Light-emitting diodes based on solution-processed nontoxic quantum dots: oxides as carrier-transport layers and introducing molybdenum oxide nanoparticles as a hole-inject layer.

Science.gov (United States)

Bhaumik, Saikat; Pal, Amlan J

2014-07-23

We report fabrication and characterization of solution-processed quantum dot light-emitting diodes (QDLEDs) based on a layer of nontoxic and Earth-abundant zinc-diffused silver indium disulfide (AIZS) nanoparticles as an emitting material. In the QDLEDs fabricated on indium tin oxide (ITO)-coated glass substrates, we use layers of oxides, such as graphene oxide (GO) and zinc oxide (ZnO) nanoparticles as a hole- and electron-transport layer, respectively. In addition, we introduce a layer of MoO3 nanoparticles as a hole-inject one. We report a comparison of the characteristics of different device architectures. We show that an inverted device architecture, ITO/ZnO/AIZS/GO/MoO3/Al, yields a higher electroluminescence (EL) emission, compared to direct ones, for three reasons: (1) the GO/MoO3 layers introduce barriers for electrons to reach the Al electrode, and, similarly, the ZnO layers acts as a barrier for holes to travel to the ITO electrode; (2) the introduction of a layer of MoO3 nanoparticles as a hole-inject layer reduces the barrier height for holes and thereby balances charge injection in the inverted structure; and (3) the wide-bandgap zinc oxide next to the ITO electrode does not absorb the EL emission during its exit from the device. In the QDLEDs with oxides as carrier inject and transport layers, the EL spectrum resembles the photoluminescence emission of the emitting material (AIZS), implying that excitons are formed in the quaternary nanocrystals and decay radiatively.

TiO{sub 2} nanofiber solid-state dye sensitized solar cells with thin TiO{sub 2} hole blocking layer prepared by atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Li, Jinwei; Chen, Xi; Xu, Weihe [Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Nam, Chang-Yong, E-mail: cynam@bnl.gov [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973 (United States); Shi, Yong, E-mail: Yong.Shi@stevens.edu [Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)

2013-06-01

We incorporated a thin but structurally dense TiO{sub 2} layer prepared by atomic layer deposition (ALD) as an efficient hole blocking layer in the TiO{sub 2} nanofiber based solid-state dye sensitized solar cell (ss-DSSC). The nanofiber ss-DSSCs having ALD TiO{sub 2} layers displayed increased open circuit voltage, short circuit current density, and power conversion efficiency compared to control devices with blocking layers prepared by spin-coating liquid TiO{sub 2} precursor. We attribute the improved photovoltaic device performance to the structural integrity of ALD-coated TiO{sub 2} layer and consequently enhanced hole blocking effect that results in reduced dark leakage current and increased charge carrier lifetime. - Highlights: • TiO{sub 2} blocking locking layer prepared by atomic layer deposition (ALD) method. • ALD-coated TiO{sub 2} layer enhanced hole blocking effect. • ALD blocking layer improved the voltage, current and efficiency. • ALD blocking layer reduced dark leakage current and increased electron lifetime.

Efficient hole-transporting layer MoO_3:CuI deposited by co-evaporation in organic photovoltaic cells

International Nuclear Information System (INIS)

Barkat, L.; Khelil, A.; Hssein, M.; El Jouad, Z.; Cattin, L.; Louarn, G.; Stephant, N.; Ghamnia, M.; Addou, M.; Morsli, M.; Bernede, J.C.

2017-01-01

In order to improve hole collection at the interface anode/electron donor in organic photovoltaic cells, it is necessary to insert a hole-transporting layer. CuI was shown to be a very efficient hole-transporting layer. However, its tendency to be quite rough tends to induce leakage currents and it is necessary to use a very slow deposition rate for CuI to avoid such negative effect. Herein, we show that the co-deposition of MoO_3 and CuI avoids this difficulty and allows deposition of a homogeneous efficient hole-collecting layer at an acceptable deposition rate. Via an XPS study, we show that blending MoO_3:CuI improves the hole collection efficiency through an increase of the gap state density. This increase is due to the formation of Mo"5"+ following interaction between MoO_3 and CuI. Not only does the co-evaporation process allow for decreasing significantly the deposition time of the hole-transporting layer, but also it increases the efficiency of the device based on the planar heterojunction, CuPc/C_6_0. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Many-body correlation effects in the spatially separated electron and hole layers in the coupled quantum wells

Energy Technology Data Exchange (ETDEWEB)

Babichenko, V.S. [RRC Kurchatov Institute, Kurchatov Sq., 1, 123182 Moscow (Russian Federation); Polishchuk, I.Ya., E-mail: iyppolishchuk@gmail.com [RRC Kurchatov Institute, Kurchatov Sq., 1, 123182 Moscow (Russian Federation); Moscow Institute of Physics and Technology, 141700, 9, Institutskii per., Dolgoprudny, Moscow Region (Russian Federation)

2014-11-15

The many-body correlation effects in the spatially separated electron and hole layers in the coupled quantum wells are investigated. A special case of the many-component electron–hole system is considered. It is shown that if the hole mass is much greater than the electron mass, the negative correlation energy is mainly determined by the holes. The ground state of the system is found to be the 2D electron–hole liquid with the energy smaller than the exciton phase. It is shown that the system decays into the spatially separated neutral electron–hole drops if the initially created charge density in the layers is smaller than the certain critical value n{sub eq}.

Simulation of hole-mobility in doped relaxed and strained Ge layers

Science.gov (United States)

Watling, Jeremy R.; Riddet, Craig; Chan, Morgan Kah H.; Asenov, Asen

2010-11-01

As silicon based metal-oxide-semiconductor field-effect transistors (MOSFETs) are reaching the limits of their performance with scaling, alternative channel materials are being considered to maintain performance in future complementary metal-oxide semiconductor technology generations. Thus there is renewed interest in employing Ge as a channel material in p-MOSFETs, due to the significant improvement in hole mobility as compared to Si. Here we employ full-band Monte Carlo to study hole transport properties in Ge. We present mobility and velocity-field characteristics for different transport directions in p-doped relaxed and strained Ge layers. The simulations are based on a method for over-coming the potentially large dynamic range of scattering rates, which results from the long-range nature of the unscreened Coulombic interaction. Our model for ionized impurity scattering includes the affects of dynamic Lindhard screening, coupled with phase-shift, and multi-ion corrections along with plasmon scattering. We show that all these effects play a role in determining the hole carrier transport in doped Ge layers and cannot be neglected.

Light-hole conduction in InGaAs/GaAs strained-layer superlattices

International Nuclear Information System (INIS)

Schirber, J.E.; Fritz, I.J.; Dawson, L.R.

1985-01-01

We report the first observation of light-hole band carriers in In/sub 0.2/Ga/sub 0.8/As/GaAs strained-layer superlattices by direct measurements of their effective mass (m*m/sub o/ = 0.14) using oscillatory magnetoresistance data. Preferential population of light-hole states, due to splitting of the degenerate bulk valence bands by built-in strain, allows this direct observation

Efficient hole-transporting layer MoO{sub 3}:CuI deposited by co-evaporation in organic photovoltaic cells

Energy Technology Data Exchange (ETDEWEB)

Barkat, L.; Khelil, A. [Universite d' Oran 1 - Ahmed Ben Bella, LPCM2E, Oran (Algeria); Hssein, M. [Universite de Nantes, Institut des Materiaux Jean Rouxel (IMN), CNRS, UMR 6502, Nantes (France); Laboratoire Optoelectronique et Physico-chimie des Materiaux, Universite Ibn Tofail, Faculte des Sciences, Kenitra (Morocco); El Jouad, Z. [Laboratoire Optoelectronique et Physico-chimie des Materiaux, Universite Ibn Tofail, Faculte des Sciences, Kenitra (Morocco); Universite de Nantes, MOLTECH-Anjou, CNRS, UMR 6200, Nantes (France); Cattin, L.; Louarn, G.; Stephant, N. [Universite de Nantes, Institut des Materiaux Jean Rouxel (IMN), CNRS, UMR 6502, Nantes (France); Ghamnia, M. [Universite d' Oran 1 - Ahmed Ben Bella, Laboratoire des Sciences de la Matiere Condensee (LSMC), Oran (Algeria); Addou, M. [Laboratoire Optoelectronique et Physico-chimie des Materiaux, Universite Ibn Tofail, Faculte des Sciences, Kenitra (Morocco); Morsli, M. [Universite de Nantes, Faculte des Sciences et des Techniques, Nantes (France); Bernede, J.C. [Universite de Nantes, MOLTECH-Anjou, CNRS, UMR 6200, Nantes (France)

2017-01-15

In order to improve hole collection at the interface anode/electron donor in organic photovoltaic cells, it is necessary to insert a hole-transporting layer. CuI was shown to be a very efficient hole-transporting layer. However, its tendency to be quite rough tends to induce leakage currents and it is necessary to use a very slow deposition rate for CuI to avoid such negative effect. Herein, we show that the co-deposition of MoO{sub 3} and CuI avoids this difficulty and allows deposition of a homogeneous efficient hole-collecting layer at an acceptable deposition rate. Via an XPS study, we show that blending MoO{sub 3}:CuI improves the hole collection efficiency through an increase of the gap state density. This increase is due to the formation of Mo{sup 5+} following interaction between MoO{sub 3} and CuI. Not only does the co-evaporation process allow for decreasing significantly the deposition time of the hole-transporting layer, but also it increases the efficiency of the device based on the planar heterojunction, CuPc/C{sub 60}. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Acoustic transmission resonance and suppression through double-layer subwavelength hole arrays

International Nuclear Information System (INIS)

Liu Zhifeng; Jin Guojun

2010-01-01

We present a theoretical study of acoustic waves passing through double-layer subwavelength hole arrays. The acoustic transmission resonance and suppression are observed. There are three mechanisms responsible for the transmission resonance: the excitation of geometrically induced acoustic surface waves, the Fabry-Perot resonance in a hole cavity (I-FP resonance) and the Fabry-Perot resonance between two plates (II-FP resonance). We can differentiate these mechanisms via the dispersion relation of acoustic modes supported by the double-layer structure. It is confirmed that the coupling between two single-layer perforated plates, associated with longitudinal interval and lateral displacement, plays a crucial role in modulating the transmission properties. The strong coupling between two plates can induce the splitting of the transmission peak, while the decoupling between plates leads to the appearance of transmission suppression. By analyzing the criterion derived for transmission suppression, we conclude that it is the destructive interference between the diffracted waves and the direct transmission waves assisted by the I-FP resonance of the first plate that leads to the decoupling between plates and then the transmission suppression.

Picosecond kinetics of the electron-hole layers formation in wide-bandgap II-VI type-II heterostructures

Energy Technology Data Exchange (ETDEWEB)

Filatov, E.V.; Zaitsev, S.V.; Tartakovskii, I.I.; Maksimov, A.A. [Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow region (Russian Federation); Yakovlev, D.R. [A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Experimentelle Physik II, Technische Universitaet Dortmund (Germany); Waag, A. [Institute of Semiconductor Technology, Braunschweig Technical University, 38106 Braunschweig (Germany)

2010-06-15

Considerable slowdown of luminescence kinetics of the direct optical transition was discovered in ZnSe/BeTe type-II heterostructures under high levels of optical pumping. The effect is attributed to forming of a potential barrier for holes in the ZnSe layer due to band bending at high densities of spatially separated carriers. That results in a longer time of the photoexcited holes energy relaxation to their ground state in the BeTe layer. The decrease of overlapping of electron and hole wavefunctions in the ZnSe layer in thick ZnSe/BeTe structures at high levels of optical excitation reveals an additional important effect, that leads to sufficient retardation of radiative recombination time for photoexcited carriers (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Electron-Hole Asymmetry of Spin Injection and Transport in Single-Layer Graphene

OpenAIRE

Han, Wei; Wang, W. H.; Pi, K.; McCreary, K. M.; Bao, W.; Li, Yan; Miao, F.; Lau, C. N.; Kawakami, R. K.

2009-01-01

Spin-dependent properties of single-layer graphene (SLG) have been studied by non-local spin valve measurements at room temperature. Gate voltage dependence shows that the non-local magnetoresistance (MR) is proportional to the conductivity of the SLG, which is the predicted behavior for transparent ferromagnetic/nonmagnetic contacts. While the electron and hole bands in SLG are symmetric, gate voltage and bias dependence of the non-local MR reveal an electron-hole asymmetry in which the non-...

Hole-doping of mechanically exfoliated graphene by confined hydration layers

Institute of Scientific and Technical Information of China (English)

Tjeerd R. J. Bollmann[1,2; Liubov Yu. Antipina[3,4; Matthias Temmen[2; Michael Reichling[2; Pavel B. Sorokin[5

2015-01-01

By the use of non-contact atomic force microscopy （NC-AFM） and Kelvin probe force microscopy （KPFM）, we measure the local surface potential of mechanically exfoliated graphene on the prototypical insulating hydrophilic substrate of CAF2（111）. Hydration layers confined between the graphene and the CaF2 substrate, resulting from the graphene＇s preparation under ambient conditions on the hydrophilic substrate surface, are found to electronically modify the graphene as the material＇s electron density transfers from graphene to the hydration layer. Density functional theory （DFT） calculations predict that the first 2 to 3 water layers adjacent to the graphene hole-dope the graphene by several percent of a unit charge per unit cell.

Charge carriers bulk recombination instead of electroplex emission after their tunneling through hole-blocking layer in OLEDs

Science.gov (United States)

Yang, S. Y.; Liu, D.; Jiang, Y.; Teng, F.; Xu, Z.; Hou, Y.; Xu, X. R.

2006-08-01

Charge carriers bulk recombination instead of forming electroplex after their tunneling through a hole-blocking layer, i.e. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), in organic electroluminescence (EL) device ITO/poly-(N-vinyl-carbazole)(PVK)/BCP/tris(8-hydroxyquinoline) aluminum (Alq3)/Al is reported. By changing the thickness of BCP layer, one can find that high electric fields enhance the tunneling process of holes accumulated at the PVK/BCP interface into BCP layer instead of forming “electroplex emission” as reported earlier in literatures. Our experimental data show that charge carriers bulk recombination takes place in both PVK layer and BCP layer, and even in Alq3 layer when BCP layer is thin enough. Further, it is suggested that PVK is the origin of the emission shoulder at 595 nm in the EL spectra of trilayer device ITO/PVK/BCP/Alq3/Al.

Hole and electron extraction layers based on graphene oxide derivatives for high-performance bulk heterojunction solar cells.

Science.gov (United States)

Liu, Jun; Xue, Yuhua; Gao, Yunxiang; Yu, Dingshan; Durstock, Michael; Dai, Liming

2012-05-02

By charge neutralization of carboxylic acid groups in graphene oxide (GO) with Cs(2)CO(3) to afford Cesium-neutralized GO (GO-Cs), GO derivatives with appropriate modification are used as both hole- and electron-extraction layers for bulk heterojunction (BHJ) solar cells. The normal and inverted devices based on GO hole- and GO-Cs electron-extraction layers both outperform the corresponding standard BHJ solar cells. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improved performance of organic solar cells with solution processed hole transport layer

Science.gov (United States)

Bhargav, Ranoo; Gairola, S. P.; Patra, Asit; Naqvi, Samya; Dhawan, S. K.

2018-06-01

This work is based on Cobalt Oxide as solution processed, inexpensive and effective hole transport layer (HTL) for efficient organic photovoltaic applications (OPVs). In Organic solar cell (OSC) devices ITO coated glass substrate used as a transparent anode electrode for light incident, HTL material Co3O4 dissolve in DMF solvent deposited on anode electrode, after that active layer material (donor/acceptor) deposited on to HTL and finally Al were deposited by thermal evaporation used as cathode electrode. These devices were fabricated with PCDTBT well known low band gap donor material in OSCs and blended with PC71BM as an acceptor material using simplest device structure ITO/Co3O4/active layer/Al at ambient conditions. The power conversion efficiencies (PCEs) based on Co3O4 and PEDOT:PSS have been achieved to up to 3.21% and 1.47% with PCDTBT respectively. In this study we reported that the devices fabricated with Co3O4 showed better performance as compare to the devices fabricated with well known and most studied solution processed HTL material PEDOT:PSS under identical environmental conditions. The surface morphology of the HTL film was characterized by (AFM). Lastly, we have provided Co3O4 as an efficient hole transport material HTL for solution processed organic photovoltaic applications.

Organic light-emitting diodes with F16CuPC as an efficient hole-injection layer

International Nuclear Information System (INIS)

Lee, H. K.; Shin, Y. C.; Kwon, D. S.; Lee, C. H.

2006-01-01

We report a new hole-injection material, copper hexadecafluorophthalocyanine (F 16 CuPC) for organic light-emitting diodes (OLEDs) consisting of N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) as a hole-transport layer and 8-tris-hydroxyquinoline aluminum (Alq 3 ) as a light-emitting and electron-transport layer. The insertion of the F 16 CuPC between indium-tin oxide (ITO) and α-NPD reduces the operating voltage significantly and thereby increases the luminous efficiency. By measuring the device characteristics for various F 16 CuPC thicknesses, we find that an optimum F 16 CuPC thickness is about 15 nm. At a luminance of 1000 cd/m 2 , the device with 15-nm-thick F 16 CuPC shows a luminous efficiency of 1.5 lm/W and a device operating voltage of 7.2 V while the device without the F 16 CuPC layer shows 1.1 lm/W and 10.4 V. The significant decrease in a driving voltage and increase in the luminous efficiency can be attributed to the high hole-injection efficiency when F 16 CuPC is inserted between ITO and α-NPD.

Carbazole/triarylamine based polymers as a hole injection/transport layer in organic light emitting devices.

Science.gov (United States)

Wang, Hui; Ryu, Jeong-Tak; Kwon, Younghwan

2012-05-01

This study examined the influence of the charge injection barriers on the performance of organic light emitting diodes (OLEDs) using polymers with a stepwise tuned ionization potential (I(p) approximately -5.01 - -5.29 eV) between the indium tin oxide (ITO) (phi approximately -4.8 eV) anode and tris(8-hydroxyquinolinato) aluminium (Alq3) (I(p) approximately -5.7 eV) layer. The energy levels of the polymers were tuned by structural modification. Double layer devices were fabricated with a configuration of ITO/polymer/Alq3/LiF/Al, where the polymers, Alq3, and LiF/Al were used as the hole injection/transport layer, emissive electron transport layer, and electron injection/cathode, respectively. Using the current density-voltage (J-V), luminescence-voltage (L-V) and efficiencies in these double layer devices, the device performance was evaluated in terms of the energy level alignments at the interfaces, such as the hole injection barriers (phi(h)(iTO/polymer) and phi(h)(polymer/Alq3)) from ITO through the polymers into the Alq3 layer, and the electron injection barrier (phi(e)(polymer/Alq3) or electron/exciton blocking barrier) at the polymer/Alq3 interface.

Hole and electron extraction layers based on graphene oxide derivatives for high-performance bulk heterojunction solar cells

Energy Technology Data Exchange (ETDEWEB)

Liu, Jun; Gao, Yunxiang; Yu, Dingshan; Dai, Liming [Center of Advanced Science and Engineering for Carbon, Department of Macromolecular, Science and Engineering, Case School of Engineering, Case Western Reserve University, Cleveland, Ohio (United States); Xue, Yuhua [Center of Advanced Science and Engineering for Carbon, Department of Macromolecular, Science and Engineering, Case School of Engineering, Case Western Reserve University, Cleveland, Ohio (United States); Institute of Advanced Materials for Nano-Bio Applications, School of Ophthalmology and Optometry, Wenzhou Medical College, Zhejiang 325027 (China); Durstock, Michael [Materials and Manufacturing Directorate, Air Force Research Laboratory, RXBP, Wright-Patterson Air Force Base, Ohio 45433 (United States)

2012-05-02

By charge neutralization of carboxylic acid groups in graphene oxide (GO) with Cs{sub 2}CO{sub 3} to afford Cesium-neutralized GO (GO-Cs), GO derivatives with appropriate modification are used as both hole- and electron-extraction layers for bulk heterojunction (BHJ) solar cells. The normal and inverted devices based on GO hole- and GO-Cs electron-extraction layers both outperform the corresponding standard BHJ solar cells. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Efficient and ultraviolet durable planar perovskite solar cells via a ferrocenecarboxylic acid modified nickel oxide hole transport layer.

Science.gov (United States)

Zhang, Jiankai; Luo, Hui; Xie, Weijia; Lin, Xuanhuai; Hou, Xian; Zhou, Jianping; Huang, Sumei; Ou-Yang, Wei; Sun, Zhuo; Chen, Xiaohong

2018-03-28

Planar perovskite solar cells (PSCs) that use nickel oxide (NiO x ) as a hole transport layer have recently attracted tremendous attention because of their excellent photovoltaic efficiencies and simple fabrication. However, the electrical conductivity of NiO x and the interface contact properties of the NiO x /perovskite layer are always limited for the NiO x layer fabricated at a relatively low annealing temperature. Ferrocenedicarboxylic acid (FDA) was firstly introduced to modify a p-type NiO x hole transport layer in PSCs, which obviously improves the crystallization of the perovskite layer and hole transport and collection abilities and reduces carrier recombination. PSCs with a FDA modified NiO x layer reached a PCE of 18.20%, which is much higher than the PCE (15.13%) of reference PSCs. Furthermore, PSCs with a FDA interfacial modification layer show better UV durability and a hysteresis-free effect and still maintain the original PCE value of 49.8%after being exposed to UV for 24 h. The enhanced performance of the PSCs is attributed to better crystallization of the perovskite layer, the passivation effect of FDA, superior interface contact at the NiO x /perovskite layers and enhancement of the electrical conductivity of the FDA modified NiO x layer. In addition, PSCs with FDA inserted at the interface of the perovskite/PCBM layers can also improve the PCE to 16.62%, indicating that FDA have dual functions to modify p-type and n-type carrier transporting layers.

Solution-Processed rGO/AgNPs/rGO Sandwich Structure as a Hole Extraction Layer for Polymer Solar Cells

Directory of Open Access Journals (Sweden)

Quang Trung Tran

2015-01-01

Full Text Available We found that inserting silver nanoparticles (AgNPs between two layers of reduced grapheme oxide (rGO has an effect on tailoring the work function of rGO. The utilization of rGO/AgNPs/rGO sandwich structure as the hole extraction layer in polymer solar cells is demonstrated. Solution-processable fabrication of this sandwich structure at the ITO/active layer interface facilitates the extraction of hole from active layer into ITO anode because of lowering the barrier level alignment at the interface. It results in an improvement of the short circuit current density and the overall photovoltaic performance.

The inversion layer of electric fields and electron phase-space-hole structure during two-dimensional collisionless magnetic reconnection

International Nuclear Information System (INIS)

Chen Lijen; Lefebvre, Bertrand; Torbert, Roy B.; Daughton, William S.

2011-01-01

Based on two-dimensional fully kinetic simulations that resolve the electron diffusion layer in undriven collisionless magnetic reconnection with zero guide field, this paper reports the existence and evolution of an inversion layer of bipolar electric fields, its corresponding phase-space structure (an electron-hole layer), and the implication to collisionless dissipation. The inversion electric field layer is embedded in the layer of bipolar Hall electric field and extends throughout the entire length of the electron diffusion layer. The electron phase-space hole structure spontaneously arises during the explosive growth phase when there exist significant inflows into the reconnection layer, and electrons perform meandering orbits across the layer while being cyclotron-turned toward the outflow directions. The cyclotron turning of meandering electrons by the magnetic field normal to the reconnection layer is shown to be a primary factor limiting the current density in the region where the reconnection electric field is balanced by the gradient (along the current sheet normal) of the off-diagonal electron pressure-tensor.

The effects of electron and hole transport layer with the electrode work function on perovskite solar cells

Science.gov (United States)

Deng, Quanrong; Li, Yiqi; Chen, Lian; Wang, Shenggao; Wang, Geming; Sheng, Yonglong; Shao, Guosheng

2016-09-01

The effects of electron and hole transport layer with the electrode work function on perovskite solar cells with the interface defects were simulated by using analysis of microelectronic and photonic structures-one-dimensional (AMPS-1D) software. The simulation results suggest that TiO2 electron transport layer provides best device performance with conversion efficiency of 25.9% compared with ZnO and CdS. The threshold value of back electrode work function for Spiro-OMeTAD, NiO, CuI and Cu2O hole transport layer are calculated to be 4.9, 4.8, 4.7 and 4.9 eV, respectively, to reach the highest conversion efficiency. The mechanisms of device physics with various electron and hole transport materials are discussed in details. The device performance deteriorates gradually as the increased density of interface defects located at ETM/absorber or absorber/HTM. This research results can provide helpful guidance for materials and metal electrode choice for perovskite solar cells.

Polyethers with pendent phenylvinyl substituted carbazole rings as polymers for hole transporting layers of OLEDs

Science.gov (United States)

Griniene, R.; Liu, L.; Tavgeniene, D.; Sipaviciute, D.; Volyniuk, D.; Grazulevicius, J. V.; Xie, Z.; Zhang, B.; Leduskrasts, K.; Grigalevicius, S.

2016-01-01

Polyethers containing pendent 3-(2-phenylvinyl)carbazole moieties have been synthesized by the multi-step synthetic routes. Full characterization of their structures is presented. The polymers represent materials of high thermal stability with initial thermal degradation temperatures exceeding 370 °C. The glass transition temperatures of the amorphous materials were in the range of 56-658 °C. The electron photoemission spectra of thin layers of the polymers showed ionization potentials of about 5.6 eV. Hole-transporting properties of the polymeric materials were tested in the structures of organic light emitting diodes with Alq3 as the green emitter and electron transporting layer. The device containing hole-transporting layers of poly{9-[6-(3-methyloxetan-3-ylmethoxy)hexyl]-3-(2-phenylvinyl)carbazole} exhibited the best overall performance with a maximum photometric efficiency of about 4.0 cd/A and maximum brightness exceeding 6430 cd/m2.

Electron and Hole Transport Layers: Their Use in Inverted Bulk Heterojunction Polymer Solar Cells

Directory of Open Access Journals (Sweden)

Sandro Lattante

2014-03-01

Full Text Available Bulk heterojunction polymer solar cells (BHJ PSCs are very promising organic-based devices for low-cost solar energy conversion, compatible with roll-to-roll or general printing methods for mass production. Nevertheless, to date, many issues should still be addressed, one of these being the poor stability in ambient conditions. One elegant way to overcome such an issue is the so-called “inverted” BHJ PSC, a device geometry in which the charge collection is reverted in comparison with the standard geometry device, i.e., the electrons are collected by the bottom electrode and the holes by the top electrode (in contact with air. This reverted geometry allows one to use a high work function top metal electrode, like silver or gold (thus avoiding its fast oxidation and degradation, and eliminates the need of a polymeric hole transport layer, typically of an acidic nature, on top of the transparent metal oxide bottom electrode. Moreover, this geometry is fully compatible with standard roll-to-roll manufacturing in air and is less demanding for a good post-production encapsulation process. To date, the external power conversion efficiencies of the inverted devices are generally comparable to their standard analogues, once both the electron transport layer and the hole transport layer are fully optimized for the particular device. Here, the most recent results on this particular optimization process will be reviewed, and a general outlook regarding the inverted BHJ PSC will be depicted.

Perovskite solar cells with CuSCN hole extraction layers yield stabilized efficiencies greater than 20%

Science.gov (United States)

Arora, Neha; Dar, M. Ibrahim; Hinderhofer, Alexander; Pellet, Norman; Schreiber, Frank; Zakeeruddin, Shaik Mohammed; Grätzel, Michael

2017-11-01

Perovskite solar cells (PSCs) with efficiencies greater than 20% have been realized only with expensive organic hole-transporting materials. We demonstrate PSCs that achieve stabilized efficiencies exceeding 20% with copper(I) thiocyanate (CuSCN) as the hole extraction layer. A fast solvent removal method enabled the creation of compact, highly conformal CuSCN layers that facilitate rapid carrier extraction and collection. The PSCs showed high thermal stability under long-term heating, although their operational stability was poor. This instability originated from potential-induced degradation of the CuSCN/Au contact. The addition of a conductive reduced graphene oxide spacer layer between CuSCN and gold allowed PSCs to retain >95% of their initial efficiency after aging at a maximum power point for 1000 hours under full solar intensity at 60°C. Under both continuous full-sun illumination and thermal stress, CuSCN-based devices surpassed the stability of spiro-OMeTAD-based PSCs.

Effects of the thickness of NiO hole transport layer on the performance of all-inorganic quantum dot light emitting diode

International Nuclear Information System (INIS)

Zhang, Xiao Li; Dai, Hai Tao; Zhao, Jun Liang; Li, Chen; Wang, Shu Guo; Sun, Xiao Wei

2014-01-01

All-inorganic quantum dot light emitting diodes (QLEDs) have recently gained great attention owing to their high stability under oxygenic, humid environment and higher operating currents. In this work, we fabricated all-inorganic CdSe/ZnS core-shell QLEDs composed of ITO/NiO/QDs/ZnO/Al, in which NiO and ZnO thin film deposited via all-solution method were employed as hole and electron transport layer, respectively. To achieve high light emitting efficiency, the balance transport between electrons and holes play a key role. In this work, the effects of the thickness of NiO film on the performance of QLEDs were explored experimentally in details. NiO layers with various thicknesses were prepared with different rotation speeds. Experimental results showed that thinner NiO layer deposited at higher rotation speed had higher transmittance and larger band gap. Four typical NiO thickness based QLEDs were fabricated to optimize the hole transport layer. Thinner NiO layer based device performs bright emission with high current injection, which is ascribed to the reduced barrier height between hole transport layer and quantum dot. - Highlights: • All-inorganic quantum dot light emitting diodes (QLEDs) were fabricated. • Thinner NiO film can effectively enhance on–off properties of devices. • Improved performance of QLEDs is mainly attributed to energy barrier reduction

Effect of the post-annealing temperature on the thermal-decomposed NiOx hole contact layer for perovskite solar cells

Directory of Open Access Journals (Sweden)

Yuxiao Guo

2018-02-01

Full Text Available A hysteresis-less inverted perovskite solar cell (PSC with power conversion efficiency (PCE of 13.57% was successfully achieved based on the thermal-decomposed NiOx hole contact layer, possessing better electron blocking and hole extraction properties for its suitable work function and high-conduction band edge position. Herein, the transparent and high-crystalline NiOx film is prepared by thermal-decomposing of the solution-derived Ni(OH2 film in our study, which is then employed as hole transport layer (HTL of the organic–inorganic hybrid PSCs. Reasonably, the post-annealing treatment, especially for the annealing temperature, could greatly affect the Ni(OH2 decomposition process and the quality of decomposed NiOx nanoparticles. The vital NiOx HTLs with discrepant morphology, crystallinity and transmission certainly lead to a wide range of device performance. As a result, an annealing process of 400∘C/2h significantly promotes the photovoltaic properties of the NiOx layer and the further device performance.

Influence of the thickness of electrochemically deposited polyaniline used as hole transporting layer on the behaviour of polymer light-emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Alonso, J.L. [Dpto. de Fisica y Arquitectura de Computadores, Universidad Miguel Hernandez, Av. de la Universidad s/n, Ed. Torrepinet, 03202, Elche, Alicante (Spain)], E-mail: j.l.alonso@umh.es; Ferrer, J.C. [Dpto. de Fisica y Arquitectura de Computadores, Universidad Miguel Hernandez, Av. de la Universidad s/n, Ed. Torrepinet, 03202, Elche, Alicante (Spain); Cotarelo, M.A.; Montilla, F. [Dpto. de Quimica Fisica e Instituto Universitario de Materiales de Alicante, Apdo. de Correos 99, E-03080, Alicante (Spain); Fernandez de Avila, S. [Dpto. de Fisica y Arquitectura de Computadores, Universidad Miguel Hernandez, Av. de la Universidad s/n, Ed. Torrepinet, 03202, Elche, Alicante (Spain)

2009-02-27

An experimental study about the influence of the thickness of electrochemically deposited polyaniline (PANI), used as hole-transporting layer, on the behaviour of polymer light emitting diodes is presented. Two sets of devices with a different conjugated polymer used as active layer were prepared. Poly(9-vinylcarbazole) was used for the first type of devices, whereas Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene] was used for the second type. Each set consists of five polymeric diodes in which the hole-transporting layer has been varied. In one case of each set no layer was deposited, in other one a Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) layer was deposited, and in the rest of the diodes a different thickness of electrochemically deposited PANI was employed. The optic and electronic characterization of the devices show that controlling the thickness of the PANI hole transporting layer, both the maximum emission peak of the electroluminescence curves and the driving voltage could be tuned. Furthermore, an exponential behaviour has been demonstrated for the maximum intensity of the electroluminescence curves as a function of the applied excitation voltage between anode and cathode.

Influence of the thickness of electrochemically deposited polyaniline used as hole transporting layer on the behaviour of polymer light-emitting diodes

International Nuclear Information System (INIS)

Alonso, J.L.; Ferrer, J.C.; Cotarelo, M.A.; Montilla, F.; Fernandez de Avila, S.

2009-01-01

An experimental study about the influence of the thickness of electrochemically deposited polyaniline (PANI), used as hole-transporting layer, on the behaviour of polymer light emitting diodes is presented. Two sets of devices with a different conjugated polymer used as active layer were prepared. Poly(9-vinylcarbazole) was used for the first type of devices, whereas Poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene-vinylene] was used for the second type. Each set consists of five polymeric diodes in which the hole-transporting layer has been varied. In one case of each set no layer was deposited, in other one a Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) layer was deposited, and in the rest of the diodes a different thickness of electrochemically deposited PANI was employed. The optic and electronic characterization of the devices show that controlling the thickness of the PANI hole transporting layer, both the maximum emission peak of the electroluminescence curves and the driving voltage could be tuned. Furthermore, an exponential behaviour has been demonstrated for the maximum intensity of the electroluminescence curves as a function of the applied excitation voltage between anode and cathode

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

Energy Technology Data Exchange (ETDEWEB)

Qian, L., E-mail: qian_lei@126.com; Xu, Z.; Teng, F.; Duan, X.-X. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China); Jin, Z.-S.; Du, Z.-L. [Henan University, Key Laboratory on special functional materials (China); Li, F.-S.; Zheng, M.-J. [State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Peking University, Department of Physics (China); Wang, Y.-S. [Beijing Jiaotong University, Institute of Optoelectronic Technology (China)

2007-06-15

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

Enhanced Efficiency of Polymer Light-Emitting Diodes by Dispersing Dehydrated Nanotube Titanic Acid in the Hole-buffer Layer

Science.gov (United States)

Qian, L.; Xu, Z.; Teng, F.; Duan, X.-X.; Jin, Z.-S.; Du, Z.-L.; Li, F.-S.; Zheng, M.-J.; Wang, Y.-S.

2007-06-01

Efficiency of polymer light-emitting diodes (PLEDs) with poly(2-methoxy-5-(2-ethyl hexyloxy)- p-phenylene vinylene) (MEH-PPV) as an emitting layer was improved if a dehydrated nanotubed titanic acid (DNTA) doped hole-buffer layer polyethylene dioxythiophene (PEDOT) was used. Photoluminescence (PL) and Raman spectra indicated a stronger interaction between DNTA and sulfur atom in thiophene of PEDOT, which suppresses the chemical interaction between vinylene of MEH-PPV and thiophene of PEDOT. The interaction decreases the defect states in an interface region to result in enhancement in device efficiency, even though the hole transporting ability of PEDOT was decreased.

Formation of electrostatic double-layers and electron-holes in a low pressure mercury plasma column

International Nuclear Information System (INIS)

Petraconi, G; Maciel, Homero S

2003-01-01

Experimental studies of the formation of electrostatic double layers (DLs) and electron-holes (e-holes) are reported. The measurements were performed in the positive column of a mercury arc discharge operating in the low-pressure range of (2.0-14.0) x 10 -2 Pa with current density in the range of (3.0-8.0) x 10 3 A m -2 . Stable and unstable modes of the discharge were identified as the current was gradually increased, keeping constant the vapour pressure. The discharge remains stable until a critical current from which a slight increase of the current leads to an unstable regime characterized by high discharge impedance and strong oscillations. This mode ceased after a DL was formed in the plasma column. To induce the DL formation and to transport it smoothly along the discharge column, a low intensity B-field (7-10) x 10 -3 T produced by a movable single coil was used. The B-field locally increases the electron current density and makes the DL form at the centre of the magnetic constriction where it remained at rest. Electrostatic potential structures compatible with ordinary DLs and multiple-layers could be formed in the plasma column by dealing with the combined effects of the operational parameters of the discharge. It is noticeable that a pure e-hole, which is a symmetric triple-layer having a bell shape potential profile, could easily be formed by means of this experimental technique. A partial kinetic description, based on the space charge structure derived from an experimental e-hole, is presented in order to infer the charged particle populations that could contribute to the space charge of the e-hole. Evidence is shown that strong e-hole formation might be driven by an ion beam, therefore it could not be formed in isolation since its formation requires a nearby ion accelerating potential structure. Probe measurements of the plasma properties, at various radial positions of the stable positive column, are also presented. In the stable mode, prior to

Selections from 2016: Primordial Black Holes as Dark Matter

Science.gov (United States)

Kohler, Susanna

2016-12-01

Editors note:In these last two weeks of 2016, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.LIGO Gravitational Wave Detection, Primordial Black Holes, and the Near-IR Cosmic Infrared Background AnisotropiesPublished May2016Main takeaway:A study by Alexander Kashlinsky (NASA Goddard SFC) proposes that the cold dark matter that makes up the majority of the universes matter may be made of black holes. These black holes, Kashlinsky suggests, are primordial: they collapsed directly from dense regions of the universe soon after the Big Bang.Why its interesting:This model would simultaneously explain several observations. In particular, we see similarities in patterns between the cosmic infrared and X-ray backgrounds. This would make sense if accretion onto primordial black holes in halos produced the X-ray background in the same regions where the first stars also formed, producing the infrared background.What this means for current events:In Kashlinskys model, primordial black holes would occasionally form binary pairs and eventually spiral in and merge. The release of energy from such an event would then be observable by gravitational-wave detectors. Could the gravitational-wave signal that LIGO detected last year have been two primordial black holes merging? More observations will be needed to find out.CitationA. Kashlinsky 2016 ApJL 823 L25. doi:10.3847/2041-8205/823/2/L25

Layered bismuth selenide utilized as hole transporting layer for highly stable organic photovoltaics

KAUST Repository

Yuan, Zhongcheng

2015-11-01

Abstract Layered bismuth selenide (L-Bi2Se3) nanoplates were implemented as hole transporting layers (HTLs) for inverted organic solar cells. Device based on L-Bi2Se3 showed increasing power conversion efficiency (PCE) during ambient condition storage process. A PCE of 4.37% was finally obtained after 5 days storage, which outperformed the ones with evaporated-MoO3 using poly(3-hexylthiophene) (P3HT) as donor material and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as acceptor. The improved device efficiency can be attributed to the high conductivity and increasing work function of L-Bi2Se3. The work function of L-Bi2Se3 increased with the storage time in ambient condition due to the oxygen atom doping. Ultraviolet photoelectron spectroscopy and high resolution X-ray photoelectron spectroscopy were conducted to verify the increased work function, which originated from the p-type doping process. The device based on L-Bi2Se3 exhibited excellent stability in ambient condition up to 4 months, which was much improved compared to the device based on traditional HTLs. © 2015 Elsevier B.V.

Enhancing carrier injection in the active region of a 280nm emission wavelength LED using graded hole and electron blocking layers

KAUST Repository

Janjua, Bilal; Ng, Tien Khee; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

2014-01-01

A theoretical investigation of AlGaN UV-LED with band engineering of hole and electron blocking layers (HBL and EBL, respectively) was conducted with an aim to improve injection efficiency and reduce efficiency droop in the UV LEDs. The analysis is based on energy band diagrams, carrier distribution and recombination rates (Shockley-Reed-Hall, Auger, and radiative recombination rates) in the quantum well, under equilibrium and forward bias conditions. Electron blocking layer is based on AlaGa1-aN / Al b → cGa1-b → 1-cN / AldGa 1-dN, where a < d < b < c. A graded layer sandwiched between large bandgap AlGaN materials was found to be effective in simultaneously blocking electrons and providing polarization field enhanced carrier injection. The graded interlayer reduces polarization induced band bending and mitigates the related drawback of impediment of holes injection. Similarly on the n-side, the Alx → yGa1-x → 1-yN / AlzGa 1-zN (x < z < y) barrier acts as a hole blocking layer. The reduced carrier leakage and enhanced carrier density in the active region results in significant improvement in radiative recombination rate compared to a structure with the conventional rectangular EBL layers. The improvement in device performance comes from meticulously designing the hole and electron blocking layers to increase carrier injection efficiency. The quantum well based UV-LED was designed to emit at 280nm, which is an effective wavelength for water disinfection application.

Enhancing carrier injection in the active region of a 280nm emission wavelength LED using graded hole and electron blocking layers

KAUST Repository

Janjua, Bilal

2014-02-27

A theoretical investigation of AlGaN UV-LED with band engineering of hole and electron blocking layers (HBL and EBL, respectively) was conducted with an aim to improve injection efficiency and reduce efficiency droop in the UV LEDs. The analysis is based on energy band diagrams, carrier distribution and recombination rates (Shockley-Reed-Hall, Auger, and radiative recombination rates) in the quantum well, under equilibrium and forward bias conditions. Electron blocking layer is based on AlaGa1-aN / Al b → cGa1-b → 1-cN / AldGa 1-dN, where a < d < b < c. A graded layer sandwiched between large bandgap AlGaN materials was found to be effective in simultaneously blocking electrons and providing polarization field enhanced carrier injection. The graded interlayer reduces polarization induced band bending and mitigates the related drawback of impediment of holes injection. Similarly on the n-side, the Alx → yGa1-x → 1-yN / AlzGa 1-zN (x < z < y) barrier acts as a hole blocking layer. The reduced carrier leakage and enhanced carrier density in the active region results in significant improvement in radiative recombination rate compared to a structure with the conventional rectangular EBL layers. The improvement in device performance comes from meticulously designing the hole and electron blocking layers to increase carrier injection efficiency. The quantum well based UV-LED was designed to emit at 280nm, which is an effective wavelength for water disinfection application.

Enhancing Photovoltaic Performance of Inverted Planar Perovskite Solar Cells by Cobalt-Doped Nickel Oxide Hole Transport Layer.

Science.gov (United States)

Xie, Yulin; Lu, Kai; Duan, Jiashun; Jiang, Youyu; Hu, Lin; Liu, Tiefeng; Zhou, Yinhua; Hu, Bin

2018-04-25

Electron and hole transport layers have critical impacts on the overall performance of perovskite solar cells (PSCs). Herein, for the first time, a solution-processed cobalt (Co)-doped NiO X film was fabricated as the hole transport layer in inverted planar PSCs, and the solar cells exhibit 18.6% power conversion efficiency. It has been found that an appropriate Co-doping can significantly adjust the work function and enhance electrical conductivity of the NiO X film. Capacitance-voltage ( C- V) spectra and time-resolved photoluminescence spectra indicate clearly that the charge accumulation becomes more pronounced in the Co-doped NiO X -based photovoltaic devices; it, as a consequence, prevents the nonradiative recombination at the interface between the Co-doped NiO X and the photoactive perovskite layers. Moreover, field-dependent photoluminescence measurements indicate that Co-doped NiO X -based devices can also effectively inhibit the radiative recombination process in the perovskite layer and finally facilitate the generation of photocurrent. Our work indicates that Co-doped NiO X film is an excellent candidate for high-performance inverted planar PSCs.

Significant performance enhancement of inverted organic light-emitting diodes by using ZnIx as a hole-blocking layer

Science.gov (United States)

Cheng, Chuan-Hui; Zhang, Bi-Long; Sun, Chao; Li, Ruo-Xuan; Wang, Yuan; Tian, Wen-Ming; Zhao, Chun-Yi; Jin, Sheng-Ye; Liu, Wei-Feng; Luo, Ying-Min; Du, Guo-Tong; Cong, Shu-Lin

2017-06-01

A highly efficient inverted organic light emitting diode using 1.0 nm-thick ZnIx as a hole-blocking layer is developed. We fabricate devices with the configuration ITO/ZnIx (1.0 nm)/Alq3 (50 nm)/NPB (50 nm)/MoO3 (6.0 nm)/Al (100 nm). The deposition of a ZnIx layer increases the maximum luminance by two orders of magnitude from 13.4 to 3566.1 cd/m2. In addition, the maximum current efficiency and power efficiency are increased by three orders of magnitude, and the turn-on voltage to reach 1 cd/m2 decreases from 13 to 8 V. The results suggest that the electron injection efficiency is not improved by introducing a ZnIx layer. Instead, the improved device performance originates from the strong hole-blocking ability of ZnIx. This work indicates that layered materials may lead to novel applications in optoelectronic devices.

Numerical analysis of drilling hole work-hardening effects in hole-drilling residual stress measurement

Science.gov (United States)

Li, H.; Liu, Y. H.

2008-11-01

The hole-drilling strain gage method is an effective semi-destructive technique for determining residual stresses in the component. As a mechanical technique, a work-hardening layer will be formed on the surface of the hole after drilling, and affect the strain relaxation. By increasing Young's modulus of the material near the hole, the work-hardening layer is simplified as a heterogeneous annulus. As an example, two finite rectangular plates submitted to different initial stresses are treated, and the relieved strains are measured by finite element simulation. The accuracy of the measurement is estimated by comparing the simulated residual stresses with the given initial ones. The results are shown for various hardness of work-hardening layer. The influence of the relative position of the gages compared with the thickness of the work-hardening layer, and the effect of the ratio of hole diameter to work-hardening layer thickness are analyzed as well.

Brittleness and Packing Density Effects on Blast-hole Cuttings Yield of Selected Rocks

Directory of Open Access Journals (Sweden)

B. Adebayo

2016-06-01

Full Text Available This paper evaluates brittleness and packing density to analysis their effects on blast-hole cutting yield for three selected rocks in Nigeria. Brittleness test (S20 was carried out in accordance with Norwegian Soil and Rock Engineering and the Brittleness Index (BI for the selected rocks were estimated. The packing density determined from the photomicrograph of the rock samples. The grain size of 45 blast-holes drill cuttings collected from three selected while drilling of these rocks were determined using standard method of America Society for Testing and Materials (ASTM D 2487. The brittleness values are 50%, 44% and 42% for micro granite, porphyritic granite and medium biotite granite respectively. The result of BI varied from 10.32 – 11.59 and they are rated as moderately brittle rocks. The values of packing density varied from 92.20 – 94.55%, 91.00 -92.96% and 92.92 – 94.96% for all the rocks. The maximum weights of blast-hole particle size retained at 75 µm are 106.00g, 103.28 g and 99.76 g for medium biotite granite, micro granite and porhyritic granite respectively. Packing density values have correlation to some extent with (S20 values hence, this influence the yield of blast-hole cuttings as drilling progresses. The minimum weight of blast-hole cuttings particle size retained at 150 µm agrees with brittleness index classification for micro granite.

Molecular Doping of the Hole-Transporting Layer for Efficient, Single-Step Deposited Colloidal Quantum Dot Photovoltaics

KAUST Repository

Kirmani, Ahmad R.; Garcia de Arquer, F. Pelayo; Fan, James Z.; Khan, Jafar Iqbal; Walters, Grant; Hoogland, Sjoerd; Wehbe, Nimer; Said, Marcel M.; Barlow, Stephen; Laquai, Fré dé ric; Marder, Seth R.; Sargent, Edward H.; Amassian, Aram

2017-01-01

solar cells. These promising architectures employ a QD hole-transporting layer (HTL) whose intrinsically shallow Fermi level (EF) restricts band-bending at maximum power-point during solar cell operation limiting charge collection. Here, we demonstrate a

Blue and white phosphorescent organic light emitting diode performance improvement by confining electrons and holes inside double emitting layers

Energy Technology Data Exchange (ETDEWEB)

Tsai, Yu-Sheng; Hong, Lin-Ann; Juang, Fuh-Shyang; Chen, Cheng-Yin

2014-09-15

In this research, complex emitting layers (EML) were fabricated using TCTA doping hole-transport material in the front half of a bipolar 26DCzPPy as well as PPT doping electron-transport material in the back half of 26DCzPPy. Blue dopant FIrpic was also mixed inside the complex emitting layer to produce a highly efficient blue phosphorescent organic light emitting diode (OLED). The hole and electron injection and carrier recombination rate were effectively increased. The fabricated complex emitting layers exhibited current efficiency of 42 cd/A and power efficiency of 30 lm/W when the luminance was 1000 cd/m{sup 2}, driving voltage was 4.4 V, and current density was 2.4 mA/cm{sup 2}. A white OLED component was then manufactured by doping red dopant [Os(bpftz){sub 2}(PPh{sub 2}Me){sub 2}] (Os) in proper locations. When the Os dopant was doped in between the complex emitting layers, excitons were effectively confined within, increasing the recombination rate and therefore reducing the color shift. The resulting Commission Internationale de L’Eclairage (CIE) coordinates shifted from 4 to 10 V is (Δx=−0.04, Δy=+0.01). The component had a current efficiency of 35.7 cd/A, a power efficiency of 24 lm/W, driving voltage of 4.6 V and a CIE{sub x,y} of (0.31,0.35) at a luminance of 1000 cd/m{sup 2}, with a maximum luminance of 15,600 cd/m{sup 2} at 10 V. Attaching an outcoupling enhancement film was applied to increase the luminance efficiency to 30 lm/W. - Highlights: • Used the complex double emitting layers. • Respectively doped hole and electron transport material in the bipolar host. • Electrons and holes are effectively confined within EMLs to produce excitons.

Blue and white phosphorescent organic light emitting diode performance improvement by confining electrons and holes inside double emitting layers

International Nuclear Information System (INIS)

Tsai, Yu-Sheng; Hong, Lin-Ann; Juang, Fuh-Shyang; Chen, Cheng-Yin

2014-01-01

In this research, complex emitting layers (EML) were fabricated using TCTA doping hole-transport material in the front half of a bipolar 26DCzPPy as well as PPT doping electron-transport material in the back half of 26DCzPPy. Blue dopant FIrpic was also mixed inside the complex emitting layer to produce a highly efficient blue phosphorescent organic light emitting diode (OLED). The hole and electron injection and carrier recombination rate were effectively increased. The fabricated complex emitting layers exhibited current efficiency of 42 cd/A and power efficiency of 30 lm/W when the luminance was 1000 cd/m 2 , driving voltage was 4.4 V, and current density was 2.4 mA/cm 2 . A white OLED component was then manufactured by doping red dopant [Os(bpftz) 2 (PPh 2 Me) 2 ] (Os) in proper locations. When the Os dopant was doped in between the complex emitting layers, excitons were effectively confined within, increasing the recombination rate and therefore reducing the color shift. The resulting Commission Internationale de L’Eclairage (CIE) coordinates shifted from 4 to 10 V is (Δx=−0.04, Δy=+0.01). The component had a current efficiency of 35.7 cd/A, a power efficiency of 24 lm/W, driving voltage of 4.6 V and a CIE x,y of (0.31,0.35) at a luminance of 1000 cd/m 2 , with a maximum luminance of 15,600 cd/m 2 at 10 V. Attaching an outcoupling enhancement film was applied to increase the luminance efficiency to 30 lm/W. - Highlights: • Used the complex double emitting layers. • Respectively doped hole and electron transport material in the bipolar host. • Electrons and holes are effectively confined within EMLs to produce excitons

Effects of Au nanoparticle addition to hole transfer layer in organic solar cells based on copper naphthalocyanine and fullerene

Institute of Scientific and Technical Information of China (English)

Akihiko Nagata; Takeo Okun; Tsuyoshi Akiyaman; Atsushi Suzuki

2014-01-01

Organic solar cells based on copper naphthalocyanine (CuNc) and fullerene (C60) were fabricated, and their photovoltaic properties were investigated. C60 and CuNc were used as n-type and p-type semiconductors, respectively. In addition, the effect of Au nanoparticle addition on a hole transfer layer was investigated, and the power conversion efficiency of the devices was improved after blending the Au nanoparticles into the hole transport layer. Nanostructures of Au nanoparticles were investigated by transmission electron microscopy and X-ray diffraction. Energy levels of molecules were calculated by molecular orbital calculations, and the nanostructure and electronic properties were discussed.

Towards printed perovskite solar cells with cuprous oxide hole transporting layers

DEFF Research Database (Denmark)

Wang, Yan; Xia, Zhonggao; Liang, Jun

2015-01-01

Solution-processed p-type metal oxide materials have shown great promise in improving the stability of perovskite-based solar cells and offering the feasibility for a low cost printing fabrication process. Herein, we performed a device modeling study on planar perovskite solar cells with cuprous...... oxide (Cu2O) hole transporting layers (HTLs) by using a solar cell simulation program, wxAMPS. The performance of a Cu2O/perovskite solar cell was correlated to the material properties of the Cu2O HTL, such as thickness, carrier mobility, mid-gap defect, and doping...

Fabrication and characterization of organic light-emitting diodes using zinc complexes as hole-blocking layer.

Science.gov (United States)

Kim, Won Sam; You, Jung Min; Lee, Burm-Jong; Jang, Yoon-Ki; Kim, Dong-Eun; Kwon, Young-Soo

2006-11-01

2-(2-Hydroxyphenyl)benzoxazole (HPB) was employed as organic ligand and the corresponding zinc complexes (Zn(HPB)2 and Zn(HPB)q) were synthesized. And their EL properties were characterized. The structures of zinc complexes were determined with FT-NMR, FT-IR, UV-Vis, and XPS. The thermal stability showed up to about 300 degrees C under nitrogen flow, which was measured by TGA. The photoluminescence (PL) of zinc complexes were measured from the DMF solution. The PL emitted in blue and yellow region, respectively. The EL devices were fabricated by the vacuum deposition. Two kinds of OLEDs devices were fabricated; ITO/NPB (40 nm)/Zn complexes (60 nm)/LiF/Al and ITO/NPB (40 nm)/Alq3 (60 nm)/Zn complexes (5 nm)/LiF/Al. Both of the EL properties as the emitting and the hole-blocking layer were investigated. The EL emission of Zn(HPB)q exhibited green light centered at 532 nm. The device showed a turn-on voltage at 5 V and a luminance of 6073 cd/m2 at 10 V. Meanwhile, the maximum EL the emission of the Zn(HPB)2 device was found to be at 447 nm. And the device showed a luminance of 2813 cd/m2 at 10 V. The ITO/NPB (40 nm)/Alq3 (60 nm)/Zn(HPB)2 (5 nm)/LiF/Al device showed increased luminance of L=17000 cd/m2 compared to L=12000 cd/m2 for similar device fabricated without the hole-blocking layer. And the turn-on voltage was significantly affected by the existence of the hole-blocking layer.

Electrically conductive polyaniline as hole-injection layer for MEH-PPV:BT based polymer light emitting diodes

International Nuclear Information System (INIS)

Mohsennia, M.; Bidgoli, M. Massah; Boroumand, F. Akbari; Nia, A. Mohsen

2015-01-01

Graphical abstract: The PANI prepared at 15 °C with higher electrical conductivity has been used as hole-injection layer (HIL) in polymer light emitting diodes (PLEDs) with structure of ITO/PANI/MEHPPV:BT/Al. - Highlights: • Polyaniline (PANI) was synthesized at different temperatures (5, 10, 15, 20 and 25 °C). • The PANI sample with higher electrical conductivity was used as HIL in the PLED devices. • The PANI injection layer yielded higher current and lower turn-on voltage. • The effect of MEH-PPV:BT weight ratio on the PLED performance has been also investigated. • The J–V characteristics of the devices have been explained by FN tunneling model. - Abstract: Polyaniline (PANI) was synthesized by oxidative polymerization of aniline at different temperatures (5, 10, 15, 20 and 25 °C). The influence of polymerization temperature on sheet resistance of PANI was investigated, and the one prepared at 15 °C which showed lowest resistivity was chosen for further analysis. PANI was subsequently used as hole-injection layer (HIL) in polymer light emitting diodes (PLEDs) with structure of poly(ethylene terephthalate) (PET)/indium tin oxide (ITO)/PANI/MEH-PPV:BT/aluminum (Al). The PLEDs with emission layer made from a blend of poly [2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and an electron transporting material, benzothiadiazole (BT), were fabricated at room conditions without using glove boxes. Our results showed an improvement in performance of our PANI-based fabricated PLEDs (PET/ITO/PANI/MEH-PPV:BT/Al) compared to the conventional devices that use poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PET/ITO/PEDOT:PSS/MEH-PPV:BT/Al) as their HIL. The hole injection barrier height (φ) of the fabricated PLEDs were then estimated using the Fowler–Nordheim (FN) field-emission tunneling theory and revealed that the barrier height decreases by increasing the BT concentration in the MEH-PPV:BT blend layer

Improved fill factor in inverted planar perovskite solar cells with zirconium acetate as the hole-and-ion-blocking layer.

Science.gov (United States)

Zhang, Xuewen; Liang, Chunjun; Sun, Mengjie; Zhang, Huimin; Ji, Chao; Guo, Zebang; Xu, Yajun; Sun, Fulin; Song, Qi; He, Zhiqun

2018-03-14

Planar perovskite solar cells (PSCs) have gained great interest due to their low-temperature solution preparation and simple process. In inverted planar PSCs, an additional buffer layer is usually needed on the top of the PCBM electron-transport layer (ETL) to enhance the device performance. In this work, we used a new buffer layer, zirconium acetate (Zr(Ac) 4 ). The inclusion of the Zr(Ac) 4 buffer layer leads to the increase of FF from ∼68% to ∼79% and PCE from ∼14% to ∼17% in the planar PSCs. The UPS measurement indicates that the Zr(Ac) 4 layer has a low HOMO level of -8.2 eV, indicating that the buffer layer can act as a hole-blocking layer. Surface morphology and surface chemistry investigations reveal that the elements I, MA and Pb can diffuse across the PCBM ETL, damaging the device performance. The covering Zr(Ac) 4 molecules fill in the pinholes of the PCBM layer and effectively block the ions/molecules of the perovskite from diffusion across the ETL. The resulting more robust PCBM/Zr(Ac) 4 ETL leads to weaker ionic charge accumulation and lower diode leakage current. The double role of hole-and-ion blocking of the Zr(Ac) 4 layer explains the improved FF and PCE in the PSCs.

Evolution of magnetohydrodynamic waves in low layers of a coronal hole

International Nuclear Information System (INIS)

Pucci, Francesco; Malara, Francesco; Onofri, Marco

2014-01-01

Although a coronal hole is permeated by a magnetic field with a dominant polarity, magnetograms reveal a more complex magnetic structure in the lowest layers, where several regions of opposite polarity of typical size of the order of 10 4 km are present. This can give rise to magnetic separatrices and neutral lines. MHD fluctuations generated at the base of the coronal hole by motions of the inner layer of the solar atmosphere may interact with such inhomogeneities, leading to the formation of small scales. This phenomenon is studied on a 2D model of a magnetic structure with an X-point, using 2D MHD numerical simulations. This model implements a method of characteristics for boundary conditions in the direction outer-pointing to Sun surface to simulate both wave injection and exit without reflection. Both Alfvénic and magnetosonic perturbations are considered, and they show very different phenomenology. In the former case, an anisotropic power-law spectrum forms with a dominance of perpendicular wavevectors at altitudes ∼10 4 km. Density fluctuations are generated near the X-point by Alfvén wave magnetic pressure and propagate along open fieldlines at a speed comparable to the local Alfvén velocity. An analysis of energy dissipation and heating caused by the formation of small scales for the Alfvénic case is presented. In the magnetosonic case, small scales form only around the X-point, where a phenomenon of oscillating magnetic reconnection is observed to be induced by the periodic deformation of the magnetic structure due to incoming waves.

Efficient organic solar cells using copper(I) iodide (CuI) hole transport layers

Energy Technology Data Exchange (ETDEWEB)

Peng, Ying [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China); Department of Physics and Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, London SW7 2AZ (United Kingdom); Yaacobi-Gross, Nir; Perumal, Ajay K.; Faber, Hendrik A.; Bradley, Donal D. C.; Anthopoulos, Thomas D., E-mail: zhqhe@bjtu.edu.cn, E-mail: t.anthopoulos@imperial.ac.uk [Department of Physics and Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, London SW7 2AZ (United Kingdom); Vourlias, George; Patsalas, Panos A. [Department of Physics, Laboratory of Applied Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); He, Zhiqun, E-mail: zhqhe@bjtu.edu.cn, E-mail: t.anthopoulos@imperial.ac.uk [Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044 (China)

2015-06-15

We report the fabrication of high power conversion efficiency (PCE) polymer/fullerene bulk heterojunction (BHJ) photovoltaic cells using solution-processed Copper (I) Iodide (CuI) as hole transport layer (HTL). Our devices exhibit a PCE value of ∼5.5% which is equivalent to that obtained for control devices based on the commonly used conductive polymer poly(3,4-ethylenedioxythiophene): polystyrenesulfonate as HTL. Inverted cells with PCE >3% were also demonstrated using solution-processed metal oxide electron transport layers, with a CuI HTL evaporated on top of the BHJ. The high optical transparency and suitable energetics of CuI make it attractive for application in a range of inexpensive large-area optoelectronic devices.

Efficient organic solar cells using copper(I) iodide (CuI) hole transport layers

International Nuclear Information System (INIS)

Peng, Ying; Yaacobi-Gross, Nir; Perumal, Ajay K.; Faber, Hendrik A.; Bradley, Donal D. C.; Anthopoulos, Thomas D.; Vourlias, George; Patsalas, Panos A.; He, Zhiqun

2015-01-01

We report the fabrication of high power conversion efficiency (PCE) polymer/fullerene bulk heterojunction (BHJ) photovoltaic cells using solution-processed Copper (I) Iodide (CuI) as hole transport layer (HTL). Our devices exhibit a PCE value of ∼5.5% which is equivalent to that obtained for control devices based on the commonly used conductive polymer poly(3,4-ethylenedioxythiophene): polystyrenesulfonate as HTL. Inverted cells with PCE >3% were also demonstrated using solution-processed metal oxide electron transport layers, with a CuI HTL evaporated on top of the BHJ. The high optical transparency and suitable energetics of CuI make it attractive for application in a range of inexpensive large-area optoelectronic devices

Enhancing Color Purity and Stable Efficiency of White Organic Light Diodes by Using Hole-Blocking Layer

Directory of Open Access Journals (Sweden)

Chien-Jung Huang

2014-01-01

Full Text Available The organic light-emitting diodes with triple hole-blocking layer (THBL formation sandwich structure which generate white emission were fabricated. The 5,6,11,12-tetraphenylnapthacene (Rubrene, (4,4′-N,N′-dicarbazolebiphenyl (CBP, and 4,4′-bis(2,2′diphenylvinil-1,1′-biphenyl (DPVBi were used as emitting materials in the device. The function of CBP layer is not only an emitting layer but also a hole-blocking layer (HBL, and the Rubrene was doped into the CBP. The optimal configuration structure was indium tin oxide (ITO/Molybdenum trioxide (MoO3 (5 nm/[4,4-bis[N-(1-naphthyl-N-phenylamino]biphenyl (NPB (35 nm/CBP (HBL1 (5 nm/DPVBi (I (10 nm/CBP (HBL2 : Rubrene (4 : 1 (3 nm/DPVBi (II (30 nm/CBP (HBL3 (2 nm/4,7-diphenyl-1,10-phenanthroline (BPhen (10 nm/Lithium fluoride (LiF/aluminum (Al. The result showed that the device with Rubrene doped in CBP (HBL2 exhibited a stable white emission with the color coordinates of (0.322, 0.368, and the coordinate with the slight shift of ±Δx,y = (0.001, 0.011 for applied voltage of 8–12 V was observed.

Inverted polymer solar cells with Nafion® as the hole extraction layer: efficiency and lifetime studies

Science.gov (United States)

Manceau, Matthieu; Berson, Solenn

2014-01-01

The use of Nafion® as the hole extraction layer in polymer solar cells is demonstrated in this work. Inverted devices were built on plastic foil with the following architecture: PET/ITO/ZnO/P3HT:PCBM/Nafion®/Ag. The Nafion® was processed from a surfactant-free solution in alcoholic solvents on top of the active layer. Optimization of film thickness and annealing yielded fully functional devices with power conversion efficiency similar to others referenced, along with good operational stability.

On the hole accelerator for III-nitride light-emitting diodes

International Nuclear Information System (INIS)

Zhang, Zi-Hui; Zhang, Yonghui; Bi, Wengang; Geng, Chong; Xu, Shu; Demir, Hilmi Volkan; Sun, Xiao Wei

2016-01-01

In this work, we systematically conduct parametric studies revealing the sensitivity of the hole injection on the hole accelerator (a hole accelerator is made of the polarization mismatched p-electron blocking layer (EBL)/p-GaN/p-Al x Ga 1−x N heterojunction) with different designs, including the AlN composition in the p-Al x Ga 1−x N layer, and the thickness for the p-GaN layer and the p-Al x Ga 1−x N layer. According to our findings, the energy that the holes obtain does not monotonically increase as the AlN incorporation in the p-Al x Ga 1−x N layer increases. Meanwhile, with p-GaN layer or p-Al x Ga 1−x N layer thickening, the energy that the holes gain increases and then reaches a saturation level. Thus, the hole injection efficiency and the device efficiency are very sensitive to the p-EBL/p-GaN/p-Al x Ga 1−x N design, and the hole accelerator can effectively increase the hole injection if properly designed.

Improved Efficiency of Polymer Solar Cells by means of Coating Hole Transporting Layer as Double Layer Deposition

Science.gov (United States)

Chonsut, T.; Kayunkid, N.; Rahong, S.; Rangkasikorn, A.; Wirunchit, S.; Kaewprajak, A.; Kumnorkaew, P.; Nukeaw, J.

2017-09-01

Polymer solar cells is one of the promising technologies that gain tremendous attentions in the field of renewable energy. Optimization of thickness for each layer is an important factor determining the efficiency of the solar cells. In this work, the optimum thickness of Poly(3,4-ethylenedioxythione): poly(styrenesulfonate) (PEDOT:PSS), a famous polymer widely used as hole transporting layer in polymer solar cells, is determined through the analyzing of device’s photovoltaic parameters, e.g. short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) as well as power conversion efficiency (PCE). The solar cells were prepared with multilayer of ITO/PEDOT:PSS/PCDTBT:PC70BM/TiOx/Al by rapid convective deposition. In such preparation technique, the thickness of the thin film is controlled by the deposition speed. The faster deposition speed is used, the thicker film is obtained. Furthermore, double layer deposition of PEDOT:PSS was introduced as an approach to improve solar cell efficiency. The results obviously reveal that, with the increase of PEDOT:PSS thickness, the increments of Jsc and FF play the important role to improve PCE from 3.21% to 4.03%. Interestingly, using double layer deposition of PEDOT:PSS shows the ability to enhance the performance of the solar cells to 6.12% under simulated AM 1.5G illumination of 100 mW/cm2.

Black-hole ringdown search in TAMA300: matched filtering and event selections

International Nuclear Information System (INIS)

Tsunesada, Yoshiki; Kanda, Nobuyuki; Nakano, Hiroyuki; Tatsumi, Daisuke

2005-01-01

Detecting gravitational ringdown waves provides a probe for direct observation of astrophysical black holes. The masses and angular momenta of black holes can be determined from the waveforms by using the black-hole perturbation theory. In this paper we present data analysis methods to search for black-hole ringdowns of fundamental quasi-normal modes with interferometric gravitational wave detectors, and report an application to the TAMA300 data. Our method is based upon matched filtering by which we calculate cross-correlations between detector outputs and reference waveforms. In a search for gravitational signals, fake reductions and event identifications are of most importance. We developed two methods to reject spurious triggers in filter outputs in the time domain and examined their reduction powers. It is shown that by using the methods presented here the number of fake triggers can be reduced by an order with a false dismissal probability of 5%. We also discuss the possibility of using the higher order quasi-normal modes for event selection

Selective layer disordering in III-nitrides with a capping layer

Science.gov (United States)

Wierer, Jr., Jonathan J.; Allerman, Andrew A.

2016-06-14

Selective layer disordering in a doped III-nitride superlattice can be achieved by depositing a dielectric capping layer on a portion of the surface of the superlattice and annealing the superlattice to induce disorder of the layer interfaces under the uncapped portion and suppress disorder of the interfaces under the capped portion. The method can be used to create devices, such as optical waveguides, light-emitting diodes, photodetectors, solar cells, modulators, laser, and amplifiers.

Enhancement of hole-injection and power efficiency of organic light emitting devices using an ultra-thin ZnO buffer layer

International Nuclear Information System (INIS)

Huang, H.-H.; Chu, S.-Y.; Kao, P.-C.; Chen, Y.-C.; Yang, M.-R.; Tseng, Z.-L.

2009-01-01

The advantages of using an anode buffer layer of ZnO on the electro-optical properties of organic light emitting devices (OLEDs) are reported. ZnO powders were thermal-evaporated and then treated with ultra-violet (UV) ozone exposure to make the ZnO layers. The turn-on voltage of OLEDs decreased from 4 V (4.2 cd/m 2 ) to 3 V (3.4 cd/m 2 ) and the power efficiency increased from 2.7 lm/W to 4.7 lm/W when a 1-nm-thick ZnO layer was inserted between indium tin oxide (ITO) anodes and α-naphthylphenylbiphenyl diamine (NPB) hole-transporting layers. X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS) results revealed the formation of the ZnO layer and showed that the work function increased by 0.59 eV when the ZnO/ITO layer was treated by UV-ozone for 20 min. The surface of the ZnO/ITO film became smoother than that of bare ITO film after the UV-ozone treatment. Thus, the hole-injection energy barrier was lowered by inserting an ZnO buffer layer, resulting in a decrease of the turn-on voltage and an increase of the power efficiency of OLEDs.

Semiconducting Polymer Photodetectors with Electron and Hole Blocking Layers: High Detectivity in the Near-Infrared

Directory of Open Access Journals (Sweden)

Xiong Gong

2010-07-01

Full Text Available Sensing from the ultraviolet-visible to the infrared is critical for a variety of industrial and scientific applications. Photodetectors with broad spectral response, from 300 nm to 1,100 nm, were fabricated using a narrow-band gap semiconducting polymer blended with a fullerene derivative. By using both an electron-blocking layer and a hole-blocking layer, the polymer photodetectors, operating at room temperature, exhibited calculated detectivities greater than 1013 cm Hz1/2/W over entire spectral range with linear dynamic range approximately 130 dB. The performance is comparable to or even better than Si photodetectors.

A hole modulator for InGaN/GaN light-emitting diodes

Science.gov (United States)

Zhang, Zi-Hui; Kyaw, Zabu; Liu, Wei; Ji, Yun; Wang, Liancheng; Tan, Swee Tiam; Sun, Xiao Wei; Demir, Hilmi Volkan

2015-02-01

The low p-type doping efficiency of the p-GaN layer has severely limited the performance of InGaN/GaN light-emitting diodes (LEDs) due to the ineffective hole injection into the InGaN/GaN multiple quantum well (MQW) active region. The essence of improving the hole injection efficiency is to increase the hole concentration in the p-GaN layer. Therefore, in this work, we have proposed a hole modulator and studied it both theoretically and experimentally. In the hole modulator, the holes in a remote p-type doped layer are depleted by the built-in electric field and stored in the p-GaN layer. By this means, the overall hole concentration in the p-GaN layer can be enhanced. Furthermore, the hole modulator is adopted in the InGaN/GaN LEDs, which reduces the effective valance band barrier height for the p-type electron blocking layer from ˜332 meV to ˜294 meV at 80 A/cm2 and demonstrates an improved optical performance, thanks to the increased hole concentration in the p-GaN layer and thus the improved hole injection into the MQWs.

Selective detection of antibodies in microstructured polymer optical fibers

DEFF Research Database (Denmark)

Jensen, Jesper Bo Damm; Hoiby, P.E.; Emiliyanov, Grigoriy Andreev

2005-01-01

was applied to selectively capture either α-streptavidin or α-CRP antibodies inside these air holes. A sensitive and easy-to-use fluorescence method was used for the optical detection. Our results show that mPOF based biosensors can provide reliable and selective antibody detection in ultra small sample......We demonstrate selective detection of fluorophore labeled antibodies from minute samples probed by a sensor layer of complementary biomolecules immobilized inside the air holes of microstructured Polymer Optical Fiber (mPOF). The fiber core is defined by a ring of 6 air holes and a simple procedure...

Coevolution of Cooperation and Layer Selection Strategy in Multiplex Networks

Directory of Open Access Journals (Sweden)

Katsuki Hayashi

2016-11-01

Full Text Available Recently, the emergent dynamics in multiplex networks, composed of layers of multiple networks, has been discussed extensively in network sciences. However, little is still known about whether and how the evolution of strategy for selecting a layer to participate in can contribute to the emergence of cooperative behaviors in multiplex networks of social interactions. To investigate these issues, we constructed a coevolutionary model of cooperation and layer selection strategies in which each an individual selects one layer from multiple layers of social networks and plays the Prisoner’s Dilemma with neighbors in the selected layer. We found that the proportion of cooperative strategies increased with increasing the number of layers regardless of the degree of dilemma, and this increase occurred due to a cyclic coevolution process of game strategies and layer selection strategies. We also showed that the heterogeneity of links among layers is a key factor for multiplex networks to facilitate the evolution of cooperation, and such positive effects on cooperation were observed regardless of the difference in the stochastic properties of network topologies.

Gradient SiNO anti-reflective layers in solar selective coatings

Science.gov (United States)

Ren, Zhifeng; Cao, Feng; Sun, Tianyi; Chen, Gang

2017-08-01

A solar selective coating includes a substrate, a cermet layer having nanoparticles therein deposited on the substrate, and an anti-reflection layer deposited on the cermet layer. The cermet layer and the anti-reflection layer may each be formed of intermediate layers. A method for constructing a solar-selective coating is disclosed and includes preparing a substrate, depositing a cermet layer on the substrate, and depositing an anti-reflection layer on the cermet layer.

Methods for producing thin film charge selective transport layers

Science.gov (United States)

Hammond, Scott Ryan; Olson, Dana C.; van Hest, Marinus Franciscus Antonius Maria

2018-01-02

Methods for producing thin film charge selective transport layers are provided. In one embodiment, a method for forming a thin film charge selective transport layer comprises: providing a precursor solution comprising a metal containing reactive precursor material dissolved into a complexing solvent; depositing the precursor solution onto a surface of a substrate to form a film; and forming a charge selective transport layer on the substrate by annealing the film.

A hole modulator for InGaN/GaN light-emitting diodes

International Nuclear Information System (INIS)

Zhang, Zi-Hui; Kyaw, Zabu; Liu, Wei; Ji, Yun; Wang, Liancheng; Tan, Swee Tiam; Sun, Xiao Wei; Demir, Hilmi Volkan

2015-01-01

The low p-type doping efficiency of the p-GaN layer has severely limited the performance of InGaN/GaN light-emitting diodes (LEDs) due to the ineffective hole injection into the InGaN/GaN multiple quantum well (MQW) active region. The essence of improving the hole injection efficiency is to increase the hole concentration in the p-GaN layer. Therefore, in this work, we have proposed a hole modulator and studied it both theoretically and experimentally. In the hole modulator, the holes in a remote p-type doped layer are depleted by the built-in electric field and stored in the p-GaN layer. By this means, the overall hole concentration in the p-GaN layer can be enhanced. Furthermore, the hole modulator is adopted in the InGaN/GaN LEDs, which reduces the effective valance band barrier height for the p-type electron blocking layer from ∼332 meV to ∼294 meV at 80 A/cm 2 and demonstrates an improved optical performance, thanks to the increased hole concentration in the p-GaN layer and thus the improved hole injection into the MQWs

Effect of eggshell temperature and a hole in the air cell on the perinatal development and physiology of layer hatchlings

NARCIS (Netherlands)

Molenaar, R.; Vries, de S.; Anker, van den I.; Meijerhof, R.; Kemp, B.; Brand, van den H.

2010-01-01

To investigate the effect of incubation conditions on layer hatchlings, an experiment was performed in which layer eggs were incubated at a normal (37.8°C) or high (38.9°C) eggshell temperature (EST) and a hole was punctured in the air cell of half of the eggs in both EST treatments from d 14 of

Role of the polymeric hole injection layer on the efficiency and stability of organic light emitting diodes with small molecular emitters

International Nuclear Information System (INIS)

Chin, Byung Doo

2008-01-01

In this paper, an improvement in the properties of the small molecular organic light emitting diode (OLED) upon application of a polymeric hole injection layer (HIL) was reported. The luminous efficiency, operating voltage and lifetime of devices with dye-doped small molecule emitters (fluorescent and phosphorescent) were found to be sensitive to the HIL/hole transport layer (HTL) combination used, where the improved injection and brightness was shown at the hole cascading structure and the longer lifetime behaviour was obtained at the hole-trapping structure. Use of a polymeric HIL significantly increased the luminous current efficiency and lifetime for both fluorescent blue and phosphorescent green/red light emitters. The polymeric HIL was effective in terms of the driving characteristics of phosphorescent OLED, since it provides higher brightness behaviour at lower current density. The apparent shade of the pixel image at light emission, which will probably induce degradation at the pixel wall interface, will be suppressed by the use of polymeric HIL. In spite of the ambiguity in the formation of such shaded pixels and their influence at the decay of OLED, intrinsic stability of polymeric HIL/anode would be advantageous for stable storage and operation of devices.

Black Hole Universe Model and Dark Energy

Science.gov (United States)

Zhang, Tianxi

2011-01-01

Considering black hole as spacetime and slightly modifying the big bang theory, the author has recently developed a new cosmological model called black hole universe, which is consistent with Mach principle and Einsteinian general relativity and self consistently explains various observations of the universe without difficulties. According to this model, the universe originated from a hot star-like black hole and gradually grew through a supermassive black hole to the present universe by accreting ambient material and merging with other black holes. The entire space is infinitely and hierarchically layered and evolves iteratively. The innermost three layers are the universe that we lives, the outside space called mother universe, and the inside star-like and supermassive black holes called child universes. The outermost layer has an infinite radius and zero limits for both the mass density and absolute temperature. All layers or universes are governed by the same physics, the Einstein general relativity with the Robertson-Walker metric of spacetime, and tend to expand outward physically. When one universe expands out, a new similar universe grows up from its inside black holes. The origin, structure, evolution, expansion, and cosmic microwave background radiation of black hole universe have been presented in the recent sequence of American Astronomical Society (AAS) meetings and published in peer-review journals. This study will show how this new model explains the acceleration of the universe and why dark energy is not required. We will also compare the black hole universe model with the big bang cosmology.

Efficient blue-green and green electroluminescent devices obtained by doping iridium complexes into hole-block material as supplementary light-emitting layer

Energy Technology Data Exchange (ETDEWEB)

Zhou, Liang [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zheng, Youxuan, E-mail: yxzheng@mail.nju.edu.cn [State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Deng, Ruiping; Feng, Jing; Song, Mingxing; Hao, Zhaomin [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zhang, Hongjie, E-mail: hongjie@ciac.jl.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Zuo, Jinglin; You, Xiaozeng [State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China)

2014-04-15

In this work, organic electroluminescent (EL) devices with dominant and supplementary light-emitting layers (EMLs) were designed to further improve the EL performances of two iridium{sup III}-based phosphorescent complexes, which have been reported to provide EL devices with slow EL efficiency roll-off. The widely used hole-block material 2,2′,2''-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) was selected as host material to construct the supplementary EML. Compared with single-EML devices, double-EMLs devices showed higher EL efficiencies, higher brightness, and lower operation voltage attributed to wider recombination zone and better balance of carriers. In addition, the insertion of supplementary EML is instrumental in facilitating carriers trapping, thus improving the color purity. Finally, high performance blue-green and green EL devices with maximum current efficiencies of 35.22 and 90.68 cd/A, maximum power efficiencies of 26.36 and 98.18 lm/W, and maximum brightness of 56,678 and 112,352 cd/m{sup 2}, respectively, were obtained by optimizing the doping concentrations. Such a device design strategy extends the application of a double EML device structure and provides a chance to simplify device fabrication processes. -- Highlights: • Electroluminescent devices with supplementary light-emitting layer were fabricated. • Doping concentrations and thicknesses were optimized. • Better balance of holes and electrons causes the enhanced efficiency. • Improved carrier trapping suppresses the emission of host material.

Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

International Nuclear Information System (INIS)

Lu, Yu-Hsuan; Pilkuhn, Manfred H.; Fu, Yi-Keng; Chu, Mu-Tao; Huang, Shyh-Jer; Su, Yan-Kuin; Wang, Kang L.

2014-01-01

The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL

Tailoring of polarization in electron blocking layer for electron confinement and hole injection in ultraviolet light-emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Lu, Yu-Hsuan; Pilkuhn, Manfred H. [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Fu, Yi-Keng; Chu, Mu-Tao [Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (China); Huang, Shyh-Jer, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States); Su, Yan-Kuin, E-mail: yksu@mail.ncku.edu.tw, E-mail: totaljer48@gmail.com [Department of Electrical Engineering, Institute of Microelectronics and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Electronic Engineering, Kun-Shan University, Tainan 71003, Taiwan (China); Wang, Kang L. [Department of Electrical Engineering, University of California at Los Angeles, Los Angeles, California 90095 (United States)

2014-03-21

The influence of the AlGaN electron blocking layer (EBL) with graded aluminum composition on electron confinement and hole injection in AlGaN-based ultraviolet light-emitting diodes (LEDs) are investigated. The light output power of LED with graded AlGaN EBL was markedly improved, comparing to LED with conventional EBL. In experimental results, a high increment of 86.7% can be obtained in light output power. Simulation analysis shows that via proper modification of the barrier profile from the last barrier of the active region to EBL, not only the elimination of electron overflow to p-type layer can be achieved but also the hole injection into the active region can be enhanced, compared to a conventional LED structure. The dominant factor to the performance improvement is shown to be the modulation of polarization field by the graded Al composition in EBL.

Hypodense regions (holes) in the retinal nerve fiber layer in frequency-domain OCT scans of glaucoma patients and suspects.

Science.gov (United States)

Xin, Daiyan; Talamini, Christine L; Raza, Ali S; de Moraes, Carlos Gustavo V; Greenstein, Vivienne C; Liebmann, Jeffrey M; Ritch, Robert; Hood, Donald C

2011-09-09

To better understand hypodense regions (holes) that appear in the retinal nerve fiber layer (RNFL) of frequency-domain optical coherence tomography (fdOCT) scans of patients with glaucoma and glaucoma suspects. Peripapillary circle (1.7-mm radius) and cube optic disc fdOCT scans were obtained on 208 eyes from 110 patients (57.4 ± 13.2 years) with glaucomatous optic neuropathy (GON) and 45 eyes of 45 controls (48.0 ± 12.6 years) with normal results of fundus examination. Holes in the RNFL were identified independently by two observers on the circle scans. Holes were found in 33 (16%) eyes of 28 (25%) patients; they were not found in any of the control eyes. Twenty-four eyes had more than one hole. Although some holes were relatively large, others were small. In general, the holes were located adjacent to blood vessels; only three eyes had isolated holes that were not adjacent to a vessel. The holes tended to be in the regions that are thickest in healthy controls and were associated with arcuate defects in patients. Holes were not seen in the center of the temporal disc region. They were more common in the superior (25 eyes) than in the inferior (15 eyes) disc. Of the 30 eyes with holes with reliable visual fields, seven were glaucoma suspect eyes with normal visual fields. The holes in the RNFL seen in patients with GON were probably due to a local loss of RNFL fibers and can occur in the eyes of glaucoma suspects with normal visual fields.

Study on characteristics of a double-conductible channel organic thin-film transistor with an ultra-thin hole-blocking layer

International Nuclear Information System (INIS)

Guang-Cai, Yuan; Zheng, Xu; Su-Ling, Zhao; Fu-Jun, Zhang; Xue-Yan, Tian; Xu-Rong, Xu; Na, Xu

2009-01-01

The properties of top-contact organic thin-film transistors (TC-OTFTs) using ultra-thin 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline (BCP) as a hole-blocking interlayer have been improved significantly and a BCP interlayer was inserted into the middle of the pentacene active layer. This paper obtains a fire-new transport mode of an OTFT device with double-conductible channels. The accumulation and transfer of the hole carriers are limited by the BCP interlayer in the vertical region of the channel. A huge amount of carriers is located not only at the interface between pentacene and the gate insulator, but also at the two interfaces of pentacene/BCP interlayer and pentacene/gate insulator, respectively. The results suggest that the BCP interlayer may be useful to adjust the hole accumulation and transfer, and can increase the hole mobility and output current of OTFTs. The TC-OTFTs with a BCP interlayer at V DS = −20 V showed excellent hole mobility μFE and threshold voltage V TH of 0.58 cm 2 /(V·s) and −4.6 V, respectively

Formation of BaSi2 heterojunction solar cells using transparent MoOx hole transport layers

Science.gov (United States)

Du, W.; Takabe, R.; Baba, M.; Takeuchi, H.; Hara, K. O.; Toko, K.; Usami, N.; Suemasu, T.

2015-03-01

Heterojunction solar cells that consist of 15 nm thick molybdenum trioxide (MoOx, x < 3) as a hole transport layer and 600 nm thick unpassivated or passivated n-BaSi2 layers were demonstrated. Rectifying current-voltage characteristics were observed when the surface of BaSi2 was exposed to air. When the exposure time was decreased to 1 min, an open circuit voltage of 200 mV and a short circuit current density of 0.5 mA/cm2 were obtained under AM1.5 illumination. The photocurrent density under a reverse bias voltage of -1 V reached 25 mA/cm2, which demonstrates the significant potential of BaSi2 for solar cell applications.

Bifurcation from stable holes to replicating holes in vibrated dense suspensions.

Science.gov (United States)

Ebata, H; Sano, M

2013-11-01

In vertically vibrated starch suspensions, we observe bifurcations from stable holes to replicating holes. Above a certain acceleration, finite-amplitude deformations of the vibrated surface continue to grow until void penetrates fluid layers, and a hole forms. We studied experimentally and theoretically the parameter dependence of the holes and their stabilities. In suspensions of small dispersed particles, the circular shapes of the holes are stable. However, we find that larger particles or lower surface tension of water destabilize the circular shapes; this indicates the importance of capillary forces acting on the dispersed particles. Around the critical acceleration for bifurcation, holes show intermittent large deformations as a precursor to hole replication. We applied a phenomenological model for deformable domains, which is used in reaction-diffusion systems. The model can explain the basic dynamics of the holes, such as intermittent behavior, probability distribution functions of deformation, and time intervals of replication. Results from the phenomenological model match the linear growth rate below criticality that was estimated from experimental data.

Electron-hole pairing and anomalous properties of layered high-Tc compounds

International Nuclear Information System (INIS)

Efetov, K.B.

1991-01-01

Band-structure pictures for layered high-T c materials available in the literature show that, besides the dispersive broad band responsible for metallic properties, there are at least two additional bands having minima and maxima near the Fermi surface. These additional bands belong to different planes (for example, CuO planes and BiO planes in Bi 2 Sr 2 CaCu 2 O 8 ) or to planes and chains (in YBa 2 Cu 3 O 7 ). Provided the Coulomb repulsion is not very weak, pairing of electrons and holes belonging to these additional bands in different planes or planes and chains is possible. It is shown that, if this possibility is realized, a transition in the additional bands into a state of an excitonic dielectric occurs. The spin of an electron-hole pair can be both 0 and 1. Due to the fact that the electron and the hole of the pair belong to different planes, there are no charge- or spin-density waves. This excitonic insulator can serve as a polarizing substance and give a strong attraction between electrons of the metallic band even if the bare interaction is repulsive. It is also shown that some interesting gapless excitations exist. Provided there are impurities in the system that scatter from plane to plane, these excitations are coupled to the electrons of the metallic band. This effective interaction can be described in terms of an effective mode P(ω) with ImP(ω)∼-sgnω. As a result, one can obtain such properties of the normal state as a linear dependence of the resistivity on temperature, linear dependence of the density of states on energy, constant background in the Raman-scattering intensity, large nuclear relaxation rate, etc., which are very well known from experiments

A New Cosmological Model: Black Hole Universe

Directory of Open Access Journals (Sweden)

Zhang T. X.

2009-07-01

Full Text Available A new cosmological model called black hole universe is proposed. According to this model, the universe originated from a hot star-like black hole with several solar masses, and gradually grew up through a supermassive black hole with billion solar masses to the present state with hundred billion-trillion solar masses by accreting ambient mate- rials and merging with other black holes. The entire space is structured with infinite layers hierarchically. The innermost three layers are the universe that we are living, the outside called mother universe, and the inside star-like and supermassive black holes called child universes. The outermost layer is infinite in radius and limits to zero for both the mass density and absolute temperature. The relationships among all layers or universes can be connected by the universe family tree. Mathematically, the entire space can be represented as a set of all universes. A black hole universe is a subset of the en- tire space or a subspace. The child universes are null sets or empty spaces. All layers or universes are governed by the same physics - the Einstein general theory of relativity with the Robertson-walker metric of spacetime - and tend to expand outward physically. The evolution of the space structure is iterative. When one universe expands out, a new similar universe grows up from its inside. The entire life of a universe begins from the birth as a hot star-like or supermassive black hole, passes through the growth and cools down, and expands to the death with infinite large and zero mass density and absolute temperature. The black hole universe model is consistent with the Mach principle, the observations of the universe, and the Einstein general theory of relativity. Its various aspects can be understood with the well-developed physics without any difficulty. The dark energy is not required for the universe to accelerate its expansion. The inflation is not necessary because the black hole universe

Effects of pentacene-doped PEDOT:PSS as a hole-conducting layer on the performance characteristics of polymer photovoltaic cells

OpenAIRE

Kim, Hyunsoo; Lee, Jungrae; Ok, Sunseong; Choe, Youngson

2012-01-01

We have investigated the effect of pentacene-doped poly(3,4-ethylenedioxythiophene:poly(4-styrenesulfonate) [PEDOT:PSS] films as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the amount of pentacene and the annealing temperature of pentacene-doped PEDOT:PSS layer, the changes of performance characteristics were evaluated. Pentacene-doped PEDOT:PSS thin films were prepared by dissolving pentacene in 1-methyl-2-pyrrolidinone solvent and mixing with PEDO...

Performance enhancement of perovskite solar cells with Mg-doped TiO2 compact film as the hole-blocking layer

International Nuclear Information System (INIS)

Wang, Jing; Qin, Minchao; Tao, Hong; Ke, Weijun; Chen, Zhao; Wan, Jiawei; Qin, Pingli; Lei, Hongwei; Fang, Guojia; Xiong, Liangbin; Yu, Huaqing

2015-01-01

In this letter, we report perovskite solar cells with thin dense Mg-doped TiO 2 as hole-blocking layers (HBLs), which outperform cells using TiO 2 HBLs in several ways: higher open-circuit voltage (V oc ) (1.08 V), power conversion efficiency (12.28%), short-circuit current, and fill factor. These properties improvements are attributed to the better properties of Mg-modulated TiO 2 as compared to TiO 2 such as better optical transmission properties, upshifted conduction band minimum (CBM) and downshifted valence band maximum (VBM), better hole-blocking effect, and higher electron life time. The higher-lying CBM due to the modulation with wider band gap MgO and the formation of magnesium oxide and magnesium hydroxides together resulted in an increment of V oc . In addition, the Mg-modulated TiO 2 with lower VBM played a better role in the hole-blocking. The HBL with modulated band position provided better electron transport and hole blocking effects within the device

Inverted polymer solar cells with Nafion® as the hole extraction layer: efficiency and lifetime studies

International Nuclear Information System (INIS)

Manceau, Matthieu; Berson, Solenn

2014-01-01

The use of Nafion ®  as the hole extraction layer in polymer solar cells is demonstrated in this work. Inverted devices were built on plastic foil with the following architecture: PET/ITO/ZnO/P3HT:PCBM/Nafion ® /Ag. The Nafion ®  was processed from a surfactant-free solution in alcoholic solvents on top of the active layer. Optimization of film thickness and annealing yielded fully functional devices with power conversion efficiency similar to others referenced, along with good operational stability. (paper)

Inverted bulk-heterojunction organic solar cells with the transfer-printed anodes and low-temperature-processed ultrathin buffer layers

Science.gov (United States)

Itoh, Eiji; Sakai, Shota; Fukuda, Katsutoshi

2018-03-01

We studied the effects of a hole buffer layer [molybdenum oxide (MoO3) and natural copper oxide layer] and a low-temperature-processed electron buffer layer on the performance of inverted bulk-heterojunction organic solar cells in a device consisting of indium-tin oxide (ITO)/poly(ethylene imine) (PEI)/titanium oxide nanosheet (TiO-NS)/poly(3-hexylthiopnehe) (P3HT):phenyl-C61-butyric acid methylester (PCBM)/oxide/anode (Ag or Cu). The insertion of ultrathin TiO-NS (˜1 nm) and oxide hole buffer layers improved the open circuit voltage V OC, fill factor, and rectification properties owing to the effective hole blocking and electron transport properties of ultrathin TiO-NS, and to the enhanced work function difference between TiO-NS and the oxide hole buffer layer. The insertion of the TiO-NS contributed to the reduction in the potential barrier at the ITO/PEI/TiO-NS/active layer interface for electrons, and the insertion of the oxide hole buffer layer contributed to the reduction in the potential barrier for holes. The marked increase in the capacitance under positive biasing in the capacitance-voltage characteristics revealed that the combination of TiO-NS and MoO3 buffer layers contributes to the selective transport of electrons and holes, and blocks counter carriers at the active layer/oxide interface. The natural oxide layer of the copper electrode also acts as a hole buffer layer owing to the increase in the work function of the Cu surface in the inverted cells. The performance of the cell with evaporated MoO3 and Cu layers that were transfer-printed to the active layer was almost comparable to that of the cell with MoO3 and Ag layers directly evaporated onto the active layer. We also demonstrated comparable device performance in the cell with all-printed MoO3 and low-temperature-processed silver nanoparticles as an anode.

Slot-Die-Coated V2O5 as Hole Transport Layer for Flexible Organic Solar Cells and Optoelectronic Devices

DEFF Research Database (Denmark)

Beliatis, Michail; Helgesen, Martin; Garcia Valverde, Rafael

2016-01-01

Vanadium pentoxide has been proposed as a good alternative hole transport layer for improving device lifetime of organic photovoltaics. The article presents a study on the optimization of slot-die-coated vanadium oxide films produced with a roll coating machine with the aim of achieving scalable ...

Flexible ITO-free organic solar cells applying aqueous solution-processed V2O5 hole transport layer: An outdoor stability study

Directory of Open Access Journals (Sweden)

F. Anderson S. Lima

2016-02-01

Full Text Available Solution processable semiconductor oxides have opened a new paradigm for the enhancement of the lifetime of thin film solar cells. Their fabrication by low-cost and environmentally friendly solution-processable methods makes them ideal barrier (hole and electron transport layers. In this work, we fabricate flexible ITO-free organic solar cells (OPV by printing methods applying an aqueous solution-processed V2O5 as the hole transport layer (HTL and compared them to devices applying PEDOT:PSS. The transparent conducting electrode was PET/Ag/PEDOT/ZnO, and the OPV configuration was PET/Ag/PEDOT/ZnO/P3HT:PC60BM/HTL/Ag. Outdoor stability analyses carried out for more than 900 h revealed higher stability for devices fabricated with the aqueous solution-processed V2O5.

Hole-to-surface resistivity measurements at Gibson Dome (drill hole GD-1) Paradox basin, Utah

Science.gov (United States)

Daniels, J.J.

1984-01-01

Hole-to-surface resistivity measurements were made in a deep drill hole (GD-1), in San Juan County, Utah, which penetrated a sequence of sandstone, shale, and evaporite. These measurements were made as part of a larger investigation to study the suitability of an area centered around the Gibson Dome structure for nuclear waste disposal. The magnitude and direction of the total electric field resulting from a current source placed in a drill hole is calculated from potential difference measurements for a grid of closely-spaced stations. A contour map of these data provides a detailed map of the distribution of the electric field away from the drill hole. Computation of the apparent resistivity from the total electric field helps to interpret the data with respect to the ideal situation of a layered earth. Repeating the surface measurements for different source depths gives an indication of variations in the geoelectric section with depth. The quantitative interpretation of the field data at Gibson Dome was hindered by the pressure of a conductive borehole fluid. However, a qualitative interpretation of the field data indicates the geoelectric section around drill hole GD-1 is not perfectly layered. The geoelectric section appears to dip to the northwest, and contains anomalies in the resistivity distribution that may be representative of localized thickening or folding of the salt layers.

All-inorganic quantum-dot light-emitting-diodes with vertical nickel oxide nanosheets as hole transport layer

Directory of Open Access Journals (Sweden)

Jiahui Li

2016-10-01

Full Text Available All-inorganic quantum dot light emitting diodes (QLEDs have gained great attention as a result of their high stability under oxygen-rich, humid and high current working conditions. In this work, we have fabricated an all-inorganic QLED device (FTO/NiO/QDs/AZO/Ag with sandwich-structure, wherein the inorganic metal oxides thin films of NiO and AZO were employed as hole and electron transport layers, respectively. The porous NiO layer with vertical lamellar nanosheets interconnected microstructure have been directly synthesized on the substrate of conductive FTO glass and increased the wettability of CdSe@ZnS QDs, which result in an enhancement of current transport performance of the QLED.

Influence of Weak Base Addition to Hole-Collecting Buffer Layers in Polymer:Fullerene Solar Cells

Directory of Open Access Journals (Sweden)

Jooyeok Seo

2017-02-01

Full Text Available We report the effect of weak base addition to acidic polymer hole-collecting layers in normal-type polymer:fullerene solar cells. Varying amounts of the weak base aniline (AN were added to solutions of poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate (PEDOT:PSS. The acidity of the aniline-added PEDOT:PSS solutions gradually decreased from pH = 1.74 (AN = 0 mol% to pH = 4.24 (AN = 1.8 mol %. The electrical conductivity of the PEDOT:PSS-AN films did not change much with the pH value, while the ratio of conductivity between out-of-plane and in-plane directions was dependent on the pH of solutions. The highest power conversion efficiency (PCE was obtained at pH = 2.52, even though all devices with the PEDOT:PSS-AN layers exhibited better PCE than those with the pristine PEDOT:PSS layers. Atomic force microscopy investigation revealed that the size of PEDOT:PSS domains became smaller as the pH increased. The stability test for 100 h illumination under one sun condition disclosed that the PCE decay was relatively slower for the devices with the PEDOT:PSS-AN layers than for those with pristine PEDOT:PSS layers.

Copper (I) Selenocyanate (CuSeCN) as a Novel Hole-Transport Layer for Transistors, Organic Solar Cells, and Light-Emitting Diodes

KAUST Repository

Wijeyasinghe, Nilushi; Tsetseris, Leonidas; Regoutz, Anna; Sit, Wai-Yu; Fei, Zhuping; Du, Tian; Wang, Xuhua; McLachlan, Martyn A.; Vourlias, George; Patsalas, Panos A.; Payne, David J.; Heeney, Martin; Anthopoulos, Thomas D.

2018-01-01

The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution-processable hole-transport layer (HTL) material in transistors, organic light-emitting diodes, and solar cells are reported. Density-functional theory calculations combined with X-ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution-processed layers are found to be nanocrystalline and optically transparent (>94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at −5.1 eV. Hole-transport analysis performed using field-effect measurements confirms the p-type character of CuSeCN yielding a hole mobility of 0.002 cm2 V−1 s−1. When CuSeCN is incorporated as the HTL material in organic light-emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4-ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.

Copper (I) Selenocyanate (CuSeCN) as a Novel Hole-Transport Layer for Transistors, Organic Solar Cells, and Light-Emitting Diodes

KAUST Repository

Wijeyasinghe, Nilushi

2018-02-01

The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution-processable hole-transport layer (HTL) material in transistors, organic light-emitting diodes, and solar cells are reported. Density-functional theory calculations combined with X-ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution-processed layers are found to be nanocrystalline and optically transparent (>94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at −5.1 eV. Hole-transport analysis performed using field-effect measurements confirms the p-type character of CuSeCN yielding a hole mobility of 0.002 cm2 V−1 s−1. When CuSeCN is incorporated as the HTL material in organic light-emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4-ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.

Selecting core-hole localization or delocalization in CS2 by photofragmentation dynamics.

Science.gov (United States)

Guillemin, R; Decleva, P; Stener, M; Bomme, C; Marin, T; Journel, L; Marchenko, T; Kushawaha, R K; Jänkälä, K; Trcera, N; Bowen, K P; Lindle, D W; Piancastelli, M N; Simon, M

2015-01-21

Electronic core levels in molecules are highly localized around one atomic site. However, in single-photon ionization of symmetric molecules, the question of core-hole localization versus delocalization over two equivalent atoms has long been debated as the answer lies at the heart of quantum mechanics. Here, using a joint experimental and theoretical study of core-ionized carbon disulfide (CS2), we demonstrate that it is possible to experimentally select distinct molecular-fragmentation pathways in which the core hole can be considered as either localized on one sulfur atom or delocalized between two indistinguishable sulfur atoms. This feat is accomplished by measuring photoelectron angular distributions within the frame of the molecule, directly probing entanglement or disentanglement of quantum pathways as a function of how the molecule dissociates.

Low resistivity ZnO-GO electron transport layer based CH3NH3PbI3 solar cells

Directory of Open Access Journals (Sweden)

Muhammad Imran Ahmed

2016-06-01

Full Text Available Perovskite based solar cells have demonstrated impressive performances. Controlled environment synthesis and expensive hole transport material impede their potential commercialization. We report ambient air synthesis of hole transport layer free devices using ZnO-GO as electron selective contacts. Solar cells fabricated with hole transport layer free architecture under ambient air conditions with ZnO as electron selective contact achieved an efficiency of 3.02%. We have demonstrated that by incorporating GO in ZnO matrix, low resistivity electron selective contacts, critical to improve the performance, can be achieved. We could achieve max efficiency of 4.52% with our completed devices for ZnO: GO composite. Impedance spectroscopy confirmed the decrease in series resistance and an increase in recombination resistance with inclusion of GO in ZnO matrix. Effect of temperature on completed devices was investigated by recording impedance spectra at 40 and 60 oC, providing indirect evidence of the performance of solar cells at elevated temperatures.

Flexible ITO-free organic solar cells applying aqueous solution-processed V2O5 hole transport layer: An outdoor stability study

DEFF Research Database (Denmark)

Lima, F. Anderson S.; Beliatis, Michail J.; Roth, Bérenger

2016-01-01

Solution processable semiconductor oxides have opened a new paradigm for theenhancement of the lifetime of thin film solar cells. Their fabrication by low-costand environmentally friendly solution-processable methods makes them ideal barrier(hole and electron) transport layers. In this work, we f...

Electrical response of electron selective atomic layer deposited TiO2‑x heterocontacts on crystalline silicon substrates

Science.gov (United States)

Ahiboz, Doğuşcan; Nasser, Hisham; Aygün, Ezgi; Bek, Alpan; Turan, Raşit

2018-04-01

Integration of oxygen deficient sub-stoichiometric titanium dioxide (TiO2‑x) thin films as the electron transporting-hole blocking layer in solar cell designs are expected to reduce fabrication costs by eliminating high temperature processes while maintaining high conversion efficiencies. In this paper, we conducted a study to reveal the electrical properties of TiO2‑x thin films grown on crystalline silicon (c-Si) substrates by atomic layer deposition (ALD) technique. Effect of ALD substrate temperature, post deposition annealing, and doping type of the c-Si substrate on the interface states and TiO2‑x bulk properties were extracted by performing admittance (C-V, G-V) and current-voltage (J-V) measurements. Moreover, the asymmetry in C-V and J-V measurements between the p-n type and n-n TiO2‑x-c-Si heterojunction types were examined and the electron transport selectivity of TiO2‑x was revealed.

High-performance inverted planar heterojunction perovskite solar cells based on a solution-processed CuOx hole transport layer.

Science.gov (United States)

Sun, Weihai; Li, Yunlong; Ye, Senyun; Rao, Haixia; Yan, Weibo; Peng, Haitao; Li, Yu; Liu, Zhiwei; Wang, Shufeng; Chen, Zhijian; Xiao, Lixin; Bian, Zuqiang; Huang, Chunhui

2016-05-19

During the past several years, methylammonium lead halide perovskites have been widely investigated as light absorbers for thin-film photovoltaic cells. Among the various device architectures, the inverted planar heterojunction perovskite solar cells have attracted special attention for their relatively simple fabrication and high efficiencies. Although promising efficiencies have been obtained in the inverted planar geometry based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) sulfonic acid ( PSS) as the hole transport material (HTM), the hydrophilicity of the PSS is a critical factor for long-term stability. In this paper, a CuOx hole transport layer from a facile solution-processed method was introduced into the inverted planar heterojunction perovskite solar cells. After the optimization of the devices, a champion PCE of 17.1% was obtained with an open circuit voltage (Voc) of 0.99 V, a short-circuit current (Jsc) of 23.2 mA cm(-2) and a fill factor (FF) of 74.4%. Furthermore, the unencapsulated device cooperating with the CuOx film exhibited superior performance in the stability test, compared to the device involving the PSS layer, indicating that CuOx could be a promising HTM for replacing PSS in inverted planar heterojunction perovskite solar cells.

Copper(I) Thiocyanate (CuSCN) Hole-Transport Layers Processed from Aqueous Precursor Solutions and Their Application in Thin-Film Transistors and Highly Efficient Organic and Organometal Halide Perovskite Solar Cells

KAUST Repository

Wijeyasinghe, Nilushi; Regoutz, Anna; Eisner, Flurin; Du, Tian; Tsetseris, Leonidas; Lin, Yen-Hung; Faber, Hendrik; Pattanasattayavong, Pichaya; Li, Jinhua; Yan, Feng; McLachlan, Martyn A.; Payne, David J.; Heeney, Martin; Anthopoulos, Thomas D.

2017-01-01

spectra agree with first-principles calculations. Study of the hole-transport properties using field-effect transistor measurements reveals that the aqueous-processed CuSCN layers exhibit a fivefold higher hole mobility than films processed from diethyl

Prognostic significance of delayed structural recovery after macular hole surgery

DEFF Research Database (Denmark)

Christensen, Ulrik C; Krøyer, Kristian; Sander, Birgit

2009-01-01

was used; however, secondary macular hole surgery had a significant influence on diameter of photoreceptor layer discontinuity at 3 months. CONCLUSIONS: Structural recovery in the form of photoreceptor layer discontinuity with a diameter of more than approximately 1500 microm 3 months after macular hole...

Architecture of the Interface between the Perovskite and Hole-Transport Layers in Perovskite Solar Cells.

Science.gov (United States)

Moriya, Masahiro; Hirotani, Daisuke; Ohta, Tsuyoshi; Ogomi, Yuhei; Shen, Qing; Ripolles, Teresa S; Yoshino, Kenji; Toyoda, Taro; Minemoto, Takashi; Hayase, Shuzi

2016-09-22

The interface between the perovskite (PVK, CH 3 NH 3 PbI 3 ) and hole-transport layers in perovskite solar cells is discussed. The device architecture studied is as follows: F-doped tin oxide (FTO)-coated glass/compact TiO 2 /mesoporous TiO 2 /PVK/2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-MeOTAD)/Au. After a thin layer of 4,4,4-trifluorobutylammonium iodide (TFBA) was inserted at the interface between PVK and Spiro-MeOTAD, the photovoltaic efficiency increased from 11.6-14.5 % to 15.1-17.6 %. TFBA (10 ppm) was added in the PVK solution before coating. Owing to the low surface tension of TFBA, TFBA rose to the surface of the PVK layer spontaneously during spin-coating to make a thin organic layer. The PVK grain boundaries also seemed to be passivated with the addition of TFBA. However, large differences in Urbach energies and valence band energy level were not observed for the PVK layer with and without the addition of TFBA. The charge recombination time constant between the PVK and the Spiro-MeOTAD became slower (from 8.4 to 280 μsec) after 10 ppm of TFBA was added in the PVK. The experimental results using TFBA conclude that insertion of a very thin layer at the interface between PVK and Spiro-MeOTAD is effective for suppressing charge recombination and increasing photovoltaic performances. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasma enhanced atomic layer deposited MoOx emitters for silicon heterojunction solar cells

OpenAIRE

Ziegler, J.; Mews, M.; Kaufmann, K.; Schneider, T.; Sprafke, A.N.; Korte, L.; Wehrsporn, R.B

2015-01-01

A method for the deposition of molybdenum oxide MoOx with high growth rates at temperatures below 200 C based on plasma enhanced atomic layer deposition is presented. The stoichiometry of the overstoichiometric MoOx films can be adjusted by the plasma parameters. First results of these layers acting as hole selective contacts in silicon heterojunction solar cells are presented and discussed

Application of OCT in traumatic macular hole

Directory of Open Access Journals (Sweden)

Wen-Li Fu

2017-12-01

Full Text Available AIM: To observe the application of optical coherence tomography(OCTin the diseases of traumatic macular hole. METHODS: Twenty-five eyes of 23 patients with traumatic macular hole from January 2015 to January 2017 were enrolled in this study, including 9 eyes treated without surgeries, 16 eyes with surgeries. The image features were analyzed using OCT from ZEISS. RESULTS: The OCT characteristics in patients with traumatic macular hole were partial or full-thickness disappearance of the neuro-epithelium. Posterior vitreous detachment was not seen in the traumatic macular hole. OCT examination revealed that 4 eyes had partial detachment of macular hole and 21 eyes had full thickness detachment. Of the twenty-one eyes, 4 eyes had simple macular hole, 10 eyes had macular full-layer division with peripheral nerve epithelium edema, 7 eyes had the macular full-layer hole with the neuro-epithelium localized detachment. In the 25 eyes, 9 eyes did not undergo the surgery, of which 7 eyes were self-healing; 16 eyes were surgically treated. Postoperative OCT showed the macular structure were normal in 12 eyes with the visual acuity improved 3 lines; retinal nerve epithelium were thinning in 4 eyes, visual acuities were not significant improved after surgery. CONCLUSION: OCT examination is necessary for the diagnosis and treatment of traumatic macular hole.

Room-Temperature and Solution-Processable Cu-Doped Nickel Oxide Nanoparticles for Efficient Hole-Transport Layers of Flexible Large-Area Perovskite Solar Cells.

Science.gov (United States)

He, Qiqi; Yao, Kai; Wang, Xiaofeng; Xia, Xuefeng; Leng, Shifeng; Li, Fan

2017-12-06

Flexible perovskite solar cells (PSCs) using plastic substrates have become one of the most attractive points in the field of thin-film solar cells. Low-temperature and solution-processable nanoparticles (NPs) enable the fabrication of semiconductor thin films in a simple and low-cost approach to function as charge-selective layers in flexible PSCs. Here, we synthesized phase-pure p-type Cu-doped NiO x NPs with good electrical properties, which can be processed to smooth, pinhole-free, and efficient hole transport layers (HTLs) with large-area uniformity over a wide range of film thickness using a room-temperature solution-processing technique. Such a high-quality inorganic HTL allows for the fabrication of flexible PSCs with an active area >1 cm 2 , which have a power conversion efficiency over 15.01% without hysteresis. Moreover, the Cu/NiO x NP-based flexible devices also demonstrate excellent air stability and mechanical stability compared to their counterpart fabricated on the pristine NiO x films. This work will contribute to the evolution of upscaling flexible PSCs with a simple fabrication process and high device performances.

Low resistivity ZnO-GO electron transport layer based CH{sub 3}NH{sub 3}PbI{sub 3} solar cells

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Muhammad Imran, E-mail: imranrahbar@scme.nust.edu.pk, E-mail: amirhabib@scme.nust.edu.pk; Hussain, Zakir; Mujahid, Mohammad; Khan, Ahmed Nawaz [School of Chemical and Materials Engineering, National University of Sciences and Technology, Islamabad, 44000 (Pakistan); Javaid, Syed Saad [College of Aeronautical Engineering, National University of Sciences and Technology, Islamabad, 44000 (Pakistan); Habib, Amir, E-mail: imranrahbar@scme.nust.edu.pk, E-mail: amirhabib@scme.nust.edu.pk [School of Chemical and Materials Engineering, National University of Sciences and Technology, Islamabad, 44000 (Pakistan); The Department of Physics, College of Sciences, University of Hafar Al Batin, P.O. Box 1803, Hafar Al Batin 31991 Saudi Arabia (Saudi Arabia)

2016-06-15

Perovskite based solar cells have demonstrated impressive performances. Controlled environment synthesis and expensive hole transport material impede their potential commercialization. We report ambient air synthesis of hole transport layer free devices using ZnO-GO as electron selective contacts. Solar cells fabricated with hole transport layer free architecture under ambient air conditions with ZnO as electron selective contact achieved an efficiency of 3.02%. We have demonstrated that by incorporating GO in ZnO matrix, low resistivity electron selective contacts, critical to improve the performance, can be achieved. We could achieve max efficiency of 4.52% with our completed devices for ZnO: GO composite. Impedance spectroscopy confirmed the decrease in series resistance and an increase in recombination resistance with inclusion of GO in ZnO matrix. Effect of temperature on completed devices was investigated by recording impedance spectra at 40 and 60 {sup o}C, providing indirect evidence of the performance of solar cells at elevated temperatures.

Area-selective atomic layer deposition of platinum using photosensitive polyimide

NARCIS (Netherlands)

Vervuurt, R.H.J.; Sharma, A.; Jiao, Y.; Kessels, W.M.M.; Bol, A.A.

2016-01-01

Area-selective atomic layer deposition (AS-ALD) of platinum (Pt) was studied using photosensitive polyimide as a masking layer. The polyimide films were prepared by spin-coating and patterned using photolithography. AS-ALD of Pt using poly(methyl-methacrylate) (PMMA) masking layers was used as a

On the use of a charged tunnel layer as a hole collector to improve the efficiency of amorphous silicon thin-film solar cells

Energy Technology Data Exchange (ETDEWEB)

Ke, Cangming; Sahraei, Nasim; Aberle, Armin G. [Solar Energy Research Institute of Singapore, National University of Singapore, Singapore 117574 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Stangl, Rolf [Solar Energy Research Institute of Singapore, National University of Singapore, Singapore 117574 (Singapore); Peters, Ian Marius

2015-06-28

A new concept, using a negatively charged tunnel layer as a hole collector, is proposed and theoretically investigated for application in amorphous silicon thin-film solar cells. The concept features a glass/transparent conductive oxide/ultra-thin negatively charged tunnel layer/intrinsic a-Si:H/n-doped a-Si:H/metal structure. The key feature of this so called t{sup +}-i-n structure is the introduction of a negatively charged tunnel layer (attracting holes from the intrinsic absorber layer), which substitutes the highly recombination active p-doped a-Si:H layer in a conventional p-i-n configuration. Atomic layer deposited aluminum oxide (ALD AlO{sub x}) is suggested as a potential candidate for such a tunnel layer. Using typical ALD AlO{sub x} parameters, a 27% relative efficiency increase (i.e., from 9.7% to 12.3%) is predicted theoretically for a single-junction a-Si:H solar cell on a textured superstrate. This prediction is based on parameters that reproduce the experimentally obtained external quantum efficiency and current-voltage characteristics of a conventional processed p-i-n a-Si:H solar cell, reaching 9.7% efficiency and serving as a reference. Subsequently, the p-doped a-Si:H layer is replaced by the tunnel layer (studied by means of numerical device simulation). Using a t{sup +}-i-n configuration instead of a conventional p-i-n configuration will not only increase the short-circuit current density (from 14.4 to 14.9 mA/cm{sup 2}, according to our simulations), it also enhances the open-circuit voltage and the fill factor (from 917 mV to 1.0 V and from 74% to 83%, respectively). For this concept to work efficiently, a high work function front electrode material or a high interface charge is needed.

On the use of a charged tunnel layer as a hole collector to improve the efficiency of amorphous silicon thin-film solar cells

International Nuclear Information System (INIS)

Ke, Cangming; Sahraei, Nasim; Aberle, Armin G.; Stangl, Rolf; Peters, Ian Marius

2015-01-01

A new concept, using a negatively charged tunnel layer as a hole collector, is proposed and theoretically investigated for application in amorphous silicon thin-film solar cells. The concept features a glass/transparent conductive oxide/ultra-thin negatively charged tunnel layer/intrinsic a-Si:H/n-doped a-Si:H/metal structure. The key feature of this so called t + -i-n structure is the introduction of a negatively charged tunnel layer (attracting holes from the intrinsic absorber layer), which substitutes the highly recombination active p-doped a-Si:H layer in a conventional p-i-n configuration. Atomic layer deposited aluminum oxide (ALD AlO x ) is suggested as a potential candidate for such a tunnel layer. Using typical ALD AlO x parameters, a 27% relative efficiency increase (i.e., from 9.7% to 12.3%) is predicted theoretically for a single-junction a-Si:H solar cell on a textured superstrate. This prediction is based on parameters that reproduce the experimentally obtained external quantum efficiency and current-voltage characteristics of a conventional processed p-i-n a-Si:H solar cell, reaching 9.7% efficiency and serving as a reference. Subsequently, the p-doped a-Si:H layer is replaced by the tunnel layer (studied by means of numerical device simulation). Using a t + -i-n configuration instead of a conventional p-i-n configuration will not only increase the short-circuit current density (from 14.4 to 14.9 mA/cm 2 , according to our simulations), it also enhances the open-circuit voltage and the fill factor (from 917 mV to 1.0 V and from 74% to 83%, respectively). For this concept to work efficiently, a high work function front electrode material or a high interface charge is needed

Lead Monoxide: Two-Dimensional Ferromagnetic Semiconductor Induced by Hole-Doping

KAUST Repository

Wang, Yao

2017-04-12

We employ first-principles calculations to demonstrate ferromagnetic ground states for single- and multi-layer lead monoxide (PbO) under hole-doping, originating from a van Hove singularity at the valence band edge. Both the sample thickness and applied strain are found to have huge effects on the electronic and magnetic properties. Multi-layer PbO is an indirect band gap semiconductor, while a direct band gap is realized in the single-layer limit. In hole-doped single-layer PbO, biaxial tensile strain can enhance the stability of the ferromagnetic state.

Lead Monoxide: Two-Dimensional Ferromagnetic Semiconductor Induced by Hole-Doping

KAUST Repository

Wang, Yao; Zhang, Qingyun; Shen, Qian; Cheng, Yingchun; Schwingenschlö gl, Udo; Huang, Wei

2017-01-01

We employ first-principles calculations to demonstrate ferromagnetic ground states for single- and multi-layer lead monoxide (PbO) under hole-doping, originating from a van Hove singularity at the valence band edge. Both the sample thickness and applied strain are found to have huge effects on the electronic and magnetic properties. Multi-layer PbO is an indirect band gap semiconductor, while a direct band gap is realized in the single-layer limit. In hole-doped single-layer PbO, biaxial tensile strain can enhance the stability of the ferromagnetic state.

Influence of hole transport material/metal contact interface on perovskite solar cells

Science.gov (United States)

Lei, Lei; Zhang, Shude; Yang, Songwang; Li, Xiaomin; Yu, Yu; Wei, Qingzhu; Ni, Zhichun; Li, Ming

2018-06-01

Interfaces have a significant impact on the performance of perovskite solar cells. This work investigated the influence of hole transport material/metal contact interface on photovoltaic behaviours of perovskite solar devices. Different hole material/metal contact interfaces were obtained by depositing the metal under different conditions. High incident kinetic energy metal particles were proved to penetrate and embed into the hole transport material. These isolated metal particles in hole transport materials capture holes and increase the apparent carrier transport resistance of the hole transport layer. Sample temperature was found to be of great significance in metal deposition. Since metal vapour has a high temperature, the deposition process accumulated a large amount of heat. The heat evaporated the additives in the hole transport layer and decreased the hole conductivity. On the other hand, high temperature may cause iodization of the metal contact.

Polyethers containing 4-(carbazol-2-yl)-7-arylbenzo[c]-1,2,5-thiadiazole chromophores as solution processed materials for hole transporting layers of OLEDs

Science.gov (United States)

Krucaite, G.; Tavgeniene, D.; Xie, Z.; Lin, X.; Zhang, B.; Grigalevicius, S.

2018-02-01

Two polyethers containing electroactive pendent 4-(carbazol-2-yl)-7-arylbenzo[c]-1,2,5-thiadiazole moieties have been synthesized by the multi-step synthetic route. Full characterization of their structures is presented. The polymers represent derivatives of very high thermal stability with initial thermal degradation temperatures of 425 °C and 431 °C. Glass transition temperatures of the amorphous materials were also very high and reached values of 154 °C and 163 °C. The electron photoemission spectra of thin layers of the polymers showed ionization potentials of 5.84 eV and 5.93 eV. Hole-transporting properties of the polymeric materials were tested in the structures of organic light emitting diodes with Alq3 as the green emitter and electron transporting material. An electroluminescent device containing hole-transporting layer (HTL) of the polymer with electroactive 4-carbazolyl-7-phenylbenzo[c]-1,2,5-thiadiazole moieties exhibited turn on voltage of 6.2 V, maximum photometric efficiency of 2.5 cd/A and maximum brightness exceeding 300 cd/m2. The device containing HTL of the polymer with 4-carbazolyl-7-(1-naphtyl)benzo[c]-1,2,5-thiadiazole moieties demonstrated turn on voltage of 5.2 V, maximum photometric efficiency of 1.6 cd/A and maximum brightness exceeding 1500 cd/m2. The efficiencies were about 30-90% higher than that of the device containing widely used hole transporting layers of poly(9-vinylcarbazole).

Layered Black Phosphorus as a Selective Vapor Sensor.

Science.gov (United States)

Mayorga-Martinez, Carmen C; Sofer, Zdeněk; Pumera, Martin

2015-11-23

Black phosphorus is a layered material that is sensitive to the surrounding atmosphere. This is generally considered as a disadvantage, especially when compared to more stable layered compounds, such as graphite or MoS2. This sensitivity is now turned into an advantage. A vapor sensor that is based on layered black phosphorus and uses electrochemical impedance spectroscopy as the detection method is presented; the device selectively detects methanol vapor. The impedance phase measured at a constant frequency is used as a distinctive parameter for the selective quantification of methanol, and increases with the methanol concentration. The low detection limit of 28 ppm is well below the approved exposure limit of 200 ppm. The results are highly reproducible, and the vapor sensor is shown to be very selective in the presence of other vapors and to have long-term stability. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Improving the color purity and efficiency of blue organic light-emitting diodes (BOLED) by adding hole-blocking layer

International Nuclear Information System (INIS)

Huang, C.J.; Kang, C.C.; Lee, T.C.; Chen, W.R.; Meen, T.H.

2009-01-01

This work demonstrates the fabrication of a bright blue organic light-emitting diode (BOLED) with good color purity using 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl (DPVBi) and bathocuproine (BCP) as the emitting layer (EML) and the hole-blocking layer (HBL), respectively. Devices were prepared by vacuum deposition on indium tin oxide (ITO)-glass substrates. The thickness of DPVBi used in the OLED has an important effect on color and efficiency. The blue luminescence is maximal at 7670 cd/m 2 when 13 V is applied and the BCP thickness is 2 nm. The CIE coordinate at a luminance of 7670 cd/m 2 is (0.165, 0.173). Furthermore, the current efficiency is maximum at 4.25 cd/A when 9 V is applied.

Ablation of selected conducting layers by fiber laser

Science.gov (United States)

Pawlak, Ryszard; Tomczyk, Mariusz; Walczak, Maria

2014-08-01

Laser Direct Writing (LDW) are used in the manufacture of electronic circuits, pads, and paths in sub millimeter scale. They can also be used in the sensors systems. Ablative laser writing in a thin functional layer of material deposited on the dielectric substrate is one of the LDW methods. Nowadays functional conductive layers are composed from graphene paint or nanosilver paint, indium tin oxide (ITO), AgHTTM and layers containing carbon nanotubes. Creating conducting structures in transparent layers (ITO, AgHT and carbon nanotubes layers) may have special importance e.g. for flexi electronics. The paper presents research on the fabrication of systems of paths and appropriate pattern systems of paths and selected electronic circuits in AgHTTM and ITO layers deposited on glass and polymer substrates. An influence of parameters of ablative fiber laser treatment in nanosecond regime as well as an influence of scanning mode of laser beam on the pattern fidelity and on electrical parameters of a generated circuit was investigated.

Effects of pilot holes on longitudinal miniscrew stability and bony adaptation.

Science.gov (United States)

Carney, Lauren Ohlenforst; Campbell, Phillip M; Spears, Robert; Ceen, Richard F; Melo, Ana Cláudia; Buschang, Peter H

2014-11-01

The purposes of this study were to longitudinally evaluate the effects of pilot holes on miniscrew implant (MSI) stability and to determine whether the effects can be attributed to the quality or the quantity of bone surrounding the MSI. Using a randomized split-mouth design in 6 skeletally mature female foxhound-mix dogs, 17 MSIs (1.6 mm outer diameter) placed with pilot holes (1.1 mm) were compared with 17 identical MSIs placed without pilot holes. Implant stability quotient measurements of MSI stability were taken weekly for 7 weeks. Using microcomputed tomography with an isotropic resolution of 6 μm, bone volume fractions were measured for 3 layers of bone (6-24, 24-42, and 42-60 μm) surrounding the MSIs. At placement, the MSIs with pilot holes showed significantly (P holes (48.3 vs 47.5). Over time, the implant stability quotient values decreased significantly more for the MSIs placed with pilot holes than for those placed without pilot holes. After 7 weeks, the most coronal aspect of the 6- to 24-μm layer of cortical bone and the most coronal aspects of all 3 layers of trabecular bone showed significantly larger bone volume fractions for the MSIs placed without pilot holes than for those placed with pilot holes. MSIs placed with pilot holes show greater primary stability, but greater decreases in stability over time, due primarily to having less trabecular bone surrounding them. Copyright © 2014 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Two-Step Physical Deposition of a Compact CuI Hole-Transport Layer and the Formation of an Interfacial Species in Perovskite Solar Cells.

Science.gov (United States)

Gharibzadeh, Saba; Nejand, Bahram Abdollahi; Moshaii, Ahmad; Mohammadian, Nasim; Alizadeh, Amir Hossein; Mohammadpour, Rahele; Ahmadi, Vahid; Alizadeh, Abdolali

2016-08-09

A simple and practical approach is introduced for the deposition of CuI as an inexpensive inorganic hole-transport material (HTM) for the fabrication of low cost perovskite solar cells (PSCs) by gas-solid phase transformation of Cu to CuI. The method provides a uniform and well-controlled CuI layer with large grains and good compactness that prevents the direct connection between the contact electrodes. Solar cells prepared with CuI as the HTM with Au electrodes displays an exceptionally high short-circuit current density of 32 mA cm(-2) , owing to an interfacial species formed between the perovskite and the Cu resulting in a long wavelength contribution to the incident photon-to-electron conversion efficiency (IPCE), and an overall power conversion efficiency (PCE) of 7.4 %. The growth of crystalline and uniform CuI on a low roughness perovskite layer leads to remarkably high charge extraction in the cells, which originates from the high hole mobility of CuI in addition to a large number of contact points between CuI and the perovskite layer. In addition, the solvent-free method has no damaging side effect on the perovskite layer, which makes it an appropriate method for large scale applications of CuI in perovskite solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TFB:TPDSi2 interfacial layer usable in organic photovoltaic cells

Science.gov (United States)

Marks, Iobin J [Evanston, IL; Hains, Alexander W [Evanston, IL

2011-02-15

The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode; an active organic layer comprising an electron-donating organic material and an electron-accepting organic material; and an interfacial layer formed between the anode and active organic layer, where the interfacial layer comprises a hole-transporting polymer characterized with a hole-mobility higher than that of the electron-donating organic material in the active organic layer, and a small molecule that has a high hole-mobility and is capable of crosslinking on contact with air.

New regular black hole solutions

International Nuclear Information System (INIS)

Lemos, Jose P. S.; Zanchin, Vilson T.

2011-01-01

In the present work we consider general relativity coupled to Maxwell's electromagnetism and charged matter. Under the assumption of spherical symmetry, there is a particular class of solutions that correspond to regular charged black holes whose interior region is de Sitter, the exterior region is Reissner-Nordstroem and there is a charged thin-layer in-between the two. The main physical and geometrical properties of such charged regular black holes are analyzed.

A New Model of Black Hole Formation

Directory of Open Access Journals (Sweden)

Thayer G. D.

2013-10-01

Full Text Available The formation of a black hole and its event horizon are described. Conclusions, which are the result of a thought experiment, show that Schwarzschild [1] was correct: A singularity develops at the event horizon of a newly-formed black hole. The intense gravitational field that forms near the event horizon results in the mass-energy of the black hole accumulating in a layer just inside the event horizon, rather than collapsing into a central singularity.

Thermally Cross-Linkable Hole Transport Materials for Solution Processed Phosphorescent OLEDs

Science.gov (United States)

Kim, Beom Seok; Kim, Ohyoung; Chin, Byung Doo; Lee, Chil Won

2018-04-01

Materials for unique fabrication of a solution-processed, multi-layered organic light-emitting diode (OLED) were developed. Preparation of a hole transport layer with a thermally cross-linkable chemical structure, which can be processed to form a thin film and then transformed into an insoluble film by using an amine-alcohol condensation reaction with heat treatment, was investigated. Functional groups, such as triplenylamine linked with phenylcarbazole or biphenyl, were employed in the chemical structure of the hole transport layer in order to maintain high triplet energy properties. When phenylcarbazole or biphenyl compounds continuously react with triphenylamine under acid catalysis, a chemically stable thin film material with desirable energy-level properties for a blue OLED could be obtained. The prepared hole transport materials showed excellent surface roughness and thermal stability in comparison with the commercial reference material. On the solution-processed model hole transport layer, we fabricated a device with a blue phosphorescent OLED by using sequential vacuum deposition. The maximum external quantum, 19.3%, was improved by more than 40% over devices with the commercial reference material (11.4%).

The Antarctic ozone hole

International Nuclear Information System (INIS)

Jones, Anna E

2008-01-01

Since the mid 1970s, the ozone layer over Antarctica has experienced massive destruction during every spring. In this article, we will consider the atmosphere, and what ozone and the ozone layer actually are. We explore the chemistry responsible for the ozone destruction, and learn about why conditions favour ozone destruction over Antarctica. For the historical perspective, the events leading up to the discovery of the 'hole' are presented, as well as the response from the international community and the measures taken to protect the ozone layer now and into the future

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

Science.gov (United States)

Kim, Hyomin; Kwon, Yiseul; Choe, Youngson

2013-05-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration.

En face spectral domain optical coherence tomography analysis of lamellar macular holes.

Science.gov (United States)

Clamp, Michael F; Wilkes, Geoff; Leis, Laura S; McDonald, H Richard; Johnson, Robert N; Jumper, J Michael; Fu, Arthur D; Cunningham, Emmett T; Stewart, Paul J; Haug, Sara J; Lujan, Brandon J

2014-07-01

To analyze the anatomical characteristics of lamellar macular holes using cross-sectional and en face spectral domain optical coherence tomography. Forty-two lamellar macular holes were retrospectively identified for analysis. The location, cross-sectional length, and area of lamellar holes were measured using B-scans and en face imaging. The presence of photoreceptor inner segment/outer segment disruption and the presence or absence of epiretinal membrane formation were recorded. Forty-two lamellar macular holes were identified. Intraretinal splitting occurred within the outer plexiform layer in 97.6% of eyes. The area of intraretinal splitting in lamellar holes did not correlate with visual acuity. Eyes with inner segment/outer segment disruption had significantly worse mean logMAR visual acuity (0.363 ± 0.169; Snellen = 20/46) than in eyes without inner segment/outer segment disruption (0.203 ± 0.124; Snellen = 20/32) (analysis of variance, P = 0.004). Epiretinal membrane was present in 34 of 42 eyes (81.0%). En face imaging allowed for consistent detection and quantification of intraretinal splitting within the outer plexiform layer in patients with lamellar macular holes, supporting the notion that an area of anatomical weakness exists within Henle's fiber layer, presumably at the synaptic connection of these fibers within the outer plexiform layer. However, the en face area of intraretinal splitting did not correlate with visual acuity, disruption of the inner segment/outer segment junction was associated with significantly worse visual acuity in patients with lamellar macular holes.

Improving the color purity and efficiency of blue organic light-emitting diodes (BOLED) by adding hole-blocking layer

Energy Technology Data Exchange (ETDEWEB)

Huang, C.J., E-mail: chien@nuk.edu.t [Department of Applied Physics, National University of Kaohsiung, 700 Kaohsiung University Road, Nan-Tzu, Kaohsiung, Taiwan (China); Kang, C.C. [Department of Electro-Optical Engineering, Southern Taiwan University of Technology, 1 Nan-Tai St., Yung-Kang City, Tainan, Taiwan (China); Lee, T.C. [Department of Electrical Engineering, Southern Taiwan University of Technology, 1 Nan-Tai St., Yung-Kang City, Tainan, Taiwan (China); Chen, W.R.; Meen, T.H. [Department of Electronic Engineering, National Formosa University, 64 Wen-Hwa Road, Hu-Wei, Yunlin, Taiwan (China)

2009-11-15

This work demonstrates the fabrication of a bright blue organic light-emitting diode (BOLED) with good color purity using 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl (DPVBi) and bathocuproine (BCP) as the emitting layer (EML) and the hole-blocking layer (HBL), respectively. Devices were prepared by vacuum deposition on indium tin oxide (ITO)-glass substrates. The thickness of DPVBi used in the OLED has an important effect on color and efficiency. The blue luminescence is maximal at 7670 cd/m{sup 2} when 13 V is applied and the BCP thickness is 2 nm. The CIE coordinate at a luminance of 7670 cd/m{sup 2} is (0.165, 0.173). Furthermore, the current efficiency is maximum at 4.25 cd/A when 9 V is applied.

Peculiarities of interaction of the p{sub z}-, π- electrons and the σ{sub p}-holes at the top 1–6 layers of HOPG

Energy Technology Data Exchange (ETDEWEB)

Dementjev, A.P., E-mail: demcarbon@yandex.ru; Ivanov, K.E.

2017-03-31

Graphical abstract: The formation of π-bands and σ{sub p}- holes as result of the p{sub z} → π transitions in 2–6 graphene layers HOPG. The valence band spectrum taken from Murday et al. (1981). - Abstract: The present work continues the analysis of results of Dementjev et al. (2015) in order to identify the interlayer interactions of the π-bands. Analysis of the N(E) C KVV Auger spectra of highly-ordered pyro-graphite showed the absence of the electron exchange between the π-bands in 1–6 layers. Since the π-bands are formed by the p{sub z} → π transitions, one can suggest that the π-band occupation at each graphene layer is formed by the p{sub z}-electrons of this layer. Since the p{sub z} electrons belong to the σ{sub p}-bands, the p{sub z} → π transitions in the σ{sub p}-bands in each of 2–6 graphene layers result in formation of holes H, whose concentration is equal to the concentration of electrons in the π-bands [H{sub i}] ≡ [π{sub i}]. This shows the origin of the ambipolar conductivity in graphene. The absence of the electronic interaction between the π-bands allows a suggestion that the interaction between top six graphene layers is due to the van der Waals electrostatic attractive forces. These forces promote the p{sub z} → π transitions in each of the 2–6 graphene layers and depend on the number of graphene layers above. The N(E) C KVV Auger spectra allow identification of number (1–6) of graphene layers and the π-band occupation at each of the layer. For the first time a specification of the van der Waals forces in HOPG was done.

The feasibility of using solution-processed aqueous La2O3 as effective hole injection layer in organic light-emitting diode

Science.gov (United States)

Zhang, Yan; Li, Wanshu; Zhang, Ting; Yang, Bo; Zheng, Qinghong; Xu, Jiwen; Wang, Hua; Wang, Lihui; Zhang, Xiaowen; Wei, Bin

2018-01-01

Low-cost and scalable manufacturing boosts organic electronic devices with all solution process. La2O3 powders and corresponding aqueous solutions are facilely synthesized. Atomic force microscopy and scanning electron microscopy measurements show that solution-processed La2O3 behaves superior film morphology. X-ray diffraction and X-ray photoelectron spectroscopy measurements verify crystal phase and typical La signals. In comparison with the most widely-used hole injection layers (HILs) of MoOx and poly(ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), enhanced luminous efficiency is observed in organic light-emitting diode (OLED) using solution-processed La2O3 HIL. Current-voltage, impedance-voltage and phase angle-voltage transition curves clarify that solution-processed La2O3 behaves nearly comparable hole injection capacity to MoOx and PEDOT:PSS, and favorably tailors carrier balance. Moreover, the hole injection mechanism of solution-processed La2O3 is proven to be predominantly controlled by Fowler-Nordheim tunneling process and the hole injection barrier height between ITO and NPB via La2O3 interlayer is estimated to be 0.098 eV. Our experiments provide a feasible application of La2O3 in organic electronic devices with solution process.

Self-cleaning effect in high quality percussion ablating of cooling hole by picosecond ultra-short pulse laser

Science.gov (United States)

Zhao, Wanqin; Yu, Zhishui

2018-06-01

Comparing with the trepanning technology, cooling hole could be processed based on the percussion drilling with higher processing efficiency. However, it is widely believed that the ablating precision of hole is lower for percussion drilling than for trepanning, wherein, the melting spatter materials around the hole surface and the recast layer inside the hole are the two main issues for reducing the ablating precision of hole, especially for the recast layer, it can't be eliminated completely even through the trepanning technology. In this paper, the self-cleaning effect which is a particular property just for percussion ablating of holes has been presented in detail. In addition, the reasons inducing the self-cleaning effect have been discussed. At last, based on the self-cleaning effect of percussion drilling, high quality cooling hole without the melting spatter materials around the hole surface and recast layer inside the hole could be ablated in nickel-based superalloy by picosecond ultra-short pulse laser.

Sol-gel-processed yttrium-doped NiO as hole transport layer in inverted perovskite solar cells for enhanced performance

Science.gov (United States)

Hu, Zijun; Chen, Da; Yang, Pan; Yang, Lijun; Qin, Laishun; Huang, Yuexiang; Zhao, Xiaochong

2018-05-01

In this work, high-performance inverted planar perovskite solar cells (PSCs) using sol-gel processed Y-doped NiO thin films as hole transport layer (HTL) were demonstrated. Y-doped NiO thin films containing different Y doping concentrations were successfully prepared through a simple sol-gel process. The Y doping could significantly improve the electrical conductivity of NiO thin film, and the photovoltaic performance of Y-doped NiO HTL-based PSC devices outperformed that of the pristine NiO HTL-based device. Notably, the PSC using a 5%Y-NiO HTL exhibited the champion performance with an open-circuit voltage (Voc) of 1.00 V, a short circuit current density (Jsc) of 23.82 mA cm-2, a fill factor (FF) of 68% and a power conversion efficiency (PCE) of 16.31%, resulting in a 27.62% enhancement in PCE in comparison with the NiO device. The enhanced performance of the Y-doped NiO device could be attributed to the improved hole mobility, the high quality compact active layer morphology, the more efficient charge extraction from perovskite absorber as well as the lower recombination probability of charge carriers. Thus, this work provides a simple and effective approach to improve the electrical conductivity of p-type NiO thin films for use as a promising HTL in high performance PSCs.

On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes.

Science.gov (United States)

Li, Luping; Zhang, Yonghui; Xu, Shu; Bi, Wengang; Zhang, Zi-Hui; Kuo, Hao-Chung

2017-10-24

The hole injection is one of the bottlenecks that strongly hinder the quantum efficiency and the optical power for deep ultraviolet light-emitting diodes (DUV LEDs) with the emission wavelength smaller than 360 nm. The hole injection efficiency for DUV LEDs is co-affected by the p-type ohmic contact, the p-type hole injection layer, the p-type electron blocking layer and the multiple quantum wells. In this report, we review a large diversity of advances that are currently adopted to increase the hole injection efficiency for DUV LEDs. Moreover, by disclosing the underlying device physics, the design strategies that we can follow have also been suggested to improve the hole injection for DUV LEDs.

A Fast Measuring Method for the Inner Diameter of Coaxial Holes.

Science.gov (United States)

Wang, Lei; Yang, Fangyun; Fu, Luhua; Wang, Zhong; Yang, Tongyu; Liu, Changjie

2017-03-22

A new method for fast diameter measurement of coaxial holes is studied. The paper describes a multi-layer measuring rod that installs a single laser displacement sensor (LDS) on each layer. This method is easy to implement by rotating the measuring rod, and immune from detecting the measuring rod's rotation angles, so all diameters of coaxial holes can be calculated by sensors' values. While revolving, the changing angles of each sensor's laser beams are approximately equal in the rod's radial direction so that the over-determined nonlinear equations of multi-layer holes for fitting circles can be established. The mathematical model of the measuring rod is established, all parameters that affect the accuracy of measurement are analyzed and simulated. In the experiment, the validity of the method is verified, the inner diameter measuring precision of 28 μm is achieved by 20 μm linearity LDS. The measuring rod has advantages of convenient operation and easy manufacture, according to the actual diameters of coaxial holes, and also the varying number of holes, LDS's mounting location can be adjusted for different parts. It is convenient for rapid diameter measurement in industrial use.

Plasma-enhanced atomic-layer-deposited MoO{sub x} emitters for silicon heterojunction solar cells

Energy Technology Data Exchange (ETDEWEB)

Ziegler, Johannes; Schneider, Thomas; Sprafke, Alexander N. [Martin-Luther-University Halle-Wittenberg, mu-MD Group, Institute of Physics, Halle (Germany); Mews, Mathias; Korte, Lars [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, Institute for Silicon-Photovoltaics, Berlin (Germany); Kaufmann, Kai [Fraunhofer Center for Silicon Photovoltaics CSP, Halle (Germany); University of Applied Sciences, Hochschule Anhalt Koethen, Koethen (Germany); Wehrspohn, Ralf B. [Martin-Luther-University Halle-Wittenberg, mu-MD Group, Institute of Physics, Halle (Germany); Fraunhofer Institute for Mechanics of Materials IWM Halle, Halle (Germany)

2015-09-15

A method for the deposition of molybdenum oxide (MoO{sub x}) with high growth rates at temperatures below 200 C based on plasma-enhanced atomic layer deposition is presented. The stoichiometry of the over-stoichiometric MoO{sub x} films can be adjusted by the plasma parameters. First results of these layers acting as hole-selective contacts in silicon heterojunction solar cells are presented and discussed. (orig.)

Use of neutron capture gamma radiation for determining grade of iron ore in blast holes and exploration holes

International Nuclear Information System (INIS)

Eisler, P.L.; Huppert, P.; Mathew, P.J.; Wylie, A.W.; Youl, S.F.

1977-01-01

Neutron radiative capture and neutron-neutron logging have been applied to determining the grade of ore in dry blast holes and a dry exploration hole drilled into a layered iron deposit. Both thermal and epithermal neutron responses were measured as well as the gamma-ray responses due to neutron capture by iron and by hydrogen present in hydrated minerals. The results were fitted by a stepwise multiple linear regression technique to give expressions for mean grade of ore in the drill hole and 95% confidence intervals for estimation of this mean. For an overall range of ore grades of 20-68% Fe and a mean grade of 63% Fe, the confidence interval for prediction of mean grade for the neutron-gamma technique was 0.3% Fe for pooled data from all five blast holes and 0.8% Fe for a single hole. It was also shown that for this type of layered deposit a simpler neutron-neutron log incorporating simultaneous measurement of both thermal and epithermal neutron responses gave almost as good a grade prediction result for pooled results from five drill holes, namely 63+-0.4% Fe, as that obtained by the neutron-gamma technique. The results of both types of log are compared with those obtained by the spectral gamma-ray backscattering [Psub(z)] technique, or by logging of natural gamma radiations from the shale component of the ore. From this comparison conclusions are drawn regarding the most suitable technique to employ for determining grade of iron ore in various practical logging situations. (author)

Hierarchical Model for the Similarity Measurement of a Complex Holed-Region Entity Scene

Directory of Open Access Journals (Sweden)

Zhanlong Chen

2017-11-01

Full Text Available Complex multi-holed-region entity scenes (i.e., sets of random region with holes are common in spatial database systems, spatial query languages, and the Geographic Information System (GIS. A multi-holed-region (region with an arbitrary number of holes is an abstraction of the real world that primarily represents geographic objects that have more than one interior boundary, such as areas that contain several lakes or lakes that contain islands. When the similarity of the two complex holed-region entity scenes is measured, the number of regions in the scenes and the number of holes in the regions are usually different between the two scenes, which complicates the matching relationships of holed-regions and holes. The aim of this research is to develop several holed-region similarity metrics and propose a hierarchical model to measure comprehensively the similarity between two complex holed-region entity scenes. The procedure first divides a complex entity scene into three layers: a complex scene, a micro-spatial-scene, and a simple entity (hole. The relationships between the adjacent layers are considered to be sets of relationships, and each level of similarity measurements is nested with the adjacent one. Next, entity matching is performed from top to bottom, while the similarity results are calculated from local to global. In addition, we utilize position graphs to describe the distribution of the holed-regions and subsequently describe the directions between the holes using a feature matrix. A case study that uses the Great Lakes in North America in 1986 and 2015 as experimental data illustrates the entire similarity measurement process between two complex holed-region entity scenes. The experimental results show that the hierarchical model accounts for the relationships of the different layers in the entire complex holed-region entity scene. The model can effectively calculate the similarity of complex holed-region entity scenes, even if the

Expansible apparatus for removing the surface layer from a concrete object

International Nuclear Information System (INIS)

Allen, C.H.

1979-01-01

A method and apparatus for removing the surface layer from a concrete object are described. The method consists of providing a hole having a circular wall in the surface layer of the object, the hole being at least as deep as the thickness of the surface layer to be removed, and applying an outward wedging pressure on the wall of the hole sufficient to spall the surface layer around the hole. By the proper spacing of an appropriate number of holes, it is possible to remove the entire surface layer. The apparatus consists of an elongated tubular-shaped body having a relatively short handle with a solid wall at one end. The wall of the remainder of the body contains a plurality of evenly spaced longitudinal cuts to form a relatively long expandable section. The outer end of the expandable section has an expandable, wedge-shaped spalling edge extending from the outer surface of the wall, perpendicular to the longitudinal axis of the body, and expanding means in the body for outwardly expanding the expandable section and forcing the spalling edge into the wall of a hole with sufficient outward pressure to spall away the surface layer of concrete. The method and apparatus are particularly suitable for removing surface layers of concrete which are radioactively contaminated

Molecular Doping of the Hole-Transporting Layer for Efficient, Single-Step Deposited Colloidal Quantum Dot Photovoltaics

KAUST Repository

Kirmani, Ahmad R.

2017-07-31

Employment of thin perovskite shells and metal halides as surface-passivants for colloidal quantum dots (CQDs) have been important, recent developments in CQD optoelectronics. These have opened the route to single-step deposited high-performing CQD solar cells. These promising architectures employ a QD hole-transporting layer (HTL) whose intrinsically shallow Fermi level (EF) restricts band-bending at maximum power-point during solar cell operation limiting charge collection. Here, we demonstrate a generalized approach to effectively balance band-edge energy levels of the main CQD absorber and charge-transport layer for these high-performance solar cells. Briefly soaking the QD HTL in a solution of the metal-organic p-dopant, molybdenum tris(1-(trifluoroacetyl)-2-(trifluoromethyl)ethane-1,2-dithiolene), effectively deepens its Fermi level, resulting in enhanced band bending at the HTL:absorber junction. This blocks the back-flow of photo-generated electrons, leading to enhanced photocurrent and fill factor compared to undoped devices. We demonstrate 9.0% perovskite-shelled and 9.5% metal-halide-passivated CQD solar cells, both achieving ca. 10% relative enhancements over undoped baselines.

Dynamic study of a compressed electron layer during the hole-boring stage in a sharp-front laser interaction region

Directory of Open Access Journals (Sweden)

W. P. Wang

2012-08-01

Full Text Available This study investigates the dynamics of a compressed electron layer (CEL when a circularly polarized laser pulse with a sharp front irradiates a high-density foil. A time-dependent model for CEL motion during the hole-boring stage is proposed to describe details of the interaction for any shape of laser pulse. The opacity case, where the laser pulse is totally reflected, is investigated using this model. The results obtained are consistent with the results from particle-in-cell (PIC simulations. A relaxation distance determined by the laser-front steepness is necessary to build a stable CEL state before ions rejoin into the CEL. For the transparent case, the laser-front steepness is important for the formation of the stable CEL state at the back surface of the target. Considering the motion of ions, both the CEL and ion dynamics are important to rebalance the laser pressure and electrostatic charge-separation force as the hole-boring stage changes to the light-sail stage.

Copper(I) Thiocyanate (CuSCN) Hole-Transport Layers Processed from Aqueous Precursor Solutions and Their Application in Thin-Film Transistors and Highly Efficient Organic and Organometal Halide Perovskite Solar Cells

KAUST Repository

Wijeyasinghe, Nilushi

2017-07-28

This study reports the development of copper(I) thiocyanate (CuSCN) hole-transport layers (HTLs) processed from aqueous ammonia as a novel alternative to conventional n-alkyl sulfide solvents. Wide bandgap (3.4–3.9 eV) and ultrathin (3–5 nm) layers of CuSCN are formed when the aqueous CuSCN–ammine complex solution is spin-cast in air and annealed at 100 °C. X-ray photoelectron spectroscopy confirms the high compositional purity of the formed CuSCN layers, while the high-resolution valence band spectra agree with first-principles calculations. Study of the hole-transport properties using field-effect transistor measurements reveals that the aqueous-processed CuSCN layers exhibit a fivefold higher hole mobility than films processed from diethyl sulfide solutions with the maximum values approaching 0.1 cm2 V−1 s−1. A further interesting characteristic is the low surface roughness of the resulting CuSCN layers, which in the case of solar cells helps to planarize the indium tin oxide anode. Organic bulk heterojunction and planar organometal halide perovskite solar cells based on aqueous-processed CuSCN HTLs yield power conversion efficiency of 10.7% and 17.5%, respectively. Importantly, aqueous-processed CuSCN-based cells consistently outperform devices based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate HTLs. This is the first report on CuSCN films and devices processed via an aqueous-based synthetic route that is compatible with high-throughput manufacturing and paves the way for further developments.

Hole distribution in (Sr, Ca, Y, La)14Cu24O41 compounds studies by x-ray absorption and emission spectroscopy

International Nuclear Information System (INIS)

Kabasawa, Eiki; Nakamura, Jin; Yamada, Nobuyoshi; Kuroki, Kazuhiko; Yamazaki, Hisashi; Watanabe, Masamitsu; Denlinger, Jonathan D.; Shin, Shik; Perera, Rupert C.C.

2008-01-01

The polarization dependence of soft x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) near the O 1s absorption edge was measured on two-leg ladder single-crystalline samples of (Sr, Ca, Y, La) 14 Cu 24 O 41 (14-24-41). The hole distributions in 14-24-41 compounds are determined by polarization analysis. For samples with less than or equal to 5 holes/chemical formula (c.f.), all holes reside on the edge-shared chain layer. In the case of Sr 14-x Ca x Cu 24 O 41 (6 holes/c.f.), there is approximately one hole on the two-leg ladder layer, with about five holes remaining on the edge-shared chain layer. By Ca substitution for Sr in the Sr 14-x Ca x Cu 24 O 41 samples, 0.3 holes transfer from the edge-shared chain to the two-leg ladder layer. It is possible that some of the holes on the two-leg ladder layer move from the rung sites to the leg sites upon Ca substitution. (author)

Improvement of the photovoltaic parameters of perovskite solar cells using a reduced-graphene-oxide-modified titania layer and soluble copper phthalocyanine as a hole transporter.

Science.gov (United States)

Nouri, Esmaiel; Mohammadi, Mohammad Reza; Xu, Zong-Xiang; Dracopoulos, Vassilios; Lianos, Panagiotis

2018-01-24

Functional perovskite solar cells can be made by using a simple, inexpensive and stable soluble tetra-n-butyl-substituted copper phthalocyanine (CuBuPc) as a hole transporter. In the present study, TiO 2 /reduced graphene oxide (T/RGO) hybrids were synthesized via an in situ solvothermal process and used as electron acceptor/transport mediators in mesoscopic perovskite solar cells based on soluble CuBuPc as a hole transporter and on graphene oxide (GO) as a buffer layer. The impact of the RGO content on the optoelectronic properties of T/RGO hybrids and on the solar cell performance was studied, suggesting improved electron transport characteristics and photovoltaic parameters. An enhanced electron lifetime and recombination resistance led to an increase in the short circuit current density, open circuit voltage and fill factor. The device based on a T/RGO mesoporous layer with an optimal RGO content of 0.2 wt% showed 22% higher photoconversion efficiency and higher stability compared with pristine TiO 2 -based devices.

Solid Catalyst with Ionic Liquid Layer (SCILL). A concept to improve the selectivity of selective hydrogenations

Energy Technology Data Exchange (ETDEWEB)

Jess, A.; Korth, W. [Bayreuth Univ. (Germany). Chair of Chemical Engineering

2011-07-01

Catalytic hydrogenations are important for refinery processes, petrochemical applications as well as for numerous processes of the fine chemicals industry. In some cases, hydrogenations consist of a sequence of consecutive reactions, and the desired product is the intermediate. An important goal is then a high yield and selectivity to the intermediate, if possible at a high conversion degree. The selectivity to an intermediate primarily depends on the chemical nature of the catalyst, but may also be influenced by diffusion processes. Ionic liquids (ILs) are low melting salts (< 100 C) and represent a promising solvent class. This paper focuses on the concept of a Solid Catalyst with Ionic Liquid Layer (SCILL), where the solid catalyst is coated with a thin IL layer to improve the selectivity. (orig.)

Mechanism of Cuticle Hole Development in Human Hair Due to UV-Radiation Exposure

Directory of Open Access Journals (Sweden)

Kazuhisa Maeda

2018-03-01

Full Text Available Hair is easily damaged by ultraviolet (UV radiation, bleaching agents or permanent wave treatments, and as damage progresses, hair loses its gloss, develops split ends and breaks. However, the causes of hair damage due to UV radiation have not yet been clarified. We discovered that in one mechanism facilitating damage to wet hair by UV radiation, the unsaturated fatty acids in wet hair produce hydroxy radicals upon exposure to UV radiation, and these radicals produce cuticle holes between the cuticle layers. In wet hair exposed to UV radiation, cuticle holes were produced only between the cuticle layers, whereas when human hair was immersed in a solution containing hydroxy radicals produced by Fenton’s reaction, a random production of cuticle holes was noted. It is thought that hydroxy radicals are produced only between the cuticle layers by exposure to UV radiation, and cuticle holes are formed only in this region because one of the polyunsaturated fatty acids, linoleic acid, with a bis-allyl hydrogen, is found between the cuticle layers.

Effect of Boundary-Layer Bleed Hole Inclination Angle and Scaling on Flow Coefficient Behavior

Science.gov (United States)

Eichorn, Michael B.; Barnhart, Paul J.; Davis, David O.; Vyas, Manan A.; Slater, John W.

2013-01-01

Phase II data results of the Fundamental Inlet Bleed Experiments study at NASA Glenn Research Center are presented which include flow coefficient behavior for 21 bleed hole configurations. The bleed configurations are all round holes with hole diameters ranging from 0.795 to 6.35 mm, hole inclination angles from 20deg to 90deg, and thickness-to-diameter ratios from 0.25 to 2.0. All configurations were tested at a unit Reynolds number of 2.46 10(exp 7)/m and at discrete local Mach numbers of 1.33, 1.62, 1.98, 2.46, and 2.92. Interactions between the design parameters of hole diameter, hole inclination angle, and thickness-to-diameter as well as the interactions between the flow parameters of pressure ratio and Mach number upon the flow coefficient are examined, and a preliminary statistical model is proposed. An existing correlation is also examined with respect to this data.

Black holes as possible sources of closed and semiclosed worlds

International Nuclear Information System (INIS)

Frolov, V.P.; Markov, M.A.; Mukhanov, V.F.

1990-01-01

The internal structure of spacetime inside a black hole is investigated on the assumption that some limiting curvature exists. It is shown that the Schwarzschild metric inside the black hole can be attached to the de Sitter one at some spacelike junction surface which may represent a short transition layer. The method of massive thin shells by Israel is used to obtain the characteristics of this layer. It is shown that instead of the singularity the closed world can be formed inside the black hole. It is argued that this property of our model may also be valid in a more general case provided the gravitation theory is asymptotically free and the limiting curvature exists. After passing the deflation stage the closed world in the black-hole interior may begin to inflate and give rise to a new macroscopic universe. The described model may be considered as an example of the creation of a closed or semiclosed world ''in the laboratory.'' The possible fate of the evaporating black hole is also briefly discussed

Role of 4-tert-Butylpyridine as a Hole Transport Layer Morphological Controller in Perovskite Solar Cells.

Science.gov (United States)

Wang, Shen; Sina, Mahsa; Parikh, Pritesh; Uekert, Taylor; Shahbazian, Brian; Devaraj, Arun; Meng, Ying Shirley

2016-09-14

Hybrid organic-inorganic materials for high-efficiency, low-cost photovoltaic devices have seen rapid progress since the introduction of lead based perovskites and solid-state hole transport layers. Although majority of the materials used for perovskite solar cells (PSC) are introduced from dye-sensitized solar cells (DSSCs), the presence of a perovskite capping layer as opposed to a single dye molecule (in DSSCs) changes the interactions between the various layers in perovskite solar cells. 4-tert-Butylpyridine (tBP), commonly used in PSCs, is assumed to function as a charge recombination inhibitor, similar to DSSCs. However, the presence of a perovskite capping layer calls for a re-evaluation of its function in PSCs. Using TEM (transmission electron microscopy), we first confirm the role of tBP as a HTL morphology controller in PSCs. Our observations suggest that tBP significantly improves the uniformity of the HTL and avoids accumulation of Li salt. We also study degradation pathways by using FTIR (Fourier transform infrared spectroscopy) and APT (atom probe tomography) to investigate and visualize in 3-dimensions the moisture content associated with the Li salt. Long-term effects, over 1000 h, due to evaporation of tBP have also been studied. Based on our findings, a PSC failure mechanism associated with the morphological change of the HTL is proposed. tBP, the morphology controller in HTL, plays a key role in this process, and thus this study highlights the need for additive materials with higher boiling points for consistent long-term performance of PSCs.

Nondispersive hole transport in a spin-coated dendrimer film measured by the charge-generation-layer time-of-flight method

Science.gov (United States)

Markham, Jonathan P. J.; Anthopoulos, Thomas D.; Samuel, Ifor D. W.; Richards, Gary J.; Burn, Paul L.; Im, Chan; Bassler, Heinz

2002-10-01

Measurements of the mobility of a first-generation (G1) bis-fluorene cored dendrimer have been performed on spin-coated samples of 500 nm thickness using the charge-generation-layer time-of-flight (TOF) technique. A 10 nm perylene charge generation layer was excited by the 532 nm line of a Q-switched Nd:YAG laser and the generated carriers swept through the dendrimer film under an applied field. We observe nondispersive hole transport in the dendrimer layer with a room-temperature mobility mu=2.0 x10-4 cm2/V s at a field of 0.55 MV/cm. There is a weak field dependence of the mobility and it increases from mu=1.6 x10-4 cm2/V s at 0.2 MV/cm to mu=3.0 x10-4 cm2/V s at 1.4 MV/cm. These results suggest that the measurement of mobility by TOF in spin-coated samples on thickness scales relevant to organic light-emitting diodes can yield valuable information, and that dendrimers are promising materials for device applications.

Graded Heterojunction Engineering for Hole-Conductor-Free Perovskite Solar Cells with High Hole Extraction Efficiency and Conductivity.

Science.gov (United States)

Li, Bo; Zhang, Yanan; Zhang, Luyuan; Yin, Longwei

2017-10-01

Despite great progress in the photovoltaic conversion efficiency (PCE) of inorganic-organic hybrid perovskite solar cells (PSCs), the large-scale application of PSCs still faces serious challenges due to the poor-stability and high-cost of the spiro-OMeTAD hole transport layer (HTL). It is of great fundamental importance to rationally address the issues of hole extraction and transfer arising from HTL-free PSCs. Herein, a brand-new PSC architecture is designed by introducing multigraded-heterojunction (GHJ) inorganic perovskite CsPbBr x I 3- x layers as an efficient HTL. The grade adjustment can be achieved by precisely tuning the halide proportion and distribution in the CsPbBr x I 3- x film to reach an optimal energy alignment of the valance and conduction band between MAPbI 3 and CsPbBr x I 3- x . The CsPbBr x I 3- x GHJ as an efficient HTL can induce an electric field where a valance/conduction band edge is leveraged to bend at the heterojunction interface, boosting the interfacial electron-hole splitting and photoelectron extraction. The GHJ architecture enhances the hole extraction and conduction efficiency from the MAPbI 3 to the counter electrode, decreases the recombination loss during the hole transfer, and benefits in increasing the open-circuit voltage. The optimized HTL-free PCS based on the GHJ architecture demonstrates an outstanding thermal stability and a significantly improved PCE of 11.33%, nearly 40% increase compared with 8.16% for pure HTL-free devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of PDMS through-holes using the MIMIC method and the surface treatment by atmospheric-pressure CH4/He RF plasma

Science.gov (United States)

Choi, Jongchan; Lee, Kyeong-Hwan; Yang, Sung

2011-09-01

This note presents a simple fabrication process for patterning micro through-holes in a PDMS layer by a combination of the micromolding in capillaries (MIMIC) method and the surface treatment by atmospheric-pressure CH4/He RF plasma. The fabrication process is confirmed by forming micro through-holes with various shapes including circle, C-shape, open microfluidic channel and hemisphere. All micro through-holes of various shapes in a wide range of diameters and heights are well fabricated by the proposed method. Also, a 3D micromixer containing a PDMS micro through-hole layer formed by the proposed method is built and its performance is tested as another practical demonstration of the proposed fabrication method. Therefore, we believe that the proposed fabrication process will build a PDMS micro through-hole layer in a simple and easy way and will contribute to developing highly efficient multi-layered microfluidic systems, which may require PDMS micro through-hole layers.

Improved hole-injection and power efficiency of organic light-emitting diodes using an ultrathin cerium fluoride buffer layer

Science.gov (United States)

Lu, Hsin-Wei; Kao, Po-Ching; Chu, Sheng-Yuan

2016-09-01

In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a CeF3 film as an ultra-thin buffer layer between the ITO and NPB hole transport layer, with the structure configuration ITO/CeF3 (1 nm)/NPB (40 nm)/Alq3 (60 nm)/LiF (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated via several approaches. The work function increased from 4.8 eV (standard ITO electrode) to 5.2 eV (1-nm-thick UV-ozone treated CeF3 film deposited on the ITO electrode). The turn-on voltage decreased from 4.2 V to 4.0 V at 1 mA/cm2, the luminance increased from 7588 cd/m2 to 10820 cd/m2, and the current efficiency increased from 3.2 cd/A to 3.5 cd/A when the 1-nm-thick UV-ozone treated CeF3 film was inserted into the OLEDs.

Observation of plasma hole in a rotating plasma

International Nuclear Information System (INIS)

Nagaoka, Kenichi; Ishihara, Tatsuzo; Okamoto, Atsushi; Yoshimura, Shinji; Tanaka, Masayoshi Y.

2001-01-01

Plasma hole, a cylindrical density cavity, formed in a rotating plasma has been investigated experimentally. The plasma hole is characterized by large aspect ratio (length/radius ≥ 30), steep boundary layer between the hole and the ambient plasma (10 ion Larmor radius), and extremely high positive potential (130 V). The flow velocity field associated with plasma hole structure has been measured, and is found to have interesting features: (1) plasma rotates in azimuthal direction at a maximum velocity of order of ion sound speed, (2) plasma flows radially inward across the magnetic field line, (3) there present an axial flow reversal between core and peripheral region. It is found that the flow pattern of the plasma hole is very similar to the that of well-developed typhoon with core. (author)

Numerical simulation and experimental validation of inverted planar perovskite solar cells based on NiOx hole transport layer

Science.gov (United States)

Wei, Xiaoqing; Wang, Xian; Jiang, Hailong; Huang, Yongliang; Han, Anjun; Gao, Qi; Bian, Jiantao; Liu, Zhengxin

2017-12-01

Numerical simulation of inverted planar perovskite solar cells based on NiOx hole transport layer was performed with AMPS-1D program. The simulated device parameters were shown to agree well with our experimental work. The simulated results revealed that the device contained typical p-i-n junction configuration. The optimum thickness of the absorber, the effects of the absorber quality, the defect density of interfaces, the effects of VBO and CBO, the interface contact at front and back electrodes were analyzed. Open-circuit voltage mainly depended on the defect density in CH3NH3PbI3 layer, the recombination at HTL/CH3NH3PbI3 and ETL/CH3NH3PbI3 interface, the values of VBO and CBO, while short-circuit current mainly depended on the thickness of CH3NH3PbI3 layer. Fill factor was significantly influenced by the interface contact at front and back electrodes. Remarkably, a power conversion efficiency of 21.8% is obtained under optimised conditions. Real devices with PCE of up to 15% were obtained by initially optimizing the preparation of CH3NH3PbI3 absorber layer. Our work can provide some important guidance for device design and optimization from the considerations of both theory and experiment.

Characterization of Organic Thin Film Solar Cells of PCDTBT : PC71BM Prepared by Different Mixing Ratio and Effect of Hole Transport Layer

Directory of Open Access Journals (Sweden)

Vijay Srinivasan Murugesan

2015-01-01

Full Text Available The organic thin film solar cells (OTFSCs have been successfully fabricated using PCDTBT : PC71BM with different mixing ratios (1 : 1 to 1 : 8 and the influence of hole transport layer thickness (PEDOT : PSS. The active layers with different mixing ratios of PCDTBT : PC71BM have been fabricated using o-dichlorobenzene (o-DCB. The surface morphology of the active layers and PEDOT : PSS layer with different thicknesses were characterized by AFM analysis. Here, we report that the OTFSCs with high performance have been optimized with 1 : 4 ratios of PCDTBT : PC71BM. The power conversion efficiency (PCE = 5.17% of the solar cells was significantly improved by changing thickness of PEDOT : PSS layer. The thickness of the PEDOT : PSS layer was found to be of significant importance; the thickness of the PEDOT : PSS layer at 45 nm (higher spin speed 5000 rpm shows higher short circuit current density (Jsc and lower series resistance (Rs and higher PCE.

Tetra-methyl substituted copper (II) phthalocyanine as a hole injection enhancer in organic light-emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Wang, Yu-Long; Xu, Jia-Ju; Lin, Yi-Wei; Chen, Qian; Shan, Hai-Quan; Xu, Zong-Xiang, E-mail: xu.zx@sustc.edu.cn, E-mail: val.roy@cityu.edu.hk [Department of Chemistry, South University of Science and Technology of China, Shenzhen, Guangdong, P. R. China, 518055 (China); Yan, Yan; Roy, V. A. L., E-mail: xu.zx@sustc.edu.cn, E-mail: val.roy@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (Hong Kong)

2015-10-15

We have enhanced hole injection and lifetime in organic light-emitting diodes (OLEDs) by incorporating the isomeric metal phthalocyanine, CuMePc, as a hole injection enhancer. The OLED devices containing CuMePc as a hole injection layer (HIL) exhibited higher luminous efficiency and operational lifetime than those using a CuPc layer and without a HIL. The effect of CuMePc thickness on device performance was investigated. Atomic force microscope (AFM) studies revealed that the thin films were smooth and uniform because the mixture of CuMePc isomers depressed crystallization within the layer. This may have caused the observed enhanced hole injection, indicating that CuMePc is a promising HIL material for highly efficient OLEDs.

Tetra-methyl substituted copper (II phthalocyanine as a hole injection enhancer in organic light-emitting diodes

Directory of Open Access Journals (Sweden)

Yu-Long Wang

2015-10-01

Full Text Available We have enhanced hole injection and lifetime in organic light-emitting diodes (OLEDs by incorporating the isomeric metal phthalocyanine, CuMePc, as a hole injection enhancer. The OLED devices containing CuMePc as a hole injection layer (HIL exhibited higher luminous efficiency and operational lifetime than those using a CuPc layer and without a HIL. The effect of CuMePc thickness on device performance was investigated. Atomic force microscope (AFM studies revealed that the thin films were smooth and uniform because the mixture of CuMePc isomers depressed crystallization within the layer. This may have caused the observed enhanced hole injection, indicating that CuMePc is a promising HIL material for highly efficient OLEDs.

Micro-hole array fluorescent sensor based on AC-Dielectrophoresis (DEP) for simultaneous analysis of nano-molecules

Science.gov (United States)

Kim, Hye Jin; Kang, Dong-Hoon; Lee, Eunji; Hwang, Kyo Seon; Shin, Hyun-Joon; Kim, Jinsik

2018-02-01

We propose a simple fluorescent bio-chip based on two types of alternative current-dielectrophoretic (AC-DEP) force, attractive (positive DEP) and repulsive (negative DEP) force, for simultaneous nano-molecules analysis. Various radius of micro-holes on the bio-chip are designed to apply the different AC-DEP forces, and the nano-molecules are concentrated inside the micro-hole arrays according to the intensity of the DEP force. The bio-chip was fabricated by Micro Electro Mechanical system (MEMS) technique, and was composed of two layers; a SiO2 layer and Ta/Pt layer were accomplished for an insulation layer and a top electrode with micro-hole arrays to apply electric fields for DEP force, respectively. Each SiO2 and Ta/Pt layers were deposited by thermal oxidation and sputtering, and micro-hole arrays were fabricated with Inductively Coupled Plasma (ICP) etching process. For generation of each positive and negative DEP at micro-holes, we applied two types of sine-wave AC voltage with different frequency range alternately. The intensity of the DEP force was controlled by the radius of the micro-hole and size of nano-molecule, and calculated with COMSOL multi-physics. Three types of nano-molecules labelled with different fluorescent dye were used and the intensity of nano-molecules was examined by the fluorescent optical analysis after applying the DEP force. By analyzing the fluorescent intensities of the nano-molecules, we verify the various nano-molecules in analyte are located successfully inside corresponding micro-holes with different radius according to their size.

Simple measuring rod method for the coaxiality of serial holes

Science.gov (United States)

Wang, Lei; Yang, Tongyu; Wang, Zhong; Ji, Yuchen; Liu, Changjie; Fu, Luhua

2017-11-01

Aiming at the rapid coaxiality measurement of serial hole part with a small diameter, a coaxiality measuring rod for each layer hole with a single LDS (laser displacement sensor) is proposed. This method does not require the rotation angle information of the rod, and the coaxiality of serial holes can be calculated from the measured values of LDSs after randomly rotating the measuring rod several times. With the mathematical model of the coaxiality measuring rod, each factor affecting the accuracy of coaxiality measurement is analyzed by simulation, and the installation accuracy requirements of the measuring rod and LDSs are presented. In the tolerance of a certain installation error of the measuring rod, the relative center of the hole is calculated by setting the over-determined nonlinear equations of the fitting circles of the multi-layer holes. In experiment, coaxiality measurement accuracy is realized by a 16 μm precision LDS, and the validity of the measurement method is verified. The manufacture and measurement requirements of the coaxiality measuring rod are low, by changing the position of LDSs in the measuring rod, the serial holes with different sizes and numbers can be measured. The rapid coaxiality measurement of parts can be easily implemented in industrial sites.

PIV measurements in the near wakes of hollow cylinders with holes

Science.gov (United States)

Firat, Erhan; Ozkan, Gokturk M.; Akilli, Huseyin

2017-05-01

The wake flows behind fixed, hollow, rigid circular cylinders with two rows of holes connecting the front and rear stagnation lines were investigated using particle image velocimetry (PIV) for various combinations of three hole diameters, d = 0.1 D, 0.15 D, and 0.20 D, six hole-to-hole distances, l = 2 d, 3 d, 4 d, 5 d, 6 d, and 7 d, and ten angles of incidence ( α), from 0° to 45° in steps of 5°, at a Reynolds number of Re = 6,900. Time-averaged velocity distributions, instantaneous and time-averaged vorticity patterns, time-averaged streamline topology, and hot spots of turbulent kinetic energy occurred through the interaction of shear layers from the models were presented to show how the wake flow was modified by the presence of the self-issuing jets with various momentums emanating from the downstream holes. In general, as hole diameter which is directly related to jet momentum increased, the values of time-averaged wake characteristics (length of time-averaged recirculation region, vortex formation length, length of shear layers, and gap between the shear layers) increased. Irrespective to d and l tested, the values of the vortex formation length of the models are greater than that of the cylinder without hole (reference model). That is, vortex formation process was shifted downstream by aid of jets. It was found that time-averaged wake characteristics were very sensitive to α. As α increased, the variation of these characteristics can be modeled by exponential decay functions. The effect of l on the three-dimensional vortex shedding patterns in the near wake of the models was also discussed.

Selection bias in dynamically measured supermassive black hole samples: scaling relations and correlations between residuals in semi-analytic galaxy formation models

Science.gov (United States)

Barausse, Enrico; Shankar, Francesco; Bernardi, Mariangela; Dubois, Yohan; Sheth, Ravi K.

2017-07-01

Recent work has confirmed that the scaling relations between the masses of supermassive black holes and host-galaxy properties such as stellar masses and velocity dispersions may be biased high. Much of this may be caused by the requirement that the black hole sphere of influence must be resolved for the black hole mass to be reliably estimated. We revisit this issue with a comprehensive galaxy evolution semi-analytic model. Once tuned to reproduce the (mean) correlation of black hole mass with velocity dispersion, the model cannot account for the correlation with stellar mass. This is independent of the model's parameters, thus suggesting an internal inconsistency in the data. The predicted distributions, especially at the low-mass end, are also much broader than observed. However, if selection effects are included, the model's predictions tend to align with the observations. We also demonstrate that the correlations between the residuals of the scaling relations are more effective than the relations themselves at constraining models for the feedback of active galactic nuclei (AGNs). In fact, we find that our model, while in apparent broad agreement with the scaling relations when accounting for selection biases, yields very weak correlations between their residuals at fixed stellar mass, in stark contrast with observations. This problem persists when changing the AGN feedback strength, and is also present in the hydrodynamic cosmological simulation Horizon-AGN, which includes state-of-the-art treatments of AGN feedback. This suggests that current AGN feedback models are too weak or simply not capturing the effect of the black hole on the stellar velocity dispersion.

Simulation of polarization-dependent film with subwavelength nano-hole array

Science.gov (United States)

Yu, Yue; Wei, Dong; Long, Huabao; Xin, Zhaowei; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

When lightwave passes through a metal thin film with a periodic subwavelength hole arrays structure, its transmittance is significantly improved in the partial band compared to other wavelength. Changing the size of the hole, the period or metal material, will make the transmission curve different. Here, we add a layer of dielectric material on the surface of the metal film, such as liquid crystal(LC), by controlling voltage on LC to change the refractive index of this layer, then we can change the transmission curve, and achieve using voltage to move the transmission curve. When there is need for polarization, the holes can be made of a rectangle whose length and width are different or other shapes, for different polarization state of the light, and the film will display different transmission characteristics.

Selection of peripheral intravenous catheters with 24-gauge side-holes versus those with 22-gauge end-hole for MDCT: A prospective randomized study

Energy Technology Data Exchange (ETDEWEB)

Tamura, Akio, E-mail: a.akahane@gmail.com [Department of Radiology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka 020-8505 (Japan); Kato, Kenichi, E-mail: kkato@iwate-med.ac.jp [Department of Radiology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka 020-8505 (Japan); Kamata, Masayoshi, E-mail: kamataaoi@yahoo.co.jp [Iwate Medical University Hospital, 19-1 Uchimaru, Morioka 020-8505 (Japan); Suzuki, Tomohiro, E-mail: suzukitomohiro123@gmail.com [Department of Radiology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka 020-8505 (Japan); Suzuki, Michiko, E-mail: mamimichiko@me.com [Department of Radiology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka 020-8505 (Japan); Nakayama, Manabu, E-mail: gakuymgt@yahoo.co.jp [Department of Radiology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka 020-8505 (Japan); Tomabechi, Makiko, E-mail: mtomabechi@mac.com [Department of Radiology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka 020-8505 (Japan); Nakasato, Tatsuhiko, E-mail: nakasato77@gmail.com [Department of Radiology, Southern Tohoku Research Institute for Neuroscience, 7-115 Yatsuyamada, Koriyama 963-8563 (Japan); Ehara, Shigeru, E-mail: ehara@iwate-med.ac.jp [Department of Radiology, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka 020-8505 (Japan)

2017-02-15

Highlights: • We compared 24-gauge side-hole and conventional 22-gauge end-hole catheters in MDCT. • The 24-gauge side-hole catheter is noninferior to the 22-gauge end-hole catheter. • The 24-gauge side-hole catheter is safe and facilitates optimal enhancement quality. • The 24-gauge side-hole catheter is suitable for patients with narrow or fragile veins. - Abstract: Purpose: To compare the 24-gauge side-holes catheter and conventional 22-gauge end-hole catheter in terms of safety, injection pressure, and contrast enhancement on multi-detector computed tomography (MDCT). Materials & methods: In a randomized single-center study, 180 patients were randomized to either the 24-gauge side-holes catheter or the 22-gauge end-hole catheter groups. The primary endpoint was safety during intravenous administration of contrast material for MDCT, using a non-inferiority analysis (lower limit 95% CI greater than −10% non-inferiority margin for the group difference). The secondary endpoints were injection pressure and contrast enhancement. Results: A total of 174 patients were analyzed for safety during intravenous contrast material administration for MDCT. The overall extravasation rate was 1.1% (2/174 patients); 1 (1.2%) minor episode occurred in the 24-gauge side-holes catheter group and 1 (1.1%) in the 22-gauge end-hole catheter group (difference: 0.1%, 95% CI: −3.17% to 3.28%, non-inferiority P = 1). The mean maximum pressure was higher with the 24-gauge side-holes catheter than with the 22-gauge end-hole catheter (8.16 ± 0.95 kg/cm{sup 2} vs. 4.79 ± 0.63 kg/cm{sup 2}, P < 0.001). The mean contrast enhancement of the abdominal aorta, celiac artery, superior mesenteric artery, and pancreatic parenchyma in the two groups were not significantly different. Conclusion: In conclusion, our study showed that the 24-gauge side-holes catheter is safe and suitable for delivering iodine with a concentration of 300 mg/mL at a flow-rate of 3 mL/s, and it may contribute to

The role of the hole-extraction layer in determining the operational stability of a polycarbazole:fullerene bulk-heterojunction photovoltaic device

Science.gov (United States)

Bovill, E.; Scarratt, N.; Griffin, J.; Yi, H.; Iraqi, A.; Buckley, A. R.; Kingsley, J. W.; Lidzey, D. G.

2015-02-01

We have made a comparative study of the relative operational stability of bulk-heterojunction organic photovoltaic (OPV) devices utilising different hole transport layers (HTLs). OPV devices were fabricated based on a blend of the polymer PCDTBT with the fullerene PC70BM, and incorporated the different HTL materials PEDOT:PSS, MoOx and V2O5. Following 620 h of irradiation by light from a solar simulator, we find that devices using the PEDOT:PSS HTL retained the highest efficiency, having a projected T80 lifetime of 14 500 h.

Formation of conductive spontaneous via holes in AlN buffer layer on n+Si substrate by filling the vias with n-AlGaN by metal organic chemical vapor deposition and application to vertical deep ultraviolet photo-sensor

Directory of Open Access Journals (Sweden)

N. Kurose

2014-12-01

Full Text Available We have grown conductive aluminum nitride (AlN layers using the spontaneous via holes formation technique on an n+-Si substrate for vertical-type device fabrication. The size and density of the via holes are controlled through the crystal growth conditions used for the layer, and this enables the conductance of the layer to be controlled. Using this technique, we demonstrate the fabrication of a vertical-type deep ultraviolet (DUV photo-sensor. This technique opens up the possibility of fabrication of monolithically integrated on-chip DUV sensors and DUV light-emitting devices (LEDs, including amplifiers, controllers and other necessary functional circuits, on a Si substrate.

Coulomb drag in electron-hole bilayer: Mass-asymmetry and exchange correlation effects

Science.gov (United States)

Arora, Priya; Singh, Gurvinder; Moudgil, R. K.

2018-04-01

Motivated by a recent experiment by Zheng et al. [App. Phys. Lett. 108, 062102 (2016)] on coulomb drag in electron-hole and hole-hole bilayers based on GaAs/AlGaAs semiconductor heterostructure, we investigate theoretically the influence of mass-asymmetry and temperature-dependence of correlations on the drag rate. The correlation effects are dealt with using the Vignale-Singwi effective inter-layer interaction model which includes correlations through local-field corrections to the bare coulomb interactions. However, in this work, we have incorporated only the intra-layer correlations using the temperature-dependent Hubbard approximation. Our results display a reasonably good agreement with the experimental data. However, it is crucial to include both the electron-hole mass-asymmetry and temperature-dependence of correlations. Mass-asymmetry and correlations are found to result in a substantial enhancement of drag resistivity.

Hole injection enhancement in organic light emitting devices using plasma treated graphene oxide

Energy Technology Data Exchange (ETDEWEB)

Jesuraj, P. Justin; Parameshwari, R. [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu (India); Kanthasamy, K.; Koch, J. [Institut für Festkörperphysik, ATMOS, Appelstr. 2, D-30167, Hannover (Germany); Pfnür, H. [Institut für Festkörperphysik, ATMOS, Appelstr. 2, D-30167, Hannover (Germany); Laboratorium für Nano- und Quantene$ngineering, Schneiderberg 30, D-30167, Hannover (Germany); Jeganathan, K., E-mail: kjeganathan@yahoo.com [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli, 620 024, Tamil Nadu (India)

2017-03-01

Graphical abstract: Plasma treated Graphene oxide for hole injection enhancement in OLEDs. - Highlights: • Oxygen (O{sub 2}) and hydrogen (H{sub 2}) plasma exposed graphene oxide (GO) sheets have been demonstrated as hole buffer layers in OLEDs. • O{sub 2} plasma exposure induces assimilation of oxygen contents in GO lattice resulting in improved work function that reduced the hole injection barrier further. Whereas, H{sub 2} plasma contrastingly reduced the GO by excluding oxygen which ensuing lower work function. • X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy investigations reveal the capricious amount of oxygen in GO lattice and its corresponding work function variations. • GO and O{sub 2} plasma treated GO significantly improves the current efficiency of OLEDs more than one order with notable reduction in turn on voltage. - Abstract: The hole injection layer (HIL) with high work function (WF) is desirable to reduce the injection barrier between anode and hole transport layer in organic light emitting devices (OLED). Here, we report a novel approach to tune the WF of graphene oxide (GO) using oxygen and hydrogen plasma treatment and its hole injection properties in OLEDs. The mild exposure of oxygen plasma on GO (O{sub 2}-GO) significantly reduces the injection barrier by increasing the WF of anode (4.98 eV) through expansion of C−O bonds. In contrast, the hole injection barrier was drastically increased for hydrogen plasma treated GO (H{sub 2}-GO) layers as the WF is lowered by the contraction of C−O bond. By employing active O{sub 2}-GO as HIL in OLEDs found to exhibit superior current efficiency of 4.2 cd/A as compared to 3.3 cd/A for pristine GO. Further, the high injection efficiency of O{sub 2}-GO infused hole only device can be attributed to the improved energy level matching. Ultraviolet and X-ray photoelectron spectroscopy were used to correlate the WF of HIL infused anode towards the enhanced performance of

Hole-transport material variation in fully vacuum deposited perovskite solar cells

Energy Technology Data Exchange (ETDEWEB)

Polander, Lauren E.; Pahner, Paul; Schwarze, Martin; Saalfrank, Matthias; Koerner, Christian; Leo, Karl, E-mail: karl.leo@iapp.de [Institut für Angewandte Photophysik, Technische Universität Dresden, 01069 Dresden (Germany)

2014-08-01

This work addresses the effect of energy level alignment between the hole-transporting material and the active layer in vacuum deposited, planar-heterojunction CH{sub 3}NH{sub 3}PbI{sub x−3}Cl{sub x} perovskite solar cells. Through a series of hole-transport materials, with conductivity values set using controlled p-doping of the layer, we correlate their ionization potentials with the open-circuit voltage of the device. With ionization potentials beyond 5.3 eV, a substantial decrease in both current density and voltage is observed, which highlights the delicate energetic balance between driving force for hole-extraction and maximizing the photovoltage. In contrast, when an optimal ionization potential match is found, the open-circuit voltage can be maximized, leading to power conversion efficiencies of up to 10.9%. These values are obtained with hole-transport materials that differ from the commonly used Spiro-MeO-TAD and correspond to a 40% performance increase versus this reference.

Hole-transport material variation in fully vacuum deposited perovskite solar cells

Directory of Open Access Journals (Sweden)

Lauren E. Polander

2014-08-01

Full Text Available This work addresses the effect of energy level alignment between the hole-transporting material and the active layer in vacuum deposited, planar-heterojunction CH3NH3PbIx−3Clx perovskite solar cells. Through a series of hole-transport materials, with conductivity values set using controlled p-doping of the layer, we correlate their ionization potentials with the open-circuit voltage of the device. With ionization potentials beyond 5.3 eV, a substantial decrease in both current density and voltage is observed, which highlights the delicate energetic balance between driving force for hole-extraction and maximizing the photovoltage. In contrast, when an optimal ionization potential match is found, the open-circuit voltage can be maximized, leading to power conversion efficiencies of up to 10.9%. These values are obtained with hole-transport materials that differ from the commonly used Spiro-MeO-TAD and correspond to a 40% performance increase versus this reference.

Selection of hidden layer nodes in neural networks by statistical tests

International Nuclear Information System (INIS)

Ciftcioglu, Ozer

1992-05-01

A statistical methodology for selection of the number of hidden layer nodes in feedforward neural networks is described. The method considers the network as an empirical model for the experimental data set subject to pattern classification so that the selection process becomes a model estimation through parameter identification. The solution is performed for an overdetermined estimation problem for identification using nonlinear least squares minimization technique. The number of the hidden layer nodes is determined as result of hypothesis testing. Accordingly the redundant network structure with respect to the number of parameters is avoided and the classification error being kept to a minimum. (author). 11 refs.; 4 figs.; 1 tab

A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies. II. The SDSS DR7 Sample

Science.gov (United States)

Liu, He-Yang; Yuan, Weimin; Dong, Xiao-Bo; Zhou, Hongyan; Liu, Wen-Juan

2018-04-01

A new sample of 204 low-mass black holes (LMBHs) in active galactic nuclei (AGNs) is presented with black hole masses in the range of (1–20) × 105 M ⊙. The AGNs are selected through a systematic search among galaxies in the Seventh Data Release (DR7) of the Sloan Digital Sky Survey (SDSS), and careful analyses of their optical spectra and precise measurement of spectral parameters. Combining them with our previous sample selected from SDSS DR4 makes it the largest LMBH sample so far, totaling over 500 objects. Some of the statistical properties of the combined LMBH AGN sample are briefly discussed in the context of exploring the low-mass end of the AGN population. Their X-ray luminosities follow the extension of the previously known correlation with the [O III] luminosity. The effective optical-to-X-ray spectral indices α OX, albeit with a large scatter, are broadly consistent with the extension of the relation with the near-UV luminosity L 2500 Å. Interestingly, a correlation of α OX with black hole mass is also found, with α OX being statistically flatter (stronger X-ray relative to optical) for lower black hole masses. Only 26 objects, mostly radio loud, were detected in radio at 20 cm in the FIRST survey, giving a radio-loud fraction of 4%. The host galaxies of LMBHs have stellar masses in the range of 108.8–1012.4 M ⊙ and optical colors typical of Sbc spirals. They are dominated by young stellar populations that seem to have undergone continuous star formation history.

Interfacial Passivation of the p-Doped Hole-Transporting Layer Using General Insulating Polymers for High-Performance Inverted Perovskite Solar Cells.

Science.gov (United States)

Zhang, Fan; Song, Jun; Hu, Rui; Xiang, Yuren; He, Junjie; Hao, Yuying; Lian, Jiarong; Zhang, Bin; Zeng, Pengju; Qu, Junle

2018-05-01

Organic-inorganic lead halide perovskite solar cells (PVSCs), as a competing technology with traditional inorganic solar cells, have now realized a high power conversion efficiency (PCE) of 22.1%. In PVSCs, interfacial carrier recombination is one of the dominant energy-loss mechanisms, which also results in the simultaneous loss of potential efficiency. In this work, for planar inverted PVSCs, the carrier recombination is dominated by the dopant concentration in the p-doped hole transport layers (HTLs), since the F4-TCNQ dopant induces more charge traps and electronic transmission channels, thus leading to a decrease in open-circuit voltages (V OC ). This issue is efficiently overcome by inserting a thin insulating polymer layer (poly(methyl methacrylate) or polystyrene) as a passivation layer with an appropriate thickness, which allows for increases in the V OC without significantly sacrificing the fill factor. It is believed that the passivation layer attributes to the passivation of interfacial recombination and the suppression of current leakage at the perovskite/HTL interface. By manipulating this interfacial passivation technique, a high PCE of 20.3% is achieved without hysteresis. Consequently, this versatile interfacial passivation methodology is highly useful for further improving the performance of planar inverted PVSCs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural Characterization of the Foliated-Layered Gabbro Transition in Wadi Tayin of the Samail Ophiolite, Oman; Oman Drilling Project Holes GT1A and GT2A

Science.gov (United States)

Deans, J. R.; Crispini, L.; Cheadle, M. J.; Harris, M.; Kelemen, P. B.; Teagle, D. A. H.; Matter, J. M.; Takazawa, E.; Coggon, J. A.

2017-12-01

Oman Drilling Project Holes GT1A and GT2A were drilled into the Wadi Tayin massif, Samail ophiolite and both recovered ca. 400 m of continuous core through a section of the layered gabbros and the foliated-layered gabbro transition. Hole GT1A is cut by a discrete fault system including localized thin ultracataclastic fault zones. Hole GT2A is cut by a wider zone of brittle deformation and incipient brecciation. Here we report the structural history of the gabbros reflecting formation at the ridge to later obduction. Magmatic and high temperature history- 1) Both cores exhibit a pervasive, commonly well-defined magmatic foliation delineated by plagioclase, olivine and in places clinopyroxene. Minor magmatic deformation is present. 2) The dip of the magmatic foliation varies cyclically, gradually changing dip by 30o from gentle to moderate over a 50 m wavelength. 3) Layering is present throughout both cores, is defined by changes in mode and grain size ranging in thickness from 2 cm to 3 m and is commonly sub-parallel to the foliation. 4) There are no high temperature crystal-plastic shear zones in the core. Key observations include: no simple, systematic shallowing of dip with depth across the foliated-layered gabbro transition and layering is continuous across this transition. Cyclic variation of magmatic foliation dip most likely reflects the process of plate separation at the ridge axis. Near-axis faulting- i) On or near-axis structures consist of epidote-amphibole bearing hydraulic breccias and some zones of intense cataclasis with intensely deformed epidote and seams of clay and chlorite accompanied by syntectonic alteration of the wall rock. Early veins are filled with amphibole, chlorite, epidote, and anhydrite. ii) The deformation ranges from brittle-ductile, causing local deflection of the magmatic foliation, to brittle offset of the foliation and core and mantle structures in anhydrite veins. iii) The prevalent sense of shear is normal and slickenfibers

The effect of hole transporting layer in charge accumulation properties of p-i-n perovskite solar cells

Directory of Open Access Journals (Sweden)

Fedros Galatopoulos

2017-07-01

Full Text Available The charge accumulation properties of p-i-n perovskite solar cells were investigated using three representative organic and inorganic hole transporting layer (HTL: (a Poly(3,4-ethylenedioxythiophene-poly(styrenesulfonate (PEDOT:PSS, Al 4083, (b copper-doped nickel oxide (Cu:NiOx, and (c Copper oxide (CuO. Through impedance spectroscopy analysis and modelling, it is shown that charge accumulation is decreased in the HTL/perovskite interface, between PEDOT:PSS to Cu:NiOx and CuO. This was indicative from the decrease in double layer capacitance (Cdl and interfacial charge accumulation capacitance (Cel, resulting in an increase to recombination resistance (Rrec, thus decreased charge recombination events between the three HTLs. Through AFM measurements, it is also shown that the reduced recombination events (followed by the increase in Rrec are also a result of increased grain size between the three HTLs, thus reduction in the grain boundary area. These charge accumulation properties of the three HTLs have resulted in an increase to the power conversion efficiency between the PEDOT:PSS (8.44%, Cu:NiOx (11.45%, and CuO (15.3%-based devices.

Layer-selective synthesis of bilayer graphene via chemical vapor deposition

Science.gov (United States)

Yang, Ning; Choi, Kyoungjun; Robertson, John; Park, Hyung Gyu

2017-09-01

A controlled synthesis of high-quality AB-stacked bilayer graphene by chemical vapor deposition demands a detailed understanding of the mechanism and kinetics. By decoupling the growth of the two layers via a growth-and-regrowth scheme, we report the kinetics and termination mechanisms of the bilayer graphene growth on copper. We observe, for the first time, that the secondary layer growth follows Gompertzian kinetics. Our observations affirm the postulate of a time-variant transition from a mass-transport-limited to a reaction-limited regimes and identify the mechanistic disparity between the monolayer growth and the secondary-layer expansion underneath the monolayer cover. It is the continuous carbon supply that drives the expansion of the graphene secondary layer, rather than the initially captured carbon amount, suggesting an essential role of the surface diffusion of reactant adsorbates in the interspace between the top graphene layer and the underneath copper surface. We anticipate that the layer selectivity of the growth relies on the entrance energetics of the adsorbed reactants to the graphene-copper interspace across the primary-layer edge, which could be engineered by tailoring the edge termination state. The temperature-reliant saturation area of the secondary-layer expansion is understood as a result of competitive attachment of carbon and hydrogen adatoms to the secondary-layer graphene edge.

A hole accelerator for InGaN/GaN light-emitting diodes

Science.gov (United States)

Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ji, Yun; Wang, Liancheng; Zhu, Binbin; Zhang, Yiping; Lu, Shunpeng; Zhang, Xueliang; Hasanov, Namig; Sun, Xiao Wei; Demir, Hilmi Volkan

2014-10-01

The quantum efficiency of InGaN/GaN light-emitting diodes (LEDs) has been significantly limited by the insufficient hole injection, and this is caused by the inefficient p-type doping and the low hole mobility. The low hole mobility makes the holes less energetic, which hinders the hole injection into the multiple quantum wells (MQWs) especially when a p-type AlGaN electron blocking layer (EBL) is adopted. In this work, we report a hole accelerator to accelerate the holes so that the holes can obtain adequate kinetic energy, travel across the p-type EBL, and then enter the MQWs more efficiently and smoothly. In addition to the numerical study, the effectiveness of the hole accelerator is experimentally shown through achieving improved optical output power and reduced efficiency droop for the proposed InGaN/GaN LED.

Polarization-induced hole doping in N-polar III-nitride LED grown by metalorganic chemical vapor deposition

KAUST Repository

Yan, Long

2018-05-03

Polarization-induced doping has been shown to be effective for wide-bandgap III-nitrides. In this work, we demonstrated a significantly enhanced hole concentration via linearly grading an N-polar AlxGa1-xN (x = 0–0.3) layer grown by metal-organic chemical vapor deposition. The hole concentration increased by ∼17 times compared to that of N-polar p-GaN at 300 K. The fitting results of temperature-dependent hole concentration indicated that the holes in the graded p-AlGaN layer comprised both polarization-induced and thermally activated ones. By optimizing the growth conditions, the hole concentration was further increased to 9.0 × 1017 cm−3 in the graded AlGaN layer. The N-polar blue-violet light-emitting device with the graded p-AlGaN shows stronger electroluminescence than the one with the conventional p-GaN. The study indicates the potential of the polarization doping technique in high-performance N-polar light-emitting devices.

Polarization-induced hole doping in N-polar III-nitride LED grown by metalorganic chemical vapor deposition

KAUST Repository

Yan, Long; Zhang, Yuantao; Han, Xu; Deng, Gaoqiang; Li, Pengchong; Yu, Ye; Chen, Liang; Li, Xiaohang; Song, Junfeng

2018-01-01

Polarization-induced doping has been shown to be effective for wide-bandgap III-nitrides. In this work, we demonstrated a significantly enhanced hole concentration via linearly grading an N-polar AlxGa1-xN (x = 0–0.3) layer grown by metal-organic chemical vapor deposition. The hole concentration increased by ∼17 times compared to that of N-polar p-GaN at 300 K. The fitting results of temperature-dependent hole concentration indicated that the holes in the graded p-AlGaN layer comprised both polarization-induced and thermally activated ones. By optimizing the growth conditions, the hole concentration was further increased to 9.0 × 1017 cm−3 in the graded AlGaN layer. The N-polar blue-violet light-emitting device with the graded p-AlGaN shows stronger electroluminescence than the one with the conventional p-GaN. The study indicates the potential of the polarization doping technique in high-performance N-polar light-emitting devices.

PEDOT: PSS: rGO nanocomposite as a hole transport layer (HTLs) for P3HT:PCBM based organic solar cells

Science.gov (United States)

Tiwari, D. C.; Dwivedi, Shailendra Kumar; Dipak, Pukhrambam; Chandel, Tarun

2018-05-01

This paper reports the fabrication process of organic solar cell (OSCs) having structure ITO/PEDOT:PSS:rGO/P3HT:PCBM/Al. In this cell, poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT: PSS) is ultrasonically mixed with thermally reduced graphene oxide (rGO), which was used as a hole transport layer (HTLs). In order to investigate structural, morphological and optical properties of nanocomposite, XRD, FE-SEM and UV-vis spectroscopy were carried out. We have observed, Jsc = 6.5mA/cm2, Voc = 212 mV, FF=0.31 and PCE of 0.43% from fabricated organic solar cell.

"Holes" in Student Understanding: Addressing Prevalent Misconceptions regarding Atmospheric Environmental Chemistry

Science.gov (United States)

Kerr, Sara C.; Walz, Kenneth A.

2007-01-01

There is a misconception among undergraduate students that global warming is caused by holes in the ozone layer. In this study, we evaluated the presence of this and other misconceptions surrounding atmospheric chemistry that are responsible for the entanglement of the greenhouse effect and the ozone hole in students' conceptual frameworks. We…

Do superheavy elements imply the existence of black holes

International Nuclear Information System (INIS)

Pringle, J.E.; Dearborn, D.S.P.; Fabian, A.C.

1976-01-01

Some comments are offered on the question of where superheavy elements, such as elements 116, 124 and 126, are likely to have been formed. Most of these elements are thought to have been produced under conditions of explosive nucleosynthesis by what is known as the 'r-process', and particularly in conventional supernova explosions, but it is stated that the ability of the r-process to produce superheavy elements is very uncertain, and the conditions necessary for synthesis of these elements are difficult to realise in astrophysical situations. It is thought that superheavy elements exist in the outer layers of neutron stars, and ideal conditions for the production of superheavy nuclei, such as high neutron flux and rapid β decays, occur in the disruption of a neutron star. Such disruption is possible in two ways, both of which involve a black hole. It is likely that a neutron star is disrupted when it accretes sufficient material for its mass to exceed the maximum mass for stability, and it then has no alternative but to collapse to form a black hole and it seems possible that some of the outer layers are thrown off during the process. It is thus argued that the most likely site for the production of superheavy elements is in the surface layers of a neutron star, and the most plausible means by which these layers can be returned to the interstellar medium involves the intervention or formation of a black hole. (U.K.)

Multi-Layer Approach for the Detection of Selective Forwarding Attacks.

Science.gov (United States)

Alajmi, Naser; Elleithy, Khaled

2015-11-19

Security breaches are a major threat in wireless sensor networks (WSNs). WSNs are increasingly used due to their broad range of important applications in both military and civilian domains. WSNs are prone to several types of security attacks. Sensor nodes have limited capacities and are often deployed in dangerous locations; therefore, they are vulnerable to different types of attacks, including wormhole, sinkhole, and selective forwarding attacks. Security attacks are classified as data traffic and routing attacks. These security attacks could affect the most significant applications of WSNs, namely, military surveillance, traffic monitoring, and healthcare. Therefore, there are different approaches to detecting security attacks on the network layer in WSNs. Reliability, energy efficiency, and scalability are strong constraints on sensor nodes that affect the security of WSNs. Because sensor nodes have limited capabilities in most of these areas, selective forwarding attacks cannot be easily detected in networks. In this paper, we propose an approach to selective forwarding detection (SFD). The approach has three layers: MAC pool IDs, rule-based processing, and anomaly detection. It maintains the safety of data transmission between a source node and base station while detecting selective forwarding attacks. Furthermore, the approach is reliable, energy efficient, and scalable.

Multi-Layer Approach for the Detection of Selective Forwarding Attacks

Directory of Open Access Journals (Sweden)

Naser Alajmi

2015-11-01

Full Text Available Security breaches are a major threat in wireless sensor networks (WSNs. WSNs are increasingly used due to their broad range of important applications in both military and civilian domains. WSNs are prone to several types of security attacks. Sensor nodes have limited capacities and are often deployed in dangerous locations; therefore, they are vulnerable to different types of attacks, including wormhole, sinkhole, and selective forwarding attacks. Security attacks are classified as data traffic and routing attacks. These security attacks could affect the most significant applications of WSNs, namely, military surveillance, traffic monitoring, and healthcare. Therefore, there are different approaches to detecting security attacks on the network layer in WSNs. Reliability, energy efficiency, and scalability are strong constraints on sensor nodes that affect the security of WSNs. Because sensor nodes have limited capabilities in most of these areas, selective forwarding attacks cannot be easily detected in networks. In this paper, we propose an approach to selective forwarding detection (SFD. The approach has three layers: MAC pool IDs, rule-based processing, and anomaly detection. It maintains the safety of data transmission between a source node and base station while detecting selective forwarding attacks. Furthermore, the approach is reliable, energy efficient, and scalable.

Potential application of CuSbS2 as the hole transport material in perovskite solar cell: A simulation study

Science.gov (United States)

Teimouri, R.; Mohammadpour, R.

2018-06-01

CH3 NH3 PbI3 (MAPbI3) thin film solar cells, which are reported at laboratory efficiency scale of nearly 22%, are the subject of much attention by energy researchers due to their low cost buildup, acceptable efficiency, high absorption coefficient and diffusion length. The main purpose of this research is to simulate the structure of thin film perovskite solar cells through numerical simulation of SCAPS based on the empirical data for different hole transport layers. After simulating the initial structure of FTO/TiO2/CH3NH3PbI3/Spiro-OMeTAD solar cell, the hole transport layer Spiro-OMeTAD thickness was optimized on a small scale using modeling. The researchers also sought to reduce the amount of this material and the cost of construction. Ultimately, an optimum thickness of 140 nm was obtained for this cell with efficiency of 22.88%. The effect of employing alternative inorganic hole transport layer was investigated as a substitute for Spiro-OMeTAD; Copper antimony sulphide (CuSbS2) was selected due to abundant and available material and high open circuit voltage of about 988 mV. Thickness variations were also performed on a MAPbI3/CuSbS2 solar cell. Finally, It has obtained that perovskite solar cell with 120 nm-thick of CuSbS2 has 23.14% conversion efficiency with acceptable VOC and JSC values.

Magnetic layers and neutral points near a rotating black hole

Czech Academy of Sciences Publication Activity Database

Karas, Vladimír; Kopáček, Ondřej

2009-01-01

Roč. 26, č. 2 (2009), s. 1-9 ISSN 0264-9381 R&D Projects: GA ČR GA205/07/0052 Institutional research plan: CEZ:AV0Z10030501 Keywords : black holes * magnetic fields Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 3.029, year: 2009

Plasma horizons of a charged black hole

International Nuclear Information System (INIS)

Hanni, R.S.

1977-01-01

The most promising way of detecting black holes seems to be through electromagnetic radiation emitted by nearby charged particles. The nature of this radiation depends strongly on the local electromagnetic field, which varies with the charge of the black hole. It has often been purported that a black hole with significant charge will not be observed, because, the dominance of the Coulomb interaction forces its neutralization through selective accretion. This paper shows that it is possible to balance the electric attraction of particles whose charge is opposite that of the black hole with magnetic forces and (assuming an axisymmetric, stationary solution) covariantly define the regions in which this is possible. A Kerr-Newman hole in an asymptotically uniform magnetic field and a current ring centered about a Reissner-Nordstroem hole are used as examples, because of their relevance to processes through which black holes may be observed. (Auth.)

Ambipolar field-effect transistors by few-layer InSe with asymmetry contact metals

Directory of Open Access Journals (Sweden)

Chang-Yu Lin

2017-07-01

Full Text Available Group IIIA−VIA layered semiconductors (MX, where M = Ga and In, X = S, Se, and Te have attracted tremendous interest for their anisotropic optical, electronic, and mechanical properties. In this study, we demonstrated that metal and InSe junctions can lead to carrier behaviors in few-layered InSe FETs. These results indicate that the polarity of few-layered InSe FETs can be determined by using metals with different work functions. We adopted FET S/D metal contacts with asymmetric work functions to reduce the Schottky barriers of electrons and holes, and discovered that few-layered InSe FETs with carefully selected metal contacts can achieve ambipolar behaviors. These results indicate that group IIIA−VIA layered semiconductor FETs with asymmetry contact metals have great potential for applications in photovoltaic devices, optical sensors, and CMOS inverter circuits.

Electron Dynamics in a Subproton-Gyroscale Magnetic Hole

Science.gov (United States)

Gershman, Daniel J.; Dorelli, John C.; Vinas, Adolfo F.; Avanov, Levon A.; Gliese, Ulrik B.; Barrie, Alexander C.; Coffey, Victoria; Chandler, Michael; Dickson, Charles; MacDonald, Elizabeth A.;

Hole transport in c-plane InGaN-based green laser diodes

Energy Technology Data Exchange (ETDEWEB)

Cheng, Yang; Liu, Jianping, E-mail: jpliu2010@sinano.ac.cn; Tian, Aiqin; Zhang, Feng; Feng, Meixin; Hu, Weiwei; Zhang, Shuming; Ikeda, Masao; Li, Deyao; Zhang, Liqun; Yang, Hui [Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); School of Nano Technology and Nano Bionics, University of Science and Technology of China, Suzhou 215123 (China)

2016-08-29

Hole transport in c-plane InGaN-based green laser diodes (LDs) has been investigated by both simulations and experiments. It is found that holes can overflow from the green double quantum wells (DQWs) at high current density, which reduces carrier injection efficiency of c-plane InGaN-based green LDs. A heavily silicon-doped layer right below the green DQWs can effectively suppress hole overflow from the green DQWs.

Light illumination intensity dependence of photovoltaic parameter in polymer solar cells with ammonium heptamolybdate as hole extraction layer.

Science.gov (United States)

Liu, Zhiyong; Niu, Shengli; Wang, Ning

2018-01-01

A low-temperature, solution-processed molybdenum oxide (MoO X ) layer and a facile method for polymer solar cells (PSCs) is developed. The PSCs based on a MoO X layer as the hole extraction layer (HEL) is a significant advance for achieving higher photovoltaic performance, especially under weaker light illumination intensity. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements show that the (NH 4 ) 6 Mo 7 O 24 molecule decomposes and forms the molybdenum oxide (MoO X ) molecule when undergoing thermal annealing treatment. In this study, PSCs with the MoO X layer as the HEL exhibited better photovoltaic performance, especially under weak light illumination intensity (from 100 to 10mWcm -2 ) compared to poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)-based PSCs. Analysis of the current density-voltage (J-V) characteristics at various light intensities provides information on the different recombination mechanisms in the PSCs with a MoO X and PEDOT:PSS layer as the HEL. That the slopes of the open-circuit voltage (V OC ) versus light illumination intensity plots are close to 1 unity (kT/q) reveals that bimolecular recombination is the dominant and weaker monomolecular recombination mechanism in open-circuit conditions. That the slopes of the short-circuit current density (J SC ) versus light illumination intensity plots are close to 1 reveals that the effective charge carrier transport and collection mechanism of the MoO X /indium tin oxide (ITO) anode is the weaker bimolecular recombination in short-circuit conditions. Our results indicate that MoO X is an alternative candidate for high-performance PSCs, especially under weak light illumination intensity. Copyright © 2017 Elsevier Inc. All rights reserved.

Selected stratigraphic data for drill holes located in Frenchman Flat, Nevada Test Site. Rev. 1

International Nuclear Information System (INIS)

Drellack, S.L. Jr.

1997-02-01

Stratigraphic data are presented in tabular form for 72 holes drilled in Frenchman Flat, Nevada Test Site, between 1950 and 1993. Three pairs of data presentations are included for each hole: depth to formation tops, formation thicknesses, and formation elevations are presented in both field (English) and metric units. Also included for each hole, where available, are various construction data (hole depth, hole diameter, surface location coordinates) and certain information of hydrogeologic significance (depth to water level, top of zeolitization). The event name is given for holes associated with a particular nuclear test. An extensive set of footnotes is included, which indicates data sources and provides other information. The body of the report describes the stratigraphic setting of Frenchman Flat, gives drill-hole naming conventions and database terminology, and provides other background and reference material

Black holes as possible sources of closed and semiclosed worlds

International Nuclear Information System (INIS)

Frolov, V.P.; Markov, M.A.; Mukhanov, V.F.

1988-05-01

The internal structure of spacetime inside a black hole is investigated on the assumption that some limiting curvature exists. It is shown that the Schwarzschild metric inside a black hole can be attached to the de Sitter one at some spacelike junction hypersurface which represents a short transition layer. After passing the deflation stage the de Sitter space inside the black hole begins to inflate and may become a source of a new macroscopic Universe. The corresponding conformal Penrose diagrams are given. The described model may be considered as an example of ''a creation of a closed or semiclosed world in laboratory''. The fate of an evaporating black hole is also briefly discussed. (author). 21 refs, 12 figs

Plasma-assisted atomic layer deposition of TiO2 compact layers for flexible mesostructured perovskite solar cells

NARCIS (Netherlands)

Zardetto, V.; Di Giacomo, F.; Lucarelli, G.; Kessels, W.M.M.; Brown, T.M.; Creatore, M.

2017-01-01

In mesostructured perovskite solar cell devices, charge recombination processes at the interface between the transparent conductive oxide, perovskite and hole transport layer are suppressed by depositing an efficient compact TiO2 blocking layer. In this contribution we investigate the role of the

Simple solution-processed CuOX as anode buffer layer for efficient organic solar cells

International Nuclear Information System (INIS)

Shen, Wenfei; Yang, Chunpeng; Bao, Xichang; Sun, Liang; Wang, Ning; Tang, Jianguo; Chen, Weichao; Yang, Renqiang

2015-01-01

Graphical abstract: - Highlights: • Simple solution-processed CuO X hole transport layer for efficient organic solar cell. • Good photovoltaic performances as hole transport layer in OSCs with P3HT and PBDTTT-C as donor materials. • The device with CuO X as hole transport layer shows great improved stability compared with that of device with PEDOT:PSS as hole transport layer. - Abstract: A simple, solution-processed ultrathin CuO X anode buffer layer was fabricated for high performance organic solar cells (OSCs). XPS measurement demonstrated that the CuO X was the composite of CuO and Cu 2 O. The CuO X modified ITO glass exhibit a better surface contact with the active layer. The photovoltaic performance of the devices with CuO X layer was optimized by varying the thickness of CuO X films through changing solution concentration. With P3HT:PC 61 BM as the active layer, we demonstrated an enhanced PCE of 4.14% with CuO X anode buffer layer, compared with that of PEDOT:PSS layer. The CuO X layer also exhibits efficient photovoltaic performance in devices with PBDTTT-C:PC 71 BM as the active layer. The long-term stability of CuO X device is better than that of PEDOT:PSS device. The results indicate that the easy solution-processed CuO X film can act as an efficient anode buffer layer for high-efficiency OSCs

High-performance and environmentally stable planar heterojunction perovskite solar cells based on a solution-processed copper-doped nickel oxide hole-transporting layer.

Science.gov (United States)

Kim, Jong H; Liang, Po-Wei; Williams, Spencer T; Cho, Namchul; Chueh, Chu-Chen; Glaz, Micah S; Ginger, David S; Jen, Alex K-Y

2015-01-27

An effective approach to significantly increase the electrical conductivity of a NiOx hole-transporting layer (HTL) to achieve high-efficiency planar heterojunction perovskite solar cells is demonstrated. Perovskite solar cells based on using Cu-doped NiOx HTL show a remarkably improved power conversion efficiency up to 15.40% due to the improved electrical conductivity and enhanced perovskite film quality. General applicability of Cu-doped NiOx to larger bandgap perovskites is also demonstrated in this study. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Genome Scan for Selection in Structured Layer Chicken Populations Exploiting Linkage Disequilibrium Information.

Directory of Open Access Journals (Sweden)

Mahmood Gholami

Full Text Available An increasing interest is being placed in the detection of genes, or genomic regions, that have been targeted by selection because identifying signatures of selection can lead to a better understanding of genotype-phenotype relationships. A common strategy for the detection of selection signatures is to compare samples from distinct populations and to search for genomic regions with outstanding genetic differentiation. The aim of this study was to detect selective signatures in layer chicken populations using a recently proposed approach, hapFLK, which exploits linkage disequilibrium information while accounting appropriately for the hierarchical structure of populations. We performed the analysis on 70 individuals from three commercial layer breeds (White Leghorn, White Rock and Rhode Island Red, genotyped for approximately 1 million SNPs. We found a total of 41 and 107 regions with outstanding differentiation or similarity using hapFLK and its single SNP counterpart FLK respectively. Annotation of selection signature regions revealed various genes and QTL corresponding to productions traits, for which layer breeds were selected. A number of the detected genes were associated with growth and carcass traits, including IGF-1R, AGRP and STAT5B. We also annotated an interesting gene associated with the dark brown feather color mutational phenotype in chickens (SOX10. We compared FST, FLK and hapFLK and demonstrated that exploiting linkage disequilibrium information and accounting for hierarchical population structure decreased the false detection rate.

Heterojunction PbS nanocrystal solar cells with oxide charge-transport layers.

Science.gov (United States)

Hyun, Byung-Ryool; Choi, Joshua J; Seyler, Kyle L; Hanrath, Tobias; Wise, Frank W

2013-12-23

Oxides are commonly employed as electron-transport layers in optoelectronic devices based on semiconductor nanocrystals, but are relatively rare as hole-transport layers. We report studies of NiO hole-transport layers in PbS nanocrystal photovoltaic structures. Transient fluorescence experiments are used to verify the relevant energy levels for hole transfer. On the basis of these results, planar heterojunction devices with ZnO as the photoanode and NiO as the photocathode were fabricated and characterized. Solution-processed devices were used to systematically study the dependence on nanocrystal size and achieve conversion efficiency as high as 2.5%. Optical modeling indicates that optimum performance should be obtained with thinner oxide layers than can be produced reliably by solution casting. Room-temperature sputtering allows deposition of oxide layers as thin as 10 nm, which enables optimization of device performance with respect to the thickness of the charge-transport layers. The best devices achieve an open-circuit voltage of 0.72 V and efficiency of 5.3% while eliminating most organic material from the structure and being compatible with tandem structures.

Selective and low temperature transition metal intercalation in layered tellurides

Science.gov (United States)

Yajima, Takeshi; Koshiko, Masaki; Zhang, Yaoqing; Oguchi, Tamio; Yu, Wen; Kato, Daichi; Kobayashi, Yoji; Orikasa, Yuki; Yamamoto, Takafumi; Uchimoto, Yoshiharu; Green, Mark A.; Kageyama, Hiroshi

2016-01-01

Layered materials embrace rich intercalation reactions to accommodate high concentrations of foreign species within their structures, and find many applications spanning from energy storage, ion exchange to secondary batteries. Light alkali metals are generally most easily intercalated due to their light mass, high charge/volume ratio and in many cases strong reducing properties. An evolving area of materials chemistry, however, is to capture metals selectively, which is of technological and environmental significance but rather unexplored. Here we show that the layered telluride T2PTe2 (T=Ti, Zr) displays exclusive insertion of transition metals (for example, Cd, Zn) as opposed to alkali cations, with tetrahedral coordination preference to tellurium. Interestingly, the intercalation reactions proceed in solid state and at surprisingly low temperatures (for example, 80 °C for cadmium in Ti2PTe2). The current method of controlling selectivity provides opportunities in the search for new materials for various applications that used to be possible only in a liquid. PMID:27966540

White holes and eternal black holes

International Nuclear Information System (INIS)

Hsu, Stephen D H

2012-01-01

We investigate isolated white holes surrounded by vacuum, which correspond to the time reversal of eternal black holes that do not evaporate. We show that isolated white holes produce quasi-thermal Hawking radiation. The time reversal of this radiation, incident on a black hole precursor, constitutes a special preparation that will cause the black hole to become eternal. (paper)

Quasiparticle energies, excitons, and optical spectra of few-layer black phosphorus

International Nuclear Information System (INIS)

Tran, Vy; Fei, Ruixiang; Yang, Li

2015-01-01

We report first-principles GW–Bethe–Salpeter-equation (BSE) studies of excited-state properties of few-layer black phosphorus (BP) (phosphorene). With improved GW computational methods, we obtained converged quasiparticle band gaps and optical absorption spectra by the single-shot (G 0 W 0 ) procedure. Moreover, we reveal fine structures of anisotropic excitons, including the series of one-dimensional like wave functions, spin singlet–triplet splitting, and electron–hole binding energy spectra by solving BSE. An effective-mass model is employed to describe these electron–hole pairs, shedding light on estimating the exciton binding energy of anisotropic two-dimensional semiconductors without expensive ab initio simulations. Finally, the anisotropic optical response of BP is explained by using optical selection rules based on the projected single-particle density of states at band edges. (paper)

Topotactic growth, selective adsorption, and adsorption-driven photocatalysis of protonated layered titanate nanosheets.

Science.gov (United States)

Wu, Qili; Yang, Xianfeng; Liu, Jia; Nie, Xin; Huang, Yongliang; Wen, Yuping; Khan, Javid; Khan, Wasim U; Wu, Mingmei; An, Taicheng

2014-10-22

Layered titanates with selective adsorption ability and adsorption-driven photocatalytic property can be quite attractive due to their potential applications in water purification. In this work, lepidocrocite-like layered protonated titanate (H2Ti2O5·H2O, denoted as HTO) nanosheets were successfully synthesized by an ion-exchange process. It turns out that this layered structure displays an abundant and selective adsorption toward the fluoroquinolone pharmaceutical compared with some large dye molecules due to a size selectivity of the interlayer spacing of HTO and the molecular horizontal size, as well as their electrostatic interaction. The uptake ability of HTO could be readily controlled through adjusting the pH values of adsorbate solution, and the maximum uptake capacity was achieved at the pH value of about 5.5 for ciprofloxacin (CIP) and 6.5 for moxifloxacin (MOX). The adsorption amount of smaller nalidixic acid (NAL) showed an increasing tendency as the pH value decreased. Moreover, the two-dimensional layered crystal structure also permits such HTO nanosheets to have a large percentage of (010) faces exposed, which is considerably provided by the interlayer surfaces of these nanosheets. The (010) surface has a similar Ti and O atomic arrangement as to the highly reactive anatase TiO2(001) one. Due to these specific characteristics, these HTO nanosheets show excellent photocatalytic activity in degrading CIP under UV light irradiation as well as possess a superior adsorption ability to remove CIP from aqueous solution selectively and efficiently. The photocatalytic reaction is believed to be mainly conducted on the active anatase (001)-like interlayer (010) surfaces of the layered structures since the as-prepared HTO performs an adsorption-driven molecular recognitive photocatalytic reaction.

Trap effect of an ultrathin DCJTB layer in organic light-emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Wang Yuanmin [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Teng Feng [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China)]. E-mail: advanced9898@126.com; Xu Zheng [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Hou Yanbing [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Yang Shengyi [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China); Xu Xurong [Institute of Optoelectronic Technology, Key Laboratory for Information Storage, Displays and Materials, Beijing Jiaotong University, Beijing 100044 (China)

2005-08-15

An improved performance of organic light-emitting diodes has been obtained by using 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) -4Hpyran (DCJTB) as an ultrathin emitting layer. When 0.1 nm DCJTB was inserted between the hole-transporting layer and electron-transporting layer, for an unoptimized device indium-tin oxide (ITO)/naphtylphenyliphenyl diamine (NPB)/DCJTB (0.1 nm)/8-hydroxyquinoline aluminum (Alq{sub 3})/Al, the maximum brightness was 1531 cd m{sup -2} at 15 V. Compared with doped devices ITO/NPB/Alq{sub 3}:DCJTB (1%)/Alq{sub 3}/LiF/Al, a higher efficiency has been achieved. Compared with the conventional device ITO/NPB/Alq{sub 3}/Al, the inserted device has a slightly higher current efficiency and lower turn-on voltage. We suggest the ultrathin DCJTB layer acts as trap for carriers, and the accumulated holes at the hole-transport layer/electron-transport layer interface have enhanced the electric field in the electron-transport layer and improved the electron injection at the cathode.

Understanding Molecular Interactions within Chemically Selective Layered Polymer Assemblies

Energy Technology Data Exchange (ETDEWEB)

Gary J. Blanchard

2009-06-30

This work focuses on two broad issues. These are (1) the molecular origin of the chemical selectivity achieved with ultrathin polymer multilayers, and (2) how the viscoelastic properties of the polymer layers are affected by exposure to solvent and analytes. These issues are inter-related, and to understand them we need to design experiments that probe both the energetic and kinetic aspects of interfacial adsorption processes. This project focuses on controling the chemical structure, thickness, morphology and sequential ordering of polymer layers bound to interfaces using maleimide-vinyl ether and closely related alternating copolymerization chemistry and efficient covalent cross-linking reactions that allow for layer-by-layer polymer deposition. This chemistry has been developed during the funding cycle of this Grant. We have measure the equilibrium constants for interactions between specific layers within the polymer interfaces and size-controlled, surface-functionalized gold nanoparticles. The ability to control both size and functionality of gold nanoparticle model analytes allows us to evaluate the average “pore size” that characterizes our polymer films. We have measured the “bulk” viscosity and shear modulus of the ultrathin polymer films as a function of solvent overlayer identity using quartz crystal microbalance complex impedance measurements. We have measured microscopic viscosity at specific locations within the layered polymer interfaces with time-resolved fluorescence lifetime and depolarization techniques. We combine polymer, cross-linking and nanoparticle synthetic expertise with a host of characterization techniques, including QCM gravimetry and complex impedance analysis, steady state and time-resolved spectroscopies.

On the AlxGa1-xN/AlyGa1-yN/AlxGa1-xN (x>y) p-electron blocking layer to improve the hole injection for AlGaN based deep ultraviolet light-emitting diodes

Science.gov (United States)

Chu, Chunshuang; Tian, Kangkai; Fang, Mengqian; Zhang, Yonghui; Li, Luping; Bi, Wengang; Zhang, Zi-Hui

2018-01-01

This work proposes the [0001] oriented AlGaN-based deep ultraviolet (DUV) light-emitting diode (LED) possessing a specifically designed p-electron blocking layer (p-EBL) to achieve the high internal quantum efficiency. Both electrons and holes can be efficiently injected into the active region by adopting the Al0.60Ga0.40N/Al0.50Ga0.50N/Al0.60Ga0.40N structured p-EBL, in which a p-Al0.50Ga0.50N layer is embedded into the p-EBL. Moreover, the impact of different thicknesses for the p-Al0.50Ga0.50N insertion layer on the hole and electron injections has also been investigated. Compared with the DUV LED with the bulk p-Al0.60Ga0.40N as the EBL, the proposed LED architectures improve the light output power if the thickness of the p-Al0.50Ga0.50N insertion layer is properly designed.

Stationary black holes as holographs

Energy Technology Data Exchange (ETDEWEB)

Racz, Istvan [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-01 (Japan); MTA KFKI, Reszecske- es Magfizikai Kutatointezet, H-1121 Budapest, Konkoly Thege Miklos ut 29-33 (Hungary)

2007-11-21

Smooth spacetimes possessing a (global) one-parameter group of isometries and an associated Killing horizon in Einstein's theory of gravity are investigated. No assumption concerning the asymptotic structure is made; thereby, the selected spacetimes may be considered as generic distorted stationary black holes. First, spacetimes of arbitrary dimension, n {>=} 3, with matter satisfying the dominant energy condition and allowing a non-zero cosmological constant are investigated. In this part, complete characterization of the topology of the event horizon of 'distorted' black holes is given. It is shown that the topology of the event horizon of 'distorted' black holes is allowed to possess a much larger variety than that of the isolated black hole configurations. In the second part, four-dimensional (non-degenerate) electrovac distorted black hole spacetimes are considered. It is shown that the spacetime geometry and the electromagnetic field are uniquely determined in the black hole region once the geometry of the bifurcation surface and one of the electromagnetic potentials are specified there. Conditions guaranteeing the same type of determinacy, in a neighbourhood of the event horizon, on the domain of outer communication side are also investigated. In particular, they are shown to be satisfied in the analytic case.

Associate host in single-layer co-host polymer electrophosphorescent devices

International Nuclear Information System (INIS)

Wang Yuanmin; Teng Feng; Feng Bin; Wang Yongsheng; Xu Xurong

2006-01-01

The definition and role of 'host' in polymer LED materials are studied in the present work. 'Primary host' and 'associate host' have been proposed and the rules of how to select an associate host are reported. Based on our experiments and the analysis of the energy scheme of the devices, we suggest that the values of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) are critical determinant in selecting a suitable associate host. On one hand, the associate host should be a hole-blocking material. This can confine the excitons in the active layer. On the other hand, the associate host should have a suitable LUMO that is convenient for electrons to transport

Observation of Blobs and Holes in the Boundary Plasma of EAST Tokamak

DEFF Research Database (Denmark)

Yan, Ning; Xu, Guosheng; Zhang, Wei

2011-01-01

Intermittent convective transport at the edge and in the scrape-off layer (SOL) of EAST was investigated by using fast reciprocating Langmuir probe. Holes, as part of plasma structures, were detected for the first time inside the shear layer. The amplitude probability distribution function...

Recombination zone in white organic light emitting diodes with blue and orange emitting layers

Science.gov (United States)

Tsuboi, Taiju; Kishimoto, Tadashi; Wako, Kazuhiro; Matsuda, Kuniharu; Iguchi, Hirofumi

2012-10-01

White fluorescent OLED devices with a 10 nm thick blue-emitting layer and a 31 nm thick orange-emitting layer have been fabricated, where the blue-emitting layer is stacked on a hole transport layer. An interlayer was inserted between the two emitting layers. The thickness of the interlayer was changed among 0.3, 0.4, and 1.0 nm. White emission with CIE coordinates close to (0.33, 0.33) was observed from all the OLEDs. OLED with 0.3 nm thick interlayer gives the highest maximum luminous efficiency (11 cd/A), power efficiency (9 lm/W), and external quantum efficiency (5.02%). The external quantum efficiency becomes low with increasing the interlayer thickness from 0 nm to 1.0 nm. When the location of the blue- and orange-emitting layers is reversed, white emission was not obtained because of too weak blue emission. It is suggested that the electron-hole recombination zone decreases nearly exponentially with a distance from the hole transport layer.

Is Black Hole Growth a Universal Process? Exploring Selection Effects in Measurements of AGN Accretion Rates and Host Galaxies.

Science.gov (United States)

Jones, Mackenzie

2018-01-01

At the center of essentially every massive galaxy is a monstrous black hole producing luminous radiation driven by the accretion of gas. By observing these active galactic nuclei (AGN) we may trace the growth of black holes across cosmic time. However, our knowledge of the full underlying AGN population is hindered by complex observational biases. My research aims to untangle these biases by using a novel approach to simulate the impact of selection effects on multiwavelength observations.The most statistically powerful studies of AGN to date come from optical spectroscopic surveys, with some reporting a complex relationship between AGN accretion rates and host galaxy characteristics. However, the optical waveband can be strongly influenced by selection effects and dilution from host galaxy star formation. I have shown that accounting for selection effects, the Eddington ratio distribution for optically-selected AGN is consistent with a broad power-law, as seen in the X-rays (Jones et al. 2016). This suggests that a universal Eddington ratio distribution may be enough to describe the full multiwavelength AGN population.Building on these results, I have expanded a semi-numerical galaxy formation simulation to include this straightforward prescription for AGN accretion and explicitly model selection effects. I have found that a simple model for AGN accretion can broadly reproduce the host galaxies and halos of X-ray AGN, and that different AGN selection techniques yield samples with very different host galaxy properties (Jones et al. 2017). Finally, I will discuss the capabilities of this simulation to build synthetic multiwavelength SEDs in order to explore what AGN populations would be detected with the next generation of observatories. This research is supported by a NASA Jenkins Graduate Fellowship under grant no. NNX15AU32H.

Phase-space holes due to electron and ion beams accelerated by a current-driven potential ramp

Directory of Open Access Journals (Sweden)

M. V. Goldman

2003-01-01

Full Text Available One-dimensional open-boundary simulations have been carried out in a current-carrying plasma seeded with a neutral density depression and with no initial electric field. These simulations show the development of a variety of nonlinear localized electric field structures: double layers (unipolar localized fields, fast electron phase-space holes (bipolar fields moving in the direction of electrons accelerated by the double layer and trains of slow alternating electron and ion phase-space holes (wave-like fields moving in the direction of ions accelerated by the double layer. The principal new result in this paper is to show by means of a linear stability analysis that the slow-moving trains of electron and ion holes are likely to be the result of saturation via trapping of a kinetic-Buneman instability driven by the interaction of accelerated ions with unaccelerated electrons.

Vascular Displacement in Idiopathic Macular Hole after Single-layered Inverted Internal Limiting Membrane Flap Surgery.

Science.gov (United States)

Lee, Jae Jung; Lee, In Ho; Park, Keun Heung; Pak, Kang Yeun; Park, Sung Who; Byon, Ik Soo; Lee, Ji Eun

2017-08-01

To compare vascular displacement in the macula after surgical closure of idiopathic macular hole (MH) after single-layered inverted internal limiting membrane (ILM) flap technique and conventional ILM removal. This retrospective study included patients who underwent either vitrectomy and ILM removal only or vitrectomy with single-layered inverted ILM flap for idiopathic MH larger than 400 μm from 2012 to 2015. A customized program compared the positions of the retinal vessels in the macula between preoperative and postoperative photographs. En face images of 6 × 6 mm optical coherence tomography volume scans were registered to calculate the scale. Retinal vessel displacement was measured as a vector value by comparing its location in 16 sectors of a grid partitioned into eight sectors in two rings (inner, 2 to 4 mm; outer, 4 to 6 mm). The distance and angle of displacement were calculated as an average vector and were compared between the two groups for whole sectors, inner ring, outer ring, and for each sector. Twenty patients were included in the ILM flap group and 22 in the ILM removal group. There were no statistical differences between the groups for baseline characteristics. The average displacement in the ILM flap group and the ILM removal group was 56.6 μm at -3.4° and 64.9 μm at -2.7°, respectively, for the whole sectors (p = 0.900), 76.1 μm at -1.1° and 87.3 μm at -0.9° for the inner ring (p = 0.980), and 37.4 μm at -8.2° and 42.7 μm at -6.3° for the outer ring (p = 0.314). There was no statistical difference in the displacement of each of the sectors. Postoperative topographic changes showed no significant differences between the ILM flap and the ILM removal group for idiopathic MH. The single-layered ILM flap technique did not appear to cause additional displacement of the retinal vessels in the macula. © 2017 The Korean Ophthalmological Society

Binary black holes on a budget: simulations using workstations

International Nuclear Information System (INIS)

Marronetti, Pedro; Tichy, Wolfgang; Bruegmann, Bernd; Gonzalez, Jose; Hannam, Mark; Husa, Sascha; Sperhake, Ulrich

2007-01-01

Binary black hole simulations have traditionally been computationally very expensive: current simulations are performed in supercomputers involving dozens if not hundreds of processors, thus systematic studies of the parameter space of binary black hole encounters still seem prohibitive with current technology. Here we show how the multi-layered refinement level code BAM can be used on dual processor workstations to simulate certain binary black hole systems. BAM, based on the moving punctures method, provides grid structures composed of boxes of increasing resolution near the centre of the grid. In the case of binaries, the highest resolution boxes are placed around each black hole and they track them in their orbits until the final merger when a single set of levels surrounds the black hole remnant. This is particularly useful when simulating spinning black holes since the gravitational fields gradients are larger. We present simulations of binaries with equal mass black holes with spins parallel to the binary axis and intrinsic magnitude of S/m 2 = 0.75. Our results compare favourably to those of previous simulations of this particular system. We show that the moving punctures method produces stable simulations at maximum spatial resolutions up to M/160 and for durations of up to the equivalent of 20 orbital periods

Heterojunction PbS Nanocrystal Solar Cells with Oxide Charge-Transport Layers

KAUST Repository

Hyun, Byung-Ryool

2013-12-23

Oxides are commonly employed as electron-transport layers in optoelectronic devices based on semiconductor nanocrystals, but are relatively rare as hole-transport layers. We report studies of NiO hole-transport layers in PbS nanocrystal photovoltaic structures. Transient fluorescence experiments are used to verify the relevant energy levels for hole transfer. On the basis of these results, planar heterojunction devices with ZnO as the photoanode and NiO as the photocathode were fabricated and characterized. Solution-processed devices were used to systematically study the dependence on nanocrystal size and achieve conversion efficiency as high as 2.5%. Optical modeling indicates that optimum performance should be obtained with thinner oxide layers than can be produced reliably by solution casting. Roomerature sputtering allows deposition of oxide layers as thin as 10 nm, which enables optimization of device performance with respect to the thickness of the charge-transport layers. The best devices achieve an open-circuit voltage of 0.72 V and efficiency of 5.3% while eliminating most organic material from the structure and being compatible with tandem structures. © 2013 American Chemical Society.

Multiple extrafoveal macular holes following internal limiting membrane peeling

Directory of Open Access Journals (Sweden)

Hussain N

2018-05-01

Full Text Available Nazimul Hussain, Sandip Mitra Department of Ophthalmology, Al Zahra Hospital, Sharjah, United Arab Emirates Objective: Internal limiting membrane (ILM peeling has been the standard of treatment for macular holes. Besides, causing retinal nerve fiber layer surface abnormality, postoperative extrafoveal multiple retinal holes is a rare phenomenon following ILM peeling. We report an unusual complication of eight extrafoveal macular holes occurring following ILM peeling.Case presentation: A 60-year-old male presented with complaints of decreased and distorted vision in the right eye. He was diagnosed as having epiretinal membrane with lamellar macular hole. He underwent 23G pars plana vitrectomy, brilliant blue assisted ILM peeling and fluid gas exchange. Intraoperatively, ILM was found to be adherent to the underlying neurosensory retina. One month after cataract surgery, he underwent YAG capsulotomy in the right eye. He complained of visual distortion. His fundus evaluation in the right eye showed multiple (eight extrafoveal retinal holes temporal to the macula clustered together.Conclusion: This case demonstrated that peeling of ILM, especially when it is adherent to the underlying neurosensory retina, may cause unwanted mechanical trauma to the inner retina. Glial apoptosis and neuronal degeneration may presumably play a role in delayed appearance of multiple (eight extrafoveal macular holes, which has not been reported earlier. Keywords: internal limiting membrane, lamellar macular hole, full thickness macular holes, epiretinal membrane

Multiple extrafoveal macular holes following internal limiting membrane peeling.

Science.gov (United States)

Hussain, Nazimul; Mitra, Sandip

2018-01-01

Internal limiting membrane (ILM) peeling has been the standard of treatment for macular holes. Besides, causing retinal nerve fiber layer surface abnormality, postoperative extrafoveal multiple retinal holes is a rare phenomenon following ILM peeling. We report an unusual complication of eight extrafoveal macular holes occurring following ILM peeling. A 60-year-old male presented with complaints of decreased and distorted vision in the right eye. He was diagnosed as having epiretinal membrane with lamellar macular hole. He underwent 23G pars plana vitrectomy, brilliant blue assisted ILM peeling and fluid gas exchange. Intraoperatively, ILM was found to be adherent to the underlying neurosensory retina. One month after cataract surgery, he underwent YAG capsulotomy in the right eye. He complained of visual distortion. His fundus evaluation in the right eye showed multiple (eight) extrafoveal retinal holes temporal to the macula clustered together. This case demonstrated that peeling of ILM, especially when it is adherent to the underlying neurosensory retina, may cause unwanted mechanical trauma to the inner retina. Glial apoptosis and neuronal degeneration may presumably play a role in delayed appearance of multiple (eight) extrafoveal macular holes, which has not been reported earlier.

Effects of pentacene-doped PEDOT:PSS as a hole-conducting layer on the performance characteristics of polymer photovoltaic cells.

Science.gov (United States)

Kim, Hyunsoo; Lee, Jungrae; Ok, Sunseong; Choe, Youngson

2012-01-05

We have investigated the effect of pentacene-doped poly(3,4-ethylenedioxythiophene:poly(4-styrenesulfonate) [PEDOT:PSS] films as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the amount of pentacene and the annealing temperature of pentacene-doped PEDOT:PSS layer, the changes of performance characteristics were evaluated. Pentacene-doped PEDOT:PSS thin films were prepared by dissolving pentacene in 1-methyl-2-pyrrolidinone solvent and mixing with PEDOT:PSS. As the amount of pentacene in the PEDOT:PSS solution was increased, UV-visible transmittance also increased dramatically. By increasing the amount of pentacene in PEDOT:PSS films, dramatic decreases in both the work function and surface resistance were observed. However, the work function and surface resistance began to sharply increase above the doping amount of pentacene at 7.7 and 9.9 mg, respectively. As the annealing temperature was increased, the surface roughness of pentacene-doped PEDOT:PSS films also increased, leading to the formation of PEDOT:PSS aggregates. The films of pentacene-doped PEDOT:PSS were characterized by AFM, SEM, UV-visible transmittance, surface analyzer, surface resistance, and photovoltaic response analysis.

Wetting layers effect on InAs/GaAs quantum dots

International Nuclear Information System (INIS)

Sun Chao; Lu Pengfei; Yu Zhongyuan; Cao Huawei; Zhang Lidong

2012-01-01

FEM combining with the K·P theory is adopted to systematically investigate the effect of wetting layers on the strain-stress profiles and electronic structures of self-organized InAs quantum dot. Four different kinds of quantum dots are introduced at the same height and aspect ratio. We found that 0.5 nm wetting layer is an appropriate thickness for InAs/GaAs quantum dots. Strain shift down about 3%∼4.5% for the cases with WL (0.5 nm) and without WL in four shapes of quantum dots. For band edge energy, wetting layers expand the potential energy gap width. When WL thickness is more than 0.8 nm, the band edge energy profiles cannot vary regularly. The electron energy is affected while for heavy hole this impact on the energy is limited. Wetting layers for the influence of the electronic structure is obviously than the heavy hole. Consequently, the electron probability density function spread from buffer to wetting layer while the center of hole's function moves from QDs internal to wetting layer when introduce WLs. When WLs thickness is larger than 0.8 nm, the electronic structures of quantum dots have changed obviously. This will affect the instrument's performance which relies on the quantum dots' optical properties.

Improving the efficiency and environmental stability of inverted planar perovskite solar cells via silver-doped nickel oxide hole-transporting layer

Science.gov (United States)

Wei, Ying; Yao, Kai; Wang, Xiaofeng; Jiang, Yihua; Liu, Xueyuan; Zhou, Naigen; Li, Fan

2018-01-01

In this paper, we demonstrate the high-performance inverted planar heterojunction perovskite solar cells (PeSCs) based on the novel inorganic hole-transporting layer (HTL) of silver (Ag)-doped NiOx (Ag:NiOx). Density-functional theory (DFT) calculation reveals that Ag prefers to occupy the substitutional Ni site (AgNi) and behaves as an acceptor in NiO lattice. Compared with the pristine NiOx films, appropriate Ag doping can increase the optical transparency, work function, electrical conductivity and hole mobility of NiOx films. Moreover, the CH3NH3PbI3 perovskite films grown on Ag:NiOx exhibit better crystallinity, higher coverage and smoother surface with densely packed larger grains than those grown on the pristine NiOx film. Consequently, the Ag:NiOx HTL boosts the efficiency of the inverted planar heterojunction PeSCs from 13.46% (for the pristine NiOx-based device) to 16.86% (for the 2 at.% Ag:NiOx-based device). Furthermore, the environmental stability of PeSCs based on Ag:NiOx HTL is dramatically improved compared to devices based on organic HTLs and pristine NiOx HTLs. This work provides a simple and effective HTL material system for high-efficient and stable PeSCs.

Solution-processed inorganic copper(I) thiocyanate (CuSCN) hole transporting layers for efficient p–i–n perovskite solar cells

KAUST Repository

Zhao, Kui

2015-08-27

CuSCN is a highly transparent, highly stable, low cost and easy to solution process HTL that is proposed as a low cost replacement to existing organic and inorganic metal oxide hole transporting materials. Here, we demonstrate hybrid organic-inorganic perovskite-based p-i-n planar heterojunction solar cells using a solution-processed copper(I) thiocyanate (CuSCN) bottom hole transporting layer (HTL). CuSCN, with its high workfunction, increases the open circuit voltage (Voc) by 0.23 V to 1.06 V as compared with devices based on the well-known poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (0.83 V), resulting in a superior power conversion efficiency (PCE) of 10.8% without any notable hysteresis. Photoluminescence measurements suggest a similar efficiency of charge transfer at HTL/perovskite interface as PEDOT:PSS. However, we observe more efficient light harvesting in the presence of CuSCN at shorter wavelengths despite PEDOT:PSS being more transparent. Further investigation of the microstructure and morphology reveals differences in the crystallographic texture of the polycrystalline perovskite film, suggesting somewhat modified perovskite growth on the surface of CuSCN. The successful demonstration of the solution-processed inorganic HTL using simple and low temperature processing routes bodes well for the development of reliable and efficient flexible p-i-n perovskite modules or for integration as a front cell in hybrid tandem solar cells.

Phosphorene: an unexplored 2D semiconductor with a high hole mobility.

Science.gov (United States)

Liu, Han; Neal, Adam T; Zhu, Zhen; Luo, Zhe; Xu, Xianfan; Tománek, David; Ye, Peide D

2014-04-22

We introduce the 2D counterpart of layered black phosphorus, which we call phosphorene, as an unexplored p-type semiconducting material. Same as graphene and MoS2, single-layer phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct, and appreciable band gap. Our ab initio calculations indicate that the band gap is direct, depends on the number of layers and the in-layer strain, and is significantly larger than the bulk value of 0.31-0.36 eV. The observed photoluminescence peak of single-layer phosphorene in the visible optical range confirms that the band gap is larger than that of the bulk system. Our transport studies indicate a hole mobility that reflects the structural anisotropy of phosphorene and complements n-type MoS2. At room temperature, our few-layer phosphorene field-effect transistors with 1.0 μm channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm(2)/V·s, and an on/off ratio of up to 10(4). We demonstrate the possibility of phosphorene integration by constructing a 2D CMOS inverter consisting of phosphorene PMOS and MoS2 NMOS transistors.

Area-selective atomic layer deposition of platinum using photosensitive polyimide.

Science.gov (United States)

Vervuurt, René H J; Sharma, Akhil; Jiao, Yuqing; Kessels, Wilhelmus Erwin M M; Bol, Ageeth A

2016-10-07

Area-selective atomic layer deposition (AS-ALD) of platinum (Pt) was studied using photosensitive polyimide as a masking layer. The polyimide films were prepared by spin-coating and patterned using photolithography. AS-ALD of Pt using poly(methyl-methacrylate) (PMMA) masking layers was used as a reference. The results show that polyimide has excellent selectivity towards the Pt deposition, after 1000 ALD cycles less than a monolayer of Pt is deposited on the polyimide surface. The polyimide film could easily be removed after ALD using a hydrogen plasma, due to a combination of weakening of the polyimide resist during Pt ALD and the catalytic activity of Pt traces on the polyimide surface. Compared to PMMA for AS-ALD of Pt, polyimide has better temperature stability. This resulted in an improved uniformity of the Pt deposits and superior definition of the Pt patterns. In addition, due to the absence of reflow contamination using polyimide the nucleation phase during Pt ALD is drastically shortened. Pt patterns down to 3.5 μm were created with polyimide, a factor of ten smaller than what is possible using PMMA, at the typical Pt ALD processing temperature of 300 °C. Initial experiments indicate that after further optimization of the polyimide process Pt features down to 100 nm should be possible, which makes AS-ALD of Pt using photosensitive polyimide a promising candidate for patterning at the nanoscale.

Recombination barrier layers in solid-state quantum dot-sensitized solar cells

KAUST Repository

Roelofs, Katherine E.; Brennan, Thomas P.; Dominguez, Juan C.; Bent, Stacey F.

2012-01-01

in situ by successive ion layer adsorption and reaction (SILAR). Aluminum oxide recombination barrier layers were deposited by atomic layer deposition (ALD) at the TiO2/hole-conductor interface. For low numbers of ALD cycles, the Al2O3 barrier layer

The Phase Transition of Higher Dimensional Charged Black Holes

International Nuclear Information System (INIS)

Li, Huaifan; Zhao, Ren; Zhang, Lichun; Guo, Xiongying

2016-01-01

We have studied phase transitions of higher dimensional charge black hole with spherical symmetry. We calculated the local energy and local temperature and find that these state parameters satisfy the first law of thermodynamics. We analyze the critical behavior of black hole thermodynamic system by taking state parameters (Q,Φ) of black hole thermodynamic system, in accordance with considering the state parameters (P,V) of van der Waals system, respectively. We obtain the critical point of black hole thermodynamic system and find that the critical point is independent of the dual independent variables we selected. This result for asymptotically flat space is consistent with that for AdS spacetime and is intrinsic property of black hole thermodynamic system.

Selective Excitation of Window and Buffer Layers in Chalcopyrite Devices and Modules

Energy Technology Data Exchange (ETDEWEB)

Glynn, Stephen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Repins, Ingrid L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Burst, James M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Beall, Carolyn L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bowers, Karen A [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Mansfield, Lorelle M [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2018-02-02

Window and buffer layers in chalcopyrite devices are well known to affect junctions, conduction, and photo-absorption properties of the device. Some of these layers, particularly 'buffers,' which are deposited directly on top of the absorber, exhibit metastable effects upon exposure to light. Thus, to understand device performance and/or metastability, it is sometimes desirable to selectively excite different layers in the device stack. Absorption characteristics of various window and buffer layers used in chalcopyrite devices are measured. These characteristics are compared with emission spectra of common and available light sources that might be used to optically excite such layers. Effects of the window and buffer absorption on device quantum efficiency and metastability are discussed. For the case of bath-deposited Zn(O,S) buffers, we conclude that this layer is not optically excited in research devices or modules. This provides a complimentary mechanism to the chemical differences that may cause long time constants (compared to devices with CdS buffers) associated with reaching a stable 'light-soaked' state.

Foundations of Black Hole Accretion Disk Theory

Directory of Open Access Journals (Sweden)

Marek A. Abramowicz

2013-01-01

Full Text Available This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves. In this light we discuss how accretion disks might reveal some of the unique signatures of strong gravity: the event horizon, the innermost stable circular orbit, and the ergosphere. We then review, from a first-principles perspective, the physical processes at play in accretion disks. This leads us to the four primary accretion disk models that we review: Polish doughnuts (thick disks, Shakura-Sunyaev (thin disks, slim disks, and advection-dominated accretion flows (ADAFs. After presenting the models we discuss issues of stability, oscillations, and jets. Following our review of the analytic work, we take a parallel approach in reviewing numerical studies of black hole accretion disks. We finish with a few select applications that highlight particular astrophysical applications: measurements of black hole mass and spin, black hole vs. neutron star accretion disks, black hole accretion disk spectral states, and quasi-periodic oscillations (QPOs.

Foundations of Black Hole Accretion Disk Theory.

Science.gov (United States)

Abramowicz, Marek A; Fragile, P Chris

2013-01-01

This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves. In this light we discuss how accretion disks might reveal some of the unique signatures of strong gravity: the event horizon, the innermost stable circular orbit, and the ergosphere. We then review, from a first-principles perspective, the physical processes at play in accretion disks. This leads us to the four primary accretion disk models that we review: Polish doughnuts (thick disks), Shakura-Sunyaev (thin) disks, slim disks, and advection-dominated accretion flows (ADAFs). After presenting the models we discuss issues of stability, oscillations, and jets. Following our review of the analytic work, we take a parallel approach in reviewing numerical studies of black hole accretion disks. We finish with a few select applications that highlight particular astrophysical applications: measurements of black hole mass and spin, black hole vs. neutron star accretion disks, black hole accretion disk spectral states, and quasi-periodic oscillations (QPOs).

Monte Carlo modeling of time-resolved fluorescence for depth-selective interrogation of layered tissue.

Science.gov (United States)

Pfefer, T Joshua; Wang, Quanzeng; Drezek, Rebekah A

2011-11-01

Computational approaches for simulation of light-tissue interactions have provided extensive insight into biophotonic procedures for diagnosis and therapy. However, few studies have addressed simulation of time-resolved fluorescence (TRF) in tissue and none have combined Monte Carlo simulations with standard TRF processing algorithms to elucidate approaches for cancer detection in layered biological tissue. In this study, we investigate how illumination-collection parameters (e.g., collection angle and source-detector separation) influence the ability to measure fluorophore lifetime and tissue layer thickness. Decay curves are simulated with a Monte Carlo TRF light propagation model. Multi-exponential iterative deconvolution is used to determine lifetimes and fractional signal contributions. The ability to detect changes in mucosal thickness is optimized by probes that selectively interrogate regions superficial to the mucosal-submucosal boundary. Optimal accuracy in simultaneous determination of lifetimes in both layers is achieved when each layer contributes 40-60% of the signal. These results indicate that depth-selective approaches to TRF have the potential to enhance disease detection in layered biological tissue and that modeling can play an important role in probe design optimization. Published by Elsevier Ireland Ltd.

Bulk heterojunction perovskite solar cells based on room temperature deposited hole-blocking layer: Suppressed hysteresis and flexible photovoltaic application

Science.gov (United States)

Chen, Zhiliang; Yang, Guang; Zheng, Xiaolu; Lei, Hongwei; Chen, Cong; Ma, Junjie; Wang, Hao; Fang, Guojia

2017-05-01

Perovskite solar cells have developed rapidly in recent years as the third generation solar cells. In spite of the great improvement achieved, there still exist some issues such as undesired hysteresis and indispensable high temperature process. In this work, bulk heterojunction perovskite-phenyl-C61-butyric acid methyl ester solar cells have been prepared to diminish hysteresis using a facile two step spin-coating method. Furthermore, high quality tin oxide films are fabricated using pulse laser deposition technique at room temperature without any annealing procedure. The as fabricated tin oxide film is successfully applied in bulk heterojunction perovskite solar cells as a hole blocking layer. Bulk heterojunction devices based on room temperature tin oxide exhibit almost hysteresis-free characteristics with power conversion efficiency of 17.29% and 14.0% on rigid and flexible substrates, respectively.

Investigation of Poly(3,4-ethylenedioxythiophene:Poly(styrenesulfonate Hole Transport Layer for Solution-Processed Polymer Solar Cells

Directory of Open Access Journals (Sweden)

Chengxi Zhang

2015-01-01

Full Text Available The inverted polymer solar cell was prepared by self-made spray-coating system, and the poly(3,4-ethylenedioxythiophene:poly(styrenesulfonate (PEDOT:PSS hole transport layer was studied. 220 nm poly-(3-hexylthiophene:[6,6]-phenylC61butyric-acid methyl-ester (P3HT:PCBM and 40 nm PEDOT:PSS were deposited on ZnO thin film subsequently by solution spray coating. Different volume of isopropyl alcohol was introduced into PEDOT:PSS to decrease the contact angle and obtain the optimum Marangoni flow. The surface morphology and roughness of PEDOT:PSS films were characterized by atomic force microscopy with varied deposition temperature from 70°C to 160°C. The improvement of power conversion efficiency (PCE was attributed to the enhancement of vertical phase separation in PEDOT:PSS film, which improved the charge transfer in the bulk cell. The highest PCE of spray-coated PSCs reached 2.80% after postannealing for 10 min.

Investigation of Selective Laser Melting Surface Alloyed Aluminium Metal Matrix Dispersive Reinforced Layers

Science.gov (United States)

Kamburov, V. V.; Dimitrova, R. B.; Kandeva, M. K.; Sofronov, Y. P.

2018-01-01

The aim of the paper is to investigate the improvement of mechanical properties and in particular wear resistance of laser surface alloyed dispersive reinforced thin layers produced by selective laser melting (SLM) technology. The wear resistance investigation of aluminium matrix composite layers in the conditions of dry friction surface with abrasive particles and nanoindentation tests were carried out. The process parameters (as scan speed) and their impact on the wear resistant layers have been evaluated. The alloyed layers containing metalized SiC particles were studied by Optical and Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray microanalysis (EDX). The obtained experimental results of the laser alloyed thin layers show significant development of their wear resistance and nanohardness due to the incorporated reinforced phase of electroless nickel coated SiC particles.

Research of precise pulse plasma arc powder welding technology of thin-walled inner hole parts

Institute of Scientific and Technical Information of China (English)

Li Zhanming; Du Xiaokun; Sun Xiaofeng; Song Wei

2017-01-01

The inner hole parts played an oriented or supporting role in engineering machinery and equipment,which are prone to appear surface damages such as wear,strain and corrosion.The precise pulse plasma arc powder welding method is used for surface damage repairing of inner hole parts in this paper.The working principle and process of the technology are illustrated,and the microstructure and property of repairing layer by precise pulse plasma powder welding and CO2 gas shielded welding are tested and observed by microscope,micro hardness tester and X-ray residual stress tester etc.Results showed that the substrate deformation of thin-walled inner hole parts samples by precise pulse plasma powder welding is relatively small.The repair layer and substrate is metallurgical bonding,the transition zones (including fusion zone and heat affected zone) are relatively narrow and the welding quality is good.h showed that the thin-walled inner hole parts can be repaired by this technology and equipment.

High-permeance crosslinked PTMSP thin-film composite membranes as supports for CO2 selective layer formation

Directory of Open Access Journals (Sweden)

Stepan D. Bazhenov

2016-10-01

Full Text Available In the development of the composite gas separation membranes for post-combustion CO2 capture, little attention is focused on the optimization of the membrane supports, which satisfy the conditions of this technology. The primary requirements to the membrane supports are concerned with their high CO2 permeance. In this work, the membrane supports with desired characteristics were developed as high-permeance gas separation thin film composite (TFC membranes with the thin defect-free layer from the crosslinked highly permeable polymer, poly[1-(trimethylsilyl-1-propyne] (PTMSP. This layer is insoluble in chloroform and can be used as a gutter layer for the further deposition of the СО2-selective materials from the organic solvents. Crosslinking of PTMSP was performed using polyethyleneimine (PEI and poly (ethyleneglycol diglycidyl ether (PEGDGE as crosslinking agents. Optimal concentrations of PEI in PTMSP and PEGDGE in methanol were selected in order to diminish the undesirable effect on the final membrane gas transport characteristics. The conditions of the kiss-coating technique for the deposition of the thin defect-free PTMSP-based layer, namely, composition of the casting solution and the speed of movement of the porous commercial microfiltration-grade support, were optimized. The procedure of post-treatment with alcohols and alcohol solutions was shown to be crucial for the improvement of gas permeance of the membranes with the crosslinked PTMSP layer having thickness ranging within 1–2.5 μm. The claimed membranes showed the following characteristics: CO2 permeance is equal to 50–54 m3(STP/(m2 h bar (18,500–20,000 GPU, ideal CO2/N2 selectivity is 3.6–3.7, and their selective layers are insoluble in chloroform. Thus, the developed high-permeance TFC membranes are considered as a promising supports for further modification by enhanced CO2 selective layer formation. Keywords: Thin-film composite membrane

Filter construction technology in mining drilling hole for in-situ leaching of multilayer deposit

International Nuclear Information System (INIS)

Jiang Yan; Hu Baishi; Tan Yahui; Yang Lizhi; Li Xiaojian; Wang Xiaodong; Chang Jingtao; Qin Hao

2014-01-01

Taking a typical multilayer sandstone uranium deposit as example, study was carried out on filter construction technology in mining drilling hole for in-situ leaching of multilayer deposit. According to the character of multilayer sandstone, four injecting holes and one drawning hole were designed between the P13-P15 exploration lines, five different methods were used to construct filter. Construction technology by different methods was introduced and the advantages and disadvantages of the construction filter with five methods were analysed. As far as five experimental drilling holes, layered gravel-filling hole construction technology is a suitable method for construction multilayer filter with continuous construction, simple operation and good effect of well completion. (authors)

Measuring the $W$-hair of String Black Holes

CERN Document Server

Ellis, Jonathan Richard; Nanopoulos, Dimitri V; Ellis, John

1992-01-01

We have argued previously that the infinitely many gauge symmetries of string theory provide an infinite set of conserved (gauge) quantum numbers ($W$-hair) which characterise black hole states and maintain quantum coherence. Here we study ways of measuring the $W$-hair of spherically-symmetric four-dimensional objects with event horizons, treated as effectively two-dimensional string black holes. Measurements can be done either through the s-wave scattering of light particles off the string black-hole background, or through interference experiments of Aharonov-Bohm type. In the first type of measurement, selection rules

Bounded excursion stable gravastars and black holes

Energy Technology Data Exchange (ETDEWEB)

Rocha, P [Instituto de Fisica, Universidade Federal Fluminense, Avenida Litoranea, s/n, Boa Viagem 24210-340, Niteroi, RJ (Brazil); Miguelote, A Y; Chan, R [Coordenacao de Astronomia e Astrofisica, Observatorio Nacional, Rua General Jose Cristino, 77, Sao Cristovao 20921-400, Rio de Janeiro, RJ (Brazil); Da Silva, M F; Wang, Anzhong [Departamento de Fisica Teorica, Instituto de Fisica, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier 524, Maracana 20550-900, Rio de Janeiro-RJ (Brazil); Santos, N O, E-mail: pedrosennarocha@gmail.com, E-mail: yasuda@on.br, E-mail: chan@on.br, E-mail: mfasnic@gmail.com, E-mail: N.O.Santos@qmul.ac.uk, E-mail: anzhong_wang@baylor.edu [LERMA/CNRS-FRE 2460, Universite Pierre et Marie Curie, ERGA, Boite 142, 4 Place Jussieu, 75005 Paris Cedex 05 (France)

2008-06-15

Dynamical models of prototype gravastars were constructed in order to study their stability. The models are the Visser-Wiltshire three-layer gravastars, in which an infinitely thin spherical shell of stiff fluid divides the whole spacetime into two regions, where the internal region is de Sitter, and the external one is Schwarzschild. It is found that in some cases the models represent the 'bounded excursion' stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes occurs. In the phase space, the region for the 'bounded excursion' gravastars is very small in comparison to that of black holes, but not empty. Therefore, although the possibility of the existence of gravastars cannot be excluded from such dynamical models, our results indicate that, even if gravastars do indeed exist, that does not exclude the possibility of the existence of black holes.

Simple solution-processed CuO{sub X} as anode buffer layer for efficient organic solar cells

Energy Technology Data Exchange (ETDEWEB)

Shen, Wenfei [CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Institute of Hybrid Materials, The Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Yang, Chunpeng [CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Bao, Xichang, E-mail: baoxc@qibebt.ac.cn [CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Sun, Liang; Wang, Ning [CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Tang, Jianguo [Institute of Hybrid Materials, The Growing Base for State Key Laboratory, Qingdao University, 308 Ningxia Road, Qingdao 266071 (China); Chen, Weichao [CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China); Yang, Renqiang, E-mail: yangrq@qibebt.ac.cn [CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 189 Songling Road, Qingdao 266101 (China)

2015-10-15

Graphical abstract: - Highlights: • Simple solution-processed CuO{sub X} hole transport layer for efficient organic solar cell. • Good photovoltaic performances as hole transport layer in OSCs with P3HT and PBDTTT-C as donor materials. • The device with CuO{sub X} as hole transport layer shows great improved stability compared with that of device with PEDOT:PSS as hole transport layer. - Abstract: A simple, solution-processed ultrathin CuO{sub X} anode buffer layer was fabricated for high performance organic solar cells (OSCs). XPS measurement demonstrated that the CuO{sub X} was the composite of CuO and Cu{sub 2}O. The CuO{sub X} modified ITO glass exhibit a better surface contact with the active layer. The photovoltaic performance of the devices with CuO{sub X} layer was optimized by varying the thickness of CuO{sub X} films through changing solution concentration. With P3HT:PC{sub 61}BM as the active layer, we demonstrated an enhanced PCE of 4.14% with CuO{sub X} anode buffer layer, compared with that of PEDOT:PSS layer. The CuO{sub X} layer also exhibits efficient photovoltaic performance in devices with PBDTTT-C:PC{sub 71}BM as the active layer. The long-term stability of CuO{sub X} device is better than that of PEDOT:PSS device. The results indicate that the easy solution-processed CuO{sub X} film can act as an efficient anode buffer layer for high-efficiency OSCs.

19.2% Efficient InP Heterojunction Solar Cell with Electron-Selective TiO2 Contact.

Science.gov (United States)

Yin, Xingtian; Battaglia, Corsin; Lin, Yongjing; Chen, Kevin; Hettick, Mark; Zheng, Maxwell; Chen, Cheng-Ying; Kiriya, Daisuke; Javey, Ali

2014-12-17

We demonstrate an InP heterojunction solar cell employing an ultrathin layer (∼10 nm) of amorphous TiO 2 deposited at 120 °C by atomic layer deposition as the transparent electron-selective contact. The TiO 2 film selectively extracts minority electrons from the conduction band of p-type InP while blocking the majority holes due to the large valence band offset, enabling a high maximum open-circuit voltage of 785 mV. A hydrogen plasma treatment of the InP surface drastically improves the long-wavelength response of the device, resulting in a high short-circuit current density of 30.5 mA/cm 2 and a high power conversion efficiency of 19.2%.

Creation of nanosized holes in graphene planes for improvement of rate capability of lithium-ion batteries

Science.gov (United States)

Bulusheva, L. G.; Stolyarova, S. G.; Chuvilin, A. L.; Shubin, Yu V.; Asanov, I. P.; Sorokin, A. M.; Mel'gunov, M. S.; Zhang, Su; Dong, Yue; Chen, Xiaohong; Song, Huaihe; Okotrub, A. V.

2018-04-01

Holes with an average size of 2-5 nm have been created in graphene layers by heating of graphite oxide (GO) in concentrated sulfuric acid followed by annealing in an argon flow. The hot mineral acid acts simultaneously as a defunctionalizing and etching agent, removing a part of oxygen-containing groups and lattice carbon atoms from the layers. Annealing of the holey reduced GO at 800 °C-1000 °C causes a decrease of the content of residual oxygen and the interlayer spacing thus producing thin compact stacks from holey graphene layers. Electrochemical tests of the obtained materials in half-cells showed that the removal of oxygen and creation of basal holes lowers the capacity loss in the first cycle and facilitates intercalation-deintercalation of lithium ions. This was attributed to minimization of electrolyte decomposition reactions, easier desolvation of lithium ions near the hole boundaries and appearance of multiple entrances for the naked ions into graphene stacks.

Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

International Nuclear Information System (INIS)

Padilla, J. L.; Alper, C.; Ionescu, A. M.; Medina-Bailón, C.; Gámiz, F.

2015-01-01

We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I ON levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures

Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

Energy Technology Data Exchange (ETDEWEB)

Padilla, J. L., E-mail: jose.padilladelatorre@epfl.ch; Alper, C.; Ionescu, A. M. [Nanoelectronic Devices Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015 (Switzerland); Medina-Bailón, C.; Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain)

2015-06-29

We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I{sub ON} levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures.

Wetting layers effect on InAs/GaAs quantum dots

Energy Technology Data Exchange (ETDEWEB)

Sun Chao [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, P.O. Box 49(BUPT), Xitucheng Road No. 10, Beijing 100876 (China); Lu Pengfei, E-mail: photon.bupt@gmail.com [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, P.O. Box 49(BUPT), Xitucheng Road No. 10, Beijing 100876 (China); Yu Zhongyuan; Cao Huawei; Zhang Lidong [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, P.O. Box 49(BUPT), Xitucheng Road No. 10, Beijing 100876 (China)

2012-11-15

FEM combining with the K{center_dot}P theory is adopted to systematically investigate the effect of wetting layers on the strain-stress profiles and electronic structures of self-organized InAs quantum dot. Four different kinds of quantum dots are introduced at the same height and aspect ratio. We found that 0.5 nm wetting layer is an appropriate thickness for InAs/GaAs quantum dots. Strain shift down about 3%{approx}4.5% for the cases with WL (0.5 nm) and without WL in four shapes of quantum dots. For band edge energy, wetting layers expand the potential energy gap width. When WL thickness is more than 0.8 nm, the band edge energy profiles cannot vary regularly. The electron energy is affected while for heavy hole this impact on the energy is limited. Wetting layers for the influence of the electronic structure is obviously than the heavy hole. Consequently, the electron probability density function spread from buffer to wetting layer while the center of hole's function moves from QDs internal to wetting layer when introduce WLs. When WLs thickness is larger than 0.8 nm, the electronic structures of quantum dots have changed obviously. This will affect the instrument's performance which relies on the quantum dots' optical properties.

Optimal management of idiopathic macular holes.

Science.gov (United States)

Madi, Haifa A; Masri, Ibrahim; Steel, David H

2016-01-01

This review evaluates the current surgical options for the management of idiopathic macular holes (IMHs), including vitrectomy, ocriplasmin (OCP), and expansile gas use, and discusses key background information to inform the choice of treatment. An evidence-based approach to selecting the best treatment option for the individual patient based on IMH characteristics and patient-specific factors is suggested. For holes without vitreomacular attachment (VMA), vitrectomy is the only option with three key surgical variables: whether to peel the inner limiting membrane (ILM), the type of tamponade agent to be used, and the requirement for postoperative face-down posturing. There is a general consensus that ILM peeling improves primary anatomical hole closure rate; however, in small holes (holes, but large (>400 µm) and chronic holes (>1-year history) are usually treated with long-acting gas and posturing. Several studies on posturing and gas choice were carried out in combination with ILM peeling, which may also influence the gas and posturing requirement. Combined phacovitrectomy appears to offer more rapid visual recovery without affecting the long-term outcomes of vitrectomy for IMH. OCP is licensed for use in patients with small- or medium-sized holes and VMA. A greater success rate in using OCP has been reported in smaller holes, but further predictive factors for its success are needed to refine its use. It is important to counsel patients realistically regarding the rates of success with intravitreal OCP and its potential complications. Expansile gas can be considered as a further option in small holes with VMA; however, larger studies are required to provide guidance on its use.

Selective UV–O3 treatment for indium zinc oxide thin film transistors with solution-based multiple active layer

Science.gov (United States)

Kim, Yu-Jung; Jeong, Jun-Kyo; Park, Jung-Hyun; Jeong, Byung-Jun; Lee, Hi-Deok; Lee, Ga-Won

2018-06-01

In this study, a method to control the electrical performance of solution-based indium zinc oxide (IZO) thin film transistors (TFTs) is proposed by ultraviolet–ozone (UV–O3) treatment on the selective layer during multiple IZO active layer depositions. The IZO film is composed of triple layers formed by spin coating and UV–O3 treatment only on the first layer or last layer. The IZO films are compared by X-ray photoelectron spectroscopy, and the results show that the atomic ratio of oxygen vacancy (VO) increases in the UV–O3 treatment on the first layer, while it decreases on last layer. The device characteristics of the bottom gated structure are also improved in the UV–O3 treatment on the first layer. This indicates that the selective UV–O3 treatment in a multi-stacking active layer is an effective method to optimize TFT properties by controlling the amount of VO in the IZO interface and surface independently.

Microstructure, Morphology, and Nanomechanical Properties Near Fine Holes Produced by Electro-Discharge Machining

Science.gov (United States)

Blau, P. J.; Howe, J. Y.; Coffey, D. W.; Trejo, R. M.; Kenik, E. D.; Jolly, B. C.; Yang, N.

2012-08-01

Fine holes in metal alloys are employed for many important technological purposes, including cooling and the precise atomization of liquids. For example, they play an important role in the metering and delivery of fuel to the combustion chambers in energy-efficient, low-emission diesel engines. Electro-discharge machining (EDM) is one process employed to produce such holes. Since the hole shape and bore morphology can affect fluid flow, and holes also represent structural discontinuities in the tips of the spray nozzles, it is important to understand the microstructures adjacent to these holes, the features of the hole walls, and the nanomechanical properties of the material that was in some manner altered by the EDM hole-making process. Several techniques were used to characterize the structure and properties of spray-holes in a commercial injector nozzle. These include scanning electron microscopy, cross sectioning and metallographic etching, bore surface roughness measurements by optical interferometry, scanning electron microscopy, and transmission electron microscopy of recast EDM layers extracted with the help of a focused ion beam.

Cuprous Oxide as a Potential Low-Cost Hole-Transport Material for Stable Perovskite Solar Cells.

Science.gov (United States)

Nejand, Bahram Abdollahi; Ahmadi, Vahid; Gharibzadeh, Saba; Shahverdi, Hamid Reza

2016-02-08

Inorganic hole-transport materials are commercially desired to decrease the fabrication cost of perovskite solar cells. Here, Cu2O is introduced as a potential hole-transport material for stable, low-cost devices. Considering that Cu2O formation is highly sensitive to the underlying mixture of perovskite precursors and their solvents, we proposed and engineered a technique for reactive magnetron sputtering. The rotational angular deposition of Cu2O yields high surface coverage of the perovskite layer for high rate of charge extraction. Deposition of this Cu2O layer on the pinhole-free perovskite layer produces devices with power conversion efficiency values of up to 8.93%. The engineered Cu2O layers showed uniform, compact, and crack-free surfaces on the perovskite layer without affecting the perovskite structure, which is desired for deposition of the top metal contact and for surface shielding against moisture and mechanical damages. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Binary black hole coalescence in the large-mass-ratio limit: The hyperboloidal layer method and waveforms at null infinity

International Nuclear Information System (INIS)

Bernuzzi, Sebastiano; Nagar, Alessandro; Zenginoglu, Anil

2011-01-01

We compute and analyze the gravitational waveform emitted to future null infinity by a system of two black holes in the large-mass-ratio limit. We consider the transition from the quasiadiabatic inspiral to plunge, merger, and ringdown. The relative dynamics is driven by a leading order in the mass ratio, 5PN-resummed, effective-one-body (EOB), analytic-radiation reaction. To compute the waveforms, we solve the Regge-Wheeler-Zerilli equations in the time-domain on a spacelike foliation, which coincides with the standard Schwarzschild foliation in the region including the motion of the small black hole, and is globally hyperboloidal, allowing us to include future null infinity in the computational domain by compactification. This method is called the hyperboloidal layer method, and is discussed here for the first time in a study of the gravitational radiation emitted by black hole binaries. We consider binaries characterized by five mass ratios, ν=10 -2,-3,-4,-5,-6 , that are primary targets of space-based or third-generation gravitational wave detectors. We show significative phase differences between finite-radius and null-infinity waveforms. We test, in our context, the reliability of the extrapolation procedure routinely applied to numerical relativity waveforms. We present an updated calculation of the final and maximum gravitational recoil imparted to the merger remnant by the gravitational wave emission, v kick end /(cν 2 )=0.04474±0.00007 and v kick max /(cν 2 )=0.05248±0.00008. As a self-consistency test of the method, we show an excellent fractional agreement (even during the plunge) between the 5PN EOB-resummed mechanical angular momentum loss and the gravitational wave angular momentum flux computed at null infinity. New results concerning the radiation emitted from unstable circular orbits are also presented. The high accuracy waveforms computed here could be considered for the construction of template banks or for calibrating analytic models such

Efficiency of solution-processed multilayer polymer light-emitting diodes using charge blocking layers

Science.gov (United States)

Kasparek, Christian; Rörich, Irina; Blom, Paul W. M.; Wetzelaer, Gert-Jan A. H.

2018-01-01

By blending semiconducting polymers with the cross-linkable matrix ethoxylated-(4)-bisphenol-a-dimethacrylate (SR540), an insoluble layer is acquired after UV-illumination. Following this approach, a trilayer polymer light-emitting diode (PLED) consisting of a blend of poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD) and SR540 as an electron-blocking layer, Super Yellow-Poly(p-phenylene vinylene) (SY-PPV) blended with SR540 as an emissive layer, and poly(9,9-di-n-octylfluorenyl-2,7-diyl) as a hole-blocking layer is fabricated from solution. The trilayer PLED shows a 23% increase in efficiency at low voltage as compared to a single layer SY-PPV PLED. However, at higher voltage, the advantage in current efficiency gradually decreases. A combined experimental and modelling study shows that the increased efficiency is not only due to the elimination of exciton quenching at the electrodes but also due to suppressed nonradiative trap-assisted recombination due to carrier confinement. At high voltages, holes can overcome the hole-blocking barrier, which explains the efficiency roll-off.

Carrier mobility and scattering lifetime in electric double-layer gated few-layer graphene

Energy Technology Data Exchange (ETDEWEB)

Piatti, E.; Galasso, S.; Tortello, M.; Nair, J.R.; Gerbaldi, C. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy); Bruna, M.; Borini, S. [Istituto Nazionale di Ricerca Metrologica (INRIM), 10135 Torino (Italy); Daghero, D. [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy); Gonnelli, R.S., E-mail: renato.gonnelli@polito.it [Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 10129 Torino (Italy)

2017-02-15

Highlights: • We fabricated few-layer graphene FETs by mechanical exfoliation and standard microfabrication techniques. • We employed a Li-TFSI based ion gel to induce carrier densities as high as ≈6e14 e{sup −}/cm{sup 2} in the devices' channel. • We found a strong asymmetry in the sheet conductance and mobility doping dependences between electron and hole doping. • We combined the experimental results with ab initio DFT calculations to obtain the average scattering lifetime of the charge carriers. • We found that the increase in the carrier density and an unexpected increase in the density of charged scattering centers compete in determining the scattering lifetime. - Abstract: We fabricate electric double-layer field-effect transistor (EDL-FET) devices on mechanically exfoliated few-layer graphene. We exploit the large capacitance of a polymeric electrolyte to study the transport properties of three, four and five-layer samples under a large induced surface charge density both above and below the glass transition temperature of the polymer. We find that the carrier mobility shows a strong asymmetry between the hole and electron doping regime. We then employ ab initio density functional theory (DFT) calculations to determine the average scattering lifetime from the experimental data. We explain its peculiar dependence on the carrier density in terms of the specific properties of the electrolyte we used in our experiments.

Quantum Black Hole Model and HAWKING’S Radiation

Science.gov (United States)

Berezin, Victor

The black hole model with a self-gravitating charged spherical symmetric dust thin shell as a source is considered. The Schroedinger-type equation for such a model is derived. This equation appeared to be a finite differences equation. A theory of such an equation is developed and general solution is found and investigated in details. The discrete spectrum of the bound state energy levels is obtained. All the eigenvalues appeared to be infinitely degenerate. The ground state wave functions are evaluated explicitly. The quantum black hole states are selected and investigated. It is shown that the obtained black hole mass spectrum is compatible with the existence of Hawking’s radiation in the limit of low temperatures both for large and nearly extreme Reissner-Nordstrom black holes. The above mentioned infinite degeneracy of the mass (energy) eigenvalues may appeared helpful in resolving the well known information paradox in the black hole physics.

Engineering of electronic properties of single layer graphene by swift heavy ion irradiation

Science.gov (United States)

Kumar, Sunil; Kumar, Ashish; Tripathi, Ambuj; Tyagi, Chetna; Avasthi, D. K.

2018-04-01

In this work, swift heavy ion irradiation induced effects on the electrical properties of single layer graphene are reported. The modulation in minimum conductivity point in graphene with in-situ electrical measurement during ion irradiation was studied. It is found that the resistance of graphene layer decreases at lower fluences up to 3 × 1011 ions/cm2, which is accompanied by the five-fold increase in electron and hole mobilities. The ion irradiation induced increase in electron and hole mobilities at lower fluence up to 1 × 1011 ions/cm2 is verified by separate Hall measurements on another irradiated graphene sample at the selected fluence. In contrast to the adverse effects of irradiation on the electrical properties of materials, we have found improvement in electrical mobility after irradiation. The increment in mobility is explained by considering the defect annealing in graphene after irradiation at a lower fluence regime. The modification in carrier density after irradiation is also observed. Based on findings of the present work, we suggest ion beam irradiation as a useful tool for tuning of the electrical properties of graphene.

Black holes

International Nuclear Information System (INIS)

Feast, M.W.

1981-01-01

This article deals with two questions, namely whether it is possible for black holes to exist, and if the answer is yes, whether we have found any yet. In deciding whether black holes can exist or not the central role in the shaping of our universe played by the forse of gravity is discussed, and in deciding whether we are likely to find black holes in the universe the author looks at the way stars evolve, as well as white dwarfs and neutron stars. He also discusses the problem how to detect a black hole, possible black holes, a southern black hole, massive black holes, as well as why black holes are studied

Gene selection using hybrid binary black hole algorithm and modified binary particle swarm optimization.

Science.gov (United States)

Pashaei, Elnaz; Pashaei, Elham; Aydin, Nizamettin

2018-04-14

In cancer classification, gene selection is an important data preprocessing technique, but it is a difficult task due to the large search space. Accordingly, the objective of this study is to develop a hybrid meta-heuristic Binary Black Hole Algorithm (BBHA) and Binary Particle Swarm Optimization (BPSO) (4-2) model that emphasizes gene selection. In this model, the BBHA is embedded in the BPSO (4-2) algorithm to make the BPSO (4-2) more effective and to facilitate the exploration and exploitation of the BPSO (4-2) algorithm to further improve the performance. This model has been associated with Random Forest Recursive Feature Elimination (RF-RFE) pre-filtering technique. The classifiers which are evaluated in the proposed framework are Sparse Partial Least Squares Discriminant Analysis (SPLSDA); k-nearest neighbor and Naive Bayes. The performance of the proposed method was evaluated on two benchmark and three clinical microarrays. The experimental results and statistical analysis confirm the better performance of the BPSO (4-2)-BBHA compared with the BBHA, the BPSO (4-2) and several state-of-the-art methods in terms of avoiding local minima, convergence rate, accuracy and number of selected genes. The results also show that the BPSO (4-2)-BBHA model can successfully identify known biologically and statistically significant genes from the clinical datasets. Copyright © 2018 Elsevier Inc. All rights reserved.

Selective exfoliation of single-layer graphene from non-uniform graphene grown on Cu

International Nuclear Information System (INIS)

Lim, Jae-Young; Lee, Jae-Hyun; Jang, Hyeon-Sik; Whang, Dongmok; Joo, Won-Jae; Hwang, SungWoo

2015-01-01

Graphene growth on a copper surface via metal-catalyzed chemical vapor deposition has several advantages in terms of providing high-quality graphene with the potential for scale-up, but the product is usually inhomogeneous due to the inability to control the graphene layer growth. The non-uniform regions strongly affect the reliability of the graphene in practical electronic applications. Herein, we report a novel graphene transfer method that allows for the selective exfoliation of single-layer graphene from non-uniform graphene grown on a Cu foil. Differences in the interlayer bonding energy are exploited to mechanically separate only the top single-layer graphene and transfer this to an arbitrary substrate. The dry-transferred single-layer graphene showed electrical characteristics that were more uniform than those of graphene transferred using conventional wet-etching transfer steps. (paper)

Improvement of the optical quality of site-controlled InAs quantum dots by a double stack growth technique in wet-chemically etched holes

Energy Technology Data Exchange (ETDEWEB)

Pfau, Tino Johannes; Gushterov, Aleksander; Reithmaier, Johann-Peter [Technische Physik, INA, Universitaet Kassel (Germany); Cestier, Isabelle; Eisenstein, Gadi [Electrical Engineering Dept., Technion, Haifa (Israel); Linder, Evgany; Gershoni, David [Solid State Institute and Physics Dept., Technion, Haifa (Israel)

2010-07-01

The optimization of the wet-chemically etching of holes and a special MBE growth stack technique allows enlarging the site-control of low density InAs QDs on GaAs substrates up to a buffer layer thickness of 55 nm. The strain of InAs QDs, grown in the etched holes, reduces the hole closing, so that a pre-patterned surface is conserved for the second QD layer. The distance of 50 nm GaAs between the two QD layers exceeds drastically the maximum vertical alignment based on pure strain coupling (20 nm). Compared to stacks with several QD layers, this method avoids electronic coupling between the different QD layers and reduces the problems to distinguish the dots of different layers optically. Confocal microphotoluminescence reveals a significant diminution of the low temperature photoluminescence linewidth of the second InAs QD layer to an average value of 505{+-}53 {mu}eV and a minimum width of 460 {mu}eV compared to 2 to 4 meV for QDs grown on thin buffer layers. The increase of the buffer layer thickness decreases the influence of the surface defects caused by prepatterning.

Planar perovskite solar cells employing copper(I) thiocyanate/N,N‧-di(1-naphthyl)-N,N‧-diphenyl-(1,1‧-biphenyl)-4,4‧-diamine bilayer structure as hole transport layers

Science.gov (United States)

Tseng, Zong-Liang; Chen, Lung-Chien

2018-02-01

Organic hole transport materials, such as N 2,N 2,N 2‧,N 2‧,N 7,N 7,N 7‧,N 7‧-octakis(4-methoxyphenyl)-9,9‧-spirobi[9H-fluorene]-2,2‧,7,7‧-tetramine (Spiro-OMeTAD), are commonly used as the hole transport materials in efficient perovskite solar cells, but the chemical synthetic procedure may increase the cost of the photovoltaic devices. On the other hand, inorganic hole transport materials, such as copper(I) thiocyanate (CuSCN) or copper(I) iodide (CuI), have potential for the manufacture of efficient and low-cost perovskite solar cells, but the performance of these devices is still imperfect. In this study, we demonstrate the use of an inorganic CuSCN and organic N,N‧-di(1-naphthyl)-N,N‧-diphenyl-(1,1‧-biphenyl)-4,4‧-diamine (NPB) hybrid bilayer as an alternative hole transport layer for planar CH3NH3PbI3 perovskite solar cells. The electronic behavior of the bilayer and the performance of the corresponding devices were discussed. As a result, the power conversion efficiency (PCE) for the best cells at AM1.5G illumination with a shadow mask was 12.3%.

Gamma-ray spectrometry applied to down-hole logging

International Nuclear Information System (INIS)

Dumesnil, P.; Umiastowsky, K.

1983-11-01

Gamma-ray spectrometry permits to improve the accuracy of natural gamma, gamma-gamma and neutron-gamma geophysical measurements. The probe developed at Centre d'Etudes Nucleaires de Saclay allows down-hole gamma-ray spectrometry. Among others, this probe can be applied to the uranium content determination by selective natural gamma method, down-hole determination of the ash content in the coal by gamma-gamma selective method and elemental analysis by neutron-gamma method. For the calibration and an exact interpretation of the measurements it is important to know the gamma-ray and neutron characteristics of the different kinds of rocks considered as probabilistic variables

Modelling investigations of DBRs and cavities with photonic crystal holes for application in VCSELs

International Nuclear Information System (INIS)

Ivanov, P; Ho, Y-L D; Cryan, M J; Rorison, J

2012-01-01

We investigate the reflection spectra of distributed Bragg reflectors (DBRs) and DBR cavities with and without photonic crystal holes fabricated within them. A finite-difference time domain (FDTD) electromagnetic model which is considered to provide the exact solution of Maxwell equations is used as a reference model. Two simplified modelling approaches are compared to the FDTD results: an effective index model where the individual DBR constituent layers penetrated by holes possess an effective index and a spatial loss model where optical losses are introduced spatially where the holes are fabricated. Results of the FDTD and the spatial loss model show that optical loss determines the properties of an etched DBR and DBR cavity when the lattice constant of the holes of exceeds 1 μm and the hole depth is small. The spatial loss model compares well to the FDTD results for holes with a lattice period exceeding 1 μm. We also consider the realistic effect of angling the sides of the etched holes. (paper)

σ-holes and π-holes: Similarities and differences.

Science.gov (United States)

Politzer, Peter; Murray, Jane S

2018-04-05

σ-Holes and π-holes are regions of molecules with electronic densities lower than their surroundings. There are often positive electrostatic potentials associated with them. Through these potentials, the molecule can interact attractively with negative sites, such as lone pairs, π electrons, and anions. Such noncovalent interactions, "σ-hole bonding" and "π-hole bonding," are increasingly recognized as being important in a number of different areas. In this article, we discuss and compare the natures and characteristics of σ-holes and π-holes, and factors that influence the strengths and locations of the resulting electrostatic potentials. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Nano-electron beam induced current and hole charge dynamics through uncapped Ge nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Marchand, A.; El Hdiy, A.; Troyon, M. [Laboratoire de Recherche en Nanosciences, Bat. 6, case no 15, UFR Sciences, Universite de Reims Champagne Ardenne, 51687 Reims Cedex 2 (France); Amiard, G.; Ronda, A.; Berbezier, I. [IM2NP, Faculte des Sciences et Techniques, Campus de Saint Jerome - Case 142, Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20 (France)

2012-04-16

Dynamics of hole storage in spherical Ge nanocrystals (NCs) formed by a two step dewetting/nucleation process on an oxide layer grown on an n-doped <001> silicon substrate is studied using a nano-electron beam induced current technique. Carrier generation is produced by an electron beam irradiation. The generated current is collected by an atomic force microscope--tip in contact mode at a fixed position away from the beam spot of about 0.5 {mu}m. This distance represents the effective diffusion length of holes. The time constants of holes charging are determined and the effect of the NC size is underlined.

Defence against Black Hole and Selective Forwarding Attacks for Medical WSNs in the IoT

Directory of Open Access Journals (Sweden)

Avijit Mathur

2016-01-01

Full Text Available Wireless sensor networks (WSNs are being used to facilitate monitoring of patients in hospital and home environments. These systems consist of a variety of different components/sensors and many processes like clustering, routing, security, and self-organization. Routing is necessary for medical-based WSNs because it allows remote data delivery and it facilitates network scalability in large hospitals. However, routing entails several problems, mainly due to the open nature of wireless networks, and these need to be addressed. This paper looks at two of the problems that arise due to wireless routing between the nodes and access points of a medical WSN (for IoT use: black hole and selective forwarding (SF attacks. A solution to the former can readily be provided through the use of cryptographic hashes, while the latter makes use of a neighbourhood watch and threshold-based analysis to detect and correct SF attacks. The scheme proposed here is capable of detecting a selective forwarding attack with over 96% accuracy and successfully identifying the malicious node with 83% accuracy.

Defence against Black Hole and Selective Forwarding Attacks for Medical WSNs in the IoT.

Science.gov (United States)

Mathur, Avijit; Newe, Thomas; Rao, Muzaffar

2016-01-19

Wireless sensor networks (WSNs) are being used to facilitate monitoring of patients in hospital and home environments. These systems consist of a variety of different components/sensors and many processes like clustering, routing, security, and self-organization. Routing is necessary for medical-based WSNs because it allows remote data delivery and it facilitates network scalability in large hospitals. However, routing entails several problems, mainly due to the open nature of wireless networks, and these need to be addressed. This paper looks at two of the problems that arise due to wireless routing between the nodes and access points of a medical WSN (for IoT use): black hole and selective forwarding (SF) attacks. A solution to the former can readily be provided through the use of cryptographic hashes, while the latter makes use of a neighbourhood watch and threshold-based analysis to detect and correct SF attacks. The scheme proposed here is capable of detecting a selective forwarding attack with over 96% accuracy and successfully identifying the malicious node with 83% accuracy.

Statistical-mechanical entropy by the thin-layer method

International Nuclear Information System (INIS)

Feng, He; Kim, Sung Won

2003-01-01

G. Hooft first studied the statistical-mechanical entropy of a scalar field in a Schwarzschild black hole background by the brick-wall method and hinted that the statistical-mechanical entropy is the statistical origin of the Bekenstein-Hawking entropy of the black hole. However, according to our viewpoint, the statistical-mechanical entropy is only a quantum correction to the Bekenstein-Hawking entropy of the black-hole. The brick-wall method based on thermal equilibrium at a large scale cannot be applied to the cases out of equilibrium such as a nonstationary black hole. The statistical-mechanical entropy of a scalar field in a nonstationary black hole background is calculated by the thin-layer method. The condition of local equilibrium near the horizon of the black hole is used as a working postulate and is maintained for a black hole which evaporates slowly enough and whose mass is far greater than the Planck mass. The statistical-mechanical entropy is also proportional to the area of the black hole horizon. The difference from the stationary black hole is that the result relies on a time-dependent cutoff

Minimum entropy principle-based solar cell operation without a pn-junction and a thin CdS layer to extract the holes from the emitter

Science.gov (United States)

Böer, Karl W.

2016-10-01

The solar cell does not use a pn-junction to separate electrons from holes, but uses an undoped CdS layer that is p-type inverted when attached to a p-type collector and collects the holes while rejecting the backflow of electrons and thereby prevents junction leakage. The operation of the solar cell is determined by the minimum entropy principle of the cell and its external circuit that determines the electrochemical potential, i.e., the Fermi-level of the base electrode to the operating (maximum power point) voltage. It leaves the Fermi level of the metal electrode of the CdS unchanged, since CdS does not participate in the photo-emf. All photoelectric actions are generated by the holes excited from the light that causes the shift of the quasi-Fermi levels in the generator and supports the diffusion current in operating conditions. It is responsible for the measured solar maximum power current. The open circuit voltage (Voc) can approach its theoretical limit of the band gap of the collector at 0 K and the cell increases the efficiency at AM1 to 21% for a thin-film CdS/CdTe that is given as an example here. However, a series resistance of the CdS forces a limitation of its thickness to preferably below 200 Å to avoid unnecessary reduction in efficiency or Voc. The operation of the CdS solar cell does not involve heated carriers. It is initiated by the field at the CdS/CdTe interface that exceeds 20 kV/cm that is sufficient to cause extraction of holes by the CdS that is inverted to become p-type. Here a strong doubly charged intrinsic donor can cause a negative differential conductivity that switches-on a high-field domain that is stabilized by the minimum entropy principle and permits an efficient transport of the holes from the CdTe to the base electrode. Experimental results of the band model of CdS/CdTe solar cells are given and show that the conduction bands are connected in the dark, where the electron current must be continuous, and the valence bands are

The southern ozone hole as observed at Belgrano station

OpenAIRE

SILBERGLEIT, VIRGINIA

2000-01-01

The thinning of the stratosphere ozone layer in the Antarctic region is studied by considering ground-based observations at Belgrano Station (78.0°S; 38.8°W). Gumbel's first distribution of extreme values is used to evaluate the highest depletion of the Southern ozone hole for the spring months of 1998. According to the present study we predict that the expected largest yearly deviation of the ozone layer density during 1998 would be (109 ± 15)DU. This result agrees remarkably well with the m...

Layer-dependent band alignment and work function of few-layer phosphorene.

Science.gov (United States)

Cai, Yongqing; Zhang, Gang; Zhang, Yong-Wei

2014-10-20

Using first-principles calculations, we study the electronic properties of few-layer phosphorene focusing on layer-dependent behavior of band gap, work function band alignment and carrier effective mass. It is found that few-layer phosphorene shows a robust direct band gap character, and its band gap decreases with the number of layers following a power law. The work function decreases rapidly from monolayer (5.16 eV) to trilayer (4.56 eV), and then slowly upon further increasing the layer number. Compared to monolayer phosphorene, there is a drastic decrease of hole effective mass along the ridge (zigzag) direction for bilayer phosphorene, indicating a strong interlayer coupling and screening effect. Our study suggests that 1). Few-layer phosphorene with a layer-dependent band gap and a robust direct band gap character is promising for efficient solar energy harvest. 2). Few-layer phosphorene outperforms monolayer counterpart in terms of a lighter carrier effective mass, a higher carrier density and a weaker scattering due to enhanced screening. 3). The layer-dependent band edges and work functions of few-layer phosphorene allow for modification of Schottky barrier with enhanced carrier injection efficiency. It is expected that few-layer phosphorene will present abundant opportunities for a plethora of new electronic applications.

Graded Recombination Layers for Multijunction Photovoltaics

KAUST Repository

Koleilat, Ghada I.; Wang, Xihua; Sargent, Edward H.

2012-01-01

it to achieve multicolor and spectrally tunable behavior. In series-connected current-matched multijunction devices, the recombination layers must allow the hole current from one cell to recombine, with high efficiency and low voltage loss, with the electron

Low-cost copper complexes as p-dopants in solution processable hole transport layers

Energy Technology Data Exchange (ETDEWEB)

Kellermann, Renate [Department for Materials Science and Engineering, Chair for Materials for Electronics and Energy Technology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen 91058 (Germany); Siemens AG – Corporate Technology, Guenther-Scharowsky-Str. 1, Erlangen 91058 (Germany); Taroata, Dan; Maltenberger, Anna; Hartmann, David; Schmid, Guenter [Siemens AG – Corporate Technology, Guenther-Scharowsky-Str. 1, Erlangen 91058 (Germany); Brabec, Christoph J. [Department for Materials Science and Engineering, Chair for Materials for Electronics and Energy Technology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen 91058 (Germany)

2015-09-07

We demonstrate the usage of the Lewis-acidic copper(II)hexafluoroacetylacetonate (Cu(hfac){sub 2}) and copper(II)trifluoroacetylacetonate (Cu(tfac){sub 2}) as low-cost p-dopants for conductivity enhancement of solution processable hole transport layers based on small molecules in organic light emitting diodes (OLEDs). The materials were clearly soluble in mixtures of environmentally friendly anisole and xylene and spin-coated under ambient atmosphere. Enhancements of two and four orders of magnitude, reaching 4.0 × 10{sup −11} S/cm with a dopant concentration of only 2 mol% Cu(hfac){sub 2} and 1.5 × 10{sup −9} S/cm with 5 mol% Cu(tfac){sub 2} in 2,2′,7,7′-tetra(N,N-ditolyl)amino-9,9-spiro-bifluorene (spiro-TTB), respectively, were achieved. Red light emitting diodes were fabricated with reduced driving voltages and enhanced current and power efficiencies (8.6 lm/W with Cu(hfac){sub 2} and 5.6 lm/W with Cu(tfac){sub 2}) compared to the OLED with undoped spiro-TTB (3.9 lm/W). The OLED with Cu(hfac){sub 2} doped spiro-TTB showed an over 8 times improved LT{sub 50} lifetime of 70 h at a starting luminance of 5000 cd/m{sup 2}. The LT{sub 50} lifetime of the reference OLED with PEDOT:PSS was only 8 h. Both non-optimized OLEDs were operated at similar driving voltage and power efficiency.

Al2O3 dielectric layers on H-terminated diamond: Controlling surface conductivity

Science.gov (United States)

Yang, Yu; Koeck, Franz A.; Dutta, Maitreya; Wang, Xingye; Chowdhury, Srabanti; Nemanich, Robert J.

2017-10-01

This study investigates how the surface conductivity of H-terminated diamond can be preserved and stabilized by using a dielectric layer with an in situ post-deposition treatment. Thin layers of Al2O3 were grown by plasma enhanced atomic layer deposition (PEALD) on H-terminated undoped diamond (100) surfaces. The changes of the hole accumulation layer were monitored by correlating the binding energy of the diamond C 1s core level with electrical measurements. The initial PEALD of 1 nm Al2O3 resulted in an increase of the C 1s core level binding energy consistent with a reduction of the surface hole accumulation and a reduction of the surface conductivity. A hydrogen plasma step restored the C 1s binding energy to the value of the conductive surface, and the resistance of the diamond surface was found to be within the range for surface transfer doping. Further, the PEALD growth did not appear to degrade the surface conductive layer according to the position of the C 1s core level and electrical measurements. This work provides insight into the approaches to establish and control the two-dimensional hole-accumulation layer of the H-terminated diamond and improve the stability and performance of H-terminated diamond electronic devices.

Black hole astrophysics

International Nuclear Information System (INIS)

Blandford, R.D.; Thorne, K.S.

1979-01-01

Following an introductory section, the subject is discussed under the headings: on the character of research in black hole astrophysics; isolated holes produced by collapse of normal stars; black holes in binary systems; black holes in globular clusters; black holes in quasars and active galactic nuclei; primordial black holes; concluding remarks on the present state of research in black hole astrophysics. (U.K.)

Overview of Hole GT2A: Drilling middle gabbro in Wadi Tayin massif, Oman ophiolite

Science.gov (United States)

Takazawa, E.; Kelemen, P. B.; Teagle, D. A. H.; Coggon, J. A.; Harris, M.; Matter, J. M.; Michibayashi, K.

2017-12-01

Hole GT2A (UTM: 40Q 655960.7E / 2529193.5N) was drilled by the Oman Drilling Project (OmDP) into Wadi Gideah of Wadi Tayin massif in the Samail ophiolite, Oman. OmDP is an international collaboration supported by the International Continental Scientific Drilling Program, the Deep Carbon Observatory, NSF, IODP, JAMSTEC, and the European, Japanese, German and Swiss Science Foundations, with in-kind support in Oman from the Ministry of Regional Municipalities and Water Resources, Public Authority of Mining, Sultan Qaboos University, and the German University of Technology. Hole GT2A was diamond cored in 25 Dec 2016 to 18 Jan 2017 to a total depth of 406.77 m. The outer surfaces of the cores were imaged and described on site before being curated, boxed and shipped to the IODP drill ship Chikyu, where they underwent comprehensive visual and instrumental analysis. 33 shipboard scientists were divided into six teams (Igneous, Alteration, Structural, Geochem, Physical Properties, Paleomag) to describe and analyze the cores. Hole GT2A drilled through the transition between foliated and layered gabbro. The transition zone occurs between 50 and 150 m curation corrected depth (CCD). The top 50 m of Hole GT2A is foliated gabbro whereas the bottom 250 m consists of layered gabbro. Brittle fracture is observed throughout the core. Intensity of alteration vein decreases from the top to the bottom of the hole. On the basis of changes in grain size and/or modal abundance and/or appearance/disappearance of igneous primary mineral(s) five lithological units are defined in Hole GT2A (Unit I to V). The uppermost part of Hole GT2A (Unit I) is dominated by fine-grained granular olivine gabbro intercalated with less dominant medium-grained granular olivine gabbro and rare coarse-grained varitextured gabbro. The lower part of the Hole (Units II, III and V) is dominated by medium-grained olivine gabbro, olivine melagabbro and olivine-bearing gabbro. Modally-graded rhythmic layering with

Atomic layer deposition overcoating: tuning catalyst selectivity for biomass conversion.

Science.gov (United States)

Zhang, Hongbo; Gu, Xiang-Kui; Canlas, Christian; Kropf, A Jeremy; Aich, Payoli; Greeley, Jeffrey P; Elam, Jeffrey W; Meyers, Randall J; Dumesic, James A; Stair, Peter C; Marshall, Christopher L

2014-11-03

The terraces, edges, and facets of nanoparticles are all active sites for heterogeneous catalysis. These different active sites may cause the formation of various products during the catalytic reaction. Here we report that the step sites of Pd nanoparticles (NPs) can be covered precisely by the atomic layer deposition (ALD) method, whereas the terrace sites remain as active component for the hydrogenation of furfural. Increasing the thickness of the ALD-generated overcoats restricts the adsorption of furfural onto the step sites of Pd NPs and increases the selectivity to furan. Furan selectivities and furfural conversions are linearly correlated for samples with or without an overcoating, though the slopes differ. The ALD technique can tune the selectivity of furfural hydrogenation over Pd NPs and has improved our understanding of the reaction mechanism. The above conclusions are further supported by density functional theory (DFT) calculations. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of a Device for a Material Irradiation Test in the OR Test Hole

Energy Technology Data Exchange (ETDEWEB)

Cho, Man Soon; Kang, Y. H.; Kim, B. G.; Choo, K. N.; Sohn, J. M.; Shin, Y. T.; Park, S. J.; Seo, C. K

2008-05-15

To develop a technology and a device for the irradiation test for utilization of the OR/IP holes according to the various requirements of users, the properties of the OR/IP holes were investigated and an irradiation device for the OR hole was designed and fabricated. The OR-4, 5 and the IP-9, 10, 11 holes were selected as those suitable to irradiation tests among the test holes located in the out core area. The conceptual design was performed to design a device to irradiate materials using the OR and IP holes. The capsule for the OR holes is fixed by pressing the protection tube using a clamping device, on the other hand the IP capsule is inserted in the hole without a special clamping device. In the basic design of the irradiation device for the OR hole, the capsules having the outside diameter of 50, 52, 54, 56mm were reviewed theoretically to investigate if they meet the hydraulic and vibration conditions required in the HANARO. The results of the pressure drop test showed that the 3 kinds of capsules having diameter of 52, 54, 56mm satisfied the requirement for the pressure difference and flow rate in HANARO. The capsule of {phi}56mm out of the above three satisfied the vibration condition and was finally selected giving consideration of a capacity of specimens. The capsule having a diameter of {phi}56mm was fabricated and the flow rate was measured. Using the velocity data measured at the out-core facility, the heat transfer coefficient, and the temperature on the surface of the capsule was evaluated to confirm it less than the ONB temperature. As a result, the capsule of {phi}56mm was selected for the irradiation test at the OR holes.

Japan's exploration of vertical holes and subsurface caverns on the Moon and Mars

Science.gov (United States)

Haruyama, J.; Kawano, I.; Kubota, T.; Yoshida, K.; Kawakatsu, Y.; Kato, H.; Otsuki, M.; Watanabe, K.; Nishibori, T.; Yamamoto, Y.; Iwata, T.; Ishigami, G.; Yamada, T. T.

2013-12-01

Recently, gigantic vertical holes exceeding several tens of meters in diameter and depth were discovered on the Moon and Mars. Based on high-resolution image data, lunar holes and some Martian pits (called 'holes' hereafter) are probably skylights of subsurface caverns such as lava tubes or magma chambers. We are starting preparations for exploring the caverns through the vertical holes. The holes and subsurface caverns have high potential as resources for scientific studies. Various important geological and mineralogical processes could be uniquely and effectively observed inside these holes and subsurface caverns. The exposed fresh lava layers on the vertical walls of the lunar and Martian holes would provide information on volcanic eruption histories. The lava layers may also provide information on past magnetic fields of the celestial bodies. The regolith layers may be sandwiched between lava layers and may preserve volatile elements including solar wind protons that could be a clue to understanding past solar activities. Water molecules from solar winds or cometary/meteorite impacts may be stored inside the caverns because of mild temperatures there. The fresh lava materials forming the walls and floors of caverns might trap endogenic volatiles from magma eruptions that will be key materials for revealing the formation and early evolution of the Moon and Mars. Furthermore, the Martian subsurface caverns are highly expected to be life cradles where the temperatures are probably stable and that are free from ultra-violet and other cosmic rays that break chemical bonds, thus avoiding polymerization of molecules. Discovering extraterrestrial life and its varieties is one of our ultimate scientific purposes for exploring the lunar and Martian subsurface caverns. In addition to scientific interests, lunar and Martian subsurface caverns are excellent candidates for future lunar bases. We expect such caverns to have high potential due to stable temperatures; absence

SHORT-PULSE ELECTROMAGNETIC TRANSPONDER FOR HOLE-TO-HOLE USE.

Science.gov (United States)

Wright, David L.; Watts, Raymond D.; Bramsoe, Erik

1983-01-01

Hole-to-hole observations were made through nearly 20 m of granite using an electromagnetic transponder (an active reflector) in one borehole and a single-hole short-pulse radar in another. The transponder is inexpensive, operationally simple, and effective in extending the capability of a short-pulse borehole radar system to allow hole-to-hole operation without requiring timing cables. A detector in the transponder senses the arrival of each pulse from the radar. Each pulse detection triggers a kilovolt-amplitude pulse for retransmission. The transponder 'echo' may be stronger than that of a passive reflector by a factor of as much as 120 db. The result is an increase in range capability by a factor which depends on attenuation in the medium and hole-to-hole wavepath geometry.

Could there be a hole in type Ia supernovae?

International Nuclear Information System (INIS)

Kasen, Daniel; Nugent, Peter; Thomas, R.C.; Wang, Lifan

2004-01-01

In the favored progenitor scenario, Type Ia supernovae (SNe Ia) arise from a white dwarf accreting material from a non-degenerate companion star. Soon after the white dwarf explodes, the ejected supernova material engulfs the companion star; two-dimensional hydrodynamical simulations by Marietta et al. (2001) show that, in the interaction, the companion star carves out a conical hole of opening angle 30-40 degrees in the supernova ejecta. In this paper we use multi-dimensional Monte Carlo radiative transfer calculations to explore the observable consequences of an ejecta-hole asymmetry. We calculate the variation of the spectrum, luminosity, and polarization with viewing angle for the aspherical supernova near maximum light. We find that the supernova looks normal from almost all viewing angles except when one looks almost directly down the hole. In the latter case, one sees into the deeper, hotter layers of ejecta. The supernova is relatively brighter and has a peculiar spectrum characterized by more highly ionized species, weaker absorption features, and lower absorption velocities. The spectrum viewed down the hole is comparable to the class of SN 1991T-like supernovae. We consider how the ejecta-hole asymmetry may explain the current spectropolarimetric observations of SNe Ia, and suggest a few observational signatures of the geometry. Finally, we discuss the variety currently seen in observed SNe Ia and how an ejecta-hole asymmetry may fit in as one of several possible sources of diversity

Time-of-flight Measurement Of Hole-tunneling Properties And Emission Color Control In Organic Light-emitting Diodes

Science.gov (United States)

Kurata, K.; Kashiwabara, K.; Nakajima, K.; Mizoguchi, Y.; Ohtani, N.

2011-12-01

Hole transport properties of organic light-emitting diodes (OLEDs) with a thin hole-blocking layer (HBL) were evaluated by time-of-flight measurement. Electroluminescence (EL) spectra of OLEDs with various HBL thicknesses were also evaluated. The results clearly show that the time-resolved photocurrent response and the emission color strongly depend on HBL thickness. This can be attributed to hole-tunneling through the thin HBL. We successfully fabricated a white OLED by controlling the thickness of HBL.

Australian Students' Appreciation of the Greenhouse Effect and the Ozone Hole.

Science.gov (United States)

Fisher, Brian

1998-01-01

Examines students' explanations of the greenhouse effect and the hole in the ozone layer, using a life-world and scientific dichotomy. Illuminates ideas often expressed in classrooms and sheds light on the progression in students' developing powers of explanation. Contains 17 references. (DDR)

Black holes

OpenAIRE

Brügmann, B.; Ghez, A. M.; Greiner, J.

2001-01-01

Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries.

Observations of electron phase-space holes driven during magnetic reconnection in a laboratory plasma

Science.gov (United States)

Fox, W.; Porkolab, M.; Egedal, J.; Katz, N.; Le, A.

2012-03-01

This work presents detailed experimental observations of electron phase-space holes driven during magnetic reconnection events on the Versatile Toroidal Facility. The holes are observed to travel on the order of or faster than the electron thermal speed, and are of large size scale, with diameter of order 60 Debye lengths. In addition, they have 3D spheroidal structure with approximately unity aspect ratio. We estimate the direct anomalous resistivity due to ion interaction with the holes and find it to be too small to affect the reconnection rate; however, the holes may play a role in reining in a tail of accelerated electrons and they indicate the presence of other processes in the reconnection layer, such as electron energization and electron beam formation.

Synthesis and properties of a spirobifluorene-based hole-transporting material containingtert-butyl group

Directory of Open Access Journals (Sweden)

DING Ning

2016-12-01

Full Text Available A spirobifluorene-based compound SPF-BMO was developed as hole transporters for green phosphorescent organic light-emitting diodes(PhOLEDs.The synthesized material showed sufficient HOMO/LUMO bandgap and triplet energy for green emitting bis［2-(2-pyridinyl-Nphenyl-C］ (acetylacetonato iridium(III ［Ir (ppy2(acac］.The addition of a thin layer of 4,4′,4″-tri(N-carbazolyltriphenylamine (TCTAwith a high triplet energy as an exciton-blockinglayer at hole transporter/emitter interface seems to be unnecessary.SPF-BMO showed high thermal stability due to its spiro-annulated structure.Compared with the standard green PhOLEDs,organic light-emitting diodes with SPF-BMO as the hole-transport material have improved performances such as enhanced device power efficiency andlonger stability.These results clearly demonstrate that SPF-BMO is among the best hole-transporting materials reported for green PhOLEDs and utilizing anappropriate hole transporter to construct a simplified device is a promising method to enhance the power efficiency of PhOLEDs.

Observation of Enhanced Hole Extraction in Br Concentration Gradient Perovskite Materials.

Science.gov (United States)

Kim, Min-Cheol; Kim, Byeong Jo; Son, Dae-Yong; Park, Nam-Gyu; Jung, Hyun Suk; Choi, Mansoo

2016-09-14

Enhancing hole extraction inside the perovskite layer is the key factor for boosting photovoltaic performance. Realization of halide concentration gradient perovskite materials has been expected to exhibit rapid hole extraction due to the precise bandgap tuning. Moreover, a formation of Br-rich region on the tri-iodide perovskite layer is expected to enhance moisture stability without a loss of current density. However, conventional synthetic techniques of perovskite materials such as the solution process have not achieved the realization of halide concentration gradient perovskite materials. In this report, we demonstrate the fabrication of Br concentration gradient mixed halide perovskite materials using a novel and facile halide conversion method based on vaporized hydrobromic acid. Accelerated hole extraction and enhanced lifetime due to Br gradient was verified by observing photoluminescence properties. Through the combination of secondary ion mass spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopy analysis, the diffusion behavior of Br ions in perovskite materials was investigated. The Br-gradient was found to be eventually converted into a homogeneous mixed halide layer after undergoing an intermixing process. Br-substituted perovskite solar cells exhibited a power conversion efficiency of 18.94% due to an increase in open circuit voltage from 1.08 to 1.11 V and an advance in fill-factor from 0.71 to 0.74. Long-term stability was also dramatically enhanced after the conversion process, i.e., the power conversion efficiency of the post-treated device has remained over 97% of the initial value under high humid conditions (40-90%) without any encapsulation for 4 weeks.

Characteristics of organic light emitting diodes with copper iodide as injection layer

Energy Technology Data Exchange (ETDEWEB)

Stakhira, P., E-mail: stakhira@polynet.lviv.u [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Cherpak, V.; Volynyuk, D.; Ivastchyshyn, F. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Hotra, Z. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Rzeszow University of Technology, W. Pola 2, Rzeszow, 35-959 (Poland); Tataryn, V. [Lviv Polytechnic National University, S. Bandera, 12, Lviv, 79013 (Ukraine); Luka, G. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)

2010-09-30

We have studied the use of a thin copper iodide (CuI) film as an efficient injection layer of holes from indium tin oxide (ITO) anode in a light-emitting diode structure based on tris-8-hydroxyquinoline aluminium (Alq3). The results of impedance analysis of two types of diode structures, ITO/CuI/Alq3/poly(ethylene glycol) dimethyl ether/Al and ITO/Alq3/poly(ethylene glycol) dimethyl ether/Al, are presented. Comparative analysis of their current density-voltage, luminance-voltage and impedance characteristics shows that presence of CuI layer facilitates injection of holes from ITO anode into the light-emitting layer Alq3 and increases electroluminescence efficiency of the organic light emitting diodes.

Ultrafast optical control of terahertz surface plasmons in subwavelength hole-arrays at room temperature

Energy Technology Data Exchange (ETDEWEB)

Azad, Abul Kalam [Los Alamos National Laboratory; Chen, Hou - Tong [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; O' Hara, John [Los Alamos National Laboratory

2010-12-10

Extraordinary optical transmission through subwavelength metallic hole-arrays has been an active research area since its first demonstration. The frequency selective resonance properties of subwavelength metallic hole arrays, generally known as surface plasmon polaritons, have potential use in functional plasmonic devices such as filters, modulators, switches, etc. Such plasmonic devices are also very promising for future terahertz applications. Ultrafast switching or modulation of the resonant behavior of the 2-D metallic arrays in terahertz frequencies is of particular interest for high speed communication and sensing applications. In this paper, we demonstrate optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a conductive layer in the substrate reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of {approx}10 ps. We also present resonant terahertz transmission in a hybrid plasmonic film comprised of an integrated array of subwavelength metallic islands and semiconductor holes. A large dynamic transition between a dipolar localized surface plasmon mode and a surface plasmon resonance near 0.8 THz is observed under near infrared optical excitation. The reversal in transmission amplitude from a stopband to a passband and up to {pi}/2 phase shift achieved in the hybrid plasmonic film make it promising in large dynamic phase modulation, optical changeover switching, and active terahertz plasmonics.

Effect of organic small-molecule hole injection materials on the performance of inverted organic solar cells

Science.gov (United States)

Li, Jie; Zheng, Yifan; Zheng, Ding; Yu, Junsheng

2016-07-01

In this study, the influence of small-molecule organic hole injection materials on the performance of organic solar cells (OSCs) as the hole transport layer (HTL) with an architecture of ITO/ZnO/P3HT:PC71BM/HTL/Ag has been investigated. A significant enhancement on the performance of OSCs from 1.06% to 2.63% is obtained by using N, N‧-bis(1-naphthalenyl)-N, N‧-bis-phenyl-(1, 1‧-biphenyl)-4, 4‧-diamine (NPB) HTL. Through the resistance simulation and space-charge limited current analysis, we found that NPB HTL cannot merely improve the hole mobility of the device but also form the Ohmic contact between the active layer and anode. Besides, when we apply mix HTL by depositing the NPB on the surface of molybdenum oxide, the power conversion efficiency of OSC are able to be further improved to 2.96%.

The effect of the gas factor on selecting the thickness of a layer during two-layer getting of thick seams. [USSR

Energy Technology Data Exchange (ETDEWEB)

Varekha, Zh P; Kurkin, A S; Vechera, V N

1979-01-01

For technico-economic verification of the selection of the efficient removed thickness of upper and lower layers under conditions of high gas abundance of seams, the KNIUI has developed an economic model of converted costs within a getting field, allowing for natural and technical factors. The calculation considers specific costs for stoping work when getting the upper and lower layers, digging and maintenance of development workings, coal transport, assembly-disassembly work, ventilation, labor costs, degassing, etc. The calculation dependences and nomogram obtained enable comparatively easy definition of efficient thicknesses of removed layers when designing stoping work at thick, gently sloping seams, as well as calculation converted costs using as the initial data the total thickness of the seam, its natural gas content, and the expected degree of preliminary degassing.

Neutrino constraints that transform black holes into grey holes

International Nuclear Information System (INIS)

Ruderfer, M.

1982-01-01

Existing black hole theory is found to be defective in its neglect of the physical properties of matter and radiation at superhigh densities. Nongravitational neutrino effects are shown to be physically relevant to the evolution of astronomical black holes and their equations of state. Gravitational collapse to supernovae combined with the Davis and Ray vacuum solution for neutrinos limit attainment of a singularity and require black holes to evolve into ''grey holes''. These allow a better justification than do black holes for explaining the unique existence of galactic masses. (Auth.)

Analysis of the equalizing holes resistance in fuel assembly spike for lead-based reactor

International Nuclear Information System (INIS)

Zhang, Guangyu; Jin, Ming; Wang, Jianye; Song, Yong

2017-01-01

Highlights: • A RELAP5 model for a 10 MWth lead-based reactor was built to study the hydrodynamic characteristics between the equalizing holes in the fuel assembly spike. • Different fuel assembly total blockage scenarios and different resistances for different fuel assemblies were examined. • The inherent safety characteristics of the lead-based reactor was improved by optimizing the configuration of equalizing holes in the fuel assembly spike. - Abstract: To avoid the damage of the fuel rod cladding when a fuel assembly (FA) is totally blocked, a special configuration of the fuel assembly spike was designed with some equalizing holes in the center region which can let the coolant to flow during the totally blockage scenarios of FA. To study the hydrodynamic characteristics between the equalizing holes and an appropriate resistance, a RELAP5 model was developed for a 10 MWth lead-based reactor which used lead-bismuth as coolant. Several FA total blockage and partial core blockage scenarios were selected. The simulation results indicated that when all the FA spike equalizing holes had the same hydraulic resistance, only a narrow range of suitable equalizing holes resistances could be chosen when a FA was blocked. However, in the two or more FA blockage scenarios, there were no appropriate resistances to meet the requirement. In addition, with different FA spike equalizing holes with different resistances, a large range of suitable equalizing hole resistances could be chosen. Especially a series of suitable resistances were selected when the small power FA resistance was 1/2, 1/4, 1/8 of the large one. Under these circumstances, one, two or three FA blockages would not damage the core. These demonstrated that selecting a series of suitable hydraulic resistances for the equalizing holes could improve the safety characteristics of the reactor effectively.

Two Hop Adaptive Vector Based Quality Forwarding for Void Hole Avoidance in Underwater WSNs.

Science.gov (United States)

Javaid, Nadeem; Ahmed, Farwa; Wadud, Zahid; Alrajeh, Nabil; Alabed, Mohamad Souheil; Ilahi, Manzoor

2017-08-01

Underwater wireless sensor networks (UWSNs) facilitate a wide range of aquatic applications in various domains. However, the harsh underwater environment poses challenges like low bandwidth, long propagation delay, high bit error rate, high deployment cost, irregular topological structure, etc. Node mobility and the uneven distribution of sensor nodes create void holes in UWSNs. Void hole creation has become a critical issue in UWSNs, as it severely affects the network performance. Avoiding void hole creation benefits better coverage over an area, less energy consumption in the network and high throughput. For this purpose, minimization of void hole probability particularly in local sparse regions is focused on in this paper. The two-hop adaptive hop by hop vector-based forwarding (2hop-AHH-VBF) protocol aims to avoid the void hole with the help of two-hop neighbor node information. The other protocol, quality forwarding adaptive hop by hop vector-based forwarding (QF-AHH-VBF), selects an optimal forwarder based on the composite priority function. QF-AHH-VBF improves network good-put because of optimal forwarder selection. QF-AHH-VBF aims to reduce void hole probability by optimally selecting next hop forwarders. To attain better network performance, mathematical problem formulation based on linear programming is performed. Simulation results show that by opting these mechanisms, significant reduction in end-to-end delay and better throughput are achieved in the network.

Site-selective spectroscopy of Er in GaN

International Nuclear Information System (INIS)

Dierolf, V.; Sandmann, C.; Zavada, J.; Chow, P.; Hertog, B.

2004-01-01

We investigated different Er 3+ defect sites found in Er-doped GaN layers by site-selective combined excitation-emission spectroscopy and studied the role of these sites in different direct and multistep excitation schemes. The layers were grown by molecular beam epitaxy and were 200 nm thick. Two majority sites were found along with several minority sites. The sites strongly differ in excitation and energy transfer efficiencies as well as branching ratios during relaxation. For this reason, relative emission intensities from these sites depend strongly on emission and excitation. The sites were identified for several transitions and a comprehensive list of energy levels has been compiled. One of the minority sites appears strongly under ultraviolet excitation above the GaN band gap suggesting that this site is an excellent trap for excitation energy of electron-hole pairs

Collaborative research: Dynamics of electrostatic solitary waves and their effects on current layers

Energy Technology Data Exchange (ETDEWEB)

Chen, Li-Jen

2014-04-18

The project has accomplished the following achievements including the goals outlined in the original proposal. Generation and measurements of Debye-scale electron holes in laboratory: We have generated by beam injections electron solitary waves in the LAPD experiments. The measurements were made possible by the fabrication of the state-of-the-art microprobes at UCLA to measure Debye-scale electric fields [Chiang et al., 2011]. We obtained a result that challenged the state of knowledge about electron hole generation. We found that the electron holes were not due to two-stream instability, but generated by a current-driven instability that also generated whistler-mode waves [Lefebvre et al., 2011, 2010b]. Most of the grant supported a young research scientist Bertrand Lefebvre who led the dissemination of the laboratory experimental results. In addition to two publications, our work relevant to the laboratory experiments on electron holes has resulted in 7 invited talks [Chen, 2007, 2009; Pickett et al., 2009a; Lefebvre et al., 2010a; Pickett et al., 2010; Chen et al., 2011c, b] (including those given by the co-I Jolene Pickett) and 2 contributed talks [Lefebvre et al., 2009b, a]. Discovery of elecctron phase-space-hole structure in the reconnection electron layer: Our theoretical analyses and simulations under this project led to the discovery of an inversion electric field layer whose phase-space signature is an electron hole within the electron diffusion layer in 2D anti-parallel reconnection [Chen et al., 2011a]. We carried out particle tracing studies to understand the electron orbits that result in the phase-space hole structure. Most importantly, we showed that the current density in the electron layer is limited in collisionless reconnection with negligible guide field by the cyclotron turning of meandering electrons. Comparison of electrostatic solitary waves in current layers observed by Cluster and in LAPD: We compared the ESWs observed in a supersubstorm

Rational Design of Molecular Hole-Transporting Materials for Perovskite Solar Cells: Direct versus Inverted Device Configurations.

Science.gov (United States)

Grisorio, Roberto; Iacobellis, Rosabianca; Listorti, Andrea; De Marco, Luisa; Cipolla, Maria Pia; Manca, Michele; Rizzo, Aurora; Abate, Antonio; Gigli, Giuseppe; Suranna, Gian Paolo

2017-07-26

Due to a still limited understanding of the reasons making 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD) the state-of-the-art hole-transporting material (HTM) for emerging photovoltaic applications, the molecular tailoring of organic components for perovskite solar cells (PSCs) lacks in solid design criteria. Charge delocalization in radical cationic states can undoubtedly be considered as one of the essential prerequisites for an HTM, but this aspect has been investigated to a relatively minor extent. In marked contrast with the 3-D structure of Spiro-OMeTAD, truxene-based HTMs Trux1 and Trux2 have been employed for the first time in PSCs fabricated with a direct (n-i-p) or inverted (p-i-n) architecture, exhibiting a peculiar behavior with respect to the referential HTM. Notwithstanding the efficient hole extraction from the perovskite layer exhibited by Trux1 and Trux2 in direct configuration devices, their photovoltaic performances were detrimentally affected by their poor hole transport. Conversely, an outstanding improvement of the photovoltaic performances in dopant-free inverted configuration devices compared to Spiro-OMeTAD was recorded, ascribable to the use of thinner HTM layers. The rationalization of the photovoltaic performances exhibited by different configuration devices discussed in this paper can provide new and unexpected prospects for engineering the interface between the active layer of perovskite-based solar cells and the hole transporters.

Spin-Selective Transmission and Devisable Chirality in Two-Layer Metasurfaces.

Science.gov (United States)

Li, Zhancheng; Liu, Wenwei; Cheng, Hua; Chen, Shuqi; Tian, Jianguo

2017-08-15

Chirality is a nearly ubiquitous natural phenomenon. Its minute presence in most naturally occurring materials makes it incredibly difficult to detect. Recent advances in metasurfaces indicate that they exhibit devisable chirality in novel forms; this finding offers an effective opening for studying chirality and its features in such nanostructures. These metasurfaces display vast possibilities for highly sensitive chirality discrimination in biological and chemical systems. Here, we show that two-layer metasurfaces based on twisted nanorods can generate giant spin-selective transmission and support engineered chirality in the near-infrared region. Two designed metasurfaces with opposite spin-selective transmission are proposed for treatment as enantiomers and can be used widely for spin selection and enhanced chiral sensing. Specifically, we demonstrate that the chirality in these proposed metasurfaces can be adjusted effectively by simply changing the orientation angle between the twisted nanorods. Our results offer simple and straightforward rules for chirality engineering in metasurfaces and suggest intriguing possibilities for the applications of such metasurfaces in spin optics and chiral sensing.

Photon-exchange energy transfer of an electron–hole plasma between quasi-two-dimensional semiconductor layers

International Nuclear Information System (INIS)

Lyo, S.K.

2012-01-01

Photon-mediated energy transfer is shown to play an important role for transfer of an electron–hole plasma between two quasi-two-dimensional quantum wells separated by a wide barrier. The magnitude and the dependence of the transfer rate of an electron–hole plasma on the temperature, the well-to-well distance, and the plasma density are compared with those of the standard Förster (i.e., dipolar) rate and also with the exciton transfer rate. The plasma transfer rate through the photon-exchange mechanism decays very slowly as a function of the well-to-well distance and is larger than the dipolar rate except for short distances. The transfer rate of plasmas saturates at high densities and decays rapidly with the temperature. - Highlights: ► We study energy transfer (ET) between two two-dimensional semiconductor quantum wells. ► We compare the ET rates of an electron–hole plasma (at a high density) and Mott excitons. ► We show that the proposed photon-exchange rate is practically dominant over the Förster rate. ► We examine the dependences of the ET rate on the temperature, density, and well-to-well distance.

Recovery and Lithologic Analysis of Sediment from Hole UT-GOM2-1-H002, Green Canyon 955, Northern Gulf of Mexico

Science.gov (United States)

Kinash, N.; Cook, A.; Sawyer, D.; Heber, R.

2017-12-01

In May 2017 the University of Texas led a drilling and pressure coring expedition in the northern Gulf of Mexico, UT-GOM2-01. The holes were located in Green Canyon Block 955, where the Gulf of Mexico Joint Industry Project Leg II identified an approximately 100m thick hydrate-filled course-grained levee unit in 2009. Two separate wells were drilled into this unit: Holes H002 and H005. In Hole H002, a cutting shoe drill bit was used to collect the pressure cores, and only 1 of the 8 cores collected was pressurized during recovery. The core recovery in Hole H002 was generally poor, about 34%, while the only pressurized core had 45% recovery. In Hole H005, a face bit was used during pressure coring where 13 cores were collected and 9 cores remained pressurized. Core recovery in Hole H005 was much higher, at about 75%. The type of bit was not the only difference between the holes, however. Drilling mud was used throughout the drilling and pressure coring of Hole H002, while only seawater was used during the first 80m of pressure cores collected in Hole H005. Herein we focus on lithologic analysis of Hole H002 with the goal of documenting and understanding core recovery in Hole H002 to compare with Hole H005. X-ray Computed Tomography (XCT) images were collected by Geotek on pressurized cores, mostly from Hole H005, and at Ohio State on unpressurized cores, mostly from Hole H002. The XCT images of unpressurized cores show minimal sedimentary structures and layering, unlike the XCT images acquired on the pressurized, hydrate-bearing cores. Only small sections of the unpressurized cores remained intact. The unpressurized cores appear to have two prominent facies: 1) silt that did not retain original sedimentary fabric and often was loose within the core barrel, and 2) dense mud sections with some sedimentary structures and layering present. On the XCT images, drilling mud appears to be concentrated on the sides of cores, but also appears in layers and fractures within

Selected Data for Wells and Test Holes Used in Structure-Contour Maps of the Inyan Kara Group, Minnekahta Limestone, Minnelusa Formation, Madison Limestone, and Deadwood Formation in the Black Hills Area, South Dakota

National Research Council Canada - National Science Library

Carter, Janet M

1999-01-01

This report presents selected data on wells and test holes that were used in the construction of structure-contour maps of selected formations that contain major aquifers in the Black Hills area of western South Dakota...

Primary black holes

International Nuclear Information System (INIS)

Novikov, I.; Polnarev, A.

1981-01-01

Proves are searched for of the formation of the so-called primary black holes at the very origin of the universe. The black holes would weigh less than 10 13 kg. The formation of a primary black hole is conditional on strong fluctuations of the gravitational field corresponding roughly to a half of the fluctuation maximally permissible by the general relativity theory. Only big fluctuations of the gravitational field can overcome the forces of the hot gas pressure and compress the originally expanding matter into a black hole. Low-mass black holes have a temperature exceeding that of the black holes formed from stars. A quantum process of particle formation, the so-called evaporation takes place in the strong gravitational field of a black hole. The lower the mass of the black hole, the shorter the evaporation time. The analyses of processes taking place during the evaporation of low-mass primary black holes show that only a very small proportion of the total mass of the matter in the universe could turn into primary black holes. (M.D.)

Unequivocal detection of ozone recovery in the Antarctic Ozone Hole through significant increases in atmospheric layers with minimum ozone

Science.gov (United States)

de Laat, Jos; van Weele, Michiel; van der A, Ronald

2015-04-01

An important new landmark in present day ozone research is presented through MLS satellite observations of significant ozone increases during the ozone hole season that are attributed unequivocally to declining ozone depleting substances. For many decades the Antarctic ozone hole has been the prime example of both the detrimental effects of human activities on our environment as well as how to construct effective and successful environmental policies. Nowadays atmospheric concentrations of ozone depleting substances are on the decline and first signs of recovery of stratospheric ozone and ozone in the Antarctic ozone hole have been observed. The claimed detection of significant recovery, however, is still subject of debate. In this talk we will discuss first current uncertainties in the assessment of ozone recovery in the Antarctic ozone hole by using multi-variate regression methods, and, secondly present an alternative approach to identify ozone hole recovery unequivocally. Even though multi-variate regression methods help to reduce uncertainties in estimates of ozone recovery, great care has to be taken in their application due to the existence of uncertainties and degrees of freedom in the choice of independent variables. We show that taking all uncertainties into account in the regressions the formal recovery of ozone in the Antarctic ozone hole cannot be established yet, though is likely before the end of the decade (before 2020). Rather than focusing on time and area averages of total ozone columns or ozone profiles, we argue that the time evolution of the probability distribution of vertically resolved ozone in the Antarctic ozone hole contains a better fingerprint for the detection of ozone recovery in the Antarctic ozone hole. The advantages of this method over more tradition methods of trend analyses based on spatio-temporal average ozone are discussed. The 10-year record of MLS satellite measurements of ozone in the Antarctic ozone hole shows a

Deposition of silver layer on different substrates

Science.gov (United States)

Krzemiński, J.; Kiełbasiński, K.; Szałapak, J.; Jakubowska, M.; MłoŻniak, A.; Zwierkowska, E.

2015-09-01

The hole process of producing continuous layer with silver nanoparticles is presented in this paper. First the ink preparation and then the spray process is shown and discussed. The silver layers were obtained on sodium glass substrate. Three different ink carriers were considered and the best one has been chosen. Spray coating process was carried out using special spray can. After obtaining sprayed layers the samples were sintered in several temperatures to investigate the lowest suitable sintering temperature. After that layers resistivity were measured. Then the silver layers were cracked to produce breakthrough fracture that was investigated by a scanning electron microscope. In this paper, the authors investigated the spray coating technique as an alternative to electroplating and other techniques, considering layer resistivity, thickness and production process.

From binary black hole simulation to triple black hole simulation

International Nuclear Information System (INIS)

Bai Shan; Cao Zhoujian; Han, Wen-Biao; Lin, Chun-Yu; Yo, Hwei-Jang; Yu, Jui-Ping

2011-01-01

Black hole systems are among the most promising sources for a gravitational wave detection project. Now, China is planning to construct a space-based laser interferometric detector as a follow-on mission of LISA in the near future. Aiming to provide some theoretical support to this detection project on the numerical relativity side, we focus on black hole systems simulation in this work. Considering the globular galaxy, multiple black hole systems also likely to exist in our universe and play a role as a source for the gravitational wave detector we are considering. We will give a progress report in this paper on our black hole system simulation. More specifically, we will present triple black hole simulation together with binary black hole simulation. On triple black hole simulations, one novel perturbational method is proposed.

Spectroelectrochemical evidence for the effect of phase structure and interface on charge behavior in poly(3-hexylthiophene): Fullerene active layer

International Nuclear Information System (INIS)

Hu, Rong; Ni, Haitao; Wang, Zhaodong; Liu, Yurong; Liu, Hongdong; Yang, Xin; Cheng, Jiang

2016-01-01

Highlights: • The steady-state absorption spectra of P3HT"·"+, P3HT"·"−, PCBM"+ and PCBM"− were obtained. • The effect of morphology of active layer on charge generation was identified. • Non-equilibrium transport of electron and hole was confirmed in PSCs. - Abstract: To investigate the correlation between morphology of active layer and performance of polymer solar cells (PSCs). Poly(3-hexylthiophene):[6,6]-phenyl-C_6_1-butyric acid methyl ester (P3HT:PCBM) were selected as research object and five PSCs based on active layers with varied morphology were fabricated. The results showed that P3HT crystalline phase and donor-acceptor (D-A) interface had an important influence on PSCs performance, which was revealed by structure characterization and J-V measurement. To further understanding the effect of phase structure and D-A interface on charge behavior. Spectroelectrochemistry measurement (SEC) was performed to characterize the steady-state optical absorption of P3HT, PCBM cation and anion in varied active layers, and the spectra difference of cations and anions was analyzed. The results were found that D-A interface could promote charge generation. P3HT crystalline phase and PCBM aggregation phase were beneficial for improving the charge transport ability. Meanwhile, the non-equilibrium transport of electron and hole in PSCs was corroborated by SEC.

Effect of atmospheric-pressure plasma treatment on the adhesion properties of a thin adhesive layer in a selective transfer process

Science.gov (United States)

Yoon, Min-Ah; Kim, Chan; Hur, Min; Kang, Woo Seok; Kim, Jaegu; Kim, Jae-Hyun; Lee, Hak-Joo; Kim, Kwang-Seop

2018-01-01

The adhesion between a stamp and thin film devices is crucial for their transfer on a flexible substrate. In this paper, a thin adhesive silicone layer on the stamp was treated by atmospheric pressure plasma to locally control the adhesion strength for the selective transfer. The adhesion strength of the silicone layer was significantly reduced after the plasma treatment, while its surface energy was increased. To understand the inconsistency between the adhesion strength and surface energy changes, the surface properties of the silicone layer were characterized using nanoindentation and X-ray photoelectron spectroscopy. These techniques revealed that a thin, hard, silica-like layer had formed on the surface from plasma-enhanced oxidation. This layer played an important role in decreasing the contact area and increasing the interfacial slippage, resulting in decreased adhesion. As a practical application, the transfer process was demonstrated on GaN LEDs that had been previously delaminated by a laser lift-off (LLO) process. Although the LEDs were not transferred onto the treated adhesive layer due to the reduced adhesion, the untreated adhesive layer could readily pick up the LEDs. It is expected that this simple method of controlling the adhesion of a stamp with a thin adhesive layer would enable a continuous, selective and large-scale roll-to-roll selective transfer process and thereby advance the development of flexible, stretchable and wearable electronics.

Tuning the dispersion and single/multi-modeness of a hole-assisted fiber by the hole's geometrical parameters

NARCIS (Netherlands)

Uranus, H.P.; Hoekstra, Hugo; van Groesen, Embrecht W.C.

2008-01-01

Using a vectorial finite element mode solver developed earlier, we studied a hole-assisted multi-ring fiber. We report the role of the hole’s geometrical parameters in tuning the waveguide dispersion and the single/multi-modeness of the particular fiber. By correctly selecting the hole’s size and

High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

KAUST Repository

Nazir, Safdar

2012-05-18

A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.

High mobility of the strongly confined hole gas in AgTaO3/SrTiO3

KAUST Repository

Nazir, Safdar; Schwingenschlö gl, Udo; Upadhyay Kahaly, M.

2012-01-01

A theoretical study of the two-dimensional hole gas at the (AgO)−/(TiO2)0 p-type interface in the AgTaO3/SrTiO3 (001) heterostructure is presented. The Ag 4d states strongly hybridize with the O 2p states and contribute to the hole gas. It is demonstrated that the holes are confined to an ultra thin layer (∼4.9Å) with a considerable carrier density of ∼1014cm−2. We estimate a hole mobility of 18.6 cm2 V−1 s−1, which is high enough to enable device applications.

Phase transition for black holes with scalar hair and topological black holes

International Nuclear Information System (INIS)

Myung, Yun Soo

2008-01-01

We study phase transitions between black holes with scalar hair and topological black holes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ black hole in three dimensions and topological black hole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between black hole with scalar hair (Martinez-Troncoso-Zanelli black hole) and topological black hole is second-order by using differences between two free energies. However, we do not identify what order of the phase transition between scalar and non-rotating BTZ black holes occurs in three dimensions, although there exists a possible decay of scalar black hole to non-rotating BTZ black hole

Optical properties of single-layer, double-layer, and bulk MoS2

Energy Technology Data Exchange (ETDEWEB)

Molina-Sanchez, Alejandro; Wirtz, Ludger [University of Luxembourg (Luxembourg); Hummer, Kerstin [University of Vienna, Vienna (Austria)

2013-07-01

The rise of graphene has brought attention also to other layered materials that can complement graphene or that can be an alternative in applications as transistors. Single-layer MoS{sub 2} has shown interesting electronic and optical properties such as as high electron mobility at room temperature and an optical bandgap of 1.8 eV. This makes the material suitable for transistors or optoelectronic devices. We present a theoretical study of the optical absorption and photoluminescence spectra of single-layer, double-layer and bulk MoS{sub 2}. The excitonic states have been calculated in the framework of the Bethe-Salpeter equation, taking into account the electron-hole interaction via the screened Coulomb potential. In addition to the step-function like behaviour that is typical for the joint-density of states of 2D materials with parabolic band dispersion, we find a bound excitonic peak that is dominating the luminescence spectra. The peak is split due to spin-orbit coupling for the single-layer and split due to layer-layer interaction for few-layer and bulk MoS{sub 2}. We discuss the changes of the optical bandgap and of the exciton binding energy with the number of layers, comparing our results with the reported experimental data.

Simulation of perovskite solar cells with inorganic hole transporting materials

DEFF Research Database (Denmark)

Wang, Yan; Xia, Zhonggao; Liu, Yiming

2015-01-01

Device modeling organolead halide perovskite solar cells with planar architecture based on inorganic hole transporting materials (HTMs) were performed. A thorough understanding of the role of the inorganic HTMs and the effect of band offset between HTM/absorber layers is indispensable for further...... improvement in power conversion efficiency (PCE). Here, we investigated the effect of band offset between inorganic HTM/absorber layers. The solar cell simulation program adopted in this work is named wxAMPS, an updated version of the AMPS tool (Analysis of Microelectronic and Photonic Structure)....

Optimal management of idiopathic macular holes

Directory of Open Access Journals (Sweden)

Madi HA

2016-01-01

Full Text Available Haifa A Madi,1,* Ibrahim Masri,1,* David H Steel1,2 1Sunderland Eye Infirmary, Sunderland, 2Institute of Genetic Medicine, Newcastle University, International Centre for Life, Newcastle, UK *These authors contributed equally to this work Abstract: This review evaluates the current surgical options for the management of idiopathic macular holes (IMHs, including vitrectomy, ocriplasmin (OCP, and expansile gas use, and discusses key background information to inform the choice of treatment. An evidence-based approach to selecting the best treatment option for the individual patient based on IMH characteristics and patient-specific factors is suggested. For holes without vitreomacular attachment (VMA, vitrectomy is the only option with three key surgical variables: whether to peel the inner limiting membrane (ILM, the type of tamponade agent to be used, and the requirement for postoperative face-down posturing. There is a general consensus that ILM peeling improves primary anatomical hole closure rate; however, in small holes (<250 µm, it is uncertain whether peeling is always required. It has been increasingly recognized that long-acting gas and face-down positioning are not always necessary in patients with small- and medium-sized holes, but large (>400 µm and chronic holes (>1-year history are usually treated with long-acting gas and posturing. Several studies on posturing and gas choice were carried out in combination with ILM peeling, which may also influence the gas and posturing requirement. Combined phacovitrectomy appears to offer more rapid visual recovery without affecting the long-term outcomes of vitrectomy for IMH. OCP is licensed for use in patients with small- or medium-sized holes and VMA. A greater success rate in using OCP has been reported in smaller holes, but further predictive factors for its success are needed to refine its use. It is important to counsel patients realistically regarding the rates of success with

Black Holes

OpenAIRE

Townsend, P. K.

1997-01-01

This paper is concerned with several not-quantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole space-times. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usu...

Simulation of hole mobility in two-dimensional systems

International Nuclear Information System (INIS)

Donetti, Luca; Gamiz, Francisco; Rodriguez, Noel

2009-01-01

We develop a fully self-consistent solver for the six-band k . p Schrödinger and Poisson equations to compute the valence-band structure of Si and Ge devices with arbitrary substrate orientation and uniaxial or biaxial strain. This allows us to compute the potential, charge distribution and subband energy dispersion relation for hole inversion layers in different devices and, using a simplex Monte Carlo simulator, to evaluate the low-field mobility. New procedures have been developed to calculate the scattering rates. The results obtained in the case of a (0 0 1) Si MOSFET device are compared with experimental mobility curves and a very good agreement is found. Then, hole mobility curves for different structures and crystallographic orientations both with strained and unstrained materials are evaluated

SURFACE LAYER ACCRETION IN TRANSITIONAL AND CONVENTIONAL DISKS: FROM POLYCYCLIC AROMATIC HYDROCARBONS TO PLANETS

International Nuclear Information System (INIS)

Perez-Becker, Daniel; Chiang, Eugene

2011-01-01

'Transitional' T Tauri disks have optically thin holes with radii ∼>10 AU, yet accrete up to the median T Tauri rate. Multiple planets inside the hole can torque the gas to high radial speeds over large distances, reducing the local surface density while maintaining accretion. Thus multi-planet systems, together with reductions in disk opacity due to grain growth, can explain how holes can be simultaneously transparent and accreting. There remains the problem of how outer disk gas diffuses into the hole. Here it has been proposed that the magnetorotational instability (MRI) erodes disk surface layers ionized by stellar X-rays. In contrast to previous work, we find that the extent to which surface layers are MRI-active is limited not by ohmic dissipation but by ambipolar diffusion, the latter measured by Am: the number of times a neutral hydrogen molecule collides with ions in a dynamical time. Simulations by Hawley and Stone showed that Am ∼ 100 is necessary for ions to drive MRI turbulence in neutral gas. We calculate that in X-ray-irradiated surface layers, Am typically varies from ∼10 -3 to 1, depending on the abundance of charge-adsorbing polycyclic aromatic hydrocarbons, whose properties we infer from Spitzer observations. We conclude that ionization of H 2 by X-rays and cosmic rays can sustain, at most, only weak MRI turbulence in surface layers 1-10 g cm -2 thick, and that accretion rates in such layers are too small compared to observed accretion rates for the majority of disks.

Tribochemical interaction between nanoparticles and surfaces of selective layer during chemical mechanical polishing

International Nuclear Information System (INIS)

Ilie, Filip

2013-01-01

Nanoparticles have been widely used in polish slurries such as those in the chemical mechanical polishing (CMP) process. For understanding the mechanisms of CMP, an atomic force microscope (AFM) is used to characterize polished surfaces of selective layers, after a set of polishing experiments. To optimize the CMP polishing process, one needs to get information on the interaction between the nano-abrasive slurry nanoparticles and the surface of selective layer being polished. The slurry used in CMP process of the solid surfaces is slurry with large nanoparticle size colloidal silica sol nano-abrasives. Silica sol nano-abrasives with large nanoparticle are prepared and characterized by transmission electron microscopy, particles colloidal size, and Zeta potential in this paper. The movement of nanoparticles in liquid and the interaction between nanoparticles and solid surfaces coating with selective layer are very important to obtain an atomic alloy smooth surface in the CMP process. We investigate the nanoparticle adhesion and removal processes during CMP and post-CMP cleaning. The mechanical interaction between nanoparticles and the wafer surface was studied using a microcontact wear model. This model considers the nanoparticle effects between the polishing interfaces during load balancing. Experimental results on polishing and cleaning are compared with numerical analysis. This paper suggests that during post-CMP cleaning, a combined effort in chemical and mechanical interaction (tribochemical interactions) would be effective in removal of small nanoparticles during cleaning. For large nanoparticles, more mechanical forces would be more effective. CMP results show that the removal rate has been improved to 367 nm/min and root mean square (RMS) of roughness has been reduced from 4.4 to 0.80 nm. Also, the results show that the silica sol nano-abrasives about 100 nm are of higher stability (Zeta potential is −65 mV) and narrow distribution of nanoparticle

Research of acceptor impurity thermal activation in GaN: Mg epitaxial layers

Directory of Open Access Journals (Sweden)

Aleksandr V. Mazalov

2016-06-01

The effect of thermal annealing of GaN:Mg layers on acceptor impurity activation has been investigated. Hole concentration increased and mobility decreased with an increase in thermal annealing temperature. The sample annealed at 1000 °C demonstrated the lowest value of resistivity. Rapid thermal annealing (annealing with high heating speed considerably improved the efficiency of Mg activation in the GaN layers. The optimum time of annealing at 1000 °C has been determined. The hole concentration increased by up to 4 times compared to specimens after conventional annealing.

Selective formation of porous layer on n-type InP by anodic etching combined with scratching

International Nuclear Information System (INIS)

Seo, Masahiro; Yamaya, Tadafumi

2005-01-01

The selective formation of porous layer on n-type InP (001) surface was investigated by using scratching with a diamond scriber followed by anodic etching in deaerated 0.5M HCl. Since the InP specimen was highly doped, the anodic etching proceeded in the dark. The potentiodynamic polarization showed the anodic current shoulder in the potential region between 0.8 and 1.3V (SHE) for the scratched area in addition to the anodic current peak at 1.7V (SHE) for the intact area. The selective formation of porous layer on the scratched are was brought by the anodic etching at a constant potential between 1.0 and 1.2V (SHE) for a certain time. The nucleation and growth of etch pits on intact area, however, took place when the time passed the critical value. The cross section of porous layer on the scratched area perpendicular to the [1-bar 10] or [110] scratching direction had a V-shape, while the cross section of porous layer on the scratched area parallel to the [1-bar 10] or [110] scratching direction had a band structure with stripes oriented to the [1-bar 11] or [11-bar 1] direction. Moreover, nano-scratching at a constant normal force in the micro-Newton range followed by anodic etching showed the possibility for selective formation of porous wire with a nano-meter width

Selective formation of porous layer on n-type InP by anodic etching combined with scratching

Energy Technology Data Exchange (ETDEWEB)

Seo, Masahiro [Graduate School of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, Sapporo 060-8628 (Japan)]. E-mail: seo@elechem1-mc.eng.hokudai.ac.jp; Yamaya, Tadafumi [Graduate School of Engineering, Hokkaido University, Kita-13 Jo, Nishi-8 Chome, Kita-ku, Sapporo 060-8628 (Japan)

2005-11-10

The selective formation of porous layer on n-type InP (001) surface was investigated by using scratching with a diamond scriber followed by anodic etching in deaerated 0.5M HCl. Since the InP specimen was highly doped, the anodic etching proceeded in the dark. The potentiodynamic polarization showed the anodic current shoulder in the potential region between 0.8 and 1.3V (SHE) for the scratched area in addition to the anodic current peak at 1.7V (SHE) for the intact area. The selective formation of porous layer on the scratched are was brought by the anodic etching at a constant potential between 1.0 and 1.2V (SHE) for a certain time. The nucleation and growth of etch pits on intact area, however, took place when the time passed the critical value. The cross section of porous layer on the scratched area perpendicular to the [1-bar 10] or [110] scratching direction had a V-shape, while the cross section of porous layer on the scratched area parallel to the [1-bar 10] or [110] scratching direction had a band structure with stripes oriented to the [1-bar 11] or [11-bar 1] direction. Moreover, nano-scratching at a constant normal force in the micro-Newton range followed by anodic etching showed the possibility for selective formation of porous wire with a nano-meter width.

Geometry and surface damage in micro electrical discharge machining of micro-holes

Science.gov (United States)

Ekmekci, Bülent; Sayar, Atakan; Tecelli Öpöz, Tahsin; Erden, Abdulkadir

2009-10-01

Geometry and subsurface damage of blind micro-holes produced by micro electrical discharge machining (micro-EDM) is investigated experimentally to explore the relational dependence with respect to pulse energy. For this purpose, micro-holes are machined with various pulse energies on plastic mold steel samples using a tungsten carbide tool electrode and a hydrocarbon-based dielectric liquid. Variations in the micro-hole geometry, micro-hole depth and over-cut in micro-hole diameter are measured. Then, unconventional etching agents are applied on the cross sections to examine micro structural alterations within the substrate. It is observed that the heat-damaged segment is composed of three distinctive layers, which have relatively high thicknesses and vary noticeably with respect to the drilling depth. Crack formation is identified on some sections of the micro-holes even by utilizing low pulse energies during machining. It is concluded that the cracking mechanism is different from cracks encountered on the surfaces when machining is performed by using the conventional EDM process. Moreover, an electrically conductive bridge between work material and debris particles is possible at the end tip during machining which leads to electric discharges between the piled segments of debris particles and the tool electrode during discharging.

Geometry and surface damage in micro electrical discharge machining of micro-holes

International Nuclear Information System (INIS)

Ekmekci, Bülent; Sayar, Atakan; Öpöz, Tahsin Tecelli; Erden, Abdulkadir

2009-01-01

Geometry and subsurface damage of blind micro-holes produced by micro electrical discharge machining (micro-EDM) is investigated experimentally to explore the relational dependence with respect to pulse energy. For this purpose, micro-holes are machined with various pulse energies on plastic mold steel samples using a tungsten carbide tool electrode and a hydrocarbon-based dielectric liquid. Variations in the micro-hole geometry, micro-hole depth and over-cut in micro-hole diameter are measured. Then, unconventional etching agents are applied on the cross sections to examine micro structural alterations within the substrate. It is observed that the heat-damaged segment is composed of three distinctive layers, which have relatively high thicknesses and vary noticeably with respect to the drilling depth. Crack formation is identified on some sections of the micro-holes even by utilizing low pulse energies during machining. It is concluded that the cracking mechanism is different from cracks encountered on the surfaces when machining is performed by using the conventional EDM process. Moreover, an electrically conductive bridge between work material and debris particles is possible at the end tip during machining which leads to electric discharges between the piled segments of debris particles and the tool electrode during discharging

Black hole based tests of general relativity

International Nuclear Information System (INIS)

Yagi, Kent; Stein, Leo C

2016-01-01

General relativity has passed all solar system experiments and neutron star based tests, such as binary pulsar observations, with flying colors. A more exotic arena for testing general relativity is in systems that contain one or more black holes. Black holes are the most compact objects in the Universe, providing probes of the strongest-possible gravitational fields. We are motivated to study strong-field gravity since many theories give large deviations from general relativity only at large field strengths, while recovering the weak-field behavior. In this article, we review how one can probe general relativity and various alternative theories of gravity by using electromagnetic waves from a black hole with an accretion disk, and gravitational waves from black hole binaries. We first review model-independent ways of testing gravity with electromagnetic/gravitational waves from a black hole system. We then focus on selected examples of theories that extend general relativity in rather simple ways. Some important characteristics of general relativity include (but are not limited to) (i) only tensor gravitational degrees of freedom, (ii) the graviton is massless, (iii) no quadratic or higher curvatures in the action, and (iv) the theory is four-dimensional. Altering a characteristic leads to a different extension of general relativity: (i) scalar–tensor theories, (ii) massive gravity theories, (iii) quadratic gravity, and (iv) theories with large extra dimensions. Within each theory, we describe black hole solutions, their properties, and current and projected constraints on each theory using black hole based tests of gravity. We close this review by listing some of the open problems in model-independent tests and within each specific theory. (paper)

Dissimilar mechanism of executing hole transfer by WO{sub 3} and MoO{sub 3} nanoparticles in organic solar cells

Energy Technology Data Exchange (ETDEWEB)

Park, Eung-Kyu; Kim, Jae-Hyoung; Kim, Ji-Hwan; Park, Min-Ho; Lee, Dong-Hoon; Kim, Yong-Sang, E-mail: yongsang@skku.edu

2015-07-31

We investigated the effect of metal oxide nanoparticles (NPs) in poly (3,4 ethylenedioxythiophence):poly (styrene-sulfonate) layer for the light harvestation in poly (3-hexylthiophene):[6,6]-pheny-C{sub 61}-butyric acid methyl ester organic solar cells. The role of tungsten trioxide nanoparticles (WO{sub 3}) and molybdenum trioxide nanoparticles (MoO{sub 3}) in enhancing the efficiency of solar cells was compared. Due to the difference in the energy band structure of the two nanoparticles, the WO{sub 3} NPs acted as a hole blocking layer, whereas MoO{sub 3} NPs helped in the hole transfer. The solar cell with WO{sub 3} NPs at 1.5 wt% concentration showed a power conversion efficiency of 4.22% under AM 1.5G illumination and the device blended with 2 wt% of MoO{sub 3} NPs showed a power conversion efficiency of 4.40%. We measured various electrical properties including, electrochemical impedance spectroscopy and recombination mechanisms using the light intensity dependent current–voltage measurement of organic solar cell. - Highlights: • An organic solar cell was fabricated with WO{sub 3} or MoO{sub 3} NPs mixed PEDOT:PSS layer. • The effects of metallic NPs in PEDOT:PSS light harvesting system was investigated. • WO{sub 3} NPs acted as a hole blocking layer and MoO{sub 3} NPs helped in hole transporting. • The MoO{sub 3} NPs gave higher performance, reduced charge recombination and low resistance.

Single-layer centrifugation through colloid selects improved quality of epididymal cat sperm.

Science.gov (United States)

Chatdarong, K; Thuwanut, P; Morrell, J M

2010-06-01

The objectives were to determine the: 1) extent of epithelial and red blood cell contamination in epididymal cat sperm samples recovered by the cutting method; 2) efficacy of simple washing, single-layer centrifugation (SLC), and swim-up for selecting epididymal cat sperm; and 3) effects of freezing and thawing on cat sperm selected by various techniques. Ten unit samples were studied; each contained sperm from the cauda epididymides of four cats (total, approximately 200 x 10(6) sperm) and was equally allocated into four treatments: 1) simple washing, 2) single-layer centrifugation through colloid prior to cryopreservation (SLC-PC), 3) single-layer centrifugation through colloid after cryopreservation (SLC-AC), and 4) swim-up. Centrifugation (300 x g for 20 min) was done for all methods. The SLC-PC had a better recovery rate than the SLC-AC and swim-up methods (mean+/-SD of 16.4+/-8.7, 10.7+/-8.9, and 2.3+/-1.7%, respectively; Pblood cell contamination than simple washed samples (0.02+/-0.01, 0.02+/-0.04, 0.03+/-0.04, and 0.44+/-0.22 x 10(6) cells/mL, respectively; P0.05), SLC-PC yielded the highest percentage of sperm with normal midpieces and tails (P0.05). In conclusion, both SLC-PC and swim-up improved the quality of epididymal cat sperm, including better morphology, membrane and DNA integrity, and removal of cellular contamination. However, SLC had a better sperm recovery rate than swim-up. 2010 Elsevier Inc. All rights reserved.

Characterization of solution processed, p-doped films using hole-only devices and organic field-effect transistors

Energy Technology Data Exchange (ETDEWEB)

Swensen, James S.; Wang, Liang (Frank); Rainbolt, James E.; Koech, Phillip K.; Polikarpov, Evgueni; Gaspar, Daniel J.; Padmaperuma, Asanga B.

2012-12-01

We report a solution-processed approach for a p-type doped hole transport layer in organic light emitting devices (OLEDs). UV-vis-NIR absorption spectra identified the charge transfer between the donor and acceptor in the solution processed doped films. Single carrier device and field-effect transistor were utilized as test vehicles to study the charge transport property and extract important parameters such as bulk mobile carrier concentration and mobility. OLEDs with p-type doped hole transport layer showed significant improvement in power efficiency up to 30% at the optimal doping ratio. This approach has the great potential to reduce the power consumption for OLED solid state lighting while lowering the cost and boosting the throughput of its manufacturing.

Piezo-Phototronic Effect on Selective Electron or Hole Transport through Depletion Region of Vis-NIR Broadband Photodiode.

Science.gov (United States)

Zou, Haiyang; Li, Xiaogan; Peng, Wenbo; Wu, Wenzhuo; Yu, Ruomeng; Wu, Changsheng; Ding, Wenbo; Hu, Fei; Liu, Ruiyuan; Zi, Yunlong; Wang, Zhong Lin

2017-08-01

Silicon underpins nearly all microelectronics today and will continue to do so for some decades to come. However, for silicon photonics, the indirect band gap of silicon and lack of adjustability severely limit its use in applications such as broadband photodiodes. Here, a high-performance p-Si/n-ZnO broadband photodiode working in a wide wavelength range from visible to near-infrared light with high sensitivity, fast response, and good stability is reported. The absorption of near-infrared wavelength light is significantly enhanced due to the nanostructured/textured top surface. The general performance of the broadband photodiodes can be further improved by the piezo-phototronic effect. The enhancement of responsivity can reach a maximum of 78% to 442 nm illumination, the linearity and saturation limit to 1060 nm light are also significantly increased by applying external strains. The photodiode is illuminated with different wavelength lights to selectively choose the photogenerated charge carriers (either electrons or holes) passing through the depletion region, to investigate the piezo-phototronic effect on electron or hole transport separately for the first time. This is essential for studying the basic principles in order to develop a full understanding about piezotronics and it also enables the development of the better performance of optoelectronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low-mass black holes as the remnants of primordial black hole formation.

Science.gov (United States)

Greene, Jenny E

2012-01-01

Bridging the gap between the approximately ten solar mass 'stellar mass' black holes and the 'supermassive' black holes of millions to billions of solar masses are the elusive 'intermediate-mass' black holes. Their discovery is key to understanding whether supermassive black holes can grow from stellar-mass black holes or whether a more exotic process accelerated their growth soon after the Big Bang. Currently, tentative evidence suggests that the progenitors of supermassive black holes were formed as ∼10(4)-10(5) M(⊙) black holes via the direct collapse of gas. Ongoing searches for intermediate-mass black holes at galaxy centres will help shed light on this formation mechanism.

Investigations on effects of the hole size to fix electrodes and interconnection lines in polydimethylsiloxane

Science.gov (United States)

Behkami, Saber; Frounchi, Javad; Ghaderi Pakdel, Firouz; Stieglitz, Thomas

2017-11-01

Translational research in bioelectronics medicine and neural implants often relies on established material assemblies made of silicone rubber (polydimethylsiloxane-PDMS) and precious metals. Longevity of the compound is of utmost importance for implantable devices in therapeutic and rehabilitation applications. Therefore, secure mechanical fixation can be used in addition to chemical bonding mechanisms to interlock PDMS substrate and insulation layers with metal sheets for interconnection lines and electrodes. One of the best ways to fix metal lines and electrodes in PDMS is to design holes in electrode rims to allow for direct interconnection between top to bottom layer silicone. Hence, the best layouts and sizes of holes (up to 6) which provide sufficient stability against lateral and vertical forces have been investigated with a variety of numbers of hole in line electrodes, which are simulated and fabricated with different layouts, sizes and materials. Best stability was obtained with radii of 100, 72 and 62 µm, respectively, and a single central hole in aluminum, platinum and MP35N foil line electrodes of 400  ×  500 µm2 size and of thickness 20 µm. The study showed that the best hole size which provides line electrode immobility (of thickness less than 30 µm) within a central hole is proportional to reverse value of Young’s Modulus of the material used. Thus, an array of line electrodes was designed and fabricated to study this effect. Experimental results were compared with simulation data. Subsequently, an approximation curve was generated as design rule to propose the best radius to fix line electrodes according to the material thickness between 10 and 200 µm using PDMS as substrate material.

Subset of Cortical Layer 6b Neurons Selectively Innervates Higher Order Thalamic Nuclei in Mice.

Science.gov (United States)

Hoerder-Suabedissen, Anna; Hayashi, Shuichi; Upton, Louise; Nolan, Zachary; Casas-Torremocha, Diana; Grant, Eleanor; Viswanathan, Sarada; Kanold, Patrick O; Clasca, Francisco; Kim, Yongsoo; Molnár, Zoltán

2018-05-01

The thalamus receives input from 3 distinct cortical layers, but input from only 2 of these has been well characterized. We therefore investigated whether the third input, derived from layer 6b, is more similar to the projections from layer 6a or layer 5. We studied the projections of a restricted population of deep layer 6 cells ("layer 6b cells") taking advantage of the transgenic mouse Tg(Drd1a-cre)FK164Gsat/Mmucd (Drd1a-Cre), that selectively expresses Cre-recombinase in a subpopulation of layer 6b neurons across the entire cortical mantle. At P8, 18% of layer 6b neurons are labeled with Drd1a-Cre::tdTomato in somatosensory cortex (SS), and some co-express known layer 6b markers. Using Cre-dependent viral tracing, we identified topographical projections to higher order thalamic nuclei. VGluT1+ synapses formed by labeled layer 6b projections were found in posterior thalamic nucleus (Po) but not in the (pre)thalamic reticular nucleus (TRN). The lack of TRN collaterals was confirmed with single-cell tracing from SS. Transmission electron microscopy comparison of terminal varicosities from layer 5 and layer 6b axons in Po showed that L6b varicosities are markedly smaller and simpler than the majority from L5. Our results suggest that L6b projections to the thalamus are distinct from both L5 and L6a projections.

submitter Study of Backgrounds to Black Hole Events in the ATLAS Detector

CERN Document Server

Han, Sang Hee

large extra dimension model with black hole mass MBH = sˆ, where sˆ is the parton-parton Centre of Momentum System (CMS) energy squared. In the large extra dimension model, quantum gravity can become strong at a TeV energy scale in the bulk space-time, and could lead to microscopic black holes being produced and observed by the LHC experiments. Once black holes are produced in the collider, they will decay to the SM particles by Hawking evaporation. Under this scenario, an analysis was carried out to determine the significance of black hole signals above some SM backgrounds in the ATLAS detector. Five event selection criteria were app...

Radiative properties of optical board embedded with optical black holes

International Nuclear Information System (INIS)

Qiu, J.; Liu, L.H.; Hsu, P.-F.

2011-01-01

Unique radiative properties, such as wavelength-selective transmission or absorption, have been intensively studied. Historically, geometries for wavelength-selective of light absorption were developed based on metallic periodical structures, which were only applied in the case of TM wave incidence due to the excitation of surface plasmons. In this paper, we develop an alternative approach to selective wavelength of light absorption (both TE and TM waves), based on an optical board periodical embedded with optical black holes. Numerical work was carried out to study such structure's radiative properties within the wavelength range of 1-100 μm. The electromagnetic wave transmission through such a structure is predicted by solving Maxwell's equations using the finite-difference time-domain (FDTD) method. Spectral absorptance varies with the period of optical black holes. When the incidence wavelength is much larger than the inner core radius, most of the light energy will be transmitted through the inner core. Otherwise, the energy will be mainly absorbed. Numerical results of the radiative properties of the optical board with different incidence wavelengths are also obtained. The effect of the oblique incidence wave is investigated. This study helps us gain a better understanding of the radiative properties of an optical board embedded with optical black holes and develop an alternative approach to selective light absorption.

White OLED using β-diketones rare earth binuclear complex as emitting layer

International Nuclear Information System (INIS)

Quirino, W.G.; Legnani, C.; Cremona, M.; Lima, P.P.; Junior, S.A.; Malta, O.L.

2006-01-01

In this work, the fabrication and the characterization of a white triple-layer OLED using a β-diketones binuclear complex [Eu(btfa) 3 phenterpyTb(acac) 3 ] as the emitting layer is reported. The devices were assembled using a heterojunction between three organic molecular materials: the N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB) as hole-transporting layer, the β-diketones binuclear complex and the tris(8-hydroxyquinoline aluminum) (Alq 3 ) as the electron transporting layer. All the organic layers were sequentially deposited under high vacuum environment by thermal evaporation onto ITO substrates and without breaking vacuum. Continuous electroluminescence emission was obtained varying the applied bias voltage from 10 to 22 V showing a wide emission band from 400 to 700 nm with about 100 cd/m 2 of luminance. The white emission results from a combined action between the binuclear complex, acting as hole blocking and emitting layer, blue from NPB and the typical Alq 3 green emission. The intensity ratio of the peaks is determined by the layer thickness and by the bias voltage applied to the OLED, allowing us to obtain a color tunable light source

The theory of double layers

International Nuclear Information System (INIS)

Schamel, H.

1982-01-01

Numerical and in some degree laboratory experiments suggest the existence of at least two different kinds of time-independent double layers: a strictly monotonic transition of the electrostatic potential and a transition accompanied by a negative spike at the low potential side (ion acoustic DL). An interpretation of both is presented in terms of analytic BGK modes. The first class of DLs commonly observed in voltage- or beam-driven plasmas needs for its existence beam-type distributions satisfying a Bohm criterion. The potential drop is at least of the order of Tsub(e), and stability arguments favour currents which satisfy the Langmuir condition. The second class found in current-driven plasma simulations is correlated with ion holes. This latter kind of nonlinear wave-solutions is linearly based on the slow ion-acoustic mode and exists due to a vortex-like distortion of the ion distribution in the thermal range. During the growth of an ion hole which is triggered by ion-acoustic fluctuations, the partial reflection of streaming electrons causes different plasma states on both sides of the potential dip and makes the ion hole asymmetric giving rise to an effective potential drop. This implies that the amplitude of this second type of double layers has an upper limit of 1-2 Tsub(e) and presumes a temperature ratio of Tsub(e)/Tsub(i) > or approximately 3 in coincidence with the numerical results. (Auth.)

Hole dephasing caused by hole-hole interaction in a multilayered black phosphorus.

Science.gov (United States)

Li, Lijun; Khan, Muhammad Atif; Lee, Yoontae; Lee, Inyeal; Yun, Sun Jin; Youn, Doo-Hyeb; Kim, Gil-Ho

2017-11-01

We study the magnetotransport of holes in a multilayered black phosphorus in a temperature range of 1.9 to 21.5 K. We observed a negative magnetoresistance at magnetic fields up to 1.5 T. This negative magetoresistance was analyzed by weak localization theory in diffusive regime. At the lowest temperature and the highest carrier density we found a phase coherence length of 48 nm. The linear temperature dependence of the dephasing rate shows that the hole-hole scattering processes with small energy transfer are the dominant contribution in breaking the carrier phase coherence.

Research of selection seeds drying in dense layer

Directory of Open Access Journals (Sweden)

S. A. Pavlov

2018-01-01

Full Text Available At the choice of the mode of safe drying of grain mass it is necessary to consider its heterogeneity on moisture content. It is an undesirable factor of which it is necessary to get rid. When increase in moisture inconstant the stability of grain mass at storage decreases, there is a danger of emergence of heating, the overall performance of dryers and other processing equipment decreases, energy costs for seeds production rise. To eliminate this shortcoming located in a grain layer or grain stream the dried-up product should be mixed carefully for the best uniformity. However not uniformity on individual moisture content of separate grains will remain. For its decrease combination of lying with material concitation is used. Researches were conducted in batch-operated laboratory machine. The humidified seeds of sugar beet were blowed-through with the drying agent speed of 0.5 m/s and temperature of 45 degrees Celsius. Moisture removal between concitations did not exceed 2.5 percent for selection seeds and 3.0 percent for ordinary ones. Duration of the periods between concitations can be determined in the analytical way. Thickness of a layer of seeds allowing drying without concitation decreases on square dependence on increase in moisture content. A contact moisture exchange between the damp and dried caryopsides for 30 min and more make it possibledrop-off in the unevenness of drying up to 0.5 percent.

The depletion of the stratospheric ozone layer

International Nuclear Information System (INIS)

Sabogal Nelson

2000-01-01

The protection of the Earth's ozone layer is of the highest importance to mankind. The dangers of its destruction are by now well known. The depletion of that layer has reached record levels. The Antarctic ozone hole covered this year a record area. The ozone layer is predicted to begin recovery in the next one or two decades and should be restored to pre-1980 levels by 2050. This is the achievement of the regime established by the 1985 Vienna Convention for the Protection of the Ozone Layer and the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer. The regime established by these two agreements has been revised, and made more effective in London (1990), Copenhagen (1992), Vienna (1995), and Beijing (1999)

Eliminating dependence of hole depth on aspect ratio by forming ammonium bromide during plasma etching of deep holes in silicon nitride and silicon dioxide

Science.gov (United States)

Iwase, Taku; Yokogawa, Kenetsu; Mori, Masahito

2018-06-01

The reaction mechanism during etching to fabricate deep holes in SiN/SiO2 stacks by using a HBr/N2/fluorocarbon-based gas plasma was investigated. To etch SiN and SiO2 films simultaneously, HBr/fluorocarbon gas mixture ratio was controlled to achieve etching selectivity closest to one. Deep holes were formed in the SiN/SiO2 stacks by one-step etching at several temperatures. The surface composition of the cross section of the holes was analyzed by time-of-flight secondary-ion mass spectrometry. It was found that bromine ions (considered to be derived from NH4Br) were detected throughout the holes in the case of low-temperature etching. It was also found that the dependence of hole depth on aspect ratio decreases as temperature decreases, and it becomes significantly weaker at a substrate temperature of 20 °C. It is therefore concluded that the formation of NH4Br supplies the SiN/SiO2 etchant to the bottom of the holes. Such a finding will make it possible to alleviate the decrease in etching rate due to a high aspect ratio.

Surface-geophysical techniques used to detect existing and infilled scour holes near bridge piers

Science.gov (United States)

Placzek, Gary; Haeni, F.P.

1995-01-01

Surface-geophysical techniques were used with a position-recording system to study riverbed scour near bridge piers. From May 1989 to May 1993. Fathometers, fixed- and swept-frequency con- tinuous seismic-reflection profiling (CSP) systems, and a ground-penetrating radar (GPR) system were used with a laser-positioning system to measure the depth and extent of existing and infilled scour holes near bridge piers. Equipment was purchased commercially and modified when necessary to interface the components and (or) to improve their performance. Three 200-kHz black-and-white chart- recording Fathometers produced profiles of the riverbed that included existing scour holes and exposed pier footings. The Fathometers were used in conjunction with other geophysical techniques to help interpret the geophysical data. A 20-kHz color Fathometer delineated scour-hole geometry and, in some cases, the thickness of fill material in the hole. The signal provided subbottom information as deep as 10 ft in fine-grained materials and resolved layers of fill material as thin as 1 foot thick. Fixed-frequency and swept-frequency CSP systems were evaluated. The fixed-frequency system used a 3.5-, 7.0-, or 14-kHz signal. The 3.5-kHz signal pene- trated up to 50 ft of fine-grained material and resolved layers as thin as 2.5-ft thick. The 14-kHz signal penetrated up to 20 ft of fine-grained material and resolved layers as thin as 1-ft thick. The swept-frequency systems used a signal that swept from 2- to 16-kHz. With this system, up to 50 ft of penetration was achieved, and fill material as thin as 1 ft was resolved. Scour-hole geometry, exposed pier footings, and fill thickness in scour holes were detected with both CSP systems. The GPR system used an 80-, 100-, or 300-megahertz signal. The technique produced records in water up to 15 ft deep that had a specific conductance less than 200x11ms/cm. The 100-MHz signal penetrated up to 40 ft of resistive granular material and resolved layers as

Monitoring macular pigment changes in macular holes using fluorescence lifetime imaging ophthalmoscopy.

Science.gov (United States)

Sauer, Lydia; Peters, Sven; Schmidt, Johanna; Schweitzer, Dietrich; Klemm, Matthias; Ramm, Lisa; Augsten, Regine; Hammer, Martin

2017-08-01

To investigate the impact of macular pigment (MP) on fundus autofluorescence (FAF) lifetimes in vivo by characterizing full-thickness idiopathic macular holes (MH) and macular pseudo-holes (MPH). A total of 37 patients with MH and 52 with MPH were included. Using the fluorescence lifetime imaging ophthalmoscope (FLIO), based on a Heidelberg Engineering Spectralis system, a 30° retinal field was investigated. FAF decays were detected in a short (498-560 nm; ch1) and long (560-720 nm; ch2) wavelength channel. τ m , the mean fluorescence lifetime, was calculated from a three-exponential approximation of the FAF decays. Macular coherence tomography scans were recorded, and macular pigment's optical density (MPOD) was measured (one-wavelength reflectometry). Two MH subgroups were analysed according to the presence or absence of an operculum above the MH. A total of 17 healthy fellow eyes were included. A longitudinal FAF decay examination was conducted in nine patients, which were followed up after surgery and showed a closed MH. In MH without opercula, significant τ m differences (p hole area (MHa) and surrounding areas (MHb) (ch1: MHa 238 ± 64 ps, MHb 181 ± 78 ps; ch2: MHa 275 ± 49 ps, MHb 223 ± 48 ps), as well as between MHa and healthy eyes or closed MH. Shorter τ m , adjacent to the hole, can be assigned to areas with equivalently higher MPOD. Opercula containing MP also show short τ m . In MPH, the intactness of the Hele fibre layer is associated with shortest τ m . Shortest τ m originates from MP-containing retinal layers, especially from the Henle fibre layer. Fluorescence lifetime imaging ophthalmoscope (FLIO) provides information on the MP distribution, the pathogenesis and topology of MH. Macular pigment (MP) fluorescence may provide a biomarker for monitoring pathological changes in retinal diseases. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Effect of light-hole tunnelling on the excitonic properties of GaAsP/AlGaAs near-surface quantum wells

International Nuclear Information System (INIS)

Pal, Suparna; Porwal, S; Sharma, T K; Oak, S M; Singh, S D; Khan, S; Jayabalan, J; Chari, Rama

2013-01-01

Light-hole tunnelling to the surface states is studied using photoluminescence (PL) spectroscopy and transient reflectivity measurements in the tensile-strained GaAsP/AlGaAs near-surface quantum well (NSQW) samples by reducing the top barrier layer thickness from 275 to 5 nm. The ground state transition (e 1 –lh 1 ) remains excitonic even at room temperature (RT) for a buried quantum well sample with 275 nm thick top barrier. When the top barrier thickness is reduced to 50 nm the same transition is found to be excitonic only at low temperatures but changes to free-carrier recombination at higher temperatures. When the top barrier layer thickness is further reduced to 5 nm, the ground state transition is no longer excitonic in nature, where it shows free-carrier behaviour even at 10 K. We therefore find a clear relationship between the character of the ground state transition and the top barrier layer thickness. Light-hole excitons cannot be formed in NSQW samples when the top barrier layer thickness is kept reasonably low. This is attributed to the quantum mechanical tunnelling of free light holes to the surface states, which is found to be faster than the exciton formation process. A tunnelling time of ∼500 fs for light holes is measured by the transient reflectivity measurements for the NSQW sample with a 5 nm top barrier. On the other hand, heavy-hole-related transitions in NSQW samples are found to be of excitonic nature even at RT because of the relatively large tunnelling time. It supports the dominance of excited state feature over the ground state transition in PL measurements at temperatures higher than 150 K. (paper)

Formation of 2D-PhCs with missing holes based on Si-layers by EBL

Science.gov (United States)

Utkin, D. E.; Shklyev, A. A.; Tsarev, A. V.; Latyshev, A. V.

2017-11-01

The fabrication of the periodic structures, that is two-dimensional photonic crystals (2D PhCs) based on Si-materials by electron beam lithography (EBL) technique has been studied. We have investigated basic lithography processes such as designing, exposition, development, etching and others. The developed top-down approach allows close-packed arrays of elements and holes to be formed in nanometre range. This can be used to produce 2D PhCs with emitting micro-cavities (missing holes) with lateral size parameters with an accuracy of about 2% in the Si (100) substrate and in silicon-on-insulator structures. Such accuracy is expected to be sufficient for obtaining the cavities-coupling radiation interference from large areas of 2D PhCs.

Effect of tunneling layers on the performances of floating-gate based organic thin-film transistor nonvolatile memories

Science.gov (United States)

Wang, Wei; Han, Jinhua; Ying, Jun; Xiang, Lanyi; Xie, Wenfa

2014-09-01

Two types of floating-gate based organic thin-film transistor nonvolatile memories (FG-OTFT-NVMs) were demonstrated, with poly(methyl methacrylate co glycidyl methacrylate) (P(MMA-GMA)) and tetratetracontane (TTC) as the tunneling layer, respectively. Their device performances were measured and compared. In the memory with a P(MMA-GMA) tunneling layer, typical unipolar hole transport was obtained with a relatively small mobility of 0.16 cm2/V s. The unidirectional shift of turn-on voltage (Von) due to only holes trapped/detrapped in/from the floating gate resulted in a small memory window of 12.5 V at programming/erasing voltages (VP/VE) of ±100 V and a nonzero reading voltage. Benefited from the well-ordered molecule orientation and the trap-free surface of TTC layer, a considerably high hole mobility of 1.7 cm2/V s and a visible feature of electrons accumulated in channel and trapped in floating-gate were achieved in the memory with a TTC tunneling layer. High hole mobility resulted in a high on current and a large memory on/off ratio of 600 at the VP/VE of ±100 V. Both holes and electrons were injected into floating-gate and overwritten each other, which resulted in a bidirectional Von shift. As a result, an enlarged memory window of 28.6 V at the VP/VE of ±100 V and a zero reading voltage were achieved. Based on our results, a strategy is proposed to optimize FG-OTFT-NVMs by choosing a right tunneling layer to improve the majority carrier mobility and realize ambipolar carriers injecting and trapping in the floating-gate.

Selective laser etching or ablation for fabrication of devices

KAUST Repository

Buttner, Ulrich

2017-01-12

Methods of fabricating devices vial selective laser etching are provided. The methods can include selective laser etching of a portion of a metal layer, e.g. using a laser light source having a wavelength of 1,000 nm to 1,500 nm. The methods can be used to fabricate a variety of features, including an electrode, an interconnect, a channel, a reservoir, a contact hole, a trench, a pad, or a combination thereof. A variety of devices fabricated according to the methods are also provided. In some aspects, capacitive humidity sensors are provided that can be fabricated according to the provided methods. The capacitive humidity sensors can be fabricated with intricate electrodes, e.g. having a fractal pattern such as a Peano curve, a Hilbert curve, a Moore curve, or a combination thereof.

Black hole microstates in AdS{sub 4} from supersymmetric localization

Energy Technology Data Exchange (ETDEWEB)

Benini, Francesco [Blackett Laboratory, Imperial College London,South Kensington Campus, London SW7 2AZ (United Kingdom); International School for Advanced Studies (SISSA),via Bonomea 265, 34136 Trieste (Italy); Hristov, Kiril [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences,Tsarigradsko Chaussee 72, 1784 Sofia (Bulgaria); Zaffaroni, Alberto [Dipartimento di Fisica, Università di Milano-Bicocca,piazza della Scienza 3, I-20126 Milano (Italy); INFN, sezione di Milano-Bicocca,piazza della Scienza 3, I-20126 Milano (Italy)

2016-05-10

This paper addresses a long standing problem, the counting of the microstates of supersymmetric asymptotically AdS black holes in terms of a holographically dual field theory. We focus on a class of asymptotically AdS{sub 4} static black holes preserving two real supercharges which are dual to a topologically twisted deformation of the ABJM theory. We evaluate in the large N limit the topologically twisted index of the ABJM theory and we show that it correctly reproduces the entropy of the AdS{sub 4} black holes. An extremization of the index with respect to a set of chemical potentials is required. We interpret it as the selection of the exact R-symmetry of the superconformal quantum mechanics describing the horizon of the black hole.

Performance of High Layer Thickness in Selective Laser Melting of Ti6Al4V

Directory of Open Access Journals (Sweden)

Xuezhi Shi

2016-12-01

Full Text Available To increase building rate and save cost, the selective laser melting (SLM of Ti6Al4V with a high layer thickness (200 μm and low cost coarse powders (53 μm–106 μm at a laser power of 400 W is investigated in this preliminary study. A relatively large laser beam with a diameter of 200 μm is utilized to produce a stable melt pool at high layer thickness, and the appropriate scanning track, which has a smooth surface with a shallow contact angle, can be obtained at the scanning speeds from 40 mm/s to 80 mm/s. By adjusting the hatch spacings, the density of multi-layer samples can be up to 99.99%, which is much higher than that achieved in previous studies about high layer thickness selective laser melting. Meanwhile, the building rate can be up to 7.2 mm3/s, which is about 2 times–9 times that of the commercial equipment. Besides, two kinds of defects are observed: the large un-melted defects and the small spherical micropores. The formation of the un-melted defects is mainly attributed to the inappropriate overlap rates and the unstable scanning tracks, which can be eliminated by adjusting the processing parameters. Nevertheless, the micropores cannot be completely eliminated. It is worth noting that the high layer thickness plays a key role on surface roughness rather than tensile properties during the SLM process. Although a sample with a relatively coarse surface is generated, the average values of yield strength, ultimate tensile strength, and elongation are 1050 MPa, 1140 MPa, and 7.03%, respectively, which are not obviously different than those with the thin layer thickness used in previous research; this is due to the similar metallurgical bonding and microstructure.

Performance of High Layer Thickness in Selective Laser Melting of Ti6Al4V.

Science.gov (United States)

Shi, Xuezhi; Ma, Shuyuan; Liu, Changmeng; Chen, Cheng; Wu, Qianru; Chen, Xianping; Lu, Jiping

2016-12-01

To increase building rate and save cost, the selective laser melting (SLM) of Ti6Al4V with a high layer thickness (200 μm) and low cost coarse powders (53 μm-106 μm) at a laser power of 400 W is investigated in this preliminary study. A relatively large laser beam with a diameter of 200 μm is utilized to produce a stable melt pool at high layer thickness, and the appropriate scanning track, which has a smooth surface with a shallow contact angle, can be obtained at the scanning speeds from 40 mm/s to 80 mm/s. By adjusting the hatch spacings, the density of multi-layer samples can be up to 99.99%, which is much higher than that achieved in previous studies about high layer thickness selective laser melting. Meanwhile, the building rate can be up to 7.2 mm³/s, which is about 2 times-9 times that of the commercial equipment. Besides, two kinds of defects are observed: the large un-melted defects and the small spherical micropores. The formation of the un-melted defects is mainly attributed to the inappropriate overlap rates and the unstable scanning tracks, which can be eliminated by adjusting the processing parameters. Nevertheless, the micropores cannot be completely eliminated. It is worth noting that the high layer thickness plays a key role on surface roughness rather than tensile properties during the SLM process. Although a sample with a relatively coarse surface is generated, the average values of yield strength, ultimate tensile strength, and elongation are 1050 MPa, 1140 MPa, and 7.03%, respectively, which are not obviously different than those with the thin layer thickness used in previous research; this is due to the similar metallurgical bonding and microstructure.

A gas production system from methane hydrate layers by hot water injection and BHP control with radial horizontal wells

Energy Technology Data Exchange (ETDEWEB)

Yamakawa, T.; Ono, S.; Iwamoto, A.; Sugai, Y.; Sasaki, K. [Kyushu Univ., Fukuoka, Fukuoka (Japan)

2010-07-01

Reservoir characterization of methane hydrate (MH) bearing turbidite channel in the eastern Nankai Trough, in Japan has been performed to develop a gas production strategy. This paper proposed a gas production system from methane hydrate (MH) sediment layers by combining the hot water injection method and bottom hole pressure control at the production well using radial horizontal wells. Numerical simulations of the cylindrical homogeneous MH layer model were performed in order to evaluate gas production characteristics by the depressurization method with bottom hole pressure control. In addition, the effects of numerical block modeling and averaging physical properties of MH layers were presented. According to numerical simulations, combining the existing production system with hot water injection and bottom hole pressure control results in an outward expansion of the hot water chamber from the center of the MH layer with continuous gas production. 10 refs., 15 figs.

Improved thermal stability and hole mobilities in a strained-Si/strained-Si1-yGe y/strained-Si heterostructure grown on a relaxed Si1-xGe x buffer

International Nuclear Information System (INIS)

Gupta, Saurabh; Lee, Minjoo L.; Isaacson, David M.; Fitzgerald, Eugene A.

2005-01-01

A dual channel heterostructure consisting of strained-Si/strained-Si 1-y Ge y on relaxed Si 1-x Ge x (y > x), provides a platform for fabricating metal-oxide-semiconductor field-effect transistors (MOSFETs) with high hole mobilities (μ eff ) which depend directly on Ge concentration and strain in the strained-Si 1-y Ge y layer. Ge out-diffuses from the strained-Si 1-y Ge y layer into relaxed Si 1-x Ge x during high temperature processing, reducing peak Ge concentration and strain in the strained-Si 1-y Ge y layer and degrades hole μ eff in these dual channel heterostructures. A heterostructure consisting of strained-Si/strained-Si 1-y Ge y /strained-Si, referred to as a trilayer heterostructure, grown on relaxed Si 1-x Ge x has much reduced Ge out-flux from the strained-Si 1-y Ge y layer and retains higher μ eff after thermal processing. Improved hole μ eff over similar dual channel heterostructures is also observed in this heterostructure. This could be a result of preventing the hole wavefunction tunneling into the low μ eff relaxed Si 1-x Ge x layer due to the additional valence band offset provided by the underlying strained-Si layer. A diffusion coefficient has been formulated and implemented in a finite difference scheme for predicting the thermal budget of the strained SiGe heterostructures. It shows that the trilayer heterostructures have superior thermal budgets at higher Ge concentrations. Ring-shaped MOSFETs were fabricated on both platforms and subjected to various processing temperatures in order to compare the extent of μ eff reduction with thermal budget. Hole μ eff enhancements are retained to a much higher extent in a trilayer heterostructure after high temperature processing as compared to a dual channel heterostructure. The improved thermal stability and hole μ eff of a trilayer heterostructure makes it an ideal platform for fabricating high μ eff MOSFETs that can be processed over higher temperatures without significant losses in hole �

Graphene oxide/PEDOT:PSS composite hole transport layer for efficient and stable planar heterojunction perovskite solar cells.

Science.gov (United States)

Lee, Da-Young; Na, Seok-In; Kim, Seok-Soon

2016-01-21

We investigated a graphene oxide (GO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ( PSS) composite as a promising candidate for the practical application of a 2-D carbonaceous hole transport layer (HTL) to planar heterojunction perovskite solar cells (PeSCs) consisting of a transparent electrode/HTL/perovskite/fullerene/metal electrode. Both the insulating properties of GO and the non-uniform coating of the transparent electrode with GO cause the poor morphology of perovskite induced low power conversion efficiency (PCE) of 6.4%. On the other hand, PeSCs with a GO/PEDOT:PSS composite HTL, exhibited a higher PCE of 9.7% than that of a device fabricated with conventional PSS showing a PCE of 8.2%. The higher performance is attributed to the decreased series resistance (RS) and increased shunt resistance (RSh). The well-matched work-function between GO (4.9 eV) and PSS (5.1 eV) probably results in more efficient charge transport and an overall decrease in RS. The existence of GO with a large bandgap of ∼3.6 eV might induce the effective blocking of electrons, leading to an increase of RSh. Moreover, improvement in the long-term stability under atmospheric conditions was observed.

High strain amount in recessed junctions induced by selectively deposited boron-doped SiGe layers

International Nuclear Information System (INIS)

Radamson, H.H.; Kolahdouz, M.; Ghandi, R.; Ostling, M.

2008-01-01

This work presents the selective epitaxial growth (SEG) of Si 1-x Ge x (x = 0.15-0.315) layers with high amount of boron (1 x 10 20 -1 x 10 21 cm -3 ) in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. The influence of the growth rate and strain on boron incorporation has been studied. A focus has been made on the strain distribution and boron incorporation in SEG of SiGe layers

DC-sputtered MoO{sub x} thin-films as hole transport layer in organic photovoltaic

Energy Technology Data Exchange (ETDEWEB)

Cauduro, Andre L.F.; Ahmadpour, Mehrad; Rubahn, Horst-Guenter; Madsen, Morten, E-mail: cauduro@mci.sdu.dk [NanoSYD, University of Southern Denmark (Denmark); Reis, Roberto dos; Chen, Gong; Schmid, Andreas [National Center for Electron Microscopy, The Molecular Foundry, LBNL, Berkeley, CA (United States); Methivier, Christophe [Sorbonne Universites, UPMC Univ Paris 06, CNRS UMR, Laboratoire de Reactivite de Surface (LRS) (France); Witkowski, Nadine [Sorbonne Universites, UPMC Univ Paris 06, UMR CNRS, Institut des Nanosciences de Paris (INSP) (France); Fichtner, Paulo F.P. [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre (Brazil)

2016-07-01

Full text: Molybdenum-oxide (MoO{sub x}) thin-films have attracted a lot of attention in the past years due to their unique ability to act as interfacial layers in novel electronics and energy applications. In the work presented here, large tuning possibilities in the electronic and optoelectronic properties of MoO{sub x} thin-films deposited by reactive sputtering using different oxygen partial pressures and annealing conditions are demonstrated along with the implementation of the films in organic photovoltaic. MoO{sub x} thin-films deposited under low oxygen partial pressure present a high conductivity of around 3.22 S.cm{sup -1}, however, as the oxygen partial pressure increases, the conductivity of the resulting films drops by up to around 10 orders of magnitude as the [O]/[Mo] ratio changes from 2.57 to beyond 3.00. Optical absorption measurements also show drastic changes mostly within the 0.60 eV - 2.50 eV spectral region for the same increase in oxygen concentration in [1]. UPS and XPS studies are conducted for accessing information about the work function and surface composition of the thin-films. The XPS spectra registered on the Mo 3d core level reveal how the oxidation state of Mo is affected by the partial pressure of oxygen during film growth. The work function of the films increase with annealing temperature and oxygen content, and span a tuning range of about 2 eV. To extract the spatially resolved work function values from the sputtered films, we use in addition Low Energy Electron Microscopy (LEEM). Finally, the application of the MoO{sub x} thin-films in organic optoelectronic devices is investigated by employing them as hole transport layers in small molecule photovoltaic, here based on DBP and C70. The work thus demonstrates a viable method for tuning the electronic and optoelectronic properties of MoO{sub x} thin-films, which can be applied in combination with a wide range of materials in e.g. organic photovoltaic. [1] A.L. Fernandes Cauduro

Black Holes

OpenAIRE

Horowitz, Gary T.; Teukolsky, Saul A.

1998-01-01

Black holes are among the most intriguing objects in modern physics. Their influence ranges from powering quasars and other active galactic nuclei, to providing key insights into quantum gravity. We review the observational evidence for black holes, and briefly discuss some of their properties. We also describe some recent developments involving cosmic censorship and the statistical origin of black hole entropy.

CLOSING MACULAR HOLES WITH "MACULAR PLUG" WITHOUT GAS TAMPONADE AND POSTOPERATIVE POSTURING.

Science.gov (United States)

Chakrabarti, Meena; Benjamin, Preethi; Chakrabarti, Keya; Chakrabarti, Arup

2017-03-01

To investigate the surgical results of macular hole surgery without gas tamponade or postoperative posturing in patients with Stage 3 and Stage 4 macular holes with ≥500 μm mean base diameter. Retrospective interventional case series. Twenty-six patients with Stage 3 and Stage 4 macular holes. Twenty-six eyes of 26 patients with Stage 3 and Stage 4 macular holes and a mean base diameter of 892.8 ± 349 μm underwent pars plana 23-gauge vitrectomy with broad internal limiting membrane peel (ILM peel), inverted ILM flap repositioning (ILMR), and use of autologous gluconated blood clumps as a macular plug to close the macular hole. No fluid-air exchange, endotamponade, or postoperative posturing was used. The subjects were followed up for 12 months. The anatomical outcome of the procedure was evaluated by fundus examination and optical coherence tomography. Spectral domain optical coherence tomography was used to study the restoration of the outer retinal layer integrity in the postoperative period. The preoperative and postoperative best-corrected visual acuities in logMAR units were compared to evaluate functional outcome. Macular hole closure and best-corrected visual acuity before and after surgery. Twenty-six patients with mean age 62.8 ± 7.3 years, preoperative median best-corrected visual acuity 6/60 (1.0 logMAR units), and a mean base diameter of 892.8 ± 349 μm underwent surgery to close macular holes without gas tamponade or postoperative posturing. Twenty patients (76.9%) were phakic. Twenty eyes (76.92%) had Stage 3 macular holes and 6 eyes (23.10%) had Stage 4 macular holes. After a single surgery, hole closure was achieved in 100% of eyes. The median best-corrected visual acuity improved from 6/60 (1.0 logMAR units) to 6/18 (0.50 logMAR units) (P hole closure with statically significant functional improvement for large Stage 3 and Stage 4 macular holes.

Fatigue crack growth monitoring in multi-layered structures using guided ultrasonic waves

International Nuclear Information System (INIS)

Kostson, E; Fromme, P

2009-01-01

This contribution investigates the application of low frequency guided ultrasonic waves for monitoring fatigue crack growth at fastener holes in the 2nd layer of multi-layered plate structures, a common problem in aerospace industry. The model multi-layered structure investigated consists of two aluminum plate-strips adhesively bonded using a structural paste adhesive. Guided ultrasonic waves were excited using multiple piezoelectric discs bonded to the surface of the multi-layered structure. The wave propagation in the tensile specimen was measured using a laser interferometer and compared to numerical simulations. Thickness and width mode shapes of the excited flexural waves were identified from Semi-Analytical Finite Element (SAFE) calculations. Experiments and 3D Finite Element (FE) simulations show a change in the scattered field around fastener holes caused by a defect in the 2nd layer. The amplitude of the guided ultrasonic wave was monitored during fatigue experiments at a single point. The measured changes in the amplitude of the ultrasonic signal due to fatigue crack growth agree well with FE simulations.

Black hole levitron

International Nuclear Information System (INIS)

Arsiwalla, Xerxes D.; Verlinde, Erik P.

2010-01-01

We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.'s multicenter supersymmetric black hole solutions provides a supergravity description of such backgrounds within which a black hole can be trapped within a confined volume. This construction is realized by solving for a levitating black hole over a magnetic dipole base. We comment on how such a construction is akin to a mechanical levitron.

Layered plasma polymer composite membranes

Science.gov (United States)

Babcock, Walter C.

1994-01-01

Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is .gtoreq.2 and is the number of selective layers.

Noncommutative black holes

Energy Technology Data Exchange (ETDEWEB)

Lopez-DomInguez, J C [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); Obregon, O [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); RamIrez, C [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Puebla, PO Box 1364, 72000 Puebla (Mexico); Sabido, M [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico)

2007-11-15

We study noncommutative black holes, by using a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate Hawking's temperature and entropy for the 'noncommutative' Schwarzschild black hole.

Selective growth of Ge1- x Sn x epitaxial layer on patterned SiO2/Si substrate by metal-organic chemical vapor deposition

Science.gov (United States)

Takeuchi, Wakana; Washizu, Tomoya; Ike, Shinichi; Nakatsuka, Osamu; Zaima, Shigeaki

2018-01-01

We have investigated the selective growth of a Ge1- x Sn x epitaxial layer on a line/space-patterned SiO2/Si substrate by metal-organic chemical vapor deposition. We examined the behavior of a Sn precursor of tributyl(vinyl)tin (TBVSn) during the growth on Si and SiO2 substrates and investigated the effect of the Sn precursor on the selective growth. The selective growth of the Ge1- x Sn x epitaxial layer was performed under various total pressures and growth temperatures of 300 and 350 °C. The selective growth of the Ge1- x Sn x epitaxial layer on the patterned Si region is achieved at a low total pressure without Ge1- x Sn x growth on the SiO2 region. In addition, we found that the Sn content in the Ge1- x Sn x epitaxial layer increases with width of the SiO2 region for a fixed Si width even with low total pressure. To control the Sn content in the selective growth of the Ge1- x Sn x epitaxial layer, it is important to suppress the decomposition and migration of Sn and Ge precursors.

Charge-carrier selective electrodes for organic bulk heterojunction solar cell by contact-printed siloxane oligomers

International Nuclear Information System (INIS)

Hwang, Hyun-Sik; Khang, Dahl-Young

2015-01-01

‘Smart’ (or selective) electrode for charge carriers, both electrons and holes, in organic bulk-heterojunction (BHJ) solar cells using insertion layers made of hydrophobically-recovered and contact-printed siloxane oligomers between electrodes and active material has been demonstrated. The siloxane oligomer insertion layer has been formed at a given interface simply by conformally-contacting a cured slab of polydimethylsiloxane stamp for less than 100 s. All the devices, either siloxane oligomer printed at one interface only or printed at both interfaces, showed efficiency enhancement when compared to non-printed ones. The possible mechanism that is responsible for the observed efficiency enhancement has been discussed based on the point of optimum symmetry and photocurrent analysis. Besides its simplicity and large-area applicability, the demonstrated contact-printing technique does not involve any vacuum or wet processing steps and thus can be very useful for the roll-based, continuous production scheme for organic BHJ solar cells. - Highlights: • Carrier-selective insertion layer in organic bulk heterojunction solar cells • Simple contact-printing of siloxane oligomers improves cell efficiency. • Printed siloxane layer reduces carrier recombination at electrode surfaces. • Siloxane insertion layer works equally well at both electrode surfaces. • Patterned PDMS stamp shortens the printing time within 100 s

Black hole critical phenomena without black holes

Indian Academy of Sciences (India)

large values of Ф, black holes do form and for small values the scalar field ... on the near side of the ridge ultimately evolve to form black holes while those configu- ... The inset shows a bird's eye view looking down on the saddle point.

Search for black holes

International Nuclear Information System (INIS)

Cherepashchuk, Anatolii M

2003-01-01

Methods and results of searching for stellar mass black holes in binary systems and for supermassive black holes in galactic nuclei of different types are described. As of now (June 2002), a total of 100 black hole candidates are known. All the necessary conditions Einstein's General Relativity imposes on the observational properties of black holes are satisfied for candidate objects available, thus further assuring the existence of black holes in the Universe. Prospects for obtaining sufficient criteria for reliably distinguishing candidate black holes from real black holes are discussed. (reviews of topical problems)

Development of scour in non-cohesive sediments under a poorly erodible top layer

OpenAIRE

Van Zuylen, J.A.; Sloff, C.J.

2015-01-01

This study deals with the development of deep scour holes in the river bed of the Dutch Rhine delta in the Netherlands. Assessment of multi-beam surveys, laboratory-flume experiments, and 3D numerical modelling, shows how fast this type of scour holes grows in depth and width. These typical scour holes are found in the tidal deltaic rivers that experience a general incision. This erosion decreases the thickness of the erosion resistant clay/peat layer that is covering and protecting the under...

Arrangement of disposal holes according to the features of groundwater flow

Energy Technology Data Exchange (ETDEWEB)

Ko, Nak Youl; Baik, Min Hoon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-12-15

Based on the results of groundwater flow system modeling for a hypothetical deep geological repository site, quantitative and spatial distributions of groundwater flow rates at the positions of deposition holes, groundwater travel length and time from the positions to the surface environment were analyzed and used to suggest a method for determining locations of deposition holes. The hydraulic head values at the depth of the deposition holes and a particle tracking method were used to calculate the groundwater flow rates and groundwater travel length and time, respectively. From the results, an approach to designing a layout of deposition holes was suggested by selecting relatively favorable positions for maintaining performance of the disposal facility and screening some positions of deposition holes that did not comply with specific constraints for the groundwater flow rates, travel length and time. In addition, a method for determining a geometrical direction for extension of the disposal facility was discussed. Designing the layout of deposition holes with the information of groundwater flow at the disposal depth can contribute to secure performance and safety of the disposal facility.

Electron holes in phase space: What they are and why they matter

Science.gov (United States)

Hutchinson, I. H.

2017-05-01

This is a tutorial and selective review explaining the fundamental concepts and some currently open questions concerning the plasma phenomenon of the electron hole. The widespread occurrence of electron holes in numerical simulations, space-craft observations, and laboratory experiments is illustrated. The elementary underlying theory is developed of a one-dimensional electron hole as a localized potential maximum, self-consistently sustained by a deficit of trapped electron phase-space density. The spatial extent of a hole is typically a few Debye lengths; what determines the minimum and maximum possible lengths is explained, addressing the key aspects of the as yet unsettled dispute between the integral and differential approaches to hole structure. In multiple dimensions, holes tend to form less readily; they generally require a magnetic field and distribution-function anisotropy. The mechanisms by which they break up are explained, noting that this transverse instability is not fully understood. Examples are given of plasma circumstances where holes play an important role, and of recent progress on understanding their holistic kinematics and self-acceleration.

Selective deposition contact patterning using atomic layer deposition for the fabrication of crystalline silicon solar cells

International Nuclear Information System (INIS)

Cho, Young Joon; Shin, Woong-Chul; Chang, Hyo Sik

2014-01-01

Selective deposition contact (SDC) patterning was applied to fabricate the rear side passivation of crystalline silicon (Si) solar cells. By this method, using screen printing for contact patterning and atomic layer deposition for the passivation of Si solar cells with Al 2 O 3 , we produced local contacts without photolithography or any laser-based processes. Passivated emitter and rear-contact solar cells passivated with ozone-based Al 2 O 3 showed, for the SDC process, an up-to-0.7% absolute conversion-efficiency improvement. The results of this experiment indicate that the proposed method is feasible for conversion-efficiency improvement of industrial crystalline Si solar cells. - Highlights: • We propose a local contact formation process. • Local contact forms a screen print and an atomic layer deposited-Al 2 O 3 film. • Ozone-based Al 2 O 3 thin film was selectively deposited onto patterned silicon. • Selective deposition contact patterning method can increase cell-efficiency by 0.7%

Selectivity Enhancement by Using Double-Layer MOX-Based Gas Sensors Prepared by Flame Spray Pyrolysis (FSP

Directory of Open Access Journals (Sweden)

Julia Rebholz

2016-09-01

Full Text Available Here we present a novel concept for the selective recognition of different target gases with a multilayer semiconducting metal oxide (SMOX-based sensor device. Direct current (DC electrical resistance measurements were performed during exposure to CO and ethanol as single gases and mixtures of highly porous metal oxide double- and single-layer sensors obtained by flame spray pyrolysis. The results show that the calculated resistance ratios of the single- and double-layer sensors are a good indicator for the presence of specific gases in the atmosphere, and can constitute some building blocks for the development of chemical logic devices. Due to the inherent lack of selectivity of SMOX-based gas sensors, such devices could be especially relevant for domestic applications.

Differential gene expression from genome-wide microarray analyses distinguishes Lohmann Selected Leghorn and Lohmann Brown layers.

Directory of Open Access Journals (Sweden)

Christin Habig

Full Text Available The Lohmann Selected Leghorn (LSL and Lohmann Brown (LB layer lines have been selected for high egg production since more than 50 years and belong to the worldwide leading commercial layer lines. The objectives of the present study were to characterize the molecular processes that are different among these two layer lines using whole genome RNA expression profiles. The hens were kept in the newly developed small group housing system Eurovent German with two different group sizes. Differential expression was observed for 6,276 microarray probes (FDR adjusted P-value <0.05 among the two layer lines LSL and LB. A 2-fold or greater change in gene expression was identified on 151 probe sets. In LSL, 72 of the 151 probe sets were up- and 79 of them were down-regulated. Gene ontology (GO enrichment analysis accounting for biological processes evinced 18 GO-terms for the 72 probe sets with higher expression in LSL, especially those taking part in immune system processes and membrane organization. A total of 32 enriched GO-terms were determined among the 79 down-regulated probe sets of LSL. Particularly, these terms included phosphorus metabolic processes and signaling pathways. In conclusion, the phenotypic differences among the two layer lines LSL and LB are clearly reflected in their gene expression profiles of the cerebrum. These novel findings provide clues for genes involved in economically important line characteristics of commercial laying hens.

A highly sensitive hydrogen sensor with gas selectivity using a PMMA membrane-coated Pd nanoparticle/single-layer graphene hybrid.

Science.gov (United States)

Hong, Juree; Lee, Sanggeun; Seo, Jungmok; Pyo, Soonjae; Kim, Jongbaeg; Lee, Taeyoon

2015-02-18

A polymer membrane-coated palladium (Pd) nanoparticle (NP)/single-layer graphene (SLG) hybrid sensor was fabricated for highly sensitive hydrogen gas (H2) sensing with gas selectivity. Pd NPs were deposited on SLG via the galvanic displacement reaction between graphene-buffered copper (Cu) and Pd ion. During the galvanic displacement reaction, graphene was used as a buffer layer, which transports electrons from Cu for Pd to nucleate on the SLG surface. The deposited Pd NPs on the SLG surface were well-distributed with high uniformity and low defects. The Pd NP/SLG hybrid was then coated with polymer membrane layer for the selective filtration of H2. Because of the selective H2 filtration effect of the polymer membrane layer, the sensor had no responses to methane, carbon monoxide, or nitrogen dioxide gas. On the contrary, the PMMA/Pd NP/SLG hybrid sensor exhibited a good response to exposure to 2% H2: on average, 66.37% response within 1.81 min and recovery within 5.52 min. In addition, reliable and repeatable sensing behaviors were obtained when the sensor was exposed to different H2 concentrations ranging from 0.025 to 2%.

High strain amount in recessed junctions induced by selectively deposited boron-doped SiGe layers

Energy Technology Data Exchange (ETDEWEB)

Radamson, H.H. [School of Information and Communication Technology, KTH (Royal Institute of Technology) Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)], E-mail: rad@kth.se; Kolahdouz, M.; Ghandi, R.; Ostling, M. [School of Information and Communication Technology, KTH (Royal Institute of Technology) Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)

2008-12-05

This work presents the selective epitaxial growth (SEG) of Si{sub 1-x}Ge{sub x} (x = 0.15-0.315) layers with high amount of boron (1 x 10{sup 20}-1 x 10{sup 21} cm{sup -3}) in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. The influence of the growth rate and strain on boron incorporation has been studied. A focus has been made on the strain distribution and boron incorporation in SEG of SiGe layers.

Auger electron emission initiated by the creation of valence-band holes in graphene by positron annihilation.

Science.gov (United States)

Chirayath, V A; Callewaert, V; Fairchild, A J; Chrysler, M D; Gladen, R W; Mcdonald, A D; Imam, S K; Shastry, K; Koymen, A R; Saniz, R; Barbiellini, B; Rajeshwar, K; Partoens, B; Weiss, A H

2017-07-13

Auger processes involving the filling of holes in the valence band are thought to make important contributions to the low-energy photoelectron and secondary electron spectrum from many solids. However, measurements of the energy spectrum and the efficiency with which electrons are emitted in this process remain elusive due to a large unrelated background resulting from primary beam-induced secondary electrons. Here, we report the direct measurement of the energy spectra of electrons emitted from single layer graphene as a result of the decay of deep holes in the valence band. These measurements were made possible by eliminating competing backgrounds by employing low-energy positrons (holes by annihilation. Our experimental results, supported by theoretical calculations, indicate that between 80 and 100% of the deep valence-band holes in graphene are filled via an Auger transition.

Analysis of materials modifications caused by UV laser micro drilling of via holes in AlGaN/GaN transistors on SiC

Energy Technology Data Exchange (ETDEWEB)

Wernicke, Tim [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)]. E-mail: tim.wernicke@fbh-berlin.de; Krueger, Olaf [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany); Herms, Martin [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany); Wuerfl, Joachim [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany); Kirmse, Holm [Humboldt-Universitaet zu Berlin, Institut fuer Physik, AG Kristallographie, Newtonstr. 15, 12489 Berlin (Germany); Neumann, Wolfgang [Humboldt-Universitaet zu Berlin, Institut fuer Physik, AG Kristallographie, Newtonstr. 15, 12489 Berlin (Germany); Behm, Thomas [Technische Universitaet Bergakademie Freiberg, Institut fuer Theoretische Physik, Bernhard-von-Cotta-Str. 4, 09596 Freiberg (Germany); Irmer, Gert [Technische Universitaet Bergakademie Freiberg, Institut fuer Theoretische Physik, Bernhard-von-Cotta-Str. 4, 09596 Freiberg (Germany); Traenkle, Guenther [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

2007-07-31

Pulsed UV laser drilling can be applied to fabricate vertical electrical interconnects (vias) for AlGaN/GaN high electron mobility transistor devices on single-crystalline silicon carbide (SiC) substrate. Through-wafer micro holes with a diameter of 50-100 {mu}m were formed in 400 {mu}m thick bulk 4H-SiC by a frequency-tripled solid-state laser (355 nm) with a pulse width of {<=}30 ns and a focal spot size of {approx}15 {mu}m. The impact of laser machining on the material system in the vicinity of micro holes was investigated by means of micro-Raman spectroscopy and transmission electron microscopy. After removing the loosely deposited debris by etching in buffered hydrofluoric acid, a layer of <4 {mu}m resolidified material remains at the side walls of the holes. The thickness of the resolidified layer depends on the vertical distance to the hole entry as observed by scanning electron microscopy. Micro-Raman spectra indicate a change of internal strain due to laser drilling and evidence the formation of nanocrystalline silicon (Si). Microstructure analysis of the vias' side walls using cross sectional TEM reveals altered degree of crystallinity in SiC. Layers of heavily disturbed SiC, and nanocrystalline Si are formed by laser irradiation. The layers are separated by 50-100 nm thick interface regions. No evidence of extended defects, micro cracking or crystal damage was found beneath the resolidified layer. The precision of UV laser micro ablation of SiC using nanosecond pulses is not limited by laser-induced extended crystal defects.

Effects of electron blocking and hole trapping of the red guest emitter materials on hybrid white organic light emitting diodes

International Nuclear Information System (INIS)

Hong, Lin-Ann; Vu, Hoang-Tuan; Juang, Fuh-Shyang; Lai, Yun-Jr; Yeh, Pei-Hsun; Tsai, Yu-Sheng

2013-01-01

Hybrid white organic light emitting diodes (HWOLEDs) with fluorescence and phosphorescence hybrid structures are studied in this work. HWOLEDs were fabricated with blue/red emitting layers: fluorescent host material doped with sky blue material, and bipolar phosphorescent host emitting material doped with red dopant material. An electron blocking layer is applied that provides hole red guest emitter hole trapping effects, increases the charge carrier injection quantity into the emitting layers and controls the recombination zone (RZ) that helps balance the device color. Spacer layers were also inserted to expand the RZ, increase efficiency and reduce energy quenching along with roll-off effects. The resulting high efficiency warm white OLED device has the lower highest occupied molecule orbital level red guest material, current efficiency of 15.9 cd/A at current density of 20 mA/cm 2 , and Commission Internationale de L'Eclairage coordinates of (0.34, 0.39)

Effects of electron blocking and hole trapping of the red guest emitter materials on hybrid white organic light emitting diodes

Energy Technology Data Exchange (ETDEWEB)

Hong, Lin-Ann; Vu, Hoang-Tuan [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Juang, Fuh-Shyang, E-mail: fsjuang@seed.net.tw [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Lai, Yun-Jr [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China); Yeh, Pei-Hsun [Raystar Optronics, Inc., 5F No. 25, Keya Rd. Daya Township, Taichung County, Taiwan (China); Tsai, Yu-Sheng [National Formosa University, Institute of Electro-Optical and Materials Science, Huwei, Yunlin County, Taiwan (China)

2013-10-01

Hybrid white organic light emitting diodes (HWOLEDs) with fluorescence and phosphorescence hybrid structures are studied in this work. HWOLEDs were fabricated with blue/red emitting layers: fluorescent host material doped with sky blue material, and bipolar phosphorescent host emitting material doped with red dopant material. An electron blocking layer is applied that provides hole red guest emitter hole trapping effects, increases the charge carrier injection quantity into the emitting layers and controls the recombination zone (RZ) that helps balance the device color. Spacer layers were also inserted to expand the RZ, increase efficiency and reduce energy quenching along with roll-off effects. The resulting high efficiency warm white OLED device has the lower highest occupied molecule orbital level red guest material, current efficiency of 15.9 cd/A at current density of 20 mA/cm{sup 2}, and Commission Internationale de L'Eclairage coordinates of (0.34, 0.39)

Different Techniques For Producing Precision Holes (>20 mm) In Hardened Steel—Comparative Results

Science.gov (United States)

Coelho, R. T.; Tanikawa, S. T.

2009-11-01

High speed machining (HSM), or high performance machining, has been one of the most recent technological advances. When applied to milling operations, using adequate machines, CAM programs and tooling, it allows cutting hardened steels, which was not feasible just a couple of years ago. The use of very stiff and precision machines has created the possibilities of machining holes in hardened steels, such as AISI H13 with 48-50 HRC, using helical interpolations, for example. Such process is particularly useful for holes with diameter bigger than normal solid carbide drills commercially available, around 20 mm, or higher. Such holes may need narrow tolerances, fine surface finishing, which can be obtained just by end milling operations. The present work compares some of the strategies used to obtain such holes by end milling, and also some techniques employed to finish them, by milling, boring and also by fine grinding at the same machine. Results indicate that it is possible to obtain holes with less than 0.36 m in circularity, 7.41 m in cylindricity and 0.12 m in surface roughness Ra. Additionally, there is less possibilities of obtaining heat affected layers when using such technique.

Supersaturated Self-Assembled Charge-Selective Interfacial Layers for Organic Solar Cells

Science.gov (United States)

2014-11-24

layers (IFLs) on the tin-doped indium oxide (ITO) anodes of organic photovoltaic (OPV) cells, a series of Ar2N-(CH2)n-SiCl3 precursors with Ar = 3,4...Bulk- heterojunction OPV devices are fabricated with these SHSAMs: ITO/IFL/poly[[4,8- bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][2...phobicity,15,19,20 electrical conductivity,21−23 and charge in- jection/collection selectivity through the film.1,2,10 For example, on metal oxide substrates

A Dancing Black Hole

Science.gov (United States)

Shoemaker, Deirdre; Smith, Kenneth; Schnetter, Erik; Fiske, David; Laguna, Pablo; Pullin, Jorge

2002-04-01

Recently, stationary black holes have been successfully simulated for up to times of approximately 600-1000M, where M is the mass of the black hole. Considering that the expected burst of gravitational radiation from a binary black hole merger would last approximately 200-500M, black hole codes are approaching the point where simulations of mergers may be feasible. We will present two types of simulations of single black holes obtained with a code based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of the Einstein evolution equations. One type of simulations addresses the stability properties of stationary black hole evolutions. The second type of simulations demonstrates the ability of our code to move a black hole through the computational domain. This is accomplished by shifting the stationary black hole solution to a coordinate system in which the location of the black hole is time dependent.

Enhancement of Photovoltaic Performance by Utilizing Readily Accessible Hole Transporting Layer of Vanadium(V) Oxide Hydrate in a Polymer-Fullerene Blend Solar Cell.

Science.gov (United States)

Jiang, Youyu; Xiao, Shengqiang; Xu, Biao; Zhan, Chun; Mai, Liqiang; Lu, Xinhui; You, Wei

2016-05-11

Herein, a successful application of V2O5·nH2O film as hole transporting layer (HTL) instead of PSS in polymer solar cells is demonstrated. The V2O5·nH2O layer was spin-coated from V2O5·nH2O sol made from melting-quenching sol-gel method by directly using vanadium oxide powder, which is readily accessible and cost-effective. V2O5·nH2O (n ≈ 1) HTL is found to have comparable work function and smooth surface to that of PSS. For the solar cell containing V2O5·nH2O HTL and the active layer of the blend of a novel polymer donor (PBDSe-DT2PyT) and the acceptor of PC71BM, the PCE was significantly improved to 5.87% with a 30% increase over 4.55% attained with PSS HTL. Incorporation of V2O5·nH2O as HTL in the polymer solar cell was found to enhance the crystallinity of the active layer, electron-blocking at the anode and the light-harvest in the wavelength range of 400-550 nm in the cell. V2O5·nH2O HTL improves the charge generation and collection and suppress the charge recombination within the PBDSe-DT2PyT:PC71BM solar cell, leading to a simultaneous enhancement in Voc, Jsc, and FF. The V2O5·nH2O HTL proposed in this work is envisioned to be of great potential to fabricate highly efficient PSCs with low-cost and massive production.

XFEM Modelling of Multi-holes Plate with Single-row and Staggered Holes Configurations

Directory of Open Access Journals (Sweden)

Supar Khairi

2017-01-01

Full Text Available Joint efficiency is the key to composite structures assembly design, good structures response is dependent upon multi-holes behavior as subjected to remote loading. Current benchmarking work were following experimental testing series taken from literature on multi-holes problem. Eleven multi-hole configurations were investigated with various pitch and gage distance of staggered holes and non-staggered holes (single-row holes. Various failure modes were exhibited, most staggered holes demonstrates staggered crack path but non-staggered holes series displayed crack path along net-section plane. Stress distribution were carried out and good agreement were exhibited in experimental observation as reported in the respective literature. Consequently, strength prediction work were carried out under quasi-static loading, most showed discrepancy between 8% -31%, better prediction were exhibited in thicker and non-staggered holes plate combinations.

Effect of tunneling layers on the performances of floating-gate based organic thin-film transistor nonvolatile memories

International Nuclear Information System (INIS)

Wang, Wei; Han, Jinhua; Ying, Jun; Xiang, Lanyi; Xie, Wenfa

2014-01-01

Two types of floating-gate based organic thin-film transistor nonvolatile memories (FG-OTFT-NVMs) were demonstrated, with poly(methyl methacrylate co glycidyl methacrylate) (P(MMA-GMA)) and tetratetracontane (TTC) as the tunneling layer, respectively. Their device performances were measured and compared. In the memory with a P(MMA-GMA) tunneling layer, typical unipolar hole transport was obtained with a relatively small mobility of 0.16 cm 2 /V s. The unidirectional shift of turn-on voltage (V on ) due to only holes trapped/detrapped in/from the floating gate resulted in a small memory window of 12.5 V at programming/erasing voltages (V P /V E ) of ±100 V and a nonzero reading voltage. Benefited from the well-ordered molecule orientation and the trap-free surface of TTC layer, a considerably high hole mobility of 1.7 cm 2 /V s and a visible feature of electrons accumulated in channel and trapped in floating-gate were achieved in the memory with a TTC tunneling layer. High hole mobility resulted in a high on current and a large memory on/off ratio of 600 at the V P /V E of ±100 V. Both holes and electrons were injected into floating-gate and overwritten each other, which resulted in a bidirectional V on shift. As a result, an enlarged memory window of 28.6 V at the V P /V E of ±100 V and a zero reading voltage were achieved. Based on our results, a strategy is proposed to optimize FG-OTFT-NVMs by choosing a right tunneling layer to improve the majority carrier mobility and realize ambipolar carriers injecting and trapping in the floating-gate.

White OLED using {beta}-diketones rare earth binuclear complex as emitting layer

Energy Technology Data Exchange (ETDEWEB)

Quirino, W.G. [LOEM, Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, PUC-Rio, P.O.Box 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil); Legnani, C. [LOEM, Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, PUC-Rio, P.O.Box 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil); Cremona, M. [LOEM, Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, PUC-Rio, P.O.Box 38071, Rio de Janeiro, RJ, CEP 22453-970 (Brazil)]. E-mail: cremona@fis.puc-rio.br; Lima, P.P. [Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, UFPE-CCEN, Recife, PE, 50670-901 (Brazil); Junior, S.A. [Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, UFPE-CCEN, Recife, PE, 50670-901 (Brazil); Malta, O.L. [Departamento de Quimica Fundamental, Universidade Federal de Pernambuco, UFPE-CCEN, Recife, PE, 50670-901 (Brazil)

2006-01-03

In this work, the fabrication and the characterization of a white triple-layer OLED using a {beta}-diketones binuclear complex [Eu(btfa){sub 3}phenterpyTb(acac){sub 3}] as the emitting layer is reported. The devices were assembled using a heterojunction between three organic molecular materials: the N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB) as hole-transporting layer, the {beta}-diketones binuclear complex and the tris(8-hydroxyquinoline aluminum) (Alq{sub 3}) as the electron transporting layer. All the organic layers were sequentially deposited under high vacuum environment by thermal evaporation onto ITO substrates and without breaking vacuum. Continuous electroluminescence emission was obtained varying the applied bias voltage from 10 to 22 V showing a wide emission band from 400 to 700 nm with about 100 cd/m{sup 2} of luminance. The white emission results from a combined action between the binuclear complex, acting as hole blocking and emitting layer, blue from NPB and the typical Alq{sub 3} green emission. The intensity ratio of the peaks is determined by the layer thickness and by the bias voltage applied to the OLED, allowing us to obtain a color tunable light source.

A pillar-layered metal-organic framework as luminescent sensor for selective and reversible response of chloroform

Energy Technology Data Exchange (ETDEWEB)

Wang, Kun; Li, Shuni; Jiang, Yucheng; Hu, Mancheng; Zhai, Quan-Guo, E-mail: zhaiqg@snnu.edu.cn

2017-03-15

A new 3D metal-organic framework, namely, (Zn{sub 4}(H{sub 2}BPTC){sub 2}(HCOO){sub 4}){sub n} (SNNU-1, H{sub 4}BPTC=biphenyl-3,3',5,5'-tetracarboxylic acid, SNNU=Shaanxi Normal University) has been solvothermal synthesized. Four independent tetrahedral Zn atoms are connected by organic ligands to form a 2D Zn-H{sub 2}BPTC layer, which is further bridged by in-situ generated HCOO{sup -} to give the 3D pillar-layered framework of SNNU-1. Unique Zn and H{sub 2}BPTC all act as 4-connected nodes leading to a new 4,4,4-connected topological net with point symbol of (4·5·6{sup 2}·8{sup 2})(4·5{sup 2}·6{sup 2}·8)(5{sup 2}·6{sup 3}·7). Notably, intense blue emission band is observed for SNNU-1, which exhibits solvent-dependent effect. Compared to other common organic solvents, chloroform can specially improve the photoluminescent intensity of SNNU-1. Further repeated response and release experiments clearly showed that SNNU-1 can act as luminescent sensor for selective and reversible detection of chloroform. - Graphical abstract: Zn{sup 2+} ions are bridged by aromatic tetracarboxylate ligands and inorganic formate anions to give a microporous pillar layered open-framework, which exhibits not only strong photoluminescence but also selective and reversible luminescent sensing for chloroform. - Highlights: • Novel Zn-tetracarboxylate-formate microporous pillar layered open-framework. • New 4,4,4-connected topology and rod-packing net. • Solvent-dependent photoluminescent intensity. • Selective and reversible response for chloroform.

Site selection

International Nuclear Information System (INIS)

Olsen, C.W.

1983-07-01

The conditions and criteria for selecting a site for a nuclear weapons test at the Nevada Test Site are summarized. Factors considered are: (1) scheduling of drill rigs, (2) scheduling of site preparation (dirt work, auger hole, surface casing, cementing), (3) schedule of event (when are drill hole data needed), (4) depth range of proposed W.P., (5) geologic structure (faults, Pz contact, etc.), (6) stratigraphy (alluvium, location of Grouse Canyon Tuff, etc.), (7) material properties (particularly montmorillonite and CO 2 content), (8) water table depth, (9) potential drilling problems (caving), (10) adjacent collapse craters and chimneys, (11) adjacent expended but uncollapsed sites, (12) adjacent post-shot or other small diameter holes, (13) adjacent stockpile emplacement holes, (14) adjacent planned events (including LANL), (15) projected needs of Test Program for various DOB's and operational separations, and (16) optimal use of NTS real estate

Hole-transport limited S-shaped I-V curves in planar heterojunction organic photovoltaic cells

Science.gov (United States)

Zhang, Minlu; Wang, Hui; Tang, C. W.

2011-11-01

Current-voltage (I-V) characteristics of planar heterojunction organic photovoltaic cells based on N',N'-Di-[(1-naphthyl)-N',N'-diphenyl]-1,1'-biphenyl)-4,4'-diamine (NPB) and C60 are investigated. Through variation of the layer thickness and composition, specifically chemical doping NPB with MoOx, we show that the hole-transport limitation in the NPB layer is the determining factor in shaping the I-V characteristics of NPB/C60 cells.

Effect of strain, substrate surface and growth rate on B-doping in selectively grown SiGe layers

International Nuclear Information System (INIS)

Ghandi, R.; Kolahdouz, M.; Hallstedt, J.; Wise, R.; Wejtmans, Hans; Radamson, H.H.

2008-01-01

In this work, the role of strain and growth rate on boron incorporation in selective epitaxial growth (SEG) of B-doped Si 1-x Ge x (x = 0.15-0.25) layers in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. A focus has been made on the strain distribution and B incorporation in SEG of SiGe layers

Effect of strain, substrate surface and growth rate on B-doping in selectively grown SiGe layers

Energy Technology Data Exchange (ETDEWEB)

Ghandi, R. [School of Information and Communication Technology, KTH (Royal Institute of Technology), Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)], E-mail: ghandi@kth.se; Kolahdouz, M.; Hallstedt, J. [School of Information and Communication Technology, KTH (Royal Institute of Technology), Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden); Wise, R.; Wejtmans, Hans [Texas Instrument, 13121 TI Boulevard, Dallas, Tx 75243 (United States); Radamson, H.H. [School of Information and Communication Technology, KTH (Royal Institute of Technology), Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)

2008-11-03

In this work, the role of strain and growth rate on boron incorporation in selective epitaxial growth (SEG) of B-doped Si{sub 1-x}Ge{sub x} (x = 0.15-0.25) layers in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. A focus has been made on the strain distribution and B incorporation in SEG of SiGe layers.

Experiments on ion acoustic typed double layers

International Nuclear Information System (INIS)

Chan, C.; Cho, M.H.; Intrator, T.; Hershkowitz, N.

1984-01-01

The formation of small amplitude double layers with potential drops the order of the electron temperature, was examined experimentally by pulsing a grid and thereby changing the electron drift across the target chamber of a triple plasma device. The rarefactive part of a long wavelength, low frequency ion wave grew in amplitude due to the presence of slowly drifting electrons. The corresponding current limitation led to the formation of the double layers. Depending on the plasma conditions, the asymmetric double layers either transform into a weak monotonic layer, a propagating shock, or a series of rarefactive solitary pulses. The rarefactive pulses propagate with Mach number less than one and resemble solitary plasma holes with density cavities in both the electron and the ion density profiles

Development of solar selective absorber layers on aluminium. Final report; Entwicklung solarselektiver Absorberschichten auf Aluminium fuer Solarkollektoren. Abschlussbericht

Energy Technology Data Exchange (ETDEWEB)

Hoenicke, D.; Moeller, T.; Schwarz, T.

1998-01-31

A new electrolytic process was developed to form solar selective layers on aluminium. In the developed process, both the formation of the alumina layer and the deposition of metals into the layer takes place in only one treatment step using a single electrolysis bath. The main step of the so called ISOC-method (impulse structured oxide ceramic) is the anodic oxidation of aluminium which was carried out by using a pulse technique at different voltages. During the anodic polarisation a thin alumina ceramic layer was formed, while the cathodic led to the metal deposition as copper and nickel. The conditions of the electrolysis were varied in order to estimate optimal parameters achieving solar selective layers with high selectivity. Furthermore, a scale-up of the lab scale apparatus to a mini plant was carried out. Finally, the corrosion resistance of the absorber layers was improved by the formation of a thin hydrophobic overlayer using a sol-gel treatment. (orig.) [Deutsch] Ein neuartiges Behandlungsverfahren zur Erzeugung von solarselektiven Absorberschichten auf Aluminium wurde entwickelt. Bei dieser elektrochemischen Behandlung wird in einem Einstufenprozess mit einem Elektrolyten durch eine Kombination von anodischer Oxidation und bipolarer Pulsbehandlung auf der Oberflaeche des Aluminiums eine impulsstrukturierte Oxidkeramik (ISOK) erzeugt. Dabei entsteht durch eine anodische Oxidation eine strukturierte Aluminiumoxidschicht. Bei der bipolaren Pulsbehandlung erfolgt dann eine Abscheidung der im ISOK-Elektrolyten befindlichen Metalle Cu und Ni auf oder in die Aluminiumoxidoberflaeche. Die ISOK-Behandlung wurde vom Labormassstab zu einem ISOK-Verfahren im Miniplant-Massstab entwickelt. Der Einfluss der elektrischen Parameter und der chemischen Zusammensetzung der ISOK-Elektrolyte wurde untersucht. Durch eine auf das ISOK-Verfahren abgestimmte Nachbehandlung, ein Tauchverfahren in einer Sol-Gel-Loesung, entsteht ein Schichtsystem mit hoher Solarselektivitaet

Black holes will break up solitons and white holes may destroy them

International Nuclear Information System (INIS)

Akbar, Fiki T.; Gunara, Bobby E.; Susanto, Hadi

2017-01-01

Highlights: • What happens if a soliton collides with a black or white hole? • Solitons can pass through black hole horizons, but they will break up into several solitons after the collision. • In the interaction with a white hole horizon, solitons either pass through the horizon or will be destroyed by it. - Abstract: We consider a quantum analogue of black holes and white holes using Bose–Einstein condensates. The model is described by the nonlinear Schrödinger equation with a ‘stream flow’ potential, that induces a spatial translation to standing waves. We then mainly consider the dynamics of dark solitons in a black hole or white hole flow analogue and their interactions with the event horizon. A reduced equation describing the position of the dark solitons was obtained using variational method. Through numerical computations and comparisons with the analytical approximation we show that solitons can pass through black hole horizons even though they will break up into several solitons after the collision. In the interaction with a white hole horizon, we show that solitons either pass through the horizon or will be destroyed by it.

Black holes will break up solitons and white holes may destroy them

Energy Technology Data Exchange (ETDEWEB)

Akbar, Fiki T., E-mail: ftakbar@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10, Bandung, 40132 (Indonesia); Gunara, Bobby E., E-mail: bobby@fi.itb.ac.id [Theoretical Physics Laboratory, Theoretical High Energy Physics and Instrumentation Research Group, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha no. 10, Bandung, 40132 (Indonesia); Susanto, Hadi, E-mail: hsusanto@essex.ac.uk [Department of Mathematical Sciences, University of Essex, Colchester, CO4 3SQ (United Kingdom)

2017-06-15

Highlights: • What happens if a soliton collides with a black or white hole? • Solitons can pass through black hole horizons, but they will break up into several solitons after the collision. • In the interaction with a white hole horizon, solitons either pass through the horizon or will be destroyed by it. - Abstract: We consider a quantum analogue of black holes and white holes using Bose–Einstein condensates. The model is described by the nonlinear Schrödinger equation with a ‘stream flow’ potential, that induces a spatial translation to standing waves. We then mainly consider the dynamics of dark solitons in a black hole or white hole flow analogue and their interactions with the event horizon. A reduced equation describing the position of the dark solitons was obtained using variational method. Through numerical computations and comparisons with the analytical approximation we show that solitons can pass through black hole horizons even though they will break up into several solitons after the collision. In the interaction with a white hole horizon, we show that solitons either pass through the horizon or will be destroyed by it.

Ion implantation into amorphous Si layers to form carrier-selective contacts for Si solar cells

International Nuclear Information System (INIS)

Feldmann, Frank; Mueller, Ralph; Reichel, Christian; Hermle, Martin

2014-01-01

This paper reports our findings on the boron and phosphorus doping of very thin amorphous silicon layers by low energy ion implantation. These doped layers are implemented into a so-called tunnel oxide passivated contact structure for Si solar cells. They act as carrier-selective contacts and, thereby, lead to a significant reduction of the cell's recombination current. In this paper we address the influence of ion energy and ion dose in conjunction with the obligatory high-temperature anneal needed for the realization of the passivation quality of the carrier-selective contacts. The good results on the phosphorus-doped (implied V oc = 725 mV) and boron-doped passivated contacts (iV oc = 694 mV) open a promising route to a simplified interdigitated back contact (IBC) solar cell featuring passivated contacts. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

A microstructured Polymer Optical Fiber Biosensor

DEFF Research Database (Denmark)

Emiliyanov, Grigoriy Andreev; Jensen, Jesper Bo; Hoiby, Poul E.

2006-01-01

We demonstrate selective detection of fluorophore labeled antibodies from minute samples probed by a sensor layer of the complementary biomolecules immobilized inside the air holes of microstructured Polymer Optical Fibers.......We demonstrate selective detection of fluorophore labeled antibodies from minute samples probed by a sensor layer of the complementary biomolecules immobilized inside the air holes of microstructured Polymer Optical Fibers....

Thermally and electrochemically stable amorphous hole-transporting materials based on carbazole dendrimers for electroluminescent devices

International Nuclear Information System (INIS)

Promarak, Vinich; Ichikawa, Musubu; Sudyoadsuk, Taweesak; Saengsuwan, Sayant; Jungsuttiwong, Siriporn; Keawin, Tinnagon

2008-01-01

Amorphous hole-transporting carbazole dendrimers, 1,4-bis[3,6-di(carbazol-9-yl)carbazol-9-yl]-2,6-di(2-ethylhexyloxy)benzene (G2CB) and 1,4-bis[3,6-di(carbazol-9-yl)carbazol-9-yl]-9-(2-ethylhexyl)carbazole (G2CC), were synthesized by a divergent approach involving bromination and Ullmann coupling reactions. Compounds G2CB and G2CC showed high thermal stability (T g = 206 to 245 deg. C) and excellent electrochemical reversibility. Double-layer organic light-emitting diodes were fabricated by using G2CB and G2CC as hole-transporting layers (HTLs) and tris(8-quinolinato)aluminum (Alq 3 ) as light-emissive layer with the device configuration of indium tin oxide/HTL/Alq 3 /LiF:Al. Both devices exhibited bright green emission from Alq 3 . The device using G2CC as HTL has the best performance with a maximum brightness of 8900 cd/m 2 at 14 V and a low turn-on voltage of 3.5 V

Fabrication of Polymer Solar Cells Using Aqueous Processing for All Layers Including the Metal Back Electrode

DEFF Research Database (Denmark)

Søndergaard, Roar; Helgesen, Martin; Jørgensen, Mikkel

2011-01-01

The challenges of printing all layers in polymer solar cells from aqueous solution are met by design of inks for the electron-, hole-, active-, and metallic back electrode-layers. The conversion of each layer to an insoluble state after printing enables multilayer formation from the same solvent...

Caged black holes: Black holes in compactified spacetimes. I. Theory

International Nuclear Information System (INIS)

Kol, Barak; Sorkin, Evgeny; Piran, Tsvi

2004-01-01

In backgrounds with compact dimensions there may exist several phases of black objects including a black hole and a black string. The phase transition between them raises questions and touches on fundamental issues such as topology change, uniqueness, and cosmic censorship. No analytic solution is known for the black hole, and moreover one can expect approximate solutions only for very small black holes, while phase transition physics happens when the black hole is large. Hence we turn to numerical solutions. Here some theoretical background to the numerical analysis is given, while the results will appear in a subsequent paper. The goals for a numerical analysis are set. The scalar charge and tension along the compact dimension are defined and used as improved order parameters which put both the black hole and the black string at finite values on the phase diagram. The predictions for small black holes are presented. The differential and the integrated forms of the first law are derived, and the latter (Smarr's formula) can be used to estimate the 'overall numerical error'. Field asymptotics and expressions for physical quantities in terms of the numerical values are supplied. The techniques include the 'method of equivalent charges', free energy, dimensional reduction, and analytic perturbation for small black holes

Electron-hole pair effects in methane dissociative chemisorption on Ni(111)

Energy Technology Data Exchange (ETDEWEB)

Luo, Xuan; Jiang, Bin, E-mail: bjiangch@ustc.edu.cn [Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Juaristi, J. Iñaki [Centro de Física de Materiales CFM/MPC(CSIC-UPV/EHU), P. Manuel de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center DIPC, P. Manuel de Lardizabal 4, 20018 San Sebastián (Spain); Departamento de Física de Materiales, Facultad de Químicas, Universidad del País Vasco (UPV/EHU), Apartado 1072, 20080 San Sebastián (Spain); Alducin, Maite [Centro de Física de Materiales CFM/MPC(CSIC-UPV/EHU), P. Manuel de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center DIPC, P. Manuel de Lardizabal 4, 20018 San Sebastián (Spain); Guo, Hua [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

2016-07-28

The dissociative chemisorption of methane on metal surfaces has attracted much attention in recent years as a prototype of gas-surface reactions in understanding the mode specific and bond selective chemistry. In this work, we systematically investigate the influence of electron-hole pair excitations on the dissociative chemisorption of CH{sub 4}/CH{sub 3}D/CHD{sub 3} on Ni(111). The energy dissipation induced by surface electron-hole pair excitations is modeled as a friction force introduced in the generalized Langevin equation, in which the independent atomic friction coefficients are determined within the local-density friction approximation. Quasi-classical trajectory calculations for CH{sub 4}/CH{sub 3}D/CHD{sub 3} have been carried out on a recently developed twelve-dimensional potential energy surface. Comparing the dissociation probabilities obtained with and without friction, our results clearly indicate that the electron-hole pair effects are generally small, both on absolute reactivity of each vibrational state and on the mode specificity and bond selectivity. Given similar observations in both water and methane dissociation processes, we conclude that electron-hole pair excitations would not play an important role as long as the reaction is direct and the interaction time between the molecule and metal electrons is relatively short.

Porous layered double hydroxides synthesized using oxygen generated by decomposition of hydrogen peroxide

NARCIS (Netherlands)

Gonzalez Rodriguez, P.; de Ruiter, M.P.; Wijnands, Tom; ten Elshof, Johan E.

2017-01-01

Porous magnesium-aluminium layered double hydroxides (LDH) were prepared through intercalation and decomposition of hydrogen peroxide (H2O2). This process generates oxygen gas nano-bubbles that pierce holes in the layered structure of the material by local pressure build-up. The decomposition of the

Alternate Explosions: Collapse and Accretion Events with Red Holes instead of Black Holes

OpenAIRE

Graber, James S.

1999-01-01

A red hole is "just like a black hole" except it lacks an event horizon and a singularity. As a result, a red hole emits much more energy than a black hole during a collapse or accretion event. We consider how a red hole solution can solve the "energy crisis" and power extremely energetic gamma ray bursts and hypernovae.

Black and white holes

International Nuclear Information System (INIS)

Zeldovich, Ya.; Novikov, I.; Starobinskij, A.

1978-01-01

The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius Rsub(r). At t>>Rsub(r)/c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius. (J.B.)

Black and white holes

Energy Technology Data Exchange (ETDEWEB)

Zeldovich, Ya; Novikov, I; Starobinskii, A

1978-07-01

The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius R/sub r/. At t>>R/sub r//c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius.

Astrophysical black holes

CERN Document Server

Gorini, Vittorio; Moschella, Ugo; Treves, Aldo; Colpi, Monica

2016-01-01

Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical black holes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of black hole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized black holes observed in the Milky Way, the formation and evolution of supermassive black holes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of black holes supporting theoretical understanding of the coalescence of black holes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.

ITO electrode/photoactive layer interface engineering for efficient inverted polymer solar cells based on P3HT and PCBM using a solution-processed titanium chelate

International Nuclear Information System (INIS)

Zhang Wenqing; Zheng Hua; Tan Zhan'ao; Qian Deping; Li Liangjie; Xu Qi; Li Shusheng; Li Yongfang

2012-01-01

We report efficient inverted polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) using alcohol-soluble titanium (diisopropoxide) bis (2,4-pentanedionate) (TIPD) as an electron selective layer between the indium tin oxide (ITO) electrode and the photoactive layer. The thermally annealed TIPD layer is highly transparent in the visible range and shows effective electron collection ability. By optimizing the electron-collecting layer, the photoactive layer and the hole-collecting layer, the power conversion efficiency (PCE) of the inverted device with the structure ITO/TIPD/P3HT : PCBM/MoO 3 /Ag reaches 4.10% under the illumination of AM1.5G, 100 mW cm -2 , which is among the highest values for inverted PSCs based on P3HT : PCBM. The PCE of the inverted device is improved in comparison with the conventional device (3.77%) under the same experimental conditions. (paper)

Thiol-ene thermosets exploiting surface reactivity for layer-by-layer structures and control of penetration depth for selective surface reactivity

DEFF Research Database (Denmark)

Daugaard, Anders Egede; Westh, Andreas; Pereira Rosinha Grundtvig, Ines

Thiol-ene thermosets have been shown to be an efficient platform for preparation of functional polymer surfaces. Especially the effectiveness and versatility of the system has enabled a large variety of network properties to be obtained in a simple and straight-forward way. Due to its selectivity......, various thiols and allyl or other vinyl reactants can be used to obtain either soft and flexible1 or more rigid functional thermosets 2. The methodology permits use of etiher thermal or photochemical conditions both for matrix preparation as well as for surface functionalization. Due to excess reactive...... groups in thµe surface of thiol-ene thermosets, it is possible to prepare surface functional thermosets or to exploit the reactive groups for modular construction and subsequent chemical bonding. Here a different approach preparing monolithic layer-by-layer structures with controlled mechanical...

Selective contacts drive charge extraction in quantum dot solids via asymmetry in carrier transfer kinetics

KAUST Repository

Mora-Sero, Ivan; Bertoluzzi, Luca; Gonzalez-Pedro, Victoria; Gimenez, Sixto; Fabregat-Santiago, Francisco; Kemp, Kyle W.; Sargent, Edward H.; Bisquert, Juan

2013-01-01

Colloidal quantum dot solar cells achieve spectrally selective optical absorption in a thin layer of solution-processed, size-effect tuned, nanoparticles. The best devices built to date have relied heavily on drift-based transport due to the action of an electric field in a depletion region that extends throughout the thickness of the quantum dot layer. Here we study for the first time the behaviour of the best-performing class of colloidal quantum dot films in the absence of an electric field, by screening using an electrolyte. We find that the action of selective contacts on photovoltage sign and amplitude can be retained, implying that the contacts operate by kinetic preferences of charge transfer for either electrons or holes. We develop a theoretical model to explain these experimental findings. The work is the first to present a switch in the photovoltage in colloidal quantum dot solar cells by purposefully formed selective contacts, opening the way to new strategies in the engineering of colloidal quantum dot solar cells. © 2013 Macmillan Publishers Limited. All rights reserved.

Selective contacts drive charge extraction in quantum dot solids via asymmetry in carrier transfer kinetics

KAUST Repository

Mora-Sero, Ivan

2013-08-12

Colloidal quantum dot solar cells achieve spectrally selective optical absorption in a thin layer of solution-processed, size-effect tuned, nanoparticles. The best devices built to date have relied heavily on drift-based transport due to the action of an electric field in a depletion region that extends throughout the thickness of the quantum dot layer. Here we study for the first time the behaviour of the best-performing class of colloidal quantum dot films in the absence of an electric field, by screening using an electrolyte. We find that the action of selective contacts on photovoltage sign and amplitude can be retained, implying that the contacts operate by kinetic preferences of charge transfer for either electrons or holes. We develop a theoretical model to explain these experimental findings. The work is the first to present a switch in the photovoltage in colloidal quantum dot solar cells by purposefully formed selective contacts, opening the way to new strategies in the engineering of colloidal quantum dot solar cells. © 2013 Macmillan Publishers Limited. All rights reserved.

Direct Observation of Ultrafast Hole Injection from Lead Halide Perovskite by Differential Transient Transmission Spectroscopy.

Science.gov (United States)

Ishioka, Kunie; Barker, Bobby G; Yanagida, Masatoshi; Shirai, Yasuhiro; Miyano, Kenjiro

2017-08-17

Efficient charge separation at the interfaces of the perovskite with the carrier transport layers is crucial for perovskite solar cells to achieve high power conversion efficiency. We present a systematic experimental study on the hole injection dynamics from MAPbI 3 perovskite to three typical hole transport materials (HTMs). We extract the carrier dynamics directly related to the hole injection by employing a pump light with short absorption depth and comparing the transient transmission signals excited on the two sides of the sample. The differential transmission signals reveal the hole injections to PTAA and PEDOT:PSS to be complete within 1 and 2 ps, respectively, and that to NiO x to exhibit an additional slow process on a 40 ps time scale. The obtained injection dynamics are discussed in comparison with the device performance of the solar cells containing the same MAPbI 3 /HTM interfaces.

Chemical gating of epitaxial graphene through ultrathin oxide layers.

Science.gov (United States)

Larciprete, Rosanna; Lacovig, Paolo; Orlando, Fabrizio; Dalmiglio, Matteo; Omiciuolo, Luca; Baraldi, Alessandro; Lizzit, Silvano

2015-08-07

We achieved a controllable chemical gating of epitaxial graphene grown on metal substrates by exploiting the electrostatic polarization of ultrathin SiO2 layers synthesized below it. Intercalated oxygen diffusing through the SiO2 layer modifies the metal-oxide work function and hole dopes graphene. The graphene/oxide/metal heterostructure behaves as a gated plane capacitor with the in situ grown SiO2 layer acting as a homogeneous dielectric spacer, whose high capacity allows the Fermi level of graphene to be shifted by a few hundreds of meV when the oxygen coverage at the metal substrate is of the order of 0.5 monolayers. The hole doping can be finely tuned by controlling the amount of interfacial oxygen, as well as by adjusting the thickness of the oxide layer. After complete thermal desorption of oxygen the intrinsic doping of SiO2 supported graphene is evaluated in the absence of contaminants and adventitious adsorbates. The demonstration that the charge state of graphene can be changed by chemically modifying the buried oxide/metal interface hints at the possibility of tuning the level and sign of doping by the use of other intercalants capable of diffusing through the ultrathin porous dielectric and reach the interface with the metal.

Black holes in binary stars

NARCIS (Netherlands)

Wijers, R.A.M.J.

1996-01-01

Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes

The stable problem of the black-hole connected region in the Schwarzschild black hole

OpenAIRE

Tian, Guihua

2005-01-01

The stability of the Schwarzschild black hole is studied. Using the Painlev\\'{e} coordinate, our region can be defined as the black-hole-connected region(r>2m, see text) of the Schwarzschild black hole or the white-hole-connected region(r>2m, see text) of the Schwarzschild black hole. We study the stable problems of the black-hole-connected region. The conclusions are: (1) in the black-hole-connected region, the initially regular perturbation fields must have real frequency or complex frequen...

Atomic-Layer-Deposited Transparent Electrodes for Silicon Heterojunction Solar Cells

International Nuclear Information System (INIS)

Demaurex, Benedicte; Seif, Johannes P.; Smit, Sjoerd; Macco, Bart; Kessels, W. M.; Geissbuhler, Jonas; De Wolf, Stefaan; Ballif, Christophe

2014-01-01

We examine damage-free transparent-electrode deposition to fabricate high-efficiency amorphous silicon/crystalline silicon heterojunction solar cells. Such solar cells usually feature sputtered transparent electrodes, the deposition of which may damage the layers underneath. Using atomic layer deposition, we insert thin protective films between the amorphous silicon layers and sputtered contacts and investigate their effect on device operation. We find that a 20-nm-thick protective layer suffices to preserve, unchanged, the amorphous silicon layers beneath. Insertion of such protective atomic-layer-deposited layers yields slightly higher internal voltages at low carrier injection levels. However, we identify the presence of a silicon oxide layer, formed during processing, between the amorphous silicon and the atomic-layer-deposited transparent electrode that acts as a barrier, impeding hole and electron collection

THE USE OF AIR LAYERS IN BUILDING ENVELOPES FOR ENERGY SAVING DURING AIR CONDITIONING

Directory of Open Access Journals (Sweden)

S. N. Osipov

2017-01-01

Full Text Available Since there are no large natural energy resources in Belarus, energy savings ought to be a point of the special attention. With this regard it is important to develop modern ways of savings during the process of air conditioning inside new buildings with an air layer in the enclosure, especially in translucent ones. The system of ventilation of air layers in the enclosure of a building has been introduced in which air movement is caused by the gravitational and aerodynamic forces. It makes it possible to arrange further ventilation – a natural, forced or a hybrid one. With the purpose of increasing and streamlining natural draught the partitions are used separating the different parts of air layers. For natural ventilation with the use of gravitational forces the holes in the upper and lower parts of the partitions between adjacent air layers are applied. Natural ventilation in the holes of the partitions is regulated by movable shutters, blinds or other adjusting devices. For combined or forced air exchange between adjacent zones of air layers fans are used pumping air from the air layer zones with a higher temperature to zones of air layers with lower temperature and vice versa. When air exchange is forced, in order to intensify the infiltration of air into zones of air layers jets are laid on a hard surface. In order to cool a multi-layered enclosure of a building, where the movement of air between the air layers (that have been formed by internal partitions is being fulfilled by a natural, forced or combined mode, a part of the air or the total air processed inside the building (i.e. conditioned or non-conditioned air cooler as compared with the outside one is being sent to these strata. Combined or forced flow of the air processed inside the building into the air layers is done through the ducts associated with the output channels of the air conditioners. The internal partitions are equipped with the air valve hole.

Rotating black holes at future colliders. III. Determination of black hole evolution