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Sample records for p-type organic semiconductor

  1. Prediction and theoretical characterization of p-type organic semiconductor crystals for field-effect transistor applications.

    Science.gov (United States)

    Atahan-Evrenk, Sule; Aspuru-Guzik, Alán

    2014-01-01

    The theoretical prediction and characterization of the solid-state structure of organic semiconductors has tremendous potential for the discovery of new high performance materials. To date, the theoretical analysis mostly relied on the availability of crystal structures obtained through X-ray diffraction. However, the theoretical prediction of the crystal structures of organic semiconductor molecules remains a challenge. This review highlights some of the recent advances in the determination of structure-property relationships of the known organic semiconductor single-crystals and summarizes a few available studies on the prediction of the crystal structures of p-type organic semiconductors for transistor applications.

  2. A theoretical description of charge reorganization energies in molecular organic P-type semiconductors.

    Science.gov (United States)

    Brückner, Charlotte; Engels, Bernd

    2016-06-05

    Charge transport properties of materials composed of small organic molecules are important for numerous optoelectronic applications. A material's ability to transport charges is considerably influenced by the charge reorganization energies of the composing molecules. Hence, predictions about charge-transport properties of organic materials deserve reliable statements about these charge reorganization energies. However, using density functional theory which is mostly used for the predictions, the computed reorganization energies depend strongly on the chosen functional. To gain insight, a benchmark of various density functionals for the accurate calculation of charge reorganization energies is presented. A correlation between the charge reorganization energies and the ionization potentials is found which suggests applying IP-tuning to obtain reliable values for charge reorganization energies. According to benchmark investigations with IP-EOM-CCSD single-point calculations, the tuned functionals provide indeed more reliable charge reorganization energies. Among the standard functionals, ωB97X-D and SOGGA11X yield accurate charge reorganization energies in comparison with IP-EOM-CCSD values. © 2016 Wiley Periodicals, Inc.

  3. Screening of inorganic wide-bandgap p-type semiconductors for high performance hole transport layers in organic photovoltaic devices

    Science.gov (United States)

    Ginley, David; Zakutayev, Andriy; Garcia, Andreas; Widjonarko, Nicodemus; Ndione, Paul; Sigdel, Ajaya; Parilla, Phillip; Olson, Dana; Perkins, John; Berry, Joseph

    2011-03-01

    We will report on the development of novel inorganic hole transport layers (HTL) for organic photovoltaics (OPV). All the studied materials belong to the general class of wide-bandgap p-type oxide semiconductors. Potential candidates suitable for HTL applications include SnO, NiO, Cu2O (and related CuAlO2, CuCrO2, SrCu2O4 etc) and Co3O4 (and related ZnCo2O4, NiCo2O4, MgCo2O4 etc.). Materials have been optimized by high-throughput combinatorial approaches. The thin films were deposited by RF sputtering and pulsed laser deposition at ambient and elevated temperatures. Performance of the inorganic HTLs and that of the reference organic PEDOT:PSS HTL were compared by measuring the power conversion efficiencies and spectral responses of the P3HT/PCBM- and PCDTBT/PCBM-based OPV devices. Preliminary results indicate that Co3O4-based HTLs have performance comparable to that of our previously reported NiOs and PEDOT:PSS HTLs, leading to a power conversion efficiency of about 4 percent. The effect of composition and work function of the ternary materials on their performance in OPV devices is under investigation.

  4. Influence of chemically p-type doped active organic semiconductor on the film thickness versus performance trend in cyanine/C60 bilayer solar cells

    Science.gov (United States)

    Jenatsch, Sandra; Geiger, Thomas; Heier, Jakob; Kirsch, Christoph; Nüesch, Frank; Paracchino, Adriana; Rentsch, Daniel; Ruhstaller, Beat; C Véron, Anna; Hany, Roland

    2015-01-01

    Simple bilayer organic solar cells rely on very thin coated films that allow for effective light absorption and charge carrier transport away from the heterojunction at the same time. However, thin films are difficult to coat on rough substrates or over large areas, resulting in adverse shorting and low device fabrication yield. Chemical p-type doping of organic semiconductors can reduce Ohmic losses in thicker transport layers through increased conductivity. By using a Co(III) complex as chemical dopant, we studied doped cyanine dye/C60 bilayer solar cell performance for increasing dye film thickness. For films thicker than 50 nm, doping increased the power conversion efficiency by more than 30%. At the same time, the yield of working cells increased to 80%. We addressed the fate of the doped cyanine dye, and found no influence of doping on solar cell long term stability. PMID:27877804

  5. Influence of chemically p-type doped active organic semiconductor on the film thickness versus performance trend in cyanine/C60 bilayer solar cells.

    Science.gov (United States)

    Jenatsch, Sandra; Geiger, Thomas; Heier, Jakob; Kirsch, Christoph; Nüesch, Frank; Paracchino, Adriana; Rentsch, Daniel; Ruhstaller, Beat; C Véron, Anna; Hany, Roland

    2015-06-01

    Simple bilayer organic solar cells rely on very thin coated films that allow for effective light absorption and charge carrier transport away from the heterojunction at the same time. However, thin films are difficult to coat on rough substrates or over large areas, resulting in adverse shorting and low device fabrication yield. Chemical p-type doping of organic semiconductors can reduce Ohmic losses in thicker transport layers through increased conductivity. By using a Co(III) complex as chemical dopant, we studied doped cyanine dye/C60 bilayer solar cell performance for increasing dye film thickness. For films thicker than 50 nm, doping increased the power conversion efficiency by more than 30%. At the same time, the yield of working cells increased to 80%. We addressed the fate of the doped cyanine dye, and found no influence of doping on solar cell long term stability.

  6. Bi-Se doped with Cu, p-type semiconductor

    Science.gov (United States)

    Bhattacharya, Raghu Nath; Phok, Sovannary; Parilla, Philip Anthony

    2013-08-20

    A Bi--Se doped with Cu, p-type semiconductor, preferably used as an absorber material in a photovoltaic device. Preferably the semiconductor has at least 20 molar percent Cu. In a preferred embodiment, the semiconductor comprises at least 28 molar percent of Cu. In one embodiment, the semiconductor comprises a molar percentage of Cu and Bi whereby the molar percentage of Cu divided by the molar percentage of Bi is greater than 1.2. In a preferred embodiment, the semiconductor is manufactured as a thin film having a thickness less than 600 nm.

  7. (Ga,Fe)Sb: A p-type ferromagnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Tu, Nguyen Thanh; Anh, Le Duc; Tanaka, Masaaki [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Hai, Pham Nam [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan)

    2014-09-29

    A p-type ferromagnetic semiconductor (Ga{sub 1−x},Fe{sub x})Sb (x = 3.9%–13.7%) has been grown by low-temperature molecular beam epitaxy (MBE) on GaAs(001) substrates. Reflection high energy electron diffraction patterns during the MBE growth and X-ray diffraction spectra indicate that (Ga,Fe)Sb layers have the zinc-blende crystal structure without any other crystallographic phase of precipitates. Magnetic circular dichroism (MCD) spectroscopy characterizations indicate that (Ga,Fe)Sb has the zinc-blende band structure with spin-splitting induced by s,p-d exchange interactions. The magnetic field dependence of the MCD intensity and anomalous Hall resistance of (Ga,Fe)Sb show clear hysteresis, demonstrating the presence of ferromagnetic order. The Curie temperature (T{sub C}) increases with increasing x and reaches 140 K at x = 13.7%. The crystal structure analyses, magneto-transport, and magneto-optical properties indicate that (Ga,Fe)Sb is an intrinsic ferromagnetic semiconductor.

  8. Characterization of copper selenide thin film hole-injection layers deposited at room temperature for use with p-type organic semiconductors

    Science.gov (United States)

    Hiramatsu, Hidenori; Koizumi, Ikue; Kim, Ki-Beom; Yanagi, Hiroshi; Kamiya, Toshio; Hirano, Masahiro; Matsunami, Noriaki; Hosono, Hideo

    2008-12-01

    Copper selenide, CuxSe(x ˜2), was examined as a hole-injection layer for low-temperature organic devices. Crystalline CuxSe films grown at room temperature with atomically flat surfaces exhibited metallic conduction with a high electrical conductivity of 4.5×103 S/cm, a hole concentration of 1.4×1022 cm-3, and a mobility of 2.0 cm2/(V s). Analysis of the free carrier absorption using the Drude model estimated the effective mass of a hole as 1.0me. Photoemission spectroscopy measurements of the interfaces between CuxSe and organic hole transport layers, N ,N'-bis(naphthalen-1-yl)-N ,N'-bis(phenyl) benzidine (NPB) and copper phthalocyanine (CuPc), verified that the hole-injection barriers of these interfaces (0.4 eV for NPB and 0.3 eV for CuPc) are smaller than that of a conventional indium tin oxide (ITO) hole-injection electrode/NPB interface (0.6 eV) but are comparable to that of an ITO electrode/CuPc interface (0.3 eV). Hole-only devices using the CuxSe layer as a hole-injection anode exhibited very low threshold voltages (0.4-0.5 V) and nearly Ohmic characteristics. The NPB layer on the CuxSe layer was found to be highly doped at 1017-1019 cm-3, probably due to copper diffusion, while the CuPc layer is nearly intrinsic with a doping concentration lower than 1015 cm-3. These results indicated that a CuxSe film combined with CuPc is a promising candidate for a low-voltage hole-injection anode or a buffer layer in low-temperature devices such as organic light-emitting diodes and thin film transistors.

  9. Tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(III) as p-type dopant for organic semiconductors and its application in highly efficient solid-state dye-sensitized solar cells.

    Science.gov (United States)

    Burschka, Julian; Dualeh, Amalie; Kessler, Florian; Baranoff, Etienne; Cevey-Ha, Ngoc-Lê; Yi, Chenyi; Nazeeruddin, Mohammad K; Grätzel, Michael

    2011-11-16

    Chemical doping is an important strategy to alter the charge-transport properties of both molecular and polymeric organic semiconductors that find widespread application in organic electronic devices. We report on the use of a new class of Co(III) complexes as p-type dopants for triarylamine-based hole conductors such as spiro-MeOTAD and their application in solid-state dye-sensitized solar cells (ssDSCs). We show that the proposed compounds fulfill the requirements for this application and that the discussed strategy is promising for tuning the conductivity of spiro-MeOTAD in ssDSCs, without having to rely on the commonly employed photo-doping. By using a recently developed high molar extinction coefficient organic D-π-A sensitizer and p-doped spiro-MeOTAD as hole conductor, we achieved a record power conversion efficiency of 7.2%, measured under standard solar conditions (AM1.5G, 100 mW cm(-2)). We expect these promising new dopants to find widespread applications in organic electronics in general and photovoltaics in particular.

  10. Tris(2-(1 H -pyrazol-1-yl)pyridine)cobalt(III) as p-Type Dopant for Organic Semiconductors and Its Application in Highly Efficient Solid-State Dye-Sensitized Solar Cells

    KAUST Repository

    Burschka, Julian

    2011-11-16

    Chemical doping is an important strategy to alter the charge-transport properties of both molecular and polymeric organic semiconductors that find widespread application in organic electronic devices. We report on the use of a new class of Co(III) complexes as p-type dopants for triarylamine-based hole conductors such as spiro-MeOTAD and their application in solid-state dye-sensitized solar cells (ssDSCs). We show that the proposed compounds fulfill the requirements for this application and that the discussed strategy is promising for tuning the conductivity of spiro-MeOTAD in ssDSCs, without having to rely on the commonly employed photo-doping. By using a recently developed high molar extinction coefficient organic D-π-A sensitizer and p-doped spiro-MeOTAD as hole conductor, we achieved a record power conversion efficiency of 7.2%, measured under standard solar conditions (AM1.5G, 100 mW cm -2). We expect these promising new dopants to find widespread applications in organic electronics in general and photovoltaics in particular. © 2011 American Chemical Society.

  11. Methods for enhancing P-type doping in III-V semiconductor films

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Feng; Stringfellow, Gerald; Zhu, Junyi

    2017-08-01

    Methods of doping a semiconductor film are provided. The methods comprise epitaxially growing the III-V semiconductor film in the presence of a dopant, a surfactant capable of acting as an electron reservoir, and hydrogen, under conditions that promote the formation of a III-V semiconductor film doped with the p-type dopant. In some embodiments of the methods, the epitaxial growth of the doped III-V semiconductor film is initiated at a first hydrogen partial pressure which is increased to a second hydrogen partial pressure during the epitaxial growth process.

  12. Recent Developments in p-Type Oxide Semiconductor Materials and Devices

    KAUST Repository

    Wang, Zhenwei

    2016-02-16

    The development of transparent p-type oxide semiconductors with good performance may be a true enabler for a variety of applications where transparency, power efficiency, and greater circuit complexity are needed. Such applications include transparent electronics, displays, sensors, photovoltaics, memristors, and electrochromics. Hence, here, recent developments in materials and devices based on p-type oxide semiconductors are reviewed, including ternary Cu-bearing oxides, binary copper oxides, tin monoxide, spinel oxides, and nickel oxides. The crystal and electronic structures of these materials are discussed, along with approaches to enhance valence-band dispersion to reduce effective mass and increase mobility. Strategies to reduce interfacial defects, off-state current, and material instability are suggested. Furthermore, it is shown that promising progress has been made in the performance of various types of devices based on p-type oxides. Several innovative approaches exist to fabricate transparent complementary metal oxide semiconductor (CMOS) devices, including novel device fabrication schemes and utilization of surface chemistry effects, resulting in good inverter gains. However, despite recent developments, p-type oxides still lag in performance behind their n-type counterparts, which have entered volume production in the display market. Recent successes along with the hurdles that stand in the way of commercial success of p-type oxide semiconductors are presented.

  13. Recent Developments in p-Type Oxide Semiconductor Materials and Devices.

    Science.gov (United States)

    Wang, Zhenwei; Nayak, Pradipta K; Caraveo-Frescas, Jesus A; Alshareef, Husam N

    2016-05-01

    The development of transparent p-type oxide semiconductors with good performance may be a true enabler for a variety of applications where transparency, power efficiency, and greater circuit complexity are needed. Such applications include transparent electronics, displays, sensors, photovoltaics, memristors, and electrochromics. Hence, here, recent developments in materials and devices based on p-type oxide semiconductors are reviewed, including ternary Cu-bearing oxides, binary copper oxides, tin monoxide, spinel oxides, and nickel oxides. The crystal and electronic structures of these materials are discussed, along with approaches to enhance valence-band dispersion to reduce effective mass and increase mobility. Strategies to reduce interfacial defects, off-state current, and material instability are suggested. Furthermore, it is shown that promising progress has been made in the performance of various types of devices based on p-type oxides. Several innovative approaches exist to fabricate transparent complementary metal oxide semiconductor (CMOS) devices, including novel device fabrication schemes and utilization of surface chemistry effects, resulting in good inverter gains. However, despite recent developments, p-type oxides still lag in performance behind their n-type counterparts, which have entered volume production in the display market. Recent successes along with the hurdles that stand in the way of commercial success of p-type oxide semiconductors are presented.

  14. Nanostructured p-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes

    Directory of Open Access Journals (Sweden)

    Matteo Bonomo

    2016-05-01

    Full Text Available This review reports the properties of p-type semiconductors with nanostructured features employed as photocathodes in photoelectrochemical cells (PECs. Light absorption is crucial for the activation of the reduction processes occurring at the p-type electrode either in the pristine or in a modified/sensitized state. Beside thermodynamics, the kinetics of the electron transfer (ET process from photocathode to a redox shuttle in the oxidized form are also crucial since the flow of electrons will take place correctly if the ET rate will overcome that one of recombination and trapping events which impede the charge separation produced by the absorption of light. Depending on the nature of the chromophore, i.e., if the semiconductor itself or the chemisorbed dye-sensitizer, different energy levels will be involved in the cathodic ET process. An analysis of the general properties and requirements of electrodic materials of p-type for being efficient photoelectrocatalysts of reduction processes in dye-sensitized solar cells (DSC will be given. The working principle of p-type DSCs will be described and extended to other p-type PECs conceived and developed for the conversion of the solar radiation into chemical products of energetic/chemical interest like non fossil fuels or derivatives of carbon dioxide.

  15. Transparent p-type SnO nanowires with unprecedented hole mobility among oxide semiconductors

    KAUST Repository

    Caraveo-Frescas, J. A.

    2013-11-25

    p-type tin monoxide (SnO) nanowire field-effect transistors with stable enhancement mode behavior and record performance are demonstrated at 160 °C. The nanowire transistors exhibit the highest field-effect hole mobility (10.83 cm2 V−1 s−1) of any p-type oxide semiconductor processed at similar temperature. Compared to thin film transistors, the SnO nanowire transistors exhibit five times higher mobility and one order of magnitude lower subthreshold swing. The SnO nanowire transistors show three times lower threshold voltages (−1 V) than the best reported SnO thin film transistors and fifteen times smaller than p-type Cu 2O nanowire transistors. Gate dielectric and process temperature are critical to achieving such performance.

  16. A Density Functional Theory Study of Doped Tin Monoxide as a Transparent p-type Semiconductor

    KAUST Repository

    Bianchi Granato, Danilo

    2012-05-01

    In the pursuit of enhancing the electronic properties of transparent p-type semiconductors, this work uses density functional theory to study the effects of doping tin monoxide with nitrogen, antimony, yttrium and lanthanum. An overview of the theoretical concepts and a detailed description of the methods employed are given, including a discussion about the correction scheme for charged defects proposed by Freysoldt and others [Freysoldt 2009]. Analysis of the formation energies of the defects points out that nitrogen substitutes an oxygen atom and does not provide charge carriers. On the other hand, antimony, yttrium, and lanthanum substitute a tin atom and donate n-type carriers. Study of the band structure and density of states indicates that yttrium and lanthanum improves the hole mobility. Present results are in good agreement with available experimental works and help to improve the understanding on how to engineer transparent p-type materials with higher hole mobilities.

  17. Synthesis and Characterization of Novel Organic Semiconductors

    Institute of Scientific and Technical Information of China (English)

    Prashant; Sonar; Samarendra; P.Singh; Ananth; Dodabalapur; Alan; Sellinger

    2007-01-01

    1 Results Development of new organic semiconductors for use in low-cost,large-area applications is very important for growth of the organic electronic industry.Existing non-polymer based organic semiconductors can be roughly classified into linear,star-shaped,branched or lamellar molecules on the basis of their shape[1]. Generally hole (p-type) and electron (n-type) transporting semiconductors have been prepared from electron donating and accepting π-systems respectively[2]. These materials can be used ...

  18. New photovoltaic devices based on the sensitization of p-type semiconductors: challenges and opportunities.

    Science.gov (United States)

    Odobel, Fabrice; Le Pleux, Loïc; Pellegrin, Yann; Blart, Errol

    2010-08-17

    Because solar energy is the most abundant renewable energy resource, the clear connection between human activity and global warming has strengthened the interest in photovoltaic science. Dye-sensitized solar cells (DSSCs) provide a promising low-cost technology for harnessing this energy source. Until recently, much of the research surrounding DSSCs had been focused on the sensitization of n-type semiconductors, such as titanium dioxide (Gratzel cells). In an n-type dye-sensitized solar cell (n-DSSC), an electron is injected into the conduction band of an n-type semiconductor (n-SC) from the excited state of the sensitizer. Comparatively few studies have examined the sensitization of wide bandgap p-type semiconductors. In a p-type DSSC (p-DSSC), the photoexcited sensitizer is reductively quenched by hole injection into the valence band of a p-type semiconductor (p-SC). The study of p-DSSCs is important both to understand the factors that control the rate of hole photoinjection and to aid the rational design of efficient p-DSSCs. In theory, p-DSSCs should be able to work as efficiently as n-DSSCs. In addition, this research provides a method for preparing tandem DSSCs consisting of a TiO(2)-photosensitized anode and a photosensitized p-type SC as a cathode. Tandem DSSCs are particularly important because they represent low-cost photovoltaic devices whose photoconversion efficiencies could exceed 15%. This Account describes recent research results on p-DSSCs. Because these photoelectrochemical devices are the mirror images of conventional n-DSSCs, they share some structural similarities, but they use different materials and have different charge transfer kinetics. In this technology, nickel oxide is the predominant p-SC material used, but much higher photoconversion efficiencies could be achieved with new p-SCs materials with deeper valence band potential. Currently, iodide/triiodide is the main redox mediator of electron transport within these devices, but we expect

  19. Semiconductors for organic transistors

    Directory of Open Access Journals (Sweden)

    Antonio Facchetti

    2007-03-01

    Full Text Available Organic molecules/polymers with a π-conjugated (heteroaromatic backbone are capable of transporting charge and interact efficiently with light. Therefore, these systems can act as semiconductors in opto-electronic devices similar to inorganic materials. However, organic chemistry offers tools for tailoring materials' functional properties via modifications of the molecular/monomeric units, opening new possibilities for inexpensive device manufacturing. This article reviews the fundamental aspects behind the structural design/realization of p- (hole transporting and n-channel (electron-transporting semiconductors for organic field-effect transistors (OFETs. An introduction to OFET principles and history, as well as of the state-of-the-art organic semiconductor structure and performance of OFETs is provided.

  20. Wide bandgap n-type and p-type semiconductor porous junction devices as photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yuan-Pai; Horng, Sheng-Fu [Institute of Electronics Engineering, National Tsing Hua University, Hsinchu 300, Taiwan (China); Chao, Yu-Chiang; Meng, Hsin-Fei [Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan (China); Zan, Hsiao-Wen, E-mail: yuchiangchao@gmail.com, E-mail: meng@mail.nctu.edu.tw [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2011-10-12

    In junction absorber photovoltaics doped wide bandgap n-type and p-type semiconductors form a porous interpenetrating junction structure with a layer of low bandgap absorber at the interface. The doping concentration is high enough such that the junction depletion width is smaller than the pore size. The highly conductive neutral region then has a dentrite shape with fingers reaching the absorber to effectively collect the photo-carriers swept out by the junction electric field. With doping of 10{sup 19} cm{sup -3} corresponding to a depletion width of 25 nm, pore size of 32 nm, absorber thickness close to exciton diffusion length of 17 nm, absorber bandgap of 1.4 eV and carrier mobility over 10{sup -5} cm{sup 2} V{sup -1} s{sup -1}, numerical calculation shows the power conversion efficiency is as high as 19.4%. It rises to 23% for a triplet exciton absorber.

  1. Beyond amorphous organic semiconductors

    Science.gov (United States)

    Hanna, Jun-ichi

    2003-07-01

    Recently it has been discovered that some types of liquid crystals, which believed to be governed by ionic conduction, exhibit a very fast electronic conduction. Their charge carrier transport is characterized by high mobility over 10-2 cm2/Vs independent of electric field and temperature. Now, the liquid crystals are being recognized as a new class of organic semiconductors. In this article, a new aspect of liquid crystals as a self-organizing molecular semiconductor are reviewed, focused on their basic charge carrier transport properties and discussed in comparison with those of molecular crystals and amorphous materials. And it is concluded that the liquid crystal is promising as a quality organic semiconductor for the devices that require a high mobility.

  2. P-type thin films transistors with solution-deposited lead sulfide films as semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Carrillo-Castillo, A.; Salas-Villasenor, A.; Mejia, I. [Department of Materials Science and Engineering, The University of Texas at Dallas. 800 West Campbell Rd, Richardson, TX 75083 (United States); Aguirre-Tostado, S. [Centro de Investigacion en Materiales Avanzados, S. C. Alianza Norte 202, Parque de Investigacion e Innovacion Tecnologica, Apodaca, Nuevo Leon, C.P. 666000 (Mexico); Gnade, B.E. [Department of Materials Science and Engineering, University of Texas at Dallas. 800 West Campbell Rd, Richardson, TX 75083 (United States); Quevedo-Lopez, M.A., E-mail: mxq071000@utdallas.edu [Department of Materials Science and Engineering, University of Texas at Dallas. 800 West Campbell Rd, Richardson, TX 75083 (United States)

    2012-01-31

    In this paper we demonstrate p-type thin film transistors fabricated with lead sulfide (PbS) as semiconductor deposited by chemical bath deposition methods. Crystallinity and morphology of the resulting PbS films were characterized using X-ray diffraction, atomic force microscopy and scanning electron microscopy. Devices were fabricated using photolithographic processes in a bottom gate configuration with Au as source and drain top contacts. Field effect mobility for as-fabricated devices was {approx} 0.09 cm{sup 2} V{sup -1} s{sup -1} whereas the mobility for devices annealed at 150 Degree-Sign C/h in forming gas increased up to {approx} 0.14 cm{sup 2} V{sup -1} s{sup -1}. Besides the thermal annealing, the entire fabrications process was maintained below 100 Degree-Sign C. The electrical performance of the PbS-thin film transistors was studied before and after the 150 Degree-Sign C anneal as well as a function of the PbS active layer thicknesses. - Highlights: Black-Right-Pointing-Pointer Thin film transistors with PbS as semiconductor deposited by chemical bath deposition. Black-Right-Pointing-Pointer Photolithography-based thin film transistors with PbS films at low temperatures. Black-Right-Pointing-Pointer Electron mobility for anneal-PbS devices of {approx} 0.14 cm{sup 2} V{sup -1} s{sup -1}. Black-Right-Pointing-Pointer Highest mobility reported in thin film transistors with PbS as the semiconductor.

  3. Inorganic p-Type Semiconductors: Their Applications and Progress in Dye-Sensitized Solar Cells and Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Ming-Hsien Li

    2016-04-01

    Full Text Available Considering the increasing global demand for energy and the harmful ecological impact of conventional energy sources, it is obvious that development of clean and renewable energy is a necessity. Since the Sun is our only external energy source, harnessing its energy, which is clean, non-hazardous and infinite, satisfies the main objectives of all alternative energy strategies. With attractive features, i.e., good performance, low-cost potential, simple processibility, a wide range of applications from portable power generation to power-windows, photoelectrochemical solar cells like dye-sensitized solar cells (DSCs represent one of the promising methods for future large-scale power production directly from sunlight. While the sensitization of n-type semiconductors (n-SC has been intensively studied, the use of p-type semiconductor (p-SC, e.g., the sensitization of wide bandgap p-SC and hole transport materials with p-SC have also been attracting great attention. Recently, it has been proved that the p-type inorganic semiconductor as a charge selective material or a charge transport material in organometallic lead halide perovskite solar cells (PSCs shows a significant impact on solar cell performance. Therefore the study of p-type semiconductors is important to rationally design efficient DSCs and PSCs. In this review, recent published works on p-type DSCs and PSCs incorporated with an inorganic p-type semiconductor and our perspectives on this topic are discussed.

  4. Doping of organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Luessem, B.; Riede, M.; Leo, K. [Institut fuer Angewandte Photophysik, TU Dresden (Germany)

    2013-01-15

    The understanding and applications of organic semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small organic LED (OLED) displays; other areas of application such as OLED lighting and organic photovoltaics are on the verge of broad commercialization. Organic semiconductors are superior to inorganic ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, electrical doping of organic semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorganic semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evaporated organic layers with molecular dopants. Recently, both p- and n-type molecular dopants have been developed that lead to efficient and stable doping of organic thin films. Due to doping, the conductivity of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between organic layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and organic solar cells is highlighted in this review. Overall, controlled molecular doping can be considered as key enabling technology for many different organic device types that can lead to significant improvements in efficiencies and lifetimes. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Semiconductors for organic transistors

    OpenAIRE

    Antonio Facchetti

    2007-01-01

    Organic molecules/polymers with a π-conjugated (hetero)aromatic backbone are capable of transporting charge and interact efficiently with light. Therefore, these systems can act as semiconductors in opto-electronic devices similar to inorganic materials. However, organic chemistry offers tools for tailoring materials' functional properties via modifications of the molecular/monomeric units, opening new possibilities for inexpensive device manufacturing. This article reviews the fundamental as...

  6. Physics of Organic Semiconductors

    CERN Document Server

    Brütting, Wolfgang

    2005-01-01

    Filling the gap in the literature currently available, this book presents an overview of our knowledge of the physics behind organic semiconductor devices. Contributions from 18 international research groups cover various aspects of this field, ranging from the growth of organic layers and crystals, their electronic properties at interfaces, their photophysics and electrical transport properties to the application of these materials in such different devices as organic field-effect transistors, photovoltaic cells and organic light-emitting diodes. From the contents:. * Excitation Dynamics in O

  7. Stretchable Organic Semiconductor Devices.

    Science.gov (United States)

    Qian, Yan; Zhang, Xinwen; Xie, Linghai; Qi, Dianpeng; Chandran, Bevita K; Chen, Xiaodong; Huang, Wei

    2016-11-01

    Stretchable electronics are essential for the development of intensely packed collapsible and portable electronics, wearable electronics, epidermal and bioimplanted electronics, 3D surface compliable devices, bionics, prosthesis, and robotics. However, most stretchable devices are currently based on inorganic electronics, whose high cost of fabrication and limited processing area make it difficult to produce inexpensive, large-area devices. Therefore, organic stretchable electronics are highly attractive due to many advantages over their inorganic counterparts, such as their light weight, flexibility, low cost and large-area solution-processing, the reproducible semiconductor resources, and the easy tuning of their properties via molecular tailoring. Among them, stretchable organic semiconductor devices have become a hot and fast-growing research field, in which great advances have been made in recent years. These fantastic advances are summarized here, focusing on stretchable organic field-effect transistors, light-emitting devices, solar cells, and memory devices.

  8. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong

    2013-09-26

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  9. Optical characteristics of p-type GaAs-based semiconductors towards applications in photoemission infrared detectors

    Science.gov (United States)

    Lao, Y. F.; Perera, A. G. U.; Wang, H. L.; Zhao, J. H.; Jin, Y. J.; Zhang, D. H.

    2016-03-01

    Free-carrier effects in a p-type semiconductor including the intra-valence-band and inter-valence-band optical transitions are primarily responsible for its optical characteristics in infrared. Attention has been paid to the inter-valence-band transitions for the development of internal photoemission (IPE) mid-wave infrared (MWIR) photodetectors. The hole transition from the heavy-hole (HH) band to the spin-orbit split-off (SO) band has demonstrated potential applications for 3-5 μm detection without the need of cooling. However, the forbidden SO-HH transition at the Γ point (corresponding to a transition energy Δ0, which is the split-off gap between the HH and SO bands) creates a sharp drop around 3.6 μm in the spectral response of p-type GaAs/AlGaAs detectors. Here, we report a study on the optical characteristics of p-type GaAs-based semiconductors, including compressively strained InGaAs and GaAsSb, and a dilute magnetic semiconductor, GaMnAs. A model-independent fitting algorithm was used to derive the dielectric function from experimental reflection and transmission spectra. Results show that distinct absorption dip at Δ0 is observable in p-type InGaAs and GaAsSb, while GaMnAs displays enhanced absorption without degradation around Δ0. This implies the promise of using GaMnAs to develop MWIR IPE detectors. Discussions on the optical characteristics correlating with the valence-band structure and free-hole effects are presented.

  10. Comparison of ferromagnetism in n- and p-type magnetic semiconductor thin films of ZnCoO

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y.H., E-mail: yuhua@phys.ncku.edu.t [Department of Physics, National Cheng Kung University, No. 1, Ta-Shuei Road, Tainan 70101, Taiwan (China); Lee, J.C.; Min, J.F. [Department of Physics, National Cheng Kung University, No. 1, Ta-Shuei Road, Tainan 70101, Taiwan (China); Su, C.W. [Department of Applied Physics, National Chiayi University, Chiayi 60004, Taiwan (China)

    2011-07-15

    Both n- and p-type diluted magnetic semiconductor ZnCoO are made by magnetron co-sputtering with, respectively, dopants of Al and dual dopants of Al and N. The two sputtering targets are compound ZnCoO with 5% weight of Co and pure metal Al. Sputtering gases for n- and p-type films are pure Ar and N{sub 2}, respectively. These films are magnetic at room temperature and possess free electron- and hole-concentration of 5.34x10{sup 20} and 5.27x10{sup 13} cm{sup -3}. Only the n-type film exhibits anomalous Hall-effect signals. Magnetic properties of these two types of films are compared and discussed based on measurements of microstructure and magneto-transport properties. - Research highlights: n-type ZnCoO:Al and p-type ZnCoO:(Al, N) films are made and are both ferromagnetic at room temperature. Signal of anomalous Hall-effect (AHE) is clearly observed only for n-type film but not for p-type film. Photoluminescence (PL) spectrum shows a peak attributed to shallow acceptor band of N. Ferromagnetic exchange coupling between magnetic ions in n-type film is through spin polarized free electrons. Ferromagnetism in p-type film is not attributed to the free hole-carriers mediation but to the overlap of BMP.

  11. Organic semiconductors in a spin

    CERN Document Server

    Samuel, I

    2002-01-01

    A little palladium can go a long way in polymer-based light-emitting diodes. Inorganic semiconductors such as silicon and gallium arsenide are essential for countless applications in everyday life, ranging from PCs to CD players. However, while they offer unrivalled computational speed, inorganic semiconductors are also rigid and brittle, which means that they are less suited to applications such as displays and flexible electronics. A completely different class of materials - organic semiconductors - are being developed for these applications. Organic semiconductors have many attractive features: they are easy to make, they can emit visible light, and there is tremendous scope for tailoring their properties to specific applications by changing their chemical structure. Research groups and companies around the world have developed a wide range of organic-semiconductor devices, including transistors, light-emitting diodes (LEDs), solar cells and lasers. (U.K.)

  12. Selective growth of n-type nanoparticles on p-type semiconductors for Z-scheme photocatalysis.

    Science.gov (United States)

    Miyauchi, Masahiro; Nukui, Yuuya; Atarashi, Daiki; Sakai, Etsuo

    2013-10-09

    Nanoparticles of an n-type WO3 semiconductor were segregated on the surface of p-type CaFe2O4 particles by a heterogeneous nucleation process under controlled hydrothermal conditions. By use of this approach, WO3 nanoparticles were selectively deposited on the surface of CaFe2O4, resulting in a significant increase in the photocatalytic reaction rate of the WO3/CaFe2O4 composite for the decomposition of gaseous acetaldehyde under visible-light irradiation. The high visible-light activity of the WO3/CaFe2O4 composite was due to efficient charge recombination through the junctions that formed between the two semiconductors.

  13. Organic Semiconductors and its Applications

    Science.gov (United States)

    Kamalasanan, M. N.

    2011-10-01

    Organic semiconductors in the form of evaporated or spin coated thin films have many optoelectronic applications in the present electronic industry. They are frequently used in many type of displays, photo detectors, photoconductors for photocopiers and photovoltaic cells. But many p-conjugated molecules and polymer based devices do not provide satisfactory device performance and operational stability. Most of these problems are related to the interfaces they make with other organic materials and electrodes and the low conductivity of the organic layers. The study of organic-metal and organic—organic interfaces as well as electrical doping of organic semiconductors are very important areas of research at present. In this talk, I will be discussing some of the recent advances in this field as well as some of our own results in the area of interface modification and electrical doping of organic semiconductors.

  14. Organic semiconductors in sensor applications

    CERN Document Server

    Malliaras, George; Owens, Róisín

    2008-01-01

    Organic semiconductors offer unique characteristics such as tunability of electronic properties via chemical synthesis, compatibility with mechanically flexible substrates, low-cost manufacturing, and facile integration with chemical and biological functionalities. These characteristics have prompted the application of organic semiconductors and their devices in physical, chemical, and biological sensors. This book covers this rapidly emerging field by discussing both optical and electrical sensor concepts. Novel transducers based on organic light-emitting diodes and organic thin-film transistors, as well as systems-on-a-chip architectures are presented. Functionalization techniques to enhance specificity are outlined, and models for the sensor response are described.

  15. Exciton Transport in Organic Semiconductors

    Science.gov (United States)

    Menke, Stephen Matthew

    Photovoltaic cells based on organic semiconductors are attractive for their use as a renewable energy source owing to their abundant feedstock and compatibility with low-cost coating techniques on flexible substrates. In contrast to photovoltaic cells based traditional inorganic semiconductors, photon absorption in an organic semiconductor results in the formation of a coulombically bound electron-hole pair, or exciton. The transport of excitons, consequently, is of critical importance as excitons mediate the interaction between charge and light in organic photovoltaic cells (OPVs). In this dissertation, a strong connection between the fundamental photophysical parameters that control nanoscopic exciton energy transfer and the mesoscopic exciton transport is established. With this connection in place, strategies for enhancing the typically short length scale for exciton diffusion (L D) can be developed. Dilution of the organic semiconductor boron subphthalocyanine chloride (SubPc) is found to increase the LD for SubPc by 50%. In turn, OPVs based on dilute layers of SubPc exhibit a 30% enhancement in power conversion efficiency. The enhancement in power conversion efficiency is realized via enhancements in LD, optimized optical spacing, and directed exciton transport at an exciton permeable interface. The role of spin, energetic disorder, and thermal activation on L D are also addressed. Organic semiconductors that exhibit thermally activated delayed fluorescence and efficient intersystem and reverse intersystem crossing highlight the balance between singlet and triplet exciton energy transfer and diffusion. Temperature dependent measurements for LD provide insight into the inhomogeneously broadened exciton density of states and the thermal nature of exciton energy transfer. Additional topics include energy-cascade OPV architectures and broadband, spectrally tunable photodetectors based on organic semiconductors.

  16. Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.

    Science.gov (United States)

    Zhang, Ming-Jian; Lin, Qinxian; Yang, Xiaoyang; Mei, Zongwei; Liang, Jun; Lin, Yuan; Pan, Feng

    2016-02-10

    Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.

  17. P-type AlAs/[GaAs/AlAs] Semiconductor/Superlattice DBR Grown by MBE

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A p-type AlAs(70.2 nm)/16.5 period [GaAs(3 nm)/AlAs(0.7 nm)] semiconductor/superlatice distributed Bragg reflector (DBR) has been grown on n+-GaAs(100) substrate by V80H molecular beam epitaxy system. Experimental reflection spectrum shows that its central wavelength is 820 nm, with the peak reflectivity for 10-pair DBR of as high as 96 %, and the reflection bandwidth of as wide as 90 nm. We formed a 20×20 μm2 square mesa to measure the series resistance using wet chemical etching. From the measurement result, the series resistance of about 50 Ω is obtained at a moderate doping (3×1018 cm-3). Finally, the dependence of the resistance of the DBR on the temperature is analyzed. From the experimental result, it is found that the mechanism of the low series resistance of this kind of DBR may increase the tunneling current in the semiconductor/superlattice mirror structure, which will result in a decrease in series resistance.

  18. Spin relaxation in organic semiconductors

    Science.gov (United States)

    Bobbert, Peter

    2011-03-01

    Intriguing magnetic field effects in organic semiconductor devices have been reported: anomalous magnetoresistance in organic spin valves and large effects of small magnetic fields on the current and luminescence of organic light-emitting diodes. Influences of isotopic substitution on these effects points at the role of hyperfine coupling. We performed studies of spin relaxation in organic semiconductors based on (i) coherent spin precession of the electron spin in an effective magnetic field consisting of a random hyperfine field and an applied magnetic field and (ii) incoherent hopping of charges. These ingredients are incorporated in a stochastic Liouville equation for the dynamics of the spin density matrix of single charges as well as pairs of charges. For single charges we find a spin diffusion length that depends on the magnetic field, explaining anomalous magnetoresistance in organic spin valves. For pairs of charges we show that the magnetic field influences formation of singlet bipolarons, in the case of like charges, and singlet and triplet excitons, in the case of opposite charges. We can reproduce different line shapes of reported magnetic field effects, including recently found effects at ultra-small fields.

  19. Semiconductor systems utilizing materials that form rectifying junctions in both N and P-type doping regions, whether metallurgically or field induced, and methods of use

    Science.gov (United States)

    Welch, James D.

    2000-01-01

    Disclosed are semiconductor systems, such as integrated circuits utilizing Schotky barrier and/or diffused junction technology, which semiconductor systems incorporate material(s) that form rectifying junctions in both metallurgically and/or field induced N and P-type doping regions, and methods of their use. Disclosed are Schottky barrier based inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems and which can be operated as modulators, N and P-channel MOSFETS and CMOS formed therefrom, and (MOS) gate voltage controlled rectification direction and gate voltage controlled switching devices, and use of such material(s) to block parasitic current flow pathways. Simple demonstrative five mask fabrication procedures for inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems are also presented.

  20. Multifunctional uranyl hybrid materials: structural diversities as a function of pH, luminescence with potential nitrobenzene sensing, and photoelectric behavior as p-type semiconductors.

    Science.gov (United States)

    Song, Jian; Gao, Xue; Wang, Zhi-Nan; Li, Cheng-Ren; Xu, Qi; Bai, Feng-Ying; Shi, Zhong-Feng; Xing, Yong-Heng

    2015-09-21

    A series of uranyl-organic frameworks (UOFs), {[(UO2)2(H2TTHA)(H2O)]·4,4'-bipy·2H2O}n (1), {[(UO2)3(TTHA)(H2O)3]}n (2), and {[(UO2)5(TTHA) (HTTHA)(H2O)3]·H3O}n (3), have been obtained by the hydrothermal reaction of uranyl acetate with a flexible hexapodal ligand (1,3,5-triazine-2,4,6-triamine hexaacetic acid, H6TTHA). These compounds exhibited three distinct 3D self-assembly architectures as a function of pH by single-crystal structural analysis, although the used ligand was the same in each reaction. Surprisingly, all of the coordination modes of the H6TTHA ligand in this work are first discovered. Furthermore, the photoluminescent results showed that these compounds displayed high-sensitivity luminescent sensing functions for nitrobenzene. Additionally, the surface photovoltage spectroscopy and electric-field-induced surface photovoltage spectroscopy showed that compounds 1-3 could behave as p-type semiconductors.

  1. Organic / IV, III-V Semiconductor Hybrid Solar Cells

    Directory of Open Access Journals (Sweden)

    Pang-Leen Ong

    2010-03-01

    Full Text Available We present a review of the emerging class of hybrid solar cells based on organic-semiconductor (Group IV, III-V, nanocomposites, which states separately from dye synthesized, polymer-metal oxides and organic-inorganic (Group II-VI nanocomposite photovoltaics. The structure of such hybrid cell comprises of an organic active material (p-type deposited by coating, printing or spraying technique on the surface of bulk or nanostructured semiconductor (n-type forming a heterojunction between the two materials. Organic components include various photosensitive monomers (e.g., phtalocyanines or porphyrines, conjugated polymers, and carbon nanotubes. Mechanisms of the charge separation at the interface and their transport are discussed. Also, perspectives on the future development of such hybrid cells and comparative analysis with other classes of photovoltaics of third generation are presented.

  2. Self Organization in Compensated Semiconductors

    Science.gov (United States)

    Berezin, Alexander A.

    2004-03-01

    In partially compensated semiconductor (PCS) Fermi level is pinned to donor sub-band. Due to positional randomness and almost isoenergetic hoppings, donor-spanned electronic subsystem in PCS forms fluid-like highly mobile collective state. This makes PCS playground for pattern formation, self-organization, complexity emergence, electronic neural networks, and perhaps even for origins of life, bioevolution and consciousness. Through effects of impact and/or Auger ionization of donor sites, whole PCS may collapse (spinodal decomposition) into microblocks potentially capable of replication and protobiological activity (DNA analogue). Electronic screening effects may act in RNA fashion by introducing additional length scale(s) to system. Spontaneous quantum computing on charged/neutral sites becomes potential generator of informationally loaded microstructures akin to "Carl Sagan Effect" (hidden messages in Pi in his "Contact") or informational self-organization of "Library of Babel" of J.L. Borges. Even general relativity effects at Planck scale (R.Penrose) may affect the dynamics through (e.g.) isotopic variations of atomic mass and local density (A.A.Berezin, 1992). Thus, PCS can serve as toy model (experimental and computational) at interface of physics and life sciences.

  3. Ambipolar Organic Phototransistors with p-Type/n-Type Conjugated Polymer Bulk Heterojunction Light-Sensing Layers

    KAUST Repository

    Nam, Sungho

    2016-11-18

    Ambipolar organic phototransistors with sensing channel layers, featuring p-type and n-type conjugated polymer bulk heterojunctions, exhibit outstanding light-sensing characteristics in both p-channel and n-channel sensing operation modes.

  4. All-vapor processing of P-type tellurium-containing II-VI semiconductor and ohmic contacts thereof

    Energy Technology Data Exchange (ETDEWEB)

    McCandless, Brian E.

    2000-03-01

    An all dry method for producing solar cells is provided comprising first heat-annealing a II-VI semiconductor; enhancing the conductivity and grain size of the annealed layer; modifying the surface and depositing a tellurium layer onto the enhanced layer; and then depositing copper onto the tellurium layer so as to produce a copper tellurium compound on the layer.

  5. Progress Made in the Studies of Novel Materials for Organic Semiconductors

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Co-funded by NSFC, Ministry of Science & Technology of China (MOST) and the Chinese Academy of Sciences (CAS), researchers at the Key Laboratory of Organic Solids, ICCAS, made progress in designing and synthesis of n- and p-type organic semiconductors.

  6. A Novel Sr2CuInO3S p-type semiconductor photocatalyst for hydrogen production under visible light irradiation

    Institute of Scientific and Technical Information of China (English)

    Yushuai Jia; Jingxiu Yang; Dan Zhao; Hongxian Han; Can Li

    2014-01-01

    A novel Sr2CuInO3S oxysulfide p-type semiconductor photocatalyst has been prepared by solid state reaction method and it exhibits intriguing visible light absorption properties with a bandgap of 2.3 eV. The p-type semiconductor character of the synthesized Sr2CuInO3S was confirmed by Hall efficient measurement and Mott-Schottky plot analysis. First-principles density functional theory calculations (DFT) and electrochem-ical measurements were performed to elucidate the electronic structure and the energy band locations. It was found that the as-synthesized Sr2CuInO3S photocatalyst has appreciate conduction and valence band positions for hydrogen and oxygen evolution, respectively. Photocat-alytic hydrogen production experiments under a visible light irradiation (λ>420 nm) were carried out by loading different metal and metal-like cocatalysts on Sr2CuInO3S and Rh was found to be the best one among the tested ones.

  7. Electronic Band Structure and New Magneto-transport Properties in p-type Semiconductor Medium-infrared HgTe / CdTe Superlattice

    Science.gov (United States)

    Nafidi, Ab.; EL Abidi, A.; El Kaaouachi, A.; Nafidi, Ah.

    2005-06-01

    We report here the band structure and new magneto-transport results for HgTe (56 Å) / CdTe (30 Å) superlattice grown by molecular beam epitaxy (MBE). The angular dependence of the transverse magnetoresistance follows the two-dimensional (2D) behaviour. At low temperature, the sample exhibits p type conductivity with a concentration of 1.84×1012 cm-2 and a Hall mobility of 8200 cm2/Vs. The observed Shubnikov-de Haas effect gives a carrier density of 1.80×1012 cm-2. The superlattice heavy holes dominate the conduction in plane with an effective mass of 0.297 m0 and Fermi energy (2D) of 14 meV. In intrinsic regime, the measured gap Eg = 190 meV agree well with calculated Eg(Γ, 300 K) =178 meV. The formalism used here predicts that the system is semiconductor, for our HgTe to CdTe thickness ratio d1/d2 = 1,87, when d2 < 140 Å. In our case, d2=30 Å and Eg (Γ, 4.2 K) = 111 meV. In spite of it, the sample exhibits the features typical of a p type semiconductor and is a medium-infrared detector (7 μm< λ< 11 μm).

  8. Solution-processable low-molecular weight extended arylacetylenes: versatile p-type semiconductors for field-effect transistors and bulk heterojunction solar cells.

    Science.gov (United States)

    Silvestri, Fabio; Marrocchi, Assunta; Seri, Mirko; Kim, Choongik; Marks, Tobin J; Facchetti, Antonio; Taticchi, Aldo

    2010-05-05

    We report the synthesis and characterization of a series of five extended arylacetylenes, 9,10-bis-{[m,p-bis(hexyloxy)phenyl]ethynyl}-anthracene (A-P6t, 1), 9,10-bis-[(p-{[m,p-bis(hexyloxy) phenyl]ethynyl}phenyl)ethynyl]-anthracene (PA-P6t, 2), 4,7-bis-{[m,p-bis(hexyloxy)phenyl]ethynyl}-2,1,3-benzothiadiazole (BTZ-P6t, 5), 4,7-bis(5-{[m,p-bis(hexyloxy)phenyl]ethynyl}thien-2-yl)-2,1,3-benzothiadiazole (TBTZ-P6t, 6), and 7,7'-({[m,p-bis(hexyloxy)phenyl]ethynyl}-2,1,3-benzothiadiazol-4,4'-ethynyl)-2,5-thiophene (BTZT-P6t, 7), and two arylvinylenes, 9,10-bis-{(E)-[m,p-bis(hexyloxy)phenyl]vinyl}-anthracene (A-P6d, 3), 9,10-bis-[(E)-(p-{(E)-[m,p-bis(hexyloxy)phenyl]vinyl}phenyl)vinyl]-anthracene (PA-P6d, 4). Trends in optical absorption spectra and electrochemical redox processes are first described. Next, the thin-film microstructures and morphologies of films deposited from solution under various conditions are investigated, and organic field-effect transistors (OFETs) and bulk heterojunction photovoltaic (OPV) cells fabricated. We find that substituting acetylenic for olefinic linkers on the molecular cores significantly enhances device performance. OFET measurements reveal that all seven of the semiconductors are FET-active and, depending on the backbone architecture, the arylacetylenes exhibit good p-type mobilities (mu up to approximately 0.1 cm(2) V(-1) s(-1)) when optimum film microstructural order is achieved. OPV cells using [6,6]-phenyl C(61)-butyric acid methyl ester (PCBM) as the electron acceptor exhibit power conversion efficiencies (PCEs) up to 1.3% under a simulated AM 1.5 solar irradiation of 100 mW/cm(2). These results demonstrate that arylacetylenes are promising hole-transport materials for p-channel OFETs and promising donors for organic solar cells applications. A direct correlation between OFET arylacetylene hole mobility and OPV performance is identified and analyzed.

  9. Architectures for Improved Organic Semiconductor Devices

    Science.gov (United States)

    Beck, Jonathan H.

    Advancements in the microelectronics industry have brought increasing performance and decreasing prices to a wide range of users. Conventional silicon-based electronics have followed Moore's law to provide an ever-increasing integrated circuit transistor density, which drives processing power, solid-state memory density, and sensor technologies. As shrinking conventional integrated circuits became more challenging, researchers began exploring electronics with the potential to penetrate new applications with a low price of entry: "Electronics everywhere." The new generation of electronics is thin, light, flexible, and inexpensive. Organic electronics are part of the new generation of thin-film electronics, relying on the synthetic flexibility of carbon molecules to create organic semiconductors, absorbers, and emitters which perform useful tasks. Organic electronics can be fabricated with low energy input on a variety of novel substrates, including inexpensive plastic sheets. The potential ease of synthesis and fabrication of organic-based devices means that organic electronics can be made at very low cost. Successfully demonstrated organic semiconductor devices include photovoltaics, photodetectors, transistors, and light emitting diodes. Several challenges that face organic semiconductor devices are low performance relative to conventional devices, long-term device stability, and development of new organic-compatible processes and materials. While the absorption and emission performance of organic materials in photovoltaics and light emitting diodes is extraordinarily high for thin films, the charge conduction mobilities are generally low. Building highly efficient devices with low-mobility materials is one challenge. Many organic semiconductor films are unstable during fabrication, storage, and operation due to reactions with water, oxygen and hydroxide. A final challenge facing organic electronics is the need for new processes and materials for electrodes

  10. Rhodium-doped barium titanate perovskite as a stable p-type semiconductor photocatalyst for hydrogen evolution under visible light.

    Science.gov (United States)

    Maeda, Kazuhiko

    2014-02-12

    Rhodium-doped barium titanate (BaTiO3:Rh) powder was prepared by the polymerized complex (PC) method, and the photocatalytic activity for H2 evolution from water was examined. BaTiO3 is a wide-gap n-type semiconductor having a band gap of 3.0 eV. Doping Rh species into the lattice of BaTiO3 resulted in the formation of new absorption bands in visible light region. Upon visible light (λ > 420 nm), BaTiO3:Rh modified with nanoparticulate Pt as a water reduction promoter was capable of producing H2 from water containing an electron donor such as methanol and iodide. The best material prepared by the PC method exhibited higher activity than that made by a conventional solid-state reaction method. Visible-light-driven Z-scheme water splitting was also accomplished using Pt/BaTiO3:Rh as a building block for H2 evolution in combination with PtOx-loaded WO3 as an O2 evolution photocatalyst in the presence of an IO3(-)/I(-) shuttle redox mediator. Photoelectrochemical analysis indicated that a porous BaTiO3:Rh electrode exhibited cathodic photoresponse due to water reduction in a neutral aqueous Na2SO4 solution upon visible light.

  11. Organic semiconductors for organic field-effect transistors

    Directory of Open Access Journals (Sweden)

    Yoshiro Yamashita

    2009-01-01

    Full Text Available The advantages of organic field-effect transistors (OFETs, such as low cost, flexibility and large-area fabrication, have recently attracted much attention due to their electronic applications. Practical transistors require high mobility, large on/off ratio, low threshold voltage and high stability. Development of new organic semiconductors is key to achieving these parameters. Recently, organic semiconductors have been synthesized showing comparable mobilities to amorphous-silicon-based FETs. These materials make OFETs more attractive and their applications have been attempted. New organic semiconductors resulting in high-performance FET devices are described here and the relationship between transistor characteristics and chemical structure is discussed.

  12. p-Type semiconducting nickel oxide as an efficiency-enhancing anodal interfacial layer in bulk heterojunction solar cells

    Science.gov (United States)

    Irwin, Michael D; Buchholz, Donald B; Marks, Tobin J; Chang, Robert P. H.

    2014-11-25

    The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode, a p-type semiconductor layer formed on the anode, and an active organic layer formed on the p-type semiconductor layer, where the active organic layer has an electron-donating organic material and an electron-accepting organic material.

  13. p-Type Transparent Conducting Oxide/n-Type Semiconductor Heterojunctions for Efficient and Stable Solar Water Oxidation.

    Science.gov (United States)

    Chen, Le; Yang, Jinhui; Klaus, Shannon; Lee, Lyman J; Woods-Robinson, Rachel; Ma, Jie; Lum, Yanwei; Cooper, Jason K; Toma, Francesca M; Wang, Lin-Wang; Sharp, Ian D; Bell, Alexis T; Ager, Joel W

    2015-08-05

    Achieving stable operation of photoanodes used as components of solar water splitting devices is critical to realizing the promise of this renewable energy technology. It is shown that p-type transparent conducting oxides (p-TCOs) can function both as a selective hole contact and corrosion protection layer for photoanodes used in light-driven water oxidation. Using NiCo2O4 as the p-TCO and n-type Si as a prototypical light absorber, a rectifying heterojunction capable of light driven water oxidation was created. By placing the charge separating junction in the Si using a np(+) structure and by incorporating a highly active heterogeneous Ni-Fe oxygen evolution catalyst, efficient light-driven water oxidation can be achieved. In this structure, oxygen evolution under AM1.5G illumination occurs at 0.95 V vs RHE, and the current density at the reversible potential for water oxidation (1.23 V vs RHE) is >25 mA cm(-2). Stable operation was confirmed by observing a constant current density over 72 h and by sensitive measurements of corrosion products in the electrolyte. In situ Raman spectroscopy was employed to investigate structural transformation of NiCo2O4 during electrochemical oxidation. The interface between the light absorber and p-TCO is crucial to produce selective hole conduction to the surface under illumination. For example, annealing to produce more crystalline NiCo2O4 produces only small changes in its hole conductivity, while a thicker SiOx layer is formed at the n-Si/p-NiCo2O4 interface, greatly reducing the PEC performance. The generality of the p-TCO protection approach is demonstrated by multihour, stable, water oxidation with n-InP/p-NiCo2O4 heterojunction photoanodes.

  14. Band structure engineering in organic semiconductors

    Science.gov (United States)

    Schwarze, Martin; Tress, Wolfgang; Beyer, Beatrice; Gao, Feng; Scholz, Reinhard; Poelking, Carl; Ortstein, Katrin; Günther, Alrun A.; Kasemann, Daniel; Andrienko, Denis; Leo, Karl

    2016-06-01

    A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.

  15. Micro- and nanocrystals of organic semiconductors.

    Science.gov (United States)

    Li, Rongjin; Hu, Wenping; Liu, Yunqi; Zhu, Daoben

    2010-04-20

    Organic semiconductors have attracted wide attention in recent decades, resulting in the rapid development of organic electronics. For example, the solution processibility of organic semiconductors allows researchers to use unconventional deposition methods (such as inkjet printing and stamping) to fabricate large area devices at low cost. The mechanical properties of organic semiconductors also allow for flexible electronics. However, the most distinguishing feature of organic semiconductors is their chemical versatility, which permits the incorporation of functionalities through molecular design. However, key scientific challenges remain before organic electronics technology can advance further, including both the materials' low charge carrier mobility and researchers' limited knowledge of structure-property relationships in organic semiconductors. We expect that high-quality organic single crystals could overcome these challenges: their purity and long-range ordered molecular packing ensure high device performance and facilitate the study of structure-property relationships. Micro- and nanoscale organic crystals could offer practical advantages compared with their larger counterparts. First, growing small crystals conserves materials and saves time. Second, devices based on the smaller crystals could maintain the functional advantages of larger organic single crystals but would avoid the growth of large crystals, leading to the more efficient characterization of organic semiconductors. Third, the effective use of small crystals could allow researchers to integrate these materials into micro- and nanoelectronic devices using a "bottom-up" approach. Finally, unique properties of crystals at micro- and nanometer scale lead to new applications, such as flexible electronics. In this Account, we focus on organic micro- and nanocrystals, including their design, the controllable growth of crystals, and structure-property studies. We have also fabricated devices and

  16. Method of doping organic semiconductors

    Science.gov (United States)

    Kloc, Christian Leo [Constance, DE; Ramirez, Arthur Penn [Summit, NJ; So, Woo-Young [New Providence, NJ

    2012-02-28

    A method includes the steps of forming a contiguous semiconducting region and heating the region. The semiconducting region includes polyaromatic molecules. The heating raises the semiconducting region to a temperature above room temperature. The heating is performed in the presence of a dopant gas and the absence of light to form a doped organic semiconducting region.

  17. Spectroscopy of organic semiconductors from first principles

    Science.gov (United States)

    Sharifzadeh, Sahar; Biller, Ariel; Kronik, Leeor; Neaton, Jeffery

    2011-03-01

    Advances in organic optoelectronic materials rely on an accurate understanding their spectroscopy, motivating the development of predictive theoretical methods that accurately describe the excited states of organic semiconductors. In this work, we use density functional theory and many-body perturbation theory (GW/BSE) to compute the electronic and optical properties of two well-studied organic semiconductors, pentacene and PTCDA. We carefully compare our calculations of the bulk density of states with available photoemission spectra, accounting for the role of finite temperature and surface effects in experiment, and examining the influence of our main approximations -- e.g. the GW starting point and the application of the generalized plasmon-pole model -- on the predicted electronic structure. Moreover, our predictions for the nature of the exciton and its binding energy are discussed and compared against optical absorption data. We acknowledge DOE, NSF, and BASF for financial support and NERSC for computational resources.

  18. Heteroarenes as high performance organic semiconductors.

    Science.gov (United States)

    Jiang, Wei; Li, Yan; Wang, Zhaohui

    2013-07-21

    The design, synthesis, and characterization of new organic semiconductors (OSCs) are important aspects for the development of next-generation optoelectronic devices. Structurally, organic semiconductors based on π-conjugated molecules can be easily modified via rational synthesis to tune multi-level self-assembled structures and discover novel chemical, optical, and electronic properties. Heteroarenes, which contain chalcogens and nitrogens in fused aromatic rings, are being developed as promising semiconducting materials for applications in a variety of electronic devices due to their outstanding optoelectronic properties. We highlight recent approaches toward realizing high performance p-channel field effect transistors based on linear heteroacenes and heteroatom annulated polycyclic aromatics (PAHs) as key functional components. These comprehensive, but carefully orchestrated approaches simultaneously address (i) practical synthesis, (ii) tunable self-assembled packing arrangement as well as (iii) high electronic performance.

  19. Conductive-AFM Patterning of Organic Semiconductors.

    Science.gov (United States)

    Brown, Benjamin P; Picco, Loren; Miles, Mervyn J; Faul, Charl F J

    2015-10-01

    Using a conductive atomic force microscope (c-AFM) redox-writing technique, it is shown that it is possible to locally, and reversibly, pattern conducting, and nonconducting features on the surface of a low molecular weight aniline-based organic (semi)-conductor thin film using a commercial c-AFM. It is shown that application of a voltage between the tip and sample causes localized redox reactions at the surface without damage.

  20. Current transport mechanism at metal-semiconductor nanoscale interfaces based on ultrahigh density arrays of p-type NiO nano-pillars.

    Science.gov (United States)

    Nandy, Suman; Gonçalves, Gonçalo; Pinto, Joana Vaz; Busani, Tito; Figueiredo, Vitor; Pereira, Luís; Paiva Martins, Rodrigo Ferrão; Fortunato, Elvira

    2013-12-07

    The present work focuses on a qualitative analysis of localised I-V characteristics based on the nanostructure morphology of highly dense arrays of p-type NiO nano-pillars (NiO-NPs). Vertically aligned NiO-NPs have been grown on different substrates by using a glancing angle deposition (GLAD) technique. The preferred orientation of as grown NiO-NPs was controlled by the deposition pressure. The NiO-NPs displayed a polar surface with a microscopic dipole moment along the (111) plane (Tasker's type III). Consequently, the crystal plane dependent surface electron accumulation layer and the lattice disorder at the grain boundary interface showed a non-uniform current distribution throughout the sample surface, demonstrated by a conducting AFM technique (c-AFM). The variation in I-V for different points in a single current distribution grain (CD-grain) has been attributed to the variation of Schottky barrier height (SBH) at the metal-semiconductor (M-S) interface. Furthermore, we observed that the strain produced during the NiO-NPs growth can modulate the SBH. Inbound strain acts as an external field to influence the local electric field at the M-S interface causing a variation in SBH with the NPs orientation. This paper shows that vertical arrays of NiO-NPs are potential candidates for nanoscale devices because they have a great impact on the local current transport mechanism due to its nanostructure morphology.

  1. Impact of strain on gate-induced floating body effect for partially depleted silicon-on-insulator p-type metal–oxide–semiconductor-field-effect-transistors

    Energy Technology Data Exchange (ETDEWEB)

    Lo, Wen-Hung [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Chang, Ting-Chang, E-mail: tcchang@mail.phys.nsysu.edu.tw [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Dai, Chih-Hao [Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Chung, Wan-Lin [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Chen, Ching-En; Ho, Szu-Han [Department of Electronics Engineering, National Chiao Tung University, Hsinchu, Taiwan, ROC (China); Tsai, Jyun-Yu [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Chen, Hua-Mao [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan, ROC (China); Liu, Guan-Ru [Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC (China); Cheng, Osbert; Huang, Cheng-Tung [Device Department, United Microelectronics Corporation, Tainan Science Park, Taiwan, ROC (China)

    2013-01-01

    This work investigates impact of mechanical strain on gate-induced-floating-body-effect (GIFBE) for partially depleted silicon-on-insulator p-type metal–oxide–semiconductor field effect transistors (PD SOI p-MOSFETs). First part, the original mechanism of GIFBE on PD SOI p-MOSFETs is studied. The experimental results indicate that GIFBE causes a reduction in oxide electric field (E{sub ox}), resulting in an underestimate of negative-bias temperature instability (NBTI) degradation. This can be attributed to the electrons tunneling from the process-induced partial n{sup +} poly gate and anode electron injection (AEI) model, rather than the electron valence band tunneling (EVB) widely accepted as the mechanism for n-MOSFETs. And then, the second part shows that the strained FB device has less NBTI degradation than the unstrained devices. This behavior can be attributed to the fact that more electron accumulation was induced by strain-induced band gap narrowing, reducing NBTI significantly. - Highlights: ► This work investigates the impact of mechanical strain on GIFBE for PD SOI p-MOSFETs. ► FB device shows an insignificant NBTI due to GIFBE. ► GIFBE results from the partial n{sup +} poly gate and anode electron injection model. ► The strained FB device has less NBTI degradation than unstrained devices. ► We verify the band gap narrowing causes less NBTI on strained FB device.

  2. Impact of mechanical stress on gate tunneling currents of germanium and silicon p-type metal-oxide-semiconductor field-effect transistors and metal gate work function

    Science.gov (United States)

    Choi, Youn Sung; Numata, Toshinori; Nishida, Toshikazu; Harris, Rusty; Thompson, Scott E.

    2008-03-01

    Uniaxial four-point wafer bending stress-altered gate tunneling currents are measured for germanium (Ge)/silicon (Si) channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with HfO2/SiO2 gate dielectrics and TiN/P+ poly Si electrodes. Carrier separation is used to measure electron and hole currents. The strain-altered hole tunneling current from the p-type inversion layer of Ge is measured to be ˜4 times larger than that for the Si channel MOSFET, since the larger strain-induced valence band-edge splitting in Ge results in more hole repopulation into a subband with a smaller out-of-plane effective mass and a lower tunneling barrier height. The strain-altered electron tunneling current from the metal gate is measured and shown to change due to strain altering the metal work function as quantified by flatband voltage shift measurements of Si MOS capacitors with TaN electrodes.

  3. Low level optical absorption measurements on organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Stella, M.; Rojas, F.; Escarre, J.; Asensi, J.M.; Bertomeu, J.; Andreu, J. [Dept. de Fisica Aplicada i Optica, Universitat de Barcelona. Av. Diagonal 647, 08028 Barcelona (Spain); Voz, C.; Puigdollers, J.; Fonrodona, M. [Micro and Nano Technology Group (MNT), Dept. d' Enginyeria Electronica, Universitat Politecnica de Catalunya, C/Jordi Girona 1-3, Campus Nord - Modul C4, 08034 Barcelona (Spain)

    2006-06-15

    The optical absorption of n-type (C{sub 60} and PTCDA) and p-type (CuPc and pentacene) organic semiconductors is investigated by optical transmission and photothermal deflection spectroscopy. The usual absorption bands related to HOMO-LUMO transitions are observed in the high absorption region of transmission spectra. Photothermal deflection spectroscopy also evidences exponential absorption shoulders with characteristic energies 47meV for CuPc, 38meV for pentacene, 50 meV for PTCDA and 87meV for C{sub 60}. In addition, broad bands in the low absorption level are observed for C{sub 60} and PTCDA. These bands have been attributed to contamination due to air exposure. On the other hand, in CuPc a clear absorption peak at 1.12eV is observed with smaller features at 1.04eV, 1.20eV and 1.33eV. These peaks are attributed to transitions between the Pc levels of CuPc ions. Finally, the optical absorption expected in blends of organic semiconductors is estimated by an effective media approximation. (author)

  4. Halopentacenes: Promising Candidates for Organic Semiconductors

    Institute of Scientific and Technical Information of China (English)

    DU Gong-He; REN Zhao-Yu; GUO Ping; ZHENG Ji-Ming

    2009-01-01

    We introduce polar substituents such as F, Cl, Br into pentacene to enhance the dissolubility in common organic solvents while retaining the high charge-carrier mobilities of pentacene. Geometric structures, dipole moments,frontier molecule orbits, ionization potentials and electron affinities, as well as reorganization energies of those molecules, and of pentacene for comparison, are successively calculated by density functional theory. The results indicate that halopentacenes have rather small reorganization energies (< 0.2 eV), and when the substituents are in position 2 or positions 2 and 9, they are polarity molecules. Thus we conjecture that they can easily be dissolved in common organic solvents, and are promising candidates for organic semiconductors.

  5. Tuning the crystal polymorphs of organic semiconductor towards high performance organic transistors (Conference Presentation)

    Science.gov (United States)

    Zhen, Yonggang; He, Ping; Yi, Yuanping; Hu, Wenping

    2016-11-01

    Generally, the differences in crystal polymorph exhibit different narrow band structures, electron-phonon coupling, optoelectronic characteristics and charge transport properties, thus leading to different device performances of organic semiconductors for application in organic field-effect transistors (OFETs). Nowadays it still remains a big challenge to control organic crystal polymorph because the slight non-directional intermolecular interactions lead to the very small differences instructure and energy of cystal phases with several alternative packing arrangements. Therefore, the control of the crystal polymorphism towards high device performance has become a crucial issue in the field of organic semiconductors. Thienoacenes have been intensively investigated as very promising organic semiconductors with high stability and superior mobility for OFETs in the last decade. However, scare studies focused on the crystal polymorph of thienoacenes. Herein, we report the controllable growth of different crystal phases of dihexyl-substituted dibenzo[d,d']thieno[3,2-b;4,5-b']dithiophene (C6-DBTDT), which was synthesized in a new, facile and efficient method. Furthermore, OFETs based on microribbon-shaped β phase crystals showed the hole mobility up to 18.9 cm2 V-1 s-1, which is one of the highest value for p-type organic semiconductors measured under ambient conditions, while platelet-shaped α phase crystals displayed the lower hole mobility of 8.5 cm2 V-1 s-1. We clearly demonstrated that the selective growth of different crystal polymorph for C6-DBTDT can be achieved by using different substrate and solvents. The simple drop-cast fabrication with controllable crystal phase and air operation stability would open the possibility of thienoacene derivatives in the construction of micro- and nanoelectronics.

  6. Organic semiconductors as candidates for advanced optoelectronic devices:

    OpenAIRE

    Bratina, Gvido; Hudej, Robert

    2001-01-01

    Organic semiconductors are gaining an increasing attention due to their promise of novel optoelectronic devices. The main attraction of these materials stems from their potential integration with flexible materials, which would result in ultrathin flexible multicolor displays. Basic electronic properties of typical representatives of organic semiconductors are reviewed. The operation of a light-emitting device based on organic semiconductors is fundamentally different from its inorganic count...

  7. Blue emitting organic semiconductors under high pressure

    DEFF Research Database (Denmark)

    Knaapila, Matti; Guha, Suchismita

    2016-01-01

    This review describes essential optical and emerging structural experiments that use high GPa range hydrostatic pressure to probe physical phenomena in blue-emitting organic semiconductors including π-conjugated polyfluorene and related compounds. The work emphasizes molecular structure...... and intermolecular self-organization that typically determine transport and optical emission in π-conjugated oligomers and polymers. In this context, hydrostatic pressure through diamond anvil cells has proven to be an elegant tool to control structure and interactions without chemical intervention. This has been...... and intermolecular interactions on optical excitations, electron–phonon interaction, and changes in backbone conformations. This picture is connected to the optical high pressure studies of other π-conjugated systems and emerging x-ray scattering experiments from polyfluorenes which provides a structure-property map...

  8. Semiconductor gel in shark sense organs?

    Science.gov (United States)

    Fields, R Douglas; Fields, Kyle D; Fields, Melanie C

    2007-10-22

    Sharks can sense bioelectric fields of prey and other animals in seawater using an extraordinary system of sense organs (ampullae of Lorenzini) [R.D. Fields, The shark's electric sense. Sci. Am. 297 (2007) 74-81]. A recent study reported that these sense organs also enable sharks to locate prey-rich thermal fronts using a novel mode of temperature reception without ion channels. The study reported that gel extracted from the organs operates as a thermoelectric semiconductor, generating electricity when it is heated or cooled [B.R. Brown, Neurophysiology: sensing temperature without ion channels, Nature 421 (2003) 495]. Here we report biophysical studies that call into question this mechanism of sensory transduction. Our experiments indicate that the material exhibits no unusual thermoelectric or electromechanical properties, and that the thermoelectric response is an artifact caused by temperature effects on the measurement electrodes. No response is seen when non-metallic electrodes (carbon or salt bridges) are used, and ordinary seawater produces the same effect as shark organ gel when silver wire electrodes are used. These data are consistent with the voltages arising from electrochemical electrode potentials rather generated intrinsically within the sample. This new evidence, together with the anatomy of the organs and behavioral studies in the literature, best support the conclusion that the biological function of these sense organs is to detect electric fields.

  9. Charge transport in single crystal organic semiconductors

    Science.gov (United States)

    Xie, Wei

    Organic electronics have engendered substantial interest in printable, flexible and large-area applications thanks to their low fabrication cost per unit area, chemical versatility and solution processability. Nevertheless, fundamental understanding of device physics and charge transport in organic semiconductors lag somewhat behind, partially due to ubiquitous defects and impurities in technologically useful organic thin films, formed either by vacuum deposition or solution process. In this context, single-crystalline organic semiconductors, or organic single crystals, have therefore provided the ideal system for transport studies. Organic single crystals are characterized by their high chemical purity and outstanding structural perfection, leading to significantly improved electrical properties compared with their thin-film counterparts. Importantly, the surfaces of the crystals are molecularly flat, an ideal condition for building field-effect transistors (FETs). Progress in organic single crystal FETs (SC-FETs) is tremendous during the past decade. Large mobilities ~ 1 - 10 cm2V-1s-1 have been achieved in several crystals, allowing a wide range of electrical, optical, mechanical, structural, and theoretical studies. Several challenges still remain, however, which are the motivation of this thesis. The first challenge is to delineate the crystal structure/electrical property relationship for development of high-performance organic semiconductors. This thesis demonstrates a full spectrum of studies spanning from chemical synthesis, single crystal structure determination, quantum-chemical calculation, SC-OFET fabrication, electrical measurement, photoelectron spectroscopy characterization and extensive device optimization in a series of new rubrene derivatives, motivated by the fact that rubrene is a benchmark semiconductor with record hole mobility ~ 20 cm2V-1s-1. With successful preservation of beneficial pi-stacking structures, these rubrene derivatives form

  10. Charged particle detection in organic semiconductors

    CERN Document Server

    Beckerle, P

    2000-01-01

    Polyacetylene is an organic semiconductor in which charges can be set free by a traversing charged particle, transported by an electric field to read-out electrodes and, subsequently, amplified and recorded in a way similar to what happens in a silicon-drift detector. In an experimental investigation of the features of this charge transport in thin foils we find drift velocities of the order of 40 cm/s. Stretching of the foils by a factor of three to four increases the drift velocity by a factor of ten and introduces a strong directionality of the charge transport. The detection efficiency of 5 MeV alpha particles in a few micron thin stretched foil is around 70%.

  11. Benzodicarbomethoxytetrathiafulvalene derivatives as soluble organic semiconductors.

    Science.gov (United States)

    Otón, Francisco; Pfattner, Raphael; Oxtoby, Neil S; Mas-Torrent, Marta; Wurst, Klaus; Fontrodona, Xavier; Olivier, Yoann; Cornil, Jérôme; Veciana, Jaume; Rovira, Concepció

    2011-01-07

    A series of new tetrathiafulvalene (TTF) derivatives bearing dimethoxycarbonyl and phenyl or phthalimidyl groups fused to the TTF core (6 and 15-18) has been synthesized as potential soluble semiconductor materials for organic field-effect transistors (OFETs). The electron-withdrawing substituents lower the energy of the HOMO and LUMO levels and increase the solubility and stability of the semiconducting material. Crystal structures of all new TTF derivatives are also described, and theoretical DFT calculations were carried out to study the potential of the crystals to be used in OFET. In the experimental study, the best performing device exhibited a hole mobility up to 7.5 × 10(-3) cm(2) V(-1) s(-1)).

  12. PHOTOOXIDATION OF ORGANIC WASTES USING SEMICONDUCTOR NANOCLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Wilcoxon, Jess P.

    2000-12-31

    It would be a major boon to have a visible light absorbing semiconductor catalytic material available, which is also photostable and non-toxic. Such a photocatalyst would make it possible to exploit sunlight as the sole energy source required for detoxification. To this end we have employed our expertise in nanocluster synthesis and processing to make and purify nanoparticles of MoS2. The band-gap and absorbance edges of these nanoparticles can be adjusted by particle size based upon the quantum confinement of the electron-hole pair. In a recent paper we demonstrated the use of these new photocatalysts to destroy phenol, and demonstrated a strong effect of size or band-gap on the rate of photo-oxidation.5 In this research we investigate the photooxidation kinetics and products formed for a standard material, Degussa P-25 TiO2, as compared to nanosize TiO2, SnO2, and MoS2. We examined the light intensity dependence for nanosize SnO2 compared to TiO2 (Degussa), and the effect o f size on photooxidation kinetics for both SnO2 and MoS2. We studied photooxidation in aqueous systems and, for the first time, a system consisting almost entirely of a polar organic, acetonitrile. Our primary objective was to develop an entirely new class of material: nanosize semiconductors with visible bandgaps and to engineer these material's properties to allow us to photooxidize toxic organic compounds in water on a reasonable time scale ({approx}8 hrs). A second objective was to study how certain material properties such as size, surface treatment, and material type affect the efficiency of the photocatalytic process as well as optimizing these features.

  13. Charge transport in nanoscale lateral and vertical organic semiconductor devices

    NARCIS (Netherlands)

    Xu, Bojian

    2017-01-01

    Organic semiconductors have been drawing more and more attention due to their huge potential for low-cost, flexible, printable electronics and spintronics. In this thesis research, we have investigated charge transport in two organic semiconductors, DXP and P3HT, in different device configurations.

  14. Charge transport in amorphous organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lukyanov, Alexander

    2011-03-15

    Organic semiconductors with the unique combination of electronic and mechanical properties may offer cost-effective ways of realizing many electronic applications, e. g. large-area flexible displays, printed integrated circuits and plastic solar cells. In order to facilitate the rational compound design of organic semiconductors, it is essential to understand relevant physical properties e. g. charge transport. This, however, is not straightforward, since physical models operating on different time and length scales need to be combined. First, the material morphology has to be known at an atomistic scale. For this atomistic molecular dynamics simulations can be employed, provided that an atomistic force field is available. Otherwise it has to be developed based on the existing force fields and first principle calculations. However, atomistic simulations are typically limited to the nanometer length- and nanosecond time-scales. To overcome these limitations, systematic coarse-graining techniques can be used. In the first part of this thesis, it is demonstrated how a force field can be parameterized for a typical organic molecule. Then different coarse-graining approaches are introduced together with the analysis of their advantages and problems. When atomistic morphology is available, charge transport can be studied by combining the high-temperature Marcus theory with kinetic Monte Carlo simulations. The approach is applied to the hole transport in amorphous films of tris(8- hydroxyquinoline)aluminium (Alq{sub 3}). First the influence of the force field parameters and the corresponding morphological changes on charge transport is studied. It is shown that the energetic disorder plays an important role for amorphous Alq{sub 3}, defining charge carrier dynamics. Its spatial correlations govern the Poole-Frenkel behavior of the charge carrier mobility. It is found that hole transport is dispersive for system sizes accessible to simulations, meaning that calculated

  15. Tuning Bandgap of p-Type Cu2Zn(Sn, Ge)(S, Se)4 Semiconductor Thin Films via Aqueous Polymer-Assisted Deposition.

    Science.gov (United States)

    Yi, Qinghua; Wu, Jiang; Zhao, Jie; Wang, Hao; Hu, Jiapeng; Dai, Xiao; Zou, Guifu

    2017-01-18

    Bandgap engineering of kesterite Cu2Zn(Sn, Ge)(S, Se)4 with well-controlled stoichiometric composition plays a critical role in sustainable inorganic photovoltaics. Herein, a cost-effective and reproducible aqueous solution-based polymer-assisted deposition approach is developed to grow p-type Cu2Zn(Sn, Ge)(S, Se)4 thin films with tunable bandgap. The bandgap of Cu2Zn(Sn, Ge)(S, Se)4 thin films can be tuned within the range 1.05-1.95 eV using the aqueous polymer-assisted deposition by accurately controlling the elemental compositions. One of the as-grown Cu2Zn(Sn, Ge)(S, Se)4 thin films exhibits a hall coefficient of +137 cm(3)/C. The resistivity, concentration and carrier mobility of the Cu2ZnSn(S, Se)4 thin film are 3.17 ohm·cm, 4.5 × 10(16) cm(-3), and 43 cm(2)/(V·S) at room temperature, respectively. Moreover, the Cu2ZnSn(S, Se)4 thin film when used as an active layer in a solar cell leads to a power conversion efficiency of 3.55%. The facile growth of Cu2Zn(Sn, Ge)(S, Se)4 thin films in an aqueous system, instead of organic solvents, provides great promise as an environmental-friendly platform to fabricate a variety of single/multi metal chalcogenides for the thin film industry and solution-processed photovoltaic devices.

  16. Charge-transport simulations in organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    May, Falk

    2012-07-06

    In this thesis we have extended the methods for microscopic charge-transport simulations for organic semiconductors, where weak intermolecular interactions lead to spatially localized charge carriers, and the charge transport occurs as an activated hopping process between diabatic states. In addition to weak electronic couplings between these states, different electrostatic environments in the organic material lead to a broadening of the density of states for the charge energies which limits carrier mobilities. The contributions to the method development include (i) the derivation of a bimolecular charge-transfer rate, (ii) the efficient evaluation of intermolecular (outer-sphere) reorganization energies, (iii) the investigation of effects of conformational disorder on intramolecular reorganization energies or internal site energies and (iv) the inclusion of self-consistent polarization interactions for calculation of charge energies. These methods were applied to study charge transport in amorphous phases of small molecules used in the emission layer of organic light emitting diodes (OLED). When bulky substituents are attached to an aromatic core in order to adjust energy levels or prevent crystallization, a small amount of delocalization of the frontier orbital to the substituents can increase electronic couplings between neighboring molecules. This leads to improved charge-transfer rates and, hence, larger charge-mobility. We therefore suggest using the mesomeric effect (as opposed to the inductive effect) when attaching substituents to aromatic cores, which is necessary for example in deep blue OLEDs, where the energy levels of a host molecule have to be adjusted to those of the emitter. Furthermore, the energy landscape for charges in an amorphous phase cannot be predicted by mesoscopic models because they approximate the realistic morphology by a lattice and represent molecular charge distributions in a multipole expansion. The microscopic approach shows that

  17. New Organic Semiconductor Materials Applied in Organic Photovoltaic and Optical Devices

    National Research Council Canada - National Science Library

    Andre F. S. Guedes; Vilmar P. Guedes; Simone Tartari; Mônica L. Souza; Idaulo J. Cunha

    2015-01-01

    The development of flexible organic photovoltaic solar cells, using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry...

  18. Organic modification of metal / semiconductor Schottky contacts

    Energy Technology Data Exchange (ETDEWEB)

    Mendez Pinzon, H.A.

    2006-07-10

    In the present work a Metal / organic / inorganic semiconductor hybrid heterostructure (Ag / DiMe-PTCDI / GaAs) was built under UHV conditions and characterised in situ. The aim was to investigate the influence of the organic layer in the surface properties of GaAs(100) and in the electrical response of organic-modified Ag / GaAs Schottky diodes. The device was tested by combining surface-sensitive techniques (Photoemission spectroscopy and NEXAFS) with electrical measurements (current-voltage, capacitance-voltage, impedance and charge transient spectroscopies). Core level examination by PES confirms removal of native oxide layers on sulphur passivated (S-GaAs) and hydrogen plasma treated GaAs(100) (H+GaAs) surfaces. Additional deposition of ultrathin layers of DiMe-PTCDI may lead to a reduction of the surface defects density and thereby to an improvement of the electronic properties of GaAs. The energy level alignment through the heterostructure was deduced by combining UPS and I-V measurements. This allows fitting of the I-V characteristics with electron as majority carriers injected over a barrier by thermionic emission as a primary event. For thin organic layers (below 8 nm thickness) several techniques (UPS, I-V, C-V, QTS and AFM) show non homogeneous layer growth, leading to formation of voids. The coverage of the H+GaAs substrate as a function of the nominal thickness of DiMe-PTCDI was assessed via C-V measurements assuming a voltage independent capacitance of the organic layer. The frequency response of the device was evaluated through C-V and impedance measurements in the range 1 kHz-1 MHz. The almost independent behaviour of the capacitance in the measured frequency range confirmed the assumption of a near geometrical capacitor, which was used for modelling the impedance with an equivalent circuit of seven components. From there it was found a predominance of the space charge region impedance, so that A.C. conduction can only takes place through the

  19. Charge carrier coherence and Hall effect in organic semiconductors.

    Science.gov (United States)

    Yi, H T; Gartstein, Y N; Podzorov, V

    2016-03-30

    Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

  20. Hybrid organic semiconductor lasers for bio-molecular sensing.

    Science.gov (United States)

    Haughey, Anne-Marie; Foucher, Caroline; Guilhabert, Benoit; Kanibolotsky, Alexander L; Skabara, Peter J; Burley, Glenn; Dawson, Martin D; Laurand, Nicolas

    2014-01-01

    Bio-functionalised luminescent organic semiconductors are attractive for biophotonics because they can act as efficient laser materials while simultaneously interacting with molecules. In this paper, we present and discuss a laser biosensor platform that utilises a gain layer made of such an organic semiconductor material. The simple structure of the sensor and its operation principle are described. Nanolayer detection is shown experimentally and analysed theoretically in order to assess the potential and the limits of the biosensor. The advantage conferred by the organic semiconductor is explained, and comparisons to laser sensors using alternative dye-doped materials are made. Specific biomolecular sensing is demonstrated, and routes to functionalisation with nucleic acid probes, and future developments opened up by this achievement, are highlighted. Finally, attractive formats for sensing applications are mentioned, as well as colloidal quantum dots, which in the future could be used in conjunction with organic semiconductors.

  1. Contorted Organic Semiconductors for Molecular Electronics

    Science.gov (United States)

    Zhong, Yu

    Chapter 4, I discuss helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometers in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells. In Chapter 5, I compare analogous cyclic and acyclic pi-conjugated molecules as n-type electronic materials and find that the cyclic molecules have numerous benefits in organic photovoltaics. We designed two conjugated cycles for this study. Each comprises four subunits; one combines four electron-accepting, redox-active, diphenyl-perylenediimide subunits, and the other alternates two electron-donating bithiophene units with two diphenyl-perylenediimide units. We compare the macrocycles to acyclic versions of these molecules and find that, relative to the acyclic analogs, the conjugated macrocycles have bathochromically shifted UV-vis absorbances and are more easily reduced. In blended films, macrocycle-based devices show higher electron mobility and good morphology. All of these factors contribute to the more than doubling of the power conversion efficiency observed in organic photovoltaic devices with these macrocycles as the n-type, electron transporting material. This study highlights the importance of geometric design in creating new molecular semiconductors. In Chapter 6, I describe a new molecular design that enables high performance organic photodetectors. We use a rigid, conjugated macrocycle as the electron acceptor in devices to obtain high photocurrent and low dark current. We directly compare the

  2. Synchrotron radiation studies of inorganic-organic semiconductor interfaces

    CERN Document Server

    Evans, D A; Vearey-Roberts, A R; Bushell, A; Cabailh, G; O'Brien, S; Wells, J W; McGovern, I T; Dhanak, V R; Kampen, T U; Zahn, D R T; Batchelor, D

    2003-01-01

    Organic semiconductors (polymers and small molecules) are widely used in electronic and optoelectronic technologies. Many devices are based on multilayer structures where interfaces play a central role in device performance and where inorganic semiconductor models are inadequate. Synchrotron radiation techniques such as photoelectron spectroscopy (PES), near-edge X-ray absorption fine structure (NEXAFS) and X-ray standing wave spectroscopy (XSW) provide a powerful means of probing the structural, electronic and chemical properties of these interfaces. The surface-specificity of these techniques allows key properties to be monitored as the heterostructure is fabricated. This methodology has been directed at the growth of hybrid organic-inorganic semiconductor interfaces involving copper phthalocyanine as the model organic material and InSb and GaAs as the model inorganic semiconductor substrates. Core level PES has revealed that these interfaces are abrupt and chemically inert due to the weak bonding between t...

  3. Comparison of junctionless and inversion-mode p-type metal-oxide-semiconductor field-effect transistors in presence of hole-phonon interactions

    Energy Technology Data Exchange (ETDEWEB)

    Dib, E., E-mail: elias.dib@for.unipi.it [Dipartimento di Ingegneria dell' Informazione, Università di Pisa, 56122 Pisa (Italy); Carrillo-Nuñez, H. [Integrated Systems Laboratory ETH Zürich, Gloriastrasse 35, 8092 Zürich (Switzerland); Cavassilas, N.; Bescond, M. [IM2NP, UMR CNRS 6242, Bât. IRPHE, Technopôle de Château-Gombert, 13384 Marseille Cedex 13 (France)

    2016-01-28

    Junctionless transistors are being considered as one of the alternatives to conventional metal-oxide field-effect transistors. In this work, it is then presented a simulation study of silicon double-gated p-type junctionless transistors compared with its inversion-mode counterpart. The quantum transport problem is solved within the non-equilibrium Green's function formalism, whereas hole-phonon interactions are tackled by means of the self-consistent Born approximation. Our findings show that junctionless transistors should perform as good as a conventional transistor only for ultra-thin channels, with the disadvantage of requiring higher supply voltages in thicker channel configurations.

  4. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics.

    Science.gov (United States)

    D'Avino, Gabriele; Muccioli, Luca; Castet, Frédéric; Poelking, Carl; Andrienko, Denis; Soos, Zoltán G; Cornil, Jérôme; Beljonne, David

    2016-11-01

    This review summarizes the current understanding of electrostatic phenomena in ordered and disordered organic semiconductors, outlines numerical schemes developed for quantitative evaluation of electrostatic and induction contributions to ionization potentials and electron affinities of organic molecules in a solid state, and illustrates two applications of these techniques: interpretation of photoelectron spectroscopy of thin films and energetics of heterointerfaces in organic solar cells.

  5. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics

    Science.gov (United States)

    D'Avino, Gabriele; Muccioli, Luca; Castet, Frédéric; Poelking, Carl; Andrienko, Denis; Soos, Zoltán G.; Cornil, Jérôme; Beljonne, David

    2016-11-01

    This review summarizes the current understanding of electrostatic phenomena in ordered and disordered organic semiconductors, outlines numerical schemes developed for quantitative evaluation of electrostatic and induction contributions to ionization potentials and electron affinities of organic molecules in a solid state, and illustrates two applications of these techniques: interpretation of photoelectron spectroscopy of thin films and energetics of heterointerfaces in organic solar cells.

  6. Ultrafast dynamics and laser action of organic semiconductors

    CERN Document Server

    Vardeny, Zeev Valy

    2009-01-01

    Spurred on by extensive research in recent years, organic semiconductors are now used in an array of areas, such as organic light emitting diodes (OLEDs), photovoltaics, and other optoelectronics. In all of these novel applications, the photoexcitations in organic semiconductors play a vital role. Exploring the early stages of photoexcitations that follow photon absorption, Ultrafast Dynamics and Laser Action of Organic Semiconductors presents the latest research investigations on photoexcitation ultrafast dynamics and laser action in pi-conjugated polymer films, solutions, and microcavities.In the first few chapters, the book examines the interplay of charge (polarons) and neutral (excitons) photoexcitations in pi-conjugated polymers, oligomers, and molecular crystals in the time domain of 100 fs-2 ns. Summarizing the state of the art in lasing, the final chapters introduce the phenomenon of laser action in organics and cover the latest optoelectronic applications that use lasing based on a variety of caviti...

  7. Molecular Electrical Doping of Organic Semiconductors: Fundamental Mechanisms and Emerging Dopant Design Rules.

    Science.gov (United States)

    Salzmann, Ingo; Heimel, Georg; Oehzelt, Martin; Winkler, Stefanie; Koch, Norbert

    2016-03-15

    -Dirac occupation of which ultimately determines the doping efficiency, thus emerges as key challenge. As a first step, the formation of charge transfer complexes is identified as being detrimental to the doping efficiency, which suggests sterically shielding the functional core of dopant molecules as an additional design rule to complement the requirement of low ionization energies or high electron affinities in efficient n-type or p-type dopants, respectively. In an extended outlook, we finally argue that, to fully meet this challenge, an improved understanding is required of just how the admixture of dopant molecules to organic semiconductors does affect the density of states: compared with their inorganic counterparts, traps for charge carriers are omnipresent in organic semiconductors due to structural and chemical imperfections, and Coulomb attraction between ionized dopants and free charge carriers is typically stronger in organic semiconductors owing to their lower dielectric constant. Nevertheless, encouraging progress is being made toward developing a unifying picture that captures the entire range of doping induced phenomena, from ion-pair to complex formation, in both conjugated polymers and molecules. Once completed, such a picture will provide viable guidelines for synthetic and supramolecular chemistry that will enable further technological advances in organic and hybrid organic/inorganic devices.

  8. Semiconductor Metal-Organic Frameworks: Future Low-Bandgap Materials.

    Science.gov (United States)

    Usman, Muhammad; Mendiratta, Shruti; Lu, Kuang-Lieh

    2017-02-01

    Metal-organic frameworks (MOFs) with low density, high porosity, and easy tunability of functionality and structural properties, represent potential candidates for use as semiconductor materials. The rapid development of the semiconductor industry and the continuous miniaturization of feature sizes of integrated circuits toward the nanometer (nm) scale require novel semiconductor materials instead of traditional materials like silicon, germanium, and gallium arsenide etc. MOFs with advantageous properties of both the inorganic and the organic components promise to serve as the next generation of semiconductor materials for the microelectronics industry with the potential to be extremely stable, cheap, and mechanically flexible. Here, a perspective of recent research is provided, regarding the semiconducting properties of MOFs, bandgap studies, and their potential in microelectronic devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Carrier localization on surfaces of organic semiconductors gated with electrolytes.

    Science.gov (United States)

    Xia, Yu; Xie, Wei; Ruden, P Paul; Frisbie, C Daniel

    2010-07-16

    Organic semiconductor single crystals gated with electrolytes exhibit a pronounced maximum in channel conductance at hole densities >10(13)   cm(-2). The cause is a strong decrease in the hole mobility with increasing charge density, which is explained in terms of a percolation model that incorporates trapping of holes by ions at the semiconductor-electrolyte interface. In the case of rubrene crystals, the peak channel conductance occurs at hole densities near 3 × 10(13)  cm(-2). The magnitude of the effect will be large for semiconductors with low dielectric constants and narrow bandwidths, and thus is likely to be a general phenomenon in organic semiconductors gated with electrolytes.

  10. Suppressing molecular vibrations in organic semiconductors by inducing strain.

    Science.gov (United States)

    Kubo, Takayoshi; Häusermann, Roger; Tsurumi, Junto; Soeda, Junshi; Okada, Yugo; Yamashita, Yu; Akamatsu, Norihisa; Shishido, Atsushi; Mitsui, Chikahiko; Okamoto, Toshihiro; Yanagisawa, Susumu; Matsui, Hiroyuki; Takeya, Jun

    2016-01-01

    Organic molecular semiconductors are solution processable, enabling the growth of large-area single-crystal semiconductors. Improving the performance of organic semiconductor devices by increasing the charge mobility is an ongoing quest, which calls for novel molecular and material design, and improved processing conditions. Here we show a method to increase the charge mobility in organic single-crystal field-effect transistors, by taking advantage of the inherent softness of organic semiconductors. We compress the crystal lattice uniaxially by bending the flexible devices, leading to an improved charge transport. The mobility increases from 9.7 to 16.5 cm(2) V(-1) s(-1) by 70% under 3% strain. In-depth analysis indicates that compressing the crystal structure directly restricts the vibration of the molecules, thus suppresses dynamic disorder, a unique mechanism in organic semiconductors. Since strain can be easily induced during the fabrication process, we expect our method to be exploited to build high-performance organic devices.

  11. Design of ``push-pull'' p-type quinoid-based organic dyes with near-IR absorption: A density function theory study

    Science.gov (United States)

    Yang, Zhenqing; Li, Juan; Liu, Yun; Zhang, Wansong

    2017-04-01

    Based on an experimentally synthesized p-type dye QT-1, we screened and designed a series of quinoid-based "push-pull" dyes SPL401 - SPL407 by modifying the π-conjugated linker for ptype dye-sensitized solar cells (p-type DSSC). Further, we systematically calculated their electronic and optical properties by using the density functional theory (DFT) and the time-dependent DFT (TDDFT). The results indicate that compared to QT-1, SPL406 and SPL407, which have not only smaller energy gaps, higher oscillator strength f increased by 70% and 80%, and 141 nm and 110 nm redshifts, respectively, but also a broader absorption spectrum covering the entire visible range to the near-IR region of 1200 nm, may be the most promising candidates among SPL401 - SPL407 for p-type organic sensitizers.

  12. Three-dimensional charge transport in organic semiconductor single crystals.

    Science.gov (United States)

    He, Tao; Zhang, Xiying; Jia, Jiong; Li, Yexin; Tao, Xutang

    2012-04-24

    Three-dimensional charge transport anisotropy in organic semiconductor single crystals - both plates and rods (above and below, respectively, in the figure) - is measured in well-performing organic field-effect transistors for the first time. The results provide an excellent model for molecular design and device preparation that leads to good performance.

  13. Synthesis and characterization of a new organic semiconductor material

    Energy Technology Data Exchange (ETDEWEB)

    Tiffour, Imane [Laboratoire de Génie Physique, Département de Physique, Université de Tiaret, Tiaret 14000 (Algeria); Faculté des Sciences et Technologies, Université Mustapha Stambouli, Mascara 29000 (Algeria); Dehbi, Abdelkader [Laboratoire de Génie Physique, Département de Physique, Université de Tiaret, Tiaret 14000 (Algeria); Mourad, Abdel-Hamid I., E-mail: ahmourad@uaeu.ac.ae [Mechanical Engineering Department, Faculty of Engineering, United Arab Emirates University, Al-Ain, P.O. Box 15551 (United Arab Emirates); Belfedal, Abdelkader [Faculté des Sciences et Technologies, Université Mustapha Stambouli, Mascara 29000 (Algeria); LPCMME, Département de Physique, Université d' Oran Es-sénia, 3100 Oran (Algeria)

    2016-08-01

    The objective of this study is to create an ideal mixture of Acetaminophen/Curcumin leading to a new and improved semiconductor material, by a study of the electrical, thermal and optical properties. This new material will be compared with existing semiconductor technology to discuss its viability within the industry. The electrical properties were investigated using complex impedance spectroscopy and optical properties were studied by means of UV-Vis spectrophotometry. The electric conductivity σ, the dielectric constant ε{sub r}, the activation energy E{sub a}, the optical transmittance T and the gap energy E{sub g} have been investigated in order to characterize our organic material. The electrical conductivity of the material is approximately 10{sup −5} S/m at room temperature, increasing the temperature causes σ to increase exponentially to approximately 10{sup −4} S/m. The activation energy obtained for the material is equal to 0.49 ± 0.02 ev. The optical absorption spectra show that the investigating material has absorbance in the visible range with a maximum wavelength (λ{sub max}) 424 nm. From analysis, the absorption spectra it was found the optical band gap equal to 2.6 ± 0.02 eV and 2.46 ± 0.02 eV for the direct and indirect transition, respectively. In general, the study shows that the developed material has characteristics of organic semiconductor material that has a promising future in the field of organic electronics and their potential applications, e.g., photovoltaic cells. - Highlights: • Development of a new organic acetaminophen/Curcumin semiconductor material. • The developed material has characteristics of an organic semiconductor. • It has electrical conductivity comparable to available organic semiconductors. • It has high optical transmittance and low permittivity/dielectric constant.

  14. Modeling of Spatially Correlated Energetic Disorder in Organic Semiconductors.

    Science.gov (United States)

    Kordt, Pascal; Andrienko, Denis

    2016-01-12

    Mesoscale modeling of organic semiconductors relies on solving an appropriately parametrized master equation. Essential ingredients of the parametrization are site energies (driving forces), which enter the charge transfer rate between pairs of neighboring molecules. Site energies are often Gaussian-distributed and are spatially correlated. Here, we propose an algorithm that generates these energies with a given Gaussian distribution and spatial correlation function. The method is tested on an amorphous organic semiconductor, DPBIC, illustrating that the accurate description of correlations is essential for the quantitative modeling of charge transport in amorphous mesophases.

  15. Organic semiconductor heterojunctions and its application in organic light-emitting diodes

    CERN Document Server

    Ma, Dongge

    2017-01-01

    This book systematically introduces the most important aspects of organic semiconductor heterojunctions, including the basic concepts and electrical properties. It comprehensively discusses the application of organic semiconductor heterojunctions as charge injectors and charge generation layers in organic light-emitting diodes (OLEDs). Semiconductor heterojunctions are the basis for constructing high-performance optoelectronic devices. In recent decades, organic semiconductors have been increasingly used to fabricate heterojunction devices, especially in OLEDs, and the subject has attracted a great deal of attention and evoked many new phenomena and interpretations in the field. This important application is based on the low dielectric constant of organic semiconductors and the weak non-covalent electronic interactions between them, which means that they easily form accumulation heterojunctions. As we know, the accumulation-type space charge region is highly conductive, which is an important property for high...

  16. Molecular and polymeric organic semiconductors for applications in photovoltaic devices

    CERN Document Server

    Meinhardt, G

    2000-01-01

    Photovoltaic devices based on molecular as well as polymeric semiconductors were investigated and characterized. The organic materials presented here exhibit the advantages of low price, low processing costs and the possibility of tuning their optical properties. The photovoltaic properties were investigated by photocurrent action spectroscopy and I/V-characterization and the electric field distribution in each layer by electroabsorption spectroscopy. Single layer devices of molecular semiconductors and semiconducting polymers like methyl-substituted polyparaphenylene, CN-Ether-PPV, copper-phthalocyanine, the terryleneimide DOTer, the perylene derivatives BBP-perylene and polyBBP-perylene show low photocurrents as well as a small photovoltaic effect in their pristine form. One way to enhance the performance is to blend the active layer with molecular dopands like a soluble form of titaniumoxophthalocyanine or the aromatic macromolecule RS19 or to combine two organic semiconductors in heterostructure devices. ...

  17. Chemical Defects, Electronic Structure, and Transport in N-type and P-type Organic Semiconductors: First Principles Theory

    Science.gov (United States)

    2012-11-29

    boundaries. A paper describing the work was published in Nature Materials. {J. Rivnay, L.H. Jimison, J. E. Northrup, M. F. Toney, R. Noriega , S. Lu, T. J...Switzerland.[4] [1] J. Rivnay, R. Noriega , J. E. Northrup, R. J. Kline, M. F. Toney, and A. Salleo, Structural origin of gap states in semicrystalline...1] J. Rivnay, L.H. Jimison, J. E. Northrup, M. F. Toney, R. Noriega , S. Lu, T. J. Marks, A, Facchetti, and A. Salleo, Large modulation of

  18. Molecular fingerprints in the electronic properties of crystalline organic semiconductors

    DEFF Research Database (Denmark)

    Ciuchi, S.; Hatch, R.C.; Höchst, H.

    2012-01-01

    bands can be achieved in organic semiconductors provided that one properly accounts for the coupling to molecular vibrational modes and the presence of disorder. Our findings rationalize the growing experimental evidence that even the best band structure theories based on a many-body treatment...

  19. High Gain Hybrid Graphene-Organic Semiconductor Phototransistors

    NARCIS (Netherlands)

    Huisman, Everardus H.; Shulga, Artem G.; Zomer, Paul J.; Tombros, Nikolaos; Bartesaghi, Davide; Bisri, Satria Zulkarnaen; Loi, Maria A.; Koster, L. Jan Anton; van Wees, Bart J.

    2015-01-01

    Hybrid phototransistors of graphene and the organic semiconductor poly(3-hexylthiophene-2,5-diyl) (P3HT) are presented. Two types of phototransistors are demonstrated with a charge carrier transit time that differs by more than 6 orders of magnitude. High transit time devices are fabricated using a

  20. Trap-assisted recombination in disordered organic semiconductors

    NARCIS (Netherlands)

    Kuik, M.; Koster, L.J.A.; Wetzelaer, G.A.H.; Blom, P.W.M.

    2011-01-01

    The trap-assisted recombination of electrons and holes in organic semiconductors is investigated. The extracted capture coefficients of the trap-assisted recombination process are thermally activated with an identical activation energy as measured for the hole mobility μp. We demonstrate that the ra

  1. π-Conjugated Organic Semiconductors for Field-Effect Transistors

    Institute of Scientific and Technical Information of China (English)

    LIU Yun-qi

    2005-01-01

    @@ 1Results and Discussion Organic semiconductors employed as active layers in field-effect transistors (FETs) are of great current interest because such FETs can potentially be fabricated at low cost, over large areas, and on flexible substrates. Such facile fabrication approaches offer a significant advantage over silicon technology in numerous applications.

  2. Selective Conversion from p-Type to n-Type of Printed Bottom-Gate Carbon Nanotube Thin-Film Transistors and Application in Complementary Metal-Oxide-Semiconductor Inverters.

    Science.gov (United States)

    Xu, Qiqi; Zhao, Jianwen; Pecunia, Vincenzo; Xu, Wenya; Zhou, Chunshan; Dou, Junyan; Gu, Weibing; Lin, Jian; Mo, Lixin; Zhao, Yanfei; Cui, Zheng

    2017-03-30

    The fabrication of printed high-performance and environmentally stable n-type single-walled carbon nanotube (SWCNT) transistors and their integration into complementary (i.e., complementary metal-oxide-semiconductor, CMOS) circuits are widely recognized as key to achieving the full potential of carbon nanotube electronics. Here, we report a simple, efficient, and robust method to convert the polarity of SWCNT thin-film transistors (TFTs) using cheap and readily available ethanolamine as an electron doping agent. Printed p-type bottom-gate SWCNT TFTs can be selectively converted into n-type by deposition of ethanolamine inks on the transistor active region via aerosol jet printing. Resulted n-type TFTs show excellent electrical properties with an on/off ratio of 10(6), effective mobility up to 30 cm(2) V(-1) s(-1), small hysteresis, and small subthreshold swing (90-140 mV dec(-1)), which are superior compared to the original p-type SWCNT devices. The n-type SWCNT TFTs also show good stability in air, and any deterioration of performance due to shelf storage can be fully recovered by a short low-temperature annealing. The easy polarity conversion process allows construction of CMOS circuitry. As an example, CMOS inverters were fabricated using printed p-type and n-type TFTs and exhibited a large noise margin (50 and 103% of 1/2 Vdd = 1 V) and a voltage gain as high as 30 (at Vdd = 1 V). Additionally, the CMOS inverters show full rail-to-rail output voltage swing and low power dissipation (0.1 μW at Vdd = 1 V). The new method paves the way to construct fully functional complex CMOS circuitry by printed TFTs.

  3. Inkjet-Printed Organic Transistors Based on Organic Semiconductor/Insulating Polymer Blends

    Directory of Open Access Journals (Sweden)

    Yoon-Jung Kwon

    2016-08-01

    Full Text Available Recent advances in inkjet-printed organic field-effect transistors (OFETs based on organic semiconductor/insulating polymer blends are reviewed in this article. Organic semiconductor/insulating polymer blends are attractive ink candidates for enhancing the jetting properties, inducing uniform film morphologies, and/or controlling crystallization behaviors of organic semiconductors. Representative studies using soluble acene/insulating polymer blends as an inkjet-printed active layer in OFETs are introduced with special attention paid to the phase separation characteristics of such blended films. In addition, inkjet-printed semiconducting/insulating polymer blends for fabricating high performance printed OFETs are reviewed.

  4. Small molecule organic semiconductors on the move: promises for future solar energy technology.

    Science.gov (United States)

    Mishra, Amaresh; Bäuerle, Peter

    2012-02-27

    This article is written from an organic chemist's point of view and provides an up-to-date review about organic solar cells based on small molecules or oligomers as absorbers and in detail deals with devices that incorporate planar-heterojunctions (PHJ) and bulk heterojunctions (BHJ) between a donor (p-type semiconductor) and an acceptor (n-type semiconductor) material. The article pays particular attention to the design and development of molecular materials and their performance in corresponding devices. In recent years, a substantial amount of both, academic and industrial research, has been directed towards organic solar cells, in an effort to develop new materials and to improve their tunability, processability, power conversion efficiency, and stability. On the eve of commercialization of organic solar cells, this review provides an overview over efficiencies attained with small molecules/oligomers in OSCs and reflects materials and device concepts developed over the last decade. Approaches to enhancing the efficiency of organic solar cells are analyzed.

  5. Enhancement of efficiencies for tandem green phosphorescent organic light-emitting devices with a p-type charge generation layer

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Byung Soo; Jeon, Young Pyo; Lee, Dae Uk; Kim, Tae Whan, E-mail: twk@hanayng.ac.kr

    2014-10-15

    The operating voltage of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was improved by 3% over that of the organic light-emitting device with a molybdenum trioxide layer. The maximum brightness of the tandem green phosphorescent organic light-emitting device at 21.9 V was 26,540 cd/m{sup 2}. The dominant peak of the electroluminescence spectra for the devices was related to the fac-tris(2-phenylpyridine) iridium emission. - Highlights: • Tandem OLEDs with CGL were fabricated to enhance their efficiency. • The operating voltage of the tandem OLED with a HAT-CN layer was improved by 3%. • The efficiency and brightness of the tandem OLED were 13.9 cd/A and 26,540 cd/m{sup 2}. • Efficiency of the OLED with a HAT-CN layer was lower than that with a MoO{sub 3} layer. - Abstract: Tandem green phosphorescent organic light-emitting devices with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile or a molybdenum trioxide charge generation layer were fabricated to enhance their efficiency. Current density–voltage curves showed that the operating voltage of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was improved by 3% over that of the corresponding organic light-emitting device with a molybdenum trioxide layer. The efficiency and the brightness of the tandem green phosphorescent organic light-emitting device were 13.9 cd/A and 26,540 cd/m{sup 2}, respectively. The current efficiency of the tandem green phosphorescent organic light-emitting device with a 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer was lower by 1.1 times compared to that of the corresponding organic light-emitting device with molybdenum trioxide layer due to the decreased charge generation and transport in the 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile layer resulting from triplet–triplet exciton annihilation.

  6. Organic semiconductor growth and morphology considerations for organic thin-film transistors.

    Science.gov (United States)

    Virkar, Ajay A; Mannsfeld, Stefan; Bao, Zhenan; Stingelin, Natalie

    2010-09-08

    Analogous to conventional inorganic semiconductors, the performance of organic semiconductors is directly related to their molecular packing, crystallinity, growth mode, and purity. In order to achieve the best possible performance, it is critical to understand how organic semiconductors nucleate and grow. Clever use of surface and dielectric modification chemistry can allow one to control the growth and morphology, which greatly influence the electrical properties of the organic transistor. In this Review, the nucleation and growth of organic semiconductors on dielectric surfaces is addressed. The first part of the Review concentrates on small-molecule organic semiconductors. The role of deposition conditions on film formation is described. The modification of the dielectric interface using polymers or self-assembled mono-layers and their effect on organic-semiconductor growth and performance is also discussed. The goal of this Review is primarily to discuss the thin-film formation of organic semiconducting species. The patterning of single crystals is discussed, while their nucleation and growth has been described elsewhere (see the Review by Liu et. al).([¹]) The second part of the Review focuses on polymeric semiconductors. The dependence of physico-chemical properties, such as chain length (i.e., molecular weight) of the constituting macromolecule, and the influence of small molecular species on, e.g., melting temperature, as well as routes to induce order in such macromolecules, are described.

  7. Organic semiconductors: What makes the spin relax?

    Science.gov (United States)

    Bobbert, Peter A.

    2010-04-01

    Spin relaxation in organic materials is expected to be slow because of weak spin-orbit coupling. The effects of deuteration and coherent spin excitation show that the spin-relaxation time is actually limited by hyperfine fields.

  8. Electroless silver plating of the surface of organic semiconductors.

    Science.gov (United States)

    Campione, Marcello; Parravicini, Matteo; Moret, Massimo; Papagni, Antonio; Schröter, Bernd; Fritz, Torsten

    2011-10-04

    The integration of nanoscale processes and devices demands fabrication routes involving rapid, cost-effective steps, preferably carried out under ambient conditions. The realization of the metal/organic semiconductor interface is one of the most demanding steps of device fabrication, since it requires mechanical and/or thermal treatments which increment costs and are often harmful in respect to the active layer. Here, we provide a microscopic analysis of a room temperature, electroless process aimed at the deposition of a nanostructured metallic silver layer with controlled coverage atop the surface of single crystals and thin films of organic semiconductors. This process relies on the reaction of aqueous AgF solutions with the nonwettable crystalline surface of donor-type organic semiconductors. It is observed that the formation of a uniform layer of silver nanoparticles can be accomplished within 20 min contact time. The electrical characterization of two-terminal devices performed before and after the aforementioned treatment shows that the metal deposition process is associated with a redox reaction causing the p-doping of the semiconductor.

  9. Circuit design in organic semiconductor technologies

    NARCIS (Netherlands)

    Heremans, P.; Dehaene, W.; Steyaert, M.; Myny, K.; Mariën, H.; Genoe, J.; Gelinck, G.H.; Veenendaal, E. van

    2011-01-01

    In this paper, we review the state of the art of digital and analog circuits that have been shown in recent years in organic thin-film transistor technology on flexible plastic foil. The transistors are developed for backplanes of displays, and therefore have the characteristics to be unipolar and t

  10. Improvement in the Photocurrent of Inverted Organic Solar Cells Using MoO(x)-Doped TAPC as a P-Type Optical Spacer.

    Science.gov (United States)

    Song, Jiyun; Song, Hyung-Jun; Kim, Jun Young; Lee, Yeonkyung; Park, Myeongjin; Kwon, Yongwon; Ko, Youngjun; Lee, Changhee

    2016-05-01

    In this work, we demonstrate enhancement in the short-circuit current of inverted organic photovoltaic cells (OPVs) using a p-type optical spacer. The p-type optical spacer, which consists of molybdenum oxide (MoO(x))-doped 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), shows improved transmittance at visible light with high electrical conductivity. The electrical field distribution of incident light at the active layer of OPVs can be controlled by tuning the thickness of the optical spacer in the OPVs. Specifically, the incorporation of the 20-nm optical spacer layer in the OPV leads to enhanced spectral response of the device in the wavelength range of 400-600 nm, which is consistent with the combined results of improved optical absorption and better charge transport characteristics. As a result, the OPV with a 20-nm p-type optical spacer shows improvement in the short-circuit current compared with a device with 10 nm of embedded MoO(x).

  11. Strong Coupling between Plasmons and Organic Semiconductors

    Directory of Open Access Journals (Sweden)

    Joel Bellessa

    2014-05-01

    Full Text Available In this paper we describe the properties of organic material in strong coupling with plasmon, mainly based on our work in this field of research. The strong coupling modifies the optical transitions of the structure, and occurs when the interaction between molecules and plasmon prevails on the damping of the system. We describe the dispersion relation of different plasmonic systems, delocalized and localized plasmon, coupled to aggregated dyes and the typical properties of these systems in strong coupling. The modification of the dye emission is also studied. In the second part, the effect of the microscopic structure of the organics, which can be seen as a disordered film, is described. As the different molecules couple to the same plasmon mode, an extended coherent state on several microns is observed.

  12. Glass-Forming Organic Semiconductors for Optoelectronics

    Directory of Open Access Journals (Sweden)

    Aušra TOMKEVIČIENĖ

    2011-11-01

    Full Text Available Organic electronics and optoelectronics are newly emerging fields of science and technology that cover chemistry, physics, and materials science. Electronic and optoelectronic devices using organic materials are attractive because of the materials characteristics, potentially low cost, and capability of large-area, flexible device fabrication. Such devices as OLEDs, OPVs, and OFETs involve charge transport as a main process in their operation processes, and therefore, require high-performance charge-transporting materials. This review article focuses on charge-transporting materials for use in OLEDs, OPVs, and OFETs. We have tried to arrange the charge-transporting materials in order by classifying them on the basis of their molecular structures. Molecular design concepts for charge-transporting materials and their charge-transport properties are discussed.http://dx.doi.org/10.5755/j01.ms.17.4.767

  13. Modeling disordered morphologies in organic semiconductors.

    Science.gov (United States)

    Neumann, Tobias; Danilov, Denis; Lennartz, Christian; Wenzel, Wolfgang

    2013-12-05

    Organic thin film devices are investigated for many diverse applications, including light emitting diodes, organic photovoltaic and organic field effect transistors. Modeling of their properties on the basis of their detailed molecular structure requires generation of representative morphologies, many of which are amorphous. Because time-scales for the formation of the molecular structure are slow, we have developed a linear-scaling single molecule deposition protocol which generates morphologies by simulation of vapor deposition of molecular films. We have applied this protocol to systems comprising argon, buckminsterfullerene, N,N-Di(naphthalene-1-yl)-N,N'-diphenyl-benzidine, mer-tris(8-hydroxy-quinoline)aluminum(III), and phenyl-C61-butyric acid methyl ester, with and without postdeposition relaxation of the individually deposited molecules. The proposed single molecule deposition protocol leads to formation of highly ordered morphologies in argon and buckminsterfullerene systems when postdeposition relaxation is used to locally anneal the configuration in the vicinity of the newly deposited molecule. The other systems formed disordered amorphous morphologies and the postdeposition local relaxation step has only a small effect on the characteristics of the disordered morphology in comparison to the materials forming crystals.

  14. Employing PEDOT as the p-Type Charge Collection Layer in Regular Organic-Inorganic Perovskite Solar Cells.

    Science.gov (United States)

    Liu, Jiewei; Pathak, Sandeep; Stergiopoulos, Thomas; Leijtens, Tomas; Wojciechowski, Konrad; Schumann, Stefan; Kausch-Busies, Nina; Snaith, Henry J

    2015-05-07

    Organic-inorganic halide perovskite solar cells have recently emerged as high-performance photovoltaic devices with low cost, promising for affordable large-scale energy production, with laboratory cells already exceeding 20% power conversion efficiency (PCE). To date, a relatively expensive organic hole-conducting molecule with low conductivity, namely spiro-OMeTAD (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine) 9,9'- spirobifluorene), is employed widely to achieve highly efficient perovskite solar cells. Here, we report that by replacing spiro-OMeTAD with much cheaper and highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) we can achieve PCE of up to 14.5%, with PEDOT cast from a toluene based ink. However, the stabilized power output of the PEDOT-based devices is only 6.6%, in comparison to 9.4% for the spiro-OMeTAD-based cells. We deduce that accelerated recombination is the cause for this lower stabilized power output and postulate that reduced levels of p-doping are required to match the stabilized performance of Spiro-OMeTAD. The entirely of the materials employed in the perovskite solar cell are now available at commodity scale and extremely inexpensive.

  15. Toward continuous-wave operation of organic semiconductor lasers

    Science.gov (United States)

    Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

    2017-01-01

    The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

  16. Study of neural cells on organic semiconductor ultra thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bystrenova, Eva; Tonazzini, Ilaria; Stoliar, Pablo; Greco, Pierpaolo; Lazar, Adina; Dutta, Soumya; Dionigi, Chiara; Cacace, Marcello; Biscarini, Fabio [ISMN-CNR, Bologna (Italy); Jelitai, Marta; Madarasz, Emilia [IEM- HAS, Budapest (Hungary); Huth, Martin; Nickel, Bert [LMU, Munich (Germany); Martini, Claudia [Dept. PNPB, Univ. of Pisa (Italy)

    2008-07-01

    Many technological advances are currently being developed for nano-fabrication, offering the ability to create and control patterns of soft materials. We report the deposition of cells on organic semiconductor ultra-thin films. This is a first step towards the development of active bio/non bio systems for electrical transduction. Thin films of pentacene, whose thickness was systematically varied, were grown by high vacuum sublimation. We report adhesion, growth, and differentiation of human astroglial cells and mouse neural stem cells on an organic semiconductor. Viability of astroglial cells in time was measured as a function of the roughness and the characteristic morphology of ultra thin organic film, as well as the features of the patterned molecules. Optical fluorescence microscope coupled to atomic force microscope was used to monitor the presence, density and shape of deposited cells. Neural stem cells remain viable, differentiate by retinoic acid and form dense neuronal networks. We have shown the possibility to integrate living neural cells on organic semiconductor thin films.

  17. n-Channel semiconductor materials design for organic complementary circuits.

    Science.gov (United States)

    Usta, Hakan; Facchetti, Antonio; Marks, Tobin J

    2011-07-19

    Organic semiconductors have unique properties compared to traditional inorganic materials such as amorphous or crystalline silicon. Some important advantages include their adaptability to low-temperature processing on flexible substrates, low cost, amenability to high-speed fabrication, and tunable electronic properties. These features are essential for a variety of next-generation electronic products, including low-power flexible displays, inexpensive radio frequency identification (RFID) tags, and printable sensors, among many other applications. Accordingly, the preparation of new materials based on π-conjugated organic molecules or polymers has been a central scientific and technological research focus over the past decade. Currently, p-channel (hole-transporting) materials are the leading class of organic semiconductors. In contrast, high-performance n-channel (electron-transporting) semiconductors are relatively rare, but they are of great significance for the development of plastic electronic devices such as organic field-effect transistors (OFETs). In this Account, we highlight the advances our team has made toward realizing moderately and highly electron-deficient n-channel oligomers and polymers based on oligothiophene, arylenediimide, and (bis)indenofluorene skeletons. We have synthesized and characterized a "library" of structurally related semiconductors, and we have investigated detailed structure-property relationships through optical, electrochemical, thermal, microstructural (both single-crystal and thin-film), and electrical measurements. Our results reveal highly informative correlations between structural parameters at various length scales and charge transport properties. We first discuss oligothiophenes functionalized with perfluoroalkyl and perfluoroarene substituents, which represent the initial examples of high-performance n-channel semiconductors developed in this project. The OFET characteristics of these compounds are presented with an

  18. Simulating charge transport in organic semiconductors and devices: a review

    Science.gov (United States)

    Groves, C.

    2017-02-01

    Charge transport simulation can be a valuable tool to better understand, optimise and design organic transistors (OTFTs), photovoltaics (OPVs), and light-emitting diodes (OLEDs). This review presents an overview of common charge transport and device models; namely drift-diffusion, master equation, mesoscale kinetic Monte Carlo and quantum chemical Monte Carlo, and a discussion of the relative merits of each. This is followed by a review of the application of these models as applied to charge transport in organic semiconductors and devices, highlighting in particular the insights made possible by modelling. The review concludes with an outlook for charge transport modelling in organic electronics.

  19. Effective Temperature and Universal Conductivity Scaling in Organic Semiconductors

    OpenAIRE

    Hassan Abdalla; Kevin van de Ruit; Martijn Kemerink

    2015-01-01

    We investigate the scalability of the temperature- and electric field-dependence of the conductivity of disordered organic semiconductors to ‘universal’ curves by two different but commonly employed methods; by so-called universal scaling and by using the effective temperature concept. Experimentally both scaling methods were found to be equally applicable to the out-of-plane charge transport in PEDOT:PSS thin films of various compositions. Both methods are shown to be equivalent in terms of ...

  20. Ultrathin organic semiconductor films--soft matter effect.

    Science.gov (United States)

    Wang, Tong; Yan, Donghang

    2014-05-01

    The growth of organic semiconductor thin films has been a crucial issue in organic electronics, especially the growth at the early stages. The thin-film phase has been found to be a common phenomenon in many organic semiconductor thin films, which is closely related with the weak van der Waals interaction between organic molecules, the long-range interaction between organic molecules and the substrate, as well as the soft matter characteristics of ultrathin films. The growth behavior and soft matter characteristics of the thin-film phase have great effects on thin film morphology and structure, for example, the formation and coalescence of grain boundaries, which further influences the performance of organic electronic devices. The understanding of thin-film phase and its intrinsic quality is necessary for fabricating large-size, highly ordered, continuous and defect-free ultrathin films. This review will focus on the growth behavior of organic ultrathin films, i.e., the level of the first several molecular layers, and provide an overview of the soft matter characteristics.

  1. Crystallization of Organic Semiconductor Molecules in Nanosized Cavities

    DEFF Research Database (Denmark)

    Milita, Silvia; Dionigi, Chiara; Borgatti, Francesco

    2008-01-01

    evaporation. Thanks to these real time experiments, the phase content and the crystalline domain orientation of H4T6 have been determined, from the onset of the first crystalline molecular assembly to the stable system. The correlation between the bead size dependent crystallization mechanism in this complex......The crystallization of an organic semiconductor, viz., tetrahexil-sexithiophene (H4T6) molecules, confined into nanosized cavities of a self-organized polystyrene beads template, has been investigated by means of in situ grazing incidence X-ray diffraction measurements, during the solvent...

  2. Charge transport in nanoscale vertical organic semiconductor pillar devices

    Science.gov (United States)

    Wilbers, Janine G. E.; Xu, Bojian; Bobbert, Peter A.; de Jong, Michel P.; van der Wiel, Wilfred G.

    2017-01-01

    We report charge transport measurements in nanoscale vertical pillar structures incorporating ultrathin layers of the organic semiconductor poly(3-hexylthiophene) (P3HT). P3HT layers with thickness down to 5 nm are gently top-contacted using wedging transfer, yielding highly reproducible, robust nanoscale junctions carrying high current densities (up to 106 A/m2). Current-voltage data modeling demonstrates excellent hole injection. This work opens up the pathway towards nanoscale, ultrashort-channel organic transistors for high-frequency and high-current-density operation.

  3. Theory for Spin Diffusion in Disordered Organic Semiconductors

    Science.gov (United States)

    Bobbert, P. A.; Wagemans, W.; van Oost, F. W. A.; Koopmans, B.; Wohlgenannt, M.

    2009-04-01

    We present a theory for spin diffusion in disordered organic semiconductors, based on incoherent hopping of a charge carrier and coherent precession of its spin in an effective magnetic field, composed of the random hyperfine field of hydrogen nuclei and an applied magnetic field. From Monte Carlo simulations and an analysis of the waiting-time distribution of the carrier we predict a surprisingly weak temperature dependence, but a considerable magnetic-field dependence of the spin-diffusion length. We show that both predictions are in agreement with experiments on organic spin valves.

  4. SEMICONDUCTOR DEVICES: Humidity sensitive organic field effect transistor

    Science.gov (United States)

    Murtaza, I.; Karimov, Kh S.; Ahmad, Zubair; Qazi, I.; Mahroof-Tahir, M.; Khan, T. A.; Amin, T.

    2010-05-01

    This paper reports the experimental results for the humidity dependent properties of an organic field effect transistor. The organic field effect transistor was fabricated on thoroughly cleaned glass substrate, in which the junction between the metal gate and the organic channel plays the role of gate dielectric. Thin films of organic semiconductor copper phthalocynanine (CuPc) and semitransparent Al were deposited in sequence by vacuum thermal evaporation on the glass substrate with preliminarily deposited Ag source and drain electrodes. The output and transfer characteristics of the fabricated device were performed. The effect of humidity on the drain current, drain current-drain voltage relationship, and threshold voltage was investigated. It was observed that humidity has a strong effect on the characteristics of the organic field effect transistor.

  5. Physics of organic semiconductors. 2. compl. new rev. ed.

    Energy Technology Data Exchange (ETDEWEB)

    Bruetting, Wolfgang [Augsburg Univ. (Germany). Inst. fuer Physik; Adachi, Chihaya (eds.) [Kyushu Univ., Fukuoka (Japan). Center for Future Chemistry

    2012-07-01

    The field of organic electronics has seen a steady growth over the last 15 years. At the same time, our scientific understanding of how to achieve optimum device performance has grown, and this book gives an overview of our present-day knowledge of the physics behind organic semiconductor devices. Based on the very successful first edition, the editors have invited top scientists from the US, Japan, and Europe to include the developments from recent years, covering such fundamental issues as: - growth and characterization of thin films of organic semiconductors, - charge transport and photophysical properties of the materials as well as their electronic structure at interfaces, and - analysis and modeling of devices like organic light-emitting diodes or organic lasers. The result is an overview of the field for both readers with basic knowledge and for an application-oriented audience. It thus bridges the gap between textbook knowledge largely based on crystalline molecular solids and those books focusing more on device applications.

  6. Template fabrication of highly ordered arrays of organic semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Heckel, Christian; Ostendorp, Stefan; Lei, Yong; Wilde, Gerhard [Institut fuer Materialphysik, Muenster (Germany)

    2011-07-01

    Porous alumina membrane (PAM) is a widely used template for the fabrication of highly ordered arrays of one-dimensional (1D) nanostructures. The structural parameters of the PAMs are adjustable, including the pore diameter and spacing, and the thickness of the membranes. And thus the structures of the 1D nanomaterials prepared using PAMs can be controlled. On the other hand, the investigation of organic semiconductors opens a new field of applications in computer technology like twistable displays or printing integrated circuits. In the current work, these two technologies are combined by depositing organic n-type semiconductors into the pores of PAMs using different synthesizing processes such as molecular evaporation and solution-phase self-assembly. As a result, highly ordered arrays of organic semiconducting wires are obtained within the pores with a diameter of about 50 nm, which indicates that it is possible to fill the pores with organic materials.The properties of these ''filled'' membranes are characterized by measuring the electrical properties of several nanowires pooled together and also of single nanowires by AFM-based methods.

  7. Strain effects on the work function of an organic semiconductor

    KAUST Repository

    Wu, Yanfei

    2016-02-01

    Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density functional theory calculations. An elastic-to-plastic transition, characterized by a steep rise of the WF, occurs at ~0.05% tensile strain along the rubrene π-stacking direction. The results provide the first concrete link between mechanical strain and WF of an organic semiconductor and have important implications for understanding the connection between structural and electronic disorder in soft organic electronic materials.

  8. Emission characteristics of volatile organic compounds from semiconductor manufacturing.

    Science.gov (United States)

    Chein, HungMin; Chen, Tzu Ming

    2003-08-01

    A huge amount of volatile organic compounds (VOCs) is produced and emitted with waste gases from semiconductor manufacturing processes, such as cleaning, etching, and developing. VOC emissions from semiconductor factories located at Science-Based Industrial Park, Hsin-chu, Taiwan, were measured and characterized in this study. A total of nine typical semiconductor fabricators (fabs) were monitored over a 12-month period (October 2000-September 2001). A flame ionization analyzer was employed to measure the VOC emission rate continuously in a real-time fashion. The amount of chemical use was adopted from the data that were reported to the Environmental Protection Bureau in Hsin-chu County as per the regulation of the Taiwan Environmental Protection Administration. The VOC emission factor, defined as the emission rate (kg/month) divided by the amount of chemical use (L/month), was determined to be 0.038 +/- 0.016 kg/L. A linear regression equation is proposed to fit the data with the correlation coefficient (R2)=0.863. The emission profiles of VOCs, which were drawn using the gas chromatograph/mass spectrometer analysis method, show that isopropyl alcohol is the dominant compound in most of the fabs.

  9. Self-interaction and charge transfer in organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Koerzdoerfer, Thomas

    2009-12-18

    This work concentrates on the problem of self-interaction, which is one of the most serious problems of commonly used approximative density functionals. As a major result of this work, it is demonstrated that self-interaction plays a decisive role for the performance of different approximative functionals in predicting accurate electronic properties of organic molecular semiconductors. In search for a solution to the self-interaction problem, a new concept for correcting commonly used density functionals for self-interaction is introduced and applied to a variety of systems, spanning small molecules, extended molecular chains, and organic molecular semiconductors. It is further shown that the performance of functionals that are not free from self-interaction can vary strongly for different systems and observables of interest, thus entailing the danger of misinterpretation of the results obtained from those functionals. The underlying reasons for the varying performance of commonly used density functionals are discussed thoroughly in this work. Finally, this thesis provides strategies that allow to analyze the reliability of commonly used approximations to the exchange-correlation functional for particular systems of interest. This cumulative dissertation is divided into three parts. Part I gives a short introduction into DFT and its time-dependent extension (TDDFT). Part II provides further insights into the self-interaction problem, presents a newly developed concept for the correction of self-interaction, gives an introduction into the publications, and discusses their basic results. Finally, the four publications on self-interaction and charge-transfer in extended molecular systems and organic molecular semiconductors are collected in Part III. (orig.)

  10. Universal size-dependent conductance fluctuations in disordered organic semiconductors.

    Science.gov (United States)

    Massé, A; Coehoorn, R; Bobbert, P A

    2014-09-12

    Numerically exact results of hopping charge transport in disordered organic semiconductors show for uncorrelated and dipole-correlated Gaussian energy disorder a universal, power-law, and non-power-law dependence, respectively, of the relative conductance fluctuations on the size of the considered region. Data collapse occurs upon scaling with a characteristic length having a power-law temperature dependence. Below this length, which can be as high as 100 nm for correlated disorder in a realistic case, fluctuations dominate and a continuum description of charge transport breaks down.

  11. Universal Size-Dependent Conductance Fluctuations in Disordered Organic Semiconductors

    Science.gov (United States)

    Massé, A.; Coehoorn, R.; Bobbert, P. A.

    2014-09-01

    Numerically exact results of hopping charge transport in disordered organic semiconductors show for uncorrelated and dipole-correlated Gaussian energy disorder a universal, power-law, and non-power-law dependence, respectively, of the relative conductance fluctuations on the size of the considered region. Data collapse occurs upon scaling with a characteristic length having a power-law temperature dependence. Below this length, which can be as high as 100 nm for correlated disorder in a realistic case, fluctuations dominate and a continuum description of charge transport breaks down.

  12. Organic semiconductor heterojunction and its application in organic light-emitting diodes (Conference Presentation)

    Science.gov (United States)

    Ma, Dongge

    2016-09-01

    Organic light-emitting diodes (OLEDs) have drawn increasing attention as the next generation displays and lighting sources. High efficiency and long lifetime are necessary for OLEDs in practical applications. In conventional OLEDs, the charge carriers are directly injected into the organic transport layers from electrodes, the injection barriers between the organic transport layers and electrodes are unavoidable due to the mismatch between the work function of metal electrode and the energy level of charge-transport layer, which greatly affects the performance of fabricated OLEDs. Furthermore, tandem OLEDs, which are fabricated by vertically connecting several individual electroluminescent (EL) units together in series via an appropriate charge generation layer (CGL) with the entire device driven by a single power source can significantly enhance current efficiency and stability, but their performance is strongly dependent on the used CGL, especially the power efficiency is difficult to enhance due to the increase of working voltage. Recently we found that organic semiconductor heterojunctions show efficient charge generation effect and as CGL, not only double the luminance and current efficiency, but also greatly improve the power efficiency, which is difficult in tandem OLEDs based on conventional CGLs. We also realized electrode-independent charge injection by using organic semiconductor heterojuncrions as injectors in OLEDs, and obtained comparable electroluminescent (EL) performance with that of conventional OLEDs. Here, we report the results of tandem OLEDs based on organic semiconductor heterojunctions as CGL and OLEDs using organic semiconductor heterojunctions as injectors, and discuss this working mechanism in detail.

  13. Theoretically Rational Designs of Transport Organic Semiconductors Based on Heteroacenes

    Institute of Scientific and Technical Information of China (English)

    HE,Yuan-Hang; HUI,Ren-Jie; YI,Yuan-Ping; SHUAI,Zhi-Gang

    2008-01-01

    A Marcus electron transfer theory coupled with an incoherent polaron hopping and charge diffusion model in combining with first-principle quantum chemistry calculation was applied to investigating the effects of heteroatom on the intermolecular charge transfer rate for a seres of heteroacene molecules.The influences of intermolecular packing and charge reorganization energy were discussed.It was found that the sulphur and nitrogen substituted heteroacenes were intrinsically hole-transporting materials due to the reduced hole reorganization energy and the enhanced overlap between HOMOs.For the oxygen-substituted heteroacene,it was found that both the electronic couplings and the reorganization energies for holes and electrons were comparative,indicating the application potential of ambipolar devices.Most interestingly,for the boron-substituted heteroacenes,theoretical calculations predicted a promising electron-transport material,which is rare for organic materials.These findings provide insights into rationally designing organic semiconductors with specific properties.

  14. Directional charge separation in isolated organic semiconductor crystalline nanowires

    Science.gov (United States)

    Labastide, J. A.; Thompson, H. B.; Marques, S. R.; Colella, N. S.; Briseno, A. L.; Barnes, M. D.

    2016-02-01

    One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized along the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry.

  15. Structural and electronic implications for carrier injection into organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Castellani, Mauro [Universitaet Potsdam, Institut fuer Physik und Astronomie, Potsdam-Golm (Germany); Salzmann, Ingo; Yu, Shuwen; Koch, Norbert [Humboldt-Universitaet zu Berlin, Institut fuer Physik, Berlin (Germany); Bugnon, Philippe [Ecole Polytechnique Federale de Lausanne (Switzerland). Institut des Materiaux; Oehzelt, Martin [Johannes Kepler Universitaet Linz (Austria). Institut fuer Experimentalphysik

    2009-10-15

    We report on the structural and electronic interface formation between ITO (indium-tin-oxide) and prototypical organic small molecular semiconductors, i.e., CuPc (copper phthalocyanine) and {alpha}-NPD (N,N'-di(naphtalen-1-yl)-N,N'-diphenyl-benzidine). In particular, the effects of in situ oxygen plasma pretreatment of the ITO surface on interface properties are examined in detail: Organic layer-thickness dependent Kelvin probe measurements revealed a good alignment of the ITO work function and the highest occupied electronic level of the organic material in all samples. In contrast, the electrical properties of hole-only and bipolar organic diodes depend strongly on the treatment of ITO prior to organic deposition. This dependence is more pronounced for diodes made of polycrystalline CuPc than for those of amorphous {alpha}-NPD layers. X-ray diffraction and atomic force microscopic (AFM) investigations of CuPc nucleation and growth evidenced a more pronounced texture of the polycrystalline film structure on the ITO substrate that was oxygen plasma treated prior to organic layer deposition. These findings suggest that the anisotropic electrical properties of CuPc crystallites, and their orientation with respect to the substrate, strongly affect the charge carrier injection and transport properties at the anode interface. (orig.)

  16. Flexible non-volatile memory devices based on organic semiconductors

    Science.gov (United States)

    Cosseddu, Piero; Casula, Giulia; Lai, Stefano; Bonfiglio, Annalisa

    2015-09-01

    The possibility of developing fully organic electronic circuits is critically dependent on the ability to realize a full set of electronic functionalities based on organic devices. In order to complete the scene, a fundamental element is still missing, i.e. reliable data storage. Over the past few years, a considerable effort has been spent on the development and optimization of organic polymer based memory elements. Among several possible solutions, transistor-based memories and resistive switching-based memories are attracting a great interest in the scientific community. In this paper, a route for the fabrication of organic semiconductor-based memory devices with performances beyond the state of the art is reported. Both the families of organic memories will be considered. A flexible resistive memory based on a novel combination of materials is presented. In particular, high retention time in ambient conditions are reported. Complementary, a low voltage transistor-based memory is presented. Low voltage operation is allowed by an hybrid, nano-sized dielectric, which is also responsible for the memory effect in the device. Thanks to the possibility of reproducibly fabricating such device on ultra-thin substrates, high mechanical stability is reported.

  17. Organic Semiconductors based on Dyes and Color Pigments.

    Science.gov (United States)

    Gsänger, Marcel; Bialas, David; Huang, Lizhen; Stolte, Matthias; Würthner, Frank

    2016-05-01

    Organic dyes and pigments constitute a large class of industrial products. The utilization of these compounds in the field of organic electronics is reviewed with particular emphasis on organic field-effect transistors. It is shown that for most major classes of industrial dyes and pigments, i.e., phthalocyanines, perylene and naphthalene diimides, diketopyrrolopyrroles, indigos and isoindigos, squaraines, and merocyanines, charge-carrier mobilities exceeding 1 cm(2) V(-1) s(-1) have been achieved. The most widely investigated molecules due to their n-channel operation are perylene and naphthalene diimides, for which even values close to 10 cm(2) V(-1) s(-1) have been demonstrated. The fact that all of these π-conjugated colorants contain polar substituents leading to strongly quadrupolar or even dipolar molecules suggests that indeed a much larger structural space shows promise for the design of organic semiconductor molecules than was considered in this field traditionally. In particular, because many of these dye and pigment chromophores demonstrate excellent thermal and (photo-)chemical stability in their original applications in dyeing and printing, and are accessible by straightforward synthetic protocols, they bear a particularly high potential for commercial applications in the area of organic electronics.

  18. Centro-Apical Self-Organization of Organic Semiconductors in a Line-Printed Organic Semiconductor: Polymer Blend for One-Step Printing Fabrication of Organic Field-Effect Transistors.

    Science.gov (United States)

    Lee, Su Jin; Kim, Yong-Jae; Yeo, So Young; Lee, Eunji; Lim, Ho Sun; Kim, Min; Song, Yong-Won; Cho, Jinhan; Lim, Jung Ah

    2015-09-11

    Here we report the first demonstration for centro-apical self-organization of organic semiconductors in a line-printed organic semiconductor: polymer blend. Key feature of this work is that organic semiconductor molecules were vertically segregated on top of the polymer phase and simultaneously crystallized at the center of the printed line pattern after solvent evaporation without an additive process. The thickness and width of the centro-apically segregated organic semiconductor crystalline stripe in the printed blend pattern were controlled by varying the relative content of the organic semiconductors, printing speed, and solution concentrations. The centro-apical self-organization of organic semiconductor molecules in a printed polymer blend may be attributed to the combination of an energetically favorable vertical phase-separation and hydrodynamic fluids inside the droplet during solvent evaporation. Finally, a centro-apically phase-separated bilayer structure of organic semiconductor: polymer blend was successfully demonstrated as a facile method to form the semiconductor and dielectric layer for OFETs in one- step.

  19. Comprehensive mass spectrometric analysis of novel organic semiconductor molecules

    Science.gov (United States)

    Prada, Svitlana

    This work presents a comprehensive mass spectrometry (MS) study of novel organic semiconductor molecules including ion mobility/reactivity measurements and trace elemental analysis. The organic molecules investigated here are important semiconductor materials for molecular electronic devices such as Organic Field-Effect Transistors (OFETs) and Light Emitted Diodes (LED). A high-performance orthogonal time-of flight mass spectrometer (TOF-MS) in combination with a matrix assisted laser desorption/ionization (MALDI) source operating at elevated pressure was used to perform MALDI/TOF analyses of pentacene and some of its derivatives with and without an added matrix. The observation of ion-molecule reactions between "cold" analyte ions and neutral analyte molecules in the gas phase has provided some insight into the mechanism of pentacene cluster formation and its functionalized derivatives. Furthermore, some of the matrices employed to assist the desorption/ionization process of these compounds were observed to influence the outcome via ion-molecule reactions of analyte ions and matrix molecules in the gas phase. The stability and reactivity of the compounds and their clusters in the MALDI plume during gas-phase expansion were evaluated; possible structures of the resulting clusters are discussed. The MALDI/TOF technique was also helpful in distinguishing between two isomeric forms of bis-[(triisopropylsilyl)-ethynyl]-pentacene. Furthermore, we reported ion mobility measurements of functionalized pentacene ions with a modified triple quadrupole mass spectrometer fitted with an ion molecule reactor (IMR). The IMR is equipped with a variable axial electrostatic drift field (ADF) and is able to trap ions for a prolong period of time. These capabilities were successfully employed in the measurement of ion mobilities in different modes of the IMR operation. Theoretical modeling of the drift dynamics and the special localization of the large ion packet was successfully

  20. Pressure Dependent Electronic Properties of Organic Semiconductors from First Principles

    Science.gov (United States)

    Knuth, Franz; Carbogno, Christian; Blum, Volker; Scheffler, Matthias

    2015-03-01

    The electronic properties of organic semiconductors typically exhibit a significant dependence on the strain, stress, and pressure. In this contribution, we present the theoretical background, assessment of approximations, and results of electronic and transport properties in the framework of density-functional theory. Our implementation considers the analytical strain derivatives (stress tensor) including the contributions that stem from (a) van-der-Waals interactions and (b) the Fock-exchange in hybrid functionals. We validate our approach by investigating the geometric and electronic changes that occur in polyacetylene and anthracene under hydrostatic pressure. We show that the fraction of exact exchange included in the calculations is critical - and non-trivial to choose - for a correct description of these systems. Furthermore, we point out trends for the electrical conductivity under pressure and identify the dominant charge carriers and transport directions.

  1. Potential-Dependent Generalized Einstein Relation in Disordered Organic Semiconductors

    Institute of Scientific and Technical Information of China (English)

    LU Xiao-Hong; SUN Jiu-Xun; GUO Yang; ZHANG Da

    2009-01-01

    The generalized Einstein relation (GER) is extended to consider the potential energy of carriers in an electric field (PDGER).It can be equivalently seen as the GER having position-dependent Fermi energy,and implies the organic semiconductor is in non-equilibrium under an electric field.The distribution of the carrier density with position is solved for two polymer layers.The numerical results are used to evaluate the PDGER.It is shown that the ratio of diffusion coefficient to mobility,μ/D,increases with Fermi energy and decreases with carrier density.The PDGER gives non-traditional values for the two polymer layers;the value of μ/D is small near the surface,and slightly increases as the position departs from the surface.

  2. Nonequilibrium drift-diffusion model for organic semiconductor devices

    Science.gov (United States)

    Felekidis, Nikolaos; Melianas, Armantas; Kemerink, Martijn

    2016-07-01

    Two prevailing formalisms are currently used to model charge transport in organic semiconductor devices. Drift-diffusion calculations, on the one hand, are time effective but assume local thermodynamic equilibrium, which is not always realistic. Kinetic Monte Carlo models, on the other hand, do not require this assumption but are computationally expensive. Here, we present a nonequilibrium drift-diffusion model that bridges this gap by fusing the established multiple trap and release formalism with the drift-diffusion transport equation. For a prototypical photovoltaic system the model is shown to quantitatively describe, with a single set of parameters, experiments probing (1) temperature-dependent steady-state charge transport—space-charge limited currents, and (2) time-resolved charge transport and relaxation of nonequilibrated photocreated charges. Moreover, the outputs of the developed kinetic drift-diffusion model are an order of magnitude, or more, faster to compute and in good agreement with kinetic Monte Carlo calculations.

  3. Effective Temperature and Universal Conductivity Scaling in Organic Semiconductors

    Science.gov (United States)

    Abdalla, Hassan; van de Ruit, Kevin; Kemerink, Martijn

    2015-11-01

    We investigate the scalability of the temperature- and electric field-dependence of the conductivity of disordered organic semiconductors to ‘universal’ curves by two different but commonly employed methods; by so-called universal scaling and by using the effective temperature concept. Experimentally both scaling methods were found to be equally applicable to the out-of-plane charge transport in PEDOT:PSS thin films of various compositions. Both methods are shown to be equivalent in terms of functional dependence and to have identical limiting behavior. The experimentally observed scaling behavior can be reproduced by a numerical nearest-neighbor hopping model, accounting for the Coulomb interaction, the high charge carrier concentration and the energetic disorder. The underlying physics can be captured in a simple empirical model, describing the effective temperature of the charge carrier distribution as the outcome of a heat balance between Joule heating and (effective) temperature-dependent energy loss to the lattice.

  4. Organic Spin-Valves and Beyond: Spin Injection and Transport in Organic Semiconductors and the Effect of Interfacial Engineering.

    Science.gov (United States)

    Jang, Hyuk-Jae; Richter, Curt A

    2017-01-01

    Since the first observation of the spin-valve effect through organic semiconductors, efforts to realize novel spintronic technologies based on organic semiconductors have been rapidly growing. However, a complete understanding of spin-polarized carrier injection and transport in organic semiconductors is still lacking and under debate. For example, there is still no clear understanding of major spin-flip mechanisms in organic semiconductors and the role of hybrid metal-organic interfaces in spin injection. Recent findings suggest that organic single crystals can provide spin-transport media with much less structural disorder relative to organic thin films, thus reducing momentum scattering. Additionally, modification of the band energetics, morphology, and even spin magnetic moment at the metal-organic interface by interface engineering can greatly impact the efficiency of spin-polarized carrier injection. Here, progress on efficient spin-polarized carrier injection into organic semiconductors from ferromagnetic metals by using various interface engineering techniques is presented, such as inserting a metallic interlayer, a molecular self-assembled monolayer (SAM), and a ballistic carrier emitter. In addition, efforts to realize long spin transport in single-crystalline organic semiconductors are discussed. The focus here is on understanding and maximizing spin-polarized carrier injection and transport in organic semiconductors and insight is provided for the realization of emerging organic spintronics technologies.

  5. Universal arrhenius temperature activated charge transport in diodes from disordered organic semiconductors

    NARCIS (Netherlands)

    Craciun, N. I.; Wildeman, J.; Blom, P. W. M.

    2008-01-01

    Charge transport models developed for disordered organic semiconductors predict a non-Arrhenius temperature dependence ln(mu) proportional to 1/T(2) for the mobility mu. We demonstrate that in space-charge limited diodes the hole mobility (mu(h)) of a large variety of organic semiconductors shows a

  6. Effect of Electric Field on Spin Polarized Current in Ferromagnetic/ Organic Semiconductor Systems

    Institute of Scientific and Technical Information of China (English)

    MA Yan-Ni; REN Jun-Feng; ZHANG Yu-Bin; LIU De-Sheng; XIE Shi-Jie

    2007-01-01

    Considering the special carriers in organic semiconductors, the spin polarized current under electric field in a ferromagnetic/organic semiconductor system is theoretically studied. Based on the spin-diffusion theory, the current spin polarization under the electric field is obtained. It is found that electric field can enhance the current spin polarization.

  7. Universal arrhenius temperature activated charge transport in diodes from disordered organic semiconductors

    NARCIS (Netherlands)

    Craciun, N. I.; Wildeman, J.; Blom, P. W. M.

    2008-01-01

    Charge transport models developed for disordered organic semiconductors predict a non-Arrhenius temperature dependence ln(mu) proportional to 1/T(2) for the mobility mu. We demonstrate that in space-charge limited diodes the hole mobility (mu(h)) of a large variety of organic semiconductors shows a

  8. Room temperature triplet state spectroscopy of organic semiconductors.

    Science.gov (United States)

    Reineke, Sebastian; Baldo, Marc A

    2014-01-21

    Organic light-emitting devices and solar cells are devices that create, manipulate, and convert excited states in organic semiconductors. It is crucial to characterize these excited states, or excitons, to optimize device performance in applications like displays and solar energy harvesting. This is complicated if the excited state is a triplet because the electronic transition is 'dark' with a vanishing oscillator strength. As a consequence, triplet state spectroscopy must usually be performed at cryogenic temperatures to reduce competition from non-radiative rates. Here, we control non-radiative rates by engineering a solid-state host matrix containing the target molecule, allowing the observation of phosphorescence at room temperature and alleviating constraints of cryogenic experiments. We test these techniques on a wide range of materials with functionalities spanning multi-exciton generation (singlet exciton fission), organic light emitting device host materials, and thermally activated delayed fluorescence type emitters. Control of non-radiative modes in the matrix surrounding a target molecule may also have broader applications in light-emitting and photovoltaic devices.

  9. Functional p-Type, Polymerized Organic Electrode Interlayer in CH₃NH₃PbI₃ Perovskite/Fullerene Planar Heterojunction Hybrid Solar Cells.

    Science.gov (United States)

    Chiang, Tsung-Yu; Fan, Gang-Lun; Jeng, Jun-Yuan; Chen, Kuo-Cheng; Chen, Peter; Wen, Ten-Chin; Guo, Tzung-Fang; Wong, Ken-Tsung

    2015-11-11

    Thermal curing of the styrene-functionalized 9,9-diarylfluorene-based triaryldiamine monomer (VB-DAAF) forms an ideal p-type organic electrode interlayer capable of resisting solvation of the polar precursor solution in fabricating methylammonium lead iodide (CH3NH3PbI3) perovskite/fullerene (C60) planar heterojunction hybrid solar cells. The polymerized VB-DAAF film exhibits a good energy level alignment with the valence-band-edge level of the CH3NH3PbI3 perovskite to facilitate the transport of holes. The large energy barrier to the conduction-band-edge level of the CH3NH3PbI3 perovskite effectively blocks electrons from reaching the positive electrode and reduces the photon energy loss due to recombination. The best-performing cell with the configuration of glass/indium-tin oxide/polymerized VB-DAAF/CH3NH3PbI3 perovskite/C60/bathocuproine/aluminum is free of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) layer to achieve an open-circuit voltage (VOC) = 1.02 V, a short-circuit current (JSC) = 18.92 mA/cm(2), and a fill factor (FF) = 0.78, corresponding to a power conversion efficiency (PCE) of 15.17% under standard 1 sun AM 1.5G simulated solar irradiation. The performance is much superior to the device applying the PSS interlayer with photovoltaic parameters of VOC = 0.85 V, JSC = 16.37 mA/cm(2), and FF = 0.74, corresponding to a PCE of 10.27%. Additionally, we had applied a UV-assisted process to polymerize the VB-DAAF film at relatively lower temperature and fabricate decent perovskite-based solar cells on the flexible substrate for real applications.

  10. Theory aided design and analysis of dielectric and semiconductor components for organic field-effect transistors

    Science.gov (United States)

    Dibenedetto, Sara Arlene

    Perfluoroacyl/acyl-derivatized quaterthiophens are developed and synthesized. The frontier molecular orbital energies of these compounds are studied by optical spectroscopy and electrochemistry while solid-state/film properties are investigated by thermal analysis, x-ray diffraction, and scanning electron microscopy. Organic thin film transistors (OTFTs) performance parameters are discussed in terms of the interplay between semiconductor molecular energetics and film morphologies/microstructures. The majority charge carrier type and mobility exhibit a strong correlation with the regiochemistry of perfluoroarene incorporation. In quaterthiophene-based semiconductors, carbonyl-functionalization allows tuning of the majority carrier type from p-type to ambipolar and to n-type. In situ conversion of a p-type semiconducting film to n-type film is also demonstrated. The design of chemical and film microstructural alternative hybrid organic-inorganic gate dielectrics is described using the classic Clausius-Mossotti relation. The Maxwell-Wagner effective medium model is used to compute the effective dielectric permittivity of two types of dielectrics self-assembled nanodielectrics (SANDs) and crosslinked polymer blends (CPBs). In these calculations showing good agreement between theory and experiment, it is found that greater capacitances should be achievable with mixed composites than with layered composites. With this insight, a series of mixed metal oxide-polyolefin nanocomposites is synthesized via in-situ olefin polymerization using the single-site metallocene catalysts. By integrating organic and inorganic constituents, the resulting hybrid material exhibit high permittivity (from the inorganic inclusions) and high breakdown strength, mechanical flexibility, and facile processability (from the polymer matrices). In order to better optimize the capacitance and leakage current of hybrid organic-inorganic dielectrics, the capacitance, leakage current and OFET gate

  11. Organic semiconductor nickel phthalocyanine-based photocapacitive and photoresistive detector

    Science.gov (United States)

    Shah, Mutabar; Karimov, Kh S.; Sayyad, M. H.

    2010-07-01

    In this study, the photosensitive organic semiconductor nickel phthalocyanine (NiPc) is investigated as a photocapacitive and photoresistive detector. NiPc thin film is grown by vacuum thermal evaporation on an indium tin oxide (ITO)-coated glass substrate. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is deposited as a top electrode by drop-casting to fabricate the ITO/NiPc/PEDOT:PSS light detector. It has been observed that under the unmodulated filament lamp illumination of up to 9720 lux the capacitance of the detectors increased up to 21, 18 and 4% at a frequency of measuring voltage of 120 Hz, 1 kHz and 10 kHz, respectively, under dark conditions. The change in resistance with the variation in the intensity of light is also investigated. The capacitance and resistance of the light detector decrease with an increase in the frequency. It is assumed that the photocapacitive and photoresistive response of the detector is associated with polarization occurring due to the transfer of photo-generated electrons and holes. The calculated results are in reasonable agreement with the experimental results.

  12. Small molecule semiconductors for high-efficiency organic photovoltaics.

    Science.gov (United States)

    Lin, Yuze; Li, Yongfang; Zhan, Xiaowei

    2012-06-01

    Organic photovoltaic cells (OPVs) are a promising cost-effective alternative to silicon-based solar cells, and possess light-weight, low-cost, and flexibility advantages. Significant progress has been achieved in the development of novel photovoltaic materials and device structures in the last decade. Nowadays small molecular semiconductors for OPVs have attracted considerable attention, due to their advantages over their polymer counterparts, including well-defined molecular structure, definite molecular weight, and high purity without batch to batch variations. The highest power conversion efficiencies of OPVs based on small molecular donor/fullerene acceptors or polymeric donor/fullerene acceptors are up to 6.7% and 8.3%, respectively, and meanwhile nonfullerene acceptors have also exhibited some promising results. In this review we summarize the developments in small molecular donors, acceptors (fullerene derivatives and nonfullerene molecules), and donor-acceptor dyad systems for high-performance multilayer, bulk heterojunction, and single-component OPVs. We focus on correlations of molecular chemical structures with properties, such as absorption, energy levels, charge mobilities, and photovoltaic performances. This structure-property relationship analysis may guide rational structural design and evaluation of photovoltaic materials (253 references).

  13. Preparations and Characterizations of Luminescent Two Dimensional Organic-inorganic Perovskite Semiconductors

    Directory of Open Access Journals (Sweden)

    Sanjun Zhang

    2010-05-01

    Full Text Available This article reviews the synthesis, structural and optical characterizations of some novel luminescent two dimensional organic-inorganic perovskite (2DOIP semiconductors. These 2DOIP semiconductors show a self-assembled nano-layered structure, having the electronic structure of multi-quantum wells. 2DOIP thin layers and nanoparticles have been prepared through different methods. The structures of the 2DOIP semiconductors are characterized by atomic force microscopy and X-ray diffraction. The optical properties of theb DOIP semiconductors are characterized from absorption and photoluminescence spectra measured at room and low temperatures. Influences of different components, in particular the organic parts, on the structural and optical properties of the 2DOIP semiconductors are discussed.

  14. Controlled Growth of Ultrathin Film of Organic Semiconductors by Balancing the Competitive Processes in Dip-Coating for Organic Transistors.

    Science.gov (United States)

    Wu, Kunjie; Li, Hongwei; Li, Liqiang; Zhang, Suna; Chen, Xiaosong; Xu, Zeyang; Zhang, Xi; Hu, Wenping; Chi, Lifeng; Gao, Xike; Meng, Yancheng

    2016-06-28

    Ultrathin film with thickness below 15 nm of organic semiconductors provides excellent platform for some fundamental research and practical applications in the field of organic electronics. However, it is quite challenging to develop a general principle for the growth of uniform and continuous ultrathin film over large area. Dip-coating is a useful technique to prepare diverse structures of organic semiconductors, but the assembly of organic semiconductors in dip-coating is quite complicated, and there are no reports about the core rules for the growth of ultrathin film via dip-coating until now. In this work, we develop a general strategy for the growth of ultrathin film of organic semiconductor via dip-coating, which provides a relatively facile model to analyze the growth behavior. The balance between the three direct factors (nucleation rate, assembly rate, and recession rate) is the key to determine the growth of ultrathin film. Under the direction of this rule, ultrathin films of four organic semiconductors are obtained. The field-effect transistors constructed on the ultrathin film show good field-effect property. This work provides a general principle and systematic guideline to prepare ultrathin film of organic semiconductors via dip-coating, which would be highly meaningful for organic electronics as well as for the assembly of other materials via solution processes.

  15. Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang [Columbia Univ., New York, NY (United States); Frisbie, Daniel [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-03-31

    The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

  16. Organic functionalization of group IV semiconductor surfaces: principles, examples, applications, and prospects

    Science.gov (United States)

    Bent, Stacey F.

    2002-03-01

    Organic functionalization is emerging as an important area in the development of new semiconductor-based materials and devices. Direct, covalent attachment of organic layers to a semiconductor interface provides for the incorporation of many new properties, including lubrication, optical response, chemical sensing, or biocompatibility. Methods by which to incorporate organic functionality to the surfaces of semiconductors have seen immense progress in recent years, and in this article several of these approaches are reviewed. Examples are included from both dry and wet processing environments. The focus of the article is on attachment strategies that demonstrate the molecular nature of the semiconductor surface. In many cases, the surfaces mimic the reactivity of their molecular carbon or organosilane counterparts, and examples of functionalization reactions are described in which direct analogies to textbook organic and inorganic chemistry can be applied. This article addresses the expected impact of these functionalization strategies on emerging technologies in nanotechnology, sensing, and bioengineering.

  17. Understanding electrical-thermal transport characteristics of organic semiconductors: Violation of Wiedemann-Franz law

    Science.gov (United States)

    Lu, Nianduan; Li, Ling; Gao, Nan; Liu, Ming

    2016-11-01

    Organic semiconductors exhibit plenty of attractive properties for use as thermoelectric elements. A comprehensive understanding for the electrical-thermal transport characteristics is crucial to design and fabricate the thermoelectric device. We proposed a theoretical model to investigate the electrical conductivity and the electronic thermal conductivity of organic semiconductors based on the hopping transport mechanism. The electrical-thermal transport characteristics of organic semiconductors have been analyzed in detail and compared with the experimental results and Monte Carlo simulation. The Wiedemann-Franz law, connecting the electronic thermal conductivity to the electrical conductivity of organic semiconductors, is generally found to be strongly violated under the effect of temperature, carrier concentration, energetic disorder and electric field.

  18. Nanoscale contacts to organic molecules based on layered semiconductor substrates

    Energy Technology Data Exchange (ETDEWEB)

    Strobel, Sebastian

    2009-06-15

    This work reports on the integration of organic molecules as nanoelectronic device units on semiconductor substrates. Two novel preparation methods for sub-10-nm separated metal electrodes are presented using current microelectronics process technology. The first method utilises AlGaAs/GaAs heterostructures grown by molecular beam epitaxy (MBE) as mold to create planar metal electrodes employing a newly developed, high resolution nanotransfer printing (nTP) process. The second method uses commercially available Silicon-on-Insulator (SOI) substrates as base material for the fabrication of nanogap electrode devices. This sandwich-like material stack consists of a silicon substrate, a thin silicon oxide layer, and a capping silicon layer on top. Electronic transport measurements verified their excellent electrical properties at liquid helium temperatures. Specifically tailored nanogap devices featured an electrode insulation in the GW range even up to room temperature as well as within aqueous electrolyte solution. Finally, the well defined layer architecture facilitated the fabrication of electrodes with gap separations below-10-nm to be directly bridged by molecules. Approximately 12-nm-long conjugated molecules with extended -electron system were assembled onto the devices from solution. A large conductance gap was observed with a steep increase in current at a bias voltage of V{sub T}{approx}{+-}1.5 V. Theoretical calculations based on density functional theory and non-equilibrium Green's function formalism confirmed the measured non-linear IV-characteristics qualitatively and lead to the conclusion that the conductance gap mainly originates from the oxygen containing linker. Temperature dependent investigations of the conductance indicated a hopping charge transport mechanism through the central part of the molecule for bias voltages near but below V{sub T}. (orig.)

  19. Applications of confocal laser scanning microscopy in research into organic semiconductor thin films

    DEFF Research Database (Denmark)

    Schiek, Manuela; Balzer, Frank

    2014-01-01

    At the center of opto-electronic devices are thin layers of organic semiconductors, which need to be sandwiched between planar electrodes. With the growing demand for opto-electronic devices now and in the future, new electrode materials are needed to meet the requirements of organic semiconductors...... laser scanning microscopy has emerged as a versatile tool for optical metrology while atomic force microscopy adds detailed structural information....

  20. Ambipolar Small-Molecule:Polymer Blend Semiconductors for Solution-Processable Organic Field-Effect Transistors.

    Science.gov (United States)

    Kang, Minji; Hwang, Hansu; Park, Won-Tae; Khim, Dongyoon; Yeo, Jun-Seok; Kim, Yunseul; Kim, Yeon-Ju; Noh, Yong-Young; Kim, Dong-Yu

    2017-01-25

    We report on the fabrication of an organic thin-film semiconductor formed using a blend solution of soluble ambipolar small molecules and an insulating polymer binder that exhibits vertical phase separation and uniform film formation. The semiconductor thin films are produced in a single step from a mixture containing a small molecular semiconductor, namely, quinoidal biselenophene (QBS), and a binder polymer, namely, poly(2-vinylnaphthalene) (PVN). Organic field-effect transistors (OFETs) based on QBS/PVN blend semiconductor are then assembled using top-gate/bottom-contact device configuration, which achieve almost four times higher mobility than the neat QBS semiconductor. Depth profile via secondary ion mass spectrometry and atomic force microscopy images indicate that the QBS domains in the films made from the blend are evenly distributed with a smooth morphology at the bottom of the PVN layer. Bias stress test and variable-temperature measurements on QBS-based OFETs reveal that the QBS/PVN blend semiconductor remarkably reduces the number of trap sites at the gate dielectric/semiconductor interface and the activation energy in the transistor channel. This work provides a one-step solution processing technique, which makes use of soluble ambipolar small molecules to form a thin-film semiconductor for application in high-performance OFETs.

  1. Photoelectron spectroscopy on doped organic semiconductors and related interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Olthof, Selina Sandra

    2010-06-08

    Using photoelectron spectroscopy, we show measurements of energy level alignment of organic semiconducting layers. The main focus is on the properties and the influence of doped layers. The investigations on the p-doping process in organic semiconductors show typical charge carrier concentrations up to 2.10{sup 20} cm{sup -3}. By a variation of the doping concentration, an over proportional influence on the position of the Fermi energy is observed. Comparing the number of charge carriers with the amount of dopants present in the layer, it is found that only 5% of the dopants undergo a full charge transfer. Furthermore, a detailed investigation of the density of states beyond the HOMO onset reveals that an exponentially decaying density of states reaches further into the band gap than commonly assumed. For an increasing amount of doping, the Fermi energy gets pinned on these states which suggests that a significant amount of charge carriers is present there. The investigation of metal top and bottom contacts aims at understanding the asymmetric current-voltage characteristics found for some symmetrically built device stacks. It can be shown that a reaction between the atoms from the top contact with the molecules of the layer leads to a change in energy level alignment that produces a 1.16 eV lower electron injection barrier from the top. Further detailed investigations on such contacts show that the formation of a silver top contact is dominated by diffusion processes, leading to a broadened interface. However, upon insertion of a thin aluminum interlayer this diffusion can be stopped and an abrupt interface is achieved. Furthermore, in the case of a thick silver top contact, a monolayer of molecules is found to oat on top of the metal layer, almost independent on the metal layer thickness. Finally, several device stacks are investigated, regarding interface dipoles, formation of depletion regions, energy alignment in mixed layers, and the influence of the built

  2. Back-side readout semiconductor photomultiplier

    Science.gov (United States)

    Choong, Woon-Seng; Holland, Stephen E

    2014-05-20

    This disclosure provides systems, methods, and apparatus related to semiconductor photomultipliers. In one aspect, a device includes a p-type semiconductor substrate, the p-type semiconductor substrate having a first side and a second side, the first side of the p-type semiconductor substrate defining a recess, and the second side of the p-type semiconductor substrate being doped with n-type ions. A conductive material is disposed in the recess. A p-type epitaxial layer is disposed on the second side of the p-type semiconductor substrate. The p-type epitaxial layer includes a first region proximate the p-type semiconductor substrate, the first region being implanted with p-type ions at a higher doping level than the p-type epitaxial layer, and a second region disposed on the first region, the second region being doped with p-type ions at a higher doping level than the first region.

  3. Determination of the transport levels in thin films of organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Krause, Stefan

    2009-07-27

    The approach of using the combination of Ultraviolet (UPS) and Inverse Photoemission (IPS) to determine the transport levels in thin films of organic semiconductors is the scope of this work. For this matter all influences on the peak position and width in Photoelectron Spectroscopy are discussed with a special focus on organic semiconductors. Many of these influences are shown with experimental results of the investigation of diindenoperylene on Ag(111). These findings are applied to inorganic semiconductors silicon in order to establish the use of UPS and IPS on a well-understood system. Finally, the method is used to determine the transport level of several organic semiconductors (PTCDA, Alq3, CuPc, DIP, PBI-H4) and the corresponding exciton binding energies are calculated by comparison to optical absorption data. (orig.)

  4. Study of charge-carrier relaxation in a disordered organic semiconductor by simulating impedance spectroscopy

    Science.gov (United States)

    Mesta, M.; Cottaar, J.; Coehoorn, R.; Bobbert, P. A.

    2014-05-01

    Impedance spectroscopy is a very sensitive probe of nonstationary charge transport governed by charge-carrier relaxation in devices of disordered organic semiconductors. We simulate impedance spectroscopy measurements of hole-only devices of a polyfluorene-based disordered organic semiconductor by solving a time-dependent three-dimensional master equation for the occupational probabilities of transport sites in the semiconductor. We focus on the capacitance-voltage characteristics at different frequencies. In order to obtain good agreement with the measured characteristics, we have to assume a lower strength of a Gaussian energy disorder than obtained from best fits to the stationary current density-voltage characteristics. This lower disorder strength is in agreement with dark-injection studies of nonstationary charge transport on the same devices. The results add to solving the puzzle of reconciling nonstationary with stationary charge-transport studies of disordered organic semiconductors.

  5. Functionalization of Organic Semiconductors and Other Carbon-based Materials by Self-Assembled Monolayers (SAMs) and Charge Transport in Organic Field-effect Transistors (OFETs)

    Science.gov (United States)

    Lee, Bumsu

    In the first part of the thesis, studies of the charge carrier transport in organic semiconductors performed using organic field-effect transistors (OFETs) with polymeric gate dielectric (parylene) are presented. By combining OFET and ultraviolet photoelectron spectroscopy (UPS) studies, the effect of bias-stress instability at the semiconductor/insulator interface have been investigated and understood. The effect is understood in terms of the transfer of holes from an accumulation channel of the semiconductor to localized states of the insulator that depends on energetic overlap between HOMO band tails of the semiconductor and the insulator. Second, surface functionalization of various materials such as organic single crystals, conjugated semiconductor polymers, graphene and carbon nanotubes (CNTs) with Self-Assembled Monolayers (SAMs) is described. In most cases, an enhanced surface conductivity is observed as a result of SAM treatment. Especially, fluorinated alkyl-silane (FTS) SAM induces the highest density of p-type charge carriers (in excess of an order of 1013cm-2), which leads to a strong surface hole-doping of these materials. In this thesis, (1) the mechanism of SAM nucleation, growth process and doping effect at the surface of organic single crystals and graphene is revealed. SAM nucleation occurs predominantly at molecular step edges or defect sites present at the surface and a consecutive lateral growth proceeds by cross-linking between SAM molecules. The strong hole-doping is explained by an interfacial charge transfer that during SAM formation. In addition, conductive atomic force microscopy (C-AFM) confirms that conducting paths along the step edges are formed by FTS nucleation at the early stage of FTS growth on rubrene. (2) it is reported that conductivity of solution-deposited thin film of conjugated polymers increases by up to six orders of magnitude, reaching (1.1 ± 0.1) × 103 Scm-1 for poly (2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b

  6. Real-Time Tracking of Singlet Exciton Diffusion in Organic Semiconductors

    NARCIS (Netherlands)

    Kozlov, Oleg V.; de Haan, Foppe; Kerner, Ross A.; Rand, Barry P.; Cheyns, David; Pshenichnikov, Maxim S.

    2016-01-01

    Exciton diffusion in organic materials provides the operational basis for functioning of such devices as organic solar cells and light-emitting diodes. Here we track the exciton diffusion process in organic semiconductors in real time with a novel technique based on femtosecond photoinduced absorpti

  7. Validity of the einstein relation in disordered organic semiconductors

    NARCIS (Netherlands)

    Wetzelaer, G.A.H.; Koster, L.J.A.; Blom, P.W.M.

    2011-01-01

    It is controversial whether energetic disorder in semiconductors is already sufficient to violate the classical Einstein relation, even in the case of thermal equilibrium. We demonstrate that the Einstein relation is violated only under nonequilibrium conditions due to deeply trapped carriers, as in

  8. Self-organizing nanochannel networks in periodically perforated semiconductor films

    NARCIS (Netherlands)

    Annabattula, R. K.; Onck, P. R.

    2011-01-01

    In this paper we theoretically analyze the mechanism of nanochannel formation by an evolutionary etching process in periodically perforated semiconductor films. The compressive stresses due to lattice mismatch of the epitaxially grown nanoscale films are gradually relaxed; leading to an evolutionary

  9. Synthesis and characterization of organic dyes with various electron-accepting substituents for p-type dye-sensitized solar cells.

    Science.gov (United States)

    Weidelener, Martin; Powar, Satvasheel; Kast, Hannelore; Yu, Ze; Boix, Pablo P; Li, Chen; Müllen, Klaus; Geiger, Thomas; Kuster, Simon; Nüesch, Frank; Bach, Udo; Mishra, Amaresh; Bäuerle, Peter

    2014-11-01

    Four new donor-π-acceptor dyes differing in their acceptor group have been synthesized and employed as model systems to study the influence of the acceptor groups on the photophysical properties and in NiO-based p-type dye-sensitized solar cells. UV/Vis absorption spectra showed a broad range of absorption coverage with maxima between 331 and 653 nm. Redox potentials as well as HOMO and LUMO energies of the dyes were determined from cyclic voltammetry measurements and evaluated concerning their potential use as sensitizers in p-type dye-sensitized solar cells (p-DSCs). Quantum-chemical density functional theory calculations gave further insight into the frontier orbital distributions, which are relevant for the electronic processes in p-DSCs. In p-DSCs using an iodide/triiodide-based electrolyte, the polycyclic 9,10-dicyano-acenaphtho[1,2-b]quinoxaline (DCANQ) acceptor-containing dye gave the highest power conversion efficiency of 0.08%, which is comparable to that obtained with the perylenemonoimide (PMI)-containing dye. Interestingly, devices containing the DCANQ-based dye achieve a higher V(OC) of 163 mV compared to 158 mV for the PMI-containing dye. The result was further confirmed by impedance spectroscopic analysis showing higher recombination resistance and thus a lower recombination rate for devices containing the DCANQ dye than for PMI dye-based devices. However, the use of the strong electron-accepting tricyanofurane (TCF) group played a negative role in the device performance, yielding an efficiency of only 0.01% due to a low-lying LUMO energy level, thus resulting in an insufficient driving force for efficient dye regeneration. The results demonstrate that a careful molecular design with a proper choice of the acceptor unit is essential for development of sensitizers for p-DSCs.

  10. Two-photon Photoemission of Organic Semiconductor Molecules on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Aram [Univ. of California, Berkeley, CA (United States)

    2008-05-01

    Angle- and time-resolved two-photon photoemission (2PPE) was used to study systems of organic semiconductors on Ag(111). The 2PPE studies focused on electronic behavior specific to interfaces and ultrathin films. Electron time dynamics and band dispersions were characterized for ultrathin films of a prototypical n-type planar aromatic hydrocarbon, PTCDA, and representatives from a family of p-type oligothiophenes.In PTCDA, electronic behavior was correlated with film morphology and growth modes. Within a fewmonolayers of the interface, image potential states and a LUMO+1 state were detected. The degree to which the LUMO+1 state exhibited a band mass less than a free electron mass depended on the crystallinity of the layer. Similarly, image potential states were measured to have free electron-like effective masses on ordered surfaces, and the effective masses increased with disorder within the thin film. Electron lifetimes were correlated with film growth modes, such that the lifetimes of electrons excited into systems created by layer-by-layer, amorphous film growth increased by orders of magnitude by only a few monolayers from the surface. Conversely, the decay dynamics of electrons in Stranski-Krastanov systems were limited by interaction with the exposed wetting layer, which limited the barrier to decay back into the metal.Oligothiophenes including monothiophene, quaterthiophene, and sexithiophene were deposited on Ag(111), and their electronic energy levels and effective masses were studied as a function of oligothiophene length. The energy gap between HOMO and LUMO decreased with increasing chain length, but effective mass was found to depend on domains from high- or low-temperature growth conditions rather than chain length. In addition, the geometry of the molecule on the surface, e.g., tilted or planar, substantially affected the electronic structure.

  11. Synthesis and Properties of Heteroacenes Containing Pyrrole and Thiazine Rings as Promising n-Type Organic Semiconductor Candidates

    Institute of Scientific and Technical Information of China (English)

    HONG,Wei; WEI,Zhongming; XU,Wei; WANG,Quanrui; ZHU,Daoben

    2009-01-01

    PBBTZ (6H-pyrrolo[3,2-b:4,5-b']bis[1,4]benzothiazine) was a p-type semiconductor with high field-effect transistor (FET) performance that we have just reported.Two trifluoromethyl substituted PBBTZ derivatives 3a and 3b were synthesized from facile one-pot condensation.They were characterized by means of 1H NMR,IR,HRMS (EI-TOF) and elemental analysis,furthermore,the crystal structure of 3b was described and discussed.Their optical properties were studied by UV-Vis and fluorescence spectroscopy,electrochemical properties were investigated by cyclic voltammetry (CV),and thermal properties were evaluated by thermal gravimetric analysis (TGA).The energy gaps of 3a and 3b,taken directly from spectroscopic measurements,are as broad as 2.45 and 2.48 eV,leading to bluish green and green photoluminescence.The LUMO and HOMO energy levels are -5.73 and -3.28 eV for 3a,-5.67 and -3.19 eV for 3b,respectively.The low energy levels render them well air-stable,and to be promising n-type semiconductor candidates for use in organic electronics.

  12. Tetracene dicarboxylic imide and its disulfide: synthesis of ambipolar organic semiconductors for organic photovoltaic cells.

    Science.gov (United States)

    Okamoto, Toshihiro; Suzuki, Tsuyoshi; Tanaka, Hideyuki; Hashizume, Daisuke; Matsuo, Yutaka

    2012-01-02

    We have designed and synthesized a new donor/acceptor-type tetracene derivative by the introduction of dicarboxylic imide and disulfide groups as electron-withdrawing and -donating units, respectively. The prepared compounds, tetracene dicarboxylic imide (TI) and its disulfide (TIDS) have high chemical and electrochemical stability as well as long-wavelength absorptions of up to 886 nm in the thin films. The crystal packing structure of TIDS molecules features face-to-face π-stacking, derived from dipole-dipole interactions. Notably, TIDS exhibited ambipolar properties of both electron-donating and -accepting natures in p-n and p-i-n heterojunction organic thin-film photovoltaic devices. Accordingly, TI and TIDS are expected to be promising compounds for designing new organic semiconductors.

  13. All-polymer organic semiconductor laser chips: Parallel fabrication and encapsulation

    DEFF Research Database (Denmark)

    Vannahme, Christoph; Klinkhammer, Sönke; Christiansen, Mads Brøkner

    2010-01-01

    Organic semiconductor lasers are of particular interest as tunable visible laser light sources. For bringing those to market encapsulation is needed to ensure practicable lifetimes. Additionally, fabrication technologies suitable for mass production must be used. We introduce all-polymer chips...... comprising encapsulated distributed feedback organic semiconductor lasers. Several chips are fabricated in parallel by thermal nanoimprint of the feedback grating on 4? wafer scale out of poly(methyl methacrylate) (PMMA) and cyclic olefin copolymer (COC). The lasers consisting of the organic semiconductor...... tris(8- hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2- methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM) are hermetically sealed by thermally bonding a polymer lid. The organic thin film is placed in a basin within the substrate and is not in direct contact to the lid...

  14. Spectroscopy of Charge Carriers and Traps in Field-Doped Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang; Frisbie, C Daniel

    2012-08-13

    This research project aims to achieve quantitative and molecular level understanding of charge carriers and traps in field-doped organic semiconductors via in situ optical absorption spectroscopy, in conjunction with time-resolved electrical measurements. During the funding period, we have made major progress in three general areas: (1) probed charge injection at the interface between a polymeric semiconductor and a polymer electrolyte dielectric and developed a thermodynamic model to quantitatively describe the transition from electrostatic to electrochemical doping; (2) developed vibrational Stark effect to probe electric field at buried organic semiconductor interfaces; (3) used displacement current measurement (DCM) to study charge transport at organic/dielectric interfaces and charge injection at metal/organic interfaces.

  15. Effect of Carrier Differences on Spin Polarized Injection into Organic and Inorganic Semiconductors

    Institute of Scientific and Technical Information of China (English)

    REN Jun-Feng; XIU Ming-Xia

    2008-01-01

    Spin polarized injection into organic and inorganic semiconductors are studied theoretically from the spin diffusion theory and Ohm's law, and the emphases are placed on the effect of the carrier differences on the current spin polarization. The mobility and the spin-Rip time of carriers in organic and inorganic semiconductors are different. From the calculation, it is found that current spin polarization at a ferromagnetic/organic interface is higher than that at a ferromagnetic/inorganic interface because of different carriers in them. Effects of the conductivity matching, the spin dependent interfacial resistances, and the balk spin polarization of the ferromagnetic layer on the spin polarized injection are also discussed.

  16. New Organic Semiconductor Materials Applied in Organic Photovoltaic and Optical Devices

    Directory of Open Access Journals (Sweden)

    Andre F. S. Guedes

    2015-04-01

    Full Text Available The development of flexible organic photovoltaic solar cells, using an optically transparent substrate material and organic semiconductor materials, has been widely utilized by the electronic industry when producing new technological products. The flexible organic photovoltaic solar cells are the base Poly (3,4-ethylenedioxythiophene, PEDOT, Poly(3-hexyl thiophene, P3HT, Phenyl-C61-butyric acid methyl ester, PCBM and Polyaniline, PANI, were deposited in Indium Tin Oxide, ITO, and characterized by Electrical Measurements and Scanning Electron Microscopy (SEM. In addition, the thin film obtained by the deposition of PANI, prepared in perchloric acid solution, was identified through PANI-X1. The result obtained by electrical Measurements has demonstrated that the PET/ITO/PEDOT/P3HT:PCBM Blend/PANI-X1 layer presents the characteristic curve of standard solar cell after spin-coating and electrodeposition. The Thin film obtained by electrodeposition of PANI-X1 on P3HT/PCBM Blend was prepared in perchloric acid solution. These flexible organic photovoltaic solar cells presented power conversion efficiency of 12%. The inclusion of the PANI-X1 layer reduced the effects of degradation these organic photovoltaic panels induced for solar irradiation. In Scanning Electron Microscopy (SEM these studies reveal that the surface of PANI-X1 layers is strongly conditioned by the surface morphology of the dielectric.

  17. p-Type Semiconducting Nickel Oxide as an Efficiency-Enhancing Anode Interfacial Layer in Polymer Bulk-Heterojunction Solar Cells

    National Research Council Canada - National Science Library

    Michael D. Irwin; D. Bruce Buchholz; Alexander W. Hains; Robert P. H. Chang; Tobin J. Marks

    2008-01-01

    To minimize interfacial power losses, thin (5-80 nm) layers of NiO, a p-type oxide semiconductor, are inserted between the active organic layer, poly(3-hexylthiophene) (P3HT) + [6,6]-phenyl-C₆₁...

  18. N-doping of organic semiconductors by bis-metallosandwich compounds

    Science.gov (United States)

    Barlow, Stephen; Qi, Yabing; Kahn, Antoine; Marder, Seth; Kim, Sang Bok; Mohapatra, Swagat K.; Guo, Song

    2016-01-05

    The various inventions disclosed, described, and/or claimed herein relate to the field of methods for n-doping organic semiconductors with certain bis-metallosandwich compounds, the doped compositions produced, and the uses of the doped compositions in organic electronic devices. Metals can be manganese, rhenium, iron, ruthenium, osmium, rhodium, or iridium. Stable and efficient doping can be achieved.

  19. Smooth Growth of Organic Semiconductor Films on Graphene for High-Efficiency Electronics

    NARCIS (Netherlands)

    Hlawacek, G.; Khokhar, F.S.; van Gastel, Raoul; Poelsema, Bene; Teichert, Christian

    2011-01-01

    High-quality thin films of conjugated molecules with smooth interfaces are important to assist the advent of organic electronics. Here, we report on the layer-by-layer growth of the organic semiconductor molecule p-sexiphenyl (6P) on the transparent electrode material graphene. Low energy electron

  20. Synthesis of Perylene Imide Diones as Platforms for the Development of Pyrazine Based Organic Semiconductors.

    Science.gov (United States)

    de Echegaray, Paula; Mancheño, María J; Arrechea-Marcos, Iratxe; Juárez, Rafael; López-Espejo, Guzmán; López Navarrete, J Teodomiro; Ramos, María Mar; Seoane, Carlos; Ortiz, Rocío Ponce; Segura, José L

    2016-11-18

    There is a great interest in peryleneimide (PI)-containing compounds given their unique combination of good electron accepting ability, high abosorption in the visible region, and outstanding chemical, thermal, and photochemical stabilities. Thus, herein we report the synthesis of perylene imide derivatives endowed with a 1,2-diketone functionality (PIDs) as efficient intermediates to easily access peryleneimide (PI)-containing organic semiconductors with enhanced absorption cross-section for the design of tunable semiconductor organic materials. Three processable organic molecular semiconductors containing thiophene and terthiophene moieties, PITa, PITb, and PITT, have been prepared from the novel PIDs. The tendency of these semiconductors for molecular aggregation have been investigated by NMR spectroscopy and supported by quantum chemical calculations. 2D NMR experiments and theoretical calculations point to an antiparallel π-stacking interaction as the most stable conformation in the aggregates. Investigation of the optical and electrochemical properties of the materials is also reported and analyzed in combination with DFT calculations. Although the derivatives presented here show modest electron mobilities of ∼10(-4) cm(2)V(-1)s(-1), these preliminary studies of their performance in organic field effect transistors (OFETs) indicate the potential of these new building blocks as n-type semiconductors.

  1. Universal arrhenius temperature activated charge transport in diodes from disordered organic semiconductors.

    Science.gov (United States)

    Craciun, N I; Wildeman, J; Blom, P W M

    2008-02-08

    Charge transport models developed for disordered organic semiconductors predict a non-Arrhenius temperature dependence ln(mu) proportional, variant1/T(2) for the mobility mu. We demonstrate that in space-charge limited diodes the hole mobility (micro(h)) of a large variety of organic semiconductors shows a universal Arrhenius temperature dependence micro(h)(T) = micro(0)exp(-Delta/kT) at low fields, due to the presence of extrinsic carriers from the Ohmic contact. The transport in a range of organic semiconductors, with a variation in room temperature mobility of more than 6 orders of magnitude, is characterized by a universal mobility micro(0) of 30-40 cm(2)/V s. As a result, we can predict the full temperature dependence of their charge transport properties with only the mobility at one temperature known.

  2. Quantitative Determination of Organic Semiconductor Microstructure from the Molecular to Device Scale

    KAUST Repository

    Rivnay, Jonathan

    2012-10-10

    A study was conducted to demonstrate quantitative determination of organic semiconductor microstructure from the molecular to device scale. The quantitative determination of organic semiconductor microstructure from the molecular to device scale was key to obtaining precise description of the molecular structure and microstructure of the materials of interest. This information combined with electrical characterization and modeling allowed for the establishment of general design rules to guide future rational design of materials and devices. Investigations revealed that a number and variety of defects were the largest contributors to the existence of disorder within a lattice, as organic semiconductor crystals were dominated by weak van der Waals bonding. Crystallite size, texture, and variations in structure due to spatial confinement and interfaces were also found to be relevant for transport of free charge carriers and bound excitonic species over distances that were important for device operation.

  3. Fabrication and performance of pressure-sensing device consisting of electret film and organic semiconductor

    Science.gov (United States)

    Kodzasa, Takehito; Nobeshima, Daiki; Kuribara, Kazunori; Uemura, Sei; Yoshida, Manabu

    2017-04-01

    We propose a new concept of a pressure-sensitive device that consists of an organic electret film and an organic semiconductor. This device exhibits high sensitivity and selectivity against various types of pressure. The sensing mechanism of this device originates from a modulation of the electric conductivity of the organic semiconductor film induced by the interaction between the semiconductor film and the charged electret film placed face to face. It is expected that a complicated sensor array will be fabricated by using a roll-to-roll manufacturing system, because this device can be prepared by an all-printing and simple lamination process without high-level positional adjustment for printing processes. This also shows that this device with a simple structure is suitable for application to a highly flexible device array sheet for an Internet of Things (IoT) or wearable sensing system.

  4. Developing high mobility emissive organic semiconductors towards integrated optoelectronic devices (Conference Presentation)

    Science.gov (United States)

    Dong, Huanli; Hu, Wenping; Heeger, Alan J.

    2016-09-01

    The achievement of organic semiconductors with both high mobility and strong fluorescence emission remains a challenge. High mobility requires molecules which pack densely and periodically, while serious fluorescence quenching typically occurs when fluorescent materials begin to aggregate (aggregation-induced quenching (AIQ)). Indeed, classical materials with strong fluorescent emission always exhibit low mobility, for example, tris(8-hydroxyquinoline) aluminium (ALQ) and phenylenevinylene-based polymers with mobility only 10-6-10-5 cm2V-1s-1, and benchmark organic semiconductors with high mobility demonstrate very weak emission, for example, rubrene exhibits a quantum yield 1% in crystalline state and pentacene shows very weak fluorescence in the solid state. However, organic semiconductors with high mobility and strong fluorescence are necessary for the achievement of high efficiency organic light-emitting transistors (OLETs) and electrically pumped organic lasers. Therefore, it is necessary for developing high mobility emissive organic/polymeric semiconductors towards a fast mover for the organic optoelectronic integrated devices and circuits.

  5. Low-voltage organic electronics based on a gate-tunable injection barrier in vertical graphene-organic semiconductor heterostructures.

    Science.gov (United States)

    Hlaing, Htay; Kim, Chang-Hyun; Carta, Fabio; Nam, Chang-Yong; Barton, Rob A; Petrone, Nicholas; Hone, James; Kymissis, Ioannis

    2015-01-14

    The vertical integration of graphene with inorganic semiconductors, oxide semiconductors, and newly emerging layered materials has recently been demonstrated as a promising route toward novel electronic and optoelectronic devices. Here, we report organic thin film transistors based on vertical heterojunctions of graphene and organic semiconductors. In these thin heterostructure devices, current modulation is accomplished by tuning of the injection barriers at the semiconductor/graphene interface with the application of a gate voltage. N-channel devices fabricated with a thin layer of C60 show a room temperature on/off ratio >10(4) and current density of up to 44 mAcm(-2). Because of the ultrashort channel intrinsic to the vertical structure, the device is fully operational at a driving voltage of 200 mV. A complementary p-channel device is also investigated, and a logic inverter based on two complementary transistors is demonstrated. The vertical integration of graphene with organic semiconductors via simple, scalable, and low-temperature fabrication processes opens up new opportunities to realize flexible, transparent organic electronic, and optoelectronic devices.

  6. Comparison of Ohmic contact resistances of n- and p-type Ge source/drain and their impact on transport characteristics of Ge metal oxide semiconductor field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jungwoo, E-mail: jungwoo.oh@sematech.org [SEMATECH, 2706 Montopolis Drive, Austin, TX 78741 (United States); Huang, Jeff [SEMATECH, 2706 Montopolis Drive, Austin, TX 78741 (United States); Chen, Yen-Ting [Universityof Texas, Austin, TX (United States); Ok, Injo [SEMATECH, 2706 Montopolis Drive, Austin, TX 78741 (United States); Jeon, Kanghoon [Universityof California, Berkeley, CA (United States); Lee, Se-Hoon [Universityof Texas, Austin, TX (United States); Sassman, Barry; Loh, Wei-Yip [SEMATECH, 2706 Montopolis Drive, Austin, TX 78741 (United States); Lee, Hi-Deok [Chungnam National University (Korea, Republic of); Ko, Dea-Hong [Yonsei University (Korea, Republic of); Majhi, Prashant; Kirsch, Paul; Jammy, Raj [SEMATECH, 2706 Montopolis Drive, Austin, TX 78741 (United States)

    2011-10-31

    We report the results of a systematic study to understand low drive current of Ge-nMOSFET (metal-oxide-semiconductor field-effect transistor). The poor electron transport property is primarily attributed to the low dopant activation efficiency and high contact resistance. Results are supported by analyzing source/drain Ohmic metal contacts to n-type Ge using the transmission line method. Ni contacts to Ge nMOSFETs exhibit specific contact resistances of 10{sup -3}-10{sup -5} {Omega} cm{sup 2}, which is significantly higher than the 10{sup -7}-10{sup -8} {Omega} cm{sup 2} of Ni contacts to Ge pMOSFETs. The high resistance of Ni Ohmic contacts to n-type Ge is attributed mainly to insufficient dopant activation in Ge (or high sheet resistance) and a high tunneling barrier. Results obtained in this work identify one of the root causes of the lower than expected Ge nMOSFET transport issue, advancing high mobility Ge channel technology.

  7. Evolution of plant P-type ATPases

    Directory of Open Access Journals (Sweden)

    Christian N.S. Pedersen

    2012-02-01

    Full Text Available Five organisms having completely sequenced genomes and belonging to all major branches of green plants (Viridiplantae were analyzed with respect to their content of P-type ATPases encoding genes. These were the chlorophytes Ostreococcus tauria and Chlamydomonas reinhardtii, and the streptophytes Physcomitrella patens (a moss, Selaginella moellendorffii (a primitive vascular plant, and Arabidopsis thaliana (a model flowering plant. Each organism contained sequences for all five subfamilies of P-type ATPases. Our analysis demonstrates when specific subgroups of P-type ATPases disappeared in the evolution of Angiosperms. Na/K-pump related P2C ATPases were lost with the evolution of streptophytes whereas Na+ or K+ pumping P2D ATPases and secretory pathway Ca2+-ATPases remained until mosses. An N-terminally located calmodulin binding domain in P2B ATPases can only be detected in pumps from Streptophytae, whereas, like in animals, a C-terminally localized calmodulin binding domain might be present in chlorophyte P2B Ca2+-ATPases. Chlorophyte genomes encode P3A ATPases resembling protist plasma membrane H+-ATPases and a C-terminal regulatory domain is missing. The complete inventory of P-type ATPases in the major branches of Viridiplantae is an important starting point for elucidating the evolution in plants of these important pumps.

  8. Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

    Directory of Open Access Journals (Sweden)

    David W. Manley

    2015-09-01

    Full Text Available Heterogeneous semiconductor photoredox catalysis (SCPC, particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C–N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.

  9. Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis.

    Science.gov (United States)

    Manley, David W; Walton, John C

    2015-01-01

    Heterogeneous semiconductor photoredox catalysis (SCPC), particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i) interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii) interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C-N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.

  10. New concept to break the intrinsic properties of organic semiconductors for optical sensing applications

    Science.gov (United States)

    Choy, Wallace C. H.

    2015-09-01

    As the intrinsic electrostatic limit, space charge limit (SCL) for photocurrent is a universal phenomenon which is fundamental important for organic semiconductors. We will demonstrate SCL breaking by a new plasmonic-electrical concept. As a proof-ofconcept, organic solar cells (OSCs) comprising metallic planar and grating electrodes are studied. Interestingly, although strong plasmonic resonances induce abnormally dense photocarriers around a grating anode, the grating incorporated inverted OSC is exempt from space charge accumulation (limit) and degradation of electrical properties. The plasmonic-electrical concept will open up a new way to manipulate both optical and electrical properties of semiconductor devices simultaneously.

  11. A review of carrier thermoelectric-transport theory in organic semiconductors.

    Science.gov (United States)

    Lu, Nianduan; Li, Ling; Liu, Ming

    2016-07-20

    Carrier thermoelectric-transport theory has recently become of growing interest and numerous thermoelectric-transport models have been proposed for organic semiconductors, due to pressing current issues involving energy production and the environment. The purpose of this review is to provide a theoretical description of the thermoelectric Seebeck effect in organic semiconductors. Special attention is devoted to the carrier concentration, temperature, polaron effect and dipole effect dependence of the Seebeck effect and its relationship to hopping transport theory. Furthermore, various theoretical methods are used to discuss carrier thermoelectric transport. Finally, an outlook of the remaining challenges ahead for future theoretical research is provided.

  12. Investigation of L-cystine assisted Cu3BiS 3 synthesis for energetically and environmentally improved integration as thin-film solar cell p-type semiconductor absorber

    Science.gov (United States)

    Viezbicke, Brian D.

    Solar photovoltaic energy technology is increasingly implemented in response to continuously growing global energy needs. While legacy technology utilizing silicon has captured much of the market, thin-film solar modules are projected to rise particularly in the U.S. production sector. Current materials utilized in production and deployment encounter resource and environmental impact constraints. This research investigates the viably controllable synthesis of multi-crystalline copper bismuth sulfide for potential use as an absorber layer in thin-film solar cells and early investigation of thin-film growth parameters which may enable a cost-effective route to full scale production of epitaxial copper bismuth sulfide films. The first step of this investigation has entailed a novel route for the solvo-thermally grown Cu3BiS 3 films facilitated by L-cystine as a sulfur donating and complexing agent. In the characterization of the nanoparticulate product UV-VIS spectra were analyzed via the Tauc method of bandgap interpolation. The validity of the Tauc method in application to polycrystalline films has been investigated and proven to be robust for the material class. This justifies the bandgap assessment of the subject material and provides support for wider use of the method. With the synthesis method established, the reaction was transferred to a custom built continuous flow reactor to explore this process and help understand its capabilities and limits with respect to producing single layers for an eventual photovoltaic cell stack. Though the published work has established novel chemistry, the need to deposit and/or grow a functional p-type layer for further characterization and eventual device incorporation is key to the material evolution. First evidence of continuous flow micro-reactor deposition of Cu3BiS3 has been shown with an array of resulting microstructures. The grown microstructures are evaluated with relevance to prior synthesis laboratory procedure and

  13. Driving High-Performance n- and p-type Organic Transistors with Carbon Nanotube/Conjugated Polymer Composite Electrodes Patterned Directly from Solution

    KAUST Repository

    Hellstrom, Sondra L.

    2010-07-12

    We report patterned deposition of carbon nanotube/conjugated polymer composites from solution with high nanotube densities and excellent feature resolution. Such composites are suited for use as electrodes in high-performance transistors of pentacene and C60, with bottom-contact mobilities of ?0.5 and ?1 cm2 V-1 s-1, respectively. This represents a clear step towards development of inexpensive, high-performance all-organic circuits. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Charge-transfer mobility and electrical conductivity of PANI as conjugated organic semiconductors

    Science.gov (United States)

    Zhang, Yahong; Duan, Yuping; Song, Lulu; Zheng, Daoyuan; Zhang, Mingxing; Zhao, Guangjiu

    2017-09-01

    The intramolecular charge transfer properties of a phenyl-end-capped aniline tetramer (ANIH) and a chloro-substituted derivative (ANICl) as organic semiconductors were theoretically studied through the first-principles calculation based on the Marcus-Hush theory. The reorganization energies, intermolecular electronic couplings, angular resolution anisotropic mobilities, and density of states of the two crystals were evaluated. The calculated results demonstrate that both ANIH and ANICl crystals show the higher electron transfer mobilities than the hole-transfer mobilities, which means that the two crystals should prefer to function as n-type organic semiconductors. Furthermore, the angle dependence mobilities of the two crystals show remarkable anisotropic character. The maximum mobility μmax of ANIH and ANICl crystals is 1.3893 and 0.0272 cm2 V-1 s-1, which appear at the orientation angles near 176°/356° and 119°/299° of a conducting channel on the a-b reference plane. It is synthetically evaluated that the ANIH crystal possesses relatively lower reorganization energy, higher electronic coupling, and electron transfer mobility, which means that the ANIH crystal may be the more ideal candidate as a high performance n-type organic semiconductor material. The systematic theoretical studies on organic crystals should be conducive to evaluating the charge-transport properties and designing higher performance organic semiconductor materials.

  15. Efficient light emission from inorganic and organic semiconductor hybrid structures by energy-level tuning.

    Science.gov (United States)

    Schlesinger, R; Bianchi, F; Blumstengel, S; Christodoulou, C; Ovsyannikov, R; Kobin, B; Moudgil, K; Barlow, S; Hecht, S; Marder, S R; Henneberger, F; Koch, N

    2015-04-15

    The fundamental limits of inorganic semiconductors for light emitting applications, such as holographic displays, biomedical imaging and ultrafast data processing and communication, might be overcome by hybridization with their organic counterparts, which feature enhanced frequency response and colour range. Innovative hybrid inorganic/organic structures exploit efficient electrical injection and high excitation density of inorganic semiconductors and subsequent energy transfer to the organic semiconductor, provided that the radiative emission yield is high. An inherent obstacle to that end is the unfavourable energy level offset at hybrid inorganic/organic structures, which rather facilitates charge transfer that quenches light emission. Here, we introduce a technologically relevant method to optimize the hybrid structure's energy levels, here comprising ZnO and a tailored ladder-type oligophenylene. The ZnO work function is substantially lowered with an organometallic donor monolayer, aligning the frontier levels of the inorganic and organic semiconductors. This increases the hybrid structure's radiative emission yield sevenfold, validating the relevance of our approach.

  16. Characterization of solution structure and its importance in thin film ordering of conjugated block copolymers for organic semiconductor devices

    Science.gov (United States)

    Brady, Michael; Ku, Sung-Yu; Cochran, Justin; Wang, Cheng; Hawker, Craig; Kramer, Edward; Chabinyc, Michael

    2014-03-01

    Fully conjugated diblock copolymers (CBCPs) form intriguing materials alternatives to polymer-small molecule blends for their control of mesoscopic order in low-cost organic semiconductor devices. In both bulk heterojunction (BHJ) photovoltaics, consisting of an interpenetrating network with high donor-acceptor interfacial area, and ambipolar transistors, the transport of charge carriers through continuous p- and n-type paths in thin films is a controlling factor in device performance. AFM, GIWAXS, NEXAFS spectroscopy, and RSoXS are used to probe the structure of films of CBCPs with a p-type P3HT block and an n-type DPP block. Thermal annealing in the P3HT melt after casting creates ordered domains with ~ 50 nm in-plane lamellar spacings, as confirmed with GISAXS and RSoXS. GIWAXS diffraction from the (h00) alkyl-stacking and (010) pi-stacking planes shows primarily edge-on orientation for crystals of both P3HT and DPP blocks. In addition, temperature-dependent solution SAXS and UV-Vis spectroscopy are used to probe the size and conformation of casting solution aggregates. Fibrillar DPP aggregates direct the crystallization of P3HT- b-DPP following film casting and enable the formation of wormlike domains after annealing and thus ideal morphologies for transport in organic devices.

  17. Multiscale self-organization of the organic semiconductor alpha-quinquethiophene.

    Science.gov (United States)

    Melucci, Manuela; Gazzano, Massimo; Barbarella, Giovanna; Cavallini, Massimiliano; Biscarini, Fabio; Maccagnani, Piera; Ostoja, Paolo

    2003-08-27

    We show that thin films grown by vacuum sublimation, or formed by melted powders, of semiconductor alpha-quinquethiophene (T5) exhibit a hierarchical self-affinity organization that spans scales from tens of nanometers to hundreds of micrometers. T5 organization was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), and optical microscopy. XRD showed that vacuum-evaporated T5 films were characterized by a preferred orientation of the h00 planes parallel to the glass substrate. Melting of the films followed by rapid quenching to room temperature led to the formation of micrometer-sized, single-crystal-like structures, characterized by uniaxially aligned stripes. XRD proved that the melting-quenching process enhanced molecular ordering and increased the size of domains with the molecule's long axes tilted by about 65 degrees with respect to the substrate plane and piled up side-by-side along parallel columns. AFM measurements on the melt-quenched structures showed that a hierarchical architecture was built by reiteration across multiple length scales of the same recurring motif. Because of the tendency of T5 to form highly crystalline vacuum-evaporated thin films, a field-effect hole mobility comparable to state-of-the-art FET mobility of alpha-sexithiophene films was reached, without any attempt to optimize deposition conditions.

  18. Interface-controlled growth of organic semiconductors on graphene

    Science.gov (United States)

    Mathew, Jinta; Emin, Saim; Pavlica, Egon; Valant, Matjaž; Bratina, Gvido

    2017-10-01

    We have studied submonolayer coverages of N,N-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) on mechanically exfoliated graphene transferred onto SiO2 substrates. Our atomic force microscopy (AFM) data show that PDIF-CN2 forms irregularly-shaped 1.4 nm-high islands. From the selected area diffraction performed with transmission electron microscope (TEM) we conclude that this height corresponds to π - π stacks of molecules, which are inclined for 43° relative to the graphene surface. AFM also showed complete absence of PDIF-CN2 on single-layer graphene (SLG). Electric force microscopy revealed a marked difference in surface charge density between a single-layer graphene and bilayer graphene, with a higher surface charge on SLG than on the bilayer graphene. We associate this behavior with p - type doping of graphene due to the electrostatic dipole induced by the molecular water layer present at the graphene/SiO2 interface. The crucial role of the graphene/SiO2 interface in determining growth of PDIF-CN2 was further confirmed by TEM examination of PDIF-CN2 deposited onto unsupported SLG.

  19. Interface Design Principles for High-Performance Organic Semiconductor Devices.

    Science.gov (United States)

    Nie, Wanyi; Gupta, Gautam; Crone, Brian K; Liu, Feilong; Smith, Darryl L; Ruden, P Paul; Kuo, Cheng-Yu; Tsai, Hsinhan; Wang, Hsing-Lin; Li, Hao; Tretiak, Sergei; Mohite, Aditya D

    2015-06-01

    Precise manipulation of organic donor-acceptor interfaces using spacer layers is demonstrated to suppress interface recombination in an organic photo-voltaic device. These strategies lead to a dramatic improvement in a model bilayer system and bulk-heterojunction system. These interface strategies are applicable to a wide variety of donor-acceptor systems, making them both fundamentally interesting and technologically relevant for achieving high efficiency organic electronic devices.

  20. Retention Time and Depolarization in Organic Nonvolatile Memories Based on Ferroelectric Semiconductor Phase-Separated Blends

    NARCIS (Netherlands)

    Asadi, Kamal; Wildeman, Jurjen; Blom, Paul W. M.; de Leeuw, Dago M.

    2010-01-01

    Resistive switches have been fabricated using a phase-separated blend film of ferroelectric random copolymer poly(vinylidene fluoride-co-trifluoroethylene) with the organic semiconductor regio-irregular poly(3-hexylthiophene) (rir-P3HT). Spin-coated blend films have been contacted with symmetrical A

  1. Retention time and depolarization in organic nonvolatile memories based on ferroelectric semiconductor phase-separated blends

    NARCIS (Netherlands)

    Asadi, K.; Wildeman, J.; Blom, P.W.M.; Leeuw, D.M. de

    2010-01-01

    Resistive switches have been fabricated using a phase-separated blend film of ferroelectric random copolymer poly(vinylidene fluoride-co-trifluoroethylene) with the organic semiconductor regio-irregular poly(3-hexylthiophene) (rir-P3HT). Spin-coated blend films have been contacted with symmetrical A

  2. Bias-induced photoluminescence quenching of single colloidal quantum dots embedded in organic semiconductors.

    Science.gov (United States)

    Huang, Hao; Dorn, August; Nair, Gautham P; Bulović, Vladimir; Bawendi, Moungi G

    2007-12-01

    We demonstrate reversible quenching of the photoluminescence from single CdSe/ZnS colloidal quantum dots embedded in thin films of the molecular organic semiconductor N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) in a layered device structure. Our analysis, based on current and charge carrier density, points toward field ionization as the dominant photoluminescence quenching mechanism. Blinking traces from individual quantum dots reveal that the photoluminescence amplitude decreases continuously as a function of increasing forward bias even at the single quantum dot level. In addition, we show that quantum dot photoluminescence is quenched by aluminum tris(8-hydroxyquinoline) (Alq3) in chloroform solutions as well as in thin solid films of Alq3 whereas TPD has little effect. This highlights the importance of chemical compatibility between semiconductor nanocrystals and surrounding organic semiconductors. Our study helps elucidate elementary interactions between quantum dots and organic semiconductors, knowledge needed for designing efficient quantum dot organic optoelectronic devices.

  3. Direct Measurement of the Triplet Exciton Diffusion Length in Organic Semiconductors

    NARCIS (Netherlands)

    Mikhnenko, Oleksandr V.; Ruiter, Roald; Blom, Paul W. M.; Loi, Maria Antonietta

    2012-01-01

    We present a new method to measure the triplet exciton diffusion length in organic semiconductors. N,N'-di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine (NPD) has been used as a model system. Triplet excitons are injected into a thin film of NPD by a phosphorescent thin film, which is opti

  4. Charge transport calculations of organic semiconductors by the time-dependent wave-packet diffusion method

    Science.gov (United States)

    Ishii, Hiroyuki; Kobayashi, Nobuhiko; Hirose, Kenji

    2012-02-01

    Organic materials form crystals by relatively weak Van der Waals attraction between molecules, and thus differ fundamentally from covalently bonded semiconductors. Carriers in the organic semiconductors induce the drastic lattice deformation, which is called as polaron state. The polaron effect on the transport is a serious problem. Exactly what conduction mechanism applies to organic semiconductors has not been established. Therefore, we have investigated the transport properties using the Time-Dependent Wave-Packet Diffusion (TD-WPD) method [1]. To consider the polaron effect on the transport, in the methodology, we combine the wave-packet dynamics based on the quantum mechanics theory with the molecular dynamics. As the results, we can describe the electron motion modified by (electron-phonon mediated) time-dependent structural change. We investigate the transport property from an atomistic viewpoint and evaluate the mobility of organic semiconductors. We clarify the temperature dependence of mobility from the thermal activated behavior to the power law behavior. I will talk about these results in my presentation. [1] H. Ishii, N. Kobayashi, K. Hirose, Phys. Rev. B, 82 085435 (2010).

  5. Intrinsic charge trapping in organic and polymeric semiconductors: a physical chemistry perspective

    Energy Technology Data Exchange (ETDEWEB)

    Kaake, Loren [Univ. of Texas, Austin, TX (United States); Barbara, Paul F. [Univ. of Texas, Austin, TX (United States); Zhu, Xiaoyang [Univ. of Texas, Austin, TX (United States)

    2010-01-12

    We aim to understand the origins of intrinsic charge carrier traps in organic and polymeric semiconductor materials from a physical chemistry perspective. In crystalline organic semiconductors, we point out some of the inadequacies in the description of intrinsic charge traps using language and concepts developed for inorganic semiconductors. In π-conjugated polymeric semiconductors, we suggest the presence of a two-tier electronic energy landscape, a bimodal majority landscape due to two dominant structural motifs and a minority electronic energy landscape from intrinsic charged defects. The bimodal majority electronic energy landscape results from a combination of amorphous domains and microcrystalline or liquid-crystalline domains. The minority tier of the electronic density of states is comprised of deep Coulomb traps embedded in the majority electronic energy landscape. This minority electronic energy landscape may dominate transport properties at low charge carrier densities, such as those expected for organic photovoltaic devices, while the bimodal majority electronic energy landscape becomes significant at high carrier densities, that is, in organic field effect transistors.

  6. Polyfluorenes as organic semiconductors for polymeric field effect transistors

    Science.gov (United States)

    Brennan, David J.; Townsend, Paul H., III; Welsh, Dean M.; Dibbs, Mitchell G.; Shaw, Jeff M.; Miklovich, Jessica L.; Boeke, Robyn B.; Arias, Ana Claudia; Creswell, Lisa; MacKenzie, J. D.; Ramsdale, Catherine; Menon, Anoop; Sirringhaus, Henning

    2003-11-01

    Well-characterized F8T2 polyfluorene (Dow Chemical) has been prepared with weight average molecular weights (Mw) ranging from about 20,000 to 120,000. This semiconducting polymer has been used by Plastic Logic to fabricate arrays of 4,800 thin film transistors (TFTs) with 50 dpi, to be used as backplanes for active matrix displays. In this paper, the effects that molecular weight and thermal treatment have on the electrical characteristics of F8T2-based TFTs are reported. First, transistor performance improves with increasing molecular weight, with maximum values of TFT mobility approaching 1x 10-2 cm2 /V-s. Consistently higher mobilities are obtained when the F8T2 semiconductor makes contact with PEDOT/PSS versus gold electrodes. Alignment of F8T2 on a rubbed polyimide substrate is maintained after quenching, as determined by measurement of the dichroic ratios. Early-stage results on the development of inks based on F8T2 polyfluorene are also reported.

  7. Chemistry and electronic properties of ferromagnetic metal-organic semiconductor interfaces: Fe on CuPc

    Energy Technology Data Exchange (ETDEWEB)

    Aristov, V.Yu. [IFW Dresden, 01069 Dresden (Germany); Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow distr., 142432 (Russian Federation); Molodtsova, O.V.; Knupfer, M. [IFW Dresden, 01069 Dresden (Germany); Ossipyan, Yu.A. [Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow distr., 142432 (Russian Federation); Doyle, B.P. [TASC-INFM Laboratory, Area Science Park - Basovizza, 34012 Trieste (Italy); Department of Physics, University of Johannesburg, PO Box 524, Auckland Park, 2006 (South Africa); Nannarone, S. [TASC-INFM Laboratory, Area Science Park - Basovizza, 34012 Trieste (Italy); Dipartimento di Ingegneria dei Materiali ed Amb., Universita di Modena e Reggio Emilia (Italy)

    2009-12-15

    The chemistry and electronic properties of the interfaces formed between the ferromagnetic metal (Fe) and the model organic semiconductor copper phthalocyanine are investigated in ultra-high vacuum conditions for the case of metal deposition onto the organic molecular thin film. The studies were performed by means of core-level and valence-band high-resolution photoemission electron spectroscopy (PES) as well as near-edge X-ray absorption fine structure using synchrotron radiation. Metal overlayer formation on the top of the organic semiconductor was observed without substantial penetration of deposited metal species into the organic film. At the thin interface layer the ferromagnetic metal shows strong chemical interaction with the nitrogen and carbon of the organic films. Moreover, our results infer that, as a consequence of Fe deposition onto CuPc, central copper atoms of the organic molecules at the interface are reduced from Cu(II) to Cu(I), while Fe atoms are oxidized and/or the ferromagnetic metal replaces this central Cu atom. Further optimization of such an interface is thus required to allow and/or facilitate the injection of spin-polarized carriers into organic semiconductors. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  8. Trap healing and ultralow-noise Hall effect at the surface of organic semiconductors.

    Science.gov (United States)

    Lee, B; Chen, Y; Fu, D; Yi, H T; Czelen, K; Najafov, H; Podzorov, V

    2013-12-01

    Fundamental studies of intrinsic charge transport properties of organic semiconductors are often hindered by charge traps associated with static disorder present even in optimized single-crystal devices. Here, we report a method of surface functionalization using an inert non-conjugated polymer, perfluoropolyether (PFPE), deposited at the surface of organic molecular crystals, which results in accumulation of mobile holes and a 'trap healing' effect at the crystal/PFPE interface. As a consequence, a remarkable ultralow-noise, trp-free conduction regime characterized by intrinsic mobility and transport anisotropy emerges in organic single crystals, and Hall effect measurements with an unprecedented signal-to-noise ratio are demonstrated. This general method to convert trap-dominated organic semiconductors to intrinsic systems may enable the determination of intrinsic transport parameters with high accuracy and make Hall effect measurements in molecular crystals ubiquitous.

  9. Solution-printed organic semiconductor blends exhibiting transport properties on par with single crystals.

    Science.gov (United States)

    Niazi, Muhammad R; Li, Ruipeng; Qiang Li, Er; Kirmani, Ahmad R; Abdelsamie, Maged; Wang, Qingxiao; Pan, Wenyang; Payne, Marcia M; Anthony, John E; Smilgies, Detlef-M; Thoroddsen, Sigurdur T; Giannelis, Emmanuel P; Amassian, Aram

    2015-11-23

    Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm(2) V(-1) s(-1), low threshold voltages ofcrystallization can yield solution-printed polycrystalline organic semiconductor films with transport properties and other figures of merit on par with their single-crystal counterparts.

  10. Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Chang-Hwan Kim

    2003-12-12

    Organic electronic materials are a new class of emerging materials. Organic light emitting devices (OLEDs) are the most promising candidates for future flat panel display technologies. The photophysical characterization is the basic research step one must follow to understand this new class of materials and devices. The light emission properties are closely related to the transport properties of these materials. The objective of this dissertation is to probe the relation between transport and photophysical properties of organic semiconductors. The transport characteristics were evaluated by using thermally stimulated current and thermally stimulated luminescence techniques. The photoluminescence detected magnetic resonance and photoluminescence quantum yield studies provide valuable photophysical information on this class of materials. OLEDs are already in the market. However, detailed studies on the degradation mechanisms are still lacking. Since both optically detected magnetic resonance and thermal activation spectroscopy probe long-lived defect-related states in organic semiconductors, the combined study generates new insight on the OLED operation and degradation mechanisms.

  11. Direct top-down fabrication of nanoscale electrodes for organic semiconductors using fluoropolymer resists

    OpenAIRE

    PARK, J.; Ho, J; Yun, H; Park, M.; Lee, J. H.; Seo, M.; Campbell, Eleanor E. B.; Lee, C; Pyo, S.; Lee, Sangwook

    2013-01-01

    We report the use of a fluoropolymer resist for the damage-free e-beam lithographic patterning of organic semiconductors. The same material is also shown to be suitable as an orthogonal electron beam resist for the patterning of top-contact electrodes on organic thin films. We demonstrate this by characterizing pentacene field effect transistors with feature sizes as small as 100 nm and compare the performance of bottom- and top-contacted devices.

  12. Spin Coulomb Dragging Inhibition of Spin-Polarized Electric Current Injecting into Organic Semiconductors

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun-Qing; QIAO Shi-Zhu; JIA Zhen-Feng; ZHANG Ning-Yu; JI Yan-Ju; PANG Yan-Tao; CHEN Ying; FU Gang

    2008-01-01

    @@ We introduce a one-dimensional spin injection structure comprising a ferromagnetic metal and a nondegenerate organic semiconductor to model electric current polarizations.With this model we analyse spin Coulomb dragging (SCD) effects on the polarization under various electric fields, interface and conductivity conditions.The results show that the SCD inhibits the current polarization.Thus the SCD inhibition should be well considered for accurate evaluation of current polarization in the design of organic spin devices.

  13. Nanoimprinted organic semiconductor laser pumped by a light-emitting diode.

    Science.gov (United States)

    Tsiminis, Georgios; Wang, Yue; Kanibolotsky, Alexander L; Inigo, Anto R; Skabara, Peter J; Samuel, Ifor D W; Turnbull, Graham A

    2013-05-28

    An organic semiconductor laser, simply fabricated by UV-nanoimprint lithography (UV-NIL), that is pumped with a pulsed InGaN LED is demonstrated. Molecular weight optimization of the polymer gain medium on a nanoimprinted polymer distributed feedback resonator enables the lowest reported UV-NIL laser threshold density of 770 W cm(-2) , establishing the potential for scalable organic laser fabrication compatible with mass-produced LEDs.

  14. Photogeneration and enhanced charge transport in aligned smectic liquid crystalline organic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Sanjoy; Ellman, Brett, E-mail: bellman@kent.edu [Department of Physics, Kent State University, Kent, Ohio 44242 (United States); Tripathi, Suvagata; Twieg, Robert J. [Department of Chemistry, Kent State University, Kent, Ohio 44242 (United States)

    2015-10-07

    Liquid crystalline organic semiconductors are emerging candidates for applications in electronic and photonic devices. One of the most attractive aspects of such materials is the potential, in principle, to easily control and manipulate the molecular alignment of the semiconductor over large length scales. Here, we explore the consequences of alignment in a model smectic liquid crystalline semiconductor, and find that the photogeneration efficiency is a strong function of incident polarization in aligned samples. A straightforward theory shows that such behavior is a general feature of aligned materials, regardless of the details of photophysics. Furthermore, we uncover tentative evidence that the mobility of aligned samples is substantially enhanced. Both of these phenomena are of significant technological importance.

  15. Metal-organic semiconductor interfacial barrier height determination from internal photoemission signal in spectral response measurements

    Science.gov (United States)

    Kumar, Sandeep; Iyer, S. Sundar Kumar

    2017-04-01

    Accurate and convenient evaluation methods of the interfacial barrier ϕb for charge carriers in metal semiconductor (MS) junctions are important for designing and building better opto-electronic devices. This becomes more critical for organic semiconductor devices where a plethora of molecules are in use and standardised models applicable to myriads of material combinations for the different devices may have limited applicability. In this paper, internal photoemission (IPE) from spectral response (SR) in the ultra-violet to near infra-red range of different MS junctions of metal-organic semiconductor-metal (MSM) test structures is used to determine more realistic MS ϕb values. The representative organic semiconductor considered is [6, 6]-phenyl C61 butyric acid methyl ester, and the metals considered are Al and Au. The IPE signals in the SR measurement of the MSM device are identified and separated before it is analysed to estimate ϕb for the MS junction. The analysis of IPE signals under different bias conditions allows the evaluation of ϕb for both the front and back junctions, as well as for symmetric MSM devices.

  16. Effects of Exposure to Semiconductor Nanoparticles on Aquatic Organisms

    Directory of Open Access Journals (Sweden)

    Kenton Leigh

    2012-01-01

    Full Text Available Because of their unique physical, optical, and mechanical properties, nanomaterials hold great promise in improving on a wide variety of current technologies. Consequently, their use in research and consumer products is increasing rapidly, and contamination of the environment with various nanomaterials seems inevitable. Because surface waters receive pollutants and contaminants from many sources including nanoparticles and act as reservoirs and conduits for many environmental contaminants, understanding the potential impacts of nanoparticles on the organisms within these environments is critical to evaluating their potential toxicity. While there is much to be learned about interactions between nanomaterials and aquatic systems, there have been a number of recent reports of interactions of quantum dots (QDs with aquatic environments and aquatic organisms. This review is focused on providing a summary of recent work investigating the impacts of quantum dots on aquatic organisms.

  17. Bilayer polymer/oxide coating for electroluminescent organic semiconductors

    DEFF Research Database (Denmark)

    Tavares, Luciana

    Organic materials have been given much attention due to their intriguing properties that can be tailored via synthetic chemistry for specific applications combined with their low price and fairly straight-forward large-scale synthesis. Para-hexaphenylene (p6P) nanofibers emit polarized light...... of the fibers with oxygen. We have developed a bilayer coating that does not change significantly the p6P spectrum but strongly reduces bleaching. This bilayer coating consists of a first layer of a stable polymer (PMMA) on top of the organic nanofibers as a protecting layer for avoiding modifications of the p6...

  18. Bilayer polymer/oxide coating for organic semiconductors

    DEFF Research Database (Denmark)

    Tavares, Luciana; Kjelstrup-Hansen, Jakob; Rubahn, Horst-Günter

    Organic materials have been given much attention due to their intriguing properties that can be tailored via synthetic chemistry for specific applications combined with their low price and fairly straight-forward large-scale synthesis. p6P nanofibers can emit polarized light with a highly...... not interfere with the luminescence spectrum from the p6P but it is also not effective in stopping the bleaching. On the other hand, the use of a nonreactant and stable polymer (PMMA) as a direct contact layer on top of the organic nanofibers works as a protecting layer for avoiding modifications of the p6P...

  19. A General Method for Growing Two-Dimensional Crystals of Organic Semiconductors by "Solution Epitaxy".

    Science.gov (United States)

    Xu, Chunhui; He, Ping; Liu, Jie; Cui, Ajuan; Dong, Huanli; Zhen, Yonggang; Chen, Wei; Hu, Wenping

    2016-08-08

    Two-dimensional (2D) crystals of organic semiconductors (2DCOS) have attracted attention for large-area and low-cost flexible optoelectronics. However, growing large 2DCOS in controllable ways and transferring them onto technologically important substrates, remain key challenges. Herein we report a facile, general, and effective method to grow 2DCOS up to centimeter size which can be transferred to any substrate efficiently. The method named "solution epitaxy" involves two steps. The first is to self-assemble micrometer-sized 2DCOS on water surface. The second is epitaxial growth of them into millimeter or centimeter sized 2DCOS with thickness of several molecular layers. The general applicability of this method for the growth of 2DCOS is demonstrated by nine organic semiconductors with different molecular structures. Organic field-effect transistors (OFETs) based on the 2DCOS demonstrated high performance, confirming the high quality of the 2DCOS.

  20. Lewis Acid-Base Chemistry of 7-Azaisoindigo-Based Organic Semiconductors.

    Science.gov (United States)

    Randell, Nicholas M; Fransishyn, Kyle M; Kelly, Timothy L

    2017-07-26

    Low-band-gap organic semiconductors are important in a variety of organic electronics applications, such as organic photovoltaic devices, photodetectors, and field effect transistors. Building on our previous work, which introduced 7-azaisoindigo as an electron-deficient building block for the synthesis of donor-acceptor organic semiconductors, we demonstrate how Lewis acids can be used to further tune the energies of the frontier molecular orbitals. Coordination of a Lewis acid to the pyridinic nitrogen of 7-azaisoindigo greatly diminishes the electron density in the azaisoindigo π-system, resulting in a substantial reduction in the lowest unoccupied molecular orbital (LUMO) energy. This results in a smaller highest occupied molecular orbital-LUMO gap and shifts the lowest-energy electronic transition well into the near-infrared region. Both H(+) and BF3 are shown to coordinate to azaisoindigo and affect the energy of the S0 → S1 transition. A combination of time-dependent density functional theory and UV/vis and (1)H NMR spectroscopic titrations reveal that when two azaisoindigo groups are present and high concentrations of acid are used, both pyridinic nitrogens bind Lewis acids. Importantly, we demonstrate that this acid-base chemistry can be carried out at the solid-vapor interface by exposing thin films of aza-substituted organic semiconductors to vapor-phase BF3·Et2O. This suggests the possibility of using the BF3-bound 7-azaisoindigo-based semiconductors as n-type materials in various organic electronic applications.

  1. Hybrid polaritons in a resonant inorganic/organic semiconductor microcavity

    Energy Technology Data Exchange (ETDEWEB)

    Höfner, M., E-mail: mhoefner@physik.hu-berlin.de; Sadofev, S.; Henneberger, F. [Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr.15, 12489 Berlin (Germany); Kobin, B.; Hecht, S. [Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin (Germany)

    2015-11-02

    We demonstrated the strong coupling regime in a hybrid inorganic-organic microcavity consisting of (Zn,Mg)O quantum wells and ladder-type oligo(p-phenylene) molecules embedded in a polymer matrix. A Fabry-Pérot cavity is formed by an epitaxially grown lower ZnMgO Bragg reflector and a dielectric mirror deposited atop of the organic layer. A clear anticrossing behavior of the polariton branches related to the Wannier-Mott and Frenkel excitons, and the cavity photon mode with a Rabi-splitting reaching 50 meV, is clearly identified by angular-dependent reflectivity measurements at low temperature. By tailoring the structural design, an equal mixing with weights of about 0.3 for all three resonances is achieved for the middle polariton branch at an incidence angle of about 35°.

  2. Bilayer polymer/oxide coating for organic semiconductors

    DEFF Research Database (Denmark)

    Tavares, Luciana; Kjelstrup-Hansen, Jakob; Rubahn, Horst-Günter

    of the nanofibers with oxygen. Operation of devices in vacuum is a solution but the equipment necessary makes impossible the manufacturing of the devices so we propose the use of a coating for reducing bleaching. It is observed that spin-coated PMMA do not damage the morphology of the fragile nanofibers and also do...... not interfere with the luminescence spectrum from the p6P but it is also not effective in stopping the bleaching. On the other hand, the use of a nonreactant and stable polymer (PMMA) as a direct contact layer on top of the organic nanofibers works as a protecting layer for avoiding modifications of the p6P...

  3. Organic semiconductors as real-time radiation detectors

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, T., E-mail: tsuzuki@hep.sc.niigata-u.ac.jp [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan); Miyata, H., E-mail: miyata@hep.sc.niigata-u.ac.jp [Department of Physics, Niigata University, Niigata 950-2181 (Japan); Katsumata, M. [Department of Physics, Niigata University, Niigata 950-2181 (Japan); Nakano, S.; Matsuda, K. [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan); Tamura, M. [Carlit Holdings Co., Ltd., Tokyo 104-0031 (Japan)

    2014-11-01

    In this study, the possibility of using π-conjugated organic semiconducting polymers as real-time radiation detectors was explored. Polyaniline (PAni) was used to fabricate radiation sensors because of its relative long-term stability in air. Each fabricated sensor was then subjected to irradiation by α- and β-particles, and the real-time response was measured. The multichannel analyzer (MCA) data of the response signal for each irradiation was acquired and the detection efficiency, relative to the electrode bias voltage of the detector, was extracted.

  4. Monte Carlo simulations of charge transport in heterogeneous organic semiconductors

    Science.gov (United States)

    Aung, Pyie Phyo; Khanal, Kiran; Luettmer-Strathmann, Jutta

    2015-03-01

    The efficiency of organic solar cells depends on the morphology and electronic properties of the active layer. Research teams have been experimenting with different conducting materials to achieve more efficient solar panels. In this work, we perform Monte Carlo simulations to study charge transport in heterogeneous materials. We have developed a coarse-grained lattice model of polymeric photovoltaics and use it to generate active layers with ordered and disordered regions. We determine carrier mobilities for a range of conditions to investigate the effect of the morphology on charge transport.

  5. A gated four probe technique for field effect measurements on disordered organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Hauff, E. von; Spethmann, N.; Parisi, J. [Carl von Ossietzky Univ. of Oldenburg (Germany). Dept. for Energy and Semiconductor Research

    2008-09-15

    A gated four probe measurement technique to isolate contact resistances in field effect measurements on disordered organic semiconductors was investigated. Organic field effect transistors (OFETs) were prepared with two additional electrodes in the contact geometry protruding into the source-drain channel to monitor the variation in potential across the channel. Two high impedance electrometers were used to determine the potential at the contacts. This technique allows to directly determine the magnitude of the parasitic contact resistances between metal contact and organic semiconductor from the drop in potential at the contact regions. The effects of contact resistances, which can falsify measurements on bulk transport parameters such as the field effect mobility, can be then eliminated during material characterization. Additionally, the temperature and electric field dependence of the contact resistances offers valuable information about the charge injection and extraction processes between metal and organic semiconductor. The effects of the four probe geometry, specifically the effect of the channel electrodes on the current-voltage characteristics, of hole transport in a polythiophene (P3HT) OFET with Au contacts were investigated and found not to influence device performance, except at currents <<1 nA. The IV characteristics were shown to follow the expected FET behaviour. From the variation in potential along the channel it was found that contact resistances at the source contact (charge injecting contact) are minimal while contact resistances at the drain contact (charge extracting contact) are significant, resulting in a much lower effective source-drain voltage than that applied to the device. (orig.)

  6. Thermionic emission and tunneling at carbon nanotube-organic semiconductor interface.

    Science.gov (United States)

    Sarker, Biddut K; Khondaker, Saiful I

    2012-06-26

    We study the charge carrier injection mechanism across the carbon nanotube (CNT)-organic semiconductor interface using a densely aligned carbon nanotube array as electrode and pentacene as organic semiconductor. The current density-voltage (J-V) characteristics measured at different temperatures show a transition from a thermal emission mechanism at high temperature (above 200 K) to a tunneling mechanism at low temperature (below 200 K). A barrier height of ∼0.16 eV is calculated from the thermal emission regime, which is much lower compared to the metal/pentacene devices. At low temperatures, the J-V curves exhibit a direct tunneling mechanism at low bias, corresponding to a trapezoidal barrier, while at high bias the mechanism is well described by Fowler-Nordheim tunneling, which corresponds to a triangular barrier. A transition from direct tunneling to Fowler-Nordheim tunneling further signifies a small injection barrier at the CNT/pentacene interface. Our results presented here are the first direct experimental evidence of low charge carrier injection barrier between CNT electrodes and an organic semiconductor and are a significant step forward in realizing the overall goal of using CNT electrodes in organic electronics.

  7. To the theory of hybrid organics/semiconductor nanostructures in microcavity

    Science.gov (United States)

    Dubovskiy, O. A.; Agranovich, V. M.

    2017-02-01

    We consider the hybrid structure in microcavity where the energy of Frenkel exciton in organic layer is equal to the energy of Wannier - Mott exciton in semiconductor quantum well (QW). The exciton located in QW of semiconductor layer can interact with molecules of organic layer and under influence of this interaction can change the position jumping and exciting one of organic molecules. The exciton located in molecule of organic layer also can change the position jumping to semiconductor QW. The number of such jumps depends on the intensity of interaction. In the paper we consider the influence of direct Coulomb dipole-dipole interaction and indirect interaction through the optical field of microcavity on the kinetics of excitation. It was shown that the dispersion of hybrid states are modified by Coulomb interaction particularly when the distance between layers is enough small. The lowest branch of dispersion curves with deep minimum at nonzero wave vector may be useful in the studies of the condensation of low energy hybrid excitations.

  8. Discotic liquid crystals: a new generation of organic semiconductors.

    Science.gov (United States)

    Sergeyev, Sergey; Pisula, Wojciech; Geerts, Yves Henri

    2007-12-01

    Discotic (disc-like) molecules typically comprising a rigid aromatic core and flexible peripheral chains have been attracting growing interest because of their fundamental importance as model systems for the study of charge and energy transport and due to the possibilities of their application in organic electronic devices. This critical review covers various aspects of recent research on discotic liquid crystals, in particular, molecular design concepts, supramolecular structure, processing into ordered thin films and fabrication of electronic devices. The chemical structure of the conjugated core of discotic molecules governs, to a large extent, their intramolecular electronic properties. Variation of the peripheral flexible chains and of the aromatic core is decisive for the tuning of self-assembly in solution and in bulk. Supramolecular organization of discotic molecules can be effectively controlled by the choice of the processing methods. In particular, approaches to obtain suitable macroscopic orientations of columnar superstructures on surfaces, that is, planar uniaxial or homeotropic alignment, are discussed together with appropriate processing techniques. Finally, an overview of charge transport in discotic materials and their application in optoelectronic devices is given.

  9. Low-Programmable-Voltage Nonvolatile Memory Devices Based on Omega-shaped Gate Organic Ferroelectric P(VDF-TrFE) Field Effect Transistors Using p-type Silicon Nanowire Channels

    Institute of Scientific and Technical Information of China (English)

    Ngoc Huynh Van; Jae-Hyun Lee; Dongmok Whang; Dae Joon Kang

    2015-01-01

    A facile approach was demonstrated for fabricating high-performance nonvolatile memory devices based on ferroelectric-gate field effect transistors using a p-type Si nanowire coated with omega-shaped gate organic ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)). We overcame the interfacial layer problem by incorporating P(VDF-TrFE) as a ferroelectric gate using a low-temperature fabrication process. Our memory devices exhibited excellent memory characteristics with a low programming voltage of ±5 V, a large modulation in channel conductance between ON and OFF states exceeding 105, a long retention time greater than 3 9 104 s, and a high endurance of over 105 programming cycles while maintaining an ION/IOFF ratio higher than 102.

  10. Nanophase Engineering of Organic Semiconductor-based Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Ming [ORNL; Keum, Jong Kahk [ORNL; Geohegan, David B [ORNL; Xiao, Kai [ORNL

    2015-01-01

    Organic photovoltaics are promising low-cost, easily-processable energy sources of the future, and are the subject of current academic and industrial interest. In order to achieve the envisioned device efficiencies to surpass commercialization target values, several challenges must be met: (1) to design and synthesize conjugated molecules with low optical bandgaps and optimized electronic energy levels, (2) optimization the morphology of donor/acceptor interpenetrating networks by controlling nanoscale phase separation and self-assembly, and (3) precise tuning of the active layer/electrode interfaces and donor/acceptor interfaces for optimized charge transfer. Here, we focus on recent advances in: (i) synthetic strategies for low-bandgap conjugated polymers and novel fullerene acceptors, (ii) processing to tune film morphologies by solvent annealing, thermal annealing, and the use of solvent additives and compatibilizers, and (iii) engineering of active layer/electrode interfaces and donor/acceptor interfaces with self-assembled monolayer dipoles.

  11. Purcell effect in an organic-inorganic halide perovskite semiconductor microcavity system

    Science.gov (United States)

    Wang, Jun; Cao, Runan; Da, Peimei; Wang, Yafeng; Hu, Tao; Wu, Lin; Lu, Jian; Shen, Xuechu; Xu, Fei; Zheng, Gengfeng; Chen, Zhanghai

    2016-01-01

    Organic-inorganic halide perovskite semiconductors with the attractive physics properties, including strong photoluminescence (PL), huge oscillator strengths, and low nonradiative recombination losses, are ideal candidates for studying the light-matter interaction in nanostructures. Here, we demonstrate the coupling of the exciton state and the cavity mode in the lead halide perovskite microcavity system at room temperature. The Purcell effect in the coupling system is clearly observed by using angle-resolved photoluminescence spectra. Kinetic analysis based on time-resolved PL reveals that the spontaneous emission rate of the halide perovskite semiconductor is significantly enhanced at resonance of the exciton energy and the cavity mode. Our results provide the way for developing electrically driven organic polariton lasers, optical devices, and on-chip coherent quantum light sources.

  12. Purcell effect in an organic-inorganic halide perovskite semiconductor microcavity system

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun; Wang, Yafeng; Hu, Tao; Wu, Lin; Shen, Xuechu; Chen, Zhanghai, E-mail: lujian@fudan.edu.cn, E-mail: zhanghai@fudan.edu.cn [State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Cao, Runan; Xu, Fei [Department of Physics, Shanghai University, Shanghai 200444 (China); Da, Peimei; Zheng, Gengfeng [Laboratory of Advanced Materials, Department of Chemistry, Fudan University, Shanghai 200433 (China); Lu, Jian, E-mail: lujian@fudan.edu.cn, E-mail: zhanghai@fudan.edu.cn [State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433 (China); Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210 (China)

    2016-01-11

    Organic-inorganic halide perovskite semiconductors with the attractive physics properties, including strong photoluminescence (PL), huge oscillator strengths, and low nonradiative recombination losses, are ideal candidates for studying the light-matter interaction in nanostructures. Here, we demonstrate the coupling of the exciton state and the cavity mode in the lead halide perovskite microcavity system at room temperature. The Purcell effect in the coupling system is clearly observed by using angle-resolved photoluminescence spectra. Kinetic analysis based on time-resolved PL reveals that the spontaneous emission rate of the halide perovskite semiconductor is significantly enhanced at resonance of the exciton energy and the cavity mode. Our results provide the way for developing electrically driven organic polariton lasers, optical devices, and on-chip coherent quantum light sources.

  13. Phenomenological model for charge dynamics and optical response of disordered systems: application to organic semiconductors

    OpenAIRE

    Fratini, Simone; Ciuchi, Sergio; Mayou, Didier

    2014-01-01

    We provide a phenomenological formula which describes the low-frequency optical absorption of charge carriers in disordered systems with localization. This allows to extract, from experimental data on the optical conductivity, the relevant microscopic parameters determining the transport properties, such as the carrier localization length and the elastic and inelastic scattering times. This general formula is tested and applied here to organic semiconductors, where dynamical molecular disorde...

  14. A scale-bridging modeling approach for anisotropic organic molecules at patterned semiconductor surfaces

    OpenAIRE

    Kleppmann, Nicola; Klapp, Sabine H. L.

    2014-01-01

    Hybrid systems consisting of organic molecules at inorganic semiconductor surfaces are gaining increasing importance as thin film devices for optoelectronics. The efficiency of such devices strongly depends on the collective behavior of the adsorbed molecules. In the present paper we propose a novel, coarse-grained model addressing the condensed phases of a representative hybrid system, that is, para-sexiphenyl (6P) at zinc-oxide (ZnO). Within our model, intermolecular interactions are repre-...

  15. A hybrid organic semiconductor/silicon photodiode for efficient ultraviolet photodetection.

    Science.gov (United States)

    Levell, J W; Giardini, M E; Samuel, I D W

    2010-02-15

    A method employing conjugated polymer thin film blends is shown to provide a simple and convenient way of greatly enhancing the ultraviolet response of silicon photodetectors. Hybrid organic semiconductor/silicon photodetectors are demonstrated using fluorene copolymers and give a quantum efficiency of 60% at 200 nm. The quantum efficiency is greater than 34% over the entire 200-620 nm range. These devices show promise for use in high sensitivity, low cost UV-visible photodetection and imaging applications.

  16. Rational design of organic semiconductors for texture control and self-patterning on halogenated surfaces

    KAUST Repository

    Ward, Jeremy W.

    2014-05-15

    Understanding the interactions at interfaces between the materials constituting consecutive layers within organic thin-film transistors (OTFTs) is vital for optimizing charge injection and transport, tuning thin-film microstructure, and designing new materials. Here, the influence of the interactions at the interface between a halogenated organic semiconductor (OSC) thin film and a halogenated self-assembled monolayer on the formation of the crystalline texture directly affecting the performance of OTFTs is explored. By correlating the results from microbeam grazing incidence wide angle X-ray scattering (μGIWAXS) measurements of structure and texture with OTFT characteristics, two or more interaction paths between the terminating atoms of the semiconductor and the halogenated surface are found to be vital to templating a highly ordered morphology in the first layer. These interactions are effective when the separating distance is lower than 2.5 dw, where dw represents the van der Waals distance. The ability to modulate charge carrier transport by several orders of magnitude by promoting "edge-on" versus "face-on" molecular orientation and crystallographic textures in OSCs is demonstrated. It is found that the "edge-on" self-assembly of molecules forms uniform, (001) lamellar-textured crystallites which promote high charge carrier mobility, and that charge transport suffers as the fraction of the "face-on" oriented crystallites increases. The role of interfacial halogenation in mediating texture formation and the self-patterning of organic semiconductor films, as well as the resulting effects on charge transport in organic thin-film transistors, are explored. The presence of two or more anchoring sites between a halogenated semiconductor and a halogenated self-assembled monolayer, closer than about twice the corresponding van der Waals distance, alter the microstructure and improve electrical properties. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains

    KAUST Repository

    Diao, Ying

    2013-06-02

    Solution coating of organic semiconductors offers great potential for achieving low-cost manufacturing of large-area and flexible electronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of thin-film morphology. Here, we report an approach - termed fluid-enhanced crystal engineering (FLUENCE) - that allows for a high degree of morphological control of solution-printed thin films. We designed a micropillar-patterned printing blade to induce recirculation in the ink for enhancing crystal growth, and engineered the curvature of the ink meniscus to control crystal nucleation. Using FLUENCE, we demonstrate the fast coating and patterning of millimetre-wide, centimetre-long, highly aligned single-crystalline organic semiconductor thin films. In particular, we fabricated thin films of 6,13-bis(triisopropylsilylethynyl) pentacene having non-equilibrium single-crystalline domains and an unprecedented average and maximum mobilities of 8.1±1.2 cm2 V-1 s -1 and 11 cm2 V-1 s-1. FLUENCE of organic semiconductors with non-equilibrium single-crystalline domains may find use in the fabrication of high-performance, large-area printed electronics. © 2013 Macmillan Publishers Limited. All rights reserved.

  18. Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains.

    Science.gov (United States)

    Diao, Ying; Tee, Benjamin C-K; Giri, Gaurav; Xu, Jie; Kim, Do Hwan; Becerril, Hector A; Stoltenberg, Randall M; Lee, Tae Hoon; Xue, Gi; Mannsfeld, Stefan C B; Bao, Zhenan

    2013-07-01

    Solution coating of organic semiconductors offers great potential for achieving low-cost manufacturing of large-area and flexible electronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of thin-film morphology. Here, we report an approach--termed fluid-enhanced crystal engineering (FLUENCE)--that allows for a high degree of morphological control of solution-printed thin films. We designed a micropillar-patterned printing blade to induce recirculation in the ink for enhancing crystal growth, and engineered the curvature of the ink meniscus to control crystal nucleation. Using FLUENCE, we demonstrate the fast coating and patterning of millimetre-wide, centimetre-long, highly aligned single-crystalline organic semiconductor thin films. In particular, we fabricated thin films of 6,13-bis(triisopropylsilylethynyl) pentacene having non-equilibrium single-crystalline domains and an unprecedented average and maximum mobilities of 8.1±1.2 cm(2) V(-1) s(-1) and 11 cm(2) V(-1) s(-1). FLUENCE of organic semiconductors with non-equilibrium single-crystalline domains may find use in the fabrication of high-performance, large-area printed electronics.

  19. Solution coating of large-area organic semiconductor thin films with aligned single-crystalline domains

    Science.gov (United States)

    Diao, Ying; Tee, Benjamin C.-K.; Giri, Gaurav; Xu, Jie; Kim, Do Hwan; Becerril, Hector A.; Stoltenberg, Randall M.; Lee, Tae Hoon; Xue, Gi; Mannsfeld, Stefan C. B.; Bao, Zhenan

    2013-07-01

    Solution coating of organic semiconductors offers great potential for achieving low-cost manufacturing of large-area and flexible electronics. However, the rapid coating speed needed for industrial-scale production poses challenges to the control of thin-film morphology. Here, we report an approach—termed fluid-enhanced crystal engineering (FLUENCE)—that allows for a high degree of morphological control of solution-printed thin films. We designed a micropillar-patterned printing blade to induce recirculation in the ink for enhancing crystal growth, and engineered the curvature of the ink meniscus to control crystal nucleation. Using FLUENCE, we demonstrate the fast coating and patterning of millimetre-wide, centimetre-long, highly aligned single-crystalline organic semiconductor thin films. In particular, we fabricated thin films of 6,13-bis(triisopropylsilylethynyl) pentacene having non-equilibrium single-crystalline domains and an unprecedented average and maximum mobilities of 8.1±1.2 cm2 V-1 s-1 and 11 cm2 V-1 s-1. FLUENCE of organic semiconductors with non-equilibrium single-crystalline domains may find use in the fabrication of high-performance, large-area printed electronics.

  20. Charge-carrier relaxation in disordered organic semiconductors studied by dark injection: Experiment and modeling

    Science.gov (United States)

    Mesta, M.; Schaefer, C.; de Groot, J.; Cottaar, J.; Coehoorn, R.; Bobbert, P. A.

    2013-11-01

    Understanding of stationary charge transport in disordered organic semiconductors has matured during recent years. However, charge-carrier relaxation in nonstationary situations is still poorly understood. Such relaxation can be studied in dark injection experiments, in which the bias applied over an unilluminated organic semiconductor device is abruptly increased. The resulting transient current reveals both charge-carrier transport and relaxation characteristics. We performed such experiments on hole-only devices of a polyfluorene-based organic semiconductor. Modeling the dark injection by solving a one-dimensional master equation using the equilibrium carrier mobility leads to a too-slow current transient, since this approach does not account for carrier relaxation. Modeling by solving a three-dimensional time-dependent master equation does take into account all carrier transport and relaxation effects. With this modeling, the time scale of the current transient is found to be in agreement with experiment. With a disorder strength somewhat smaller than extracted from the temperature-dependent stationary current-voltage characteristics, also the shape of the experimental transients is well described.

  1. In Situ Fabrication of ZnS Semiconductor Nanoparticles in Layered Organic-inorganic Solid Template

    Institute of Scientific and Technical Information of China (English)

    Bao Lin ZHU; Xiao CHEN; Zhen Ming SUI; Li Mei XU; Chun Jie YANG; Ji Kuan ZHAO; Jie LIU

    2004-01-01

    Ordered ZnS semiconductor nanoparticles were in situ synthesized in metal halide perovskite organic/inorganic layered hybrids (CnH2n+1NH3)2ZnCl4 (n=10 and 12) by reaction of their spin-casting films with H2S gas. Transmission electron microscopy, UV-vis spectroscopy and small-angle X-ray diffraction were used to characterize the morphology and the structure of formed nanoparticles. Obtained results indicate an effective way to incorporate functional inorganic nanoparticles into structured organic matrices.

  2. Integrated Materials Design of Organic Semiconductors for Field-Effect Transistors

    KAUST Repository

    Mei, Jianguo

    2013-05-08

    The past couple of years have witnessed a remarkable burst in the development of organic field-effect transistors (OFETs), with a number of organic semiconductors surpassing the benchmark mobility of 10 cm2/(V s). In this perspective, we highlight some of the major milestones along the way to provide a historical view of OFET development, introduce the integrated molecular design concepts and process engineering approaches that lead to the current success, and identify the challenges ahead to make OFETs applicable in real applications. © 2013 American Chemical Society.

  3. Microscopic modeling of magnetic-field effects on charge transport in organic semiconductors

    Science.gov (United States)

    Schellekens, A. J.; Wagemans, W.; Kersten, S. P.; Bobbert, P. A.; Koopmans, B.

    2011-08-01

    The stochastic Liouville equation is applied to the field of organic magnetoresistance to perform detailed microscopic calculations on the different proposed models. By adapting this equation, the influence of a magnetic field on the current in bipolaron, electron-hole pair, and triplet models is calculated. The simplicity and wide applicability of the stochastic Liouville equation makes it a powerful tool for interpreting experimental results on magnetoresistance measurements in organic semiconductors. New insights are gained on the influence of hopping rates and disorder on the magnetoresistance.

  4. Bidirectional communication in an HF hybrid organic/solution-processed metal-oxide RFID tag

    NARCIS (Netherlands)

    Myny, K.; Rockelé, M.; Chasin, A.; Pham, D.-V.; Steiger, J.; Botnaras, S.; Weber, D.; Herold, B.; Ficker, J.; Putten, B. van der; Gelinck, G.H.; Genoe, J.; Dehaene, W.; Heremans, P.

    2012-01-01

    The ambition of printing item-level RFID tags is one of the driving forces behind printed electronics research. Organic RFID tags have been shown, initially using p-type organic semiconductors [1-4]. The introduction of n-type organic semiconductors with reasonable performance made organic CMOS

  5. Bidirectional communication in an HF hybrid organic/solution-processed metal-oxide RFID tag

    NARCIS (Netherlands)

    Myny, K.; Rockelé, M.; Chasin, A.; Pham, D.-V.; Steiger, J.; Botnaras, S.; Weber, D.; Herold, B.; Ficker, J.; Putten, B. van der; Gelinck, G.H.; Genoe, J.; Dehaene, W.; Heremans, P.

    2012-01-01

    The ambition of printing item-level RFID tags is one of the driving forces behind printed electronics research. Organic RFID tags have been shown, initially using p-type organic semiconductors [1-4]. The introduction of n-type organic semiconductors with reasonable performance made organic CMOS conc

  6. Organic analogues of diluted magnetic semiconductors: bridging quantum chemistry to condensed matter physics

    Science.gov (United States)

    Furis, Madalina; Rawat, Naveen; Cherian, Judy G.; Wetherby, Anthony; Waterman, Rory; McGill, Stephen

    2015-09-01

    The selective coupling between polarized photons and electronic states in materials enables polarization-resolved spectroscopy studies of exchange interactions, spin dynamics, and collective magnetic behavior of conduction electrons in semiconductors. Here we report on Magnetic Circular Dichroism (MCD) studies of magnetic properties of electrons in crystalline thin films of small molecule organic semiconductors. Specifically, the focus was on the magnetic exchange interaction properties of d-shell ions (Cu2+, Co2+ and Mn2+) metal phthalocyanine (Pc) thin films that one may think of as organic analogues of diluted magnetic semiconductors (DMS). These films were deposited in-house using a recently developed pen-writing method that results in crystalline films with macroscopic long range ordering and improved electronic properties, ideally suited for spectroscopy techniques. Our experiments reveal that, in analogy to DMS, the extended π-orbitals of the Pc molecule mediate the spin exchange between highly localized d-like unpaired spins. We established that exchange mechanisms involve different electronic states in each species and/or hybridization between d-like orbitals and certain delocalized π-orbitals. Unprecedented 25T MCD and PL conducted in the unique 25T Split Florida HELIX magnet at the National High Magnetic Field Laboratory (NHMFL) will prove useful in probing these exchange interactions.

  7. Theory of coupled hybrid inorganic/organic systems: Excitation transfer at semiconductor/molecule interfaces

    Science.gov (United States)

    Specht, Judith; Verdenhalven, Eike; Theuerholz, Sverre; Knorr, Andreas; Richter, Marten

    2016-03-01

    We derive a theoretical framework for describing hybrid organic-inorganic systems consisting of an ordered organic molecular layer coupled to a semiconductor quantum well (e.g., ZnO). A Heisenberg equation of motion technique based on a density matrix formalism is applied to derive dynamical equations for the composite system on a mesoscopic scale. Our theoretical approach focuses on the inuence of nonradiative Förster excitation transfer across the hybrid interface on linear optical absorption spectra. Therefore, the dielectric screening is discussed at the interface of two materials with different dielectric constants. Moreover, the Förster transfer matrix element is calculated in the point-dipole approximation. For a consistent theoretical description of both constituents (i.e., the molecular layer and the semiconductor substrate), the problem is treated in momentum space. Solving the equations of motion for the microscopic polarizations in frequency space directly leads to an equation for the frequency-dependent linear absorption coefficient. Our theoretical approach forms the basis for studying parameter regimes and geometries with optimized excitation transfer efficiency across the semiconductor/ molecule interface.

  8. Reducing dynamic disorder in small-molecule organic semiconductors by suppressing large-amplitude thermal motions.

    Science.gov (United States)

    Illig, Steffen; Eggeman, Alexander S; Troisi, Alessandro; Jiang, Lang; Warwick, Chris; Nikolka, Mark; Schweicher, Guillaume; Yeates, Stephen G; Henri Geerts, Yves; Anthony, John E; Sirringhaus, Henning

    2016-02-22

    Thermal vibrations and the dynamic disorder they create can detrimentally affect the transport properties of van der Waals bonded molecular semiconductors. The low-energy nature of these vibrations makes it difficult to access them experimentally, which is why we still lack clear molecular design rules to control and reduce dynamic disorder. In this study we discuss the promising organic semiconductors rubrene, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothio-phene and 2,9-di-decyl-dinaphtho-[2,3-b:20,30-f]-thieno-[3,2-b]-thiophene in terms of an exceptionally low degree of dynamic disorder. In particular, we analyse diffuse scattering in transmission electron microscopy, to show that small molecules that have their side chains attached along the long axis of their conjugated core are better encapsulated in their crystal structure, which helps reduce large-amplitude thermal motions. Our work provides a general strategy for the design of new classes of very high mobility organic semiconductors with a low degree of dynamic disorder.

  9. Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Nádaždy, V., E-mail: nadazdy@savba.sk; Gmucová, K. [Institute of Physics SAS, Dúbravská cesta 9, 845 11 Bratislava (Slovakia); Schauer, F. [Faculty of Education, Trnava University in Trnava, 918 43 Trnava (Slovakia); Faculty of Applied Informatics, Tomas Bata University in Zlin, 760 05 Zlin (Czech Republic)

    2014-10-06

    We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bond defect states induced by ultraviolet treatment above the highest occupied molecular orbital in a prototypical σ-conjugated polymer, poly[methyl(phenyl)silylene]. The results agree well with those of our previous DOS reconstruction by post-transient space-charge-limited-current spectroscopy, which was, however, limited to a narrow energy range. In addition, good agreement of the DOS values measured on two common π-conjugated organic polymer semiconductors, polyphenylene vinylene and poly(3-hexylthiophene), with the rather rare previously published data demonstrate the accuracy of the proposed method.

  10. Energy resolved electrochemical impedance spectroscopy for electronic structure mapping in organic semiconductors

    Science.gov (United States)

    Nádaždy, V.; Schauer, F.; Gmucová, K.

    2014-10-01

    We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bond defect states induced by ultraviolet treatment above the highest occupied molecular orbital in a prototypical σ-conjugated polymer, poly[methyl(phenyl)silylene]. The results agree well with those of our previous DOS reconstruction by post-transient space-charge-limited-current spectroscopy, which was, however, limited to a narrow energy range. In addition, good agreement of the DOS values measured on two common π-conjugated organic polymer semiconductors, polyphenylene vinylene and poly(3-hexylthiophene), with the rather rare previously published data demonstrate the accuracy of the proposed method.

  11. Spin Entangling Effects of Electron and Nucleus on Hopping Transfer in Organic Semiconductors

    Science.gov (United States)

    Zhao, Jun-Qing; Sun, Ling-Ling; Wang, Ting

    2016-05-01

    To study the spin entangling effects on organic magneto-resistance in organic semiconductors, we focused on the entanglement-related hopping transfer of electrons on the basis of the Miller-Abrahams hopping rate. Considering spin entanglement of localized electron with the nucleus in the hopping process, we deduced an attempt hopping rate of electrons as a function of the applied magnetic field and the localized hyperfine interaction, and thus established a model to calculate the organic magneto-resistance. The calculated results show that the magneto-resistance has a maximum in the lower magnetic field, and the corresponding magnetic field Bmax increases with the hyperfine interaction. In the higher magnetic field, the magneto-resistance tends to a negative saturation value. This analysis will be an valuable reference for deep understanding of the organic magneto-resistance.

  12. Organic Semiconductors and Nanodielectrics for Flexible, Low Voltage Thin-Film Transistors

    Science.gov (United States)

    Marks, Tobin

    2006-03-01

    Molecular materials scientists are skilled at designing and constructing individual molecules with the goal of imbuing them with predetermined chemical and physical properties. However, the subsequent task of rationally assembling them into organized, functional supramolecular architectures with precise, nanometer-level control of bulk opt-electronic properties presents another level of challenge. In this lecture, synthetic and computational approaches to addressing such problems are described in which the ultimate goal is the fabrication of flexible electronic circuits employing unconventional materials classes and unconventional fabrication techniques. The issues here concern not only the rational design, realization, and understanding of high-mobility p- and n-type organic semiconductors, but also robust enabling nanoscopic gate dielectrics having ultra-high capacitance, low leakage, and high breakdown fields. In the former area, routes to and properties of, new high-mobility heterocyclic materials are described. These materials are then used to fabricate high-performance organic thin film transistors and CMOS circuits. In the latter topic, the design, synthesis, and characterization of new high-k nanoscopic gate dielectrics are described. It is then shown how these dielectrics can be employed to significantly enhance the performance of thin-film transistors and other devices fabricated from a wide variety of both organic as well as inorganic semiconductors.

  13. Solution-printed organic semiconductor blends exhibiting transport properties on par with single crystals

    KAUST Repository

    Niazi, Muhammad R.

    2015-11-23

    Solution-printed organic semiconductors have emerged in recent years as promising contenders for roll-to-roll manufacturing of electronic and optoelectronic circuits. The stringent performance requirements for organic thin-film transistors (OTFTs) in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require performance currently achieved by organic single-crystal devices, but these suffer from scale-up challenges. Here we present a new method based on blade coating of a blend of conjugated small molecules and amorphous insulating polymers to produce OTFTs with consistently excellent performance characteristics (carrier mobility as high as 6.7 cm2 V−1 s−1, low threshold voltages of<1 V and low subthreshold swings <0.5 V dec−1). Our findings demonstrate that careful control over phase separation and crystallization can yield solution-printed polycrystalline organic semiconductor films with transport properties and other figures of merit on par with their single-crystal counterparts.

  14. Investigation of organic semiconductor interlayers in hybrid PEDOT:PSS/silicon solar cells

    Science.gov (United States)

    Weingarten, Martin; Zweipfennig, Thorsten; Sanders, Simon; Stümmler, Dominik; Pfeiffer, Pascal; Vescan, Andrei; Kalisch, Holger

    2016-10-01

    In the last years, hybrid organic/inorganic solar cells have attracted great interest in photovoltaic research due to their expected potential to combine the advantages of both material classes, the excellent electrical properties and stability of the inorganic and the low-cost processability of the organic semiconductors. This work is focused on hybrid solar cells based on n-doped crystalline Si as the inorganic and the polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) as the organic part of the device. The hole-conducting organic semiconductors poly(3-hexylthiophene-2,5-diyl) (P3HT) and 2,2‧,7,7‧-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9‧-spirobifluorene (Spiro-MeOTAD) are investigated as electron blocking interlayers to reduce the parasitic electron current into the metal top contact and thereby increase the efficiency of the solar cell. In this context, P3HT is identified to be insufficient as an interlayer material due to unfavorable hysteresis effects. On the other hand, for solar cells with a Spiro-MeOTAD interlayer, the power conversion efficiency (PCE) is significantly increased. This is mainly attributed to an increased short-circuit current density. For the best performing device, a PCE of 14.3% is achieved, which is one of the highest values reported for this type of hybrid solar cells so far.

  15. Structural Design Principle of Small-Molecule Organic Semiconductors for Metal-Free, Visible-Light-Promoted Photocatalysis.

    Science.gov (United States)

    Wang, Lei; Huang, Wei; Li, Run; Gehrig, Dominik; Blom, Paul W M; Landfester, Katharina; Zhang, Kai A I

    2016-08-01

    Herein, we report on the structural design principle of small-molecule organic semiconductors as metal-free, pure organic and visible light-active photocatalysts. Two series of electron-donor and acceptor-type organic semiconductor molecules were synthesized to meet crucial requirements, such as 1) absorption range in the visible region, 2) sufficient photoredox potential, and 3) long lifetime of photogenerated excitons. The photocatalytic activity was demonstrated in the intermolecular C-H functionalization of electron-rich heteroaromates with malonate derivatives. A mechanistic study of the light-induced electron transport between the organic photocatalyst, substrate, and the sacrificial agent are described. With their tunable absorption range and defined energy-band structure, the small-molecule organic semiconductors could offer a new class of metal-free and visible light-active photocatalysts for chemical reactions.

  16. Simple way to engineer metal-semiconductor interface for enhanced performance of perovskite organic lead iodide solar cells.

    Science.gov (United States)

    Xu, Yuzhuan; Shi, Jiangjian; Lv, Songtao; Zhu, Lifeng; Dong, Juan; Wu, Huijue; Xiao, Yin; Luo, Yanhong; Wang, Shirong; Li, Dongmei; Li, Xianggao; Meng, Qingbo

    2014-04-23

    A thin wide band gap organic semiconductor N,N,N',N'-tetraphenyl-benzidine layer has been introduced by spin-coating to engineer the metal-semiconductor interface in the hole-conductor-free perovskite solar cells. The average cell power conversion efficiency (PCE) has been enhanced from 5.26% to 6.26% after the modification and a highest PCE of 6.71% has been achieved. By the aid of electrochemical impedance spectroscopy and dark current analysis, it is revealed that this modification can increase interfacial resistance of CH3NH3PbI3/Au interface and retard electron recombination process in the metal-semiconductor interface.

  17. Noble metal-free hydrogen-evolving photocathodes based on small molecule organic semiconductors

    Science.gov (United States)

    Morozan, A.; Bourgeteau, T.; Tondelier, D.; Geffroy, B.; Jousselme, B.; Artero, V.

    2016-09-01

    Organic semiconductors have great potential for producing hydrogen in a sustainable and economically-viable manner because they rely on readily available materials with highly tunable properties. We demonstrate here the relevance of heterojunctions to the construction of H2-evolving photocathodes, exclusively based on earth-abundant elements. Boron subnaphthalocyanine chloride proved a very promising acceptor in that perspective. It absorbs a part of the solar spectrum complementary to α-sexithiophene as a donor, thus generating large photocurrents and providing a record onset potential for light-driven H2 evolution under acidic aqueous conditions using a nanoparticulate amorphous molybdenum sulfide catalyst.

  18. Chemical engineering in the electronics industry: progress towards the rational design of organic semiconductor heterojunctions

    KAUST Repository

    Clancy, Paulette

    2012-05-01

    We review the current status of heterojunction design for combinations of organic semiconductor materials, given its central role in affecting the device performance for electronic devices and solar cell applications. We provide an emphasis on recent progress towards the rational design of heterojunctions that may lead to higher performance of charge separation and mobility. We also play particular attention to the role played by computational approaches and its potential to help define the best choice of materials for solar cell development in the future. We report the current status of the field with respect to such goals. © 2012 Elsevier Ltd.

  19. Towards high charge carrier mobilities by rational design of organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Andrienko, Denis; Ruehle, Victor; Baumeier, Bjoern; Vehoff, Thorsten; Lukyanov, Alexander; Kremer, Kurt [Max Planck Institute for Polymer Research, Mainz (Germany); Marcon, Valentina [Technische Universitaet Darmstadt (Germany); Kirkpatrick, James; Nelson, Jenny [Imperial College London (United Kingdom); Lennartz, Christian [BASF AG, Ludwigshafen (Germany)

    2010-07-01

    The role of material morphology on charge carrier mobility in partially disordered organic semiconductors is discussed for several classes of materials: derivatives of hexabenzocoronenens, perylenediimides, triangularly-shaped polyaromatic hydrocarbons, and Alq{sub 3}. Simulations are performed using a package developed by Imperial College, London and Max Planck Institute for Polymer Research, Mainz (votca.org). This package combines several techniques into one scheme: quantum chemical methods for the calculation of molecular electronic structures and reorganization energies; molecular dynamics and systematic coarse-graining approaches for simulation of self-assembly and relative positions and orientations of molecules on large scales; kinetic Monte Carlo and master equation for studies of charge transport.

  20. Ionization sensitization of doping in co-deposited organic semiconductor films

    Energy Technology Data Exchange (ETDEWEB)

    Shinmura, Yusuke, E-mail: shinmura@ims.ac.jp; Yamashina, Yohei; Kaji, Toshihiko; Hiramoto, Masahiro [Institute for Molecular Science, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787, Aichi (Japan); JST, CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan)

    2014-11-03

    Sensitization of the dopant ionization in co-deposited films of organic semiconductors was found. The ionization rate of cesium carbonate (Cs{sub 2}CO{sub 3}), which acts as a donor dopant in single films of metal-free phthalocyanine (H{sub 2}Pc) and fullerene (C{sub 60}), was increased from 10% to 97% in a H{sub 2}Pc:C{sub 60} co-deposited film. A charge separation superlattice model that includes electron transfer from the conduction band of H{sub 2}Pc to that of C{sub 60}, which increases the rate of dopant ionization, is proposed.

  1. High-sensitivity visible-blind UV detectors made with organic semiconductors

    Science.gov (United States)

    Yu, Gang; Cao, Yong; Srdanov, Gordana

    1999-04-01

    High sensitivity visible-blind UV detectors were fabricated with organic semiconductors. The photo-sensitivity at 350 nm reaches 75 mA/Watt, corresponding to quantum efficiency of approximately 27% el/ph. The visible/UV suppression ratio is more than 10(superscript 4) without optical filters. These UV detectors are of linear intensity dependence with fast response time. The simple fabrication process allows these UV detectors to be made in large size, in flexible forms or onto non-planar substrates with low cost. The fabrication process also allows these UV detectors to be integrated with electronic devices or optical devices.

  2. Influence of the semiconductor oxidation potential on the operational stability of organic field-effect transistors

    Science.gov (United States)

    Sharma, A.; Mathijssen, S. G. J.; Bobbert, P. A.; de Leeuw, D. M.

    2011-09-01

    During prolonged application of a gate bias, organic field-effect transistors show a gradual shift of the threshold voltage towards the applied gate bias voltage. The shift follows a stretched-exponential time dependence governed by a relaxation time. Here, we show that a thermodynamic analysis reproduces the observed exponential dependence of the relaxation time on the oxidation potential of the semiconductor. The good fit with the experimental data validates the underlying assumptions. It demonstrates that this operational instability is a straightforward thermodynamically driven process that can only be eliminated by eliminating water from the transistor.

  3. Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors

    Science.gov (United States)

    Matsushima, Toshinori; Sandanayaka, Atula S. D.; Esaki, Yu; Adachi, Chihaya

    2015-09-01

    We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10-2 cm2/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm2/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost.

  4. Modifying the thermal conductivity of small molecule organic semiconductor thin films with metal nanoparticles.

    Science.gov (United States)

    Wang, Xinyu; Parrish, Kevin D; Malen, Jonathan A; Chan, Paddy K L

    2015-11-04

    Thermal properties of organic semiconductors play a significant role in the performance and lifetime of organic electronic devices, especially for scaled-up large area applications. Here we employ silver nanoparticles (Ag NPs) to modify the thermal conductivity of the small molecule organic semiconductor, dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT). The differential 3-ω method was used to measure the thermal conductivity of Ag-DNTT hybrid thin films. We find that the thermal conductivity of pure DNTT thin films do not vary with the deposition temperature over a range spanning 24 °C to 80 °C. The thermal conductivity of the Ag-DNTT hybrid thin film initially decreases and then increases when the Ag volume fraction increases from 0% to 32%. By applying the effective medium approximation to fit the experimental results of thermal conductivity, the extracted thermal boundary resistance of the Ag-DNTT interface is 1.14 ± 0.98 × 10(-7) m(2)-K/W. Finite element simulations of thermal conductivity for realistic film morphologies show good agreement with experimental results and effective medium approximations.

  5. Solution-grown small-molecule organic semiconductor with enhanced crystal alignment and areal coverage for organic thin film transistors

    Directory of Open Access Journals (Sweden)

    Sheng Bi

    2015-07-01

    Full Text Available Drop casting of small-molecule organic semiconductors typically forms crystals with random orientation and poor areal coverage, which leads to significant performance variations of organic thin-film transistors (OTFTs. In this study, we utilize the controlled evaporative self-assembly (CESA method combined with binary solvent system to control the crystal growth. A small-molecule organic semiconductor,2,5-Di-(2-ethylhexyl-3,6-bis(5″-n-hexyl-2,2′,5′,2″]terthiophen-5-yl-pyrrolo[3,4-c]pyrrole-1,4-dione (SMDPPEH, is used as an example to demonstrate the effectiveness of our approach. By optimizing the double solvent ratios, well-aligned SMDPPEH crystals with significantly improved areal coverage were achieved. As a result, the SMDPPEH based OTFTs exhibit a mobility of 1.6 × 10−2 cm2/V s, which is the highest mobility from SMDPPEH ever reported.

  6. Coherent spin manipulation in molecular semiconductors: getting a handle on organic spintronics.

    Science.gov (United States)

    Lupton, John M; McCamey, Dane R; Boehme, Christoph

    2010-10-04

    Organic semiconductors offer expansive grounds to explore fundamental questions of spin physics in condensed matter systems. With the emergence of organic spintronics and renewed interest in magnetoresistive effects, which exploit the electron spin degree of freedom to encode and transmit information, there is much need to illuminate the underlying properties of spins in molecular electronic materials. For example, one may wish to identify over what length of time a spin maintains its orientation with respect to an external reference field. In addition, it is crucial to understand how adjacent spins arising, for example, in electrostatically coupled charge-carrier pairs, interact with each other. A periodic perturbation of the field may cause the spins to precess or oscillate, akin to a spinning top experiencing a torque. The quantum mechanical characteristic of the spin is then defined as the coherence time, the time over which an oscillating spin, or spin pair, maintains a fixed phase with respect to the driving field. Electron spins in organic semiconductors provide a remarkable route to performing "hands-on" quantum mechanics since permutation symmetries are controlled directly. Herein, we review some of the recent advances in organic spintronics and organic magnetoresistance, and offer an introductory description of the concept of pulsed, electrically detected magnetic resonance as a technique to manipulate and thus characterize the fundamental properties of electron spins. Spin-dependent dissociation and recombination allow the observation of coherent spin motion in a working device, such as an organic light-emitting diode. Remarkably, it is possible to distinguish between electron and hole spin resonances. The ubiquitous presence of hydrogen nuclei gives rise to strong hyperfine interactions, which appear to provide the basis for many of the magnetoresistive effects observed in these materials. Since hyperfine coupling causes quantum spin beating in electron

  7. Optical and spectroscopic studies on tannery wastes as a possible source of organic semiconductors.

    Science.gov (United States)

    Nashy, El-Shahat H A; Al-Ashkar, Emad; Moez, A Abdel

    2012-02-01

    Tanning industry produces a large quantity of solid wastes which contain hide proteins in the form of protein shavings containing chromium salts. The chromium wastes are the main concern from an environmental stand point of view, because chrome wastes posses a significant disposal problem. The present work is devoted to investigate the possibility of utilizing these wastes as a source of organic semi-conductors as an alternative method instead of the conventional ones. The chemical characterization of these wastes was determined. In addition, the Horizontal Attenuated Total Reflection (HATR) FT-IR spectroscopic analysis and optical parameters were also carried out for chromated samples. The study showed that the chromated samples had suitable absorbance and transmittance in the wavelength range (500-850 nm). Presence of chromium salt in the collagen samples increases the absorbance which improves the optical properties of the studied samples and leads to decrease the optical energy gap. The obtained optical energy gap gives an impression that the environmentally hazardous chrome shavings wastes can be utilized as a possible source of natural organic semiconductors with direct and indirect energy gap. This work opens the door to use some hazardous wastes in the manufacture of electronic devices such as IR-detectors, solar cells and also as solar cell windows. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Study of π-conjugation effect of organic semiconductors on their optical parameters

    Science.gov (United States)

    Ahmad, Zubair; Zafar, Qayyum; Touati, Farid; Shakoor, R. A.; Al-Thani, N. J.

    2016-04-01

    Metal free organic semiconductor "7,16-bis(3,3-dimethyl-3H-indol-2-yl)-5,14-dihydrodibenzo [b,i][1,4,8,11] tetraazacyclotetradecine" and metal free with extended π-conjugation organic semiconductor "8,19-bis(3,3-dimethyl-3H-indol-2-yl)-6,17-dihydrodinaphthol [2,3-b:2‧,3‧-i][1,4,8,11] tetraazacyclotetradecine have been synthesized and the effect of conjugation on their photovoltaic parameters have been investigated. The photo-physical study reveals band gaps of 2.61 eV for metal free and 2.16 eV for extended material. The HOMO/LUMO levels of the materials are calculated using cyclic voltammetry (CV) study. The open circuit voltages of metal free and extended materials in single layer photovoltaic cells are observed to be 0.72 and 0.73 under simulated solar light illumination (air mass 1.5 G, 100 mW/cm2), respectively. The short circuit current in the extended materials is found to be more than ∼1.5 times higher the metal free material.

  9. Optical and spectroscopic studies on tannery wastes as a possible source of organic semiconductors

    Science.gov (United States)

    Nashy, El-Shahat H. A.; Al-Ashkar, Emad; Abdel Moez, A.

    2012-02-01

    Tanning industry produces a large quantity of solid wastes which contain hide proteins in the form of protein shavings containing chromium salts. The chromium wastes are the main concern from an environmental stand point of view, because chrome wastes posses a significant disposal problem. The present work is devoted to investigate the possibility of utilizing these wastes as a source of organic semi-conductors as an alternative method instead of the conventional ones. The chemical characterization of these wastes was determined. In addition, the Horizontal Attenuated Total Reflection (HATR) FT-IR spectroscopic analysis and optical parameters were also carried out for chromated samples. The study showed that the chromated samples had suitable absorbance and transmittance in the wavelength range (500-850 nm). Presence of chromium salt in the collagen samples increases the absorbance which improves the optical properties of the studied samples and leads to decrease the optical energy gap. The obtained optical energy gap gives an impression that the environmentally hazardous chrome shavings wastes can be utilized as a possible source of natural organic semiconductors with direct and indirect energy gap. This work opens the door to use some hazardous wastes in the manufacture of electronic devices such as IR-detectors, solar cells and also as solar cell windows.

  10. Photogenerated Intrinsic Free Carriers in Small-molecule Organic Semiconductors Visualized by Ultrafast Spectroscopy

    Science.gov (United States)

    He, Xiaochuan; Zhu, Gangbei; Yang, Jianbing; Chang, Hao; Meng, Qingyu; Zhao, Hongwu; Zhou, Xin; Yue, Shuai; Wang, Zhuan; Shi, Jinan; Gu, Lin; Yan, Donghang; Weng, Yuxiang

    2015-11-01

    Confirmation of direct photogeneration of intrinsic delocalized free carriers in small-molecule organic semiconductors has been a long-sought but unsolved issue, which is of fundamental significance to its application in photo-electric devices. Although the excitonic description of photoexcitation in these materials has been widely accepted, this concept is challenged by recently reported phenomena. Here we report observation of direct delocalized free carrier generation upon interband photoexcitation in highly crystalline zinc phthalocyanine films prepared by the weak epitaxy growth method using ultrafast spectroscopy. Transient absorption spectra spanning the visible to mid-infrared region revealed the existence of short-lived free electrons and holes with a diffusion length estimated to cross at least 11 molecules along the π-π stacking direction that subsequently localize to form charge transfer excitons. The interband transition was evidenced by ultraviolet-visible absorption, photoluminescence and electroluminescence spectroscopy. Our results suggest that delocalized free carriers photogeneration can also be achieved in organic semiconductors when the molecules are packed properly.

  11. Exotic optoelectronic properties of organic semiconductors with super-controlled nanoscale sizes and molecular shapes.

    Science.gov (United States)

    Hotta, Shu; Yamao, Takeshi; Katagiri, Toshifumi

    2014-03-01

    We present several aspects of thiophene/phenylene co-oligomers (TPCOs). TPCOs are regarded as a newly occurring class of organic semiconductors. These materials are synthesized by hybridizing thiophene and phenylene rings at the molecular level with their various mutual arrangements. These materials are characterized by the super-controlled nanoscale sizes and molecular shapes. These produce peculiar crystallographic structures and high-performance optical and electronic properties. The crystals of TPCOs were obtained through both vapor phase and liquid phase. In the TPCO crystals, the molecules take upright configuration. These cause large carrier mobilities of field-effect transistors and laser oscillations under optical excitations. Spectrally-narrowed emissions (SNEs) were also achieved under weak optical excitation using a mercury lamp. The light-emitting field-effect transistors using these crystals for an active layer have shown the current-injected SNEs when the device was combined with an optical cavity and operated by an alternating-current gate-voltage method. Thus the TPCO materials will play an important role in the future in the fields of nanoscale technology and organic semiconductor materials as well as their optoelectronic device applications.

  12. Organic Semiconductor-Containing Supramolecules: Effect of Small Molecule Crystallization and Molecular Packing

    KAUST Repository

    Rancatore, Benjamin J.

    2016-01-21

    © 2016 American Chemical Society. Small molecules (SMs) with unique optical or electronic properties provide an opportunity to incorporate functionality into block copolymer (BCP)-based supramolecules. However, the assembly of supramolecules based on these highly crystalline molecules differs from their less crystalline counterparts. Here, two families of organic semiconductor SMs are investigated, where the composition of the crystalline core, the location (side- vs end-functionalization) of the alkyl solubilizing groups, and the constitution (branched vs linear) of the alkyl groups are varied. With these SMs, we present a systematic study of how the phase behavior of the SMs affects the overall assembly of these organic semiconductor-based supramolecules. The incorporation of SMs has a large effect on the interfacial curvature, the supramolecular periodicity, and the overall supramolecular morphology. The crystal packing of the SM within the supramolecule does not necessarily lead to the assembly of the comb block within the BCP microdomains, as is normally observed for alkyl-containing supramolecules. An unusual lamellar morphology with a wavy interface between the microdomains is observed due to changes in the packing structure of the small molecule within BCP microdomains. Since the supramolecular approach is modular and small molecules can be readily switched out, present studies provide useful guidance toward access supramolecular assemblies over several length scales using optically active and semiconducting small molecules.

  13. Mechanical properties of organic semiconductors for mechanically stable and intrinsically stretchable solar cells (Conference Presentation)

    Science.gov (United States)

    Lipomi, Darren J.

    2016-09-01

    This presentation describes my group's efforts to understand the molecular and microstructural basis for the mechanical properties of organic semiconductors for organic photovoltaic (OPV) devices. Our work is motivated by two goals. The first goal is to mitigate mechanical forms of degradation of printed modules during roll-to-roll fabrication, installation, and environmental forces—i.e., wind, rain, snow, and thermal expansion and contraction. Mechanical stability is a prerequisite for inexpensive processing on flexible substrates: to encapsulate devices in glass is to surrender this advantage. The second goal is to enable the next generation of ultra-flexible and stretchable solar cells for collapsible, portable, and wearable applications, and as low-cost sources of energy—"solar tarps"—for disaster relief and for the developing world. It may seem that organic semiconductors, due to their carbon framework, are already sufficiently compliant for these applications. We have found, however, that the mechanical properties (stiffness and brittleness) occupy a wide range of values, and can be difficult to predict from molecular structure alone. We are developing an experimental and theoretical framework for how one can combine favorable charge-transport properties and mechanical compliance in organic semiconductor films. In particular, we have explored the roles of the backbone, alkyl side chain, microstructural order, the glass transition, molecular packing with fullerenes, plasticizing effects of additives, extent of separation of [60]PCBM and [70]PCBM, structural randomness in low-bandgap polymers, and reinforcement by encapsulation, on the mechanical compliance. We are exploring the applicability of semi-empirical "back-of-the-envelope" models, along with multi-scale molecular dynamics simulations, with the ultimate goal of designing electroactive organic materials whose mechanical properties can be dialed-in. We have used the insights we have developed to

  14. Material degradation of liquid organic semiconductors analyzed by nuclear magnetic resonance spectroscopy

    Directory of Open Access Journals (Sweden)

    Tatsuya Fukushima

    2015-08-01

    Full Text Available Liquid organic light-emitting diodes (liquid OLEDs are unique devices consisting only of liquid organic semiconductors in the active layer, and the device performances have been investigated recently. However, the device degradation, especially, the origin has been unknown. In this study, we show that material degradation occurs in liquid OLEDs, whose active layer is composed of carbazole with an ethylene glycol chain. Nuclear magnetic resonance (NMR experiments clearly exhibit that the dimerization reaction of carbazole moiety occurs in the liquid OLEDs during driving the devices. In contrast, cleavages of the ethylene glycol chain are not detected within experimental error. The dimerization reaction is considered to be related to the device degradation.

  15. Optical devices combining an organic semiconductor crystal with a two-dimensional inorganic diffraction grating

    Energy Technology Data Exchange (ETDEWEB)

    Kitazawa, Takenori; Yamao, Takeshi, E-mail: yamao@kit.ac.jp; Hotta, Shu [Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Kyoto 606-8585 (Japan)

    2016-02-01

    We have fabricated optical devices using an organic semiconductor crystal as an emission layer in combination with a two-dimensional (2D) inorganic diffraction grating used as an optical cavity. We formed the inorganic diffraction grating by wet etching of aluminum-doped zinc oxide (AZO) under a 2D cyclic olefin copolymer (COC) diffraction grating used as a mask. The COC diffraction grating was fabricated by nanoimprint lithography. The AZO diffraction grating was composed of convex prominences arranged in a triangular lattice. The organic crystal placed on the AZO diffraction grating indicated narrowed peaks in its emission spectrum under ultraviolet light excitation. These are detected parallel to the crystal plane. The peaks were shifted by rotating the optical devices around the normal to the crystal plane, which reflected the rotational symmetries of the triangular lattice through 60°.

  16. Smooth growth of organic semiconductor films on graphene for high efficiency electronics

    Energy Technology Data Exchange (ETDEWEB)

    Hlawacek, Gregor [Physics of Interfaces and Nanomaterials, MESA, Institute for Nanotechnology, University of Twente, Enschede (Netherlands); Institute for Physics, University of Leoben (Austria); Khokhar, Fawad S.; Gastel, Raoul van; Poelsema, Bene [Physics of Interfaces and Nanomaterials, MESA, Institute for Nanotechnology, University of Twente, Enschede (Netherlands); Teichert, Christian [Institute for Physics, University of Leoben (Austria)

    2011-07-01

    High quality thin films of conjugated molecules with smooth interfaces are important to assist the advent of organic electronics. Here, we report on the layer-by-layer growth of the organic semiconductor molecule para-sexiphenyl on the transparent electrode material graphene. State of the art Low Energy Electron Microscopy, micro Low Energy Electron Diffraction and spot profile analysis techniques revealed the morphological and structural evolution of the thin film. Subtle difference in the molecular arrangement in comparison to graphite are confirmed by molecular dynamics simulations. Initial islands are found to have a meta stable structure that is characterized by flat lying molecules. With increasing coverage this structure changes into a herringbone arrangement similar to the {l_brace}111{r_brace} bulk layer. The layer-by-layer growth of 6P on graphene proceeds by subsequent adding of {l_brace}111{r_brace} layers.

  17. Bio-recognitive photonics of a DNA-guided organic semiconductor.

    Science.gov (United States)

    Back, Seung Hyuk; Park, Jin Hyuk; Cui, Chunzhi; Ahn, Dong June

    2016-01-01

    Incorporation of duplex DNA with higher molecular weights has attracted attention for a new opportunity towards a better organic light-emitting diode (OLED) capability. However, biological recognition by OLED materials is yet to be addressed. In this study, specific oligomeric DNA-DNA recognition is successfully achieved by tri (8-hydroxyquinoline) aluminium (Alq3), an organic semiconductor. Alq3 rods crystallized with guidance from single-strand DNA molecules show, strikingly, a unique distribution of the DNA molecules with a shape of an 'inverted' hourglass. The crystal's luminescent intensity is enhanced by 1.6-fold upon recognition of the perfect-matched target DNA sequence, but not in the case of a single-base mismatched one. The DNA-DNA recognition forming double-helix structure is identified to occur only in the rod's outer periphery. This study opens up new opportunities of Alq3, one of the most widely used OLED materials, enabling biological recognition.

  18. Collection-limited theory interprets the extraordinary response of single semiconductor organic solar cells.

    Science.gov (United States)

    Ray, Biswajit; Baradwaj, Aditya G; Khan, Mohammad Ryyan; Boudouris, Bryan W; Alam, Muhammad Ashraful

    2015-09-08

    The bulk heterojunction (BHJ) organic photovoltaic (OPV) architecture has dominated the literature due to its ability to be implemented in devices with relatively high efficiency values. However, a simpler device architecture based on a single organic semiconductor (SS-OPV) offers several advantages: it obviates the need to control the highly system-dependent nanoscale BHJ morphology, and therefore, would allow the use of broader range of organic semiconductors. Unfortunately, the photocurrent in standard SS-OPV devices is typically very low, which generally is attributed to inefficient charge separation of the photogenerated excitons. Here we show that the short-circuit current density from SS-OPV devices can be enhanced significantly (∼100-fold) through the use of inverted device configurations, relative to a standard OPV device architecture. This result suggests that charge generation may not be the performance bottleneck in OPV device operation. Instead, poor charge collection, caused by defect-induced electric field screening, is most likely the primary performance bottleneck in regular-geometry SS-OPV cells. We justify this hypothesis by: (i) detailed numerical simulations, (ii) electrical characterization experiments of functional SS-OPV devices using multiple polymers as active layer materials, and (iii) impedance spectroscopy measurements. Furthermore, we show that the collection-limited photocurrent theory consistently interprets typical characteristics of regular SS-OPV devices. These insights should encourage the design and OPV implementation of high-purity, high-mobility polymers, and other soft materials that have shown promise in organic field-effect transistor applications, but have not performed well in BHJ OPV devices, wherein they adopt less-than-ideal nanostructures when blended with electron-accepting materials.

  19. Charge transfer rates in organic semiconductors beyond first-order perturbation: from weak to strong coupling regimes.

    Science.gov (United States)

    Nan, Guangjun; Wang, Linjun; Yang, Xiaodi; Shuai, Zhigang; Zhao, Yi

    2009-01-14

    Semiclassical Marcus electron transfer theory is often employed to investigate the charge transport properties of organic semiconductors. However, quite often the electronic couplings vary several orders of magnitude in organic crystals, which goes beyond the application scope of semiclassical Marcus theory with the first-order perturbative nature. In this work, we employ a generalized nonadiabatic transition state theory (GNTST) [Zhao et al., J. Phys. Chem. A 110, 8204 (2004)], which can evaluate the charge transfer rates from weak to strong couplings, to study charge transport properties in prototypical organic semiconductors: quaterthiophene and sexithiophene single crystals. By comparing with GNTST results, we find that the semiclassical Marcus theory is valid for the case of the coupling semiconductors with general electronic coupling terms. Taking oligothiophenes as examples, we find that our GNTST-calculated hole mobility is about three times as large as that from the semiclassical Marcus theory. The difference arises from the quantum nuclear tunneling and the nonperturbative effects.

  20. Piezoresistance in p-type silicon revisited

    DEFF Research Database (Denmark)

    Richter, Jacob; Pedersen, Jesper; Brandbyge, Mads;

    2008-01-01

    We calculate the shear piezocoefficient pi44 in p-type Si with a 6×6 k·p Hamiltonian model using the Boltzmann transport equation in the relaxation-time approximation. Furthermore, we fabricate and characterize p-type silicon piezoresistors embedded in a (001) silicon substrate. We find that the ...

  1. Spectral photosensitivity of an organic semiconductor in a submicron metal grating

    Science.gov (United States)

    Blinov, L. M.; Lazarev, V. V.; Yudin, S. G.; Palto, S. P.

    2016-02-01

    The photoelectric effect in films of the copper phthalocyanine organic semiconductor (α-CuPc) has been experimentally studied for two fundamentally different geometries. A sample in the first, normal geometry is fabricated in the form of a sandwich with an α-CuPc film between a transparent SnO2 electrode on a substrate and an upper reflecting Al electrode. In the second case of the planar geometry, the semiconductor is deposited on the substrate with a system of submicron chromium interdigital electrodes. It has been found that the effective photoconductivity in the planar geometry is more than two orders of magnitude higher than that in the normal geometry. In addition to the classical model (without excitons), a simple exciton model has been proposed within which a relation has been obtained between the probability of the formation of electron-hole pairs and the characteristic recombination and dissociation times of excitons. An increase in the photoconductivity in the planar geometry has been explained within the exciton model by an increase in the rate of dissociation of excitons into electron-hole pairs owing to acceptor oxygen molecules, which diffuse more efficiently into the film in the case of the planar geometry where the upper electrode is absent.

  2. N-channel field-effect transistors with an organic-inorganic layered perovskite semiconductor

    Science.gov (United States)

    Matsushima, Toshinori; Mathevet, Fabrice; Heinrich, Benoît; Terakawa, Shinobu; Fujihara, Takashi; Qin, Chuanjiang; Sandanayaka, Atula S. D.; Ribierre, Jean-Charles; Adachi, Chihaya

    2016-12-01

    Large electron injection barriers and electrode degradation are serious issues that need to be overcome to obtain n-channel operation in field-effect transistors with an organic-inorganic layered perovskite (C6H5C2H4NH3)2SnI4 semiconductor. By employing low-work-function Al source/drain electrodes and by inserting C60 layers between the perovskite semiconductor and the Al electrodes to reduce the injection barrier and to suppress the electrode degradation, we demonstrate n-channel perovskite transistors with electron mobilities of up to 2.1 cm2/V s, the highest value ever reported in spin-coated perovskite transistors. The n-channel transport properties of these transistors are relatively stable in vacuum but are very sensitive to oxygen, which works as electron traps in perovskite and C60 layers. In addition, grazing-incidence X-ray scattering and thermally stimulated current measurements revealed that crystallite size and electron traps largely affect the n-channel transport properties.

  3. Controlling of the optical properties of the solutions of the PTCDI-C8 organic semiconductor

    Science.gov (United States)

    Erdoğan, Erman; Gündüz, Bayram

    2016-09-01

    N,N'-Dioctyl-3,4,9,10 perylenedicarboximide (PTCDI-C8) organic semiconductor have vast applications in solar cells, thermoelectric generators, thin film photovoltaics and many other optoelectronic devices. These applications of the materials are based on their spectral and optical properties. The solutions of the PTCDI-C8 for different molarities were prepared and the spectral and optical mesaurements were analyzed. Effects of the molarities on optical properties were investigated. Vibronic structure has been observed based on the absorption bands of PTCDI-C8 semiconductor with seven peaks at 2.292, 2.451, 2.616, 3.212, 3.851, 4.477 and 4.733 eV. The important spectral parameteres such as molar/mass extinction coefficients, absorption coefficient of the PTCDI-C8 molecule were calculated. Optical properties such as angle of incidence/refraction, optical band gap, real and imaginary parts of dielectric constant, loss factor and electrical susceptibility of the the PTCDI-C8 were obtained. Finally, we discussed these parameters for optoelectronic applications and compared with related parameters in literature.

  4. Side-Chain-Induced Rigid Backbone Organization of Polymer Semiconductors through Semifluoroalkyl Side Chains.

    Science.gov (United States)

    Kang, Boseok; Kim, Ran; Lee, Seon Baek; Kwon, Soon-Ki; Kim, Yun-Hi; Cho, Kilwon

    2016-03-23

    While high-mobility p-type conjugated polymers have been widely reported, high-mobility n-type conjugated polymers are still rare. In the present work, we designed semifluorinated alkyl side chains and introduced them into naphthalene diimide-based polymers (PNDIF-T2 and PNDIF-TVT). We found that the strong self-organization of these side chains induced a high degree of order in the attached polymer backbones by forming a superstructure composed of "backbone crystals" and "side-chain crystals". This phenomenon was shown to greatly enhance the ordering along the backbone direction, and the resulting polymers thus exhibited unipolar n-channel transport in field-effect transistors with remarkably high electron mobility values of up to 6.50 cm(2) V(-1) s(-1) and with a high on-off current ratio of 10(5).

  5. IR spectroscopic investigation of charge transfer at interfaces of organic semiconductors (Conference Presentation)

    Science.gov (United States)

    Beck, Sebastian; Hillebrandt, Sabina; Pucci, Annemarie

    2016-09-01

    In organic electronics, the interactions at interfaces between different organic and inorganic layers play a decisive role for device functionality and performance. Therefore, more detailed, quantitative studies of charge transfer (CT) at such interfaces are needed to improve the understanding of the underlying mechanisms. In this study we show that in-situ infrared spectroscopy can be used to investigate CT effects at organic/organic as well as inorganic/organic interfaces quantitatively. For different combinations of commonly used organic semiconductors such as 4,4´-bis(N-carbazolyl)-1,1´-biphenyl (CBP) or fluorinated zinc phthalocyanine (F4ZnPc) and inorganic contact materials such as molybdenum oxide (MoO3) or indium tin oxide (ITO) the CT at the interface was investigated using in-situ IR spectroscopy. The measurements were carried out under UHV conditions during film growth what enables a careful study of the influence of different parameters such as substrate temperature and layer thickness in a controlled way even on a nanometer scale. When the organic molecules are deposited onto the underlying layer charged and non-charged species form which can be identified and quantitatively analyzed in the IR spectra. It was also found that the deposition sequence can strongly influence the interface properties what might have strong implications on the layer stack design. For example, when MoO3 is deposited onto CBP, the CBP layer is strongly doped, due to diffusion of the deposited transition metal oxide clusters into the organic layer. Financial support by BMBF (project INTERPHASE) is gratefully acknowledged.

  6. Photoluminescence polarization anisotropy for studying long-range structural ordering within semiconductor multi-atomic alloys and organic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T.; Percino, J. [Instituto de Ciencias, BUAP, Privada 17 Norte, No 3417, col. San Miguel Huyeotlipan, 72050, Puebla, Pue. (Mexico); Orlova, T. [Department of Chemical and Biochemical Engineering, University of Notre Dame, Notre Dame, IN (United States); Vavilova, L. [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya, St Petersburg 194021, Russian Federation (Russian Federation)

    2013-12-04

    Long-range structural ordering within multi-component semiconductor alloys and organic crystals leads to significant optical anisotropy and, in particular, to anisotropy of the photoluminescence (PL) emission. The PL emission of ternary and quaternary semiconductor alloys is polarized if there is some amount of the atomic ordering within the crystal structure. We analyze the polarization of the PL emission from the quaternary GaInAsP semiconductor alloy grown by Liquid Phase Epitaxy (LPE) and conclude that it could be caused by low degree atomic ordering within the crystal structure together with the thermal biaxial strain due to difference between the thermal expansion coefficients of the layer and the substrate. We also study the state of polarization of the PL from organic crystals in order to identify different features of the crystal PL spectrum.

  7. Direct observation of entangled multiexciton states in organic semiconductors (Conference Presentation)

    Science.gov (United States)

    Yong, Chaw Keong; Musser, Andrew J.; Clark, Jenny; Anthony, John E.; Beljonne, David; Friend, Richard H.; Sirringhaus, Henning

    2016-09-01

    The standard view of singlet exciton fission in organic semiconductor is that one photon creates a singlet exciton which subsequently decays into a correlated triplet pair state (TT) multiexciton states. The triplet pair state then splits to form two free triplets. Although the theoretical description of (TT) is well developed since 1970, it has so far proved difficult to determine the role and nature of the (TT) state in solid films from experiment directly. Here, using a combination of highly sensitive broadband transient absorption and photoluminescence spectroscopies on a range of polyacene films, we demonstrate that the (TT) multiexciton states is bound and energetically stabilised with respect to free triplets in even the most efficient singlet fission materials, such as TIPS-pentacene and pentacene. The (TT) multiexciton state is emissive, and we find that charge-transfer from one (TT) state to the neighboring electron acceptors has a yield of >100%, i.e. more than one charge is transferred per charge-transfer event. Our findings suggest that the formation of spin-correlated (TT) states emits as one particle and generates 2 charges in organic solar cells and thus open a range of fascinating questions regarding the potential to use entanglement to enhance organic photovoltaic efficiency and the application of organic materials in quantum information

  8. Electrical characterization of the organic semiconductor Ag/CuPc/Au Schottky diode

    Institute of Scientific and Technical Information of China (English)

    Mutabar Shah; M. H. Sayyad; Kh. S. Karimov

    2011-01-01

    This paper reports on the fabrication and investigation of a surface-type organic semiconductor copper phthalocyanine (CuPc) based diode. A thin film of CuPc of thickness 100 nm was thermally sublimed onto a glass substrate with preliminary deposited metallic electrodes to form a surface-type Ag/CuPc/Au Schottky diode. The current-voltage characteristics were measured at room temperature under dark conditions. The barrier height was calculated as 1.05 eV. The values of mobility and conductivity was found to be 1.74 x l0-9 cm2/(V.s) and 5.5 x 10-6 Ω-1. cm-1, respectively. At low voltages the device showed ohmic conduction and the space charge limited current conduction mechanisms were dominated at higher voltages.

  9. Simulation of Temperature-Dependent Charge Transport in Organic Semiconductors with Various Degrees of Disorder.

    Science.gov (United States)

    Heck, Alexander; Kranz, Julian J; Elstner, Marcus

    2016-07-12

    Different trends in the temperature dependence of the mobility can be observed in organic semiconductors, which constitutes a serious challenge for theoretical approaches. In this work, we apply an atomistic bottom-up simulation for the calculation of temperature-dependent mobilities of a broad selection of materials, ranging from single crystal to amorphous solid. We evaluate how well the method is able to distinguish temperature dependences of different materials and how the findings relate to experimental observations. The applied method is able to cover the full range of temperature dependencies from activated transport in amorphous materials to band-like transport in crystals. In well-characterized materials, we find good agreement with the experiment and a band-like temperature dependence. In less-ordered materials, we find discrepancies from the experiment that indicated that experimentally studied materials possess a higher degree of disorder than do the simulated defect-free morphologies.

  10. Organic semiconductor growth on graphene studied by LEEM and {mu}LEED

    Energy Technology Data Exchange (ETDEWEB)

    Hlawacek, Gregor [Institute of Physics, University of Leoben (Austria); MESA Institute for Nanotechnology, University of Twente, Enschede (Netherlands); Khokhar, Fawad S.; Gastel, Raoul van; Poelsema, Bene [MESA Institute for Nanotechnology, University of Twente, Enschede (Netherlands); Teichert, Christian [Institute of Physics, University of Leoben (Austria)

    2010-07-01

    The organic semiconductor para-sexiphenyl (6P) was deposited at various substrate temperatures onto graphene flakes grown on Iridium(111). The dynamics of the deposition process and the crystallographic structure were observed in-situ by means of Low Energy Electron Microscopy (LEEM) and micro Low Energy Electron Diffraction ({mu}LEED). Layer-by-layer growth of lying molecules on graphene is observed for low deposition temperatures. After formation of a low-density layer, the full first monolayer already shows a bulk like structure. An exceptionally high mobility for 6P on graphene is observed in the initial low density layer. For room temperature the growth mode changes to Stranski-Krastanov for 6P on graphene. At elevated temperatures a continuous layer of upright standing molecules on the Ir(111) surface is nucleated by the presence of the graphene flakes.

  11. Exploring the energy landscape of the charge transport levels in organic semiconductors at the molecular scale.

    Science.gov (United States)

    Cornil, J; Verlaak, S; Martinelli, N; Mityashin, A; Olivier, Y; Van Regemorter, T; D'Avino, G; Muccioli, L; Zannoni, C; Castet, F; Beljonne, D; Heremans, P

    2013-02-19

    The extraordinary semiconducting properties of conjugated organic materials continue to attract attention across disciplines including materials science, engineering, chemistry, and physics, particularly with application to organic electronics. Such materials are used as active components in light-emitting diodes, field-effect transistors, or photovoltaic cells, as a substitute for (mostly Si-based) inorganic semiconducting materials. Many strategies developed for inorganic semiconductor device building (doping, p-n junctions, etc.) have been attempted, often successfully, with organics, even though the key electronic and photophysical properties of organic thin films are fundamentally different from those of their bulk inorganic counterparts. In particular, organic materials consist of individual units (molecules or conjugated segments) that are coupled by weak intermolecular forces. The flexibility of organic synthesis has allowed the development of more efficient opto-electronic devices including impressive improvements in quantum yields for charge generation in organic solar cells and in light emission in electroluminescent displays. Nonetheless, a number of fundamental questions regarding the working principles of these devices remain that preclude their full optimization. For example, the role of intermolecular interactions in driving the geometric and electronic structures of solid-state conjugated materials, though ubiquitous in organic electronic devices, has long been overlooked, especially when it comes to these interfaces with other (in)organic materials or metals. Because they are soft and in most cases disordered, conjugated organic materials support localized electrons or holes associated with local geometric distortions, also known as polarons, as primary charge carriers. The spatial localization of excess charges in organics together with low dielectric constant (ε) entails very large electrostatic effects. It is therefore not obvious how these

  12. Fused thiophene and its periphery fluorinated substitution derivatives: a theoretical study for organic semiconductors

    Science.gov (United States)

    Wei, Hui-Ling; Shi, Ya-Rui; Liu, Yu-Fang

    2015-06-01

    A series of phenyl end-capped derivatives of benzo[d,d‧]thieno[3,2-b4,5- b‧]dithiophene (BTDT) with periphery-fluorinated substitutions (PFS) were systematically investigated by using density functional theory (DFT) combined with the Marcus-Hush electron transfer theory. The substituting effects of PFS were discussed. Compared with the original compounds, (i) the PFS compounds have a relatively higher efficiency of charge transport, lower barriers of electron injection, and larger HOMO-LUMO gaps; (ii) the air-stability and the device performance are enhanced by PFS; and (iii) the HOMO-LUMO transitions in the absorption spectrum of the PFS compounds show an obvious blue-shift trend. The perfluorophenylbisbenzo[d, d‧]thieno[3,2-b4,5-b‧]dithiophene (BpF-BTDT) is found to be the most stable and most effective compound in charge transport among the investigated compounds, and it is suggested as an ambipolar semiconducting material. The results of electronic coupling of the bisbenzo[d, d‧]thieno[3,2-b 4,5- b‧]dithiophene (BBTDT) derivatives show that the orbital interaction is mainly contributed by the neighboring molecule in the two dimensional (2D) layer. The PFS compounds have lower oxidization potential, ionization potential, and electron affinity values than the corresponding original ones, which suggest that fluorination can enhance the performance of the thiophene-based organic solar cells. These findings provide a better understanding of the PFS effects on organic semiconductors and may help to design high-performance semiconductor materials.

  13. Dual ohmic contact to N- and P-type silicon carbide

    Science.gov (United States)

    Okojie, Robert S. (Inventor)

    2013-01-01

    Simultaneous formation of electrical ohmic contacts to silicon carbide (SiC) semiconductor having donor and acceptor impurities (n- and p-type doping, respectively) is disclosed. The innovation provides for ohmic contacts formed on SiC layers having n- and p-doping at one process step during the fabrication of the semiconductor device. Further, the innovation provides a non-discriminatory, universal ohmic contact to both n- and p-type SiC, enhancing reliability of the specific contact resistivity when operated at temperatures in excess of 600.degree. C.

  14. Maximum probing depth of low-energy photoelectrons in an amorphous organic semiconductor film

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, Yusuke [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Nakayama, Yasuo, E-mail: nkym@restaff.chiba-u.jp [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Machida, Shin’ichi; Kinjo, Hiroumi [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Ishii, Hisao [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

    2014-12-15

    Highlights: • Photoelectron attenuation lengths (AL) through amorphous organic films were examined. • In the energy range below 9 eV, AL fluctuates unlike a prediction by universal curve. • AL of photoelectron yield spectroscopy (PYS) measurements was found to be ∼3.6 nm. • PYS signals still survived through an 18 nm-thick film despite such a moderate AL. • This indicates buried interfaces in practical organic devices can be accessed by PYS. - Abstract: The attenuation length (AL) of low energy photoelectrons inside a thin film of a π-conjugated organic semiconductor material, 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), was investigated using ultraviolet photoelectron spectroscopy (UPS) and photoelectron yield spectroscopy (PYS) to discuss their probing depth in amorphous organic thin films. The present UPS results indicated that the AL is 2–3 nm in the electron energy range of 6.3–8.3 eV with respect to the Fermi level, while the PYS measurements which collected the excited electrons in a range of 4.5–6 eV exhibited a longer AL of 3.6 nm. Despite this still short AL in comparison to a typical thickness range of electronic devices that are a few tens of nm-thick, the photoemission signal penetrating through further thicker (18 nm) organic film was successfully detected by PYS. This fact suggests that the electronic structures of “buried interfaces” inside practical organic devices are accessible using this rather simple measurement technique.

  15. Implementing Metal-to-Ligand Charge Transfer in Organic Semiconductor for Improved Visible-Near-Infrared Photocatalysis.

    Science.gov (United States)

    Li, Yanrui; Wang, Zhaowu; Xia, Tong; Ju, Huanxin; Zhang, Ke; Long, Ran; Xu, Qian; Wang, Chengming; Song, Li; Zhu, Junfa; Jiang, Jun; Xiong, Yujie

    2016-08-01

    The coordination of organic semiconductors with metal cations can induce metal-to-ligand charge transfer, which broadens light absorption to cover the visible-near-infrared (vis-NIR) spectrum. As a proof-of-concept demonstration, the g-C3 N4 -based complex exhibits dramatically enhanced photocatalytic H2 production with excellent durability under vis-NIR irradiation.

  16. Inkjet-Printed Organic Field-Effect Transistor by Using Composite Semiconductor Material of Carbon Nanoparticles and Poly(3-Hexylthiophene

    Directory of Open Access Journals (Sweden)

    Chih-Ting Lin

    2011-01-01

    Full Text Available Poly(3-hexylthiophene, P3HT, has been widely used in organic electronics as a semiconductor material. It suffers from the low carrier mobility characteristics. This limits P3HT to be employed in applications. Therefore, the blending semiconductor material, carbon nanoparticle (CNP, and P3HT, are developed and examined by inkjet-printing organic field-effect transistor technology in this work. The effective carrier mobility of fabricated OFETs can be enhanced by 8 folds with adding CNP and using O2 plasma treatment. At the same time, the transconductance of fabricated OFETs is also raised by 5 folds. Based on the observations of SEM, XRD, and FTIR, these improvements are contributed to the local field induced by the formation of CNP/P3HT complexes. This observation presents an insight of the development in organic semiconductor materials. Moreover, this work also offers a low-cost and effective semiconductor material for inkjet-printing technology in the development of organic electronics.

  17. Determination of localized trap parameters in organic semiconductors using charge based deep level transient spectroscopy (Q-DLTS)

    Science.gov (United States)

    Nguyen, T. P.; Ip, J.; Gaudin, O.; Jackman, R. B.

    2004-07-01

    In organic light emitting diodes (OLEDs), localized traps within the band gap of the organic semiconductor play a fundamental role in the light emission process. Trapped charge carriers cannot recombine efficiently and therefore do not contribute to the emission. The determination of the trap parameters in the emitting layer is especially important in the evaluation of the efficiency of such devices. We have investigated the trap parameters in some organic semiconductors using the Charge-Based Deep Level Transient Spectroscopy (Q-DLTS) technique. Examples are given in poly(p phenylene vinylene) or PPV and 4, 4'-bis(4-dimethylaminostryryl) or DMASB, for which the trap level, the trap density, and the capture cross section were determined. In addition, it was possible to identify the carrier type (minority and majority) traps in these semiconductors. The results were compared with those obtained in similar materials by other techniques such as conventional DLTS, thermally stimulated currents (TSC), impedance measurements. Q-DLTS appears to be a powerful tool for studying defects in organic semiconductors.

  18. Optically switchable transistor via energy-level phototuning in a bicomponent organic semiconductor

    Science.gov (United States)

    Orgiu, Emanuele; Crivillers, Núria; Herder, Martin; Grubert, Lutz; Pätzel, Michael; Frisch, Johannes; Pavlica, Egon; Duong, Duc T.; Bratina, Gvido; Salleo, Alberto; Koch, Norbert; Hecht, Stefan; Samorì, Paolo

    2012-08-01

    Organic semiconductors are suitable candidates for printable, flexible and large-area electronics. Alongside attaining an improved device performance, to confer a multifunctional nature to the employed materials is key for organic-based logic applications. Here we report on the engineering of an electronic structure in a semiconducting film by blending two molecular components, a photochromic diarylethene derivative and a poly(3-hexylthiophene) (P3HT) matrix, to attain phototunable and bistable energy levels for the P3HT's hole transport. As a proof-of-concept we exploited this blend as a semiconducting material in organic thin-film transistors. The device illumination at defined wavelengths enabled reversible tuning of the diarylethene's electronic states in the blend, which resulted in modulation of the output current. The device photoresponse was found to be in the microsecond range, and thus on a technologically relevant timescale. This modular blending approach allows for the convenient incorporation of various molecular components, which opens up perspectives on multifunctional devices and logic circuits.

  19. Theoretical study of anisotropic mobility in ladder-type molecule organic semiconductors

    Science.gov (United States)

    Wei, Hui-Ling; Liu, Yu-Fang

    2014-09-01

    The properties of two ladder-type semiconductors {M1: 2,2'-(2,7-dihexy1-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-4,9-diylidene) dimalononitrile and M2: 2,7-dihexy1-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-4,9-dione} as the n-type and ambipolar organic materials are systematically investigated using the first-principle density functional theory combined with the Marcus-Hush electron transfer theory. It is found that the substitution of M1 induces large changes in its electron-transfer mobility of 1.370 cm2 V-1 s-1. M2 has both large electron- and hole-transfer mobility of 0.420 and 0.288 cm2 V-1 s-1, respectively, which indicates that M2 is potentially a high efficient ambipolar organic semiconducting material. Both the M1 and M2 crystals show remarkable anisotropic behavior. A proper design of the n-type and ambipolar organic electronic materials, which may have high mobility performance, is suggested based on the investigated two molecules.

  20. Electrochemical characterization of sub-micro-gram amounts of organic semiconductors using scanning droplet cell microscopy

    Science.gov (United States)

    Gasiorowski, Jacek; Mardare, Andrei I.; Sariciftci, Niyazi S.; Hassel, Achim Walter

    2013-01-01

    Scanning droplet cell microscopy (SDCM) uses a very small electrolyte droplet at the tip of a capillary which comes in contact with the working electrode. This method is particularly interesting for studies on organic semiconductors since it provides localized electrochemical investigations with high reproducibility. One clear advantage of applying SDCM is represented by the very small amounts of material necessary (less than 1 mg). Organic materials can be investigated quickly and inexpensively in electrochemical studies with a high throughput. In the present study, thin layers of poly(3-hexylthiophene) (P3HT), which is one of the most often used material for organic solar cells, were deposited on ITO/glass as working electrodes in SDCM studies. The redox reactions in 0.1 M tetra(n-butyl)ammonium hexafluorophosphate (TBAPF6) dissolved in propylene carbonate were studied by cyclic voltammetry and by electrochemical impedance spectroscopy. Two reversible, distinct oxidation steps of the P3HT were detected and their kinetics were studied in detail. The doping of P3HT increased due to the electrochemical oxidation and had resulted in a decrease of the film resistance by a few orders of magnitude. Due to localization on the sample various parameter combinations can be studied quantitatively and reproducibly. PMID:24926226

  1. Characterization of the Hole Transport and Electrical Properties in the Small-Molecule Organic Semiconductors

    Science.gov (United States)

    Wang, L. G.; Zhu, J. J.; Liu, X. L.; Cheng, L. F.

    2017-10-01

    In this paper, we investigate the hole transport and electrical properties in a small-molecule organic material N, N'-bis(1-naphthyl)- N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB), which is frequently used in organic light-emitting diodes. It is shown that the thickness-dependent current density versus voltage ( J- V) characteristics of sandwich-type NPB-based hole-only devices cannot be described well using the conventional mobility model without carrier density or electric field dependence. However, a consistent and excellent description of the thickness-dependent and temperature-dependent J- V characteristics of NPB hole-only devices can be obtained with a single set of parameters by using our recently introduced improved model that take into account the temperature, carrier density, and electric field dependence of the mobility. For the small-molecule organic semiconductor studied, we find that the width of the Gaussian distribution of density of states σ and the lattice constant a are similar to the values reported for conjugated polymers. Furthermore, we show that the boundary carrier density has an important effect on the J- V characteristics. Both the maximum of carrier density and the minimum of electric field appear near the interface of NPB hole-only devices.

  2. Prediction of charge mobility in organic semiconductors with consideration of the grain-size effect

    Science.gov (United States)

    Park, Jin Woo; Lee, Kyu Il; Choi, Youn-Suk; Kim, Jung-Hwa; Jeong, Daun; Kwon, Young-Nam; Park, Jong-Bong; Ahn, Ho Young; Park, Jeong-Il; Lee, Hyo Sug; Shin, Jaikwang

    2016-09-01

    A new computational model to predict the hole mobility of poly-crystalline organic semiconductors in thin film was developed (refer to Phys. Chem. Chem. Phys., 2016, DOI: 10.1039/C6CP02993K). Site energy differences and transfer integrals in crystalline morphologies of organic molecules were obtained from quantum chemical calculation, in which the periodic boundary condition was efficiently applied to capture the interactions with the surrounding molecules in the crystalline organic layer. Then the parameters were employed in kinetic Monte Carlo (kMC) simulations to estimate the carrier mobility. Carrier transport in multiple directions has been considered in the kMC simulation to mimic polycrystalline characteristic in thin-film condition. Furthermore, the calculated mobility was corrected with a calibration equation based on the microscopic images of thin films to take the effect of grain boundary into account. As a result, good agreement was observed between the predicted and measured hole mobility values for 21 molecular species: the coefficient of determination (R2) was estimated to be 0.83 and the mean absolute error was 1.32 cm2 V-1 s-1. This numerical approach can be applied to any molecules for which crystal structures are available and will provide a rapid and precise way of predicting the device performance.

  3. Unique Room Temperature Light Emitting Diode Based on 2D Hybrid Organic-Inorganic Low Dimensional Perovskite Semiconductor

    CERN Document Server

    Vassilakopoulou, Anastasia; Koutselas, Ioannis

    2016-01-01

    Room temperature single layer light emitting diode(LED), based on a two dimensional hybrid organic-inorganic semiconductor(HOIS), is demonstrated. This simple, low cost excitonic LED operates at low voltages. Such an excitonic device is presented for the first time as functioning at room temperature. The newly introduced class of perovskite LEDs, until now based on 3D perovksite HOIS, is now broadened with the implementation of the 2D HOIS. Novel functionalities can be realized since it is now possible to access the hybrid's 2D semiconductor advantageous properties, such as the increased excitonic peak wavelength tunability, excitonic binding energy and oscillator strength.

  4. Photooxidation of organic wastes using semiconductor nanoclusters. 1998 annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Wilcoxon, J.P.

    1998-06-01

    'This report summarizes work after 1.5 years of a 3-year project. The authors efforts have focused on demonstration of photocatalysis of organic pollutants using nanosize MoS{sub 2}. They investigated the effects of (1) bandgap, valence and conduction band energies; (2) surface modification of MoS{sub 2} by deposition of metal and metal oxide islands to enhance electron transfer; and (3) use of semi-conductor semi-conductor composites to achieve improved charge separation and thus photooxidation of pollutants. They synthesized and studied nanosize MoS{sub 2} of three different sizes and associated bandgaps and studied photoredox reactions of nanosize MoS{sub 2} dispersed in solution and supported on a macroscopic powder. The latter would be the method of choice for use as a practical photocatalyst for water purification. As they emphasized in the original proposal, MoS{sub 2} in nanosize form can be tuned to absorb various amounts of the solar spectrum. They discovered there is an optimal choice of absorbance characteristics and valence and conduction band levels which allow the rapid photo-oxidation of a chosen organic molecule. The advantages of having a photostable material with a tunable bandgap were demonstrated in an experiment where phenol destruction with visible (> 450 nm) light occurred at a dramatically faster rate with nanoscale MoS{sub 2} catalysts compared to the best available previous material TiO{sub 2}. This was the first demonstration of rapid photooxidation of an organic molecule using a completely photostable catalyst and only visible light. The possibility of transferring electrons or holes between nanoscale MoS{sub 2} and other semiconductor materials in order to increase electron/hole lifetimes were explored. It was shown that small amounts (<5 weight %) of nanoscale MoS{sub 2} deposited on to TiO{sub 2} can lead to significant ({approximately}2) enhancements of phenol destruction rates. A number of different chemicals were

  5. Phototreatment of Water by Organic Photosensitizers and Comparison with Inorganic Semiconductors

    Directory of Open Access Journals (Sweden)

    Merlyn Thandu

    2015-01-01

    Full Text Available Phototreatment of water is drawing the attention of many as a promising alternative to replace methods like chlorination, ozonization, and other oxidation processes, used in current disinfection methods limiting harmful side-products and by-products that can cause damage to the fauna and flora. Porphyrins, phthalocyanines, and other related organic dyes are well known for their use in photodynamic therapy (PDT. These photosensitizers cause cell death by generating reactive oxygen species (ROS especially singlet oxygen in the presence of light. Such molecules are also being explored for photodynamically treating microbial infections, killing of unwanted pathogens in the environment, and oxidation of chemical pollutants. The process of photosensitisation (phototreatment can be applied for obtaining clean, microbe-free water, thus exploiting the versatile properties of photosensitizers. This review collects the various attempts carried out for phototreatment of water using organic photosensitizers. For comparison, some reports of semiconductors (especially TiO2 used in photocatalytic treatment of water are also mentioned.

  6. Electrochromic conductive polymer fuses for hybrid organic/inorganic semiconductor memories

    Science.gov (United States)

    Möller, Sven; Forrest, Stephen R.; Perlov, Craig; Jackson, Warren; Taussig, Carl

    2003-12-01

    We demonstrate a nonvolatile, write-once-read-many-times (WORM) memory device employing a hybrid organic/inorganic semiconductor architecture consisting of thin film p-i-n silicon diode on a stainless steel substrate integrated in series with a conductive polymer fuse. The nonlinearity of the silicon diodes enables a passive matrix memory architecture, while the conductive polyethylenedioxythiophene:polystyrene sulfonic acid polymer serves as a reliable switch with fuse-like behavior for data storage. The polymer can be switched at ˜2 μs, resulting in a permanent decrease of conductivity of the memory pixel by up to a factor of 103. The switching mechanism is primarily due to a current and thermally dependent redox reaction in the polymer, limited by the double injection of both holes and electrons. The switched device performance does not degrade after many thousand read cycles in ambient at room temperature. Our results suggest that low cost, organic/inorganic WORM memories are feasible for light weight, high density, robust, and fast archival storage applications.

  7. Electron-hole recombination in disordered organic semiconductors: Validity of the Langevin formula

    Science.gov (United States)

    van der Holst, J. J. M.; van Oost, F. W. A.; Coehoorn, R.; Bobbert, P. A.

    2009-12-01

    Accurate modeling of electron-hole recombination in organic light-emitting diodes (OLEDs) is essential for developing a complete description of their functioning. Traditionally, the recombination rate is described by the Langevin formula, with a proportionality factor equal to the sum of the electron and hole mobilities. In the disordered organic semiconductors used in OLEDs these mobilities have been shown to depend strongly on the carrier densities and on the electric field. Moreover, the energetic disorder leads to percolating pathways for the electron and hole currents, which may or may not be correlated. To answer the question whether the Langevin formula is still valid under such circumstances we perform Monte Carlo simulations of the recombination rate for Gaussian energetic disorder. We vary the disorder energy, the temperature, the densities, and mobility ratio of electrons and holes, the electric field, and the type of correlation between the electron and hole energies. We find that at zero electric field the Langevin formula is surprisingly well obeyed, provided that a change in the charge-carrier mobilities due to the presence of charge carriers of the opposite type is taken into account. Deviations from the Langevin formula at finite electric field are small at the field scale relevant for OLED modeling.

  8. Coupling between electrolyte and organic semiconductor in electrolyte-gated organic field effect transistors (Conference Presentation)

    Science.gov (United States)

    Biscarini, Fabio; Di Lauro, Michele; Berto, Marcello; Bortolotti, Carlo A.; Geerts, Yves H.; Vuillaume, Dominique

    2016-11-01

    Organic field effect transistors (OFET) operated in aqueous environments are emerging as ultra-sensitive biosensors and transducers of electrical and electrochemical signals from a biological environment. Their applications range from detection of biomarkers in bodily fluids to implants for bidirectional communication with the central nervous system. They can be used in diagnostics, advanced treatments and theranostics. Several OFET layouts have been demonstrated to be effective in aqueous operations, which are distinguished either by their architecture or by the respective mechanism of doping by the ions in the electrolyte solution. In this work we discuss the unification of the seemingly different architectures, such as electrolyte-gated OFET (EGOFET), organic electrochemical transistor (OECT) and dual-gate ion-sensing FET. We first demonstrate that these architectures give rise to the frequency-dependent response of a synapstor (synapse-like transistor), with enhanced or depressed modulation of the output current depending on the frequency of the time-dependent gate voltage. This behavior that was reported for OFETs with embedded metal nanoparticles shows the existence of a capacitive coupling through an equivalent network of RC elements. Upon the systematic change of ions in the electrolyte and the morphology of the charge transport layer, we show how the time scale of the synapstor is changed. We finally show how the substrate plays effectively the role of a second bottom gate, whose potential is actually fixed by the pH/composition of the electrolyte and the gate voltage applied.

  9. P-doped organic semiconductor: Potential replacement for PEDOT:PSS in organic photodetectors

    Science.gov (United States)

    Herrbach, J.; Revaux, A.; Vuillaume, D.; Kahn, A.

    2016-08-01

    In this work, we present an alternative to the use of PEDOT:PSS as hole transport and electron blocking layers in organic photodetectors processed by solution. As Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is known to be sensitive to humidity, oxygen, and UV, removing this layer is essential for lifetime improvements. As a first step to achieving this goal, we need to find an alternative layer that fulfills the same role in order to obtain a working diode with similar or better performance. As a replacement, a layer of poly[(4,8-bis-(2-ethylhexyloxy)-benzo(1,2-b:4,5-b')dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2-6-diyl)] (PBDTTT-c) p-doped with the dopant tris-[1-(trifluoroethanoyl)-2-(trifluoromethyl)ethane-1,2-dithiolene] (Mo(tfd-COCF3)3) is used. This p-doped layer effectively lowers the hole injection barrier, and the low electron affinity of the polymer prevents the injection of electrons into the active layer. We show similar device performance under light and the improvements of detection performance with the doped layer in comparison with PEDOT:PSS, leading to a detectivity of 1.9 × 1013 cm (Hz)1/2 (W)-1, competitive with silicon diodes used in imaging applications. Moreover, contrary to PEDOT:PSS, no localization of the p-doped layer is needed, leading to a diode active area defined by the patterned electrodes.

  10. Investigation of defect states in organic semiconductors. Towards long term stable materials for organic photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Schafferhans, Julia

    2011-07-01

    In this work, the trap states in the conjugated polymer P3HT, often used as electron donor in organic bulk heterojunction solar cells, three commonly used fullerene based electron acceptors and P3HT:PC{sub 61}BM blends were investigated. Concerning the lifetime of organic solar cells the influence of oxygen on P3HT and P3HT:PC{sub 61}BM blends was studied. Fractional TSC measurements on P3HT diodes revealed a quasi-continuous trap distribution. The deeper traps exhibited a strong dependence on oxygen. Exposure of the P3HT diodes to oxygen, ambient air and synthetic (dry) air all revealed an increase of the deeper traps density with exposure time in the same manner. While the lower limit of the trap density in non aged P3HT samples was in the range of (1.0-1.2) x 10{sup 22} m{sup -3}, it was more than doubled after an exposure of 50 h to air. An increase of the trap density with oxygen exposure time was also seen in the Q-DLTS measurements accompanied with an increase of the temperature dependence of the emission rates. Due to the raise in density of the deeper traps, the charge carrier mobility in P3HT significantly decreased, as revealed by photo-CELIV measurements, resulting in a loss in mobility of about two orders of magnitude after 100 h exposure to synthetic air. This effect was partially reversible by applying vacuum to the sample for several hours or, more significantly, by a thermal treatment of the devices in nitrogen atmosphere. The trap states in the methanofullerenes PC{sub 61}BM, bisPC{sub 61}BM and PC71BM were investigated by TSC measurements. PC{sub 61}BM yielded a broad quasi-continuous trap distribution with the maximum of the distribution at about 75 meV. The comparison of the TSC spectra of the three methanofullerenes exhibited significant differences in the trap states with higher activation energies of the most prominent traps in bisPC{sub 61}BM and PC71BM compared to PC{sub 61}BM. The lower limit of the trap density of all of the three

  11. Field-effect transistors with vacuum-deposited organic-inorganic perovskite films as semiconductor channels

    Science.gov (United States)

    Matsushima, Toshinori; Yasuda, Takeshi; Fujita, Katsuhiko; Adachi, Chihaya

    2016-12-01

    Films of the organic-inorganic layered perovskite (C6H5C2H4NH3)2SnI4 were vacuum-deposited on substrates heated at various temperatures (Tsub) to investigate the influence of Tsub on their film quality and transistor performance (hole mobilities, threshold voltages, and current on/off ratios). Appropriate substrate heating at Tsub = 60 °C during vacuum deposition led to better-developed perovskite films with larger grains. These films exhibited the best transistor performance in comparison with films fabricated at the other Tsub. The transistor performance was further enhanced by reducing perovskite semiconductor thickness (t) because of a reduction of bulk resistance in a top-contact/bottom-gate transistor structure. By utilizing the optimized Tsub of 60 °C and t of 31 nm, we obtained the most improved hole mobility of 0.78 ± 0.24 cm2/V s, about 5000 times the hole mobilities of our initial transistors fabricated at Tsub = 24 °C and t = 50 nm.

  12. Strain-induced vertical self-organization of semiconductor quantum dots: A computational study

    Energy Technology Data Exchange (ETDEWEB)

    Shtinkov, N., E-mail: nshtinkov@uottawa.ca [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa (Ontario) K1N 6N5 (Canada)

    2013-12-28

    Atomistic strain simulations based on the valence force field method are employed to study the vertical arrangements of semiconductor quantum dot (QD) multilayers. The effects of the QD shape, dimensions, and materials parameters are systematically investigated, varying independently the following parameters: spacer width H, QD lateral spacing D, base b, and height h, slope of the side facets, elastic properties of the dot and the substrate materials, and lattice mismatch between the dot and the substrate. The transition between vertically aligned and anti-aligned structures is found to be determined mainly by the ratios H/D and b/D, as well as by the strain anisotropy of the substrate and to a lesser extent of the QD. The dependence on the QD height h is significant only for steep side facets and large aspect ratios h/b, and the effects of the lattice mismatch strain and the bulk elastic moduli are found to be negligible. The comparison with experimental data shows an excellent agreement with the results from the simulations, demonstrating that the presented analysis results in precise theoretical predictions for the vertical self-organization regime in a wide range of QD materials systems.

  13. Thermal stability and molecular ordering of organic semiconductor monolayers: effect of an anchor group.

    Science.gov (United States)

    Jones, Andrew O F; Knauer, Philipp; Resel, Roland; Ringk, Andreas; Strohriegl, Peter; Werzer, Oliver; Sferrazza, Michele

    2015-06-01

    The thermal stability and molecular order in monolayers of two organic semiconductors, PBI-PA and PBI-alkyl, based on perylene derivatives with an identical molecular structure except for an anchor group for attachment to the substrate in PBI-PA, are reported. In situ X-ray reflectivity measurements are used to follow the stability of these monolayers in terms of order and thickness as temperature is increased. Films have thicknesses corresponding approximately to the length of one molecule; molecules stand upright on the substrate with a defined structure. PBI-PA monolayers have a high degree of order at room temperature and a stable film exists up to 250 °C, but decomposes rapidly above 300 °C. In contrast, stable physisorbed PBI-alkyl monolayers only exist up to 100 °C. Above the bulk melting point at 200 °C no more order exists. The results encourage using anchor groups in monolayers for various applications as it allows enhanced stability at the interface with the substrate.

  14. A scale-bridging modeling approach for anisotropic organic molecules at patterned semiconductor surfaces.

    Science.gov (United States)

    Kleppmann, Nicola; Klapp, Sabine H L

    2015-02-14

    Hybrid systems consisting of organic molecules at inorganic semiconductor surfaces are gaining increasing importance as thin film devices for optoelectronics. The efficiency of such devices strongly depends on the collective behavior of the adsorbed molecules. In the present paper, we propose a novel, coarse-grained model addressing the condensed phases of a representative hybrid system, that is, para-sexiphenyl (6P) at zinc-oxide (ZnO). Within our model, intermolecular interactions are represented via a Gay-Berne potential (describing steric and van-der-Waals interactions) combined with the electrostatic potential between two linear quadrupoles. Similarly, the molecule-substrate interactions include a coupling between a linear molecular quadrupole to the electric field generated by the line charges characterizing ZnO(10-10). To validate our approach, we perform equilibrium Monte Carlo simulations, where the lateral positions are fixed to a 2D lattice, while the rotational degrees of freedom are continuous. We use these simulations to investigate orientational ordering in the condensed state. We reproduce various experimentally observed features such as the alignment of individual molecules with the line charges on the surface, the formation of a standing uniaxial phase with a herringbone structure, as well as the formation of a lying nematic phase.

  15. Influence of structural fluctuations on lifetimes of adsorbate states at hybrid organic-semiconductor interfaces

    Science.gov (United States)

    Müller, M.; Sánchez-Portal, D.; Lin, H.; Fratesi, G.; Brivio, G. P.; Selloni, A.

    On the road towards a more realistic description of charge transfer processes at hybrid organic-semiconductor interfaces for photovoltaic applications we extend our first-principles scheme for the extraction of elastic linewidths to include the effects of structural fluctuations. Based on snapshots obtained from Car-Parinello molecular dynamics simulations at room temperature, we set up geometries in which dye molecules at interfaces are attached to a semi-infinite TiO2 substrate. The elastic linewidths are computed using a Green's function method. This effectively introduces the coupling to a continuum of states in the substrate. In particular we investigate catechol and isonicotinic acid on rutile(110) and anatase(101) at the level of semi-local density functional theory. We perform multiple calculations of linewidths and peak-positions associated with the adsorbate's frontier orbitals for different geometric configurations to obtain a time-averaged analysis of such physical properties. We compare the results from the considered systems to understand the effects of dynamics onto interfacial charge transfer and systematically assess the dependence of the extracted elastic lifetimes on the relative alignment between adsorbate and substrate states. This project has received funding from the European Union Seventh Framework Programme under Grant Agreement No. 607323 [THINFACE].

  16. Different electronic and charge-transport properties of four organic semiconductors Tetraazaperopyrenes derivatives

    Science.gov (United States)

    Shi, Yarui; Wei, Huiling; Liu, Yufang

    2015-03-01

    Tetraazaperopyrenes (TAPPs) derivatives are high-performance n-type organic semiconductor material families with the remarkable long-term stabilities. The charge carrier mobilities in TAPPs derivatives crystals were calculated by the density functional theory (DFT) method combined with the Marcus-Hush electron-transfer theory. The existence of considerable C-H…F-C bonding defines the conformation of the molecular structure and contributes to its stability. We illustrated how it is possible to control the electronic and charge-transport parameters of TAPPs derivatives as a function of the positions, a type of the substituents. It is found that the core substitution of TAPPs has a drastic influence on the charge-transport mobilities. The maximum electron mobility value of the core-brominated 2,9-bis (perfluoroalkyl)-substituted TAPPs is 0.521 cm2 V-1 s-1, which appear in the orientation angle 95° and 275°. The results demonstrate that the TAPPs with bromine substituents in ortho positions exhibit the best charge-transfer efficiency among the four different TAPP derivatives.

  17. Ion bombardment induced morphology modifications on self-organized semiconductor surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hofer, C. E-mail: christian.hofer@unileoben.ac.at; Abermann, S.; Teichert, C.; Bobek, T.; Kurz, H.; Lyutovich, K.; Kasper, E

    2004-02-01

    The successful generation of well ordered nanopatterns on III-V semiconductor surfaces by ion erosion initiated attempts to obtain similar effects on silicon surfaces. High resolution atomic-force microscopy (AFM) is used to quantify the morphological changes of self-organized silicon/germanium films on Si(0 0 1) during ion bombardment. A nanofaceted SiGe film exhibiting a checkerboard array of {l_brace}1 0 5{r_brace} faceted pyramids and pits was eroded by Ar{sup +} ions of 100-1000 eV under normal incidence. Two characteristic energy regimes have been found. For ion energies below 750 eV the pyramidal pits transform into shallow troughs before smaller craters form. At ion energies of 750 eV and above, a significant smoothening of the surface was observed, finally resulting in a vanishing of the pattern. The influence of the initial pattern and the ion energy on the morphological changes are compared for different SiGe-films. Since at low ion energies the checkerboard array of {l_brace}1 0 5{r_brace} pyramids and pits could be transferred into the silicon substrate this procedure illustrates an alternative way to nanostructure silicon surfaces by ion erosion.

  18. Improving the Stability of Organic Semiconductors: Distortion Energy versus Aromaticity in Substituted Bistetracene

    KAUST Repository

    Thomas, Simil

    2016-11-15

    Polycyclic aromatic hydrocarbons (PAHs) have been widely explored as molecular semiconductors in organic electronic devices such as field-effect transistors or solar cells. However, their tendency to undergo photooxidation is a primary limitation to their practical applications. Bistetracene derivatives have recently been demonstrated to possess much larger photo oxidation stability than the widely investigated pentacene and rubrene, while maintaining high charge-carrier mobilities. Here, using several levels of density functional theory, we identify the origin of the increased stability of bistetracene with respect to molecular oxygen by systematically investigating the [4 + 2] cycloaddition (Diels Alder) photooxidation reaction mechanism. Importantly, our computational results indicate that endoperoxide formation in bis(2-(trimethylsilyl)ethynyl) bistetracene (BT) occurs not on the ring with least aromaticity, but rather on the ring with smallest distortion energy. This feature was subsequently confirmed by experimental NMR analyses. The oxidation activation barriers of bistetracene, pentacene, and rubrene are found to be 17.7, 13.6, and 14.4 kcal/mol, respectively, in agreement with the observed order of stability of these molecules with respect to oxidation reactions in solution. In the cases of BT and pentacene, the rates of electron transfer to create charged species (PAH(+) and O-2) are at least two orders of magnitude lower than that of the charge recombination process (back to PAH and O-2); for rubrene, both of these processes are calculated to be of the same order of magnitude, in agreement with experimental electron paramagnetic resonance spectroscopy observations.

  19. Tuning polymorphism and orientation in organic semiconductor thin films via post-deposition processing.

    Science.gov (United States)

    Hiszpanski, Anna M; Baur, Robin M; Kim, Bumjung; Tremblay, Noah J; Nuckolls, Colin; Woll, Arthur R; Loo, Yueh-Lin

    2014-11-05

    Though both the crystal structure and molecular orientation of organic semiconductors are known to impact charge transport in thin-film devices, separately accessing different polymorphs and varying the out-of-plane molecular orientation is challenging, typically requiring stringent control over film deposition conditions, film thickness, and substrate chemistry. Here we demonstrate independent tuning of the crystalline polymorph and molecular orientation in thin films of contorted hexabenzocoronene, c-HBC, during post-deposition processing without the need to adjust deposition conditions. Three polymorphs are observed, two of which have not been previously reported. Using our ability to independently tune the crystal structure and out-of-plane molecular orientation in thin films of c-HBC, we have decoupled and evaluated the effects that molecular packing and orientation have on device performance in thin-film transistors (TFTs). In the case of TFTs comprising c-HBC, polymorphism and molecular orientation are equally important; independently changing either one affects the field-effect mobility by an order of magnitude.

  20. Electrochemical Capture and Release of CO2 in Aqueous Electrolytes Using an Organic Semiconductor Electrode.

    Science.gov (United States)

    Apaydin, Dogukan H; Gora, Monika; Portenkirchner, Engelbert; Oppelt, Kerstin T; Neugebauer, Helmut; Jakesova, Marie; Głowacki, Eric D; Kunze-Liebhäuser, Julia; Zagorska, Malgorzata; Mieczkowski, Jozef; Sariciftci, Niyazi Serdar

    2017-04-19

    Developing efficient methods for capture and controlled release of carbon dioxide is crucial to any carbon capture and utilization technology. Herein we present an approach using an organic semiconductor electrode to electrochemically capture dissolved CO2 in aqueous electrolytes. The process relies on electrochemical reduction of a thin film of a naphthalene bisimide derivative, 2,7-bis(4-(2-(2-ethylhexyl)thiazol-4-yl)phenyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (NBIT). This molecule is specifically tailored to afford one-electron reversible and one-electron quasi-reversible reduction in aqueous conditions while not dissolving or degrading. The reduced NBIT reacts with CO2 to form a stable semicarbonate salt, which can be subsequently oxidized electrochemically to release CO2. The semicarbonate structure is confirmed by in situ IR spectroelectrochemistry. This process of capturing and releasing carbon dioxide can be realized in an oxygen-free environment under ambient pressure and temperature, with uptake efficiency for CO2 capture of ∼2.3 mmol g(-1). This is on par with the best solution-phase amine chemical capture technologies available today.

  1. Use of a hexapod in diffraction measurements of substrate-supported crystals of organic semiconductors.

    Science.gov (United States)

    Yang, Lin; Yang, Hoichang

    2009-11-01

    Thin films of organic semiconductor prepared on substrates generally contain crystals that have one common crystal plane parallel to the substrate but random in-plane orientations. In diffraction measurements of these structures, it is often required to anchor the X-ray beam on a fixed spot on the sample, such as an optically visible crystallite or island. Here, a hexapod is used in place of a traditional multi-circle diffractometer to perform area-detector-based diffraction measurements on an actual device that contains 6,13-bis(triisopropyl-silyethynyl)-pentacene (TIPS-pentacene) crystals. The hexapod allows for sample rotations about any user-defined rotation center. Two types of complex sample motions have been programmed to characterize the structure of the TIPS-pentacene crystal: an in-plane powder average has been performed at a fixed grazing-incident angle to determine the lattice parameters of the crystal; then the in-plane component of the scattering vector was continuously rotated in transmission geometry to determine the local crystal orientation.

  2. Calculation of the spectrum of quasiparticle electron excitations in organic molecular semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tikhonov, E. V., E-mail: tikhonov@mig.phys.msu.ru [Moscow State University (Russian Federation); Uspenskii, Yu. A. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Khokhlov, D. R. [Moscow State University (Russian Federation)

    2015-06-15

    A quasiparticle electronic spectrum belongs to the characteristics of nanoobjects that are most important for applications. The following methods of calculating the electronic spectrum are analyzed: the Kohn-Sham equations of the density functional theory (DFT), the hybrid functional method, the GW approximation, and the Lehmann approximation used in the spectral representation of one-electron Green’s function. The results of these approaches are compared with the data of photoemission measurements of benzene, PTCDA, and phthalocyanine (CuPc, H{sub 2}Pc, FePc, PtPc) molecules, which are typical representatives of organic molecular semiconductors (OMS). This comparison demonstrates that the Kohn-Sham equations of DFT incorrectly reproduce the electronic spectrum of OMS. The hybrid functional method correctly describes the spectrum of the valence and conduction bands; however, the HOMO-LUMO gap width is significantly underestimated. The correct gap width is obtained in both the GW approximation and the Lehmann approach, and the total energy in this approach can be calculated in the local density approximation of DFT.

  3. Modeling of the transient mobility in disordered organic semiconductors with a Gaussian density of states

    Science.gov (United States)

    Germs, W. Chr.; van der Holst, J. J. M.; van Mensfoort, S. L. M.; Bobbert, P. A.; Coehoorn, R.

    2011-10-01

    The charge-carrier mobility in organic semiconductors is often studied using non-steady-state experiments. However, energetic disorder can severely hamper the analysis due to the occurrence of a strong time dependence of the mobility caused by carrier relaxation. The multiple-trapping model is known to provide an accurate description of this effect. However, the value of the conduction level energy and the hopping attempt rate, which enter the model as free parameters, are not a priori known for a given material. We show how for the case of a Gaussian density of states both parameters can be deduced from the parameter values used to describe the measured dc current-voltage characteristics within the framework of the extended Gaussian disorder model. The approach is validated using three-dimensional Monte Carlo modeling. In the analysis, the charge-density dependence of the time-dependent mobility is included. The model is shown to successfully predict the low-frequency differential capacitance of sandwich-type devices based on a polyfluorene copolymer.

  4. Mechanistic Studies of Charge Injection from Metallic Electrodes into Organic Semiconductors Mediated by Ionic Functionalities: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Thuc-Quyen [UCSB; Bazan, Guillermo [UCSB; Mikhailovsky, Alexander [UCSB

    2014-04-15

    Metal-organic semiconductor interfaces are important because of their ubiquitous role in determining the performance of modern electronics such as organic light emitting diodes (OLEDs), fuel cells, batteries, field effect transistors (FETs), and organic solar cells. Interfaces between metal electrodes required for external wiring to the device and underlying organic structures directly affect the charge carrier injection/collection efficiency in organic-based electronic devices primarily due to the mismatch between energy levels in the metal and organic semiconductor. Environmentally stable and cost-effective electrode materials, such as aluminum and gold typically exhibit high potential barriers for charge carriers injection into organic devices leading to increased operational voltages in OLEDs and FETs and reduced charge extraction in photovoltaic devices. This leads to increased power consumption by the device, reduced overall efficiency, and decreased operational lifetime. These factors represent a significant obstacle for development of next generation of cheap and energy-efficient components based on organic semiconductors. It has been noticed that introduction of organic materials with conjugated backbone and ionic pendant groups known as conjugated poly- and oligoelectrolytes (CPEs and COEs), enables one to reduce the potential barriers at the metal-organic interface and achieve more efficient operation of a device, however exact mechanisms of the phenomenon have not been understood. The goal of this project was to delineate the function of organic semiconductors with ionic groups as electron injection layers. The research incorporated a multidisciplinary approach that encompassed the creation of new materials, novel processing techniques, examination of fundamental electronic properties and the incorporation of the resulting knowledgebase into development of novel organic electronic devices with increased efficiency, environmental stability, and reduced

  5. High performance printed N and P-type OTFTs enabling digital and analog complementary circuits on flexible plastic substrate

    Science.gov (United States)

    Jacob, S.; Abdinia, S.; Benwadih, M.; Bablet, J.; Chartier, I.; Gwoziecki, R.; Cantatore, E.; van Roermund, A. H. M.; Maddiona, L.; Tramontana, F.; Maiellaro, G.; Mariucci, L.; Rapisarda, M.; Palmisano, G.; Coppard, R.

    2013-06-01

    This paper presents a printed organic complementary technology on flexible plastic substrate with high performance N and P-type Organic Thin Film Transistors (OTFTs), based on small-molecule organic semiconductors in solution. Challenges related to the integration of both OTFT types in a common complementary flow are addressed, showing the importance of surface treatments. Stability on single devices and on an elementary complementary digital circuit (ring oscillator) is studied, demonstrating that a robust and reliable flow with high electrical performances can be established for printed organic devices. These devices are used to manufacture several analog and digital building blocks. The design is carried out using a model specifically developed for this technology, and taking into account the parametric variability. High-frequency measurements of printed envelope detectors show improved speed performance, resulting from the high mobility of the OTFTs. In addition, a compact dynamic flip-flop and a low-offset comparator are demonstrated, thanks to availability of both n-type and p-type OTFTs in the technology. Measurement results are in good agreement with the simulations. The circuits presented establish a complete library of building blocks for the realization of a printed RFID tag.

  6. Activation energy spectra: insights into transport limitations of organic semiconductors and photovoltaic cells

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Ziqi; Nardes, Alexandre M.; Van de Lagemaat, Jao; Gregg, Brian A. [National Renewable Energy Laboratory, Golden, CO (United States)

    2012-03-07

    Some mechanisms of charge transport in organic semiconductors and organic photovoltaic (OPV) cells can be distinguished by their predicted change in activation energy for the current, E{sub a}, versus applied field, F. E{sub a} versus F is measured first in pure films of commercially available regioregular poly(3-hexylthiophene) (P3HT) and in the same P3HT treated to reduce its charged defect density. The former shows a Poole-Frenkel (PF)-like decrease in E{sub a} at low F, which then plateaus at higher F. The low defect material does not exhibit PF behavior and E{sub a} remains approximately constant. Upon addition of [6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM), however, both materials show a large increase in E{sub a} and exhibit PF-like behavior over the entire field range. These results are explained with a previously proposed model of transport that considers both the localized random disorder in the energy levels and the long-range electrostatic fluctuations resulting from charged defects. Activation energy spectra in working OPV cells show that the current is injection-limited over most of the voltage range but becomes transport-limited, with a large peak in E{sub a}, near the open circuit photovoltage. This causes a decrease in fill factor, which may be a general limitation in such solar cells. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Chemical-state analysis of organic semiconductors using soft X-ray absorption spectroscopy combined with first-principles calculation.

    Science.gov (United States)

    Natsume, Yutaka; Kohno, Teiichiro; Minakata, Takashi; Konishi, Tokuzo; Gullikson, Eric M; Muramatsu, Yasuji

    2012-02-16

    The chemical states of organic semiconductors were investigated by total-electron-yield soft X-ray absorption spectroscopy (TEY-XAS) and first-principles calculations. The organic semiconductors, pentacene (C(22)H(14)) and pentacenequinone (C(22)H(12)O(2)), were subjected to TEY-XAS and the experimental spectra obtained were compared with the 1s core-level excited spectra of C and O atoms, calculated by a first-principles planewave pseudopotential method. Excellent agreement between the measured and the calculated spectra were obtained for both materials. Using this methodology, we examined the chemical states of the aged pentacene, and confirmed that both C-OH and C═O chemical bonds are generated by exposure to air. This result implies that not only oxygen but also humidity causes pentacene oxidation.

  8. Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Bory, Benjamin F.; Meskers, Stefan C. J., E-mail: s.c.j.meskers@tue.nl [Molecular Materials and Nanosystems and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Rocha, Paulo R. F. [Instituto de Telecomunicações, Av. Rovisco, Pais, 1, 1049-001 Lisboa, Portugal and Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany); Gomes, Henrique L. [Instituto de Telecomunicações, Av. Rovisco, Pais, 1, 1049-001 Lisboa, Portugal and Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal); Leeuw, Dago M. de [Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany)

    2015-11-28

    Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 10{sup 17 }m{sup −2}. We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching.

  9. Unipolar resistive switching in metal oxide/organic semiconductor non-volatile memories as a critical phenomenon

    Science.gov (United States)

    Bory, Benjamin F.; Rocha, Paulo R. F.; Gomes, Henrique L.; de Leeuw, Dago M.; Meskers, Stefan C. J.

    2015-11-01

    Diodes incorporating a bilayer of an organic semiconductor and a wide bandgap metal oxide can show unipolar, non-volatile memory behavior after electroforming. The prolonged bias voltage stress induces defects in the metal oxide with an areal density exceeding 1017 m-2. We explain the electrical bistability by the coexistence of two thermodynamically stable phases at the interface between an organic semiconductor and metal oxide. One phase contains mainly ionized defects and has a low work function, while the other phase has mainly neutral defects and a high work function. In the diodes, domains of the phase with a low work function constitute current filaments. The phase composition and critical temperature are derived from a 2D Ising model as a function of chemical potential. The model predicts filamentary conduction exhibiting a negative differential resistance and nonvolatile memory behavior. The model is expected to be generally applicable to any bilayer system that shows unipolar resistive switching.

  10. Heteroepitaxial growth of 3-5 semiconductor compounds by metal-organic chemical vapor deposition for device applications

    Science.gov (United States)

    Collis, Ward J.; Abul-Fadl, Ali

    1988-01-01

    The purpose of this research is to design, install and operate a metal-organic chemical vapor deposition system which is to be used for the epitaxial growth of 3-5 semiconductor binary compounds, and ternary and quaternary alloys. The long-term goal is to utilize this vapor phase deposition in conjunction with existing current controlled liquid phase epitaxy facilities to perform hybrid growth sequences for fabricating integrated optoelectronic devices.

  11. Photocatalytic oxidation of organic compounds in a hybrid system composed of a molecular catalyst and visible light-absorbing semiconductor.

    Science.gov (United States)

    Zhou, Xu; Li, Fei; Li, Xiaona; Li, Hua; Wang, Yong; Sun, Licheng

    2015-01-14

    Photocatalytic oxidation of organic compounds proceeded efficiently in a hybrid system with ruthenium aqua complexes as catalysts, BiVO4 as a light absorber, [Co(NH3)5Cl](2+) as a sacrificial electron acceptor and water as an oxygen source. The photogenerated holes in the semiconductor are used to oxidize molecular catalysts into the high-valent Ru(IV)=O intermediates for 2e(-) oxidation.

  12. 30.1 8b thin-film microprocessor using a hybrid oxide-organic complementary technology with inkjet-printed P2ROM memory

    NARCIS (Netherlands)

    Myny, K.; Smout, S.; Rockelé, M.; Bhoolokam, A.; Ke, T.H.; Steudel, S.; Obata, K.; Marinkovic, M.; Pham, D.V.; Hoppe, A.; Gulati, A.; Rodriguez, F.G.; Cobb, B.; Gelinck, G.H.; Genoe, J.; Dehaene, W.; Heremans, P.

    2014-01-01

    We present an 8b general-purpose microprocessor realized in a hybrid oxide-organic complementary thin-film technology. The n-type transistors are based on a solution-processed n-type metal-oxide semiconductor, and the p-type transistors use an organic semiconductor. As compared to previous work util

  13. 30.1 8b thin-film microprocessor using a hybrid oxide-organic complementary technology with inkjet-printed P2ROM memory

    NARCIS (Netherlands)

    Myny, K.; Smout, S.; Rockelé, M.; Bhoolokam, A.; Ke, T.H.; Steudel, S.; Obata, K.; Marinkovic, M.; Pham, D.V.; Hoppe, A.; Gulati, A.; Rodriguez, F.G.; Cobb, B.; Gelinck, G.H.; Genoe, J.; Dehaene, W.; Heremans, P.

    2014-01-01

    We present an 8b general-purpose microprocessor realized in a hybrid oxide-organic complementary thin-film technology. The n-type transistors are based on a solution-processed n-type metal-oxide semiconductor, and the p-type transistors use an organic semiconductor. As compared to previous work

  14. Probing Electronic, Structural, and Charge Transfer Properties of Organic Semiconductor/Inorganic Oxide Interfaces Using Field-Effect Transistors

    Science.gov (United States)

    Spalenka, Josef Wade

    Interfaces between organic semiconductors and inorganic oxides provide the functionality for devices including field-effect transistors (FETs) and organic photovoltaics. Organic FETs are sensitive to the physical structure and electronic properties of the few molecular layers of material at the interface between the semiconducting channel and the gate dielectric, and provide quantitative information such as the field-effect mobility of charge carriers and the concentration of trapped charge. In this thesis, FET interfaces between organic small-molecule semiconductors and SiO2, and donor/acceptor interfaces between organic small-molecules and the wide bandgap semiconductor ZnO are studied using electrical measurements of field-effect transistor devices. Monolayer-scale films of dihexyl sexithiophene are shown to have higher hole mobility than other monolayer organic semiconductors, and the origin of the high mobility is discussed. Studies of the crystal structure of the monolayer using X-ray structural probes and atomic force microscopy reveal the crystal structure is different in the monolayer regime compared to thicker films and bulk crystals. Progress and remaining challenges are discussed for in situ X-ray diffraction studies of the dynamic changes in the local crystal structure in organic monolayers due to charge carriers generated during the application of electric fields from the gate electrode in working FETs. Studies were conducted of light sensitive organic/inorganic interfaces that are modified with organic molecules grafted to the surface of ZnO nanoparticles and thin films. These interfaces are models for donor/acceptor interfaces in photovoltaics. The process of exciton dissociation at the donor/acceptor interface was sensitive to the insulating or semiconducting molecules grafted to the ZnO, and the photoinduced charge transfer process is measured by the threshold voltage shift of FETs during illumination. Charge transfer between light sensitive donor

  15. Nanoscopic oxidation of p-type and un-doped Si (100) surfaces using un-externally biased atomic force microscope tips (AFM) in the presence of selected organic solvents

    Science.gov (United States)

    McCausland, Jeffrey; Withanage, Sajeevi; Mallik, Robert; Lyuksyutov, Sergei

    A conductive un-biased AFM tip oscillating above p-type or un-doped Si (100) treated with toluene, butan-2-ol, and propan-2-ol creates nanostructures ranging in height from 1-100 nm. The tip was oscillated in ambient conditions (30-70% Rel. Humidity) at frequencies in the 102 kHz range. It was repeatable with various concentrations of solvent in aqueous solution. It is suggested that mechanical oscillations of the AFM tip polarizes the solvent molecules deposited on the surface resulting in electron transfer from the tip to the surface followed by feature formation. This process effectively creates an electrochemical cell at the microscopic level and the miscibility of the solvents is the key to enabling the process. Species which ionize during the process may be consumed in irreversible reactions whereas the alcohols act as catalysts and are not consumed. The influence of boron defects in the Si substrates is also discussed. It appears that the observed oxidation is different from all other similar reported phenomena including local anodic oxidation, and chemo-mechanical lithographic techniques utilizing AFM.

  16. Modeling space-charge-limited currents in organic semiconductors: Extracting trap density and mobility

    KAUST Repository

    Dacuña, Javier

    2011-11-28

    We have developed and have applied a mobility edge model that takes drift and diffusion currents to characterize the space-charge-limited current in organic semiconductors into account. The numerical solution of the drift-diffusion equation allows the utilization of asymmetric contacts to describe the built-in potential within the device. The model has been applied to extract information of the distribution of traps from experimental current-voltage measurements of a rubrene single crystal from Krellner showing excellent agreement across several orders of magnitude in the current. Although the two contacts are made of the same metal, an energy offset of 580 meV between them, ascribed to differences in the deposition techniques (lamination vs evaporation) was essential to correctly interpret the shape of the current-voltage characteristics at low voltage. A band mobility of 0.13cm 2V-1s-1 for holes is estimated, which is consistent with transport along the long axis of the orthorhombic unit cell. The total density of traps deeper than 0.1 eV was 2.2×1016cm -3. The sensitivity analysis and error estimation in the obtained parameters show that it is not possible to accurately resolve the shape of the trap distribution for energies deeper than 0.3 eV or shallower than 0.1 eV above the valence-band edge. The total number of traps deeper than 0.3 eV, however, can be estimated. Contact asymmetry and the diffusion component of the current play an important role in the description of the device at low bias and are required to obtain reliable information about the distribution of deep traps. © 2011 American Physical Society.

  17. Transparent Oxide Semiconductors for Emerging Electronics

    KAUST Repository

    Caraveo-Frescas, Jesus Alfonso

    2013-11-01

    demonstrated by the fabrication of hybrid ferroelectric field effect transistors composed of organic ferroelectric layer polyvinylidene fluoride trifluoroethylene and inorganic p-type semiconductor tin monoxide. Both rigid and flexible devices are demonstrated, showing the advantages of low temperature oxides over polymer semiconductors by achieving much better performance, such as order of magnitude higher hole mobility.

  18. Azine- and Azole-Functionalized Oligo´ and Polythiophene Semiconductors for Organic Thin-Film Transistors

    Directory of Open Access Journals (Sweden)

    Rocío Ponce Ortiz

    2010-03-01

    Full Text Available In the organic electronics research field, several strategies have been used to modulate the transport properties of thiophene-derived semiconductors via sequential functionalization of their π-conjugated cores. This review summarizes the major design and synthetic strategies for tuning thiophene-containing small molecule and polymer properties by introducing electron-deficient nitrogen-containing azine and azole moieties. Several examples are presented which elucidate the structural, optical, and electronic consequences of incorporating these electron-deficient fragments in the conjugated skeletons, particularly relating to applications in organic thin-film transistors.

  19. Measurement of the Charge Carrier Mobility in MEH-PPV and MEH-PPV-POSS Organic Semiconductor Films

    Science.gov (United States)

    Romanov, I. V.; Voitsekhovskii, A. V.; Dyagterenko, K. M.; Kopylova, T. N.; Kokhanenko, A. P.; Nikonova, E. N.

    2015-03-01

    The values of the charge carrier mobility in organic semiconductor materials (MEH-PPV, MEH-PPV-POSS) are obtained on the basis of an analysis of the relaxation curves of transient electroluminescence in organic light-emitting diodes (OLEDs). The data on the mobility of charge carriers are analyzed according to the Poole-Frenkel model using the dependences of the charge carrier mobility on the electric field. Physical interpretation of the transport phenomena in OLED structures based on MEH-PPV and MEH-PPV-POSS is given.

  20. Chemistry and electronic properties of metal-organic semiconductor interfaces: Fe and Co on CuPc

    Energy Technology Data Exchange (ETDEWEB)

    Aristov, Victor; Molodtsova, Olga; Knupfer, Martin [IFW Dresden, D-01069 Dresden (Germany); Ossipyan, Yurii [Institute of Solid State Physics,sian Academy of Sciences, Chernogolovka, Moscow (Russian Federation); Doyle, Bryan [TASC-INFM Laboratory, Trieste (Italy); Nannarone, Stefano [TASC-INFM Laboratory, Trieste (Italy); Dipartimento di Ingegneria dei Materiali ed Amb., Universita di Modena (Italy)

    2007-07-01

    The creation of a spin transistor based on a semiconductor was proposed in 1990 by Datta and Das. Nowadays the attractive idea to create a spin-transistor based on an organic semiconductor thin film (OMTF) has been proposed. The main problem in the development of such a device is to produce ferromagnetic metallic contacts as an injector of spin-polarized electrons into OMTF and as a drain of these spinpolarized electrons from the channel. This problem could be solved by fabrication and investigation of contacts such as Fe(Co,Ni) thin films to an OMTF. In this contribution we present the results of extensive investigations of chemistry and electronic properties of the interface formation between Fe(Co) and the archetypical organic semiconductor copper phthalocyanine (CuPc). The studies were performed by means of core-level and valence-band high-resolution photoemission electron spectroscopy as well as by near-edge X-ray absorption fine structure and using the synchrotron radiation facility ELETTRA (Italy).

  1. Bulk charge carrier transport in push-pull type organic semiconductor.

    Science.gov (United States)

    Karak, Supravat; Liu, Feng; Russell, Thomas P; Duzhko, Volodimyr V

    2014-12-10

    Operation of organic electronic and optoelectronic devices relies on charge transport properties of active layer materials. The magnitude of charge carrier mobility, a key efficiency metrics of charge transport properties, is determined by the chemical structure of molecular units and their crystallographic packing motifs, as well as strongly depends on the film fabrication approaches that produce films with different degrees of anisotropy and structural order. Probed by the time-of-flight and grazing incidence X-ray diffraction techniques, bulk charge carrier transport, molecular packing, and film morphology in different structural phases of push-pull type organic semiconductor, 7,7'-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene-2,6-diyl)bis(6-fluoro-4-(5'-hexyl-[2,2'-bithiophen]-5yl)benzo[c][1,2,5] thiadiazole), one of the most efficient small-molecule photovoltaic materials to-date, are described herein. In the isotropic phase, the material is ambipolar with high mobilities for a fluid state. The electron and hole mobilities at the phase onset at 210.78 °C are 1.0 × 10(-3) cm(2)/(V s) and 6.5 × 10(-4) cm(2)/(V s), respectively. Analysis of the temperature and electric field dependences of the mobilities in the framework of Gaussian disorder formalism suggests larger energetic and positional disorder for electron transport sites. Below 210 °C, crystallization into a polycrystalline film with a triclinic unit cell symmetry and high degree of anisotropy leads to a 10-fold increase of hole mobility. The mobility is limited by the charge transfer along the direction of branched alkyl side chains. Below 90 °C, faster cooling rates produce even higher hole mobilities up to 2 × 10(-2) cm(2)/(V s) at 25 °C because of the more isotropic orientations of crystalline domains. These properties facilitate in understanding efficient material performance in photovoltaic devices and will guide further development of materials and devices.

  2. Development of nanostructured and surface modified semiconductors for hybrid organic-inorganic solar cells.

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Julia, W. P.

    2008-09-01

    Solar energy conversion is increasingly being recognized as one of the principal ways to meet future energy needs without causing detrimental environmental impact. Hybrid organic-inorganic solar cells (SCs) are attracting particular interest due to the potential for low cost manufacturing and for use in new applications, such as consumer electronics, architectural integration and light-weight sensors. Key materials advantages of these next generation SCs over conventional semiconductor SCs are in design opportunities--since the different functions of the SCs are carried out by different materials, there are greater materials choices for producing optimized structures. In this project, we explore the hybrid organic-inorganic solar cell system that consists of oxide, primarily ZnO, nanostructures as the electron transporter and poly-(3-hexylthiophene) (P3HT) as the light-absorber and hole transporter. It builds on our capabilities in the solution synthesis of nanostructured semiconducting oxide arrays to this photovoltaic (PV) technology. The three challenges in this hybrid material system for solar applications are (1) achieving inorganic nanostructures with critical spacing that matches the exciton diffusion in the polymer, {approx} 10 nm, (2) infiltrating the polymer completely into the dense nanostructure arrays, and (3) optimizing the interfacial properties to facilitate efficient charge transfer. We have gained an understanding and control over growing oriented ZnO nanorods with sub-50 nm diameters and the required rod-to-rod spacing on various substrates. We have developed novel approaches to infiltrate commercially available P3HT in the narrow spacing between ZnO nanorods. Also, we have begun to explore ways to modify the interfacial properties. In addition, we have established device fabrication and testing capabilities at Sandia for prototype devices. Moreover, the control synthesis of ZnO nanorod arrays lead to the development of an efficient anti

  3. Large-area bi-component processing of organic semiconductors by spray deposition and spin coating with orthogonal solvents

    Energy Technology Data Exchange (ETDEWEB)

    Treossi, Emanuele; Liscio, Andrea; Palermo, Vincenzo [Consiglio Nazionale delle Ricerche, Istituto per la Sintesi Organica e la Fotoreattivita, Bologna (Italy); Feng, Xinliang; Muellen, Klaus [Max-Planck Institute for Polymer Research, Mainz (Germany); Samori, Paolo [Universite Louis Pasteur, Nanochemistry Laboratory, ISIS-CNRS, Strasbourg (France); Consiglio Nazionale delle Ricerche, Istituto per la Sintesi Organica e la Fotoreattivita, Bologna (Italy)

    2009-04-15

    Micrometre-thick uniform layers of a polymeric semiconductor (poly(3-hexylthiophene), P3HT) have been fabricated from solution by spray deposition making use of a commercial airbrush. Multi-scale characterization by optical microscopy and atomic force microscopy revealed the formation of smooth layers featuring reproducible patterns of spatially correlated micron-sized holes. This morphology was found to be uniform over the whole sample surface, on millimetre scale. On this micro-patterned P3HT layer an orthogonal solvent (i.e. a solvent which does not dissolve the P3HT) has been employed to deposit either by spin coating or by drop casting a second organic semiconductor. While spin-coated films exhibited nano-crystals of an alkylated perylene tetracarboxy diimide (PDI) preferentially grown into the micro-fabricated holes, drop-cast films displayed crystalline PDI fibres adsorbed on the patterned surface in random positions. (orig.)

  4. Large-area bi-component processing of organic semiconductors by spray deposition and spin coating with orthogonal solvents

    Science.gov (United States)

    Treossi, Emanuele; Liscio, Andrea; Feng, Xinliang; Palermo, Vincenzo; Müllen, Klaus; Samorì, Paolo

    2009-04-01

    Micrometre-thick uniform layers of a polymeric semiconductor (poly(3-hexylthiophene), P3HT) have been fabricated from solution by spray deposition making use of a commercial airbrush. Multi-scale characterization by optical microscopy and atomic force microscopy revealed the formation of smooth layers featuring reproducible patterns of spatially correlated micron-sized holes. This morphology was found to be uniform over the whole sample surface, on millimetre scale. On this micro-patterned P3HT layer an orthogonal solvent (i.e. a solvent which does not dissolve the P3HT) has been employed to deposit either by spin coating or by drop casting a second organic semiconductor. While spin-coated films exhibited nano-crystals of an alkylated perylene tetracarboxy diimide (PDI) preferentially grown into the micro-fabricated holes, drop-cast films displayed crystalline PDI fibres adsorbed on the patterned surface in random positions.

  5. Quasi-perpetual discharge behaviour in p-type Ge-air batteries.

    Science.gov (United States)

    Ocon, Joey D; Kim, Jin Won; Abrenica, Graniel Harne A; Lee, Jae Kwang; Lee, Jaeyoung

    2014-11-07

    Metal-air batteries continue to become attractive energy storage and conversion systems due to their high energy and power densities, safer chemistries, and economic viability. Semiconductor-air batteries - a term we first define here as metal-air batteries that use semiconductor anodes such as silicon (Si) and germanium (Ge) - have been introduced in recent years as new high-energy battery chemistries. In this paper, we describe the excellent doping-dependent discharge kinetics of p-type Ge anodes in a semiconductor-air cell employing a gelled KOH electrolyte. Owing to its Fermi level, n-type Ge is expected to have lower redox potential and better electronic conductivity, which could potentially lead to a higher operating voltage and better discharge kinetics. Nonetheless, discharge measurements demonstrated that this prediction is only valid at the low current regime and breaks down at the high current density region. The p-type Ge behaves extremely better at elevated currents, evident from the higher voltage, more power available, and larger practical energy density from a very long discharge time, possibly arising from the high overpotential for surface passivation. A primary semiconductor-air battery, powered by a flat p-type Ge as a multi-electron anode, exhibited an unprecedented full discharge capacity of 1302.5 mA h gGe(-1) (88% anode utilization efficiency), the highest among semiconductor-air cells, notably better than new metal-air cells with three-dimensional and nanostructured anodes, and at least two folds higher than commercial Zn-air and Al-air cells. We therefore suggest that this study be extended to doped-Si anodes, in order to pave the way for a deeper understanding on the discharge phenomena in alkaline metal-air conversion cells with semiconductor anodes for specific niche applications in the future.

  6. Origin of Meyer-Neldel type compensation behavior in organic semiconductors at large carrier concentrations: Disorder versus thermodynamic description

    Science.gov (United States)

    Fishchuk, I. I.; Kadashchuk, A.; Mityashin, A.; Gavrilyuk, M. M.; Köhler, A.; Bässler, H.; Genoe, J.; Sitter, H.; Sariciftci, N. S.

    2014-12-01

    We have extended an effective medium approximation theory [Fishchuk, Kadashchuk, Genoe, Ullah, Sitter, Singh, Sariciftci, and Bässler, Phys. Rev. B 81, 045202 (2010), 10.1103/PhysRevB.81.045202] to investigate how polaron formation affects the Meyer-Neldel (MN) compensation behavior observed for temperature-dependent charge-carrier transport in disordered organic semiconductors at large carrier concentrations, as realized in organic field-effect transistors (OFETs). We show that the compensation behavior in organic semiconductor thin films can be consistently described for both nonpolaronic and polaronic hopping transport in the framework of the disorder formalism using either Miller-Abrahams or polaron Marcus rates, respectively, provided that the polaron binding energy is small compared to the width of the density of states (DOS) distribution in the system. We argue that alternative models based on thermodynamic reasoning, like the multiexcitation entropy (MEE) model, which assumes charge transport dominated by polarons with multiphonon processes and ignores the energy disorder, are inherently not applicable to describe adequately the charge-carrier transport in disordered organic semiconductors. We have suggested and realized a test experiment based on measurements of the compensation behavior for the temperature-dependent conductivity and mobility in OFET devices to check the applicability of these models. We point out that the MN behavior observed in thin-film OFETs has nothing to do with the genuine MN rule predicted by the MEE approach, but rather it is an apparent effect arising as a consequence of the functional dependence of the partial filling of the DOS in a disordered system with hopping transport. This fact is fully supported by experimental results. The apparent MN energy was found to depend also on the shape of the DOS distribution and polaron binding energy.

  7. Hall and thermoelectric evaluation of p-type InAs

    Energy Technology Data Exchange (ETDEWEB)

    Wagener, M.C., E-mail: magnus.wagener@nmmu.ac.z [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Wagener, V.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2009-12-15

    This paper compares the galvanometric and thermoelectric evaluation of the electrical characteristics of narrow gap semiconductors. In particular, the influence of a surface inversion layer is incorporated into the analysis of the temperature-dependent Hall and thermoelectric measurements of p-type InAs. The temperature at which the Seebeck coefficient of p-type material changes sign is shown to be unaffected by the presence of degenerate conduction paths. This finding consequently facilitated the direct determination of the acceptor density of lightly doped thin film InAs.

  8. Intrinsic spin and momentum relaxation in organic single-crystalline semiconductors probed by ESR and Hall measurements

    Science.gov (United States)

    Tsurumi, Junto; Häusermann, Roger; Watanabe, Shun; Mitsui, Chikahiko; Okamoto, Toshihiro; Matsui, Hiroyuki; Takeya, Jun

    Spin and charge momentum relaxation mechanism has been argued among organic semiconductors with various methods, devices, and materials. However, little is known in organic single-crystalline semiconductors because it has been hard to obtain an ideal organic crystal with an excellent crystallinity and controllability required for accurate measurements. By using more than 1-inch sized single crystals which are fabricated via contentious edge-casting method developed by our group, we have successfully demonstrated a simultaneous determination of spin and momentum relaxation time for gate-induced charges of 3,11-didecyldinaphtho[2,3- d:2',3'- d']benzo[1,2- b:4,5- b']dithiophene, by combining electron spin resonance (ESR) and Hall effect measurements. The obtained temperature dependences of spin and momentum relaxation times are in good agreement in terms of power law with a factor of approximately -2. It is concluded that Elliott-Yafet spin relaxation mechanism can be dominant at room temperature regime (200 - 300 K). Probing characteristic time scales such as spin-lattice, spin-spin, and momentum relaxation times, demonstrated in the present work, would be a powerful tool to elucidate fundamental spin and charge transport mechanisms. We acknowledge the New Energy and Industrial Technology Developing Organization (NEDO) for financial support.

  9. Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors

    KAUST Repository

    Ryno, Sean M.

    2016-05-16

    The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density.

  10. Impact of Molecular Orientation and Packing Density on Electronic Polarization in the Bulk and at Surfaces of Organic Semiconductors.

    Science.gov (United States)

    Ryno, Sean M; Risko, Chad; Brédas, Jean-Luc

    2016-06-08

    The polarizable environment surrounding charge carriers in organic semiconductors impacts the efficiency of the charge transport process. Here, we consider two representative organic semiconductors, tetracene and rubrene, and evaluate their polarization energies in the bulk and at the organic-vacuum interface using a polarizable force field that accounts for induced-dipole and quadrupole interactions. Though both oligoacenes pack in a herringbone motif, the tetraphenyl substituents on the tetracene backbone of rubrene alter greatly the nature of the packing. The resulting change in relative orientations of neighboring molecules is found to reduce the bulk polarization energy of holes in rubrene by some 0.3 eV when compared to tetracene. The consideration of model organic-vacuum interfaces highlights the significant variation in the electrostatic environment for a charge carrier at a surface although the net change in polarization energy is small; interestingly, the environment of a charge even just one layer removed from the surface can be viewed already as representative of the bulk. Overall, it is found that in these herringbone-type layered crystals the polarization energy has a much stronger dependence on the intralayer packing density than interlayer packing density.

  11. Application of semiconductor photocatalysis for organic synthesis: from photons to the process

    NARCIS (Netherlands)

    Leite Pimenta Carneiro, J. T.

    2010-01-01

    In photocatalysis light drives the reactions. When a semiconductor, such as titania, is exposed to light of a specific wavelength range, several physical processes occur and chemical reactions can take place at its surface in the presence of a reactant. This technology works well for wastewater and

  12. Side-Chain Isomerization on an n-type Organic Semiconductor ITIC Acceptor Makes 11.77% High Efficiency Polymer Solar Cells.

    Science.gov (United States)

    Yang, Yankang; Zhang, Zhi-Guo; Bin, Haijun; Chen, Shanshan; Gao, Liang; Xue, Lingwei; Yang, Changduk; Li, Yongfang

    2016-11-16

    Low bandgap n-type organic semiconductor (n-OS) ITIC has attracted great attention for the application as an acceptor with medium bandgap p-type conjugated polymer as donor in nonfullerene polymer solar cells (PSCs) because of its attractive photovoltaic performance. Here we report a modification on the molecular structure of ITIC by side-chain isomerization with meta-alkyl-phenyl substitution, m-ITIC, to further improve its photovoltaic performance. In a comparison with its isomeric counterpart ITIC with para-alkyl-phenyl substitution, m-ITIC shows a higher film absorption coefficient, a larger crystalline coherence, and higher electron mobility. These inherent advantages of m-ITIC resulted in a higher power conversion efficiency (PCE) of 11.77% for the nonfullerene PSCs with m-ITIC as acceptor and a medium bandgap polymer J61 as donor, which is significantly improved over that (10.57%) of the corresponding devices with ITIC as acceptor. To the best of our knowledge, the PCE of 11.77% is one of the highest values reported in the literature to date for nonfullerene PSCs. More importantly, the m-ITIC-based device shows less thickness-dependent photovoltaic behavior than ITIC-based devices in the active-layer thickness range of 80-360 nm, which is beneficial for large area device fabrication. These results indicate that m-ITIC is a promising low bandgap n-OS for the application as an acceptor in PSCs, and the side-chain isomerization could be an easy and convenient way to further improve the photovoltaic performance of the donor and acceptor materials for high efficiency PSCs.

  13. P-type transparent conducting oxides

    Science.gov (United States)

    Zhang, Kelvin H. L.; Xi, Kai; Blamire, Mark G.; Egdell, Russell G.

    2016-09-01

    Transparent conducting oxides constitute a unique class of materials combining properties of electrical conductivity and optical transparency in a single material. They are needed for a wide range of applications including solar cells, flat panel displays, touch screens, light emitting diodes and transparent electronics. Most of the commercially available TCOs are n-type, such as Sn doped In2O3, Al doped ZnO, and F doped SnO2. However, the development of efficient p-type TCOs remains an outstanding challenge. This challenge is thought to be due to the localized nature of the O 2p derived valence band which leads to difficulty in introducing shallow acceptors and large hole effective masses. In 1997 Hosono and co-workers (1997 Nature 389 939) proposed the concept of ‘chemical modulation of the valence band’ to mitigate this problem using hybridization of O 2p orbitals with close-shell Cu 3d 10 orbitals. This work has sparked tremendous interest in designing p-TCO materials together with deep understanding the underlying materials physics. In this article, we will provide a comprehensive review on traditional and recently emergent p-TCOs, including Cu+-based delafossites, layered oxychalcogenides, nd 6 spinel oxides, Cr3+-based oxides (3d 3) and post-transition metal oxides with lone pair state (ns 2). We will focus our discussions on the basic materials physics of these materials in terms of electronic structures, doping and defect properties for p-type conductivity and optical properties. Device applications based on p-TCOs for transparent p-n junctions will also be briefly discussed.

  14. Density Functional Theory Simulations of Semiconductors for Photovoltaic Applications: Hybrid Organic-Inorganic Perovskites and III/V Heterostructures

    Directory of Open Access Journals (Sweden)

    Jacky Even

    2014-01-01

    Full Text Available Potentialities of density functional theory (DFT based methodologies are explored for photovoltaic materials through the modeling of the structural and optoelectronic properties of semiconductor hybrid organic-inorganic perovskites and GaAs/GaP heterostructures. They show how the properties of these bulk materials, as well as atomistic relaxations, interfaces, and electronic band-lineups in small heterostructures, can be thoroughly investigated. Some limitations of available standard DFT codes are discussed. Recent improvements able to treat many-body effects or based on density-functional perturbation theory are also reviewed in the context of issues relevant to photovoltaic technologies.

  15. Effect of Electron-Beam Irradiation on Organic Semiconductor and Its Application for Transistor-Based Dosimeters.

    Science.gov (United States)

    Kim, Jae Joon; Ha, Jun Mok; Lee, Hyeok Moo; Raza, Hamid Saeed; Park, Ji Won; Cho, Sung Oh

    2016-08-03

    The effects of electron-beam irradiation on the organic semiconductor rubrene and its application as a dosimeter was investigated. Through the measurements of photoluminescence and the ultraviolet photoelectron spectroscopy, we found that electron-beam irradiation induces n-doping of rubrene. Additionally, we fabricated rubrene thin-film transistors with pristine and irradiated rubrene, and discovered that the decrease in transistor properties originated from the irradiation of rubrene and that the threshold voltages are shifted to the opposite directions as the irradiated layers. Finally, a highly sensitive and air-stable electron dosimeter was fabricated based on a rubrene transistor.

  16. Exploring the electronic structure of an organic semiconductor based on a compactly fused electron donor-acceptor molecule.

    Science.gov (United States)

    Alemany, Pere; Canadell, Enric; Geng, Yan; Hauser, Jürg; Macchi, Piero; Krämer, Karl; Decurtins, Silvio; Liu, Shi-Xia

    2015-05-18

    A Mott-type semiconductor based on a compactly fused and partially oxidized electron donor-acceptor (D-A) molecule was recently prepared and identified to exhibit a large room-temperature conductivity of 2 S cm(-1) . In a marked contrast to the organic conductors characterized by relatively well decoupled and segregated uniform stacks of D and A moieties, the formally half-oxidized tetrathiafulvalene donors of the actual compound are organized in columnar π stacks only, whereby the coplanar electron-acceptor units, namely benzothiadiazole, are closely annulated along their ridges. Herein, we present a theoretical study that explores the electronic structure of this novel type of organic semiconductor. The highly symmetric-solid state material behaves as a one-dimensional electronic system with strong antiferromagnetic interactions (coupling constant>200 cm(-1) ). The unique shape and local dipole of this redox-active fused electron D-A molecule lays the basis for further investigations of the collective electronic structure, mainly in the function of different counterions embedded in the crystalline lattice. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. An Infrared Probe of Charge Dynamics in High Mobility Organic Semiconductors

    Science.gov (United States)

    2013-02-01

    specifically polythiophenes , have emerged as attractive materials for low-cost, large-area, and flexible electronics applications due to their solution...of magnitude increase in the DC electrical conductivity . The PI has carried out a thorough infrared and DC transport investigation of a prototypical...incorporate into the polythiophene structure, hydrolyze, and partially cross-link, forming a 3D network that induces a very strong p-type doping of P3HT

  18. Sensitization of p-type NiO using n-type conducting polymers

    NARCIS (Netherlands)

    Chavhan, S.D.; Abellon, R.D.; Breemen, A.J.J.M. van; Koetse, M.M.; Sweelssen, J.; Savenije, T.J.

    2010-01-01

    We report on the sensitization of a p-type inorganic semiconductor, NiO, by n-type conjugated polymers. NiO thin films were deposited using RF sputtering in pure Ar (NiO A) or in Ar + O2 (90% + 10%) (NiO B). XPS and Kelvin probe measurements indicate the incorporation of oxygen in NiO B

  19. Sensitization of p-type NiO using n-type conducting polymers

    NARCIS (Netherlands)

    Chavhan, S.D.; Abellon, R.D.; Breemen, A.J.J.M. van; Koetse, M.M.; Sweelssen, J.; Savenije, T.J.

    2010-01-01

    We report on the sensitization of a p-type inorganic semiconductor, NiO, by n-type conjugated polymers. NiO thin films were deposited using RF sputtering in pure Ar (NiO A) or in Ar + O2 (90% + 10%) (NiO B). XPS and Kelvin probe measurements indicate the incorporation of oxygen in NiO B l

  20. Sensitization of p-type NiO using n-type conducting polymers

    NARCIS (Netherlands)

    Chavhan, S.D.; Abellon, R.D.; Breemen, A.J.J.M. van; Koetse, M.M.; Sweelssen, J.; Savenije, T.J.

    2010-01-01

    We report on the sensitization of a p-type inorganic semiconductor, NiO, by n-type conjugated polymers. NiO thin films were deposited using RF sputtering in pure Ar (NiO A) or in Ar + O2 (90% + 10%) (NiO B). XPS and Kelvin probe measurements indicate the incorporation of oxygen in NiO B l

  1. New highly fluorescent biolabels based on II VI semiconductor hybrid organic inorganic nanostructures for bioimaging

    Science.gov (United States)

    Santos, B. S.; Farias, P. M. A.; Menezes, F. D.; Brasil, A. G., Jr.; Fontes, A.; Romão, L.; Amaral, J. O.; Moura-Neto, V.; Tenório, D. P. L. A.; Cesar, C. L.; Barbosa, L. C.; Ferreira, R.

    2008-11-01

    Semiconductor quantum dots based on II-VI materials may be prepared to develop good biolabeling properties. In this study we present some well-succeeded results related to the preparation, functionalization and bioconjugation of CdY (Y = S, Se and Te) to biological systems (live cells and fixed tissues). These nanostructured materials were prepared using colloidal synthesis in aqueous media resulting nanoparticles with very good optical properties and an excellent resistance to photodegradation.

  2. Application of semiconductor photocatalysis for organic synthesis: from photons to the process

    OpenAIRE

    Leite Pimenta Carneiro, J. T.

    2010-01-01

    In photocatalysis light drives the reactions. When a semiconductor, such as titania, is exposed to light of a specific wavelength range, several physical processes occur and chemical reactions can take place at its surface in the presence of a reactant. This technology works well for wastewater and air cleaning applications. In these, trace hazardous compounds present in water and air are converted (i.e. completely oxidized) to harmless ones such as carbon dioxide and water. A novel area wher...

  3. Role of band states and trap states in the charge transport properties of organic semiconductors (Conference Presentation)

    Science.gov (United States)

    Coropceanu, Veaceslav

    2016-11-01

    In this contribution, we examine the main factors that define charge transport in organic semiconductors. We consider both crystals based on a single molecule building block, such as oligoacenes, and two-component donor-acceptor crystals in which one component acts as an electron donor and the other as an acceptor. We will first discuss the state-of-the-art methodologies used in the derivation of the microscopic parameters (electron-vibration couplings, transfer integrals, band gaps, bandwidths, and effective masses) describing charge transport. In particular, we will discuss the impact that the amount of nonlocal Hartree-Fock exchange included in a hybrid density functional has on these parameters. In order to understand the role of disorder we use a combination of electronic-structure calculations and molecular mechanics/molecular dynamics simulations complemented by ensemble and time average approaches to separate the static and dynamic disorder components. The temperature dependence of the charge carrier mobility is studied by treating the electron-phonon interaction as a perturbation (Boltzmann theory), in the static approximation (Kubo formalism) and in the framework of mixed quantum/classical dynamics. Finally, based on the results of the kinetic Monte Carlo simulations we will compare the merits of a hopping model and a mobility edge model in the description of the effect of charge-carrier concentration on the electrical conductivity, carrier mobility, and Fermi energy of organic semiconductors.

  4. Organic semiconductor/gold interface interactions: from physisorption on planar surfaces to chemical reactions with metal nanoparticles.

    Science.gov (United States)

    Ligorio, Giovanni; Nardi, Marco Vittorio; Christodoulou, Christos; Koch, Norbert

    2015-08-24

    The interaction of gold nanoparticles (AuNPs) with prototypical organic semiconductors used in optoelectronics, namely, tris(8-hydroxyquinoline)aluminium (Alq3 ) and 4,4-bis[N-(1-naphthyl)-N-phenylamino]diphenyl (α-NPD), is investigated in situ by X-ray photoelectron spectroscopy (XPS). These AuNPs-on-molecule experiments are compared with the reversed molecule-on-Au cases. The molecules-on-Au systems show only weak interactions, and the evolution of the XP spectra is dominated by final-state effects. In contrast, in the AuNPs-on-molecules cases, both initial-state effects and final-state effects occur. Spectral features arising for both molecules and metal indicate charge transfer and the formation of organometallic complexes (initial-state effects). The energy shift in the metal emission underlines the size-induced nanometric nature of the molecule/Au interaction (final-state effects). Consequently, the chemical interaction between metals and organic semiconductors likely depends strongly on the deposition sequence in general.

  5. Facile synthesis of light harvesting semiconductor bismuth oxychloride nano photo-catalysts for efficient removal of hazardous organic pollutants.

    Science.gov (United States)

    Seddigi, Zaki S; Gondal, Mohammed A; Baig, Umair; Ahmed, Saleh A; Abdulaziz, M A; Danish, Ekram Y; Khaled, Mazen M; Lais, Abul

    2017-01-01

    In the present work, bismuth oxychloride nanoparticles-a light harvesting semiconductor photocatalyst-were synthesized by a facile hydrolysis route, with sodium bismuthate and hydroxylammonium chloride as the precursor materials. The as-synthesized semiconductor photocatalysts were characterized using X-ray diffraction analysis, Fourier transform infra-red spectroscopy, Raman spectroscopy, Field emission scanning electron microscopy, X-ray photoelectron spectroscopy and Photoluminescence spectroscopy techniques. The crystal structure, morphology, composition, and optical properties of these facile synthesized bismuth oxychloride nanoparticles (BiOCl NPs) were compared to those of traditional bismuth oxychloride. In addition, the photocatalytic performance of facile-synthesized BiOCl NPs and traditional BiOCl, as applied to the removal of hazardous organic dyes under visible light illumination, is thoroughly investigated. Our results reveal that facile-synthesized BiOCl NPs display strong UV-Vis light adsorption, improved charge carrier mobility and an inhibited rate of charge carrier recombination, when compared to traditional BiOCl. These enhancements result in an improved photocatalytic degradation rate of hazardous organic dyes under UV-Vis irradiance. For instance, the facile-synthesized BiOCl NPs attained 100% degradation of methylene blue and methyl orange dyes in approximately 30 mins under UV-Vis irradiation, against 55% degradation for traditional BiOCl under similar experimental conditions.

  6. Facile synthesis of light harvesting semiconductor bismuth oxychloride nano photo-catalysts for efficient removal of hazardous organic pollutants

    Science.gov (United States)

    Seddigi, Zaki S.; Baig, Umair; Ahmed, Saleh A.; Abdulaziz, M. A.; Danish, Ekram Y.; Khaled, Mazen M.; Lais, Abul

    2017-01-01

    In the present work, bismuth oxychloride nanoparticles–a light harvesting semiconductor photocatalyst–were synthesized by a facile hydrolysis route, with sodium bismuthate and hydroxylammonium chloride as the precursor materials. The as-synthesized semiconductor photocatalysts were characterized using X-ray diffraction analysis, Fourier transform infra-red spectroscopy, Raman spectroscopy, Field emission scanning electron microscopy, X-ray photoelectron spectroscopy and Photoluminescence spectroscopy techniques. The crystal structure, morphology, composition, and optical properties of these facile synthesized bismuth oxychloride nanoparticles (BiOCl NPs) were compared to those of traditional bismuth oxychloride. In addition, the photocatalytic performance of facile-synthesized BiOCl NPs and traditional BiOCl, as applied to the removal of hazardous organic dyes under visible light illumination, is thoroughly investigated. Our results reveal that facile-synthesized BiOCl NPs display strong UV-Vis light adsorption, improved charge carrier mobility and an inhibited rate of charge carrier recombination, when compared to traditional BiOCl. These enhancements result in an improved photocatalytic degradation rate of hazardous organic dyes under UV-Vis irradiance. For instance, the facile-synthesized BiOCl NPs attained 100% degradation of methylene blue and methyl orange dyes in approximately 30 mins under UV-Vis irradiation, against 55% degradation for traditional BiOCl under similar experimental conditions. PMID:28245225

  7. Tailored surface-enhanced Raman nanopillar arrays fabricated by laser-assisted replication for biomolecular detection using organic semiconductor lasers.

    Science.gov (United States)

    Liu, Xin; Lebedkin, Sergei; Besser, Heino; Pfleging, Wilhelm; Prinz, Stephan; Wissmann, Markus; Schwab, Patrick M; Nazarenko, Irina; Guttmann, Markus; Kappes, Manfred M; Lemmer, Uli

    2015-01-27

    Organic semiconductor distributed feedback (DFB) lasers are of interest as external or chip-integrated excitation sources in the visible spectral range for miniaturized Raman-on-chip biomolecular detection systems. However, the inherently limited excitation power of such lasers as well as oftentimes low analyte concentrations requires efficient Raman detection schemes. We present an approach using surface-enhanced Raman scattering (SERS) substrates, which has the potential to significantly improve the sensitivity of on-chip Raman detection systems. Instead of lithographically fabricated Au/Ag-coated periodic nanostructures on Si/SiO2 wafers, which can provide large SERS enhancements but are expensive and time-consuming to fabricate, we use low-cost and large-area SERS substrates made via laser-assisted nanoreplication. These substrates comprise gold-coated cyclic olefin copolymer (COC) nanopillar arrays, which show an estimated SERS enhancement factor of up to ∼ 10(7). The effect of the nanopillar diameter (60-260 nm) and interpillar spacing (10-190 nm) on the local electromagnetic field enhancement is studied by finite-difference-time-domain (FDTD) modeling. The favorable SERS detection capability of this setup is verified by using rhodamine 6G and adenosine as analytes and an organic semiconductor DFB laser with an emission wavelength of 631.4 nm as the external fiber-coupled excitation source.

  8. A metrology perspective on the dark injection transient current method for charge mobility determination in organic semiconductors

    Science.gov (United States)

    Esward, T.; Knox, S.; Jones, H.; Brewer, P.; Murphy, C.; Wright, L.; Williams, J.

    2011-05-01

    Charge mobility is a key parameter for understanding the performance of organic semiconductor devices and materials. A range of techniques is available that can measure charge mobility with varying accuracy and precision. In this paper we analyze the dark injection transient current (DITC) method from a metrology perspective. We carried out a systematic study of the sensitivity of single carrier analogues of organic light-emitting diodes (OLEDs) to small changes in electrical input and environmental conditions. We observed that the experimental results depend strongly on the previous history of the device under test, with both long term and short term effects in evidence. Our findings demonstrate the need for caution in interpreting the results of single experiments to determine the charge mobility of OLEDs and the difficulty of associating uncertainty statements with the results of charge mobility measurements.

  9. Fluorosurfactant-assisted photolithography for patterning of perfluoropolymers and solution-processed organic semiconductors for printed displays

    Science.gov (United States)

    Sakanoue, Tomo; Mizukami, Makoto; Oku, Shinya; Yoshimura, Yudai; Abiko, Miho; Tokito, Shizuo

    2014-10-01

    A photolithographic patterning technique of perfluoropolymers was developed for the micropatterning of solution-processed organic semiconductors. We found that a small amount of fluorosurfactant additives in photoresist solutions enabled preparation of the spin-coated films even on the dewetting surfaces of perfluoropolymers. Subsequent photolithography and dry/wet etching achieved excellent patterning of perfluoropolymers, which provided a high contrast of wettability in microscale on the substrate. The dewetting patterns were applied for isolating solution-processed organic thin-film transistor arrays for a 100 ppi active-matrix display by selective dewetting. The isolation of the semiconducting layers achieved significant improvement in the current on/off ratio with a high mobility of >1 cm2 V-1 s-1.

  10. Exposure to Volatile Organic Compounds and Possibility of Exposure to By-product Volatile Organic Compounds in Photolithography Processes in Semiconductor Manufacturing Factories.

    Science.gov (United States)

    Park, Seung-Hyun; Shin, Jung-Ah; Park, Hyun-Hee; Yi, Gwang Yong; Chung, Kwang-Jae; Park, Hae-Dong; Kim, Kab-Bae; Lee, In-Seop

    2011-09-01

    The purpose of this study was to measure the concentration of volatile organic compound (VOC)s originated from the chemicals used and/or derived from the original parental chemicals in the photolithography processes of semiconductor manufacturing factories. A total of four photolithography processes in 4 Fabs at three different semiconductor manufacturing factories in Korea were selected for this study. This study investigated the types of chemicals used and generated during the photolithography process of each Fab, and the concentration levels of VOCs for each Fab. A variety of organic compounds such as ketone, alcohol, and acetate compounds as well as aromatic compounds were used as solvents and developing agents in the processes. Also, the generation of by-products, such as toluene and phenol, was identified through a thermal decomposition experiment performed on a photoresist. The VOC concentration levels in the processes were lower than 5% of the threshold limit value (TLV)s. However, the air contaminated with chemical substances generated during the processes was re-circulated through the ventilation system, thereby affecting the airborne VOC concentrations in the photolithography processes. Tens of organic compounds were being used in the photolithography processes, though the types of chemical used varied with the factory. Also, by-products, such as aromatic compounds, could be generated during photoresist patterning by exposure to light. Although the airborne VOC concentrations resulting from the processes were lower than 5% of the TLVs, employees still could be exposed directly or indirectly to various types of VOCs.

  11. Resonance energy transfer in conjugates of semiconductor nanocrystals and organic dye molecules

    Science.gov (United States)

    Artemyev, Mikhail

    2012-01-01

    I analyze the efficiency of Förster resonance energy transfer (FRET) in luminescent donor-acceptor complexes based on conjugates of CdSe/ZnS quantum dots and nanorods and the luminescent dyes. Semiconductor nanocrystals serve either as FRET donors or acceptors. Experimentally observed reduced FRET efficiency in complexes of nanorods and dye molecules as compared to quantum dots are found to be attributable to a distance-limited energy transfer rate in case of point-like dye dipoles and extended nanorod dipole.

  12. Late stage crystallization and healing during spin-coating enhance carrier transport in small-molecule organic semiconductors

    KAUST Repository

    Chou, Kang Wei

    2014-01-01

    Spin-coating is currently the most widely used solution processing method in organic electronics. Here, we report, for the first time, a direct investigation of the formation process of the small-molecule organic semiconductor (OSC) 6,13-bis(triisopropylsilylethynyl) (TIPS)-pentacene during spin-coating in the context of an organic thin film transistor (OTFT) application. The solution thinning and thin film formation were monitored in situ by optical reflectometry and grazing incidence wide angle X-ray scattering, respectively, both of which were performed during spin-coating. We find that OSC thin film formation is akin to a quenching process, marked by a deposition rate of ∼100 nm s-1, nearly three orders of magnitude faster than drop-casting. This is then followed by a more gradual crystallization and healing step which depends upon the spinning speed. We associate this to further crystallization and healing of defects by residency of the residual solvent trapped inside the kinetically trapped film. The residency time of the trapped solvent is extended to several seconds by slowing the rotational speed of the substrate and is credited with improving the carrier mobility by nearly two orders of magnitude. Based on this insight, we deliberately slow down the solvent evaporation further and increase the carrier mobility by an additional order of magnitude. These results demonstrate how spin-coating conditions can be used as a handle over the crystallinity of organic semiconductors otherwise quenched during initial formation only to recrystallize and heal during extended interaction with the trapped solvent. This journal is © the Partner Organisations 2014.

  13. Investigations on Substrate Temperature-Induced Growth Modes of Organic Semiconductors at Dielectric/semiconductor Interface and Their Correlation with Threshold Voltage Stability in Organic Field-Effect Transistors.

    Science.gov (United States)

    Padma, Narayanan; Maheshwari, Priya; Bhattacharya, Debarati; Tokas, Raj B; Sen, Shashwati; Honda, Yoshihide; Basu, Saibal; Pujari, Pradeep Kumar; Rao, T V Chandrasekhar

    2016-02-10

    Influence of substrate temperature on growth modes of copper phthalocyanine (CuPc) thin films at the dielectric/semiconductor interface in organic field effect transistors (OFETs) is investigated. Atomic force microscopy (AFM) imaging at the interface reveals a change from 'layer+island' to "island" growth mode with increasing substrate temperatures, further confirmed by probing the buried interfaces using X-ray reflectivity (XRR) and positron annihilation spectroscopic (PAS) techniques. PAS depth profiling provides insight into the details of molecular ordering while positron lifetime measurements reveal the difference in packing modes of CuPc molecules at the interface. XRR measurements show systematic increase in interface width and electron density correlating well with the change from layer + island to coalesced huge 3D islands at higher substrate temperatures. Study demonstrates the usefulness of XRR and PAS techniques to study growth modes at buried interfaces and reveals the influence of growth modes of semiconductor at the interface on hole and electron trap concentrations individually, thereby affecting hysteresis and threshold voltage stability. Minimum hole trapping is correlated to near layer by layer formation close to the interface at 100 °C and maximum to the island formation with large voids between the grains at 225 °C.

  14. p-Type NiO Hybrid Visible Photodetector.

    Science.gov (United States)

    Mallows, John; Planells, Miquel; Thakare, Vishal; Bhosale, Reshma; Ogale, Satishchandra; Robertson, Neil

    2015-12-23

    A novel hybrid visible-light photodetector was created using a planar p-type inorganic NiO layer in a junction with an organic electron acceptor layer. The effect of different oxygen pressures on formation of the NiO layer by pulsed laser deposition shows that higher pressure increases the charge carrier density of the film and lowers the dark current in the device. The addition of a monolayer of small molecules containing conjugated π systems and carboxyl groups at the device interface was also investigated and with correct alignment of the energy levels improves the device performance with respect to the quantum efficiency, responsivity, and photogeneration. The thickness of the organic layer was also optimized for the device, giving a responsivity of 1.54 × 10(-2) A W(-1) in 460 nm light.

  15. The effects of electric and magnetic fields on the current spin polarization and magnetoresistance in a ferromagnetic/organic semiconductor/ferromagnetic (FM/OSC/FM) system

    Institute of Scientific and Technical Information of China (English)

    Wang Yu-Mei; Ren Jun-Feng; Yuan Xiao-Bo; Dou Zhao-Tao; Hu Gui-Chao

    2012-01-01

    From experimental results of spin polarized injection and transport in organic semiconductors (OSCs),we theoretically study the current spin polarization and magnetoresistance under an electric and a magnetic field in a ferromagnetic/organic semiconductor/ferromagnetic (FM/OSC/FM) sandwich structure according to the spin drift-diffusion theory and Ohm's law.From the calculations,it is found that the interfacial current spin polarization is enhanced by several orders of magnitude through tuning the magnetic and electric fields by taking into account the specific characteristics of OSC.Furthermore,the effects of the electric and magnetic fields on the magnetoresistance are also discussed in the sandwich structure.

  16. Study of Fused Thiophene Based Organic Semiconductors and Interfacial Self-Assembled Monolayer (SAM) for Thin-Film Transistor (TFT) Application

    Science.gov (United States)

    Youn, Jangdae

    In this thesis, the molecular packing motifs of our newly designed fused thiophenes, benzo[d,d]thieno[3,2-b;4,5-b]dithiophene (BTDT) derivatives, were studied by utilizing grazing incidence wide angle X-ray scattering (GIWAXS). Considering the potential of fused thiophene molecules as an environmentally stable, high performance semiconductor building block, it must be an important groundwork to investigate their thin film structures in relation to molecular structures, single crystal structures, and organic thin-film transistors (OTFT) performances. OTFT device performance is not only determined by semiconductor materials, but also influenced by the interfacial properties. Since there are three major components in TFT structures---electrodes, semiconductors, and dielectrics, two types of major interfaces exist. One is the semiconductor-electrode interface, and the other is the semiconductor-dielectric interface. Both of these interfaces have critical roles for TFT operation. For example, the semiconductor-electrode interface determines the charge injection barrier. Before charge carriers go through the electrode (source)-semiconductor-electrode (drain) pathways, the energy gaps between the work function of the electrodes and the HOMO energy of the semiconductor materials must be overcome for hole injection, or the energy gap between the metal work function of the electrodes and the LUMO energy of the semiconductor materials must be overcome for electron injection. These charge injection barriers are largely determined by the energetic structure of the semiconductor material and work function of the electrode. However, the size of energy gap can be modified by introducing an organic self-assembled monolayer (SAM) on the surface of metal electrode. In addition, the structure of semiconductor films, especially within several monolayers right above the electrode, is greatly influenced by the SAM, and it changes charge injection property of OTFT devices. In this thesis

  17. Spontaneously formed high-performance charge-transport layers of organic single-crystal semiconductors on precisely synthesized insulating polymers

    Science.gov (United States)

    Makita, Tatsuyuki; Sasaki, Masayuki; Annaka, Tatsuro; Sasaki, Mari; Matsui, Hiroyuki; Mitsui, Chikahiko; Kumagai, Shohei; Watanabe, Shun; Hayakawa, Teruaki; Okamoto, Toshihiro; Takeya, Jun

    2017-04-01

    Charge-transporting semiconductor layers with high carrier mobility and low trap-density, desired for high-performance organic transistors, are spontaneously formed as a result of thermodynamic phase separation from a blend of π-conjugated small molecules and precisely synthesized insulating polymers dissolved in an aromatic solvent. A crystal film grows continuously to the size of centimeters, with the critical conditions of temperature, concentrations, and atmosphere. It turns out that the molecular weight of the insulating polymers plays an essential role in stable film growth and interfacial homogeneity at the phase separation boundary. Fabricating the transistor devices directly at the semiconductor-insulator boundaries, we demonstrate that the mixture of 3,11-didecyldinaphtho[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene and poly(methyl methacrylate) with the optimized weight-average molecular weight shows excellent device performances. The spontaneous phase separation with a one-step fabrication process leads to a high mobility up to 10 cm2 V-1 s-1 and a low subthreshold swing of 0.25 V dec-1 even without any surface treatment such as self-assembled monolayer modifications on oxide gate insulators.

  18. Crafting semiconductor organic-inorganic nanocomposites via placing conjugated polymers in intimate contact with nanocrystals for hybrid solar cells.

    Science.gov (United States)

    Zhao, Lei; Lin, Zhiqun

    2012-08-22

    Semiconductor organic-inorganic hybrid solar cells incorporating conjugated polymers (CPs) and nanocrystals (NCs) offer the potential to deliver efficient energy conversion with low-cost fabrication. The CP-based photovoltaic devices are complimented by an extensive set of advantageous characteristics from CPs and NCs, such as lightweight, flexibility, and solution-processability of CPs, combined with high electron mobility and size-dependent optical properties of NCs. Recent research has witnessed rapid advances in an emerging field of directly tethering CPs on the NC surface to yield an intimately contacted CP-NC nanocomposite possessing a well-defined interface that markedly promotes the dispersion of NCs within the CP matrix, facilitates the photoinduced charge transfer between these two semiconductor components, and provides an effective platform for studying the interfacial charge separation and transport. In this Review, we aim to highlight the recent developments in CP-NC nanocomposite materials, critically examine the viable preparative strategies geared to craft intimate CP-NC nanocomposites and their photovoltaic performance in hybrid solar cells, and finally provide an outlook for future directions of this extraordinarily rich field. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. CuNb3O8: A p-Type Semiconducting Metal Oxide Photoelectrode.

    Science.gov (United States)

    Joshi, Upendra A; Maggard, Paul A

    2012-06-07

    A new p-type CuNb3O8 polycrystalline photoelectrode was investigated and was determined to have indirect and direct bandgap sizes of 1.26 and 1.47 eV, respectively. The p-type polycrystalline film could be prepared on fluorine-doped tin oxide glass and yielded a cathodic photocurrent under visible-light irradiation (λ > 420 nm) with incident photon-to-current efficiencies of up to ∼6-7% and concomitant hydrogen evolution. A Mott-Schottky analysis yielded a flat band potential of +0.35 V versus RHE (pH = 6.3) and a calculated p-type dopant concentration of ∼7.2 × 10(15) cm(-3). The conduction band energies are found to be negative enough for the reduction of water under visible light irradiation. A hole mobility of ∼145 cm(2)/V·s was obtained from J(I)-V(2) measurements using the Mott-Gurney relation, which is ∼50% higher than that typically found for p-type Cu2O. DFT-based electronic structure calculations were used to probe the atomic and structural origins of the band gap transitions and carrier mobility. Thus, a new p-type semiconductor is discovered for potential applications in solar energy conversion.

  20. Laser excitation induced modifications on distributed feedback microcavities using organic semiconductors

    Science.gov (United States)

    Wang, Tingting; Zhang, Xinping

    2017-06-01

    Distributed feedback (DFB) lasers can be achieved by spin-coating semiconductor polymers onto the top surface of a photoresist grating with designed periods. Optical pumping using lasers within the absorption spectrum of the polymer induced strong modification on the morphological distribution of the polymer film and consequently on the spectroscopic response of the DFB microcavities. The corresponding modification processes resulted mainly from the pump-laser-induced cross-linking of the polymer molecules, which led to the reduction in both the thickness and refractive index of the polymer layer. The location of the polymer laser was lowered from the top to the bottom surface of the DFB grating. Concise modeling on the angle-resolved tuning properties of the output spectrum of the DFB microcavity was achieved with excellent agreement with the experimental observation, which provided clear physical insights into the operation mechanisms of a DFB microcavity.

  1. Compact ultrafast semiconductor disk laser for nonlinear imaging in living organisms

    Science.gov (United States)

    Aviles-Espinosa, Rodrigo; Filippidis, G.; Hamilton, Craig; Malcolm, Graeme; Weingarten, Kurt J.; Südmeyer, Thomas; Barbarin, Yohan; Keller, Ursula; Artigas, David; Loza-Alvarez, Pablo

    2011-03-01

    Ultrashort pulsed laser systems (such as Ti:sapphire) have been used in nonlinear microscopy during the last years. However, its implementation is not straight forward as they are maintenance-intensive, bulky and expensive. These limitations have prevented their wide-spread use for nonlinear imaging, especially in "real-life" biomedical applications. In this work we present the suitability of a compact ultrafast semiconductor disk laser source, with a footprint of 140x240x70 mm, to be used for nonlinear microscopy. The modelocking mechanism of the laser is based on a quantumdot semiconductor saturable absorber mirror (SESAM). The laser delivers an average output power of 287 mW with 1.5 ps pulses at 500 MHz, corresponding to a peak power of 0.4 kW. Its center wavelength is 965 nm which is ideally suited for two-photon excitation of the widely used Green Fluorescent Protein (GFP) marker as it virtually matches its twophoton action cross section. We reveal that it is possible to obtain two photon excited fluorescence images of GFP labeled neurons and secondharmonic generation images of pharynx and body wall muscles in living C. elegans nematodes. Our results demonstrate that this compact laser is well suited for long-term time-lapse imaging of living samples as very low powers provide a bright signal. Importantly this non expensive, turn-key, compact laser system could be used as a platform to develop portable nonlinear bio-imaging devices, facilitating its wide-spread adoption in "real-life" applications.

  2. Charge depletion in organic heterojunction

    Science.gov (United States)

    Ng, T. W.; Lo, M. F.; Lee, S. T.; Lee, C. S.

    2012-03-01

    Until now two types of organic-organic heterojunction (OHJ) have been observed in P-N junctions formed between undoped-organic semiconductors. Charge-transfers across OHJs are either negligible or showing electron transfer from P-type to N-type materials, leading to charges accumulation near the interface. Here, we observed that junction of 4,4',4''-tris(2-methylphenyl-phenylamino)triphenylamine (m-MTDATA)/bathocuproine (BCP) show the third-behavior. Electrons in BCP (N-type) transfer to m-MTDATA (P-type), leading to depletion of mobile majority carriers near the junction. While "depletion junctions" are typical in inorganic semiconductors, there are no reports in undoped-OHJ. Formation mechanism of depletion OHJs and fundamental differences between inorganic and organic HJs are discussed.

  3. Ferromagnetic ordering of Cr and Fe doped p-type diamond: An ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Benecha, E. M. [Department of Physics, University of South Africa, P.O Box 392, UNISA 0003, Pretoria (South Africa); Lombardi, E. B. [College of Graduate Studies, University of South Africa, P.O Box 392, UNISA 0003, Pretoria (South Africa)

    2014-02-21

    Ferromagnetic ordering of transition metal dopants in semiconductors holds the prospect of combining the capabilities of semiconductors and magnetic systems in single hybrid devices for spintronic applications. Various semiconductors have so far been considered for spintronic applications, but low Curie temperatures have hindered room temperature applications. We report ab initio DFT calculations on the stability and magnetic properties of Fe and Cr impurities in diamond, and show that their ground state magnetic ordering and stabilization energies depend strongly on the charge state and type of co-doping. We predict that divacancy Cr{sup +2} and substitutional Fe{sup +1} order ferromagnetically in p-type diamond, with magnetic stabilization energies (and magnetic moment per impurity ion) of 16.9 meV (2.5 μ{sub B}) and 33.3 meV (1.0 μ{sub B}), respectively. These magnetic stabilization energies are much larger than what has been achieved in other semiconductors at comparable impurity concentrations, including the archetypal dilute magnetic semiconductor GaAs:Mn. In addition, substitutional Fe{sup +1} exhibits a strong half-metallic character, with the Fermi level crossing bands in only the spin down channel. These results, combined with diamond’s extreme properties, demonstrate that Cr or Fe dopedp-type diamond may successfully be considered in the search for room temperature spintronic materials.

  4. Self-consistent theory for the built-in voltage in metal-organic semiconductor-metal structures

    Energy Technology Data Exchange (ETDEWEB)

    Peng Yingquan, E-mail: yqpeng@lzu.edu.cn [Laboratory of Semiconductor Devices and Engineering, Lanzhou University, Tian-Shui Road, Lanzhou 730000 (China); Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Meng Weimin [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Wang Runsheng; Ma Chaozhu; Li Xunshuan; Xie Hongwei; Li Ronghua; Zhao Ming; Yuan Jianting; Wang Ying [Laboratory of Semiconductor Devices and Engineering, Lanzhou University, Tian-Shui Road, Lanzhou 730000 (China)

    2009-06-30

    A self-consistent theory for calculation of built-in voltage (U{sub bi}) of metal-organic semiconductor-metal (MOSM) structures is developed based on Gaussian energy distribution of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). It is shown that the built-in voltage depends not only on the work function difference of the two electrodes, but also on the mean energy level of HOMO and LUMO, as well as the Gaussian width of the energy distribution. The theory predicts that the spreading of HOMO and LUMO levels will results in an increase of U{sub bi}, and that U{sub bi} decreases with increasing temperature.

  5. Optical conductivity and optical effective mass in a high-mobility organic semiconductor: Implications for the nature of charge transport

    KAUST Repository

    Li, Yuan

    2014-12-03

    We present a multiscale modeling of the infrared optical properties of the rubrene crystal. The results are in very good agreement with the experimental data that point to nonmonotonic features in the optical conductivity spectrum and small optical effective masses. We find that, in the static-disorder approximation, the nonlocal electron-phonon interactions stemming from low-frequency lattice vibrations can decrease the optical effective masses and lead to lighter quasiparticles. On the other hand, the charge-transport and infrared optical properties of the rubrene crystal at room temperature are demonstrated to be governed by localized carriers driven by inherent thermal disorders. Our findings underline that the presence of apparently light carriers in high-mobility organic semiconductors does not necessarily imply bandlike transport.

  6. Role of band states and trap states in the electrical properties of organic semiconductors: Hopping versus mobility edge model

    KAUST Repository

    Mehraeen, Shafigh

    2013-05-01

    We compare the merits of a hopping model and a mobility edge model in the description of the effect of charge-carrier concentration on the electrical conductivity, carrier mobility, and Fermi energy of organic semiconductors. We consider the case of a composite electronic density of states (DOS) that consists of a superposition of a Gaussian DOS and an exponential DOS. Using kinetic Monte Carlo simulations, we apply the two models in order to interpret the recent experimental data reported for n-doped C60 films. While both models are capable of reproducing the experimental data very well and yield qualitatively similar characteristic parameters for the density of states, some discrepancies are found at the quantitative level. © 2013 American Physical Society.

  7. Nanostructured pyronin Y thin films as a new organic semiconductor: Linear/nonlinear optics, band gap and dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Zahran, H.Y. [Metallurgical Lab.1, Nanoscience Laboratory for Environmental and Bio-medical Applications (NLEBA), Semiconductor Lab., Department of Physics, Faculty of Education, Ain Shams University, Roxy, 11757 Cairo (Egypt); Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Yahia, I.S., E-mail: dr_isyahia@yahoo.com [Metallurgical Lab.1, Nanoscience Laboratory for Environmental and Bio-medical Applications (NLEBA), Semiconductor Lab., Department of Physics, Faculty of Education, Ain Shams University, Roxy, 11757 Cairo (Egypt); Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Alamri, F.H. [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia)

    2017-05-15

    Pyronin Y dye (PY) is a kind of xanthene derivatives. Thin films of pyronin Y were deposited onto highly cleaned glass substrates using low-cost/spin coating technique. The structure properties of pyronin Y thin films with different thicknesses were investigated by using X-ray diffraction (XRD) and atomic force microscope (AFM). PY thin films for all the studied thicknesses have an amorphous structure supporting the short range order of the grain size. AFM supports the nanostructure with spherical/clusters morphologies of the investigated thin films. The optical constants of pyronin Y thin films for various thicknesses were studied by using UV–vis–NIR spectrophotometer in the wavelength range 350–2500 nm. The transmittance T(λ), reflectance R(λ) spectral and absorbance (abs(λ)) were obtained for all film thicknesses at room temperature and the normal light incident. These films showed a high transmittance in the wide scale wavelengths. For different thicknesses of the studied thin films, the optical band gaps were determined and their values around 2 eV. Real and imaginary dielectric constants, dissipation factor and the nonlinear optical parameters were calculated in the wavelengths to the range 300–2500 nm. The pyronin Y is a new organic semiconductor with a good optical absorption in UV–vis regions and it is suitable for nonlinear optical applications. - Highlights: • Pyronin Y (PY) nanostructured thin films were deposited by using spin coating technique. • XRD/AFM were used to study the structure of PY films. • The optical band gap was calculated on the basis of Tauc's model. • Linear/nonlinear optical parameters are calculated and interpreted via the applied optical theories. • PY thin films is a new organic semiconductor for its application in optoelectronic devices.

  8. EDITORIAL: Oxide semiconductors

    Science.gov (United States)

    Kawasaki, M.; Makino, T.

    2005-04-01

    Blue or ultraviolet semiconducting light-emitting diodes have the potential to revolutionize illumination systems in the near-future. Such industrial need has propelled the investigation of several wide-gap semiconducting materials in recent years. Commercial applications include blue lasers for DVD memory and laser printers, while military applications are also expected. Most of the material development has so far been focused on GaN (band gap 3.5 eV at 2 K), and ZnSe (2.9 eV) because these two representative direct transition semiconductors are known to be bright emitting sources. GaN and GaN-based alloys are emerging as the winners in this field because ZnSe is subject to defect formation under high current drive. On the other hand, another II-VI compound, ZnO, has also excited substantial interest in the optoelectronics-oriented research communities because it is the brightest emitter of all, owing to the fact that its excitons have a 60 meV binding energy. This is compared with 26 meV for GaN and 20 meV for ZnSe. The stable excitons could lead to laser action based on their recombination even at temperatures well above room temperature. ZnO has additional major properties that are more advantageous than other wide-gap materials: availability of large area substrates, higher energy radiation stability, environmentally-friendly ingredients, and amenability to wet chemical etching. However, ZnO is not new to the semiconductor field as exemplified by several studies made during the 1960s on structural, vibrational, optical and electrical properties (Mollwo E 1982 Landolt-Boernstein New Series vol 17 (Berlin: Springer) p 35). In terms of devices, the luminescence from light-emitting diode structures was demonstrated in which Cu2O was used as the p-type material (Drapak I T 1968 Semiconductors 2 624). The main obstacle to the development of ZnO has been the lack of reproducible p-type ZnO. The possibility of achieving epitaxial p-type layers with the aid of thermal

  9. Optical, Electrical and Magnetic Studies of Pi-Conjugated Organic Semiconductor Systems

    Energy Technology Data Exchange (ETDEWEB)

    Vardeny, Zeev Valentine [Univ. of Utah, Salt Lake City, UT (United States)

    2016-09-15

    Over the duration of this grant our group has studied the transient and cw optical response of various π-conjugated polymers, oligomers, single crystals, fullerene molecules and blends of organic donor-acceptor molecules. We have been also involved in complementary experiments such as magneto-optical studies and spin-physics. We have advanced the field of photophysics of these materials by providing information on their excited state energies and primodal and long-lived photoexcitations such as singlet excitons, triplet excitons, polaron-pairs, excimers and exciplexes. We also fabricated various organic optoelectronic devices such as organic light emitting diodes (OLED), electrochemical cells, organic diodes, organic spin-valves (OSV), and organic photovoltaic (OPV) solar cells. These devices benefited the society in terms of cheap and energy saving illumination, as well as harnessing the solar energy.

  10. Frequency dependent capacitance and conductance properties of Schottky diode based on rubrene organic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Barış, Behzad, E-mail: behzadbaris@gmail.com

    2013-10-01

    Al/rubrene/p-Si Schottky diode has been fabricated by forming a rubrene layer on p type Si by using the spin coating method. The frequency dependent capacitance–voltage (C–V–f) and conductance–voltage (G–V–f) characteristics of Al/rubrene/p-Si Schottky diyotes has been investigated in the frequency range of 5 kHz–500 kHz at room temperature. The C–V plots show a peak for each frequency. The capacitance of the device decreased with increasing frequency. The decrease in capacitance results from the presence of interface states. The plots of series resistance–voltage (R{sub s}−V) gave a peak in the depletion region at all frequencies. The density of interface states (N{sub ss}) and relaxation time (τ) distribution profiles as a function of applied voltage bias have been determined from the C–V and G–V measurements. The values of the N{sub ss} and τ have been calculated in the ranges of 8.37×10{sup 11}–4.85×10{sup 11} eV{sup −1} cm{sup −2} and 5.17×10{sup −6}–1.02×10{sup −5} s, respectively.

  11. Photoelectrochemical studies on colloidal copper (I) oxide/modified with some organic semiconductors: Incentive for use of nanoparticle systems

    Indian Academy of Sciences (India)

    Kasem K Kasem; Carmen Davis

    2008-12-01

    Colloidal Cu2O solutions were used to explore photonic activities at the semiconductor/electrolyte interface. Fluorescence spectroscopic studies were performed on Cu2O colloidal particles modified with some conjugated organic monomers such as 2-amino-phenyl pyrrole (2-APPy), tri-phenyl amine (TPA), or 2-thionyl pyrrole (2-Th-Py) to investigate the quantum absorbance efficiency at this inorganic/organic interface (IOI). Our study shows that colloidal -type Cu2O possesses a bandgap with direct transition of ≈ 2.2 eV and indirect transition of 1.85 eV. The recorded rates of charge injection into colloidal Cu2O, ct, were 2.31 × 109 s-1, 5.05 × 108 s-1, and 7.22 × 108 s-1 for 2-APPy, TPA and 2-Th-Py, respectively. The studied systems show more stability in colloidal form than in thin solid form. Results were interpreted using the optical and electrical parameters of the organic monomer such as ionization potential (IP), electron affinity (EA) and energy bandgap (Eg), and the barrier height at the IOI interface. Stability of the colloidal system is attributed to the physical dimensions of the photoactive system. The nano-colloidal particle offers a condition where its size is less than √.

  12. Electronic Properties of Optically Switchable Photochromic Diarylethene Molecules at the Interface with Organic Semiconductors.

    Science.gov (United States)

    Wang, Qiankun; Frisch, Johannes; Herder, Martin; Hecht, Stefan; Koch, Norbert

    2017-04-05

    Light-switching-induced changes in the electronic properties of photochromic diarylethene, i.e., 1,2-bis(2-methyl-5-p-tolylthiophen-3-yl)cyclopent-1-ene (DAE1), thin films at interfaces to a gold electrode and two polymer semiconductors are investigated by direct and inverse photoelectron spectroscopy. The photoisomerization is achieved by in situ irradiation of ultraviolet and visible light. Efficient and reversible switching between the open and closed isomers of DAE1 is evidenced at all interfaces, with profound impact on the energy-level alignment. The frontier occupied level of DAE1 changes by 0.8 eV with respect to the Au Fermi level upon switching. Corresponding sizable changes in the electron and transport level offsets between the two polymers and DAE1 in its open and closed form are determined. This gives rise to fundamentally different functionality of these interfaces in terms of charge transport. Our study proves the viability of light-controlled energy-level manipulation at various interfaces in photoswitchable opto-electronic devices.

  13. Exchange Mechanisms in Long Range Ordered Thin Film Organic Magnetic Semiconductors

    Science.gov (United States)

    Rawat, N.; Headrick, R.; Furis, M.; McGill, S.; Kilanski, L.; Waterman, R.

    2014-03-01

    Magnetic exchange mechanisms in crystalline thin films of Metal Phthalocyanines (M-Pc) are explored using Magnetic Circular Dichroism (MCD) and SQUID measurements up to 10 T and 2K. Long range ordered thin films of organo-soluble derivatives of Co-Pc and Mn-Pc were fabricated using solution processing technique. In the case of Mn-Pc, our measurements show enhanced hybridization of ligand π-electronic states with the Mn d-orbitals. MCD active states beyond 1 μm have been observed for the first time, providing crucial information on the orbital arrangements of MPc's that result in competing (co-existing) long-range superexchange and indirect exchange reminiscent of RKKY. The evolution of Zeeman splitting of specific MCD-active states is very well described by enhanced effective π-electrons g-factors as large as 100, analogous to diluted magnetic semiconductors (DMS) systems. In Co-Pc MCD data indicates a weaker exchange interaction between delocalized charge carriers and d-like spin-polarized electrons, however SQUID measurements reveal magnetic ordering up to 180K. A comparison between Mn-Pc and Co-Pc and earlier results from the spin 1/2 Cu-Pc and their non-magnetic Zn-Pc counterpart, offers an interesting view on the role of long range order in magnetic interactions. NSF, MRI and CAREER programs: DMR- 0722451; DMR-0348354; DMR- 0821268; DMR-1056589.

  14. Organic semiconductor wastewater treatment using a four-stage Bardenpho with membrane system.

    Science.gov (United States)

    Chung, Jinwook; Fleege, Daniel; Ong, Say Kee; Lee, Yong-Woo

    2014-01-01

    Electronic wastewater from a semiconductor plant was treated with a pilot-scale four-stage Bardenpho process with membrane system. The system was operated over a 14-month period with an overall hydraulic retention time (HRT) ranging from 9.5 to 30 h. With a few exceptions, the pilot plant consistently treated the electronic wastewater with an average removal efficiency of chemical oxygen demand (COD) and total nitrogen of 97% and 93%, respectively, and achieving effluent quality of COD<15 mg/L, turbidity<1, and silt density index<1. Based on removal efficiencies of the pilot plant, it is possible to lower the HRT to less than 9.5 h to achieve comparable removal efficiencies. An energy-saving configuration where an internal recycle line was omitted and the biomass recycle was rerouted to the pre-anoxic tank, can reduce energy consumption by 8.6% and gave removal efficiencies that were similar to the Bardenpho process. The system achieved pre-anoxic and post-anoxic specific denitrification rate values with a 95% confidence interval of 0.091 ± 0.011 g NO₃-N/g MLVSS d and 0.087 ± 0.016 g NO₃-N/g MLVSS d, respectively. The effluent from the four-stage Bardenpho with membrane system can be paired with a reverse osmosis system to provide further treatment for reuse purposes.

  15. Organic/IR-Semiconductor heterojunctions for low-cost, high temperature IR arrays

    Science.gov (United States)

    Jones, Colin E.

    1992-08-01

    This program evaluated a new technology for producing infrared photo-diodes in HgCdTe and InSb using evaporated organic heterojunctions. High quantum-efficiency IR detectors were demonstrated with the organic process comparable to commercial IR detectors. The organic photodiodes at room temperature were better than commercial detectors. They had lower leakage currents and higher resistance-area products (RoAs). Detector arrays made with the organics can operate at higher temperatures than the current detectors. Initial data at low temperatures were poorer than commercial detectors with lower RoAs and slightly higher 1/f noise. This comparison at low temperature may change with further optimization of the organic process. The organic diode process is very simple, low cost and non-damaging to the HgCdTe or InSb. It involves thermal evaporation of the organic onto the HgCdTe or InSb followed by evaporation of metal contacts through a shadow mask. Phase 1 demonstrated organic/HaCdTe IR detectors with quantum efficiencies similar to commercial devices operating at higher temperatures. The technology is ready for a Phase 2 to further optimize the processing for IR arrays and to increase yields.

  16. Photochemical Molecular Tailoring for Efficient Diffusion and Reorganization of Organic Nanocrystals for Ultra-Flexible Organic Semiconductor Arrays.

    Science.gov (United States)

    Kang, Jingu; Kim, Jaehyun; Jo, Jeong-Wan; Heo, Jae Sang; Kim, Myung-Gil; Kim, Yong-Hoon; Kim, Jaekyun; Park, Sung Kyu

    2017-01-01

    Solution-processed organic single crystals with high carrier mobility have been actively investigated for diverse applications such as displays, sensors, and next generation electronics on a flexible platform. However, the lack of precise alignment and growth control of organic single crystals impedes the widespread adoption of organic materials in an industrial perspective. Here, a photochemical modification approach is reported tailoring the solubility and molecular diffusivity of polymeric sacrificial layer and sequential batch-type vapor annealing to implement high-performance (average saturation mobility: 8.01 cm(2) V(-1) s(-1) ) organic single-crystal thin film transistors with large channel width including multiple aligned single crystals. Additionally, the mechanical properties of the organic single crystals are systematically investigated with extreme strain conditions such as bending radius of 150 μm.

  17. Engineering interfacial properties of organic semiconductors through soft-contact lamination and surface functionalization

    Science.gov (United States)

    Shu, Andrew Leo

    Organic electronics is a topic of interest due to its potential for low temperature and solution processing for large area and flexible applications. Examples of organic electronic devices are already available on the market; however these are, in general, still rather expensive. In order to fully realize inexpensive and efficient organic electronics, the properties of organic films need to be understood and strategies developed to take advantage of these properties to improve device performance. This work focuses on two strategies that can be used to control charge transport at interfaces with active organic semiconducting thin films. These strategies are studied and verified with a range of photoemission spectroscopy, surface probe microscopy, and electrical measurements. Vacuum evaporated molecular organic devices have long used layer stacking of different materials as a method of dividing roles in a device and modifying energy level alignment to improve device performance and efficiency. Applying this type of architecture for solution-processed devices, on the other hand, is nontrivial, as an issue of removal of or mixing with underlying layers arises. We present and examine here soft-contact lamination as a viable technique for depositing solution-processed multilayer structures. The energetics at homojunctions of a couple of air-stable polymers is investigated. Charge transport is then compared between a two-layer film and a single-layer film of equivalent thicknesses. The interface formed by soft-contact lamination is found to be transparent with respect to electronic charge carriers. We also propose a technique for modifying electronic level alignment at active organic-organic heterojunctions using dipolar self-assembled monolayers (SAM). An ultra-thin metal oxide is first deposited via a gentle low temperature chemical vapor deposition as an adhesion layer for the SAM. The deposition is shown to be successful for a variety of organic films. A series of

  18. Infrared absorption and visible transparency in heavily doped p-type BaSnO3

    Science.gov (United States)

    Li, Yuwei; Sun, Jifeng; Singh, David J.

    2017-01-01

    The recent experimental work shows that perovskite BaSnO3 can be heavily doped by K to become a stable p-type semiconductor. Here, we find that p-type perovskite BaSnO3 retains transparency for visible light while absorbing strongly in the infrared below 1.5 eV. The origin of the remarkable optical transparency even with heavy doping is that the interband transitions that are enabled by empty states at the top of the valence band are concentrated mainly in the energy range from 0.5 to 1.5 eV, i.e., not extending past the near IR. In contrast to n-type, the Burstein-Moss shift is slightly negative, but very small reflecting the heavier valence bands relative to the conduction bands.

  19. Enhancement of p-type mobility in tin monoxide by native defects

    KAUST Repository

    Granato, D. B.

    2013-05-31

    Transparent p-type materials with good mobility are needed to build completely transparent p-n junctions. Tin monoxide (SnO) is a promising candidate. A recent study indicates great enhancement of the hole mobility of SnO grown in Sn-rich environment [E. Fortunato et al., Appl. Phys. Lett. 97, 052105 (2010)]. Because such an environment makes the formation of defects very likely, we study defect effects on the electronic structure to explain the increased mobility. We find that Sn interstitials and O vacancies modify the valence band, inducing higher contributions of the delocalized Sn 5p orbitals as compared to the localized O 2p orbitals, thus increasing the mobility. This mechanism of valence band modification paves the way to a systematic improvement of transparent p-type semiconductors.

  20. Preparation and Photovoltaic Properties of p-Type Nano-ZnFe2O4

    Institute of Scientific and Technical Information of China (English)

    LI Zi-heng; ZOU Xu; LI Gen; ZOU Guang-tian

    2012-01-01

    p-Type nano-ZnFe2O4 semiconductors were gained by high-prssure treatment.Surface photovoltaic spectrum(SPS) and transient photovoltaic technology(TPV) were used for studying the photogenerated charge of nano-ZnFe2O4.Results show that the photovoltaic behavior of nano-ZnFe2O4 changed as the processing pressure increased.When the processing pressure was higher than 2 GPa,both SPS response interval and peak changed significantly.XPS results show that the non-lattice oxygen entered into the lattice and the content of lattice oxygen increased with the increase of processing pressure.The material changed from oxygen vacancy type to oxygen excess type and the photoelectric properties changed from n-type to p-type when the processing pressure is higher than 2GPa.

  1. One-dimensional self-confinement promotes polymorph selection in large-area organic semiconductor thin films

    KAUST Repository

    Giri, Gaurav

    2014-04-16

    A crystal\\'s structure has significant impact on its resulting biological, physical, optical and electronic properties. In organic electronics, 6,13(bis-triisopropylsilylethynyl)pentacene (TIPS-pentacene), a small-molecule organic semiconductor, adopts metastable polymorphs possessing significantly faster charge transport than the equilibrium crystal when deposited using the solution-shearing method. Here, we use a combination of high-speed polarized optical microscopy, in situ microbeam grazing incidence wide-angle X-ray-scattering and molecular simulations to understand the mechanism behind formation of metastable TIPS-pentacene polymorphs. We observe that thin-film crystallization occurs first at the air-solution interface, and nanoscale vertical spatial confinement of the solution results in formation of metastable polymorphs, a one-dimensional and large-area analogy to crystallization of polymorphs in nanoporous matrices. We demonstrate that metastable polymorphism can be tuned with unprecedented control and produced over large areas by either varying physical confinement conditions or by tuning energetic conditions during crystallization through use of solvent molecules of various sizes. © 2014 Macmillan Publishers Limited.

  2. Electron transporting semiconducting polymers in organic electronics.

    Science.gov (United States)

    Zhao, Xingang; Zhan, Xiaowei

    2011-07-01

    Significant progress has been achieved in the preparation of semiconducting polymers over the past two decades, and successful commercial devices based on them are slowly beginning to enter the market. However, most of the conjugated polymers are hole transporting, or p-type, semiconductors that have seen a dramatic rise in performance over the last decade. Much less attention has been devoted to electron transporting, or n-type, materials that have lagged behind their p-type counterparts. Organic electron transporting materials are essential for the fabrication of organic p-n junctions, organic photovoltaic cells (OPVs), n-channel organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs) and complementary logic circuits. In this critical review we focus upon recent developments in several classes of electron transporting semiconducting polymers used in OLEDs, OFETs and OPVs, and survey and analyze what is currently known concerning electron transporting semiconductor architecture, electronic structure, and device performance relationships (87 references).

  3. A novel single-stranded DNA detection method based on organic semiconductor heterojunction

    Science.gov (United States)

    Gu, Wen; Liu, Hongbo; Zhang, Xia; Zhang, Hao; Chen, Xiong; Wang, Jun

    2016-12-01

    We demonstrate a novel DNA detection method with low-cost and disposable advantages by utilizing F16CuPc/CuPc planar organic heterojunction device. Single-stranded DNA (ssDNA) molecules have been well immobilized on the surface of CuPc film observed by atomic force microscopy, producing an obvious electrical response of the device. The conductivity of the organic heterojunction film was significantly increased by ssDNA immobilization because ssDNA molecules brought additional positive charges at heterojunction interface. Furthermore, the thickness dependence of CuPc upper layer on the electrical response was studied to optimize the sensitivity. This study will be helpful for the development of organic heterojunction based biosensors.

  4. A bio-inspired memory device based on interfacing Physarum polycephalum with an organic semiconductor

    Directory of Open Access Journals (Sweden)

    Agostino Romeo

    2015-01-01

    Full Text Available The development of devices able to detect and record ion fluxes is a crucial point in order to understand the mechanisms that regulate communication and life of organisms. Here, we take advantage of the combined electronic and ionic conduction properties of a conducting polymer to develop a hybrid organic/living device with a three-terminal configuration, using the Physarum polycephalum Cell (PPC slime mould as a living bio-electrolyte. An over-oxidation process induces a conductivity switch in the polymer, due to the ionic flux taking place at the PPC/polymer interface. This behaviour endows a current-depending memory effect to the device.

  5. Quasi continuous-wave lasing in organic thin-film semiconductors (Conference Presentation)

    Science.gov (United States)

    Sanadanayaka, Atula S. D.; Yoshida, Kou; Ribierre, Jean-Charles; Matsushima, Toshinori; Adachi, Chihaya

    2016-09-01

    Since the discovery of organic solid-state lasers, great efforts have been devoted to the development of continuous-wave (cw) lasing in organic materials. However, the operation of organic solid-state lasers under optical cw excitation or pulse excitation at a very high repetition rate (quasi-cw excitation) is extremely challenging. In this work, we have demonstrated quasi-continuous-wave (quasi-cw) surface-emitting lasing in a distributed feedback device which combines a second-order grating with an organic thin film of a host material 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) blended with an organic laser dye 4,4'-bis[(N-carbazole)styryl]biphenyl (BSBCz). When pumping the device with optical picosecond pulse excitation, the quasi-cw laser operation maintained up to a repetition rate of 8 MHz. The lasing threshold was around 0.25 μJ cm-2 which was almost independent of the repetition rates. For our laser devices, the maximum repetition rate (8 MHz) is the highest ever reported, and the lasing threshold (0.25 μJ cm-2) is the lowest ever reported. These superior quasi-cw lasing characteristics in BSBCz are accomplished by the less generation of triplet excitons via intersystem crossing because a photoluminescence quantum yield of the blend film is nearly 100% and there is no significant spectral overlap between laser and triplet absorption.[1,2] Triplet quenchers, generally used for the fabrication of organic thin-film lasers, were not necessary in our devices because of negligible accumulation of triplet excitons and a small spectral overlap between emission and triplet absorption. Therefore, we believe that BSBCz is the most promising candidate for the first realization of electrically pumped organic laser diodes in terms of optical characteristics. However, electrical characteristics such as charge carrier mobility, charge carrier capture cross section, etc., are also extremely important and will need further investigation and enhancement for realization of

  6. A bio-inspired memory device based on interfacing Physarum polycephalum with an organic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Romeo, Agostino; Dimonte, Alice; Tarabella, Giuseppe; D’Angelo, Pasquale, E-mail: dangelo@imem.cnr.it, E-mail: iannotta@imem.cnr.it; Erokhin, Victor; Iannotta, Salvatore, E-mail: dangelo@imem.cnr.it, E-mail: iannotta@imem.cnr.it [IMEM-CNR, Institute of Materials for Electronics and Magnetism-National Research Council, Parma 43124 (Italy)

    2015-01-01

    The development of devices able to detect and record ion fluxes is a crucial point in order to understand the mechanisms that regulate communication and life of organisms. Here, we take advantage of the combined electronic and ionic conduction properties of a conducting polymer to develop a hybrid organic/living device with a three-terminal configuration, using the Physarum polycephalum Cell (PPC) slime mould as a living bio-electrolyte. An over-oxidation process induces a conductivity switch in the polymer, due to the ionic flux taking place at the PPC/polymer interface. This behaviour endows a current-depending memory effect to the device.

  7. A method for the combined measurement of volatile and condensable organic AMC in semiconductor applications

    Science.gov (United States)

    Miller, Charles M.; Zaloga, Emily C.; Lobert, Jürgen M.

    2014-04-01

    Monitoring airborne molecular contamination (AMC) at the parts per trillion (ppt) level in cleanroom environments, scanner applications and compressed gas lines is essential for processes, equipment and yield-control. For the operation of EUV tools, in particular, volatile organic contamination is known to have as much impact as condensable organic compounds, which requires a suitable sampling and measurement methodology. Some of the current industry standards use sample traps comprised of porous 2,6-diphenylene-oxide polymer resin, such as Tenax®, for measuring volatile organic (6 C atoms, about toluene and higher) AMC. Inherent problems associated with these traps are a number of artifacts and chemical reactions that reduce accuracy of reported organic AMC concentrations. The break-down of the polymeric material forms false positive artifacts when used in the presence of reactive gases, such as nitrous acid and ozone, which attack and degrade the polymer to form detectable AMC. Most importantly, these traps have poor capture efficiency for volatile organic compounds (VOC). To address the disadvantages of polymer-based sample traps, we developed a method based on carbonaceous, multi-layered adsorbent traps to replace the 2,6-diphenylene-oxide polymer resin sample trap type. Along with the new trap's ability to retain volatile organics, the trap was found to provide artifact-free results. With industry trends towards detecting more contaminants while continuously reducing required reporting limits for those compounds, artifact-free and accurate detection of AMC is needed at the parts per quadrillion (ppq) level. The proposed, multi-layered trap substantially increases laboratory productivity and reduces cost by eliminating the need to analyze condensable and volatile organic compounds in two separate methods. In our studies, even some organic compounds with six C-atoms, that are part of exposure tool OEM requirements, were not effectively retained by polymeric

  8. Evidence of intrinsic ambipolar charge transport in a high band gap organic semiconductor

    OpenAIRE

    Moreno, César; Pfattner, Raphael; Mas-Torrent, Marta; Puigdollers, Joaquim; Bromley, Stefan T.; Rovira, Concepció; Veciana, Jaume; Alcubilla, Ramón

    2012-01-01

    Theoretical and experimental investigations combining in situ Kelvin probe microscopy (KPM) and macroscopic electrical studies are employed to explore the intrinsic transport in dithiophene-tetrathiafulvalene (DT-TTF) single crystal organic field-effect transistors. Our work demonstrates that ambipolar behavior is not restricted only to materials possessing a high electron affinity and thus may be a more general phenomenon. Peer Reviewed

  9. Functionalization of organic semiconductor crystals via the Diels-Alder reaction.

    Science.gov (United States)

    Qualizza, Brittni A; Prasad, Srividya; Chiarelli, M Paul; Ciszek, Jacob W

    2013-05-18

    A surface adlayer is generated on organic single crystals (tetracene and rubrene) using the site specific Diels-Alder reaction and a series of vapor phase dienophiles. X-ray photoelectron spectroscopy (XPS) confirms adsorption on the surfaces of tetracene and rubrene and mass spectrometry demonstrates the reaction's applicability to a range of dienophiles.

  10. Electronic properties and chemistry of metal / organic semiconductor/ S-GaAs(100) heterosructures

    Energy Technology Data Exchange (ETDEWEB)

    Gavrila, G.N.

    2005-10-21

    in the framework of this thesis three perylene derivates are applied as interlayers in metal/organic layer/S-GaAs(100) heterostructures. The aim of this thesis is to prove the influence of different chemical end-groups on the electronic and chemical properties of the interfaces, as well as the molecular orientation in the organic layers. The molecules 3,4,9,10-perylene tetracarbonic acid dianhydride (PTCDA), 3,4,9,10-perylene tetracarbonic acid diimide (PTCDI), and dimethyl-3,4,9,10-perylene tetracarbonic acid diimide (DiMe-PTCDI) were evaporated by organic molecular beam deposition (OMBD) in the ultrahigh vacuum on sulfur-passivated GaAs(001):2 x 1 substrates. Surface-sensitive characterization procedures as photoemission spectroscopy (PES), inverse photoemission spectroscopy (IPES), and near-edge X-ray fine-structure measurements (NEXAFS) were applied for the characterization. Theoretical calculations by means of the density-functional methods were performed, in order to allow an assignment of different components in core-level spectra. The NEXAFS spectra allow a precise determination of the molecule orientation in relation to the substrate. So it can be proved that a small change of chemical end-groups for instance in DiMe-PTCDI compared with PTCDI causes a dramatic change of the molecule orientation. The valence-band spectra of DiMe-PTCDI show an energetic dispersion of 0.2 eV, which can be assigned to a {pi}-orbital overlap and covers the formation of valence bands. The energy-level fitting to the organic-layer/S-GaAs interface as well as the transport band gap of PTCDI, DiMe-PTCDI, and PTCDA were deteminde by means of PES and IPES. The electronic, chemical, and structural properties of metal/organic-layer interfaces were studied by means of core-level spectroscopy and NEXAFS. Mg reacts strongly with the end-groups of PTCDA AND ptcdi, while the In atoms contribute to a charge-transfer process with the perylene cores of all three molecules, whereby the

  11. Studying the operation characteristics and structure of vertical channel copper-phthalocyanine organic semiconductor transistor

    Institute of Scientific and Technical Information of China (English)

    ZHU Min; SONG Ming-xin; GUI Tai-long; WANG Xuan; YIN Jing-hua; WANG Dong-xing; ZHAO Hong

    2005-01-01

    The creation of Au/CuPc/Al/CuPc/structure is a perpendicular type electricity found in the channel of organic static induction transistor. In the following we analyze transistor operation characteristics and machine structural relation. The results express that the transistor drives the voltage low and has no-saturation currentvoltage characteristics. Its operation characteristics are dependant on gate bias voltage and the construction of the aluminum electrode.The vertical channel of organic static induction transistor (OSIT) , with structure of Au/CuPc/Al/CuPc/Cu, has been determined. According to the test results, the relation of its operation characteristics and device structure was analyzed. The results show that this transistor has a low driving voltage and unsaturation Ⅰ-Ⅴ characteristics. Its operation characteristics are dependant on gate bias voltage and the structure of the aluminum electrode.

  12. Lasing in organic semiconductors - time-resolved studies of non-radiative decay processes

    CERN Document Server

    Zenz, C R

    2000-01-01

    Based on the demonstration of optical gain in an organic single crystal of a soluble oligo-phenylene-vinylene with gain values higher than 60 cm-1 and optically pumped lasing in a longitudinal adjustable microcavity based on laddertype polyparaphenylene, the realization of an organic laserdiode is discussed. The output characteristics of the microcavity can be modeled using classical rate equations, however the obtained threshold values are limited by the short excited state lifetime. A comparison with the lifetime measured on isolated molecules shows, that non-radiative decay processes in the solid state are determining the excited state lifetime. Using conventional and a novel field-assisted differential transmission spectroscopy with femtosecond time resolution, two main decay mechanism could be identified. (i) Triplet exciton in para-hexaphenyl is formed by non-geminate recombination of photo-generated polarons. (ii) Dissociation of the luminescent singlet excitons into polarons is important for two reaso...

  13. Evidence of intrinsic ambipolar charge transport in a high band gap organic semiconductor

    OpenAIRE

    Moreno Sierra, César; Pfattner, Raphael; Mas-Torrent, Marta; Puigdollers-González, Joaquim; Bromley, Stefan T.; Rovira Angulo, Concepció; Veciana Miró, Jaume; Alcubilla-González, Ramón

    2012-01-01

    Theoretical and experimental investigations combining in situ Kelvin probe microscopy (KPM) and macroscopic electrical studies are employed to explore the intrinsic transport in dithiophene-tetrathiafulvalene (DT-TTF) single crystal organic field-effect transistors. Our work demonstrates that ambipolar behavior is not restricted only to materials possessing a high electron affinity and thus may be a more general phenomenon. © 2012 The Royal Society of Chemistry.

  14. Robust Manipulation of Magnetism in Dilute Magnetic Semiconductor (Ga,Mn)As by Organic Molecules.

    Science.gov (United States)

    Wang, Xiaolei; Wang, Hailong; Pan, Dong; Keiper, Timothy; Li, Lixia; Yu, Xuezhe; Lu, Jun; Lochner, Eric; von Molnár, Stephan; Xiong, Peng; Zhao, Jianhua

    2015-12-22

    Surface adsorption of organic molecules provides a new method for the robust manipulation of ferromagnetism in (Ga,Mn)As. Electron acceptor and donor molecules yield significant enhancement and suppression, respectively, of ferromagnetism with modulation of the Curie temperature spanning 36 K. Dip-pen nanolithography is employed to directly pattern monolayers on (Ga,Mn)As, which is presented as a novel pathway toward producing magnetic nanostructures.

  15. Nonlinear Transport in Organic Thin Film Transistors with Soluble Small Molecule Semiconductor.

    Science.gov (United States)

    Kim, Hyeok; Song, Dong-Seok; Kwon, Jin-Hyuk; Jung, Ji-Hoon; Kim, Do-Kyung; Kim, SeonMin; Kang, In Man; Park, Jonghoo; Tae, Heung-Sik; Battaglini, Nicolas; Lang, Philippe; Horowitz, Gilles; Bae, Jin-Hyuk

    2016-03-01

    Nonlinear transport is intensively explained through Poole-Frenkel (PF) transport mechanism in organic thin film transistors with solution-processed small molecules, which is, 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene. We outline a detailed electrical study that identifies the source to drain field dependent mobility. Devices with diverse channel lengths enable the extensive exhibition of field dependent mobility due to thermal activation of carriers among traps.

  16. Designing small molecule polyaromatic p- and n-type semiconductor materials for organic electronics

    KAUST Repository

    Collis, Gavin E.

    2015-12-22

    By combining computational aided design with synthetic chemistry, we are able to identify core 2D polyaromatic small molecule templates with the necessary optoelectronic properties for p- and n-type materials. By judicious selection of the functional groups, we can tune the physical properties of the material making them amenable to solution and vacuum deposition. In addition to solubility, we observe that the functional group can influence the thin film molecular packing. By developing structure-property relationships (SPRs) for these families of compounds we observe that some compounds are better suited for use in organic solar cells, while others, varying only slightly in structure, are favoured in organic field effect transistor devices. We also find that the processing conditions can have a dramatic impact on molecular packing (i.e. 1D vs 2D polymorphism) and charge mobility; this has implications for material and device long term stability. We have developed small molecule p- and n-type materials for organic solar cells with efficiencies exceeding 2%. Subtle variations in the functional groups of these materials produces p- and ntype materials with mobilities higher than 0.3 cm2/Vs. We are also interested in using our SPR approach to develop materials for sensor and bioelectronic applications.

  17. Designing small molecule polyaromatic p- and n-type semiconductor materials for organic electronics

    Science.gov (United States)

    Collis, Gavin E.

    2015-12-01

    By combining computational aided design with synthetic chemistry, we are able to identify core 2D polyaromatic small molecule templates with the necessary optoelectronic properties for p- and n-type materials. By judicious selection of the functional groups, we can tune the physical properties of the material making them amenable to solution and vacuum deposition. In addition to solubility, we observe that the functional group can influence the thin film molecular packing. By developing structure-property relationships (SPRs) for these families of compounds we observe that some compounds are better suited for use in organic solar cells, while others, varying only slightly in structure, are favoured in organic field effect transistor devices. We also find that the processing conditions can have a dramatic impact on molecular packing (i.e. 1D vs 2D polymorphism) and charge mobility; this has implications for material and device long term stability. We have developed small molecule p- and n-type materials for organic solar cells with efficiencies exceeding 2%. Subtle variations in the functional groups of these materials produces p- and ntype materials with mobilities higher than 0.3 cm2/Vs. We are also interested in using our SPR approach to develop materials for sensor and bioelectronic applications.

  18. XPS study of the band alignment at ITO/oxide (n-type MoO{sub 3} or p-type NiO) interface

    Energy Technology Data Exchange (ETDEWEB)

    Bernede, J.C. [MOLTECH Anjou, UMR 6200, Universite de Nantes (France); Houari, S.; Khelil, A. [Universite d& #x27; Oran, LPCM2E, Oran Es-Senia (Algeria); Nguyen, D.; Jouan, P.Y.; Mokrani, A.; Cattin, L. [Institut J. Rouxel (IMN), UMR 6502, Universite de Nantes (France); Predeep, P. [Labaratory for Unconventional Electronics and Photonics, Department of Physics, National Institute of Technology, Kerala (India)

    2012-07-15

    While they have different electronic properties n-type MoO{sub 3} and p-type NiO are very efficient as buffer layers between the ITO anode and the organic electron donor in organic photovoltaic cells. While it is admitted that MoO{sub 3} is n-type, its band structure is still under study. Here, the band alignment at the interface of an ITO/MoO{sub 3} heterojunction is studied by X-ray photoelectron spectroscopy (XPS). The same study is realized on the structure ITO/NiO, NiO being a p-type semiconductor. The measurements have been performed on samples obtained under the same experimental conditions as those used to achieve organic photovoltaic cells. The MoO{sub 3} (NiO) upper layer was 3 nm thick. The semidirect XPS technique used to measure the band offsets allows us to estimate the band discontinuities at the interface ITO/MoO{sub 3}: {Delta}E{sub v} = 0.50 eV and {Delta}E{sub c} = 0.90 eV, while at the interface ITO/NiO we have {Delta}E{sub v} = -2.10 eV and {Delta}E{sub c} = -1.90 eV. Therefore, n-type MoO{sub 3} and p-type NiO, which are both very efficient anode buffer layers (ABLs), exhibit different band structure at the contact with ITO. However, the measurement, by means of a Kelvin probe, of the work functions of the structures ITO/NiO and ITO/MoO{sub 3}, shows that they are close and significantly higher than that of ITO alone. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Spectroscopic fingerprints for charge localization in the organic semiconductor (DOEO)4[HgBr4]·TCE

    Science.gov (United States)

    Koplak, Oksana V.; Chernenkaya, Alisa; Medjanik, Katerina; Brambilla, Alberto; Gloskovskii, Andrei; Calloni, Alberto; Elmers, Hans-Joachim; Schönhense, Gerd; Ciccacci, Franco; Morgunov, Roman B.

    2015-05-01

    Changes of the electronic structure accompanied by charge localization and a transition to an antiferromagnetic ground state were observed in the organic semiconductor (DOEO)4[HgBr4]·TCE. Localization starts in the temperature region of about 150 K and the antiferromagnetic state occurs below 60 K. The magnetic moment of the crystal contains contributions of inclusions (droplets), and individual paramagnetic centers formed by localized holes and free charge carriers at 2 K. Two types of inclusions of 100-400 nm and 2-5 nm sizes were revealed by transmission electron microscopy. Studying the temperature- and angular dependence of electron spin resonance (ESR) spectra revealed fingerprints of antiferromagnetic contributions as well as paramagnetic resonance spectra of individual localized charge carriers. The results point on coexistence of antiferromagnetic long and short range order as evident from a second ESR line. Photoelectron spectroscopy in the VUV, soft and hard X-ray range shows temperature-dependent effects upon crossing the critical temperatures around 60 K and 150 K. The substantially different probing depths of soft and hard X-ray photoelectron spectroscopy yield information on the surface termination. The combined investigation using complementary methods at the same sample reveals the close relation of changes in the transport properties and in the energy distribution of electronic states.

  20. Intermolecular band dispersion of quasi-single crystalline organic semiconductor monolayer measured by angle-resolved photoemission spectroscopy

    Science.gov (United States)

    Ohtomo, Manabu; Shimada, Toshihiro; Hasegawa, Tetsuya

    2010-03-01

    Band structure of organic semiconductors is important knowledge to improve the molecular design. Angle-Resolved Photoemission Spectroscopy (ARPES) studies using highly conductive single domain samples grown in-situ is the most direct technique. In this study, we developed a novel method to grow quasi-single crystalline monolayer on conductive substrate and electronic structure was investigated. As a template for orientation control, we used a step-bunched Si(111) substrate with dangling bond termination. In case of pentacene, it was confirmed that the crystal is quasi-single crystal with 2.2^o rotated twins. The band dispersion was identical to that of thin-film phase. The effective mass and transfer integrals are evaluated using two-dimensional tight binding fit and compared with band calculations [1]. We also report the growth of 2,7-Dipheny[1]benzothieno[3,2-b]benzothiophene (DPh-BTBT) [2] on Bi-Si substrate and compare discuss its band structure. [4pt] [1] M.Ohtomo et al., APL 95, 123308 (2009).[0pt] [2] K.Takimiya, JACS 128, 3044 (2006).

  1. The Impact of Interlayer Electronic Coupling on Charge Transport in Organic Semiconductors: A Case Study on Titanylphthalocyanine Single Crystals.

    Science.gov (United States)

    Zhang, Zongpeng; Jiang, Lang; Cheng, Changli; Zhen, Yonggang; Zhao, Guangyao; Geng, Hua; Yi, Yuanping; Li, Liqiang; Dong, Huanli; Shuai, Zhigang; Hu, Wenping

    2016-04-18

    Traditionally, it is believed that three-dimensional transport networks are preferable to those of lower dimensions. We demonstrate that inter-layer electronic couplings may result in a drastic decrease of charge mobilities by utilizing field-effect transistors (FET) based on two phases of titanyl phthalocyanine (TiOPc) crystals. The α-phase crystals with electronic couplings along two dimensions show a maximum mobility up to 26.8 cm(2)  V(-1)  s(-1) . In sharp contrast, the β-phase crystals with extra significant inter-layer electronic couplings show a maximum mobility of only 0.1 cm(2)  V(-1)  s(-1) . Theoretical calculations on the bulk crystals and model slabs reveal that the inter-layer electronic couplings for the β-phase devices will diminish remarkably the device charge transport abilities owing to the coupling direction perpendicular to the current direction. This work provides new insights into the impact of the dimensionality and directionality of the packing arrangements on charge transport in organic semiconductors.

  2. Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin-orbit coupling.

    Science.gov (United States)

    Sun, Dali; van Schooten, Kipp J; Kavand, Marzieh; Malissa, Hans; Zhang, Chuang; Groesbeck, Matthew; Boehme, Christoph; Valy Vardeny, Z

    2016-08-01

    Exploration of spin currents in organic semiconductors (OSECs) induced by resonant microwave absorption in ferromagnetic substrates is appealing for potential spintronics applications. Owing to the inherently weak spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE) response is very subtle; limited by the microwave power applicable under continuous-wave (cw) excitation. Here we introduce a novel approach for generating significant ISHE signals in OSECs using pulsed ferromagnetic resonance, where the ISHE is two to three orders of magnitude larger compared to cw excitation. This strong ISHE enables us to investigate a variety of OSECs ranging from π-conjugated polymers with strong SOC that contain intrachain platinum atoms, to weak SOC polymers, to C60 films, where the SOC is predominantly caused by the curvature of the molecule's surface. The pulsed-ISHE technique offers a robust route for efficient injection and detection schemes of spin currents at room temperature, and paves the way for spin orbitronics in plastic materials.

  3. Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin-orbit coupling

    Science.gov (United States)

    Sun, Dali; van Schooten, Kipp J.; Kavand, Marzieh; Malissa, Hans; Zhang, Chuang; Groesbeck, Matthew; Boehme, Christoph; Valy Vardeny, Z.

    2016-08-01

    Exploration of spin currents in organic semiconductors (OSECs) induced by resonant microwave absorption in ferromagnetic substrates is appealing for potential spintronics applications. Owing to the inherently weak spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE) response is very subtle; limited by the microwave power applicable under continuous-wave (cw) excitation. Here we introduce a novel approach for generating significant ISHE signals in OSECs using pulsed ferromagnetic resonance, where the ISHE is two to three orders of magnitude larger compared to cw excitation. This strong ISHE enables us to investigate a variety of OSECs ranging from π-conjugated polymers with strong SOC that contain intrachain platinum atoms, to weak SOC polymers, to C60 films, where the SOC is predominantly caused by the curvature of the molecule’s surface. The pulsed-ISHE technique offers a robust route for efficient injection and detection schemes of spin currents at room temperature, and paves the way for spin orbitronics in plastic materials.

  4. Avoiding bias effects in NMR experiments for heteronuclear dipole-dipole coupling determinations: principles and application to organic semiconductor materials.

    Science.gov (United States)

    Kurz, Ricardo; Cobo, Marcio Fernando; de Azevedo, Eduardo Ribeiro; Sommer, Michael; Wicklein, André; Thelakkat, Mukundan; Hempel, Günter; Saalwächter, Kay

    2013-09-16

    Carbon-proton dipole-dipole couplings between bonded atoms represent a popular probe of molecular dynamics in soft materials or biomolecules. Their site-resolved determination, for example, by using the popular DIPSHIFT experiment, can be challenged by spectral overlap with nonbonded carbon atoms. The problem can be solved by using very short cross-polarization (CP) contact times, however, the measured modulation curves then deviate strongly from the theoretically predicted shape, which is caused by the dependence of the CP efficiency on the orientation of the CH vector, leading to an anisotropic magnetization distribution even for isotropic samples. Herein, we present a detailed demonstration and explanation of this problem, as well as providing a solution. We combine DIPSHIFT experiments with the rotor-directed exchange of orientations (RODEO) method, and modifications of it, to redistribute the magnetization and obtain undistorted modulation curves. Our strategy is general in that it can also be applied to other types of experiments for heteronuclear dipole-dipole coupling determinations that rely on dipolar polarization transfer. It is demonstrated with perylene-bisimide-based organic semiconductor materials, as an example, in which measurements of dynamic order parameters reveal correlations of the molecular dynamics with the phase structure and functional properties.

  5. Simultaneous transferring and reserving of solar energy as electrical energy in a single organic semiconductor structure

    Energy Technology Data Exchange (ETDEWEB)

    Sengor, T. [Yildiz Technical Univ., Istanbul (Turkey)

    1995-07-01

    Thin and thick films of a doped organic material, referred to as CHLOH, on a special pair of inorganic substrates are investigated experimentally. The final product simultaneously converts and stores radiated energy, such as solar energy. The stability and efficiency of the new thick film structure has been tested since 1984 and the results illustrate that it is useful as an alternative energy source. The other aspect of the material being investigated is the application of a thin CHLOH layer as an active element in optoelectronic devices.

  6. Organic-inorganic semiconductor hybrid systems. Structure, morphology, and electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    El Helou, Mira

    2012-08-22

    This dissertation addresses the preparation and characterization of hybrid semiconducting systems combining organic with inorganic materials. Characterization methods used included to determine the structure, morphology, and thermal stability comprised X-ray diffraction (XRD), atomic force microscopy (AFM), thermal desorption spectroscopy (TDS), and X-ray photoelectron spectroscopy (XPS). One organic-inorganic semiconducting system was pentacene (C{sub 22}H{sub 14}) and zinc oxide. This interface was investigated in detail for pentacene on an oxygen-terminated zinc oxide surface, i.e. ZnO(000 anti 1). An extended study on the promising p-n junction was carried out for pentacene on ZnO with different orientations which exhibit different chemical and structural characteristics: ZnO(000 anti 1), ZnO(0001), and ZnO(10 anti 10). Moreover, the organic crystal structure of pentacene was selectively tuned by carefully choosing the substrate temperature. This defined interface with a physisorbed pentacene layer on ZnO was characterized by optical absorption which depends on the temperature of the measured system, the pentacene film thickness, and the molecular orientation and packing. The high quality of the pentacene films allowed in one case to characterize the Davydov splitting by linear polarized light focused on a single crystallite. Another subject in the field of organic-inorganic hybrid materials comprised conjugated dithiols used as self-assembled monolayers (SAMs) for immobilizing semiconducting CdS nanoparticles (NPs) on Au substrates. It was demonstrated that an appropriate selection and preparation of the conjugated SAMs is crucial for building up a light-addressable potentiometric sensor with a sufficient efficiency. An optimized electron transfer was achieved with SAMs of long range ordering, high stability, and adequate conductivity. This was examined for different linkers and was best for stilbenedithiol immobilized in solution at higher temperatures. Due

  7. Nanostructured Silver Substrates With Stable and Universal SERS Properties: Application to Organic Molecules and Semiconductor Nanoparticles

    Directory of Open Access Journals (Sweden)

    Waurisch C

    2009-01-01

    Full Text Available Abstract Nanostructured silver films have been prepared by thermal deposition on silicon, and their properties as SERS substrates investigated. The optimal conditions of the post-growth annealing of the substrates were established. Atomic force microscopy study revealed that the silver films with relatively dense and homogeneous arrays of 60–80-nm high pyramidal nanoislands are the most efficient for SERS of both organic dye and inorganic nanoparticles analytes. The noticeable enhancement of the Raman signal from colloidal nanoparticles with the help of silver island films is reported for the first time.

  8. Hybrid composites of monodisperse pi-conjugated rodlike organic compounds and semiconductor quantum particles

    DEFF Research Database (Denmark)

    Hensel, V.; Godt, A.; Popovitz-Biro, R.

    2002-01-01

    Composite materials of quantum particles (Q-particles) arranged in layers within crystalline powders of pi-conjugated, rodlike dicarboxylic acids are reported. The synthesis of the composites, either as three-dimensional crystals or as thin films at the air-water interface, comprises a two...... analysis of the solids and grazing incidence X-ray diffraction analysis of the films on water. 2) Topotactic solid/gas reaction of these salts with H2S to convert the metal ions into Q-particles of CdS or PbS embedded in the organic matrix that consists of the acids 6(H) and 8(H). These hybrid materials...

  9. Preparation and operation characteristics of organic semiconductor transistor using thin film Al gate and copper phthalocyanine

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The organic static induction transistors (OSITs) are fabricated by the method of evaporating and plating in a vacuum with copper phthalocyanine (CuPc) dye, and has a five layered structure of Au/CuPc/AL/CuPc/Au. The experiment reveals that OSITs have obtained a low driving voltage, high current density and high switch speed such as IDs = 1.2 × 10-6A/mm2 , and the degree of 1 000 Hz. The OSITs have excellent operation characteristics of typical static induction transistors.

  10. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1987-01-01

    In-depth exploration of the implications of carrier populations and Fermi energies examines distribution of electrons in energy bands and impurity levels of semiconductors. Also: kinetics of semiconductors containing excess carriers, particularly in terms of trapping, excitation, and recombination.

  11. Charge carrier mobilities in organic semiconductor crystals based on the spectral overlap.

    Science.gov (United States)

    Stehr, Vera; Fink, Reinhold F; Deibel, Carsten; Engels, Bernd

    2016-09-05

    The prediction of substance-related charge-transport properties is important for the tayloring of new materials for organic devices, such as organic solar cells. Assuming a hopping process, the Marcus theory is frequently used to model charge transport. Here another approach, which is already widely used for exciton transport, is adapted to charge transport. It is based on the spectral overlap of the vibrational donor and acceptor spectra. As the Marcus theory it is derived from Fermi's Golden rule, however, it contains less approximations, as the molecular vibrations are treated quantum mechanically. In contrast, the Marcus theory reduces all vibrational degrees of freedom to one and treats its influence classically. The approach is tested on different acenes and predicts most of the experimentally available hole mobilities in these materials within a factor of 2. This represents a significant improvement to values obtained from Marcus theory which is qualitatively correct but frequently overestimates the mobilities by factors up to 10. Furthermore, the charge-transport properties of two derivatives of perylene bisimide are investigated. © 2016 Wiley Periodicals, Inc.

  12. Semiconductor Behavior of a Three-Dimensional Strontium-Based Metal-Organic Framework.

    Science.gov (United States)

    Usman, Muhammad; Mendiratta, Shruti; Batjargal, Sainbileg; Haider, Golam; Hayashi, Michitoshi; Rao Gade, Narsinga; Chen, Jenq-Wei; Chen, Yang-Fang; Lu, Kuang-Lieh

    2015-10-21

    The self-assembly of a three-dimensional strontium-based metal-organic framework [Sr(Hbtc)(H2O)]n (1) was achieved through the reaction of Sr(NO3)2 with a 1,2,4-benzenetricarboxylic acid (1,2,4-H3btc) ligand under hydrothermal conditions. This Sr-based metal-organic framework exhibits remarkable semiconducting behavior, as evidenced by theoretical calculations and experimental measurements. Temperature-dependent DC conductivity, near-room-temperature AC conductivity, diffuse reflection spectra, and photoluminescence spectra provide strong proof that compound 1 shows a band gap of 2.3 eV, which is comparable to that for other commonly available semiconducting materials (e.g., CdSe, CdTe, ZnTe, GaP, etc.). The optimized molecular structure and electronic properties (density of states and band gap energy) of 1 were calculated using density functional theory, and the results are consistent with experimental findings. This is the first report on the semiconducting properties of a strontium-based MOF, which will pave the way for further studies in semiconducting MOFs with interesting potential applications in optoelectronic devices.

  13. Quantitative analysis of lattice disorder and crystallite size in organic semiconductor thin films

    KAUST Repository

    Rivnay, Jonathan

    2011-07-07

    The crystallite size and cumulative lattice disorder of three prototypical, high-performing organic semiconducting materials are investigated using a Fourier-transform peak shape analysis routine based on the method of Warren and Averbach (WA). A thorough incorporation of error propagation throughout the multistep analysis and a weighted fitting of Fourier-transformed data to the WA model allows for more accurate results than typically obtained and for determination of confidence bounds. We compare results obtained when assuming two types of column-length distributions, and discuss the benefits of each model in terms of simplicity and accuracy. For strongly disordered materials, the determination of a crystallite size is greatly hindered because disorder dominates the coherence length, not finite size. A simple analysis based on trends of peak widths and Lorentzian components of pseudo-Voigt line shapes as a function of diffraction order is also discussed as an approach to more easily and qualitatively assess the amount and type of disorder present in a sample. While applied directly to organic systems, this methodology is general for the accurate deconvolution of crystalline size and lattice disorder for any material investigated with diffraction techniques. © 2011 American Physical Society.

  14. Importance of surface modification of a microcontact stamp for pattern fidelity of soluble organic semiconductors

    Science.gov (United States)

    Park, Hea-Lim; Lee, Bo-Yeon; Kim, Se-Um; Suh, Jeng-Hun; Kim, Min-Hoi; Lee, Sin-Doo

    2016-01-01

    We described the effect of the ultraviolet ozone (UVO) treatment of a polydimethylsiloxane (PDMS) stamp on the fidelity of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) patterns produced from a TIPS-PEN/polymer blend by selective contact evaporation (SCE). During the SCE process, the TIPS-PEN in contact with the nanoporous PDMS was absorbed into the PDMS stamp, leaving out the TIPS-PEN patterns, complementary to the PDMS patterns, in the noncontact regions. For the case of the untreated, hydrophobic PDMS surface, the TIPS-PEN patterns developed initially were shrunken and eventually disappeared after 24 h due to the steady absorption of the TIPS-PEN in time. In contrast, for the UVO-treated case, the TIPS-PEN patterns were found to maintain the initial shapes over the period of 24 h since the absorption of the TIPS-PEN was limited by the hydrophilic nature of the UVO-treated PDMS. The modified PDMS surface by the UVO for 30 min yielded the highest fidelity of the TIPS-PEN patterns in both height and width. The patterned TIPS-PEN layer by the SCE was implemented into an organic field-effect transistor to demonstrate the viability of the SCE combined with the UVO treatment for solution-processed organic electronic devices.

  15. Absorption and scattering effects by silver nanoparticles near the interface of organic/inorganic semiconductor tandem films

    Energy Technology Data Exchange (ETDEWEB)

    Nemes, Coleen T.; Vijapurapu, Divya K.; Petoukhoff, Christopher E.; Cheung, Gary Z.; O' Carroll, Deirdre M., E-mail: ocarroll@rutgers.edu [Rutgers University, Department of Materials Science and Engineering (United States)

    2013-08-15

    nanoparticles placed near an organic/inorganic interface can be employed for light management in tandem or hybrid organic/inorganic thin-film semiconductor configurations for solar energy harvesting applications or light detection applications.

  16. Thermal Gradient During Vacuum-Deposition Dramatically Enhances Charge Transport in Organic Semiconductors: Toward High-Performance N-Type Organic Field-Effect Transistors.

    Science.gov (United States)

    Kim, Joo-Hyun; Han, Singu; Jeong, Heejeong; Jang, Hayeong; Baek, Seolhee; Hu, Junbeom; Lee, Myungkyun; Choi, Byungwoo; Lee, Hwa Sung

    2017-03-09

    A thermal gradient distribution was applied to a substrate during the growth of a vacuum-deposited n-type organic semiconductor (OSC) film prepared from N,N'-bis(2-ethylhexyl)-1,7-dicyanoperylene-3,4:9,10-bis(dicarboxyimide) (PDI-CN2), and the electrical performances of the films deployed in organic field-effect transistors (OFETs) were characterized. The temperature gradient at the surface was controlled by tilting the substrate, which varied the temperature one-dimensionally between the heated bottom substrate and the cooled upper substrate. The vacuum-deposited OSC molecules diffused and rearranged on the surface according to the substrate temperature gradient, producing directional crystalline and grain structures in the PDI-CN2 film. The morphological and crystalline structures of the PDI-CN2 thin films grown under a vertical temperature gradient were dramatically enhanced, comparing with the structures obtained from either uniformly heated films or films prepared under a horizontally applied temperature gradient. The field effect mobilities of the PDI-CN2-FETs prepared using the vertically applied temperature gradient were as high as 0.59 cm(2) V(-1) s(-1), more than a factor of 2 higher than the mobility of 0.25 cm(2) V(-1) s(-1) submitted to conventional thermal annealing and the mobility of 0.29 cm(2) V(-1) s(-1) from the horizontally applied temperature gradient.

  17. Time-resolved spin-dependent processes in magnetic field effects in organic semiconductors

    Science.gov (United States)

    Peng, Qiming; Li, Xianjie; Li, Feng

    2012-12-01

    We investigated the time-resolved magnetic field effects (MFEs) in tri-(8-hydroxyquinoline)-aluminum (Alq3) based organic light-emitting diodes (OLEDs) through the transient electroluminescence (EL) method. The values of magneto-electroluminescence (MEL) decrease with the time, and the decreasing slope is proportional to the driving voltage. Specifically, negative MELs are seen when the driving voltage is high enough (V > 11 V). We propose a model to elucidate the spin-dependent processes and theoretically simulate the time-resolved MELs. In particular, this dynamic analysis of time-resolved MELs reveals that the intersystem crossing between singlet and triplet electron-hole pairs and the triplet-triplet annihilation are responsible for the time-resolved MELs at the beginning and enduring periods of the pulse, respectively.

  18. Physical Modeling of Activation Energy in Organic Semiconductor Devices based on Energy and Momentum Conservations.

    Science.gov (United States)

    Mao, Ling-Feng; Ning, H; Hu, Changjun; Lu, Zhaolin; Wang, Gaofeng

    2016-04-22

    Field effect mobility in an organic device is determined by the activation energy. A new physical model of the activation energy is proposed by virtue of the energy and momentum conservation equations. The dependencies of the activation energy on the gate voltage and the drain voltage, which were observed in the experiments in the previous independent literature, can be well explained using the proposed model. Moreover, the expression in the proposed model, which has clear physical meanings in all parameters, can have the same mathematical form as the well-known Meyer-Neldel relation, which lacks of clear physical meanings in some of its parameters since it is a phenomenological model. Thus it not only describes a physical mechanism but also offers a possibility to design the next generation of high-performance optoelectronics and integrated flexible circuits by optimizing device physical parameter.

  19. Physical Modeling of Activation Energy in Organic Semiconductor Devices based on Energy and Momentum Conservations

    Science.gov (United States)

    Mao, Ling-Feng; Ning, H.; Hu, Changjun; Lu, Zhaolin; Wang, Gaofeng

    2016-04-01

    Field effect mobility in an organic device is determined by the activation energy. A new physical model of the activation energy is proposed by virtue of the energy and momentum conservation equations. The dependencies of the activation energy on the gate voltage and the drain voltage, which were observed in the experiments in the previous independent literature, can be well explained using the proposed model. Moreover, the expression in the proposed model, which has clear physical meanings in all parameters, can have the same mathematical form as the well-known Meyer-Neldel relation, which lacks of clear physical meanings in some of its parameters since it is a phenomenological model. Thus it not only describes a physical mechanism but also offers a possibility to design the next generation of high-performance optoelectronics and integrated flexible circuits by optimizing device physical parameter.

  20. Accurate on-chip measurement of the Seebeck coefficient of high mobility small molecule organic semiconductors

    Directory of Open Access Journals (Sweden)

    C. N. Warwick

    2015-09-01

    Full Text Available We present measurements of the Seebeck coefficient in two high mobility organic small molecules, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT and 2,9-didecyl-dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (C10-DNTT. The measurements are performed in a field effect transistor structure with high field effect mobilities of approximately 3 cm2/V s. This allows us to observe both the charge concentration and temperature dependence of the Seebeck coefficient. We find a strong logarithmic dependence upon charge concentration and a temperature dependence within the measurement uncertainty. Despite performing the measurements on highly polycrystalline evaporated films, we see an agreement in the Seebeck coefficient with modelled values from Shi et al. [Chem. Mater. 26, 2669 (2014] at high charge concentrations. We attribute deviations from the model at lower charge concentrations to charge trapping.

  1. Photoelectrical stimulation of neuronal cells by an organic semiconductor-electrolyte Interface

    DEFF Research Database (Denmark)

    Abdullaeva, Oliya S.; Schulz, Matthias; Balzer, Frank

    2016-01-01

    As a step toward the realization of neuroprosthetics for vision restoration, we follow an electrophysiological patch-clamp approach to study the fundamental photoelectrical stimulation mechanism of neuronal model cells by an organic semiconductor–electrolyte interface. Our photoactive layer...... consisting of an anilino-squaraine donor blended with a fullerene acceptor is supporting the growth of the neuronal model cell line (N2A cells) without an adhesion layer on it and is not impairing cell viability. The transient photocurrent signal upon illumination from the semiconductor–electrolyte layer...... is able to trigger a passive response of the neuronal cells under physiological conditions via a capacitive coupling mechanism. We study the dynamics of the capacitive transmembrane currents by patch-clamp recordings and compare them to the dynamics of the photocurrent signal and its spectral responsivity...

  2. Ultrafast Electron Transfer at Organic Semiconductor Interfaces: Importance of Molecular Orientation

    KAUST Repository

    Ayzner, Alexander L.

    2015-01-02

    © 2014 American Chemical Society. Much is known about the rate of photoexcited charge generation in at organic donor/acceptor (D/A) heterojunctions overaged over all relative arrangements. However, there has been very little experimental work investigating how the photoexcited electron transfer (ET) rate depends on the precise relative molecular orientation between D and A in thin solid films. This is the question that we address in this work. We find that the ET rate depends strongly on the relative molecular arrangement: The interface where the model donor compound copper phthalocyanine is oriented face-on with respect to the fullerene C60 acceptor yields a rate that is approximately 4 times faster than that of the edge-on oriented interface. Our results suggest that the D/A electronic coupling is significantly enhanced in the face-on case, which agrees well with theoretical predictions, underscoring the importance of controlling the relative interfacial molecular orientation.

  3. Si nanowires organic semiconductor hybrid heterojunction solar cells toward 10% efficiency.

    Science.gov (United States)

    He, Lining; Jiang, Changyun; Wang, Hao; Lai, Donny; Rusli

    2012-03-01

    High-efficiency hybrid solar cells are fabricated using a simple approach of spin coating a transparent hole transporting organic small molecule, 2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD) on silicon nanowires (SiNWs) arrays prepared by electroless chemical etching. The characteristics of the hybrid cells are investigated as a function of SiNWs length from 0.15 to 5 μm. A maximum average power conversion efficiency of 9.92% has been achieved from 0.35 μm length SiNWs cells, despite a 12% shadowing loss and the absence of antireflective coating and back surface field enhancement. It is found that enhanced aggregations in longer SiNWs limit the cell performance due to increased series resistance and higher carrier recombination in the shorter wavelength region. The effects of the Si substrate doping concentrations on the performance of the cells are also investigated. Cells with higher substrate doping concentration exhibit a significant drop in the incident photons-to-current conversion efficiency (IPCE) in the near infrared region. Nevertheless, a promising short circuit current density of 19 mA/cm(2) and IPCE peak of 57% have been achieved for a 0.9 μm length SiNWs cell fabricated on a highly doped substrate with a minority-carrier diffusion length of only 15 μm. The results suggest that such hybrid cells can potentially be realized using Si thin films instead of bulk substrates. This is promising towards realizing low-cost and high-efficiency SiNWs/organic hybrid solar cells.

  4. Role of impurities in determining the exciton diffusion length in organic semiconductors

    Science.gov (United States)

    Curtin, Ian J.; Blaylock, D. Wayne; Holmes, Russell J.

    2016-04-01

    The design and performance of organic photovoltaic cells is dictated, in part, by the magnitude of the exciton diffusion length (LD). Despite the importance of this parameter, there have been few investigations connecting LD and materials purity. Here, we investigate LD for the organic small molecule N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine as native impurities are systematically removed from the material. Thin films deposited from the as-synthesized material yield a value for LD, as measured by photoluminescence quenching, of (3.9 ± 0.5) nm with a corresponding photoluminescence efficiency (ηPL) of (25 ± 1)% and thin film purity of (97.1 ± 1.2)%, measured by high performance liquid chromatography. After purification by thermal gradient sublimation, the value of LD is increased to (4.7 ± 0.5) nm with a corresponding ηPL of (33 ± 1)% and purity of (98.3 ± 0.8)%. Interestingly, a similar behavior is also observed as a function of the deposition boat temperature. Films deposited from the purified material at a high temperature give LD = (5.3 ± 0.8) nm with ηPL = (37 ± 1)% for films with a purity of (99.0 ± 0.3)% purity. Using a model of diffusion by Förster energy transfer, the variation of LD with purity is predicted as a function of ηPL and is in good agreement with measurements. The removal of impurities acts to decrease the non-radiative exciton decay rate and increase the radiative decay rate, leading to increases in both the diffusivity and exciton lifetime. The results of this work highlight the role of impurities in determining LD, while also providing insight into the degree of materials purification necessary to achieve optimized exciton transport.

  5. Piezo-phototronic effect on electroluminescence properties of p-type GaN thin films.

    Science.gov (United States)

    Hu, Youfan; Zhang, Yan; Lin, Long; Ding, Yong; Zhu, Guang; Wang, Zhong Lin

    2012-07-11

    We present that the electroluminescence (EL) properties of Mg-doped p-type GaN thin films can be tuned by the piezo-phototronic effect via adjusting the minority carrier injection efficiency at the metal-semiconductor (M-S) interface by strain induced polarization charges. The device is a metal-semiconductor-metal structure of indium tin oxide (ITO)-GaN-ITO. Under different straining conditions, the changing trend of the transport properties of GaN films can be divided into two types, corresponding to the different c-axis orientations of the films. An extreme value was observed for the integral EL intensity under certain applied strain due to the adjusted minority carrier injection efficiency by piezoelectric charges introduced at the M-S interface. The external quantum efficiency of the blue EL at 430 nm was changed by 5.84% under different straining conditions, which is 1 order of magnitude larger than the change of the green peak at 540 nm. The results indicate that the piezo-phototronic effect has a larger impact on the shallow acceptor states related EL process than on the one related to the deep acceptor states in p-type GaN films. This study has great significance on the practical applications of GaN in optoelectronic devices under a working environment where mechanical deformation is unavoidable such as for flexible/printable light emitting diodes.

  6. Blue to red electroluminescence emission from organic light-emitting diodes based on π-conjugated organic semiconductor materials

    Science.gov (United States)

    Sharbati, Mohammad Taghi; Panahi, Farhad; Nekoei, Abdo-Reza; Emami, Farzin; Niknam, Khodabakhsh

    2014-01-01

    Blue to red organic light-emitting diodes based on a series of newly synthesized distyrylbenzenes have been demonstrated. Their optical properties have been theoretically and experimentally studied in order to inquire into the substitution effects (such as electron-donating, electron-withdrawing, and steric hindrance) on the emission color. Density functional theory at B3LYP/6-311+G(d) level of calculation was employed to obtain the molecular structures and highest occupied molecular orbital and lowest unoccupied molecular orbital surfaces. Electroluminescence emission range of compounds could be tuned by changing the strength of the acceptor component and using push-pull and nonplanarity effects from 483 (blue) to 600 (red) nm.

  7. Laser printed organic semiconductor PQT-12 for bottom-gate organic thin-film transistors: Fabrication and characterization

    Science.gov (United States)

    Makrygianni, M.; Ainsebaa, A.; Nagel, M.; Sanaur, S.; Raptis, Y. S.; Zergioti, I.; Tsamakis, D.

    2016-12-01

    In this work, we report on the effect of laser printed Poly (3,3‴-didodecyl quarter thiophene) on its optical, structural and electrical properties for bottom-gate/bottom-contact organic thin-film transistors applications. This semiconducting π-conjugated polymer was solution-deposited (spin-coated) on a donor substrate and transferred by means of solid phase laser-induced forward transfer (LIFT) technique on SiO2/Si receiver substrates to form the active material. This article presents a detailed study of the electrical properties of the fabricated transistors by measuring the parasitic resistances for gold (Au) and platinum (Pt) as source-drain electrodes, for optimizing OTFTs in terms of contacts. In addition, X-ray diffraction patterns revealed that it is possible to control the polymer microstructure through the choice of solvent. Also, no significant change in polymer chain orientation was observed between two printed patterns at 90 and 130 mJ/cm2 as confirmed by Raman spectra. The results demonstrate hole mobility values of (2.6 ± 1.3) × 10-2 cm2/Vs, and lower parasitic resistance for dielectric surface roughness around 1.2 nm and Pt electrodes. Higher performances are correlated to i) the well-ordering of PQT-12 surface when a high-boiling-point solvent is used and ii) the less limitating Pt source/drain electrodes. This analytical study proves that solid phase LIFT printing is a reliable technology for the fabrication of thin, organic large area electronics in a well-defined manner.

  8. Effects of Charge-Transfer Excitons on the Photophysics of Organic Semiconductors

    Science.gov (United States)

    Hestand, Nicholas J.

    The field of organic electronics has received considerable attention over the past several years due to the promise of novel electronic materials that are cheap, flexible and light weight. While some devices based on organic materials have already emerged on the market (e.g. organic light emitting diodes), a deeper understanding of the excited states within the condensed phase is necessary both to improve current commercial products and to develop new materials for applications that are currently in the commercial pipeline (e.g. organic photovoltaics, wearable displays, and field effect transistors). To this end, a model for pi-conjugated molecular aggregates and crystals is developed and analyzed. The model considers two types of electronic excitations, namely Frenkel and charge-transfer excitons, both of which play a prominent role in determining the nature of the excited states within tightly-packed organic systems. The former consist of an electron-hole pair bound to the same molecule while in the later the electron and hole are located on different molecules. The model also considers the important nuclear reorganization that occurs when the system switches between electronic states. This is achieved using a Holstein-style Hamiltonian that includes linear vibronic coupling of the electronic states to the nuclear motion associated with the high frequency vinyl-stretching and ring-breathing modes. Analysis of the model reveals spectroscopic signatures of charge-transfer mediated J- and H-aggregation in systems where the photophysical properties are determined primarily by charge-transfer interactions. Importantly, such signatures are found to be sensitive to the relative phase of the intermolecular electron and hole transfer integrals, and the relative energy of the Frenkel and charge-transfer states. When the charge-transfer integrals are in phase and the energy of the charge-transfer state is higher than the Frenkel state, the system exhibits J

  9. Aggregation of Organic Semiconductors and Its Influence on Carrier Transport and Solar Cell Performance

    KAUST Repository

    Hu, Hanlin

    2017-08-28

    Photovoltaic technology based on solution-processable organic solar cells (OSCs) provides a promising route towards a low-cost strategy to address the sharply increasing energy demands worldwide. However, up to date, the vast majority of solar cell reports have been based on spin-cast BHJ layers. Spin coating is not compatible with high speed and scalable coating processes, such as blade-coating and slot-die coating, which require the nanoscale morphology to be reproduced in scalable coating methods. And tolerance for thicker BHJ films would also facilitate high speed scalable coating. In the first part of this thesis, we investigate how pre-aggregating the conjugated polymer in solution impacts the charge transport in polymer films. We use P3HT in a wide range of molecular weights in different solvents of common use in organic electronics to investigate how they impact the aggregation behavior in the ink and in the solid state. By deliberately disentangling polymer chains via sonication of the solution in the presence of solvophobic driving forces, we show a remarkable ability to tune aggregation, which directly impacts charge transport, as measured in the context of field effect transistors. The second part of this thesis looks at the impact of the solution-coating method and the photovoltaic performance gap when applying modern BHJ inks developed for spin coating to scalable coating methods, namely blade coating. We ascribe this to significant differences in the drying kinetics between the processes. Emulating the drying kinetics of spin-coating was found to result in performance parity as well as morphological parity across several systems, resulting in demonstration of PTB7:PC71BM solar cells with efficiency of 9% and 6.5% PCEs on glass and flexible PET substrates, respectively. The last part of this thesis looks into going beyond performance parity by leveraging the differences of the scalable coating method to enable highly efficient thick solar cells which

  10. A Passively Mode-Locked Diode-End-Pumped Nd:YAG Laser with a Semiconductor Saturable Absorber Mirror Grown by Metal Organic Chemical Vapour Deposition

    Institute of Scientific and Technical Information of China (English)

    王勇刚; 马骁宇; 李春勇; 张治国; 张丙元; 张志刚

    2003-01-01

    We report the experimental results of a mode-locked diode-end-pumped Nd:YAG laser with a semiconductor saturable absorber mirror(SESAM)from which we achieved a 10ps pulse duration at 150MHz repetition rate.The SESAM was grown by metal organic chemical vapour deposition at low temperature.The recovery time was measured to be 0.5 ps,indicating the potential pulse compression to sub-picoseconds.

  11. Position-controlled III-V compound semiconductor nanowire solar cells by selective-area metal-organic vapor phase epitaxy.

    Science.gov (United States)

    Fukui, Takashi; Yoshimura, Masatoshi; Nakai, Eiji; Tomioka, Katsuhiro

    2012-01-01

    We demonstrate position-controlled III-V semiconductor nanowires (NWs) by using selective-area metal-organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core-shell NW solar cells. We form a 'flexible NW array' without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed.

  12. Localized photovoltaic investigations on organic semiconductors and bulk heterojunction solar cells.

    Science.gov (United States)

    Kollender, Jan Philipp; Gasiorowski, Jacek; Sariciftci, Niyazi Serdar; Mardare, Andrei Ionut; Hassel, Achim Walter

    2014-10-01

    Newly synthesized organic electronics materials are often available in submicrogram amounts only. Photoelectrochemical scanning droplet cell microscopy is a powerful method that allows a comprehensive characterisation of such small amounts including oxidation, reduction potentials, doping, determination of charge carriers, band gap, charge capacity, over-oxidation sensitivity and many more. Localized photoelectrochemical characterization of the poly[4,8-bis-substituted-benzo[1,2-b:4,5-b0]dithiophene-2,6-diyl-alt-4-substituted-thieno [3,4-b] thiophene-2,6-diyl] (PBDTTT-c) and PBDTTT-c:PCBM bulk heterojunction was performed using photoelectrochemical scanning droplet cell microscopy (PE-SDCM). The optical properties and the real and imaginary part of the dielectric function, of the polymer were determined using spectroscopic ellipsometry. The photoelectrochemical characterizations were performed in a three and two electrode configuration of PE-SDCM under laser and white light illumination. The effect of illumination was characterized using dark/illumination sequences. The stability of the photocurrent was studied using longer term (600 s) illumination. Finally the effect of cell configuration and illumination conditions on the photovoltage was studied.

  13. Effect of polaron diffusion on exciton-polaron quenching in disordered organic semiconductors

    Science.gov (United States)

    Coehoorn, R.; Zhang, L.; Bobbert, P. A.; van Eersel, H.

    2017-04-01

    Exciton-polaron quenching (EPQ) is a major efficiency loss process in organic optoelectronic devices, in particular at high excitation densities. Within commonly used models, the rate is assumed to be given by the product of the exciton density, the polaron density, and a constant EPQ rate coefficient, which is proportional to the polaron diffusion coefficient and an EPQ capture radius. In this work, we study the effects of polaron diffusion on the EPQ rate in energetically disordered materials with a Gaussian density of states using kinetic Monte Carlo simulations, and show that the effective rate coefficient can depend strongly on the polaron concentration and on the electric field. We furthermore find that under realistic conditions, the effective value of the capture radius can exceed the expected value of ˜1 nm by up to two orders of magnitude. To a first approximation, the simulation results can be understood from macroscopic diffusion theory, adapted at finite electric fields to include the observed "polaron wind" effect. However, for strongly disordered systems we find distinct deviations from that theory, related to the very small time and spatial scales involved in the capture process.

  14. Local Intermolecular Order Controls Photoinduced Charge Separation at Donor/Acceptor Interfaces in Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Feier, Hilary M.; Reid, Obadiah G.; Pace, Natalie A.; Park, Jaehong; Bergkamp, Jesse J.; Sellinger, Alan; Gust, Devens; Rumbles, Garry

    2016-03-23

    How free charge is generated at organic donor-acceptor interfaces is an important question, as the binding energy of the lowest energy (localized) charge transfer states should be too high for the electron and hole to escape each other. Recently, it has been proposed that delocalization of the electronic states participating in charge transfer is crucial, and aggregated or otherwise locally ordered structures of the donor or the acceptor are the precondition for this electronic characteristic. The effect of intermolecular aggregation of both the polymer donor and fullerene acceptor on charge separation is studied. In the first case, the dilute electron acceptor triethylsilylhydroxy-1,4,8,11,15,18,22,25-octabutoxyphthalocyaninatosilicon(IV) (SiPc) is used to eliminate the influence of acceptor aggregation, and control polymer order through side-chain regioregularity, comparing charge generation in 96% regioregular (RR-) poly(3-hexylthiophene) (P3HT) with its regiorandom (RRa-) counterpart. In the second case, ordered phases in the polymer are eliminated by using RRa-P3HT, and phenyl-C61-butyric acid methyl ester (PC61BM) is used as the acceptor, varying its concentration to control aggregation. Time-resolved microwave conductivity, time-resolved photoluminescence, and transient absorption spectroscopy measurements show that while ultrafast charge transfer occurs in all samples, long-lived charge carriers are only produced in films with intermolecular aggregates of either RR-P3HT or PC61BM, and that polymer aggregates are just as effective in this regard as those of fullerenes.

  15. Compensation of native donor doping in ScN: Carrier concentration control and p-type ScN

    Science.gov (United States)

    Saha, Bivas; Garbrecht, Magnus; Perez-Taborda, Jaime A.; Fawey, Mohammed H.; Koh, Yee Rui; Shakouri, Ali; Martin-Gonzalez, Marisol; Hultman, Lars; Sands, Timothy D.

    2017-06-01

    Scandium nitride (ScN) is an emerging indirect bandgap rocksalt semiconductor that has attracted significant attention in recent years for its potential applications in thermoelectric energy conversion devices, as a semiconducting component in epitaxial metal/semiconductor superlattices and as a substrate material for high quality GaN growth. Due to the presence of oxygen impurities and native defects such as nitrogen vacancies, sputter-deposited ScN thin-films are highly degenerate n-type semiconductors with carrier concentrations in the (1-6) × 1020 cm-3 range. In this letter, we show that magnesium nitride (MgxNy) acts as an efficient hole dopant in ScN and reduces the n-type carrier concentration, turning ScN into a p-type semiconductor at high doping levels. Employing a combination of high-resolution X-ray diffraction, transmission electron microscopy, and room temperature optical and temperature dependent electrical measurements, we demonstrate that p-type Sc1-xMgxN thin-film alloys (a) are substitutional solid solutions without MgxNy precipitation, phase segregation, or secondary phase formation within the studied compositional region, (b) exhibit a maximum hole-concentration of 2.2 × 1020 cm-3 and a hole mobility of 21 cm2/Vs, (c) do not show any defect states inside the direct gap of ScN, thus retaining their basic electronic structure, and (d) exhibit alloy scattering dominating hole conduction at high temperatures. These results demonstrate MgxNy doped p-type ScN and compare well with our previous reports on p-type ScN with manganese nitride (MnxNy) doping.

  16. Optical properties of organic semiconductor thin films. Static spectra and real-time growth studies

    Energy Technology Data Exchange (ETDEWEB)

    Heinemeyer, Ute

    2009-07-20

    The aim of this work was to establish the anisotropic dielectric function of organic thin films on silicon covered with native oxide and to study their optical properties during film growth. While the work focuses mainly on the optical properties of Diindenoperylene (DIP) films, also the optical response of Pentacene (PEN) films during growth is studied for comparison. Spectroscopic ellipsometry and differential reflectance spectroscopy are used to determine the dielectric function of the films ex-situ and in-situ, i.e. in air and in ultrahigh vacuum. Additionally, Raman- and fluorescence spectroscopy is utilized to characterize the DIP films serving also as a basis for spatially resolved optical measurements beyond the diffraction limit. Furthermore, X-ray reflectometry and atomic force microscopy are used to determine important structural and morphological film properties. The absorption spectrum of DIP in solution serves as a monomer reference. The observed vibronic progression of the HOMO-LUMO transition allows the determination of the Huang-Rhys parameter experimentally, which is a measure of the electronic vibrational coupling. The corresponding breathing modes are measured by Raman spectroscopy. The optical properties of DIP films on native oxide show significant differences compared to the monomer spectrum due to intermolecular interactions. First of all, the thin film spectra are highly anisotropic due to the structural order of the films. Furthermore the Frenkel exciton transfer is studied and the energy difference between Frenkel and charge transfer excitons is determined. Real-time measurements reveal optical differences between interfacial or surface molecules and bulk molecules that play an important role for device applications. They are not only performed for DIP films but also for PEN films. While for DIP films on glass the appearance of a new mode is visible, the spectra of PEN show a pronounced energy red-shift during growth. It is shown how the

  17. Materials Design via Optimized Intramolecular Noncovalent Interactions for High-Performance Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiaojie; Liao, Qiaogan; Manley, Eric F.; Wu, Zishan; Wang, Yulun; Wang, Weida; Yang, Tingbin; Shin, Young-Eun; Cheng, Xing; Liang, Yongye; Chen, Lin X.; Baeg, Kang-Jun; Marks, Tobin J.; Guo, Xugang

    2016-03-15

    , planarizing alkoxy substituents. Implementing a head-to-head linkage with an alkyl/alkoxy substitution pattern and a single S···O interaction is a promising strategy for organic electronics materials design.

  18. Time resolved single molecule spectroscopy of semiconductor quantum dot/conjugated organic hybrid nanostructures

    Science.gov (United States)

    Odoi, Michael Yemoh

    Single molecule studies on CdSe quantum dots functionalized with oligo-phenylene vinylene ligands (CdSe-OPV) provide evidence of strong electronic communication that facilitate charge and energy transport between the OPV ligands and the CdSe quantum dot core. This electronic interaction greatly modify, the photoluminescence properties of both bulk and single CdSe-OPV nanostructure thin film samples. Size-correlated wide-field fluorescence imaging show that blinking suppression in single CdSe-OPV is linked to the degree of OPV coverage (inferred from AFM height scans) on the quantum dot surface. The effect of the complex electronic environment presented by photoexcited OPV ligands on the excited state property of CdSe-OPV is measured with single photon counting and photon-pair correlation spectroscopy techniques. Time-tagged-time-resolved (TTTR) single photon counting measurements from individual CdSe-OPV nanostructures, show excited state lifetimes an order of magnitude shorter relative to conventional ZnS/CdSe quantum dots. Second-order intensity correlation measurements g(2)(tau) from individual CdSe-OPV nanostructures point to a weak multi-excitonic character with a strong wavelength dependent modulation depth. By tuning in and out of the absorption of the OPV ligands we observe changes in modulation depth from g(2) (0) ≈ 0.2 to 0.05 under 405 and 514 nm excitation respectively. Defocused images and polarization anisotropy measurements also reveal a well-defined linear dipole emission pattern in single CdSe-OPV nanostructures. These results provide new insights into to the mechanism behind the electronic interactions in composite quantum dot/conjugated organic composite systems at the single molecule level. The observed intensity flickering , blinking suppression and associated lifetime/count rate and antibunching behaviour is well explained by a Stark interaction model. Charge transfer from photo-excitation of the OPV ligands to the surface of the Cd

  19. In situ UV-visible absorption during spin-coating of organic semiconductors: A new probe for organic electronics and photovoltaics

    KAUST Repository

    Abdelsamie, Maged

    2014-01-01

    Spin-coating is the most commonly used technique for the lab-scale production of solution processed organic electronic, optoelectronic and photovoltaic devices. Spin-coating produces the most efficient solution-processed organic solar cells and has been the preferred approach for rapid screening and optimization of new organic semiconductors and formulations for electronic and optoelectronic applications, both in academia and in industrial research facilities. In this article we demonstrate, for the first time, a spin-coating experiment monitored in situ by time resolved UV-visible absorption, the most commonly used, simplest, most direct and robust optical diagnostic tool used in organic electronics. In the first part, we successfully monitor the solution-to-solid phase transformation and thin film formation of poly(3-hexylthiophene) (P3HT), the de facto reference conjugated polymer in organic electronics and photovoltaics. We do so in two scenarios which differ by the degree of polymer aggregation in solution, prior to spin-coating. We find that a higher degree of aggregation in the starting solution results in small but measurable differences in the solid state, which translate into significant improvements in the charge carrier mobility of organic field-effect transistors (OFET). In the second part, we monitor the formation of a bulk heterojunction photoactive layer based on a P3HT-fullerene blend. We find that the spin-coating conditions that lead to slower kinetics of thin film formation favour a higher degree of polymer aggregation in the solid state and increased conjugation length along the polymer backbone. Using this insight, we devise an experiment in which the spin-coating process is interrupted prematurely, i.e., after liquid ejection is completed and before the film has started to form, so as to dramatically slow the thin film formation kinetics, while maintaining the same thickness and uniformity. These changes yield substantial improvements to the

  20. Electronic inhomogeneity in n- and p-type PbTe detected by 125Te NMR

    Science.gov (United States)

    Levin, E. M.; Heremans, J. P.; Kanatzidis, M. G.; Schmidt-Rohr, K.

    2013-09-01

    125Te nuclear magnetic resonance spectra and spin-lattice relaxation of n- and p-type PbTe, self-doping narrow band-gap semiconductors, have been studied and compared to those of p-type GeTe. Spin-lattice relaxation in GeTe can be fit by one component, while that in both PbTe samples must be fit by at least two components, showing electronically homogeneous and inhomogeneous materials, respectively. For PbTe-based materials, the spin-lattice relaxation rate 1/T1 increases linearly with carrier concentration. The data for GeTe fall on the same line and allow us to extend this plot to higher concentrations. Long and short T1 components in both PbTe samples reflect “low,” ˜1017 cm-3, and “high,” ˜1018 cm-3, carrier concentration components. Carrier concentrations in both n- and p-type PbTe samples obtained from the Hall and Seebeck effects generally match the “high” carrier concentration component, and to some extent, ignore the “low” one. This demonstrates that the Hall and Seebeck effects may have a limited ability for the determination of carrier concentration in complex thermoelectric PbTe-based and other multicomponent materials.

  1. Enhanced thermopower and low thermal conductivity in p-type polycrystalline ZrTe5

    Science.gov (United States)

    Hooda, M. K.; Yadav, C. S.

    2017-07-01

    Thermoelectric properties of polycrystalline p-type ZrTe5 are reported in the temperature (T) range of 2-340 K. Thermoelectric power (S) is positive and reaches up to 458 μV/K at 340 K on increasing T. The value of Fermi energy 16 meV suggests a low carrier density of ≈9.5 × 1018 cm-3. A sharp anomaly in S data is observed at 38 K, which seems intrinsic to p-type ZrTe5. The thermal conductivity (κ) value is low (2 W/m K at T = 300 K) with major contribution from the lattice part. Electrical resistivity data show the metal to semiconductor transition at T ˜ 150 K and non-Arrhenius behavior in the semiconducting region. The figure of merit zT (0.026 at T = 300 K) is ˜63% higher than that of HfTe5 (0.016) and better than those of the conventional SnTe, p-type PbTe, and bipolar pristine ZrTe5 compounds.

  2. Fabrication of p-type ZnO nanofibers by electrospinning for field-effect and rectifying devices

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shuai; Liu, Shu-Liang; Liu, Ling-Zhi; Liu, Yi-Chen [College of Physics, Qingdao University, Qingdao 266071 (China); Long, Yun-Ze, E-mail: yunze.long@163.com [College of Physics, Qingdao University, Qingdao 266071 (China); Key Laboratory of Photonics Materials and Technology in Universities of Shandong (Qingdao University), Qingdao 266071 (China); State Key Laboratory Cultivation Base of New Fiber Materials and Modern Textile, Qingdao University, Qingdao 266071 (China); Collaborative Innovation Center for Marine Biomass Fibers, Materials and Textiles of Shandong Province, Qingdao 266071 (China); Zhang, Hong-Di; Zhang, Jun-Cheng; Han, Wen-Peng [College of Physics, Qingdao University, Qingdao 266071 (China); Key Laboratory of Photonics Materials and Technology in Universities of Shandong (Qingdao University), Qingdao 266071 (China)

    2014-01-27

    Ce-doped p-type ZnO nanofibers were synthesized by electrospinning and followed calcinations. The surface morphology, elementary composition, and crystal structure of the nanofibers were investigated. The field effect curve confirms that the resultant Ce-doped ZnO nanofibers are p-type semiconductor. A p-n heterojunction device consisting of Ce-doped p-type ZnO nanofibers and n-type indium tin oxide (ITO) thin film was fabricated on a piece of quartz substrate. The current-voltage (I-V) characteristic of the p-n heterojunction device shows typical rectifying diode behavior. The turn-on voltage appears at about 7 V under the forward bias and the reverse current is impassable.

  3. Model of coherent transport in metal-insulator-midband gap semiconductor-insulator-semiconductor structure

    Science.gov (United States)

    Abramov, I. I.; Danilyuk, A. L.

    1997-08-01

    A kinetic model of coherent transport with self-organized carrier transfer via midband gap semiconductor states in metal-insulator-midband gap semiconductor-insulator-semiconductor structure at room temperature is proposed. The coherent transport at room temperature can be a result of continuous oscillations of charge carriers at midband gap semiconductor states.

  4. Measurement of toxic volatile organic compounds in indoor air of semiconductor foundries using multisorbent adsorption/thermal desorption coupled with gas chromatography-mass spectrometry.

    Science.gov (United States)

    Wu, Chien-Hou; Lin, Ming-Nan; Feng, Chien-Tai; Yang, Kuang-Ling; Lo, Yu-Shiu; Lo, Jiunn-Guang

    2003-05-09

    A method for the qualitative and quantitative analysis of volatile organic compounds (VOCs) in the air of class-100 clean rooms at semiconductor fabrication facilities was developed. Air samples from two semiconductor factories were collected each hour on multisorbent tubes (including Carbopack B, Carbopack C, and Carbosieve SIII) with a 24-h automatic active sampling system and analyzed using adsorption/thermal desorption coupled with gas chromatography-mass spectrometry. Experimental parameters, including thermal desorption temperature, desorption time, and cryofocusing temperature, were optimized. The average recoveries and the method detection limits for the target compounds were in the range 94-101% and 0.31-0.89 ppb, respectively, under the conditions of a 1 L sampling volume and 80% relative humidity. VOCs such as acetone, isopropyl alcohol, 2-heptanone, and toluene, which are commonly used in the semiconductor and electronics industries, were detected and accurately quantified with the established method. Temporal variations of the analyte concentrations observed were attributed to the improper use of organic solvents during operation.

  5. High Performance Organic Semiconductors

    Science.gov (United States)

    2012-07-31

    a stable, solid-state source of fluoride ions that activate the silane ; (2) a Sonogashira-type condensation with dTDPP. This synthetic route...is largely red-shifted, absorbing primarily between 550 nm and 900 nm. From their molecular weights, it can be calculated that the batches of Ph

  6. Organic Field-Effect Transistors Based on a Liquid-Crystalline Polymeric Semiconductor using SU-8 Gate Dielectrics onFlexible Substrates

    Directory of Open Access Journals (Sweden)

    Kornelius Tetzner

    2014-10-01

    Full Text Available In this work, the insulating properties of poly(4-vinylphenol (PVP and SU-8 (MicroChem, Westborough, MA, USA dielectrics are analyzed and compared with each other. We further investigate the performance behavior of organic field-effect transistors based on a semiconducting liquid-crystal polymer (LCP using both dielectric materials and evaluate the results regarding the processability. Due to the lower process temperature needed for the SU-8 deposition, the realization of organic transistors on flexible substrates is demonstrated showing comparable charge carrier mobilities to devices using PVP on glass. In addition, a µ-dispensing procedure of the LCP on SU-8 is presented, improving the switching behavior of the organic transistors, and the promising stability data of the SU-8/LCP stack are verified after storing the structures for 60 days in ambient air showing negligible irreversible degradation of the organic semiconductor.

  7. Semiconductor@metal-organic framework core-shell heterostructures: a case of ZnO@ZIF-8 nanorods with selective photoelectrochemical response.

    Science.gov (United States)

    Zhan, Wen-wen; Kuang, Qin; Zhou, Jian-zhang; Kong, Xiang-jian; Xie, Zhao-xiong; Zheng, Lan-sun

    2013-02-06

    Metal-organic frameworks (MOFs) and related material classes are attracting considerable attention for their applications in gas storage/separation as well as catalysis. In contrast, research concerning potential uses in electronic devices (such as sensors) is in its infancy, which might be due to a great challenge in the fabrication of MOFs and semiconductor composites with well-designed structures. In this paper, we proposed a simple self-template strategy to fabricate metal oxide semiconductor@MOF core-shell heterostructures, and successfully obtained freestanding ZnO@ZIF-8 nanorods as well as vertically standing arrays (including nanorod arrays and nanotube arrays). In this synthetic process, ZnO nanorods not only act as the template but also provide Zn(2+) ions for the formation of ZIF-8. In addition, we have demonstrated that solvent composition and reaction temperature are two crucial factors for successfully fabricating well-defined ZnO@ZIF-8 heterostructures. As we expect, the as-prepared ZnO@ZIF-8 nanorod arrays display distinct photoelectrochemical response to hole scavengers with different molecule sizes (e.g., H(2)O(2) and ascorbic acid) owing to the limitation of the aperture of the ZIF-8 shell. Excitingly, such ZnO@ZIF-8 nanorod arrays were successfully applied to the detection of H(2)O(2) in the presence of serous buffer solution. Therefore, it is reasonable to believe that the semiconductor@MOFs heterostructure potentially has promising applications in many electronic devices including sensors.

  8. Origin and evolution of metal p-Type ATPases in Plantae (Archaeplastida

    Directory of Open Access Journals (Sweden)

    Marc eHanikenne

    2014-01-01

    Full Text Available Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two and are found in prokaryotes as well as in a variety of Eukaryotes. In Arabidopsis thaliana, eight metal P-type ATPases have been described, four being specific to copper transport and four displaying a broader metal specificity, including zinc, cadmium and possibly copper and calcium. So far, few efforts have been devoted to elucidating the origin and evolution of these proteins in Eukaryotes. In this work, we use large-scale phylogenetics to show that metal P-type ATPases form a homogenous group among P-type ATPases and that their specialisation into either monovalent (Cu or divalent (Zn, Cd… metal transport stems from a gene duplication that took place early in the evolution of Life. Then, we demonstrate that the four subgroups of plant metal ATPases all have a different evolutionary origin and a specific taxonomic distribution, only one tracing back to the cyanobacterial progenitor of the chloroplast. Finally, we examine the subsequent evolution of these proteins in green plants and conclude that the genes thoroughly characterised in model organisms are often the result of lineage-specific gene duplications, which calls for caution when attempting to infer function from sequence similarity alone in non-model organisms.

  9. Fine tuning of fluorene-based dye structures for high-efficiency p-type dye-sensitized solar cells.

    Science.gov (United States)

    Liu, Zonghao; Li, Wenhui; Topa, Sanjida; Xu, Xiaobao; Zeng, Xianwei; Zhao, Zhixin; Wang, Mingkui; Chen, Wei; Wang, Feng; Cheng, Yi-Bing; He, Hongshan

    2014-07-09

    We report on an experimental study of three organic push-pull dyes (coded as zzx-op1, zzx-op1-2, and zzx-op1-3) featuring one, two, and three fluorene units as spacers between donors and acceptors for p-type dye-sensitized solar cells (p-DSSC). The results show increasing the number of spacer units leads to obvious increases of the absorption intensity between 300 nm and 420 nm, a subtle increase in hole driving force, and almost the same hole injection rate from dyes to NiO nanoparticles. Under optimized conditions, the zzx-op1-2 dye with two fluorene spacer units outperforms other two dyes in p-DSSC. It exhibits an unprecedented photocurrent density of 7.57 mA cm(-2) under full sun illumination (simulated AM 1.5G light illumination, 100 mW cm(-2)) when the I(-)/I3(-) redox couple and commercial NiO nanoparticles were used as an electrolyte and a semiconductor, respectively. The cells exhibited excellent long-term stability. Theoretical calculations, impedance spectroscopy, and transient photovoltage decay measurements reveal that the zzx-op1-2 exhibits lower photocurrent losses, longer hole lifetime, and higher photogenerated hole density than zzx-op1 and zzx-op1-3. A dye packing model was proposed to reveal the impact of dye aggregation on the overall photovoltaic performance. Our results suggest that the structural engineering of organic dyes is important to enhance the photovoltaic performance of p-DSSC.

  10. Nanoscale characterization of the electrical properties of oxide electrodes at the organic semiconductor-oxide electrode interface in organic solar cells

    Science.gov (United States)

    MacDonald, Gordon Alex

    This dissertation focuses on characterizing the nanoscale and surface averaged electrical properties of transparent conducting oxide electrodes such as indium tin oxide (ITO) and transparent metal-oxide (MO) electron selective interlayers (ESLs), such as zinc oxide (ZnO), the ability of these materials to rapidly extract photogenerated charges from organic semiconductors (OSCs) used in organic photovoltaic (OPV) cells, and evaluating their impact on the power conversion efficiency (PCE) of OPV devices. In Chapter 1, we will introduce the fundamental principles, benefits, and the key innovations that have advanced this technology. In Chapter 2 of this dissertation, we demonstrate an innovative application of conductive probe atomic force microscopy (CAFM) to map the nanoscale electrical heterogeneity at the interface between ITO, and a well-studied OSC, copper phthalocyanine (CuPc).(MacDonald et al. (2012) ACS Nano, 6, p. 9623) In this work we collected arrays of current-voltage (J-V) curves, using a CAFM probe as the top contact of CuPc/ITO systems, to map the local J-V responses. By comparing J-V responses to known models for charge transport, we were able to determine if the local rate-limiting-step for charge transport is through the OSC (ohmic) or the CuPc/ITO interface (non-ohmic). Chapter 3 focus on the electrical property characterization of RF-magnetron sputtered ZnO (sp-ZnO) ESL films on ITO substrates. We have shown that the energetic alignment of ESLs and the OSC active materials plays a critical role in determining the PCE of OPV devices and UV light soaking sensitivity. We have used a combination of device testing, modeling, and impedance spectroscopy to characterize the effects that energetic alignment has on the charge carrier transport and distribution within the OPV device. In Chapter 4 we demonstrate that the local properties of sp-ZnO films varies as a function of the underlying ITO crystal face. We show that the local ITO crystal face determines

  11. Realization of Cu-Doped p-Type ZnO Thin Films by Molecular Beam Epitaxy.

    Science.gov (United States)

    Suja, Mohammad; Bashar, Sunayna B; Morshed, Muhammad M; Liu, Jianlin

    2015-04-29

    Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films, and the best conductivity is achieved with a high hole concentration of 1.54 × 10(18) cm(-3), a low resistivity of 0.6 Ω cm, and a moderate mobility of 6.65 cm(2) V(-1) s(-1) at room temperature. Metal oxide semiconductor capacitor devices have been fabricated on the Cu-doped ZnO films, and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as X-ray diffraction, X-ray photoelectron, Raman, and absorption spectroscopies are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO.

  12. First-principles study of p-type ZnO by S-Na co-doping

    Science.gov (United States)

    Tan, Xingyi; Li, Qiang; Zhu, Yongdan

    2017-08-01

    Using the first-principles method based on the density functional theory, the formation energy, electronic structures of S-Na co-doping in ZnO were calculated. The calculated results show that NaZn-SO have smaller formation energy than Nain-SO in energy ranges from -3.10 to 0 eV of {μ }{{O}}, indicating that it opens up a new opportunity for growth the p-type ZnO. The band structure shows that the NaZn system is a p-type direct-band-gap semiconductor material and the calculated band gap (0.84 eV) is larger than pure ZnO (0.74 eV). The NaZn-SO system is also a p-type semiconductor material with a direct band gap (0.80 eV). The influence of S-Na co-doping in ZnO on p-type conductivity is also discussed. The effective masses of NaZn-SO are larger than effective masses of NaZn and the NaZn-SO have more hole carriers than NaZn, meaning the hole in the NaZn-SO system may have a better carrier transfer character. So we inferred that NaZn-SO should be a candidate of p-type conduction. Project supported by the Natural Science Foundation of Hubei Province, China (Nos. 2014CFB342, 2014CFB619) and the Doctoral Foundation for Scientific Research of Hubei University for Nationalities (No. MY2013B020).

  13. Synthesis, spectral, thermal, optical dispersion and dielectric properties of nanocrystalline dimer complex (PEPyr–diCd) thin films as novel organic semiconductor

    Indian Academy of Sciences (India)

    Ahmed Farouk Al-Hossainy

    2016-02-01

    Dimer complex PEPyr–diCd (5a) has been prepared by reacting CdCl$_2$·2.5H$_2$O with 1,1$'$-bis(diphenylphosphino)ethyl-6-methyl-3-(pyridin-2-yl)-1,4-dihydro-pyridazine tungsten tetracarbonyl PEPyr (4a) as bipyridine ligand. The structural properties of PEPyr–diCd complex were characterized on the basis of elemental analysis (EA), Fourier transform infrared spectra, fast atom bombardment-mass spectrometry, thermogravimetric/ differential thermal analysis, and 1H nuclear magnetic resonance spectroscopy. The crystal is orthorhombic, space group Pbca. Cd(II) metal in PEPyr–diCd organic semiconductor complex coordinated with two N of the PEPyr and three Cl$^−$ (one terminal and two bridging). The micro-structural properties of the films were studied via X-ray diffraction, and scanning electron microscopy. The as-deposited films were annealed in air for 1 h at 150, 200, and 250°C. An average transmittance >70% for PEPyr–diCd complex at higher wavelength >800 nm was observed.In UV spectrum, the transmittance increases followed by a sharp decrease at wavelength 700–750 nm within visible range. The results of the absorption coefficient were determined to find the binding energy (EB) of PEPyr–diCd organic semiconductor complex as 0.242 and 0.47 eV, respectively. Refractive index () and absorption index () of PEPyr–diCd complex were calculated. Moreover, the dispersion parameters such as dispersion energy, oscillator energy, dielectric constant, and dissipation factor were determined. The oxidation of the imino-phosphine derivatives were examined using cyclic voltammetry in methylene chloride solvent. The cyclic voltammogram of PEPyr–diCd (5a) organic semiconductor appears to have two quasi-reversible oxidations at 543 and 441 mV. The obtained results indicate that the PEPyr–diCd organic semiconductor thin film is a good candidate in optoelectronic devices based on its band gap and dispersion parameters.

  14. Scanning probe characterization of novel semiconductor materials and devices

    Science.gov (United States)

    Zhou, Xiaotian

    As semiconductor devices shrink in size, it becomes more important to characterize and understand electronic properties of the materials and devices at the nanoscale. Scanning probe techniques offers numerous advantages over traditional tools used for semiconductor materials and devices characterization including high spatial resolution, ease of use and multi-functionality for electrical characterization, such as current, potential and capacitance, etc. In the first chapter, the basic principle of atomic force microscopy (AFM), and its application to characterization of semiconductor materials and devices are discussed. In the second part of the thesis, scanning capacitance microscopy (SCM), spectroscopy (SCS) and scanning Kelvin probe microscopy (SKPM) are used to investigate the structure and electronic properties of nitride based materials and devices, specifically doping in p-type GaN and electronic structure and morphology of InxGa1-xN/GaN quantum wells. In this work, AFM is used to characterize the local electronic structure in nitride thin film and heterostructures devices. In next part the thesis, AFM is used as an active part of the device, in conductive atomic force microscopy (C-AFM) and scanning gate microscopy (SGM), to study the transport properties and gating effect of InAs semiconductor nanowire based field effect transistor. This is made possible because the nanowire, as a potential one-dimension building block for high performance electronics and optoelectronics, has a diameter comparable to the size of AFM tips. In the last part of the thesis (appendix), SKPM is used to characterize semiconductor-like organic thin films, where measurements of the potential profile along the channel of an organic thin film transistor (OTFT) at different gate bias are presented to illustrate the unique transport property of such devices.

  15. Organic Thin-Film Transistors with Phase Separation of Polymer-Blend Small-Molecule Semiconductors: Dependence on Molecular Weight and Types of Polymer

    Science.gov (United States)

    Ohe, Takahiro; Kuribayashi, Miki; Tsuboi, Ami; Satori, Kotaro; Itabashi, Masao; Nomoto, Kazumasa

    2009-12-01

    We have investigated effect of polymer on solution-processed organic thin-film transistors (TFTs) with polymer-blend semiconductors. Organic TFTs made from a solution of 6,13-bis(triisopropylsilylethynyl)-pentacene with a poly(α-methylstyrene) (PaMS) molecular weight of 20 k or above, exhibited mobility around 0.1 cm2/(V.s). On the other hand, the organic TFTs with a PaMS molecular weight of 2 k or with a poly(isobutyl methacrylate), exhibited much lower mobility. This can be explained in terms of the structure and crystallinity of the films. The results of film structure can be explained by applying the Flory-Huggins theory.

  16. Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

    Institute of Scientific and Technical Information of China (English)

    Li Shang-Sheng; Ma Hong-An; Li Xiao-Lei; Su Tai-Chao; Huang Guo-Feng; Li Yong; Jia Xiao-Peng

    2011-01-01

    High-quality p-type boron-doped II0b diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K. The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively. The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique. The electrical properties including resistivities, Hall coefficients, Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method. The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized. With the increase of quantity of additive boron, some high-index crystal faces such as {113} gradually disappear, and some stripes and triangle pits occur on the crystal surface. This work is helpful for the further research and application of boron-doped semiconductor diamond.

  17. Atomic layer deposition of undoped TiO2 exhibiting p-type conductivity.

    Science.gov (United States)

    Iancu, Andrei T; Logar, Manca; Park, Joonsuk; Prinz, Fritz B

    2015-03-11

    With prominent photocatalytic applications and widespread use in semiconductor devices, TiO2 is one of the most popular metal oxides. However, despite its popularity, it has yet to achieve its full potential due to a lack of effective methods for achieving p-type conductivity. Here, we show that undoped p-type TiO2 films can be fabricated by atomic layer deposition (ALD) and that their electrical properties can be controlled across a wide range using proper postprocessing anneals in various ambient environments. Hole mobilities larger than 400 cm(2)/(V·s) are accessible superseding the use of extrinsic doping, which generally produces orders of magnitude smaller values. Through a combination of analyses and experiments, we provide evidence that this behavior is primarily due to an excess of oxygen in the films. This discovery enables entirely new categories of TiO2 devices and applications, and unlocks the potential to improve existing ones. TiO2 homojunction diodes fabricated completely by ALD are developed as a demonstration of the utility of these techniques and shown to exhibit useful rectifying characteristics even with minimal processing refinement.

  18. Cross-section imaging and p-type doping assessment of ZnO/ZnO:Sb core-shell nanowires by scanning capacitance microscopy and scanning spreading resistance microscopy

    Science.gov (United States)

    Wang, Lin; Sallet, Vincent; Sartel, Corinne; Brémond, Georges

    2016-08-01

    ZnO/ZnO:Sb core-shell structured nanowires (NWs) were grown by the metal organic chemical vapor deposition method where the shell was doped with antimony (Sb) in an attempt to achieve ZnO p-type conduction. To directly investigate the Sb doping effect in ZnO, scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) were performed on the NWs' cross-sections mapping their two dimensional (2D) local electrical properties. Although no direct p-type inversion in ZnO was revealed, a lower net electron concentration was pointed out for the Sb-doped ZnO shell layer with respect to the non-intentionally doped ZnO core, indicating an evident compensating effect as a result of the Sb incorporation, which can be ascribed to the formation of Sb-related acceptors. The results demonstrate SCM/SSRM investigation being a direct and effective approach for characterizing radial semiconductor one-dimensional (1D) structures and, particularly, for the doping study on the ZnO nanomaterial towards its p-type realization.

  19. Cross-section imaging and p-type doping assessment of ZnO/ZnO:Sb core-shell nanowires by scanning capacitance microscopy and scanning spreading resistance microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Lin, E-mail: lin.wang@insa-lyon.fr; Brémond, Georges [Institut des Nanotechnologies de Lyon (INL), Université de Lyon, CNRS UMR 5270, INSA Lyon, Bat. Blaise Pascal, 7 Avenue, Jean Capelle, 69621 Villeurbanne (France); Sallet, Vincent; Sartel, Corinne [Groupe d' étude de la Matière Condensée (GEMaC), CNRS - Université de Versailles St Quentin en Yvelines, Université Paris-Saclay, 45 Avenue des Etats-Unis, 78035 Versailles (France)

    2016-08-29

    ZnO/ZnO:Sb core-shell structured nanowires (NWs) were grown by the metal organic chemical vapor deposition method where the shell was doped with antimony (Sb) in an attempt to achieve ZnO p-type conduction. To directly investigate the Sb doping effect in ZnO, scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM) were performed on the NWs' cross-sections mapping their two dimensional (2D) local electrical properties. Although no direct p-type inversion in ZnO was revealed, a lower net electron concentration was pointed out for the Sb-doped ZnO shell layer with respect to the non-intentionally doped ZnO core, indicating an evident compensating effect as a result of the Sb incorporation, which can be ascribed to the formation of Sb-related acceptors. The results demonstrate SCM/SSRM investigation being a direct and effective approach for characterizing radial semiconductor one-dimensional (1D) structures and, particularly, for the doping study on the ZnO nanomaterial towards its p-type realization.

  20. Semiconductor spintronics

    CERN Document Server

    Xia, Jianbai; Chang, Kai

    2012-01-01

    Semiconductor Spintronics, as an emerging research discipline and an important advanced field in physics, has developed quickly and obtained fruitful results in recent decades. This volume is the first monograph summarizing the physical foundation and the experimental results obtained in this field. With the culmination of the authors' extensive working experiences, this book presents the developing history of semiconductor spintronics, its basic concepts and theories, experimental results, and the prospected future development. This unique book intends to provide a systematic and modern foundation for semiconductor spintronics aimed at researchers, professors, post-doctorates, and graduate students, and to help them master the overall knowledge of spintronics.

  1. Development of Organic Semiconductor for Field -effect Transistor%应用于场效应晶体管有机半导体材料的研究进展

    Institute of Scientific and Technical Information of China (English)

    刘珂; 吴海霞; 张浩力

    2016-01-01

    随着有机电子学的发展,效应晶体管的有机半导体材料相对于传统的单晶硅场效应晶体管材料因其重量轻、柔性、低廉和大面积制备等特点,备受学术界和工业界的广泛青睐。对目前报道过的有机半导体材料进行整理和分类,评述各种类型有机半导体材料的结构特点和性能之间关系,为将来设计合成应用于场效应晶体管的高性能有机半导体材料提供有力指导。%With the development of organic electronics,organic semiconductors for field -effect transistors (FETs) have attracted great attention from both academic and industrial sectors,as they are featured by light weight,high flexibility,low -cost,and large scale fabrication as alternatives to conventional silicon -based transistor semiconductors.In this paper,the main types of organic semiconductors were summarized,and the correlation between the structure and the properties of organic semiconductors were reviewed.This result provides useful guideline for future high performance organic semiconductor design for FET.

  2. Relative Frequencies of G and P Types among Rotaviruses from Indian Diarrheic Cow and Buffalo Calves

    Science.gov (United States)

    Gulati, Baldev R.; Nakagomi, Osamu; Koshimura, Yumi; Nakagomi, Toyoko; Pandey, Ramayan

    1999-01-01

    While an increasing number of studies suggest that there is a high prevalence of rotaviruses with P8[11], a typical P type of bovine rotavirus (BRV), among human neonates or infants in India, no data are available on the distribution of G and P types of Indian BRVs. Thus, fecal specimens were collected from cow and buffalo calves under 1 month of age on organized dairy farms in India during the period between 1994 and 1997, and 36 rotavirus-positive specimens were used to determine the relative frequencies of the G and P types of Indian BRVs. As to the G type, G10 was predominant (83%), followed by G6 (6%). The majority (94%) of BRVs had P8[11], and only one isolate possessed P6[1]. The most common combination of G and P types was G10P8[11] (81%), followed by G6P6[1] (3%) and G6P8[11] (3%). The high prevalence of BRVs possessing P8[11] VP4s strongly supports the hypothesis that BRVs may cross the host species barrier and circulate among neonates in India. PMID:10325385

  3. The dimer-approach to characterize opto-electronic properties of and exciton trapping and diffusion in organic semiconductor aggregates and crystals.

    Science.gov (United States)

    Engels, Bernd; Engel, Volker

    2017-05-24

    A fundamental understanding of photo-induced processes in opto-electronic thin film devices is a prerequisite for the rational design of improved organic semiconductor materials. Absorption and emission spectra provide important insights into the complicated electronic structure of and relaxation processes in organic semiconductor aggregates and crystals. They are of interest because they often limit the efficiencies of the devices. For an assignment of the spectra a close interplay between experiment and theory is essential because simulations are often necessary to entangle the various effects which determine the features of the spectra. In the present perspective we describe the so called dimer-approach and provide a few examples in which this approach could successfully deliver an atomistic picture of photo-induced relaxation effects in perylene-based materials and characterize their optical spectra. The model Hamiltonians of standard monomer-based approaches are also briefly discussed to reveal the differences between both methods and to shed some light on their strengths and shortcomings.

  4. Anisotropic electron-transfer mobilities in diethynyl-indenofluorene-dione crystals as high-performance n-type organic semiconductor materials: remarkable enhancement by varying substituents.

    Science.gov (United States)

    Zhang, Xiao-Yu; Huang, Jin-Dou; Yu, Juan-Juan; Li, Peng; Zhang, Wei-Ping; Frauenheim, Thoma

    2015-10-14

    In this study, the electron-transfer properties of alkynylated indenofluorene-diones with various substituents (SiMe3, SiPr3, and SiPh3) that function as n-type organic semiconductors were comparatively investigated at the first-principles DFT level based on the Marcus-Hush theory. The reorganization energies are calculated by the adiabatic potential-energy surface method, and the coupling terms are evaluated through a direct adiabatic model. The maximum value of the electron-transfer mobility of SiPr3 is 0.485 cm(2) V(-1) s(-1), which appears at the orientation angle of the conducting channel on the reference plane a-b near to 172°/352°. The predicted maximum electron mobility value of SiPr3 is nearly 26 times larger than that of SiPh3. This may be attributed to the largest number of intermolecular π-π interactions. In addition, the mobilities in all three crystals show remarkable anisotropic behavior. The calculated results indicate that SiPr3 could be an ideal candidate as a high-performance n-type organic semiconductor material. Our investigations not only give us an opportunity to completely understand the charge transport mechanisms, but also provide guidelines for designing materials for electronic applications.

  5. Solution-Processed Ambipolar Organic Thin-Film Transistors by Blending p- and n-Type Semiconductors: Solid Solution versus Microphase Separation.

    Science.gov (United States)

    Xu, Xiaomin; Xiao, Ting; Gu, Xiao; Yang, Xuejin; Kershaw, Stephen V; Zhao, Ni; Xu, Jianbin; Miao, Qian

    2015-12-30

    Here, we report solid solution of p- and n-type organic semiconductors as a new type of p-n blend for solution-processed ambipolar organic thin film transistors (OTFTs). This study compares the solid-solution films of silylethynylated tetraazapentacene 1 (acceptor) and silylethynylated pentacene 2 (donor) with the microphase-separated films of 1 and 3, a heptagon-embedded analogue of 2. It is found that the solid solutions of (1)x(2)1-x function as ambipolar semiconductors, whose hole and electron mobilities are tunable by varying the ratio of 1 and 2 in the solid solution. The OTFTs of (1)0.5(2)0.5 exhibit relatively balanced hole and electron mobilities comparable to the highest values as reported for ambipolar OTFTs of stoichiometric donor-acceptor cocrystals and microphase-separated p-n bulk heterojunctions. The solid solution of (1)0.5(2)0.5 and the microphase-separated blend of 1:3 (0.5:0.5) in OTFTs exhibit different responses to light in terms of absorption and photoeffect of OTFTs because the donor and acceptor are mixed at molecular level with π-π stacking in the solid solution.

  6. Semiconductor heterojunctions

    CERN Document Server

    Sharma, B L

    1974-01-01

    Semiconductor Heterojunctions investigates various aspects of semiconductor heterojunctions. Topics covered include the theory of heterojunctions and their energy band profiles, electrical and optoelectronic properties, and methods of preparation. A number of heterojunction devices are also considered, from photovoltaic converters to photodiodes, transistors, and injection lasers.Comprised of eight chapters, this volume begins with an overview of the theory of heterojunctions and a discussion on abrupt isotype and anisotype heterojunctions, along with graded heterojunctions. The reader is then

  7. Engineering magnetism in semiconductors

    Directory of Open Access Journals (Sweden)

    Tomasz Dietl

    2006-11-01

    Full Text Available Transition metal doped III-V, II-VI, and group IV compounds offer an unprecedented opportunity to explore ferromagnetism in semiconductors. Because ferromagnetic spin-spin interactions are mediated by holes in the valence band, changing the Fermi level using co-doping, electric fields, or light can directly manipulate the magnetic ordering. Moreover, engineering the Fermi level position by co-doping makes it possible to modify solubility and self-compensation limits, affecting magnetic characteristics in a number of surprising ways. The Fermi energy can even control the aggregation of magnetic ions, providing a new route to self-organization of magnetic nanostructures in a semiconductor host.

  8. Semiconductor surface protection material

    Science.gov (United States)

    Packard, R. D. (Inventor)

    1973-01-01

    A method and a product for protecting semiconductor surfaces is disclosed. The protective coating material is prepared by heating a suitable protective resin with an organic solvent which is solid at room temperature and converting the resulting solution into sheets by a conventional casting operation. Pieces of such sheets of suitable shape and thickness are placed on the semiconductor areas to be coated and heat and vacuum are then applied to melt the sheet and to drive off the solvent and cure the resin. A uniform adherent coating, free of bubbles and other defects, is thus obtained exactly where it is desired.

  9. Identification of an organic semiconductor superlattice structure of pentacene and perfluoro-pentacene through resonant and non-resonant X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Kowarik, S.; Weber, C. [Humboldt-Universität zu Berlin, Institut für Physik, Newtonstr. 15, 12489 Berlin (Germany); Hinderhofer, A.; Gerlach, A.; Schreiber, F. [Universität Tübingen, Institut für Angewandte Physik, Auf der Morgenstelle 10, 72076 Tübingen (Germany); Wang, C.; Hexemer, A. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Leone, S. R. [Departments of Chemistry and Physics, University of California, and Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2015-11-15

    Highly crystalline and stable molecular superlattices are grown with the smallest possible stacking period using monolayers (MLs) of the organic semiconductors pentacene (PEN) and perfluoro-pentacene (PFP). Superlattice reflections in X-ray reflectivity and their energy dependence in resonant soft X-ray reflectivity measurements show that PFP and PEN MLs indeed alternate even though the coherent ordering is lost after ∼ 4 ML. The observed lattice spacing of 15.9 Å in the superlattice is larger than in pure PEN and PFP films, presumably because of more upright standing molecules and lack of interdigitation between the incommensurate crystalline PEN and PFP layers. The findings are important for the development of novel organic quantum optoelectronic devices.

  10. Identification of an organic semiconductor superlattice structure of pentacene and perfluoro-pentacene through resonant and non-resonant X-ray scattering

    Directory of Open Access Journals (Sweden)

    S. Kowarik

    2015-11-01

    Full Text Available Highly crystalline and stable molecular superlattices are grown with the smallest possible stacking period using monolayers (MLs of the organic semiconductors pentacene (PEN and perfluoro-pentacene (PFP. Superlattice reflections in X-ray reflectivity and their energy dependence in resonant soft X-ray reflectivity measurements show that PFP and PEN MLs indeed alternate even though the coherent ordering is lost after ∼ 4 ML. The observed lattice spacing of 15.9 Å in the superlattice is larger than in pure PEN and PFP films, presumably because of more upright standing molecules and lack of interdigitation between the incommensurate crystalline PEN and PFP layers. The findings are important for the development of novel organic quantum optoelectronic devices.

  11. Growth of nitrogen-doped p-type ZnO thin films prepared by atomic layer epitaxy

    Institute of Scientific and Technical Information of China (English)

    LEE Chongmu; LIM Jongmin; PARK Suyoung; KIM Hyounwoo

    2006-01-01

    Nitrogen-doped, p-type ZnO thin films were grown successfully on sapphire (0001) substrates by using atomic layer epitaxy (ALE). Zn(C2H5)2[Diethylzinc,DEZn], H2O and NH3 were used as a zinc precursor, an oxidant and a doping source gas, respectively. The lowest electrical resistivity of the p-type ZnO films grown by ALE and annealed at 1000 ℃ in an oxygen atmosphere for 1 h was 18.3 Ω·m with a hole concentration of 3.71×1017cm-3 . Low temperature-photoluminescence analysis and time-dependent Hall measurement results support that the nitrogen-doped ZnO after annealing is ap-type semiconductor.

  12. Semimetal/Semiconductor Nanocomposites for Thermoelectrics

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Hong [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Burke, Peter G. [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Gossard, Arthur C. [Univ. of California, Santa Barbara, CA (United States). Materials Dept.; Zeng, Gehong [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering; Ramu, Ashok T. [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering; Bahk, Je-Hyeong [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering; Bowers, John E. [Univ. of California, Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering

    2011-04-15

    In this work, we present research on semimetal-semiconductor nanocomposites grown by molecular beam epitaxy (MBE) for thermoelectric applications. We study several different III-V semiconductors embedded with semimetallic rare earth-group V (RE-V) compounds, but focus is given here to ErSb:InxGa1-xSb as a promising p-type thermoelectric material. Nano­structures of RE-V compounds are formed and embedded within the III-V semiconductor matrix. By codoping the nanocomposites with the appropriate dopants, both n-type and p-type materials have been made for thermoelectric applications. The thermoelectric properties have been engineered for enhanced thermoelectric device performance. Segmented thermoelectric power generator modules using 50 μm thick Er-containing nanocomposites have been fabricated and measured. Research on different rare earth elements for thermoelectrics is discussed.

  13. Does p-type ohmic contact exist in WSe2-metal interfaces?

    Science.gov (United States)

    Wang, Yangyang; Yang, Ruo Xi; Quhe, Ruge; Zhong, Hongxia; Cong, Linxiao; Ye, Meng; Ni, Zeyuan; Song, Zhigang; Yang, Jinbo; Shi, Junjie; Li, Ju; Lu, Jing

    2015-12-01

    Formation of low-resistance metal contacts is the biggest challenge that masks the intrinsic exceptional electronic properties of two dimensional WSe2 devices. We present the first comparative study of the interfacial properties between monolayer/bilayer (ML/BL) WSe2 and Sc, Al, Ag, Au, Pd, and Pt contacts by using ab initio energy band calculations with inclusion of the spin-orbital coupling (SOC) effects and quantum transport simulations. The interlayer coupling tends to reduce both the electron and hole Schottky barrier heights (SBHs) and alters the polarity for the WSe2-Au contact, while the SOC chiefly reduces the hole SBH. In the absence of the SOC, the Pd contact has the smallest hole SBH. Dramatically, the Pt contact surpasses the Pd contact and becomes the p-type ohmic or quasi-ohmic contact with inclusion of the SOC. Therefore, p-type ohmic or quasi-ohmic contact exists in WSe2-metal interfaces. Our study provides a theoretical foundation for the selection of favorable metal electrodes in ML/BL WSe2 devices.Formation of low-resistance metal contacts is the biggest challenge that masks the intrinsic exceptional electronic properties of two dimensional WSe2 devices. We present the first comparative study of the interfacial properties between monolayer/bilayer (ML/BL) WSe2 and Sc, Al, Ag, Au, Pd, and Pt contacts by using ab initio energy band calculations with inclusion of the spin-orbital coupling (SOC) effects and quantum transport simulations. The interlayer coupling tends to reduce both the electron and hole Schottky barrier heights (SBHs) and alters the polarity for the WSe2-Au contact, while the SOC chiefly reduces the hole SBH. In the absence of the SOC, the Pd contact has the smallest hole SBH. Dramatically, the Pt contact surpasses the Pd contact and becomes the p-type ohmic or quasi-ohmic contact with inclusion of the SOC. Therefore, p-type ohmic or quasi-ohmic contact exists in WSe2-metal interfaces. Our study provides a theoretical foundation for

  14. Development in p-type Doping of ZnO

    Institute of Scientific and Technical Information of China (English)

    YU Liping; ZHU Qiqiang; FAN Dayong; LAN Zili

    2012-01-01

    Zinc oxide (ZnO) is a wide band-gap material of the Ⅱ-Ⅵ group with excellent optical properties for optoelectronics applications,such as the flat panel displays and solar cells used in sports tournament.Despite its advantages,the application of ZnO is hampered by the lack of stable p-type doping.In this paper,the recent progress in this field was briefly reviewed,and a comprehensive summary of the research was carried out on ZnO fabrication methods and its electrical,optical,and magnetic properties were presented.

  15. P-type conductivity in annealed strontium titanate

    Energy Technology Data Exchange (ETDEWEB)

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D., E-mail: mattmcc@wsu.edu [Department of Physics and Astronomy, Washington State University, Pullman, WA 99164-2814 (United States)

    2015-12-15

    Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO{sub 3}, or STO) samples that were annealed at 1200°C. Room-temperature mobilities above 100 cm{sup 2}/V s were measured, an order of magnitude higher than those for electrons (5-10 cm{sup 2}/V s). Average hole densities were in the 10{sup 9}-10{sup 10} cm{sup −3} range, consistent with a deep acceptor.

  16. Valorization of GaN based metal-organic chemical vapor deposition dust a semiconductor power device industry waste through mechanochemical oxidation and leaching: A sustainable green process.

    Science.gov (United States)

    Swain, Basudev; Mishra, Chinmayee; Lee, Chan Gi; Park, Kyung-Soo; Lee, Kun-Jae

    2015-07-01

    Dust generated during metal organic vapor deposition (MOCVD) process of GaN based semiconductor power device industry contains significant amounts of gallium and indium. These semiconductor power device industry wastes contain gallium as GaN and Ga0.97N0.9O0.09 is a concern for the environment which can add value through recycling. In the present study, this waste is recycled through mechanochemical oxidation and leaching. For quantitative recovery of gallium, two different mechanochemical oxidation leaching process flow sheets are proposed. In one process, first the Ga0.97N0.9O0.09 of the MOCVD dust is leached at the optimum condition. Subsequently, the leach residue is mechanochemically treated, followed by oxidative annealing and finally re-leached. In the second process, the MOCVD waste dust is mechanochemically treated, followed by oxidative annealing and finally leached. Both of these treatment processes are competitive with each other, appropriate for gallium leaching and treatment of the waste MOCVD dust. Without mechanochemical oxidation, 40.11 and 1.86 w/w% of gallium and Indium are leached using 4M HCl, 100°C and pulp density of 100 kg/m(3,) respectively. After mechanochemical oxidation, both these processes achieved 90 w/w% of gallium and 1.86 w/w% of indium leaching at their optimum condition.

  17. Microscopic studies of the fate of charges in organic semiconductors: Scanning Kelvin probe measurements of charge trapping, transport, and electric fields in p- and n-type devices

    Science.gov (United States)

    Smieska, Louisa Marion

    Organic semiconductors could have wide-ranging applications in lightweight, efficient electronic circuits. However, several fundamental questions regarding organic electronic device behavior have not yet been fully addressed, including the nature of chemical charge traps, and robust models for injection and transport. Many studies focus on engineering devices through bulk transport measurements, but it is not always possible to infer the microscopic behavior leading to the observed measurements. In this thesis, we present scanning-probe microscope studies of organic semiconductor devices in an effort to connect local properties with local device behavior. First, we study the chemistry of charge trapping in pentacene transistors. Working devices are doped with known pentacene impurities and the extent of charge trap formation is mapped across the transistor channel. Trap-clearing spectroscopy is employed to measure an excitation of the pentacene charge trap species, enabling identification of the degradationrelated chemical trap in pentacene. Second, we examine transport and trapping in peryelene diimide (PDI) transistors. Local mobilities are extracted from surface potential profiles across a transistor channel, and charge injection kinetics are found to be highly sensitive to electrode cleanliness. Trap-clearing spectra generally resemble PDI absorption spectra, but one derivative yields evidence indicating variation in trap-clearing mechanisms for different surface chemistries. Trap formation rates are measured and found to be independent of surface chemistry, contradicting a proposed silanol trapping mechanism. Finally, we develop a variation of scanning Kelvin probe microscopy that enables measurement of electric fields through a position modulation. This method avoids taking a numeric derivative of potential, which can introduce high-frequency noise into the electric field signal. Preliminary data is presented, and the theoretical basis for electric field

  18. The Effects of Different Electron-Phonon Couplings on the Spectral and Transport Properties of Small Molecule Single-Crystal Organic Semiconductors

    Directory of Open Access Journals (Sweden)

    Carmine Antonio Perroni

    2014-03-01

    Full Text Available Spectral and transport properties of small molecule single-crystal organic semiconductors have been theoretically analyzed focusing on oligoacenes, in particular on the series from naphthalene to rubrene and pentacene, aiming to show that the inclusion of different electron-phonon couplings is of paramount importance to interpret accurately the properties of prototype organic semiconductors. While in the case of rubrene, the coupling between charge carriers and low frequency inter-molecular modes is sufficient for a satisfactory description of spectral and transport properties, the inclusion of electron coupling to both low-frequency inter-molecular and high-frequency intra-molecular vibrational modes is needed to account for the temperature dependence of transport properties in smaller oligoacenes. For rubrene, a very accurate analysis in the relevant experimental configuration has allowed for the clarification of the origin of the temperature-dependent mobility observed in these organic semiconductors. With increasing temperature, the chemical potential moves into the tail of the density of states corresponding to localized states, but this is not enough to drive the system into an insulating state. The mobility along different crystallographic directions has been calculated, including vertex corrections that give rise to a transport lifetime one order of magnitude smaller than the spectral lifetime of the states involved in the transport mechanism. The mobility always exhibits a power-law behavior as a function of temperature, in agreement with experiments in rubrene. In systems gated with polarizable dielectrics, the electron coupling to interface vibrational modes of the gate has to be included in addition to the intrinsic electron-phonon interaction. While the intrinsic bulk electron-phonon interaction affects the behavior of mobility in the coherent regime below room temperature, the coupling with interface modes is dominant for the

  19. Metal Fluoride Inhibition of a P-type H+ Pump

    Science.gov (United States)

    Pedersen, Jesper Torbøl; Falhof, Janus; Ekberg, Kira; Buch-Pedersen, Morten Jeppe; Palmgren, Michael

    2015-01-01

    The plasma membrane H+-ATPase is a P-type ATPase responsible for establishing electrochemical gradients across the plasma membrane in fungi and plants. This essential proton pump exists in two activity states: an autoinhibited basal state with a low turnover rate and a low H+/ATP coupling ratio and an activated state in which ATP hydrolysis is tightly coupled to proton transport. Here we characterize metal fluorides as inhibitors of the fungal enzyme in both states. In contrast to findings for other P-type ATPases, inhibition of the plasma membrane H+-ATPase by metal fluorides was partly reversible, and the stability of the inhibition varied with the activation state. Thus, the stability of the ATPase inhibitor complex decreased significantly when the pump transitioned from the activated to the basal state, particularly when using beryllium fluoride, which mimics the bound phosphate in the E2P conformational state. Taken together, our results indicate that the phosphate bond of the phosphoenzyme intermediate of H+-ATPases is labile in the basal state, which may provide an explanation for the low H+/ATP coupling ratio of these pumps in the basal state. PMID:26134563

  20. Oxide semiconductors

    CERN Document Server

    Svensson, Bengt G; Jagadish, Chennupati

    2013-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scient