WorldWideScience

Sample records for stable efficient light

  1. A high-light-harvesting-efficiency coumarin dye for stable dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.S.; Cui, Y.; Hara, K. [National Institute of Advanced Industrial, Science and Technology (AIST), Tsukuba, Ibaraki (Japan); Dan-oh, Y.; Kasada, C.; Shinpo, A. [Hayashibara Biochemical Laboratories, Inc., Okayama (Japan)

    2007-04-20

    A new coumarin dye for use in dye-sensitized solar cells (DSSCs) is reported. It exhibits near-unity light harvesting efficiency and incident photon-to-electron conversion efficiency over a wide spectral region in 6 {mu}m transparent TiO{sub 2} films. DSSCs based on this metal-free organic dye show long-term stability and power-conversion efficiencies of around 6 % under continuous light-soaking stress for up to 1000 h. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  2. Light-induced lattice expansion leads to high-efficiency and stable perovskite solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Hsinhan; Asadpour, Reza; Blancon, Jean-Christophe; Stoumpos, Constantinos C.; Durand, Oliver; Strzalka, Joseph W.; Ajayan, Pulickel M.; Tretiak, Sergei; Even, Jacky; Nie, Wanyi; Mohite, Aditya D.

    2018-04-05

    Hybrid-perovskite based high-performance optoelectronic devices and clues from their operation has led to the realization that light-induced structural dynamics play a vital role on their physical properties, device performance and stability. Here, we report that continuous light illumination leads to a uniform lattice expansion in hybrid perovskite thin-films, which is critical for obtaining high-efficiency photovoltaic devices. Correlated, in-situ structural and device characterizations reveal that light-induced lattice expansion significantly benefits the performances of a mixed-cation pure-halide planar device, boosting the power conversion efficiency from 18.5% to 20.5%. This is a direct consequence of the relaxation of local lattice strains during lattice expansion, which results in the reduction of the energetic barriers at the perovskite/contact interfaces in devices, thus improving the open circuit voltage and fill factor. The light-induced lattice expansion stabilizes these high-efficiency photovoltaic devices under continuous operation of full-spectrum 1-Sun illumination for over 1500 hours. One Sentence Summary: Light-induced lattice expansion improves crystallinity, relaxes lattice strain, which enhances photovoltaic performance in hybrid perovskite device.

  3. Color-tunable and stable-efficiency white organic light-emitting diode fabricated with fluorescent-phosphorescent emission layers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Su-Hua, E-mail: shya@cc.kuas.edu.tw; Shih, Po-Jen; Wu, Wen-Jie; Huang, Yi-Hua

    2013-10-15

    White organic light emitting diodes (OLEDs) were fabricated for color-tunable lighting applications. Fluorescent and phosphorescent hybrid emission layers (EMLs) were used to enhance the luminance and stability of the devices, which have blue-EML/CBP interlayer/green-EML/phosphorescent-sensitized-EML/red-EML structures. The influence of the composition and structure of the EMLs on the electroluminescence properties of the devices were investigated from the viewpoint of their emission spectra. The possible exciton harvesting, diffusion, transport, and annihilation processes occurring in the EMLs were also evaluated. A maximum luminance intensity of 7400 cd/m{sup 2} and a highly stable current efficiency of 3.2 cd/A were obtained. Good color tunability was achieved for the white OLEDs; the chromatic coordinates linearly shifted from pure white (0.300, 0.398) to cold white (0.261, 0.367) when the applied voltage was varied from 10 to 14 V. -- Highlights: • Exciton harvesting, diffusion, transport, and annihilation processes were evaluated. • The electroluminescence properties were investigated from the viewpoint of the emission spectra. • Good color tunability and stable-efficiency were achieved for the white OLEDs.

  4. Science-based design of stable quantum dots for energy-efficient lighting

    Energy Technology Data Exchange (ETDEWEB)

    Martin, James E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Rohwer, Lauren E. S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); van Swol, Frank B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Zhou, Xiaowang [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lu, Ping [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    II-VI quantum dots, such as CdSe and CdTe, are attractive as downconversion materials for solid-state lighting, because of their narrow linewidth, tunable emission. However, for these materials to have acceptable quantum yields (QYs) requires that they be coated with a II-VI shell material whose valence band offset serves to confine the hole to the core. Confinement prevents the hole from accessing surface traps that lead to nonradiative decay of the exciton. Examples of such hole-confined core/shell QDs include CdTe/CdSe and CdSe/CdS. Unfortunately, the shell can also cause problems due to lattice mismatch, which ranges from 4-6% for systems of interest. This lattice mismatch can create significant interface energies at the heterojunction and places the core under radial compression and the shell under tangential tension. At elevated temperatures (~240°C) interfacial diffusion can relax these stresses, as can surface reconstruction, which can expose the core, creating hole traps. But such high temperatures favor the hexagonal Wurtzite structure, which has lower QY than the cubic zinc blende structure, which can be synthesized at lower temperatures, ~140°C. In the absence of alloying the core/shell structure can become metastable, or even unstable, if the shell is too thick. This can cause result in an irregular shell or even island growth. But if the shell is too thin thermallyactivated transport of the hole to surface traps can occur. In our LDRD we have developed a fundamental atomistic modeling capability, based on Stillinger-Weber and Bond-Order potentials we developed for the entire II-VI class. These pseudo-potentials have enabled us to conduct large-scale atomistic simulations that have led to the computation of phase diagrams of II-VI QDs. These phase diagrams demonstrate that at elevated temperatures the zinc blende phase of CdTe with CdSe grown on it epitaxially becomes thermodynamically unstable due to alloying. This is accompanied by a loss of hole

  5. Highly efficient and stable phosphorescent organic light-emitting diodes employing TADF materials as host (Conference Presentation)

    Science.gov (United States)

    Fukagawa, Hirohiko; Iwasaki, Yukiko; Shimizu, Takahisa

    2016-09-01

    The OLED is one of the key devices for realizing next-generation displays and lighting. The efficiency of OLEDs has been improved markedly by employing phosphorescent emitters. However, there are two main issues in the practical application of phosphorescent OLEDs (PHOLEDs): the relatively short operational lifetime of green/blue devices and the relatively high cost owing to the use of a costly emitter with a concentration of about 10% in the emitting layer. Here, we report on our success in resolving these issues by the utilization of thermally activated delayed fluorescent (TADF) materials as the host materials for phosphorescent emitters. Operationally stable green PHOLEDs are demonstrated by employing a TADF material as the host since the triplet excitons of the host, which are key elements in operational degradation, are transferred rapidly to the emitter following the Förster process via reverse intersystem crossing from the triplet to singlet states. In this case, the concentration of the emitter can be reduced to 1-3 wt%, similar to that in fluorescent OLEDs. Although an external quantum efficiency (EQE) of about 20% is obtained in many PHOLEDs regardless of the TADF host, the operational lifetime strongly depends on the host. Our optimized green PHOLED employing only 1 wt% phosphorescent emitter exhibits an EQE of over 20%, a small efficiency roll-off, and a long operational lifetime on the order of 10,000 h with an initial luminance of 1,000 cd/m2.

  6. Highly efficient and stable organic light-emitting diodes with a greatly reduced amount of phosphorescent emitter.

    Science.gov (United States)

    Fukagawa, Hirohiko; Shimizu, Takahisa; Kamada, Taisuke; Yui, Shota; Hasegawa, Munehiro; Morii, Katsuyuki; Yamamoto, Toshihiro

    2015-05-18

    Organic light-emitting diodes (OLEDs) have been intensively studied as a key technology for next-generation displays and lighting. The efficiency of OLEDs has improved markedly in the last 15 years by employing phosphorescent emitters. However, there are two main issues in the practical application of phosphorescent OLEDs (PHOLEDs): the relatively short operational lifetime and the relatively high cost owing to the costly emitter with a concentration of about 10% in the emitting layer. Here, we report on our success in resolving these issues by the utilization of thermally activated delayed fluorescent materials, which have been developed in the past few years, as the host material for the phosphorescent emitter. Our newly developed PHOLED employing only 1 wt% phosphorescent emitter exhibits an external quantum efficiency of over 20% and a long operational lifetime of about 20 times that of an OLED consisting of a conventional host material and 1 wt% phosphorescent emitter.

  7. 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.

  8. Lithium hydride doped intermediate connector for high-efficiency and long-term stable tandem organic light-emitting diodes.

    Science.gov (United States)

    Ding, Lei; Tang, Xun; Xu, Mei-Feng; Shi, Xiao-Bo; Wang, Zhao-Kui; Liao, Liang-Sheng

    2014-10-22

    Lithium hydride (LiH) is employed as a novel n-dopant in the intermediate connector for tandem organic light-emitting diodes (OLEDs) because of its easy coevaporation with other electron transporting materials. The tandem OLEDs with two and three electroluminescent (EL) units connected by a combination of LiH doped 8-hydroxyquinoline aluminum (Alq3) and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) demonstrate approximately 2-fold and 3-fold enhancement in current efficiency, respectively. In addition, no extra voltage drop across the intermediate connector is observed. Particularly, the lifetime (T75%) in the tandem OLED with two and three EL units is substantially improved by 3.8 times and 7.4 times, respectively. The doping effect of LiH into Alq3, the charge injection, and transport characteristics of LiH-doped Alq3 are further investigated by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS).

  9. Formation of Hierarchical In2S3-CdIn2S4Heterostructured Nanotubes for Efficient and Stable Visible Light CO2Reduction.

    Science.gov (United States)

    Wang, Sibo; Guan, Bu Yuan; Lu, Yan; Lou, Xiong Wen David

    2017-12-06

    We demonstrate rational design and fabrication of hierarchical In 2 S 3 -CdIn 2 S 4 heterostructured nanotubes as efficient and stable photocatalysts for visible light CO 2 reduction. The novel self-templated strategy, including sequential anion- and cation-exchange reactions, integrates two distinct sulfide semiconductors into hierarchical tubular hybrids with homogeneous interfacial contacts and ultrathin two-dimensional (2D) nanosheet subunits. Accordingly, the hierarchical heterostructured nanotubes facilitate separation and migration of photoinduced charge carriers, enhance the adsorption and concentration of CO 2 molecules, and offer rich active sites for surface redox reactions. Benefiting from these structural and compositional features, the optimized hierarchical In 2 S 3 -CdIn 2 S 4 nanotubes without employing noble metal cocatalysts in the catalytic system manifest remarkable performance for deoxygenative reduction of CO 2 with high CO generation rate (825 μmol h -1 g -1 ) and outstanding stability under visible light irradiation.

  10. Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction as a highly efficient and stable visible light photocatalyst.

    Science.gov (United States)

    Liu, Chengbin; Cao, Chenghao; Luo, Xubiao; Luo, Shenglian

    2015-03-21

    A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Au/BiOCl heterojunction within mesoporous silica shell as stable plasmonic photocatalyst for efficient organic pollutants decomposition under visible light

    International Nuclear Information System (INIS)

    Yan, Xiaoqing; Zhu, Xiaohui; Li, Renhong; Chen, Wenxing

    2016-01-01

    Highlights: • A heterojunction of Au/BiOCl was fabricated within the mesoporous silica shell. • The compact contact between Au and BiOCl enables electrons back flow from Au to BiOCl. • Au/BiOCl@mSiO 2 plasmonic photocatalyst shows efficient visible light photoactivity. • Hydroxyl radicals are the main oxidants in formaldehyde and Rhodamine B decomposition. - Abstract: A new mesoporous silica protected plasmonic photocatalyst, Au/BiOCl@mSiO 2 , was prepared by a modified AcHE method and a subsequent UV light induced photodeposition process. The surfactant-free heterojunction allows the electrons spontaneously flow from Au to nearby BiOCl surface, leading to the accumulation of positive charges on Au surface, and negative charges on Bi species under visible light. Au/BiOCl@mSiO 2 exhibits high visible light photocatalytic efficiency in complete oxidation of aqueous formaldehyde and Rhodamin B. We showed that a positive relationship exists between the LSPR effect and rate enhancements, and leads to a hypothesis that the metallic Au LSPR enhances the photocatalytic rates on nearby semiconductors by transferring energetic electrons to BiOCl and increasing the steady-state concentration of active ·OH species by a multi-electron reduction of molecular oxygen. The ·OH species is the main oxidant in photocatalytic transformations, whose intensity is greatly enhanced in the dye-involving systems due to the synergetic effect between LSPR and dye sensitization processes. In addition, the mesoporous SiO 2 shell not only inhibits the over growth of BiOCl nanocrystals within the silica frameworks, but also protects the dissolution of chloride or Au species into aqueous solution, which ultimately makes the Au/BiOCl@mSiO 2 catalysts rather stable during photocatalysis.

  12. Nanostructured N-doped orthorhombic Nb2O5as an efficient stable photocatalyst for hydrogen generation under visible light.

    Science.gov (United States)

    Kulkarni, Aniruddha K; Praveen, C S; Sethi, Yogesh A; Panmand, Rajendra P; Arbuj, Sudhir S; Naik, Sonali D; Ghule, Anil V; Kale, Bharat B

    2017-11-07

    The synthesis of orthorhombic nitrogen-doped niobium oxide (Nb 2 O 5-x N x ) nanostructures was performed and a photocatalytic study carried out in their use in the conversion of toxic H 2 S and water into hydrogen under UV-Visible light. Nanostructured orthorhombic Nb 2 O 5-x N x was synthesized by a simple solid-state combustion reaction (SSCR). The nanostructural features of Nb 2 O 5-x N x were examined by FESEM and HRTEM, which showed they had a porous chain-like structure, with chains interlocked with each other and with nanoparticles sized less than 10 nm. Diffuse reflectance spectra depicted their extended absorbance in the visible region with a band gap of 2.4 eV. The substitution of nitrogen in place of oxygen atoms as well as Nb-N bond formation were confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. A computational study (DFT) of Nb 2 O 5-x N x was also performed for investigation and conformation of the crystal and electronic structure. N-Substitution clearly showed a narrowing of the band gap due to N 2p bands cascading above the O 2p band. Considering the band gap in the visible region, Nb 2 O 5-x N x exhibited enhanced photocatalytic activity toward hydrogen evolution (3010 μmol h -1 g -1 ) for water splitting and (9358 μmol h -1 g -1 ) for H 2 S splitting under visible light. The enhanced photocatalytic activity of Nb 2 O 5-x N x was attributed to its extended absorbance in the visible region due to its electronic structure being modified upon doping, which in turn generates more electron-hole pairs, which are responsible for higher H 2 generation. More significantly, the mesoporous nanostructure accelerated the supression of electron and hole recombination, which also contributed to the enhancement of its activity.

  13. An efficient and stable green phosphor SrBaSiO4:Eu2+ for light-emitting diodes

    International Nuclear Information System (INIS)

    Zhang Xinguo; Tang Xueping; Zhang Jilin; Gong Menglian

    2010-01-01

    Eu 2+ -activated strontium-barium silicate, SrBaSiO 4 :Eu 2+ , which is an intermediate phase between Sr 2 SiO 4 and Ba 2 SiO 4 , was synthesized by a solid-state reaction. The synthesized phosphor was efficiently excited by a broad spectral range of near UV between 300 and 450 nm, and exhibited a strong and wide green emission. As the doped Eu 2+ concentration increased from 0.005 to 0.18 (molar ratio), the emission wavelength shifted from 509 to 521 nm, and this red-shift phenomenon was discussed through a band-gap model. The concentration quenching mechanism was calculated to be a dipole-quadrupole interaction. It showed good thermal stability with T 1/2 of 170 o C and high internal quantum efficiency (78%). A green LED was fabricated with SrBaSiO 4 :Eu 2+ and a 395 nm-emitting InGaN chip and it showed a superior current tolerant property. All the results indicate that this phosphor is a good candidate as green component in fabrication of phosphor-converted white LEDs.

  14. Long-term stable stacked CsPbBr3 quantum dot films for highly efficient white light generation in LEDs.

    Science.gov (United States)

    Song, Young Hyun; Yoo, Jin Sun; Kang, Bong Kyun; Choi, Seung Hee; Ji, Eun Kyung; Jung, Hyun Suk; Yoon, Dae Ho

    2016-12-01

    We report highly efficient ethyl cellulose with CsPbBr 3 perovskite QD films for white light generation in LED application. Ethyl cellulose with CsPbBr 3 quantum dots is applied with Sr 2 Si 5 N 8  : Eu 2+ red phosphor on an InGaN blue chip, achieving a highly efficient luminous efficacy of 67.93 lm W -1 under 20 mA current.

  15. Energy Efficient Task Light

    DEFF Research Database (Denmark)

    Logadottir, Asta; Ardkapan, Siamak Rahimi; Johnsen, Kjeld

    2014-01-01

    made lenses, capable of providing the desired light distribution. The user test shows that when working with general lighti ng of 100 lx in the room the developed task lig ht with its wide light distribution provides flexibility in choosing a reading task area on the desk and provides more visibility......The objectives of this work is to develop a task light for office lighting that fulfils the minimum requirements of the European standard EN12464 - 1 : Light and lightingLighting of work places, Part 1: Indoor workplaces and the Danish standard DS 700 : Lys og belysning I arbejdsrum , or more...... specifically the requirements that apply to the work area and the immediate surrounding area. By providing a task light that fulfils the requirements for task lighting and the immediate surrounding area, the general lighting only needs to provide the illuminance levels required for background lighting...

  16. Bidentate Ligand-passivated CsPbI3 Perovskite Nanocrystals for Stable Near-unity Photoluminescence Quantum Yield and Efficient Red Light-emitting Diodes

    KAUST Repository

    Pan, Jun

    2017-12-17

    Although halide perovskite nanocrystals (NCs) are promising materials for optoelectronic devices, they suffer severely from chemical and phase instabilities. Moreover, the common capping ligands like oleic acid and oleylamine that encapsulate the NCs will form an insulating layer, precluding their utility in optoelectronic devices. To overcome these limitations, we develop a post-synthesis passivation process for CsPbI3 NCs by using a bidentate ligand, namely 2,2’-Iminodibenzoic acid. Our passivated NCs exhibit narrow red photoluminescence with exceptional quantum yield (close to unity) and substantially improved stability. The passivated NCs enabled us to realize red light-emitting diodes (LEDs) with 5.02% external quantum efficiency and 748 cd/m2 luminance, surpassing by far LEDs made from the non-passivated NCs.

  17. Ag-bridged Ag{sub 2}O nanowire network/TiO{sub 2} nanotube array p–n heterojunction as a highly efficient and stable visible light photocatalyst

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chengbin, E-mail: chem_cbliu@hnu.edu.cn [Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, Nanchang Hangkong University, Nanchang 330063 (China); State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082 (China); Cao, Chenghao [State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082 (China); Luo, Xubiao [Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, Nanchang Hangkong University, Nanchang 330063 (China); Luo, Shenglian [Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, Nanchang Hangkong University, Nanchang 330063 (China); State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082 (China)

    2015-03-21

    Graphical abstract: A unique Ag-bridged Ag{sub 2}O nanowire network/TiO{sub 2} nanotube array p–n heterojunction was fabricated by simple electrochemical method. The heterostructures exhibit high photocatalytic activity and excellent recycling performance. - Highlights: • Ag-bridged Ag{sub 2}O nanowire network self-stability structure. • Ag{sub 2}O nanowire network/TiO{sub 2} nanotube p–n heterojunction. • High visible light photocatalytic activity. • Highly stable recycling performance. - Abstract: A unique Ag-bridged Ag{sub 2}O nanowire network/TiO{sub 2} nanotube array p–n heterojunction (Ag–Ag{sub 2}O/TiO{sub 2} NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO{sub 2} NT and then were partly oxidized to Ag{sub 2}O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag{sub 2}O nanowire network. The Ag–Ag{sub 2}O/TiO{sub 2} NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag–Ag{sub 2}O self-stability structure and p–n heterojunction permitted high and stable photocatalytic activity of Ag–Ag{sub 2}O/TiO{sub 2} NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag–Ag{sub 2}O/TiO{sub 2} NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO{sub 2} NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag–Ag{sub 2}O/TiO{sub 2} NT remained highly stable photocatalytic activity.

  18. High efficiency and stable white OLED using a single emitter

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jian [Arizona State Univ., Tempe, AZ (United States). School of Mechanical, Aerospace, Chemical and Materials Engineering

    2016-01-18

    The ultimate objective of this project was to demonstrate an efficient and stable white OLED using a single emitter on a planar glass substrate. The focus of the project is on the development of efficient and stable square planar phosphorescent emitters and evaluation of such class of materials in the device settings. Key challenges included improving the emission efficiency of molecular dopants and excimers, controlling emission color of emitters and their excimers, and improving optical and electrical stability of emissive dopants. At the end of this research program, the PI has made enough progress to demonstrate the potential of excimer-based white OLED as a cost-effective solution for WOLED panel in the solid state lighting applications.

  19. Synthesis and Characterization of High Efficiency and Stable Spherical Ag3PO4 Visible Light Photocatalyst for the Degradation of Methylene Blue Solutions

    Directory of Open Access Journals (Sweden)

    Liqin Qin

    2015-01-01

    Full Text Available A facile method for the synthesis of Ag3PO4 visible light photocatalyst has been developed to improve the photocatalytic activity and stability. The as-prepared samples are investigated by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, photoluminescence (PL spectroscopy, and UV-Vis diffuse reflectance spectroscopy techniques. The results reveal that the prepared Ag3PO4 has cube structure with a band gap of 2.26 eV. The as-prepared samples show higher photocatalytic activity for methylene blue (MB degradation than that of N-TiO2 under visible light irradiation.

  20. Efficient quantum memory for light.

    Science.gov (United States)

    Hedges, Morgan P; Longdell, Jevon J; Li, Yongmin; Sellars, Matthew J

    2010-06-24

    Storing and retrieving a quantum state of light on demand, without corrupting the information it carries, is an important challenge in the field of quantum information processing. Classical measurement and reconstruction strategies for storing light must necessarily destroy quantum information as a consequence of the Heisenberg uncertainty principle. There has been significant effort directed towards the development of devices-so-called quantum memories-capable of avoiding this penalty. So far, successful demonstrations of non-classical storage and on-demand recall have used atomic vapours and have been limited to low efficiencies, of less than 17 per cent, using weak quantum states with an average photon number of around one. Here we report a low-noise, highly efficient (up to 69 per cent) quantum memory for light that uses a solid-state medium. The device allows the storage and recall of light more faithfully than is possible using a classical memory, for weak coherent states at the single-photon level through to bright states of up to 500 photons. For input coherent states containing on average 30 photons or fewer, the performance exceeded the no-cloning limit. This guaranteed that more information about the inputs was retrieved from the memory than was left behind or destroyed, a feature that will provide security in communications applications.

  1. Stable blue phosphorescent organic light emitting devices

    Science.gov (United States)

    Forrest, Stephen R.; Thompson, Mark; Giebink, Noel

    2014-08-26

    Novel combination of materials and device architectures for organic light emitting devices is provided. An organic light emitting device, is provided, having an anode, a cathode, and an emissive layer disposed between the anode and the cathode. The emissive layer includes a host and a phosphorescent emissive dopant having a peak emissive wavelength less than 500 nm, and a radiative phosphorescent lifetime less than 1 microsecond. Preferably, the phosphorescent emissive dopant includes a ligand having a carbazole group.

  2. Green synthesis of the reduced graphene oxide-CuI quasi-shell-core nanocomposite: A highly efficient and stable solar-light-induced catalyst for organic dye degradation in water

    Science.gov (United States)

    Choi, Jiha; Reddy, D. Amaranatha; Islam, M. Jahurul; Seo, Bora; Joo, Sang Hoon; Kim, Tae Kyu

    2015-12-01

    Surfactant-free, reduced graphene oxide (RGO)-CuI quasi-shell-core nanocomposites were successfully synthesized using ultra-sonication assisted chemical method at room temperature. The morphologies, structures and optical properties of the CuI and CuI-RGO nanocomposites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transformed infrared spectroscopy (FTIR), UV-visible absorption spectroscopy, and photoluminescence (PL) spectroscopy. Morphological and structural analyses indicated that the CuI-RGO core-shell nanocomposites comprise single-crystalline face-centered cubic phase CuI nanostructures, coated with a thin RGO quasi-shell. Photocatalysis experiments revealed that the as-synthesized CuI-RGO nanocomposites exhibit remarkably enhanced photocatalytic activities and stabilities for photo degradation of Rhodamine-B (RhB) organic dye under simulated solar light irradiation. The photo degradation ability is strongly affected by the concentration of RGO in the nanocomposites; the highest photodegradation rate was obtained at a graphene loading content of 2 mg mL-1 nanocomposite. The remarkable photocatalytic performance of the CuI-RGO nanocomposites mainly originates from their unique adsorption and electron-accepting and electron-transporting properties of RGO. The present work provides a novel green synthetic route to producing CuI-RGO nanocomposites without toxic solvents or reducing agents, thereby providing highly efficient and stable solar light-induced RGO-CuI quasi-shell-core nanocomposites for organic dye photo degradation in water.

  3. Energy Efficiency Through Lighting Upgrades

    Energy Technology Data Exchange (ETDEWEB)

    Berst, Kara [Chickasaw Nation, Ada, OK (United States); Howeth, Maria [Chickasaw Nation, Ada, OK (United States)

    2013-02-26

    Lighting upgrades including neon to LED, incandescent to CFL's and T-12 to T-8 and T-5's were completed through this grant. A total of 16 Chickasaw nation facilities decreased their carbon footprint because of these grant funds. Calculations used were based on comparing the energy usage from the previous year's average and the current energy usage. For facilities without a full year's set of energy bills, the month after installation was compared to the same month from the previous year. Overall, the effect the lighting change-outs had for the gaming centers and casinos far exceeded expectations. For the Madill Gaming Center; both an interior and exterior upgrade was performed which resulted in a 31% decrease in energy consumption. This same reduction was seen in every facility that participated in the grant. Just by simply changing out light bulbs to newer energy efficient equivalents, a decrease in energy usage can be achieved and this was validated by the return on investment seen at Chickasaw Nation facilities. Along with the technical project tasks were awareness sessions presented at Chickasaw Head Starts. The positive message of environmental stewardship was passed down to head start students and passed along to Chickasaw employees. Excitement was created in those that learned what they could do to help reduce their energy bills and many followed through and took the idea home. For a fairy low cost, the general public can also use this technique to lower their energy consumption both at home and at work. Although the idea behind the project was somewhat simple, true benefits have been gained through environmental awareness and reductions of energy costs.

  4. Efficient and stable extrapolation of prestack wavefields

    KAUST Repository

    Wu, Zedong

    2013-09-22

    The double-square-root (DSR) relation offers a platform to perform prestack imaging using an extended single wavefield that honors the geometrical configuration between sources, receivers and the image point, or in other words, prestack wavefields. Extrapolating such wavefields in time, nevertheless, is a big challenge because the radicand can be negative, thus reduce to a complex phase velocity, which will make the rank of the mixed domain matrix very high. Using the vertical offset between the sources and receivers, we introduce a method for deriving the DSR formulation, which gives us the opportunity to derive approximations for the mixed domain operator. The method extrapolates prestack wavefields by combining all data into one wave extrapolation procedure, allowing both upgoing and downgoing wavefields since the extrapolation is done in time, and doesn’t have the v(z) assumption in the offset axis of the media. Thus, the imaging condition is imposed by taking the zero-time and zero-offset slice from the multi-dimensional prestack wavefield. Unlike reverse time migration (RTM), no crosscorrelation is needed and we also have access to the subsurface offset information, which is important for migration velocity analysis. Numerical examples show the capability of this approach in dealing with complex velocity models and can provide a better quality image compared to RTM more efficiently.

  5. INTELLIGENT LIGHTING SYSTEM WITH ENERGY EFFICIENCY

    OpenAIRE

    Neha Patil*, Prof .A .C .Wani

    2016-01-01

    This paper describes Intelligent Lighting System to reduce energy consumption in lighting system. Now days’ saving energy is the most important issue, so many light control systems have been initiated in current market. But due to some designing limitations and energy inefficiency, the existing light control systems cannot be successfully installed in home and office buildings with energy efficiency and user satisfaction. This system uses motion, light sensors and wireless communication techn...

  6. Improvement in light-extraction efficiency of light emitting diode ...

    Indian Academy of Sciences (India)

    The effect of various microlens parameters such as diameter and area fraction on light-extraction efficiency was systematically studied. Improvement of 4% in extraction efficiency was obtained by employing it on white light emitting diode. The area fraction of microlenses was increased up to 0.34 by reducing the spin speed.

  7. Improvement in light-extraction efficiency of light emitting diode ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... parameters such as diameter and area fraction on light-extraction efficiency was systematically studied. Improvement of. 4% in extraction efficiency was obtained by employing it on white light emitting diode. The area fraction .... on feature size due to (i) weak van der Waals destabilizing forces and (ii) high ...

  8. Energy efficient lighting in the retail sector

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    This Good Practice Guide gives details on how energy efficient lighting can be incorporated in the brief for a lighting consultant or contractor. The advantages of energy efficiency are highlighted, and the lighting of retail stores, the introduction of energy efficiency measures, and the application of good practice are discussed. Case studies of W H Smith, Cambridge, Tesco Stores, Boots plc, the Harvey Centre, Harlow, and the National Westminster Bank plc are presented. A guide for senior executives and specialists in lighting design is also included. (UK)

  9. Light's labour's lost - policies for energy-efficient lighting

    International Nuclear Information System (INIS)

    2006-01-01

    When William Shakepeare wrote Love's Labour's Lost he would have used light from tallow candles at a cost (today) of 12,000 British pounds per million-lumen hours. The same amount of light from electric lamps now costs only 2 pounds. But today's low-cost illumination still has a dark side. Globally, lighting consumes more electricity than is produced by either hydro or nuclear power and results in CO2 emissions equivalent to two thirds of the world's cars. A standard incandescent lamp may be much more efficient than a tallow candle, but it is far less efficient than a high-pressure sodium lamp. Were inefficient light sources to be replaced by the equivalent efficient ones, global lighting energy demand would be up to 40% less at a lower overall cost. Larger savings still could be realised through the intelligent use of controls, lighting levels and daylight. But achieving efficient lighting is not just a question of technology; it requires policies to transform current practice. This book documents the broad range of policy measures to stimulate efficient lighting that have already been implemented around the world and suggests new ways these could be strengthened to prevent light's labour's from being lost

  10. Efficiency of subaquatic light traps

    Czech Academy of Sciences Publication Activity Database

    Ditrich, Tomáš; Čihák, P.

    2017-01-01

    Roč. 38, č. 3 (2017), s. 171-184 ISSN 0165-0424 R&D Projects: GA ČR(CZ) GA14-29857S Institutional support: RVO:60077344 Keywords : Heteroptera * Diptera * light trap Subject RIV: EH - Ecology, Behaviour OBOR OECD: Ecology Impact factor: 0.524, year: 2016

  11. Improvement in light-extraction efficiency of light emitting diode ...

    Indian Academy of Sciences (India)

    ) to obtain the microlenses. Dimension of these microlenses was measured to be the order of 1–2 μ m. The effect of various microlens parameters such as diameter and area fraction on light-extraction efficiency was systematically studied.

  12. Green Lighting. Energy-efficient integrated lighting systems - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Linhart, F.; Scartezzini, J.-L.

    2009-10-15

    The objective of the Green Lighting project was to develop a High Performance Integrated Lighting System, based on advanced technologies for day- and electric lighting, achieving a Lighting Power Density (LPD) that does not exceed 3 W/m{sup 2}. The project has revealed that Anidolic Daylighting Systems (ADS) are an ideal basis for High Performance Integrated Lighting Systems. Not only are they able to provide adequate illumination (i.e. sufficiently high illuminance) in office rooms during large fractions of normal office hours, under various sky conditions and over the entire year, but they are also highly appreciated by office occupants at the condition that glare control mechanisms are available. Complementary electric lighting is, however, still necessary to back up the ADS at times when there is insufficient daylight flux available. It was shown during this project, that the most interesting trade-offs between energy-efficiency and visual comfort are obtained by using a combination of ceiling-mounted directly emitting luminaires with very high optical efficiencies for ambient lighting and portable desk lamps for temporary task lighting. The most appropriate lamps for the ceiling-mounted luminaires are currently highly efficient fluorescent tubes, but white LED tubes can be considered a realistic option for the future. The most suitable light sources for desk lamps for temporary task lighting are Compact Fluorescent Lamps (CFLs) and white LED light bulbs. Based on the above-mentioned technologies, a High Performance Integrated Lighting System with a very low LPD has been developed over the last three years. The system has been set up in an office room of the LESO solar experimental building located on the EPFL campus; it has been tested intensively during a Post-Occupancy Evaluation (POE) study involving twenty human subjects. This study has revealed that the subjects' performance and subjective visual comfort was improved by the new system, compared to

  13. Household transitions to energy efficient lighting

    International Nuclear Information System (INIS)

    Mills, Bradford; Schleich, Joachim

    2014-01-01

    New energy efficient lighting technologies can significantly reduce household electricity consumption, but adoption has been slow. A unique dataset of German households is used in this paper to examine the factors associated with the replacement of old incandescent lamps (ILs) with new energy efficient compact fluorescent lamps (CFLs) and light emitting diodes (LEDs). The ‘rebound’ effect of increased lamp luminosity in the transition to energy efficient bulbs is analyzed jointly with the replacement decision to account for household self-selection in bulb-type choice. Results indicate that the EU ban on ILs accelerated the pace of transition to CFLs and LEDs, while storage of bulbs significantly dampened the speed of the transition. Higher lighting needs and bulb attributes like energy efficiency, environmental friendliness, and durability spur IL replacement with CFLs or LEDs. Electricity gains from new energy efficient lighting are mitigated by 23% and 47% increases in luminosity for CFL and LED replacements, respectively. Model results suggest that taking the replacement bulb from storage and higher levels of education dampen the magnitude of these luminosity rebounds in IL to CFL transitions. - Highlights: • EU ban on ILs has fostered transitions to energy efficient lighting • Energy efficient, environmentally friendly, and durable lighting preferences make CFL and LED transitions more likely • Indicators of greater lighting needs are associated with higher propensities to replace ILs with CFLs and LEDs • For residential lighting, the rebound effect manifests itself through increases in luminosity • In IL to CLF transitions luminosity increases are lower with higher levels of education

  14. High Quantum Efficiency OLED Lighting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Shiang, Joseph [General Electric (GE) Global Research, Fairfield, CT (United States)

    2011-09-30

    The overall goal of the program was to apply improvements in light outcoupling technology to a practical large area plastic luminaire, and thus enable the product vision of an extremely thin form factor high efficiency large area light source. The target substrate was plastic and the baseline device was operating at 35 LPW at the start of the program. The target LPW of the program was a >2x improvement in the LPW efficacy and the overall amount of light to be delivered was relatively high 900 lumens. Despite the extremely difficult challenges associated with scaling up a wet solution process on plastic substrates, the program was able to make substantial progress. A small molecule wet solution process was successfully implemented on plastic substrates with almost no loss in efficiency in transitioning from the laboratory scale glass to large area plastic substrates. By transitioning to a small molecule based process, the LPW entitlement increased from 35 LPW to 60 LPW. A further 10% improvement in outcoupling efficiency was demonstrated via the use of a highly reflecting cathode, which reduced absorptive loss in the OLED device. The calculated potential improvement in some cases is even larger, ~30%, and thus there is considerable room for optimism in improving the net light coupling efficacy, provided absorptive loss mechanisms are eliminated. Further improvements are possible if scattering schemes such as the silver nanowire based hard coat structure are fully developed. The wet coating processes were successfully scaled to large area plastic substrate and resulted in the construction of a 900 lumens luminaire device.

  15. An Efficient Approach for Identifying Stable Lobes with Discretization Method

    Directory of Open Access Journals (Sweden)

    Baohai Wu

    2013-01-01

    Full Text Available This paper presents a new approach for quick identification of chatter stability lobes with discretization method. Firstly, three different kinds of stability regions are defined: absolute stable region, valid region, and invalid region. Secondly, while identifying the chatter stability lobes, three different regions within the chatter stability lobes are identified with relatively large time intervals. Thirdly, stability boundary within the valid regions is finely calculated to get exact chatter stability lobes. The proposed method only needs to test a small portion of spindle speed and cutting depth set; about 89% computation time is savedcompared with full discretization method. It spends only about10 minutes to get exact chatter stability lobes. Since, based on discretization method, the proposed method can be used for different immersion cutting including low immersion cutting process, the proposed method can be directly implemented in the workshop to promote machining parameters selection efficiency.

  16. Analysis of energy efficient highway lighting retrofits.

    Science.gov (United States)

    2015-06-01

    Solid state lighting technology is advancing rapidly to a point where light emitting diode (LED) lighting : systems can be viable replacements for existing lighting systems using high pressure sodium (HPS). The : present report summarizes analyses co...

  17. Photosynthetic efficiency of Chlamydomonas reinhardtii in flashing light

    NARCIS (Netherlands)

    Vejrazka, C.; Janssen, M.G.J.; Streefland, M.; Wijffels, R.H.

    2011-01-01

    Efficient light to biomass conversion in photobioreactors is crucial for economically feasible microalgae production processes. It has been suggested that photosynthesis is enhanced in short light path photobioreactors by mixing-induced flashing light regimes. In this study, photosynthetic

  18. Color stable white phosphorescent organic light emitting diodes with red emissive electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Eun Lee, Song; Kwan Kim, Young [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Hwa Yu, Hyeong; Turak, Ayse [Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Young Kim, Woo, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)

    2015-06-28

    We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){sub 3} as phosphorescent red dopant in electron transport layer.

  19. Calibration of school spectrometer for measuring light bulb efficiency

    OpenAIRE

    Valenčič, Matej

    2015-01-01

    This diploma thesis presents the efficiency of various light sources which are used for lighting on a daily basis (incandescent light bulb, halogen lamp, compact fluorescent lamp, light-emiting diode). The theoretical part of the thesis presents the instruments used for measurements, the physical laws used in order to calculate the efficiency of each light source and the physical background needed for the understanding of further calculations. The experimental part of the thesis presents the ...

  20. Highly stable cesium lead iodide perovskite quantum dot light-emitting diodes

    Science.gov (United States)

    Zou, Chen; Huang, Chun-Ying; Sanehira, Erin M.; Luther, Joseph M.; Lin, Lih Y.

    2017-11-01

    Recently, all-inorganic perovskites such as CsPbBr3 and CsPbI3, have emerged as promising materials for light-emitting applications. While encouraging performance has been demonstrated, the stability issue of the red-emitting CsPbI3 is still a major concern due to its small tolerance factor. Here we report a highly stable CsPbI3 quantum dot (QD) light-emitting diode (LED) with red emission fabricated using an improved purification approach. The device achieved decent external quantum efficiency (EQE) of 0.21% at a bias of 6 V and outstanding operational stability, with a L 70 lifetime (EL intensity decreases to 70% of starting value) of 16 h and 1.5 h under a constant driving voltage of 5 V and 6 V (maximum EQE operation) respectively. Furthermore, the device can work under a higher voltage of 7 V (maximum luminance operation) and retain 50% of its initial EL intensity after 500 s. These findings demonstrate the promise of CsPbI3 QDs for stable red LEDs, and suggest the feasibility for electrically pumped perovskite lasers with further device optimizations.

  1. Stable and efficient Light-Emitting Electrochemical Cells

    OpenAIRE

    Tordera Salvador, Daniel

    2014-01-01

    La evolución de la tecnología exige el diseño de nuevas pantallas y sis-temas de iluminación. En este marco se necesitan rendimientos mejores y diseños avanzados y novedosos de productos. Los diodos orgánicos emisores de luz (OLEDs) son una alternativa factible a los sistemas inorgánicos debido a sus propiedades físicas únicas. Se pueden preparar dispositivos muy finos que pueden ser procesados a temperatura ambiente en sustratos grandes y flexibles. Además, sus propiedades se pueden ajustar ...

  2. Discrimination of ginseng cultivation regions using light stable isotope analysis.

    Science.gov (United States)

    Kim, Kiwook; Song, Joo-Hyun; Heo, Sang-Cheol; Lee, Jin-Hee; Jung, In-Woo; Min, Ji-Sook

    2015-10-01

    Korean ginseng is considered to be a precious health food in Asia. Today, thieves frequently compromise ginseng farms by pervasive theft. Thus, studies regarding the characteristics of ginseng according to growth region are required in order to deter ginseng thieves and prevent theft. In this study, 6 regions were selected on the basis of Korea regional criteria (si, gun, gu), and two ginseng-farms were randomly selected from each of the 6 regions. Then 4-6 samples of ginseng were acquired from each ginseng farm. The stable isotopic compositions of H, O, C, and N of the collected ginseng samples were analyzed. As a result, differences in the hydrogen isotope ratios could be used to distinguish regional differences, and differences in the nitrogen isotope ratios yielded characteristic information regarding the farms from which the samples were obtained. Thus, stable isotope values could be used to differentiate samples according to regional differences. Therefore, stable isotope analysis serves as a powerful tool to discriminate the regional origin of Korean ginseng samples from across Korea. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  3. Energy Efficient LED Spectrally Matched Smart Lighting, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Innovative Imaging and Research has teamed with the University of Southern Mississippi to develop a novel energy efficient smart light system. Smart lighting adds an...

  4. High extraction efficiency ultraviolet light-emitting diode

    Science.gov (United States)

    Wierer, Jonathan; Montano, Ines; Allerman, Andrew A.

    2015-11-24

    Ultraviolet light-emitting diodes with tailored AlGaN quantum wells can achieve high extraction efficiency. For efficient bottom light extraction, parallel polarized light is preferred, because it propagates predominately perpendicular to the QW plane and into the typical and more efficient light escape cones. This is favored over perpendicular polarized light that propagates along the QW plane which requires multiple, lossy bounces before extraction. The thickness and carrier density of AlGaN QW layers have a strong influence on the valence subband structure, and the resulting optical polarization and light extraction of ultraviolet light-emitting diodes. At Al>0.3, thinner QW layers (light preferentially polarized parallel to the QW plane. Also, active regions consisting of six or more QWs, to reduce carrier density, and with thin barriers, to efficiently inject carriers in all the QWs, are preferred.

  5. Efficient and facile synthesis of novel stable monodeuterium labeled ractopamine.

    Science.gov (United States)

    Su, Feifei; Wu, Fulong; Tang, He; Wang, Zhonghua; Wu, Fanhong

    2015-01-01

    A novel synthetic route to stable deuterium labeled ractopamine was disclosed with 6.49% total yield and 97.7% isotopic abundance. Its structure and the isotope-abundance were confirmed according to (1)H-NMR and high-resolution mass spectrometry. Copyright © 2015 John Wiley & Sons, Ltd.

  6. Insights from stable light isotopes on enamel defects and weaning in ...

    Indian Academy of Sciences (India)

    Unknown

    reiterates the value of stable isotope analyses in determining both the behaviour of fossil animals and the environmental conditions that prevailed during tooth development. [Franz-Odendaal T A, Lee-Thorp J A and Chinsamy A 2003 Insights from stable light isotopes on enamel defects and weaning in Pliocene herbivores ...

  7. Efficient Thermally Stable Spectral Control Filters for Thermophotovoltaics, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The feasibility of radioisotope thermophotovoltaic (RTPV) power systems has been shown. The best efficiencies reported to date for a TPV module test include front...

  8. Improvement in light-extraction efficiency of light emitting diode ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... ranging from 20 to 40 nm. Then, this PS film was kept in dewetting solution namely methylethylketone (MEK) to obtain the microlenses. Dimension of these microlenses was measured to be the order of 1–2 μm. The effect of various microlens parameters such as diameter and area fraction on light-extraction ...

  9. Energy efficient lighting design for Venlo type greenhouses

    NARCIS (Netherlands)

    Janssen, E.G.O.N.; Zonneveldt, L.; Sools, F.

    2005-01-01

    TNO has developed a Radiance software model to calculate the light distribution in the greenhouse using raytracing methods, suitable for daylight and artificial lighting. The model is based on a 3d CAD model. The objective is to maximize the efficiency of the artificial lighting system (the amount

  10. Efficient organic light emitting-diodes (OLEDs)

    CERN Document Server

    Chang, Yi-Lu

    2015-01-01

    Following two decades of intense research globally, the organic light-emitting diode (OLED) has steadily emerged as the ultimate display technology of choice for the coming decades. Portable active matrix OLED displays have already become prevalent, and even large-sized ultra-high definition 4K TVs are being mass-produced. More exotic applications such as wearable displays have been commercialized recently. With the burgeoning success in displays, researchers are actively bringing the technology forward into the exciting solid-state lighting market. This book presents the knowledge needed for

  11. Highly efficient and stable catalyst for peroxynitrite decomposition

    Science.gov (United States)

    Yurii V. Geletii; Alan J. Bailey; Jennifer J. Cowan; Ira A. Weinstock; Craig L. Hill

    2001-01-01

    The new cobalt substituted-polyoxometalate K7[CoAlW11O39]•15H2O and the simple CoCl2•6H2O salt are efficient catalysts for peroxynitrite decomposition. These compounds also catalyze the oxidation of ascorbic acid and the nitration of phenol by peroxynitrite.

  12. Assessment of photobiological safety of energy-efficiency urban lighting

    Directory of Open Access Journals (Sweden)

    Łukasz Stanisław Pierzchała

    2018-02-01

    Full Text Available Exceeding the safe threshold for exposure on high energy radiation (UV and blue light could cause the emergence of a number of diseases. Eyesight is particularly sensitive to excessive lighting. This paper presents the laboratory research on the assessment of the photobiological risk generated by the energy-efficiency urban lighting. The results show that LED lighting systems can be a source of radiation that significantly negatively affects the eyesight and could contribute to circadian rhythm disorders.

  13. Stable and Efficient Advanced Oxygen Reduction Alloy Catalysts for PEM Fuel Cells Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Human exploration of space demands highly efficient, light-weight, long lifetime and maintenance-free power generation systems. Energy storage applications,...

  14. Stable and Efficient Advanced Oxygen Reduction Alloy Catalysts for PEM Fuel Cells, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Human exploration of space demands highly efficient, light-weight, long lifetime and maintenance-free power generation systems. Energy storage applications,...

  15. Towards low cost, efficient and stable organic photovoltaic modules

    Energy Technology Data Exchange (ETDEWEB)

    Andriessen, R. [Holst Centre - Solliance, PO Box 8550, 5605 KN Eindhoven (Netherlands); Kroon, J.M. [ECN - Solliance, Petten (Netherlands); Aernouts, T. [Imec, Solliance, Kapeldreef 75, B-3001 Leuven (Belgium); Janssen, R. [Eindhoven University of Technology, Solliance, Eindhoven (Netherlands)

    2012-09-15

    This article describes how the Solliance Organic PhotoVoltaics (OPV) shared research Program addresses efficiency, lifetime and production costs for (near) future OPV applications. The balance of these three parameters depends of the envisaged application, but at the end, OPV should be able to compete somehow with Si PV in the future. Efficiency improvements are realized by developing new materials, by exploring and optimizing new device structures and novel interconnection technologies. Lifetime improvements are realized by using stabilized device stacks and materials and by applying high end flexible barriers. Production cost control is done by using a home made Cost of Ownership tool which guides towards the use of low-cost materials and processes.

  16. AgBr/diatomite for the efficient visible-light-driven photocatalytic degradation of Rhodamine B

    Science.gov (United States)

    Fang, Jing; Zhao, Huamei; Liu, Qinglei; Zhang, Wang; Gu, Jiajun; Su, Yishi; Abbas, Waseem; Su, Huilan; You, Zhengwei; Zhang, Di

    2018-03-01

    The treatment of organic pollution via photocatalysis has been investigated for a few decades. However, earth-abundant, cheap, stable, and efficient substrates are still to be developed. Here, we prepare an efficient visible-light-driven photocatalyst via the deposition of Ag nanoparticles (nanoparticles (nanoparticles ( κ = 0.05 min-1) were measured as well. The experimental results reveal that diatomite acted more than a substrate benefiting the dispersion of AgBr nanoparticles, as well as a cooperator to help harvest visible light and adsorb dye molecules, leading to the efficient visible-light-driven photocatalytic performance of AgBr/diatomite. Considering the low cost (10 per ton) and large-scale availability of diatomite, our study provides the possibility to prepare other types of diatomite-based efficient photocatalytic composites with low-cost but excellent photocatalytic performance.

  17. Synthesis and characterization of highly efficient and stable Pr6O11/Ag3PO4/Pt ternary hybrid structure

    International Nuclear Information System (INIS)

    Deng, Jiatao; Liu, Lin; Niu, Tongjun; Sun, Xiaosong

    2017-01-01

    Highlights: • Visible-light-driven Pr 6 O 11 /Ag 3 PO 4 /Pt photocatalysts were prepared. • Pr 6 O 11 /Ag 3 PO 4 /Pt showed highly efficient and stable photocatalystic activity. • The photocatalytic mechanism of Pr 6 O 11 /Ag 3 PO 4 /Pt composite was given. - Abstract: Ag 3 PO 4 is an excellent photocatalyst with high efficiency and quantum yield, but suffers from the fast recombination of photogenerated electron-hole pairs and photo-corrosion. Hereby, the highly efficient and stable visible-light-driven Pr 6 O 11 /Ag 3 PO 4 /Pt photocatalyst were prepared via a three-step wet chemical approach. The as-prepared Pr 6 O 11 /Ag 3 PO 4 /Pt composite was characterized by X-ray diffraction, US-vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra and transient photocurrent as well. Comparing with single Pr 6 O 11 or Ag 3 PO 4 , the prepared Pr 6 O 11 /Ag 3 PO 4 /Pt composite exhibited much higher photocatalytic activity and stability for the degradation of Rhodamine B under visible light irradiation (>420 nm). The enhanced photocatalytic performance of Pr 6 O 11 /Ag 3 PO 4 /Pt composite has been attributed to the efficient separation of photo-generated electron-hole pairs through a scheme system composed of Pr 6 O 11, Ag 3 PO 4 and Pt.

  18. Designing high efficient solar powered lighting systems

    DEFF Research Database (Denmark)

    Poulsen, Peter Behrensdorff; Thorsteinsson, Sune; Lindén, Johannes

    2016-01-01

    Some major challenges in the development of L2L products is the lack of efficient converter electronics, modelling tools for dimensioning and furthermore, characterization facilities to support the successful development of the products. We report the development of 2 Three-Port-Converters respec......Some major challenges in the development of L2L products is the lack of efficient converter electronics, modelling tools for dimensioning and furthermore, characterization facilities to support the successful development of the products. We report the development of 2 Three-Port......-Converters respectively for 1-10Wp and 10-50 Wp with a peak efficiency of 97% at 1.8 W of PV power for the 10 Wp version. Furthermore, a modelling tool for L2L products has been developed and a laboratory for feeding in component data not available in the datasheets to the model is described....

  19. High efficiency lighting: Cost benefit analysis

    Energy Technology Data Exchange (ETDEWEB)

    Di Franco, N. (ENEA, Rome (Italy))

    1992-12-01

    Analysis of the incandescent and fluorescent lamp market in Italy reveals that, by the substitution of conventional equipment with high efficiency lamps, energy savings of up to 3.5 billion kWh could be realized. However, the proper selection of these highly efficient lamps, e.g., compact fluorescent, fluorescent systems using electronic reactors, outdoor systems using sodium or metal iodides, etc., requires a thorough and accurate cost benefit analysis. This article suggests a calculation model for a cost evaluation beginning from the technical and economic aspects of alternative appliances.

  20. Designing high efficient solar powered lighting systems

    DEFF Research Database (Denmark)

    Poulsen, Peter Behrensdorff; Thorsteinsson, Sune; Lindén, Johannes

    2016-01-01

    -Port-Converters respectively for 1-10Wp and 10-50 Wp with a peak efficiency of 97% at 1.8 W of PV power for the 10 Wp version. Furthermore, a modelling tool for L2L products has been developed and a laboratory for feeding in component data not available in the datasheets to the model is described....

  1. Efficient and stable perfectly matched layer for CEM

    KAUST Repository

    Duru, Kenneth

    2014-02-01

    An efficient unsplit perfectly matched layer for numerical simulation of electromagnetic waves in unbounded domains is derived via a complex change of variables. In order to surround a Cartesian grid with the PML, the time-dependent PML requires only one (scalar) auxiliary variable in two space dimensions and six (scalar) auxiliary variables in three space dimensions. It is therefore cheap and straightforward to implement. We use Fourier and energy methods to prove the stability of the PML. We extend the stability result to a semi-discrete PML approximated by central finite differences of arbitrary order of accuracy and to a fully discrete problem for the \\'Leap-Frog\\' schemes. This makes precise the usefulness of the derived PML model for longtime simulations. Numerical experiments are presented, illustrating the accuracy and stability of the PML. © 2013 IMACS.

  2. Energy Efficient LED Spectrally Matched Smart Lighting, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Innovative Imaging and Research and the University of Houston Clear Lake have teamed to develop a widely extensible, affordable, energy efficient, smart lighting...

  3. High Efficiency Lighting with Integrated Adaptive Control (HELIAC), Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed project is the continued development of the High Efficiency Lighting with Integrated Adaptive Control (HELIAC) system. Solar radiation is not a viable...

  4. High Efficiency Lighting with Integrated Adaptive Control (HELIAC), Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The innovation of the proposed project is the development of High Efficiency Lighting with Integrated Adaptive Control (HELIAC) systems to drive plant growth. Solar...

  5. Two-phase cooling of light emitting diode for higher light output and increased efficiency

    NARCIS (Netherlands)

    Ye, H.; Mihailovic, M.; Wong, C.K.Y.; Zeijl, H.W. van; Gielen, A.W.J.; Zhang, G.Q.; Sarro, P.M.

    2013-01-01

    High Power Light Emitting Diode (HP LED) is one of the promising candidates for future lighting systems with efficient energy consumption. However, around 70% of the input power will be still transferred to heat. Recently, to obtain more light output, the increased electrical currents consequently

  6. Light extraction efficiency enhancement for fluorescent SiC based white light-emitting diodes

    DEFF Research Database (Denmark)

    Ou, Haiyan; Ou, Yiyu; Argyraki, Aikaterini

    Fluorescent SiC based white light-emitting diodes(LEDs) light source, as an innovative energy-efficient light source, would even have longer lifetime, better light quality and eliminated blue-tone effect, compared to the current phosphor based white LED light source. In this paper, the yellow....... At a device level, the focus is on improving the light extraction efficiency due to the rather high refractive index of SiC by nanostructuring the surface of SiC. Both periodic nanostructures made by e-beam lithography and nanosphere lithography and random nanostructures made by self-assembled Au nanosphere...... mask and a thin layer of Al film have been investigated and all of them showed much enhanced extraction efficiency. All these good results pave the way to a very promising fluorescent SiC based white LED light source...

  7. Energy efficient lighting design for Venlo type greenhouses

    NARCIS (Netherlands)

    Janssen, E.; Zonneveldt, L.; Sools, F.

    2006-01-01

    TNO has developed a Radiance software model to calculate the light distribution in the greenhouse using raytracing methods, suitable for daylight and artificial lighting. The model is based on a 3D CAD (Computer aided design) model. The objective is to maximize the efficiency of the artificial

  8. Thermally stable aromatic amine derivative with symmetrically substituted double spirobifluorene core as a hole transport material for green phosphorescent organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Yong Joo; Lee, Jun Yeob, E-mail: leej17@dankook.ac.kr

    2012-11-01

    A thermally stable aromatic amine derivative with a symmetrically substituted double spirobifluorene core was synthesized as a hole transport material for green phosphorescent organic light-emitting diodes. A high glass transition temperature of 142 Degree-Sign C was obtained and a film morphology of the hole transport material was kept stable up to 120 Degree-Sign C. The hole transport material showed a high triplet energy of 2.53 eV and a quantum efficiency of 17.4% in green phosphorescent organic light-emitting diodes. - Highlights: Black-Right-Pointing-Pointer Synthesis of symmetrically substituted double spirobifluorene core Black-Right-Pointing-Pointer Stable film morphology up to 120 Degree-Sign C Black-Right-Pointing-Pointer High quantum efficiency in green phosphorescent organic light emitting diode.

  9. Light quality and efficiency of consumer grade solid state lighting products

    DEFF Research Database (Denmark)

    Dam-Hansen, Carsten; Corell, Dennis Dan; Thorseth, Anders

    2013-01-01

    The rapid development in flux and efficiency of Light Emitting Diodes (LED) has resulted in a flooding of the lighting market with Solid State Lighting (SSL) products. Many traditional light sources can advantageously be replaced by SSL products. There are, however, large variations in the quality...... of these products, and some are not better than the ones they are supposed to replace. A lack of quality demands and standards makes it difficult for consumers to get an overview of the SSL products. Here the results of a two year study investigating SSL products on the Danish market are presented. Focus has been...... on SSL products for replacement of incandescent lamps and halogen spotlights. The warm white light and good color rendering properties of these traditional light sources are a must for lighting in Denmark and the Nordic countries. 266 SSL replacement lamps have been tested for efficiency and light...

  10. Maximizing Light Utilization Efficiency and Hydrogen Production in Microalgal Cultures

    Energy Technology Data Exchange (ETDEWEB)

    Melis, Anastasios [Univ. of California, Berkeley, CA (United States)

    2014-12-31

    The project addressed the following technical barrier from the Biological Hydrogen Production section of the Fuel Cell Technologies Program Multi-Year Research, Development and Demonstration Plan: Low Sunlight Utilization Efficiency in Photobiological Hydrogen Production is due to a Large Photosystem Chlorophyll Antenna Size in Photosynthetic Microorganisms (Barrier AN: Light Utilization Efficiency).

  11. Highly efficient light management for perovskite solar cells

    Science.gov (United States)

    Wang, Dong-Lin; Cui, Hui-Juan; Hou, Guo-Jiao; Zhu, Zhen-Gang; Yan, Qing-Bo; Su, Gang

    2016-01-01

    Organic-inorganic halide perovskite solar cells have enormous potential to impact the existing photovoltaic industry. As realizing a higher conversion efficiency of the solar cell is still the most crucial task, a great number of schemes were proposed to minimize the carrier loss by optimizing the electrical properties of the perovskite solar cells. Here, we focus on another significant aspect that is to minimize the light loss by optimizing the light management to gain a high efficiency for perovskite solar cells. In our scheme, the slotted and inverted prism structured SiO2 layers are adopted to trap more light into the solar cells, and a better transparent conducting oxide layer is employed to reduce the parasitic absorption. For such an implementation, the efficiency and the serviceable angle of the perovskite solar cell can be promoted impressively. This proposal would shed new light on developing the high-performance perovskite solar cells. PMID:26733112

  12. The cucumber long hypocotyl mutant lacks a light-stable PHYB-like phytochrome.

    Science.gov (United States)

    López-Juez, E; Nagatani, A; Tomizawa, K; Deak, M; Kern, R; Kendrick, R E; Furuya, M

    1992-01-01

    A novel cDNA sequence homologous to a phytochrome B (phyB) gene that was isolated in a library from tobacco tissue has been used in an Escherichia coli expression system to raise anti-phytochrome B (anti-PHYB) polypeptide-specific monoclonal antibodies. The specificity of these antibodies has been tested by cross-reactivity against purified pea light-labile type 1 and light-stable type 2 phytochromes, with some antibodies reacting with the type 2 and none with the type 1 phytochromes. One such antibody, monoclonal mAT1, has been employed to analyze the phytochrome molecular species present in a photomorphogenic long hypocotyl (lh) mutant of cucumber. The results indicated that the mutant contains wild-type levels of the light-labile type 1 phytochrome polypeptide (PHYA), which has an apparent molecular mass of approximately 120 kD, but shows less than 1% (detection limit) of a light-stable polypeptide recognized by mAT1 in wild-type seedlings. This protein, not detectable in the lh mutant, has the properties of light-stable type 2 phytochrome, has an apparent molecular mass of 116 to 117 kD, and remains at constant levels under continuous low-fluence-rate red light. Therefore, we conclude that the lh mutant lacks at least one type 2 phytochrome-like polypeptide, most probably a phyB gene product. The correlation between the lack of this protein and the deficiency or absence of physiological responses to a light-stable phytochrome species in this mutant helps to identify the physiological roles played by the products of different subfamilies within the phytochrome gene family. PMID:1498594

  13. Evaluation and Improvement of Lighting Efficiency in Working Spaces

    Directory of Open Access Journals (Sweden)

    Ana Castillo-Martinez

    2018-04-01

    Full Text Available Lighting is an essential element for modern life, promoting a sense of wellbeing for users. However, bad illumination may produce health problems such as headaches and fatigue, among other vision problems. For that reason, this paper proposes the development of a smartphone-based application to help in lighting evaluation to guarantee the compliance of illumination regulations and to help increase illuminance efficiency, reducing its energy consumption. To perform this evaluation, the smartphone can be used as a lighting measurement tool, evaluating those measurements through an intelligent agent based in rules capable of guiding the decision-making process. As a result, this tool allows the evaluation of the real working environment to guarantee lighting requirements, helping in the prevention of health problems derived from bad illumination and improving the lighting efficiency at the same time.

  14. Improvement of light-extraction efficiency of organic light-emitting diodes using dielectric nanoparticles

    Science.gov (United States)

    Mann, Vidhi; Hooda, Babita; Rastogi, Vipul

    2017-07-01

    Use of dielectric nanoparticles placed at the anode (indium tin oxide) for the improvement of light-extraction efficiency of an organic light-emitting diode (OLED) has been reported. The nanoparticle layer will act as a scattering medium for the light trapped in the waveguiding modes of the device. Mie theory has been applied to study the scattering efficiency of the isolated dielectric nanoparticle. The effect of dielectric nanoparticles on the light-extraction efficiency of OLED has been analyzed by the finite-difference time-domain method. The light-extraction efficiency of the device depends upon the diameter, interparticle separation, and refractive index of dielectric nanoparticles. At optimal nanoparticle parameters, the enhancement factor of 1.7 times is obtained with the proposed design.

  15. The efficiency challenge of nitride light-emitting diodes for lighting

    KAUST Repository

    Weisbuch, Claude

    2015-03-13

    © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. We discuss the challenges of light-emitting diodes in view of their application to solid-state lighting. The requirement is to at least displace the quite efficient fluorescent, sodium, and high intensity discharge lamps used today in the main energy consuming lighting sectors, industrial, commercial and outdoors, with more efficient and better light quality lamps. We show that both from the point of view of cost of ownership and carbon emissions reduction, the relevant metric is efficiency, more than the cost of lumens. Then, progress from present performance requires identification of the loss mechanisms in light emission from LEDs, and solutions competing with mainstream c-plane LEDS grown on sapphire need to be on par with these. Special attention is devoted to a discussion of the efficiency droop mechanisms, and of a recent direct measurement of Auger generated electrons which appear to be responsible for droop.

  16. Light's labour's lost - policies for energy-efficient lighting

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-06-29

    When William Shakepeare wrote Love's Labour's Lost he would have used light from tallow candles at a cost (today) of 12,000 British pounds per million-lumen hours. The same amount of light from electric lamps now costs only 2 pounds! But today's low-cost illumination still has a dark side. Globally, lighting consumes more electricity than is produced by either hydro or nuclear power and results in CO2 emissions equivalent to two thirds of the world's cars. A standard incandescent lamp may be much more efficient than a tallow candle, but it is far less efficient than a high-pressure sodium lamp. Were inefficient light sources to be replaced by the equivalent efficient ones, global lighting energy demand would be up to 40% less at a lower overall cost. Larger savings still could be realised through the intelligent use of controls, lighting levels and daylight. But achieving efficient lighting is not just a question of technology; it requires policies to transform current practice. This book documents the broad range of policy measures to stimulate efficient lighting that have already been implemented around the world and suggests new ways these could be strengthened to prevent light's labour's from being lost.

  17. Light increases energy transfer efficiency in a boreal stream.

    Science.gov (United States)

    Lesutienė, Jūratė; Gorokhova, Elena; Stankevičienė, Daiva; Bergman, Eva; Greenberg, Larry

    2014-01-01

    Periphyton communities of a boreal stream were exposed to different light and nutrient levels to estimate energy transfer efficiency from primary to secondary producers using labeling with inorganic (13)C. In a one-day field experiment, periphyton grown in fast-flow conditions and dominated by opportunistic green algae were exposed to light levels corresponding to sub-saturating (forest shade) and saturating (open stream section) irradiances, and to N and P nutrient additions. In a two-week laboratory experiment, periphyton grown in low-flow conditions and dominated by slowly growing diatoms were incubated under two sub-saturating light and nutrient enrichment levels as well as grazed and non-grazed conditions. Light had significant positive effect on (13)C uptake by periphyton. In the field experiment, P addition had a positive effect on (13)C uptake but only at sub-saturating light levels, whereas in the laboratory experiment nutrient additions had no effect on the periphyton biomass, (13)C uptake, biovolume and community composition. In the laboratory experiment, the grazer (caddisfly) effect on periphyton biomass specific (13)C uptake and nutrient content was much stronger than the effects of light and nutrients. In particular, grazers significantly reduced periphyton biomass and increased biomass specific (13)C uptake and C:nutrient ratios. The energy transfer efficiency, estimated as a ratio between (13)C uptake by caddisfly and periphyton, was positively affected by light conditions, whereas the nutrient effect was not significant. We suggest that the observed effects on energy transfer were related to the increased diet contribution of highly palatable green algae, stimulated by higher light levels. Also, high heterotrophic microbial activity under low light levels would facilitate energy loss through respiration and decrease overall trophic transfer efficiency. These findings suggest that even a small increase in light intensity could result in community

  18. Efficient and stable single-dopant white OLEDs based on 9,10-bis (2-naphthyl) anthracene

    International Nuclear Information System (INIS)

    Tao Silu; Peng Zhaokuai; Zhang Xiaohong; Wu Shikang

    2006-01-01

    Efficient white organic light-emitting diodes (WOLEDs) are fabricated with a thin layer of 9,10-bis (2-naphthyl) anthracene (ADN) doped with Rubrene as the source of white emission. A device with the structure of ITO/NPB (70nm)/ADN: 0.5% Rubrene (30nm)/Alq 3 (50nm)/MgAg shows a maximum current efficiency of 3.7cd/A, with the CIE coordinates of x=0.33, y=0.43. The EL spectrum of the devices and the CIE coordinates remains almost the same when the voltage is increased from 10 to 15V and the current efficiency remains quite stable with the current density increased from 20 to 250mA/cm 2

  19. Improving the Efficiency of Solid State Light Sources

    International Nuclear Information System (INIS)

    Joanna McKittrick

    2003-01-01

    This proposal addresses the national need to develop a high efficiency light source for general illumination applications. The goal is to perform research that would lead to the fabrication of a unique solid state, white-emitting light source. This source is based on an InGaN/GaN UV-emitting chip that activates a luminescent material (phosphor) to produce white light. White-light LEDs are commercially available which use UV from a GaN chip to excite a phosphor suspended in epoxy around the chip. Currently, these devices are relatively inefficient. This research will target one technical barrier that presently limits the efficiency of GaN based devices. Improvements in efficiencies will be achieved by improving the internal conversion efficiency of the LED die, by improving the coupling between the die and phosphor(s) to reduce losses at the surfaces, and by selecting phosphors to maximize the emissions from the LEDs in conversion to white light. The UCSD research team proposes for this project to develop new phosphors that have high quantum efficiencies that can be activated by the UV-blue (360-410 nm) light emitted by the GaN device. The main goal for the UCSD team was to develop new phosphor materials with a very specific property: phosphors that could be excited at long UV-wavelengths (λ=350-410 nm). The photoluminescence of these new phosphors must be activated with photons emitted from GaN based dies. The GaN diodes can be designed to emit UV-light in the same range (λ=350-410 nm). A second objective, which is also very important, is to search for alternate methods to fabricate these phosphors with special emphasis in saving energy and time and reduce pollution

  20. Improving the Efficiency of Solid State Light Sources

    Energy Technology Data Exchange (ETDEWEB)

    Joanna McKittrick

    2003-03-31

    This proposal addresses the national need to develop a high efficiency light source for general illumination applications. The goal is to perform research that would lead to the fabrication of a unique solid state, white-emitting light source. This source is based on an InGaN/GaN UV-emitting chip that activates a luminescent material (phosphor) to produce white light. White-light LEDs are commercially available which use UV from a GaN chip to excite a phosphor suspended in epoxy around the chip. Currently, these devices are relatively inefficient. This research will target one technical barrier that presently limits the efficiency of GaN based devices. Improvements in efficiencies will be achieved by improving the internal conversion efficiency of the LED die, by improving the coupling between the die and phosphor(s) to reduce losses at the surfaces, and by selecting phosphors to maximize the emissions from the LEDs in conversion to white light. The UCSD research team proposes for this project to develop new phosphors that have high quantum efficiencies that can be activated by the UV-blue (360-410 nm) light emitted by the GaN device. The main goal for the UCSD team was to develop new phosphor materials with a very specific property: phosphors that could be excited at long UV-wavelengths ({lambda}=350-410 nm). The photoluminescence of these new phosphors must be activated with photons emitted from GaN based dies. The GaN diodes can be designed to emit UV-light in the same range ({lambda}=350-410 nm). A second objective, which is also very important, is to search for alternate methods to fabricate these phosphors with special emphasis in saving energy and time and reduce pollution.

  1. Environmentally Benign Technology for Efficient Warm-White Light Emission

    Science.gov (United States)

    Shen, Pin-Chun; Lin, Ming-Shiun; Lin, Ching-Fuh

    2014-06-01

    Nowadays efficient down conversion for white light emission is mainly based on rare-earth doped phosphors or cadmium-containing quantum dots. Although they exhibit high luminescence efficiency, the rare-earth mining and cadmium pollution have so far led to extremely high environmental cost, which conflicts the original purpose of pursuing efficient lighting. Here, we explore a new strategy to achieve efficient luminescence conversion based on polymer-decorated nanoparticles. The ZnO and Mn2+ doped ZnS nanoparticles are encapsulated by poly(9,9-di-n- hexylfluorenyl-2,7-diyl). The resultant core-shell nanocomposites then encompass three UV-to-visible luminescence conversion routes for photon emissions at blue, green, and orange colors, respectively. As a result, the color temperature is widely tunable (2100 K ~ 6000 K), so candle light or pure white light can be generated. The quantum yield up to 91% could also be achieved. Such rare-earth-element free nanocomposites give the bright perspectives for energy-saving, healthy, and environmentally benign lighting.

  2. High light extraction efficiency in bulk-GaN based volumetric violet light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    David, Aurelien, E-mail: adavid@soraa.com; Hurni, Christophe A.; Aldaz, Rafael I.; Cich, Michael J.; Ellis, Bryan; Huang, Kevin; Steranka, Frank M.; Krames, Michael R. [Soraa Inc., 6500 Kaiser Dr., Fremont, California 94555 (United States)

    2014-12-08

    We report on the light extraction efficiency of III-Nitride violet light-emitting diodes with a volumetric flip-chip architecture. We introduce an accurate optical model to account for light extraction. We fabricate a series of devices with varying optical configurations and fit their measured performance with our model. We show the importance of second-order optical effects like photon recycling and residual surface roughness to account for data. We conclude that our devices reach an extraction efficiency of 89%.

  3. Relative intensity noise of temperature-stable, energy-efficient 980 nm VCSELs

    Directory of Open Access Journals (Sweden)

    Hui Li

    2017-02-01

    Full Text Available The relative intensity noise (RIN of temperature-stable, energy-efficient oxide confined vertical-cavity surface-emitting lasers (VCSELs have been investigated. Low energy consumption data transmission is achieved by using small oxide-aperture diameter VCSELs biased at small currents. We demonstrate that energy efficiency is not in conflict with our VCSELs’ RIN characteristics. The experimental results indicate that small oxide-aperture diameter VCSELs, which are most suitable for energy-efficient, temperature-stable operation, exhibit lower laser RIN due to less mode competition inside the smaller optical cavity volume. Our energy-efficient VCSELs fulfill the RIN requirements of the 32G Fibre Channel standard.

  4. Energy efficiency in light-frame wood construction

    Science.gov (United States)

    Gerald E. Sherwood; Gunard Hans

    1979-01-01

    This report presents information needed for design and construction of energy-efficient light-frame wood structures. The opening section discusses improving the thermal performance of a house by careful planning and design. A second section of the report provides technical information on the thermal properties of construction materials, and on the basic engineering...

  5. Growth, light interception, radiation use efficiency and productivity of ...

    African Journals Online (AJOL)

    The purpose of this study was to assess the influence of sowing date on growth, light interception, radiation use efficiency and productivity of mungbean cultivars. The experiment comprised four sowing dates at ten days interval, viz. 08, 18, 28 July and 07 August 2006 and two cultivars, viz. Gofa local and MH-97-6.

  6. Efficient and stable single-doped white OLEDs using a palladium-based phosphorescent excimer.

    Science.gov (United States)

    Fleetham, Tyler; Ji, Yunlong; Huang, Liang; Fleetham, Trenten S; Li, Jian

    2017-12-01

    A tetradentate Pd(ii) complex, Pd3O3, which exhibits highly efficient excimer emission is synthesized and characterized. Pd3O3 can achieve blue emission despite using phenyl-pyridine emissive ligands which have been a mainstay of stable green and red phosphorescent emitter designs, making Pd3O3 a good candidate for stable blue or white OLEDs. Pd3O3 exhibits strong and efficient phosphorescent excimer emission expanding the excimer based white OLEDs beyond the sole class of Pt complexes. Devices of Pd3O3 demonstrate peak external quantum efficiencies as high as 24.2% and power efficiencies of 67.9 Lm per W for warm white devices. Furthermore, Pd3O3 devices in a carefully designed stable structure achieved a device operational lifetime of nearly 3000 h at 1000 cd m -2 without any outcoupling enhancement while simultaneously achieving peak external quantum efficiencies of 27.3% and power efficiencies over 81 Lm per W.

  7. Biomimetic spiral grating for stable and highly efficient absorption in crystalline silicon thin-film solar cells

    KAUST Repository

    Hou, Jin

    2017-09-12

    By emulating the phyllotaxis structure of natural plants, which has an efficient and stable light capture capability, a two-dimensional spiral grating is introduced on the surface of crystalline silicon solar cells to obtain both efficient and stable light absorption. Using the rigorous coupled wave analysis method, the absorption performance on structural parameter variations of spiral gratings is investigated firstly. Owing to diffraction resonance and excellent superficies antireflection, the integrated absorption of the optimal spiral grating cell is raised by about 77 percent compared with the conventional slab cell. Moreover, though a 15 percent deviation of structural parameters from the optimal spiral grating is applied, only a 5 percent decrease of the absorption is observed. This reveals that the performance of the proposed grating would tolerate large structural variations. Furthermore, the angular and polarization dependence on the absorption of the optimized cell is studied. For average polarizations, a small decrease of only 11 percent from the maximum absorption is observed within an incident angle ranging from −70 to 70 degrees. The results show promising application potentials of the biomimetic spiral grating in the solar cell.

  8. High-flux focusable color-tunable and efficient white-light-emitting diode light engine for stage lighting

    DEFF Research Database (Denmark)

    Chakrabarti, Maumita; Pedersen, Henrik Chresten; Petersen, Paul Michael

    2016-01-01

    %. The design, simulation, and optimization of the lightengine is described and compared to the experimental characterization of a prototype. The light engine is optimizedthrough the simulated design of reflector, total internal reflection lens, and MA, as well as the number ofLEDs. An optical efficiency of 59......A color mixing light-emitting diode (LED) light engine that can replace 2-kW halogen–Fresnel spotlightwith high-luminous flux in excess of 20,000 lm is reported for applications in professional stage and studio lighting.The light engine focuses and mixes the light from 210 LEDs of five different...... colors through a microlens array(MA) at the gate of ∅50 mm. Hence, it produces homogeneous color-mixed tunable white light from 3000 to6000 K that can be adjustable from flood to spot position providing 10% translational loss, whereas the correspondingloss from the halogen–Fresnel spotlight is 37...

  9. Increased collection efficiency of LIFI high intensity electrodeless light source

    Science.gov (United States)

    Hafidi, Abdeslam; DeVincentis, Marc; Duelli, Markus; Gilliard, Richard

    2008-02-01

    Recently, RF driven electrodeless high intensity light sources have been implemented successfully in the projection display systems for HDTV and videowall applications. This paper presents advances made in the RF waveguide and electric field concentrator structures with the purpose of reducing effective arc size and increasing light collection. In addition, new optical designs are described that further improve system efficiency. The results of this work demonstrate that projection system light throughput is increased relative to previous implementations and performance is optimized for home theater and other front projector applications that maintain multi-year lifetime without re-lamping, complete spectral range, fast start times and high levels of dynamic contrast due to dimming flexibility in the light source system.

  10. Efficient lighting in buildings: The lack of legislation in Portugal

    International Nuclear Information System (INIS)

    Almeida, António Manuel; Martins, António Gomes

    2014-01-01

    The behavior of building designers is conditioned by the existing legislation and regulations in the national context in which they operate. However, in the Portuguese legislation there are no rules concerning the use of daylight, and therefore, designers are not stimulated to adopt solutions that make use of the existing potential of sunlight availability. In the same way, it is difficult to understand the lack of specific regulation, with quantified targets, limiting power density of artificial lighting installed inside buildings. The present opportunity, generated by the need to carry out the revision of Portuguese building energy systems regulation, should be used to fill the existing gap in national legislation regarding those matters. In this paper the authors present some proposals for future legislation that will have as central purpose the utilization of efficient lighting systems and the promotion of architectural solutions that optimize the use of daylighting. It is possible, and desirable, to add new directives to national legislation that contribute to the improvement of Portuguese buildings, characterized by its good performance in terms of daylight availability, and at the same time, increasing the energy efficiency and reducing the energy consumption of lighting systems installed in those buildings. - Highlights: • In the Portuguese legislation there are no rules concerning the use of daylight. • Lack of specific regulation limiting power density of artificial lighting. • Revision of Portuguese building energy systems regulation. • Some proposals for future legislation. • Improvement of Portuguese buildings promoting energy efficiency

  11. Operational efficiency of the lighting system of bus salons

    Directory of Open Access Journals (Sweden)

    Brytkovskyi V.M.

    2016-08-01

    Full Text Available In recent years the problem of safety of people is studied primarily in aspects of natural and man-made disasters, fire, health and safety in the workplace. A problem connected with the way of life of the people, in particular with the use of bus transport remains almost out of sight. In addition to the foregoing, there is another side to the issue: modern development of industry and transport is characterized by large-scale introduction of technical measures aimed at saving energy In the specified aspect theoretical dependences for evaluation of technological economic efficiency of light sources in indoor lighting system buses are grounded. This theoretical dependency will make analytical framework justification applying the respective sources of light, taking into account the hygiene requirements to illumination. The methodology of calculation of economic efficiency of lighting of bus salons is offered. Estimating parameter is justified relative objective function value costs per unit of time or distance. The greatest costs are typical for lamps with incandescent bulbs. The least is common to lamps with fluorescent lamps. Led bulbs have no significant advantage even over incandescent lamps. The reason for this is the relatively high color temperature radiation of LED lamps that requires more light levels and, consequently, the high cost of energy, as well as relatively large initial cost of these lamps.

  12. Lighting energy efficiency in office buildings: Sri Lanka

    Energy Technology Data Exchange (ETDEWEB)

    Wijayatunga, Priyantha D.C. [Moratuwa Univ., Dept. of Electrical Engineering, Moratuwa (Sri Lanka); Fernando, W.J.L.S.; Ranasinghe, S. [Sri Lanka Energy Managers Association, Colombo (Sri Lanka)

    2003-09-01

    This paper describes a study conducted in the lighting sector of office buildings as a part of a broader research study aimed at developing building codes for Sri Lanka addressing lighting as well as thermal comfort in order to optimise the use of electricity within these buildings. The study covered different tasks performed in office buildings and the optimum lighting levels required to perform these tasks in the office environment in Sri Lanka. Also, it included assessing the visual performance of people involved in different activities under varying illumination levels in a controlled environment and a comparison of these optimum lighting levels with international standards. It can be seen that the required optimum lighting levels are generally lower in Sri Lanka in comparison to specified standard levels, and this scenario is likely to be similar in other developing countries too. These findings clearly emphasise the need to adopt lighting standards most appropriate to local conditions, in turn helping improve the energy efficiency within buildings. (Author)

  13. Lighting energy efficiency in office buildings: Sri Lanka

    International Nuclear Information System (INIS)

    Wijayatunga, Priyantha D.C.; Fernando, W.J.L.S.; Ranasinghe, S.

    2003-01-01

    This paper describes a study conducted in the lighting sector of office buildings as a part of a broader research study aimed at developing building codes for Sri Lanka addressing lighting as well as thermal comfort in order to optimise the use of electricity within these buildings. The study covered different tasks performed in office buildings and the optimum lighting levels required to perform these tasks in the office environment in Sri Lanka. Also, it included assessing the visual performance of people involved in different activities under varying illumination levels in a controlled environment and a comparison of these optimum lighting levels with international standards. It can be seen that the required optimum lighting levels are generally lower in Sri Lanka in comparison to specified standard levels, and this scenario is likely to be similar in other developing countries too. These findings clearly emphasise the need to adopt lighting standards most appropriate to local conditions, in turn helping improve the energy efficiency within buildings

  14. Efficiency optimization of green phosphorescent organic light-emitting device

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jung Soo; Jeon, Woo Sik; Yu, Jae Hyung [Department of Information Display, Kyung Hee University, Dongdaemoon-gu, Seoul 130-701 (Korea, Republic of); Pode, Ramchandra, E-mail: rbpode@khu.ac.k [Department of Physics, Kyung Hee University, Dongdaemoon-gu, Seoul 130-701 (Korea, Republic of); Kwon, Jang Hyuk, E-mail: jhkwon@khu.ac.k [Department of Information Display, Kyung Hee University, Dongdaemoon-gu, Seoul 130-701 (Korea, Republic of)

    2011-03-01

    Using a narrow band gap host of bis[2-(2-hydroxyphenyl)-pyridine]beryllium (Bepp{sub 2}) and green phosphorescent Ir(ppy){sub 3} [fac-tris(2-phenylpyridine) iridium III] guest concentration as low as 2%, high efficiency phosphorescent organic light-emitting diode (PHOLED) is realized. Current and power efficiencies of 62.5 cd/A (max.), 51.0 lm/W (max.), and external quantum efficiency (max.) of 19.8% are reported in this green PHOLED. A low current efficiency roll-off value of 10% over the brightness of 10,000 cd/m{sup 2} is noticed in this Bepp{sub 2} single host device. Such a high efficiency is obtained by the optimization of the doping concentration with the knowledge of the hole trapping and the emission zone situations in this host-guest system. It is suggested that the reported device performance is suitable for applications in high brightness displays and lighting.

  15. High-Efficiency Nitride-Base Photonic Crystal Light Sources

    Energy Technology Data Exchange (ETDEWEB)

    James Speck; Evelyn Hu; Claude Weisbuch; Yong-Seok Choi; Kelly McGroddy; Gregor Koblmuller; Elison Matioli; Elizabeth Rangel; Fabian Rol; Dobri Simeonov

    2010-01-31

    The research activities performed in the framework of this project represent a major breakthrough in the demonstration of Photonic Crystals (PhC) as a competitive technology for LEDs with high light extraction efficiency. The goals of the project were to explore the viable approaches to manufacturability of PhC LEDS through proven standard industrial processes, establish the limits of light extraction by various concepts of PhC LEDs, and determine the possible advantages of PhC LEDs over current and forthcoming LED extraction concepts. We have developed three very different geometries for PhC light extraction in LEDs. In addition, we have demonstrated reliable methods for their in-depth analysis allowing the extraction of important parameters such as light extraction efficiency, modal extraction length, directionality, internal and external quantum efficiency. The information gained allows better understanding of the physical processes and the effect of the design parameters on the light directionality and extraction efficiency. As a result, we produced LEDs with controllable emission directionality and a state of the art extraction efficiency that goes up to 94%. Those devices are based on embedded air-gap PhC - a novel technology concept developed in the framework of this project. They rely on a simple and planar fabrication process that is very interesting for industrial implementation due to its robustness and scalability. In fact, besides the additional patterning and regrowth steps, the process is identical as that for standard industrially used p-side-up LEDs. The final devices exhibit the same good electrical characteristics and high process yield as a series of test standard LEDs obtained in comparable conditions. Finally, the technology of embedded air-gap patterns (PhC) has significant potential in other related fields such as: increasing the optical mode interaction with the active region in semiconductor lasers; increasing the coupling of the incident

  16. Measurements of light absorption efficiency in InSb nanowires

    Directory of Open Access Journals (Sweden)

    A. Jurgilaitis

    2014-01-01

    Full Text Available We report on measurements of the light absorption efficiency of InSb nanowires. The absorbed 70 fs light pulse generates carriers, which equilibrate with the lattice via electron-phonon coupling. The increase in lattice temperature is manifested as a strain that can be measured with X-ray diffraction. The diffracted X-ray signal from the excited sample was measured using a streak camera. The amount of absorbed light was deduced by comparing X-ray diffraction measurements with simulations. It was found that 3.0(6% of the radiation incident on the sample was absorbed by the nanowires, which cover 2.5% of the sample.

  17. Funnel-shaped silicon nanowire for highly efficient light trapping.

    Science.gov (United States)

    Hussein, Mohamed; Hameed, Mohamed Farhat O; Areed, Nihal F F; Yahia, Ashraf; Obayya, S S A

    2016-03-01

    In this Letter, funnel-shaped silicon nanowires (SiNWs) are newly introduced for highly efficient light trapping. The proposed designs of nanowires are inspired by the funnel shape, which enhances the light trapping with reduced reflections in the wavelength range from 300 to 1100 nm. Composed of both cylindrical and conical units, the funnel nanowires increase the number of leaky mode resonances, yielding an absorption enhancement relative to a uniform nanowire array. The optical properties of the suggested nanowires have been numerically investigated using the 3D finite difference time domain (FDTD) method and compared to cylindrical and conical counterparts. The structural geometrical parameters are studied to maximize the ultimate efficiency and hence the short-circuit current. Carefully engineered structure geometry is shown to yield improved light absorption useful for solar cell applications. The proposed funnel-shaped SiNWs offer an ultimate efficiency of 41.8%, with an enhancement of 54.8% relative to conventional cylindrical SiNWs. Additionally, short-circuit current of 34.2  mA/cm2 is achieved using the suggested design.

  18. Scalable Light Module for Low-Cost, High-Efficiency Light- Emitting Diode Luminaires

    Energy Technology Data Exchange (ETDEWEB)

    Tarsa, Eric [Cree, Inc., Goleta, CA (United States)

    2015-08-31

    During this two-year program Cree developed a scalable, modular optical architecture for low-cost, high-efficacy light emitting diode (LED) luminaires. Stated simply, the goal of this architecture was to efficiently and cost-effectively convey light from LEDs (point sources) to broad luminaire surfaces (area sources). By simultaneously developing warm-white LED components and low-cost, scalable optical elements, a high system optical efficiency resulted. To meet program goals, Cree evaluated novel approaches to improve LED component efficacy at high color quality while not sacrificing LED optical efficiency relative to conventional packages. Meanwhile, efficiently coupling light from LEDs into modular optical elements, followed by optimally distributing and extracting this light, were challenges that were addressed via novel optical design coupled with frequent experimental evaluations. Minimizing luminaire bill of materials and assembly costs were two guiding principles for all design work, in the effort to achieve luminaires with significantly lower normalized cost ($/klm) than existing LED fixtures. Chief project accomplishments included the achievement of >150 lm/W warm-white LEDs having primary optics compatible with low-cost modular optical elements. In addition, a prototype Light Module optical efficiency of over 90% was measured, demonstrating the potential of this scalable architecture for ultra-high-efficacy LED luminaires. Since the project ended, Cree has continued to evaluate optical element fabrication and assembly methods in an effort to rapidly transfer this scalable, cost-effective technology to Cree production development groups. The Light Module concept is likely to make a strong contribution to the development of new cost-effective, high-efficacy luminaries, thereby accelerating widespread adoption of energy-saving SSL in the U.S.

  19. Nonlinear theory of stable, efficient operation of a gyrotron at cyclotron harmonics

    International Nuclear Information System (INIS)

    Saraph, G.P.; Antonsen, T.M. Jr.; Nusinovich, G.S.; Levush, B.

    1993-01-01

    One of the main obstacles in achieving stable, efficient operation at the cyclotron harmonics in a gyrotron is mode competition with parasitic modes at the fundamental frequency. In this article, the nonlinear dynamics of mode interactions in such a system are studied using a multifrequency, time-dependent model. The results of numerical simulations for a second harmonic gyrotron are presented by considering two starting scenarios: (a) fast voltage rise or an instant turn-on case, and (b) slow voltage rise case. For the first case, it is demonstrated that for a certain range of operating parameters, the presence of a parasitic mode at the fundamental can be helpful in the excitation of the second harmonic operating mode. In the second case, it is found that the unstable operating region increases with the value of the rise time constant of the electrode voltages. Stable, efficient gyrotron operation at the second harmonic is demonstrated using the numerical study

  20. Lighting

    Data.gov (United States)

    Federal Laboratory Consortium — Lighting Systems Test Facilities aid research that improves the energy efficiency of lighting systems. • Gonio-Photometer: Measures illuminance from each portion of...

  1. High-Efficiency Nitride-Based Solid-State Lighting

    Energy Technology Data Exchange (ETDEWEB)

    Paul T. Fini; Shuji Nakamura

    2005-07-30

    In this final technical progress report we summarize research accomplished during Department of Energy contract DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. Two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and the Lighting Research Center at Rensselaer Polytechnic Institute (led by Dr. N. Narendran), pursued the goals of this contract from thin film growth, characterization, and packaging/luminaire design standpoints. The UCSB team initially pursued the development of blue gallium nitride (GaN)-based vertical-cavity surface-emitting lasers, as well as ultraviolet GaN-based light emitting diodes (LEDs). In Year 2, the emphasis shifted to resonant-cavity light emitting diodes, also known as micro-cavity LEDs when extremely thin device cavities are fabricated. These devices have very directional emission and higher light extraction efficiency than conventional LEDs. Via the optimization of thin-film growth and refinement of device processing, we decreased the total cavity thickness to less than 1 {micro}m, such that micro-cavity effects were clearly observed and a light extraction efficiency of over 10% was reached. We also began the development of photonic crystals for increased light extraction, in particular for so-called ''guided modes'' which would otherwise propagate laterally in the device and be re-absorbed. Finally, we pursued the growth of smooth, high-quality nonpolar a-plane and m-plane GaN films, as well as blue light emitting diodes on these novel films. Initial nonpolar LEDs showed the expected behavior of negligible peak wavelength shift with increasing drive current. M-plane LEDs in particular show promise, as unpackaged devices had unsaturated optical output power of {approx} 3 mW at 200 mA drive current. The LRC's tasks were aimed at developing the subcomponents necessary for packaging UCSB's light

  2. Analysis of light extraction efficiency of GaN-based light-emitting diodes

    International Nuclear Information System (INIS)

    Wang Pei; Cao Bin; Gan Zhiyin; Liu Sheng

    2011-01-01

    GaN-based light emitting diodes (LEDs) as one of the most important light source in next-generation solid-state lighting have been extensively studied and remarkable progress has been obtained. However, the light extraction efficiency (LEE) is not sufficient to satisfy application requirements. Most of the photons generated in multiple quantum well (MQW) always are trapped inside the semiconductor because both the reflection index of GaN and InGaN are higher than that of air, which results in total internal reflection (TIR). Great efforts were made in enhancing light extraction of LEDs experimentally in previous investigation. However, detailed theoretical studies in predicting the LEE of different types of LEDs are not available. In this paper the light extraction efficiency(LEE) of conventional chip (CC), flip chip (FC) and vertical chip (VC) is investigated using Monte Carlo ray tracing method is presented in conventional chip (CC). Monte Carlo ray tracing simulation based on statistics is known to be one of the most suitable methods to analyze the dependence of the light extraction efficiency of LEDs on the variety of the device parameters. Diffused bottom surface was found to be better for improvement of LEE than the perfect mirror surface. When there is a material with higher refraction index on the top surface the VC structure has the highest LEE no matter the bottom surface is perfect mirror or diffuse surface, which is above 80%. It is indicated that VC is potential in high-power GaN-based LEDs from the results.

  3. Efficient polymer white-light-emitting diodes with a single-emission layer of fluorescent polymer blend

    International Nuclear Information System (INIS)

    Niu Qiaoli; Xu Yunhua; Jiang Jiaxing; Peng Junbiao; Cao Yong

    2007-01-01

    Efficient polymer white-light-emitting diodes (WPLEDs) have been fabricated with a single layer of fluorescent polymer blend. The device structure consists of ITO/PEDOT/PVK/emissive layer/Ba/Al. The emissive layer is a blend of poly(9,9-dioctylfluorene) (PFO), phenyl-substituted PPV derivative (P-PPV) and a copolymer of 9,9-dioctylfluorene and 4,7-di(4-hexylthien-2-yl)-2,1,3-benzothiadiazole (PFO-DHTBT), which, respectively, emits blue, green and red light. The emission of pure and efficient white light was implemented by tuning the blend weight ratio of PFO: P-PPV: PFO-DHTBT to 96:4:0.4. The maximum current efficiency and luminance are, respectively, 7.6 cd/A at 6.7 V and 11930 cd/m 2 at 11.2 V. The CIE coordinates of white-light emission were stable with the drive voltages

  4. Influence of precipitating light elements on stable stratification below the core/mantle boundary

    Science.gov (United States)

    O'Rourke, J. G.; Stevenson, D. J.

    2017-12-01

    Stable stratification below the core/mantle boundary is often invoked to explain anomalously low seismic velocities in this region. Diffusion of light elements like oxygen or, more slowly, silicon could create a stabilizing chemical gradient in the outermost core. Heat flow less than that conducted along the adiabatic gradient may also produce thermal stratification. However, reconciling either origin with the apparent longevity (>3.45 billion years) of Earth's magnetic field remains difficult. Sub-isentropic heat flow would not drive a dynamo by thermal convection before the nucleation of the inner core, which likely occurred less than one billion years ago and did not instantly change the heat flow. Moreover, an oxygen-enriched layer below the core/mantle boundary—the source of thermal buoyancy—could establish double-diffusive convection where motion in the bulk fluid is suppressed below a slowly advancing interface. Here we present new models that explain both stable stratification and a long-lived dynamo by considering ongoing precipitation of magnesium oxide and/or silicon dioxide from the core. Lithophile elements may partition into iron alloys under extreme pressure and temperature during Earth's formation, especially after giant impacts. Modest core/mantle heat flow then drives compositional convection—regardless of thermal conductivity—since their solubility is strongly temperature-dependent. Our models begin with bulk abundances for the mantle and core determined by the redox conditions during accretion. We then track equilibration between the core and a primordial basal magma ocean followed by downward diffusion of light elements. Precipitation begins at a depth that is most sensitive to temperature and oxygen abundance and then creates feedbacks with the radial thermal and chemical profiles. Successful models feature a stable layer with low seismic velocity (which mandates multi-component evolution since a single light element typically

  5. HIGH-EFFICIENCY NITRIDE-BASED SOLID-STATE LIGHTING

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Paul T. Fini; Prof. Shuji Nakamura

    2002-09-01

    In this annual report we summarize the progress obtained in the first year with the support of DoE contract No.DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. The two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and Rensselaer Polytechnic Institute (led by Dr. N. Narendran), are pursuing the goals of this contract from thin film growth, characterization, and packaging standpoints. The UCSB team has made significant progress in the development of GaN vertical cavity surface-emitting lasers (VCSELs) as well as light-emitting diodes (LEDs) with AlGaN active regions emitting in the ultraviolet (UV). The Rensselaer team has developed target specifications for some of the key parameters for the proposed solid-state lighting system, including a luminous flux requirement matrix for various lighting applications, optimal spectral power distributions, and the performance characteristics of currently available commercial LEDs for eventual comparisons to the devices developed in the scope of this project.

  6. HIGH-EFFICIENCY NITRIDE-BASED SOLID-STATE LIGHTING

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Paul T. Fini; Prof. Shuji Nakamura

    2002-04-30

    In this semiannual report we summarize the progress obtained in the first six months with the support of DoE contract No.DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. The two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and Rensselaer Polytechnic Institute (led by Dr. N. Narendran), are pursuing the goals of this contract from thin film growth, characterization, and packaging standpoints. The UCSB team has made significant progress in the development of GaN vertical cavity surface-emitting lasers (VCSELs) as well as light-emitting diodes (LEDs) with AlGaN active regions emitting in the ultraviolet (UV). The Rensselaer team has developed target specifications for some of the key parameters for the proposed solid-state lighting system, including a luminous flux requirement matrix for various lighting applications, optimal spectral power distributions, and the performance characteristics of currently available commercial LEDs for eventual comparisons to the devices developed in the scope of this project.

  7. Efficiency of light curing units in a government dental school.

    Science.gov (United States)

    Nassar, Hani M; Ajaj, Reem; Hasanain, Fatin

    2018-01-01

    The light intensity of a light-curing unit is a crucial factor that affects the clinical longevity of resin composites. This study aimed to investigate the efficiency of light-curing units in use at a local governmental dental school for curing conventional and bulk-fill resin materials. A total of 166 light-curing units at three locations were examined, and the brand, type, clinic location, diameter of curing tip, tip cleanliness (using a visual score), and the output (in mW/cm 2 using a digital radiometer) were recorded. Only 23.5% of the units examined had clean tips, with the graduate student clinical area containing the highest percentage of clean tips. Further, tips with poor cleanliness score values were associated with significantly lower output intensities. A small percentage (9.4%) of units was capable of producing intensities higher than 1,200 mW/cm 2 and lower than 600 mW/cm 2 (7.6%). The majority of the low intensity units were located in the undergraduate student area, which also contained the highest number of units with intensities between 900 and 1,200 mW/cm 2 . The output of all the units in service was satisfactory for curing conventional resin composites, and most units were capable of curing bulk-fill resin materials.

  8. Enhancing the light utilization efficiency of microalgae using organic dyes.

    Science.gov (United States)

    Seo, Yeong Hwan; Lee, Yonghee; Jeon, Duk Young; Han, Jong-In

    2015-04-01

    Solar radiation is composed of wide light spectrum including the range which cannot be utilized for microalgae. To enhance the light utilization efficiency, organic dye solutions of rhodamine101 and 9,10-diphenylanthracene were used as wavelength converters. Each dye affected cell growth and lipid accumulation differently, based on the response of each to different light spectrum. Under a light intensity of 50 W/m(2), maximum cell growth (1.5 g/L) was obtained with the red organic dye rhodamine101, whereas best lipid content (30%) with the blue type 9,10-diphenylanthracene. These two separate and complementary traits could be combined by simple mixing, and in so doing optimal growth (1.5 g/L) as well as lipid accumulation (30%) was achieved: lipid productivity was 2.3 times greater than without the organic dye. This study proved that certain organic dye solutions could convert useless wavelengths to be useful for algae cultivation, thereby increasing the productivity of biomass and lipids. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Thin Film Packaging Solutions for High Efficiency OLED Lighting Products

    Energy Technology Data Exchange (ETDEWEB)

    None

    2008-06-30

    The objective of the 'Thin Film Packaging Solutions for High Efficiency OLED Lighting Products' project is to demonstrate thin film packaging solutions based on SiC hermetic coatings that, when applied to glass and plastic substrates, support OLED lighting devices by providing longer life with greater efficiency at lower cost than is currently available. Phase I Objective: Demonstrate thin film encapsulated working phosphorescent OLED devices on optical glass with lifetime of 1,000 hour life, CRI greater than 75, and 15 lm/W. Phase II Objective: Demonstrate thin film encapsulated working phosphorescent OLED devices on plastic or glass composite with 25 lm/W, 5,000 hours life, and CRI greater than 80. Phase III Objective: Demonstrate 2 x 2 ft{sup 2} thin film encapsulated working phosphorescent OLED with 40 lm/W, 10,000 hour life, and CRI greater than 85. This report details the efforts of Phase III (Budget Period Three), a fourteen month collaborative effort that focused on optimization of high-efficiency phosphorescent OLED devices and thin-film encapsulation of said devices. The report further details the conclusions and recommendations of the project team that have foundation in all three budget periods for the program. During the conduct of the Thin Film Packaging Solutions for High Efficiency OLED Lighting Products program, including budget period three, the project team completed and delivered the following achievements: (1) a three-year marketing effort that characterized the near-term and longer-term OLED market, identified customer and consumer lighting needs, and suggested prototype product concepts and niche OLED applications lighting that will give rise to broader market acceptance as a source for wide area illumination and energy conservation; (2) a thin film encapsulation technology with a lifetime of nearly 15,000 hours, tested by calcium coupons, while stored at 16 C and 40% relative humidity ('RH'). This encapsulation technology

  10. Phosphorescent Pt(II) and Pd(II) Complexes for Efficient, High-Color-Quality, and Stable OLEDs.

    Science.gov (United States)

    Fleetham, Tyler; Li, Guijie; Li, Jian

    2017-02-01

    Phosphorescent organic light-emitting diodes (OLEDs) are leading candidates for next-generation displays and solid-state lighting technologies. Much of the academic and commercial pursuits in phosphorescent OLEDs have been dominated by Ir(III) complexes. Over the past decade recent developments have enabled square planar Pt(II) and Pd(II) complexes to meet or exceed the performance of Ir complexes in many aspects. In particular, the development of N-heterocyclic carbene-based emitters and tetradentate cyclometalated Pt and Pd complexes have significantly improved the emission efficiency and reduced their radiative lifetimes making them competitive with the best reported Ir complexes. Furthermore, their unique and diverse molecular design possibilities have enabled exciting photophysical attributes including narrower emission spectra, excimer -based white emission, and thermally activated delayed fluorescence. These developments have enabled the fabrication of efficient and "pure" blue OLEDs, single-doped white devices with EQEs of over 25% and high CRI, and device operational lifetimes which show early promise that square planar metal complexes can be stable enough for commercialization. These accomplishments have brought Pt complexes to the forefront of academic research. The molecular design strategies, photophysical characteristics, and device performance resulting from the major advancements in emissive Pt and Pd square planar complexes are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Light-enabled reversible self-assembly and tunable optical properties of stable hairy nanoparticles

    Science.gov (United States)

    Chen, Yihuang; Wang, Zewei; He, Yanjie; Yoon, Young Jun; Jung, Jaehan; Zhang, Guangzhao; Lin, Zhiqun

    2018-02-01

    The ability to dynamically organize functional nanoparticles (NPs) via the use of environmental triggers (temperature, pH, light, or solvent polarity) opens up important perspectives for rapid and convenient construction of a rich variety of complex assemblies and materials with new structures and functionalities. Here, we report an unconventional strategy for crafting stable hairy NPs with light-enabled reversible and reliable self-assembly and tunable optical properties. Central to our strategy is to judiciously design amphiphilic star-like diblock copolymers comprising inner hydrophilic blocks and outer hydrophobic photoresponsive blocks as nanoreactors to direct the synthesis of monodisperse plasmonic NPs intimately and permanently capped with photoresponsive polymers. The size and shape of hairy NPs can be precisely tailored by modulating the length of inner hydrophilic block of star-like diblock copolymers. The perpetual anchoring of photoresponsive polymers on the NP surface renders the attractive feature of self-assembly and disassembly of NPs on demand using light of different wavelengths, as revealed by tunable surface plasmon resonance absorption of NPs and the reversible transformation of NPs between their dispersed and aggregated states. The dye encapsulation/release studies manifested that such photoresponsive NPs may be exploited as smart guest molecule nanocarriers. By extension, the star-like block copolymer strategy enables the crafting of a family of stable stimuli-responsive NPs (e.g., temperature- or pH-sensitive polymer-capped magnetic, ferroelectric, upconversion, or semiconducting NPs) and their assemblies for fundamental research in self-assembly and crystallization kinetics of NPs as well as potential applications in optics, optoelectronics, magnetic technologies, sensory materials and devices, catalysis, nanotechnology, and biotechnology.

  12. Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system.

    Science.gov (United States)

    Charbonnier, Fabien; Roupsard, Olivier; le Maire, Guerric; Guillemot, Joannès; Casanoves, Fernando; Lacointe, André; Vaast, Philippe; Allinne, Clémentine; Audebert, Louise; Cambou, Aurélie; Clément-Vidal, Anne; Defrenet, Elsa; Duursma, Remko A; Jarri, Laura; Jourdan, Christophe; Khac, Emmanuelle; Leandro, Patricia; Medlyn, Belinda E; Saint-André, Laurent; Thaler, Philippe; Van Den Meersche, Karel; Barquero Aguilar, Alejandra; Lehner, Peter; Dreyer, Erwin

    2017-08-01

    In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from individual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant individually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees. © 2017 John Wiley & Sons Ltd.

  13. Designing High Efficient Solar Powered OLED Lighting Systems

    DEFF Research Database (Denmark)

    Ploug, Rasmus Overgaard; Poulsen, Peter Behrensdorff; Thorsteinsson, Sune

    2016-01-01

    for the 10 Wp version. Furthermore, we present measurements of state-of-the-art commercial available OLED with regards to the luminous flux, luminous efficacy, luminance homogeneity, temperature dependency and IV characteristic of the OLED panels. In addition, solar powered OLED product concepts are proposed.......OLEDs used in solar powered lighting applications is a market of the future. This paper reports the development of electronic Three-Port-Converters for PV OLED product integration in the low-power area respectively for 1-10 Wp and 10-50 Wp with a peak efficiency of 97% at 1.8 W of PV power...

  14. Enhanced quantum efficiency in blue-emitting polymer/dielectric nanolayer nanocomposite light-emitting devices

    International Nuclear Information System (INIS)

    Park, Jong Hyeok; Lim, Yong Taik; Park, O Ok; Yu, Jae-Woong; Kim, Jai Kyeong; Kim, Young Chul

    2004-01-01

    Light-emitting devices based on environmentally stable, blue-emitting polymer/dielectric nanolayer nanocomposites were fabricated by blending poly(di-octylfluorene) (PDOF) with organo-clay. By reducing the excimer formation that leads to long wavelength tails, the photoluminescence (PL) and electroluminescence (EL) color purity of the device was enhanced. When a conjugated polymer/dielectric nanolayer nanocomposite is applied to an EL device, we expect an electronic structure similar to the well-known quantum well in small nanodomains. The ratio of PDOF/organo-clay was regulated from 2:1 to 0.5:1 (w/w). The light-emitting device of 0.5:1 (w/w) blend demonstrated the highest quantum efficiency (QE), 0.72% (ph/el), which is ∼500 times higher value compared with that of the pure PDOF layer device. However, the driving voltage of the nanocomposite devices tended to increase with increasing organo-clay content

  15. Target-ion source unit ionization efficiency measurement by method of stable ion beam implantation

    CERN Document Server

    Panteleev, V.N; Fedorov, D.V; Moroz, F.V; Orlov, S.Yu; Volkov, Yu.M

    The ionization efficiency is one of the most important parameters of an on-line used target-ion source system exploited for production of exotic radioactive beams. The ionization efficiency value determination as a characteristic of a target-ion source unit in the stage of its normalizing before on-line use is a very important step in the course of the preparation for an on-line experiment. At the IRIS facility (Petersburg Nuclear Physics Institute, Gatchina) a reliable and rather precise method of the target-ion source unit ionization efficiency measurement by the method of stable beam implantation has been developed. The method worked out exploits an off-line mass-separator for the implantation of the ion beams of selected stable isotopes of different elements into a tantalum foil placed inside the Faraday cup in the focal plane of the mass-separator. The amount of implanted ions has been measured with a high accuracy by the current integrator connected to the Faraday cup. After the implantation of needed a...

  16. A guide for the laboratory information management system (LIMS) for light stable isotopes--Versions 7 and 8

    Science.gov (United States)

    Coplen, Tyler B.

    2000-01-01

    The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program, the Laboratory Information Management System (LIMS) for Light Stable Isotopes, is presented herein. Major benefits of this system include (i) a dramatic improvement in quality assurance, (ii) an increase in laboratory efficiency, (iii) a reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) a decrease in errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for laboratories. LIMS for Light Stable Isotopes is available for both Microsoft Office 97 Professional and Microsoft Office 2000 Professional as versions 7 and 8, respectively. Both source code (mdb file) and precompiled executable files (mde) are available. Numerous improvements have been made for continuous flow isotopic analysis in this version (specifically 7.13 for Microsoft Access 97 and 8.13 for Microsoft Access 2000). It is much easier to import isotopic results from Finnigan ISODAT worksheets, even worksheets on which corrections for amount of sample (linearity corrections) have been added. The capability to determine blank corrections using isotope mass balance from analyses of elemental analyzer samples has been added. It is now possible to calculate and apply drift corrections to isotopic

  17. Highly efficient phosphorescent blue and white organic light-emitting devices with simplified architectures

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chih-Hao, E-mail: chc@saturn.yzu.edu.tw [Department of Photonics Engineering, Yuan Ze University, Chung-Li, Taiwan 32003 (China); Ding, Yong-Shung; Hsieh, Po-Wei; Chang, Chien-Ping; Lin, Wei-Chieh [Department of Photonics Engineering, Yuan Ze University, Chung-Li, Taiwan 32003 (China); Chang, Hsin-Hua, E-mail: hhua3@mail.vnu.edu.tw [Department of Electro-Optical Engineering, Vanung University, Chung-Li, Taiwan 32061 (China)

    2011-09-01

    Blue phosphorescent organic light-emitting devices (PhOLEDs) with quantum efficiency close to the theoretical maximum were achieved by utilizing a double-layer architecture. Two wide-triplet-gap materials, 1,3-bis(9-carbazolyl)benzene and 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, were employed in the emitting and electron-transport layers respectively. The opposite carrier-transport characteristics of these two materials were leveraged to define the exciton formation zone and thus increase the probability of recombination. The efficiency at practical luminance (100 cd/m{sup 2}) was as high as 20.8%, 47.7 cd/A and 31.2 lm/W, respectively. Furthermore, based on the design concept of this simplified architecture, efficient warmish-white PhOLEDs were developed. Such two-component white organic light-emitting devices exhibited rather stable colors over a wide brightness range and yielded electroluminescence efficiencies of 15.3%, 33.3 cd/A, and 22.7 lm/W in the forward directions.

  18. A Traffic Prediction Algorithm for Street Lighting Control Efficiency

    Directory of Open Access Journals (Sweden)

    POPA Valentin

    2013-01-01

    Full Text Available This paper presents the development of a traffic prediction algorithm that can be integrated in a street lighting monitoring and control system. The prediction algorithm must enable the reduction of energy costs and improve energy efficiency by decreasing the light intensity depending on the traffic level. The algorithm analyses and processes the information received at the command center based on the traffic level at different moments. The data is collected by means of the Doppler vehicle detection sensors integrated within the system. Thus, two methods are used for the implementation of the algorithm: a neural network and a k-NN (k-Nearest Neighbor prediction algorithm. For 500 training cycles, the mean square error of the neural network is 9.766 and for 500.000 training cycles the error amounts to 0.877. In case of the k-NN algorithm the error increases from 8.24 for k=5 to 12.27 for a number of 50 neighbors. In terms of a root means square error parameter, the use of a neural network ensures the highest performance level and can be integrated in a street lighting control system.

  19. Silicon-Light: a European FP7 Project Aiming at High Efficiency Thin Film Silicon Solar Cells on Foil

    DEFF Research Database (Denmark)

    Soppe, W.; Haug, F.-J.; Couty, P.

    2011-01-01

    Silicon-Light is a European FP7 project, which started January 1st, 2010 and aims at development of low cost, high-efficiency thin film silicon solar cells on foil. Three main routes are explored to achieve these goals: a) advanced light trapping by implementing nanotexturization through UV Nano...... calculations of ideal nanotextures for light trapping in thin film silicon solar cells; the fabrication of masters and the replication and roll-to-roll fabrication of these nanotextures. Further, results on ITO variants with improved work function are presented. Finally, the status of cell fabrication on foils...... with nanotexture is shown. Microcrystalline and amorphous silicon single junction cells with stable efficiencies with more than 8 % have been made, paving the way towards a-Si/ c-Si tandem cells with more than 11% efficiency....

  20. Inkjet-Printed Quantum Dot Light-Emitting Diodes with an Air-Stable Hole Transport Material.

    Science.gov (United States)

    Xing, Zhenhua; Zhuang, Jinyong; Wei, Changting; Zhang, Dongyu; Xie, Zhongzhi; Xu, Xiaoping; Ji, Shunjun; Tang, Jianxin; Su, Wenming; Cui, Zheng

    2017-05-17

    High-efficiency quantum dot light-emitting diodes (QLEDs) were fabricated using inkjet printing with a novel cross-linkable hole transport material N,N'-(9,9'-spirobi[fluorene]-2,7-diylbis[4,1-phenylene])bis(N-phenyl-4'-vinyl-[1,1'-biphenyl]-4-amine) (SDTF). The cross-linked SDTF film has excellent solvent resistance, high thermal stability, and the highest occupied molecular orbital (HOMO) level of -5.54 eV. The inkjet-printed SDTF film is very smooth and uniform, with roughness as low as 0.37 nm, which is comparable with that of the spin-coated film (0.28 nm). The SDTF films stayed stable without any pinhole or grain even after 2 months in air. All-solution-processed QLEDs were fabricated; the maximum external quantum efficiency of 5.54% was achieved with the inkjet-printed SDTF in air, which is comparable to that of the spin-coated SDTF in a glove box (5.33%). Electrical stabilities of both spin-coated and inkjet-printed SDTF at the device level were also investigated and both showed a similar lifetime. The study demonstrated that SDTF is very promising as a printable hole transport material for making QLEDs using inkjet printing.

  1. Stable kilohertz spark discharges for high-efficiency conversion of methane to hydrogen and acetylene

    International Nuclear Information System (INIS)

    Li Xiaosong; Xu Yong; Wang Younian; Zhu Aimin; Lin Cankun; Shi Chuan

    2008-01-01

    Stable kilohertz spark discharges with a unique waveform of discharge current were studied for high-efficiency conversion of methane to hydrogen and acetylene at atmospheric pressure for the first time. Discharge stability was confirmed by the concentration variation in the product streams with 220 min discharge time using pure methane as the feed gas. Utilizing the stable kilohertz spark discharges, the hydrogen concentration in the product stream could be as high as 72.1 vol% at an energy cost of 6.7 eV per H 2 molecule produced and 81.5% of methane conversion. The acetylene concentration could reach 18.4 vol% at an energy cost of 21.2 eV per C 2 H 2 molecule produced and 70.3% of methane conversion. For methane conversion ranging from 51.9% to 81.5%, the energy costs were 6.6-10.7 eV per CH 4 molecule converted, 4.4-6.7 eV per H 2 molecule produced and 16.9-27.6 eV per C 2 H 2 molecule produced. This study showed the high-concentration production of CO x -free hydrogen and acetylene from methane at a low energy cost by stable kilohertz spark discharges

  2. Stable water use efficiency under climate change of three sympatric conifer species at the Alpine treeline

    Directory of Open Access Journals (Sweden)

    Gerhard eWieser

    2016-06-01

    Full Text Available The ability of treeline associated conifers in the Central Alps to cope with recent climate warming and increasing CO2 concentration is still poorly understood. We determined tree ring stable carbon and oxygen isotope ratios of Pinus cembra, Picea abies and Larix decidua trees from 1975-2010. Stable isotope ratios were compared with leaf level gas exchange measurements carried out in situ between 1979 and 2007. Results indicate that tree ring derived intrinsic water-use efficiency (iWUE of P. cembra, P. abies and L. decidua remained constant during the last 36 years despite climate warming and rising atmospheric CO2. Temporal patterns in Δ13C and Δ18O mirrored leaf level gas exchange assessments, suggesting parallel increases of CO2-fixation and stomatal conductance of treeline conifer species. As at the study site soil water availability was not a limiting factor iWUE remained largely stable throughout the study period. The stability in iWUE was accompanied by an increase in basal area increment (BAI suggesting that treeline trees benefit from both recent climate warming and CO2 fertilization. Finally, our results suggest that iWUE may not change species composition at treeline in the Austrian Alps due to similar ecophysiological responses to climatic changes of the three sympatric study species.

  3. Stable Water Use Efficiency under Climate Change of Three Sympatric Conifer Species at the Alpine Treeline.

    Science.gov (United States)

    Wieser, Gerhard; Oberhuber, Walter; Gruber, Andreas; Leo, Marco; Matyssek, Rainer; Grams, Thorsten Erhard Edgar

    2016-01-01

    The ability of treeline associated conifers in the Central Alps to cope with recent climate warming and increasing CO2 concentration is still poorly understood. We determined tree ring stable carbon and oxygen isotope ratios of Pinus cembra, Picea abies, and Larix decidua trees from 1975 to 2010. Stable isotope ratios were compared with leaf level gas exchange measurements carried out in situ between 1979 and 2007. Results indicate that tree ring derived intrinsic water-use efficiency (iWUE) of P. cembra, P. abies and L. decidua remained constant during the last 36 years despite climate warming and rising atmospheric CO2. Temporal patterns in Δ(13)C and Δ(18)O mirrored leaf level gas exchange assessments, suggesting parallel increases of CO2-fixation and stomatal conductance of treeline conifer species. As at the study site soil water availability was not a limiting factor iWUE remained largely stable throughout the study period. The stability in iWUE was accompanied by an increase in basal area increment (BAI) suggesting that treeline trees benefit from both recent climate warming and CO2 fertilization. Finally, our results suggest that iWUE may not change species composition at treeline in the Austrian Alps due to similar ecophysiological responses to climatic changes of the three sympatric study species.

  4. Atomic Layer Deposited Corrosion Protection: A Path to Stable and Efficient Photoelectrochemical Cells.

    Science.gov (United States)

    Scheuermann, Andrew G; McIntyre, Paul C

    2016-07-21

    A fundamental challenge in developing photoelectrochemical cells for the renewable production of solar chemicals and fuels is the simultaneous requirement of efficient light absorption and robust stability under corrosive conditions. Schemes for corrosion protection of semiconductor photoelectrodes such as silicon using deposited layers were proposed and attempted for several decades, but increased operational lifetimes were either insufficient or the resulting penalties for device efficiency were prohibitive. In recent years, advances in atomic layer deposition (ALD) of thin coatings have made novel materials engineering possible, leading to substantial and simultaneous improvements in stability and efficiency of photoelectrochemical cells. The self-limiting, layer-by-layer growth of ALD makes thin films with low pinhole densities possible and may also provide a path to defect control that can generalize this protection technology to a large set of materials necessary to fully realize photoelectrochemical cell technology for artificial photosynthesis.

  5. Gravity Waves and Wind-Farm Efficiency in Neutral and Stable Conditions

    Science.gov (United States)

    Allaerts, Dries; Meyers, Johan

    2018-02-01

    We use large-eddy simulations (LES) to investigate the impact of stable stratification on gravity-wave excitation and energy extraction in a large wind farm. To this end, the development of an equilibrium conventionally neutral boundary layer into a stable boundary layer over a period of 8 h is considered, using two different cooling rates. We find that turbulence decay has considerable influence on the energy extraction at the beginning of the boundary-layer transition, but afterwards, energy extraction is dominated by geometrical and jet effects induced by an inertial oscillation. It is further shown that the inertial oscillation enhances gravity-wave excitation. By comparing LES results with a simple one-dimensional model, we show that this is related to an interplay between wind-farm drag, variations in the Froude number and the dispersive effects of vertically-propagating gravity waves. We further find that the pressure gradients induced by gravity waves lead to significant upstream flow deceleration, reducing the average turbine output compared to a turbine in isolated operation. This leads us to the definition of a non-local wind-farm efficiency, next to a more standard wind-farm wake efficiency, and we show that both can be of the same order of magnitude. Finally, an energy flux analysis is performed to further elucidate the effect of gravity waves on the flow in the wind farm.

  6. Smooth muscle myosin light chain kinase efficiently phosphorylates serine 15 of cardiac myosin regulatory light chain

    Energy Technology Data Exchange (ETDEWEB)

    Josephson, Matthew P.; Sikkink, Laura A. [Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905 (United States); Penheiter, Alan R. [Molecular Medicine Program, Mayo Clinic, Rochester, MN 55905 (United States); Burghardt, Thomas P., E-mail: burghardt@mayo.edu [Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905 (United States); Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN 55905 (United States); Ajtai, Katalin [Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905 (United States)

    2011-12-16

    Highlights: Black-Right-Pointing-Pointer Cardiac myosin regulatory light chain (MYL2) is phosphorylated at S15. Black-Right-Pointing-Pointer Smooth muscle myosin light chain kinase (smMLCK) is a ubiquitous kinase. Black-Right-Pointing-Pointer It is a widely believed that MYL2 is a poor substrate for smMLCK. Black-Right-Pointing-Pointer In fact, smMLCK efficiently and rapidly phosphorylates S15 in MYL2. Black-Right-Pointing-Pointer Phosphorylation kinetics measured by novel fluorescence method without radioactivity. -- Abstract: Specific phosphorylation of the human ventricular cardiac myosin regulatory light chain (MYL2) modifies the protein at S15. This modification affects MYL2 secondary structure and modulates the Ca{sup 2+} sensitivity of contraction in cardiac tissue. Smooth muscle myosin light chain kinase (smMLCK) is a ubiquitous kinase prevalent in uterus and present in other contracting tissues including cardiac muscle. The recombinant 130 kDa (short) smMLCK phosphorylated S15 in MYL2 in vitro. Specific modification of S15 was verified using the direct detection of the phospho group on S15 with mass spectrometry. SmMLCK also specifically phosphorylated myosin regulatory light chain S15 in porcine ventricular myosin and chicken gizzard smooth muscle myosin (S20 in smooth muscle) but failed to phosphorylate the myosin regulatory light chain in rabbit skeletal myosin. Phosphorylation kinetics, measured using a novel fluorescence method eliminating the use of radioactive isotopes, indicates similar Michaelis-Menten V{sub max} and K{sub M} for regulatory light chain S15 phosphorylation rates in MYL2, porcine ventricular myosin, and chicken gizzard myosin. These data demonstrate that smMLCK is a specific and efficient kinase for the in vitro phosphorylation of MYL2, cardiac, and smooth muscle myosin. Whether smMLCK plays a role in cardiac muscle regulation or response to a disease causing stimulus is unclear but it should be considered a potentially significant

  7. High-Efficiency and Stable Organic Solar Cells Enabled by Dual Cathode Buffer Layers.

    Science.gov (United States)

    Huai, Zhaoxiang; Wang, Lixin; Sun, Yansheng; Fan, Rui; Huang, Shahua; Zhao, Xiaohui; Li, Xiaowei; Fu, Guangsheng; Yang, Shaopeng

    2018-02-14

    Various cathode interface materials have been used in organic solar cells (OSCs) to realize high performance. However, most cathode interface materials have their respective weaknesses in maximizing the efficiency or stability of OSCs. Herein, three kinds of alcohol-soluble cathode interfacial materials are combined with bathocuproine (BCP) to serve as multifunctional bilayer cathode buffers for the regular OSCs, and thus greatly enhanced power conversion efficiencies over 10.11% and significantly improved device stability have been achieved. By utilizing double interlayers, both light absorption and light distribution in active layer are improved. Furthermore, double interlayers offer favorable energy-level alignment, alcohol treatment, and duplicate protection of active layer, resulting in significantly reduced leakage current, suppressed recombination, and efficient charge collection. The improved device stability is related to the blocking effect of the complex formed between BCP and the metal electrode and the additional protection effect of the underlying alcohol-soluble materials. In view of the universal use of alcohol-soluble organic electrolyte as cathode buffer layers and by courtesy of the superiority of the double cathode layers relative to the monolayer controls, the double interlayer strategy demonstrated here opens a new way to fully exploiting the potential of OSCs and is believed to be extended to a wider application.

  8. Quantifying soil moisture impacts on light use efficiency across biomes.

    Science.gov (United States)

    Stocker, Benjamin D; Zscheischler, Jakob; Keenan, Trevor F; Prentice, I Colin; Peñuelas, Josep; Seneviratne, Sonia I

    2018-03-31

    Terrestrial primary productivity and carbon cycle impacts of droughts are commonly quantified using vapour pressure deficit (VPD) data and remotely sensed greenness, without accounting for soil moisture. However, soil moisture limitation is known to strongly affect plant physiology. Here, we investigate light use efficiency, the ratio of gross primary productivity (GPP) to absorbed light. We derive its fractional reduction due to soil moisture (fLUE), separated from VPD and greenness changes, using artificial neural networks trained on eddy covariance data, multiple soil moisture datasets and remotely sensed greenness. This reveals substantial impacts of soil moisture alone that reduce GPP by up to 40% at sites located in sub-humid, semi-arid or arid regions. For sites in relatively moist climates, we find, paradoxically, a muted fLUE response to drying soil, but reduced fLUE under wet conditions. fLUE identifies substantial drought impacts that are not captured when relying solely on VPD and greenness changes and, when seasonally recurring, are missed by traditional, anomaly-based drought indices. Counter to common assumptions, fLUE reductions are largest in drought-deciduous vegetation, including grasslands. Our results highlight the necessity to account for soil moisture limitation in terrestrial primary productivity data products, especially for drought-related assessments. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

  9. Compositionally Graded Absorber for Efficient and Stable Near-Infrared-Transparent Perovskite Solar Cells.

    Science.gov (United States)

    Fu, Fan; Pisoni, Stefano; Weiss, Thomas P; Feurer, Thomas; Wäckerlin, Aneliia; Fuchs, Peter; Nishiwaki, Shiro; Zortea, Lukas; Tiwari, Ayodhya N; Buecheler, Stephan

    2018-03-01

    Compositional grading has been widely exploited in highly efficient Cu(In,Ga)Se 2 , CdTe, GaAs, quantum dot solar cells, and this strategy has the potential to improve the performance of emerging perovskite solar cells. However, realizing and maintaining compositionally graded perovskite absorber from solution processing is challenging. Moreover, the operational stability of graded perovskite solar cells under long-term heat/light soaking has not been demonstrated. In this study, a facile partial ion-exchange approach is reported to achieve compositionally graded perovskite absorber layers. Incorporating compositional grading improves charge collection and suppresses interface recombination, enabling to fabricate near-infrared-transparent perovskite solar cells with power conversion efficiency of 16.8% in substrate configuration, and demonstrate 22.7% tandem efficiency with 3.3% absolute gain when mechanically stacked on a Cu(In,Ga)Se 2 bottom cell. Non-encapsulated graded perovskite device retains over 93% of its initial efficiency after 1000 h operation at maximum power point at 60 °C under equivalent 1 sun illumination. The results open an avenue in exploring partial ion-exchange to design graded perovskite solar cells with improved efficiency and stability.

  10. The novel stable control scheme of the light source power in the closed-loop fiber optic gyroscope

    Energy Technology Data Exchange (ETDEWEB)

    Ji Zhongxiao [Graduate University of the Chinese Academy of Sciences, Beijing (China); Ma Caiwen, E-mail: jzx@opt.ac.cn [Xi' an Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences, NO.17 Xinxi Road, New Industrial Park, Xi' an Hi-Tech Industrial Development Zone, Xi' an, Shaanxi (China)

    2011-02-01

    The light source power stability of the Fiber-Optic Gyroscope (FOG) affects directly the scale factor and bias stability of FOG. The typical control scheme of the light source power employs an additional photodetector to detect the output power of the light source. When the fiber loss of FOG varied due to the temperature change, the light power in the additional photodetector did not indicate this change, which decreased the control effect. The spike pulse overlapping on the gyro signal denotes potentially the change of the light power and fiber loss. In the novel scheme, the spike pulse is extracted from the gyro signal, and is transformed into the square wave by the differential circuit. According to the change of the square wave amplitude, FOG adjusts the bias current of the light source to keep the stable light power in the signal photodetector. It is a simple and low-cost scheme without an additional photodetector.

  11. Results of the application of stable isotopes of light elements in geology and hydrology

    International Nuclear Information System (INIS)

    Jovan, Zoto

    2003-01-01

    Stable isotopes of light elements are used for studies in the fields of geology, agriculture, hydrogeology, hydrology, precipitation and geology of petroleum in our country. The results concerning application in geology and hydrology are presented. A - Determination of absolute geological age is very important for geological studies. There are several determination methods, but, for some specific analytical problems the potassium - argon method was used. The 40 K content of the monomineral geological sample is calculated from the content of K in the sample determined by the flame photometer. The 40 Ar content is determined by mass spectrometry. The results of our determination lie between 23.7 x 10 6 - 446.2 x 10 6 years and are in good correlation with the geological evaluations and in good agreement with the determinations of other laboratories. B - The stable isotopes of hydrogen and oxygen are used in the hydrologic studies in our country, but more interesting is the study of underground connection between Prespa and Ohrid lakes. Prespa and Ohrid lakes are in the East part of Albania at the border between Albania - Greece - Fyr. of Macedonia. The altitudes of Prespa and Ohrid lakes are 850 m and 690 m, respectively and between the lakes there are Mali I Thate and Galitcica mountains. On the side of Ohrid lake there are two big springs, Tushemishti in Albania territory and Sveti Naum in Fyr. of Macedonia territory. According to our data regarding δ 18 O and δ 2 H, an underground connection exists between Prespa lake and the big springs at the side of lake Ohrid. (author)

  12. The Physics of Small Molecule Acceptors for Efficient and Stable Bulk Heterojunction Solar Cells

    KAUST Repository

    Gasparini, Nicola

    2018-01-29

    Organic bulk heterojunction solar cells based on small molecule acceptors have recently seen a rapid rise in the power conversion efficiency with values exceeding 13%. This impressive achievement has been obtained by simultaneous reduction of voltage and charge recombination losses within this class of materials as compared to fullerene-based solar cells. In this contribution, the authors review the current understanding of the relevant photophysical processes in highly efficient nonfullerene acceptor (NFA) small molecules. Charge generation, recombination, and charge transport is discussed in comparison to fullerene-based composites. Finally, the authors review the superior light and thermal stability of nonfullerene small molecule acceptor based solar cells, and highlight the importance of NFA-based composites that enable devices without early performance loss, thus resembling so-called burn-in free devices.

  13. How Stable is a Light Sail Riding on a Laser Beam?

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    The Breakthrough Starshot Initiative made headlines last year when the plan was first announced to send tiny spacecraft to our nearest stellar neighbors. But just how feasible is this initiative? A new study looks at just one aspect of this plan: whether we can propel the spacecraft successfully.Propelling a FleetThe Alpha Centauri star system, which consists of Alpha (left) and Beta (right) Centauri as well as Proxima Centauri (circled). [Skatebiker]The goal behind the Breakthrough Starshot Initiative is to build a fleet of tiny, gram-scale spacecraft to travel to the Alpha Centauri star system a systemin whicha planet was recently discovered around Proxima Centauri, the star nearest to us.To propel the spacecraft, the team plans to attach a reflective sail to each one. When a high-power laser beam is pointed at that sail from Earth, the impulse of the photons bouncing off the sail can acceleratethe lightweight spacecraft to a decent fraction of the speed of light, allowing it to reach the Alpha Centauri system within decades.Among the many potential engineering challenges forsuch a mission, one interesting one is examined in a recent study by Zachary Manchester and Avi Loeb of Harvard University: how do wekeep the spacecrafts light sail centered on the laser beam long enough to accelerate it?Beam profile (left) and corresponding potential function (right) for a laser beam made up of four Gaussians. With this configuration, the potential well pushes the spacecraft back to the center if it drifts toward the edges of the well. [Manchester Loeb 2017]The Search for StabilityManchester and Loeb arguethat any slight perturbations to the light sails position relative to the laser beam in the form of random disturbances, misalignments, or manufacturing imperfections could cause it to slide off the beam, preventing it from continuing toaccelerate. Ideally, the project would use a sail that could be passively stable: the sail wants to stay centered on the beam, rather than

  14. Highly Efficient, Selective, and Stable CO2 Electroreduction on a Hexagonal Zn Catalyst.

    Science.gov (United States)

    Won, Da Hye; Shin, Hyeyoung; Koh, Jaekang; Chung, Jaehoon; Lee, Hee Sang; Kim, Hyungjun; Woo, Seong Ihl

    2016-08-01

    Electrocatalytic CO2 conversion into fuel is a prospective strategy for the sustainable energy production. However, still many parts of the catalyst such as low catalytic activity, selectivity, and stability are challenging. Herein, a hierarchical hexagonal Zn catalyst showed highly efficient and, more importantly, stable performance as an electrocatalyst for selectively producing CO. Moreover, we found that its high selectivity for CO is attributed to morphology. In electrochemical analysis, Zn (101) facet is favorable to CO formation whereas Zn (002) facet favors the H2 evolution during CO2 electrolysis. Indeed, DFT calculations showed that (101) facet lowers a reduction potential for CO2 to CO by more effectively stabilizing a (.) COOH intermediate than (002) facet. This further suggests that tuning the crystal structure to control (101)/(002) facet ratio of Zn can be considered as a key design principle to achieve a desirable product from Zn catalyst. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Determining metal assimilation efficiency in aquatic invertebrates using enriched stable metal isotope tracers

    International Nuclear Information System (INIS)

    Croteau, Marie-Noele; Luoma, Samuel N.; Pellet, Bastien

    2007-01-01

    We employ a novel approach that combines pulse-chase feeding and multi-labelled stable isotopes to determine gut passage time (GPT), gut retention time (GRT), food ingestion rate (IR) and assimilation efficiency (AE) of three trace elements for a freshwater gastropod. Lettuce isotopically enriched in 53 Cr, 65 Cu and 106 Cd was fed for 2 h to Lymnaea stagnalis. The release of tracers in feces and water was monitored for 48 h, during which unlabelled lettuce was provided ad libidum. The first defecation of 53 Cr occurred after 5 h of depuration (GPT), whereas 90% of the ingested 53 Cr was recovered in the feces after 22.5 h of depuration (GRT). 53 Chromium was not significantly accumulated in the soft tissues upon exposure. In contrast, 65 Cu and 106 Cd assimilation was detectable for most experimental snails, i.e., 65/63 Cu and 106/114 Cd ratios in exposed snails were higher than those for controls. Food IR during the labelled feeding phase was 0.16 ± 0.07 g g -1 d -1 . IR was inferred from the amount of 53 Cr egested in the feces during depuration and the concentration of 53 Cr in the labelled lettuce. Assimilation efficiencies (±95% CI) determined using mass balance calculations were 84 ± 4% for Cu and 85 ± 3% for Cd. The ratio method yields similar AE estimates. Expanding the application of this novel stable isotope tracer technique to other metals in a wide variety of species will provide unique opportunities to evaluate the interplay between digestive processes and dietary influx of metals. Understanding the biological processes that modulate dietborne metal uptake is crucial to assess the toxicity of dietborne metals

  16. Treatment for stable HIV patients in England: can we increase efficiency and improve patient care?

    Science.gov (United States)

    Adams, Elisabeth; Ogden, David; Ehrlich, Alice; Hay, Phillip

    2014-07-01

    To estimate the costs and potential efficiency gains of changing the frequency of clinic appointments and drug dispensing arrangements for stable HIV patients compared to the costs of hospital pharmacy dispensing and home delivery. We estimated the annual costs per patient (HIV clinic visits and either first-line treatment or a common second-line regimen, with some patients switching to a second-line regimen during the year). The cost of three-, four- and six-monthly clinic appointments and drug supply was estimated assuming hospital dispensing (incurring value-added tax) and home delivery. Three-monthly appointments and hospital drug dispensing (baseline) were compared to other strategies. The baseline was the most costly option (£10,587 if first-line treatment and no switch to second-line regimen). Moving to six-monthly appointments and home delivery yielded savings of £1883 per patient annually. Assuming patients start on different regimens and may switch to second-line therapies, six-monthly appointments and three-monthly home delivery of drugs is the least expensive option and could result in nearly £2000 savings per patient. This translates to annual cost reduction of about £8 million for the estimated 4000 eligible patients not currently on home delivery in London, England. Different appointment schedules and drug supply options should be considered for stable HIV patients based on efficiency gains. However, this should be assessed for individual patients to meet their needs, especially around adherence and patient support. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  17. Donor-Acceptor Interface Stabilizer Based on Fullerene Derivatives toward Efficient and Thermal Stable Organic Photovoltaics.

    Science.gov (United States)

    Li, Junli; Zhu, Xiaoguang; Yuan, Tao; Shen, Jiulin; Liu, Jikang; Zhang, Jian; Tu, Guoli

    2017-02-22

    An interface stabilizer based on alkylation-functionalized fullerene derivatives, [6, 6]-Phenyl-C61-butyric acid (3,5-bis(octyloxy)phenyl)methyl ester (PCB-C8oc), was successfully synthesized and applied for the active layer of Organic Photovoltaics (OPVs). The PCB-C8oc can replace part of the phenyl-C61-buty-ric acid methyl ester (PCBM) and be distributed on the interface of poly(3-hexylthiophene) (P3HT) and PCBM to form P3HT/PCBM/PCB-C8oc ternary blends, leading to thermally stable and efficient organic photovoltaics. The octyl groups of PCB-C8oc exhibit intermolecular interaction with the hexyl groups of P3HT, and the fullerene unit of PCB-C8oc are in tight contact with PCBM. The dual functions of PCB-C8oc will inhibit the phase separation between electron donor and acceptor, thereby improving the stability of devices under long-time thermal annealing at high temperature. When doped with 10 wt % PCB-C8oc, the power conversion efficiency (PCE) of the P3HT system decreased from 3.54% to 2.88% after 48 h of thermal treatment at 150 °C, whereas the PCE of the reference device without PCB-C8oc dramatically dropped from 3.53% to 0.73%. When doping 10 or 20 wt % PCB-C8oc, the unannealed P3HT/PCBM/PCB-C8oc device achieved a higher PCE than the P3HT/PCBM device without any annealing following the same fabricating condition. For the PTB7/PCBM-based devices, after adding only 5 wt % PCB-C8oc, the OPVs also exhibited thermally stable morphology and better device performances. All these results demonstrate that the utilization of alkyl interchain interactions is an effective and practical strategy to control morphological evolution.

  18. Highly polarized light from stable ordered magnetic fields in GRB 120308A.

    Science.gov (United States)

    Mundell, C G; Kopač, D; Arnold, D M; Steele, I A; Gomboc, A; Kobayashi, S; Harrison, R M; Smith, R J; Guidorzi, C; Virgili, F J; Melandri, A; Japelj, J

    2013-12-05

    After the initial burst of γ-rays that defines a γ-ray burst (GRB), expanding ejecta collide with the circumburst medium and begin to decelerate at the onset of the afterglow, during which a forward shock travels outwards and a reverse shock propagates backwards into the oncoming collimated flow, or 'jet'. Light from the reverse shock should be highly polarized if the jet's magnetic field is globally ordered and advected from the central engine, with a position angle that is predicted to remain stable in magnetized baryonic jet models or vary randomly with time if the field is produced locally by plasma or magnetohydrodynamic instabilities. Degrees of linear polarization of P ≈ 10 per cent in the optical band have previously been detected in the early afterglow, but the lack of temporal measurements prevented definitive tests of competing jet models. Hours to days after the γ-ray burst, polarization levels are low (P GRBs contain magnetized baryonic jets with large-scale uniform fields that can survive long after the initial explosion.

  19. Efficient estimation of energy transfer efficiency in light-harvesting complexes.

    Science.gov (United States)

    Shabani, A; Mohseni, M; Rabitz, H; Lloyd, S

    2012-07-01

    The fundamental physical mechanisms of energy transfer in photosynthetic complexes is not yet fully understood. In particular, the degree of efficiency or sensitivity of these systems for energy transfer is not known given their realistic with surrounding photonic and phononic environments. One major problem in studying light-harvesting complexes has been the lack of an efficient method for simulation of their dynamics in biological environments. To this end, here we revisit the second order time-convolution (TC2) master equation and examine its reliability beyond extreme Markovian and perturbative limits. In particular, we present a derivation of TC2 without making the usual weak system-bath coupling assumption. Using this equation, we explore the long-time behavior of exciton dynamics of Fenna-Matthews-Olson (FMO) portein complex. Moreover, we introduce a constructive error analysis to estimate the accuracy of TC2 equation in calculating energy transfer efficiency, exhibiting reliable performance for system-bath interactions with weak and intermediate memory and strength. Furthermore, we numerically show that energy transfer efficiency is optimal and robust for the FMO protein complex of green sulfur bacteria with respect to variations in reorganization energy and bath correlation time scales.

  20. On the efficiency of stochastic volume sources for the determination of light meson masses

    CERN Document Server

    Endress, E; Wittig, H

    2011-01-01

    We investigate the efficiency of single timeslice stochastic sources for the calculation of light meson masses on the lattice as one varies the quark mass. Simulations are carried out with Nf = 2 flavours of non-perturbatively O(a) improved Wilson fermions for pion masses in the range of 450 - 760 MeV. Results for pseudoscalar and vector meson two-point correlation functions computed using stochastic as well as point sources are presented and compared. At fixed computational cost the stochastic approach reduces the variance considerably in the pseudoscalar channel for all simulated quark masses. The vector channel is more affected by the intrinsic stochastic noise. In order to obtain stable estimates of the statistical errors and a more pronounced plateau for the effective vector meson mass, a relatively large number of stochastic sources must be used.

  1. Influence of emissive hole-transporting materials on the electrical and luminescent performance of highly efficient white light organic light-emitting diodes

    Science.gov (United States)

    Wang, Ching-Wu; Chen, Shih-Fang; Kuo, Wen-Fa

    2002-09-01

    An emissive hole-transporting material with a dopant was proposed for realizing highly efficient and relatively pure white-light organic light-emitting diode (OLED). The device structure included ITO/N, N'-diphenyl-N, N'-bis(1-naphthyl-phenyl)-(1, 1'-biphenyl)-4,4'-diamine (NPB)/NPB doped with 4-Dicyanomethylene-2-methyl-6-[2, 3, 6, 7-tetra-hydro-1H, 5H-behzo[ij]-quinolizin-8-yl)vinyl]-4H-pyran (DCM2) (NPB:DCM2)/bathocuproine (BCP)/tris-(8-hydroxyquinoline) aluminum (Alq3)/Mg/Ag. By appropriately controlling the DCM2 doping concentration as well as thickness of the blue-red-emitting layer of NPB:DCM2, the white-light OLED has a relatively stable white color even the operating voltages change from 9 to 18 V.

  2. WO3/Conducting Polymer Heterojunction Photoanodes for Efficient and Stable Photoelectrochemical Water Splitting.

    Science.gov (United States)

    Jeon, Dasom; Kim, Nayeong; Bae, Sanghyun; Han, Yujin; Ryu, Jungki

    2018-02-26

    An efficient and stable heterojunction photoanode for solar water oxidation was fabricated by hybridization of WO 3 and conducting polymers (CPs). Organic/inorganic hybrid photoanodes were readily prepared by the electropolymerization of various CPs and the codeposition of tetraruthenium polyoxometalate (Ru 4 POM) water-oxidation catalysts (WOCs) on the surface of WO 3 . The deposition of CPs, especially polypyrrole (PPy) doped with Ru 4 POM (PPy:Ru 4 POM), resulted in a remarkably improved photoelectrochemical performance by the formation of a WO 3 /PPy p-n heterojunction and the incorporation of efficient Ru 4 POM WOCs. In addition, there was also a significant improvement in the photostability of the WO 3 -based photoanode after the deposition of the PPy:Ru 4 POM layer due to the suppression of the formation of hydrogen peroxide, which was responsible for corrosion. This study provides insight into the design and fabrication of novel photosynthetic and photocatalytic systems with excellent performance and stability through the hybridization of organic and inorganic materials.

  3. Accurate, stable and efficient Navier-Stokes solvers based on explicit treatment of the pressure term

    International Nuclear Information System (INIS)

    Johnston, Hans; Liu Jianguo

    2004-01-01

    We present numerical schemes for the incompressible Navier-Stokes equations based on a primitive variable formulation in which the incompressibility constraint has been replaced by a pressure Poisson equation. The pressure is treated explicitly in time, completely decoupling the computation of the momentum and kinematic equations. The result is a class of extremely efficient Navier-Stokes solvers. Full time accuracy is achieved for all flow variables. The key to the schemes is a Neumann boundary condition for the pressure Poisson equation which enforces the incompressibility condition for the velocity field. Irrespective of explicit or implicit time discretization of the viscous term in the momentum equation the explicit time discretization of the pressure term does not affect the time step constraint. Indeed, we prove unconditional stability of the new formulation for the Stokes equation with explicit treatment of the pressure term and first or second order implicit treatment of the viscous term. Systematic numerical experiments for the full Navier-Stokes equations indicate that a second order implicit time discretization of the viscous term, with the pressure and convective terms treated explicitly, is stable under the standard CFL condition. Additionally, various numerical examples are presented, including both implicit and explicit time discretizations, using spectral and finite difference spatial discretizations, demonstrating the accuracy, flexibility and efficiency of this class of schemes. In particular, a Galerkin formulation is presented requiring only C 0 elements to implement

  4. Stable high efficiency two-dimensional perovskite solar cells via cesium doping

    KAUST Repository

    Zhang, Xu

    2017-08-15

    Two-dimensional (2D) organic-inorganic perovskites have recently emerged as one of the most important thin-film solar cell materials owing to their excellent environmental stability. The remaining major pitfall is their relatively poor photovoltaic performance in contrast to 3D perovskites. In this work we demonstrate cesium cation (Cs) doped 2D (BA)(MA)PbI perovskite solar cells giving a power conversion efficiency (PCE) as high as 13.7%, the highest among the reported 2D devices, with excellent humidity resistance. The enhanced efficiency from 12.3% (without Cs) to 13.7% (with 5% Cs) is attributed to perfectly controlled crystal orientation, an increased grain size of the 2D planes, superior surface quality, reduced trap-state density, enhanced charge-carrier mobility and charge-transfer kinetics. Surprisingly, it is found that the Cs doping yields superior stability for the 2D perovskite solar cells when subjected to a high humidity environment without encapsulation. The device doped using 5% Cs degrades only ca. 10% after 1400 hours of exposure in 30% relative humidity (RH), and exhibits significantly improved stability under heating and high moisture environments. Our results provide an important step toward air-stable and fully printable low dimensional perovskites as a next-generation renewable energy source.

  5. Full phosphorescent white-light organic light-emitting diodes with improved color stability and efficiency by fine tuning primary emission contributions

    Energy Technology Data Exchange (ETDEWEB)

    Hua, Wang, E-mail: wmsu2008@sinano.ac.cn, E-mail: wanghua001@tyut.edu.cn; Du, Xiaogang [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan 030024 (China); Research Center of Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Su, Wenming, E-mail: wmsu2008@sinano.ac.cn, E-mail: wanghua001@tyut.edu.cn; Zhang, Dongyu [Printable Electronics Research Centre, Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, suzhou 215123 (China); Lin, Wenjing [Key Laboratory of Interface Science and Engineering in Advanced Materials, Taiyuan University of Technology, Ministry of Education, Taiyuan 030024 (China); Research Center of Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan 030024 (China); Printable Electronics Research Centre, Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, suzhou 215123 (China)

    2014-02-15

    In this paper, a novel type of white-light organic light emitting diode (OLED) with high color stability was reported, in which the yellow-light emission layer of (4,4{sup ′}-N,N{sup ′}-dicarbazole)biphenyl (CBP) : tris(2-phenylquinoline-C2,N{sup ′})iridium(III) (Ir(2-phq){sub 3}) was sandwiched by double blue-light emission layers of 1,1-bis-[(di-4-tolylamino)pheny1]cyclohexane (TAPC) : bis[4,6-(di-fluorophenyl)-pyridinato-N,C2{sup ′}]picolinate (FIrpic) and tris[3-(3-pyridyl)mesityl]borane (3TPYMB):FIrpic. And, it exhibited the maximum current efficiency of 33.1 cd/A, the turn-on voltage at about 3 V and the maximum luminance in excess of 20000 cd/m{sup 2}. More important, it realized very stable white-light emission, and its CIE(x, y) coordinates only shift from (0.34, 0.37) to (0.33, 0.37) as applied voltage increased from 5 V to 12 V. It is believed that the new scheme in emission layer of white-light OLED can fine tune the contribution of primary emission with applied voltage changed, resulting in high quality white-light OLED.

  6. High-throughput estimation of incident light, light interception and radiation-use efficiency of thousands of plants in a phenotyping platform.

    Science.gov (United States)

    Cabrera-Bosquet, Llorenç; Fournier, Christian; Brichet, Nicolas; Welcker, Claude; Suard, Benoît; Tardieu, François

    2016-10-01

    Light interception and radiation-use efficiency (RUE) are essential components of plant performance. Their genetic dissections require novel high-throughput phenotyping methods. We have developed a suite of methods to evaluate the spatial distribution of incident light, as experienced by hundreds of plants in a glasshouse, by simulating sunbeam trajectories through glasshouse structures every day of the year; the amount of light intercepted by maize (Zea mays) plants via a functional-structural model using three-dimensional (3D) reconstructions of each plant placed in a virtual scene reproducing the canopy in the glasshouse; and RUE, as the ratio of plant biomass to intercepted light. The spatial variation of direct and diffuse incident light in the glasshouse (up to 24%) was correctly predicted at the single-plant scale. Light interception largely varied between maize lines that differed in leaf angles (nearly stable between experiments) and area (highly variable between experiments). Estimated RUEs varied between maize lines, but were similar in two experiments with contrasting incident light. They closely correlated with measured gas exchanges. The methods proposed here identified reproducible traits that might be used in further field studies, thereby opening up the way for large-scale genetic analyses of the components of plant performance. © 2016 INRA New Phytologist © 2016 New Phytologist Trust.

  7. Full phosphorescent white-light organic light-emitting diodes with improved color stability and efficiency by fine tuning primary emission contributions

    International Nuclear Information System (INIS)

    Hua, Wang; Du, Xiaogang; Su, Wenming; Zhang, Dongyu; Lin, Wenjing

    2014-01-01

    In this paper, a novel type of white-light organic light emitting diode (OLED) with high color stability was reported, in which the yellow-light emission layer of (4,4 ′ -N,N ′ -dicarbazole)biphenyl (CBP) : tris(2-phenylquinoline-C2,N ′ )iridium(III) (Ir(2-phq) 3 ) was sandwiched by double blue-light emission layers of 1,1-bis-[(di-4-tolylamino)pheny1]cyclohexane (TAPC) : bis[4,6-(di-fluorophenyl)-pyridinato-N,C2 ′ ]picolinate (FIrpic) and tris[3-(3-pyridyl)mesityl]borane (3TPYMB):FIrpic. And, it exhibited the maximum current efficiency of 33.1 cd/A, the turn-on voltage at about 3 V and the maximum luminance in excess of 20000 cd/m 2 . More important, it realized very stable white-light emission, and its CIE(x, y) coordinates only shift from (0.34, 0.37) to (0.33, 0.37) as applied voltage increased from 5 V to 12 V. It is believed that the new scheme in emission layer of white-light OLED can fine tune the contribution of primary emission with applied voltage changed, resulting in high quality white-light OLED

  8. Timing growth and development of Campanula by daily light integral and supplemental light level in a cost-efficient light control system

    DEFF Research Database (Denmark)

    Kjaer, K. H.; Ottosen, Carl-Otto; Jorgensen, B. N.

    2012-01-01

    light control system (DynaLight desktop) automatically defines the most cost-efficient use of supplemental light based on predefined setpoints for daily photosynthesis integral (DPI), forecasted solar irradiance and the market price on electricity. It saves energy in high-cost periods of electricity......Two campanula species Campanula portenschlagiana ('Blue Get Mee') and Campanula cochlearifolia ('Blue Wonder') were grown in a cost-efficient light control system and the effect of supplemental light level and daily light integral (DLI) on growth and development was quantified. The alternative......, but creates irregular light periods which may disturb circadian rhythms and thereby affect plant growth and flower development. Plants were grown in four treatments controlled by DynaLight desktop with two setpoints for DPI (300 and 600 mmol m(-2) leaf day(-1)) and two levels of supplemental lighting (48...

  9. Parameterizing ecosystem light use efficiency and water use efficiency to estimate maize gross primary production and evapotranspiration using MODIS EVI

    Science.gov (United States)

    Quantifying global carbon and water balances requires accurate estimation of gross primary production (GPP) and evapotranspiration (ET), respectively, across space and time. Models that are based on the theory of light use efficiency (LUE) and water use efficiency (WUE) have emerged as efficient met...

  10. In situ photoactivated plasmonic Ag{sub 3}PO{sub 4}@silver as a stable catalyst with enhanced photocatalytic activity under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Dongfang; Wang, Jiaxun, E-mail: zdfbb66@aliyun.com [College of Science, Huazhong Agricultural University, Wuhan (China)

    2017-05-15

    Silver orthophosphate (Ag{sub 3}PO{sub 4}) had been reported as an excellent candidate to split water or decompose pollutants with high efficiency in visible light region, yet is not stable due to the reduction of silver ion. In this work, an easy-fabricated method (in situ photoinduced reduction) was provided to enhance the stability of Ag{sub 3}PO{sub 4} for its possible application as a visible-light sensitive photocatalyst. The as-prepared samples were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, photoluminescence spectra (PL) and Photoelectrochemical measurements. The Ag{sub 3}PO{sub 4}/Ag photocatalysts showed strong photocatalytic activity for decomposition of RhB dye or phenol-X-3B mixture under visible light irradiation (λ> 420 nm) and can be used repeatedly. The possible mechanism for the enhanced photocatalytic properties of the Ag{sub 3}PO{sub 4} /Ag hybrid was also discussed. It was found that •OH and holes take priority over •O{sub 2}{sup -} radicals in serving as the main oxidant in the Ag{sub 3}PO{sub 4}/Ag photocatalytic system. Especially, the experimental results indicate that the surface plasmon resonance of Ag nanoparticles and a large negative charge of PO{sub 4}{sup 3-} ions as well as high separation efficiency of {sup e-} --h{sup +} pairs, facilitated the enhancement of the photocatalytic activity of the Ag{sub 3} PO{sub 4} /Ag composite. The results indicated that Ag{sub 3} PO{sub 4} /Ag is an efficient and stable visible-light-driven photocatalyst. (author)

  11. Photosynthetic efficiency of Chlamydomonas reinhardtii in attenuated, flashing light

    NARCIS (Netherlands)

    Vejrazka, C.; Janssen, M.G.J.; Streefland, M.; Wijffels, R.H.

    2012-01-01

    As a result of mixing and light attenuation, algae in a photobioreactor (PBR) alternate between light and dark zones and, therefore, experience variations in photon flux density (PFD). These variations in PFD are called light/dark (L/D) cycles. The objective of this study was to determine how these

  12. Materials and architectures for efficient harvesting of singlet and triplet excitons for white light emitting OLEDs

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Mark E; Forrest, Stephen

    2015-02-03

    The present invention relates to organic light emitting devices (OLEDs), and more specifically to OLEDS that emit light using a combination of fluorescent emitters and phosphorescent emitters for the efficient utilization of all of the electrically generated excitons.

  13. Next Generation Luminaires: Recognizing Innovative, Energy-Efficient Commercial Lighting Luminaires

    Energy Technology Data Exchange (ETDEWEB)

    None

    2013-04-01

    Fact sheet that describes the Next Generation Luminaires SSL lighting design competition, which recognizes excellence in technical innovation and design of high-quality, energy-efficient commercial lighting, both indoor and outdoor.

  14. Copper Oxide Nanograss for Efficient and Stable Photoelectrochemical Hydrogen Production by Water Splitting

    Science.gov (United States)

    Borkar, Rajnikant; Dahake, Rashmi; Rayalu, Sadhana; Bansiwal, Amit

    2018-03-01

    A biphasic copper oxide thin film of grass-like appendage morphology is synthesized by two-step electro-deposition method and later investigated for photoelectrochemical (PEC) water splitting for hydrogen production. Further, the thin film was characterized by UV-Visible spectroscopy, x-ray diffraction (XRD), Scanning electron microscopy (SEM) and PEC techniques. The XRD analysis confirms formation of biphasic copper oxide phases, and SEM reveals high surface area grass appendage-like morphology. These grass appendage structures exhibit a high cathodic photocurrent of - 1.44 mAcm-2 at an applied bias of - 0.7 (versus Ag/AgCl) resulting in incident to photon current efficiency (IPCE) of ˜ 10% at 400 nm. The improved light harvesting and charge transport properties of grass appendage structured biphasic copper oxides makes it a potential candidate for PEC water splitting for hydrogen production.

  15. Wide field-of-view and high-efficiency light concentrator

    Science.gov (United States)

    Zhi, Yu; Liang, Ye; Wang, Zhe; Chen, Shaomin

    2018-03-01

    To improve light yield and energy resolution in large-volume neutrino detectors, light concentrators are often mounted on photomultiplier tubes to increase the detection efficiency of optical photons from scintillation or Cherenkov light induced by charged particles. We propose a method to optimize previous light concentrators design in order to attain a field of view of 90∘ and a geometrical collection efficiency above 98%. This improvement could be crucial to Jinping and other future neutrino experiments whichever it is applicable.

  16. Evaluation of the photon transmission efficiency of light guides used in scintillation detectors using LightTools code

    International Nuclear Information System (INIS)

    Park, Hye Min; Joo, Koan Sik; Kim, Jeong Ho; Kim, Dong Sung; Park, Ki Hyun; Park, Chan Jong; Han, Woo Jin

    2016-01-01

    To optimize the photon transmission efficiency of light guides used in scintillation detectors, LightTools code, which can construct and track light, was used to analyze photon transmission effectiveness with respect to light guides thickness. This analysis was carried out using the commercial light guide, N-BK 7 Optical Glass by SCHOTT, as a model for this study. The luminous exitance characteristic of the LYSO scintillator was used to analyze the photon transmission effectiveness according to the thickness of the light guide. The results of the simulations showed the effectiveness of the photon transmission according to the thickness of the light guide, which was found to be distributed from 13.38% to 33.57%. In addition, the photon transmission efficiency was found to be the highest for light guides of 4 mm of thickness and a receiving angle of 49 .deg. . Through such simulations, it is confirmed that photon transmission efficiency depends on light guide thickness and subsequent changes in the internal angle of reflection. The aim is to produce an actual light guide based on these results and to evaluate its performance

  17. Realistic Fasting Does Not Affect Stable Isotope Levels of a Metabolically Efficient Salamander

    Science.gov (United States)

    Stable isotopes are commonly used to examine various aspects of animal ecology. The use of stable isotopes generally proceeds under the implicit assumption that resource use is the only factor driving variation in stable isotope levels; however, a wealth of studies demonstrate a...

  18. Interfacial engineering of electron transport layer using Caesium Iodide for efficient and stable organic solar cells

    Science.gov (United States)

    Upama, Mushfika Baishakhi; Elumalai, Naveen Kumar; Mahmud, Md Arafat; Wright, Matthew; Wang, Dian; Xu, Cheng; Haque, Faiazul; Chan, Kah Howe; Uddin, Ashraf

    2017-09-01

    Polymer solar cells (PSCs) have gained immense research interest in the recent years predominantly due to low-cost, solution process-ability, and facile device fabrication. However, achieving high stability without compromising the power conversion efficiency (PCE) serves to be an important trade-off for commercialization. In line with this, we demonstrate the significance of incorporating a CsI/ZnO bilayer as electron transport layer (ETL) in the bulk heterojunction PSCs employing low band gap polymer (PTB7) and fullerene (PC71BM) as the photo-active layer. The devices with CsI/ZnO interlayer exhibited substantial enhancement of 800% and 12% in PCE when compared to the devices with pristine CsI and pristine ZnO as ETL, respectively. Furthermore, the UV and UV-ozone induced degradation studies revealed that the devices incorporating CsI/ZnO bilayer possess excellent decomposition stability (∼23% higher) over the devices with pristine ZnO counterparts. The incorporation of CsI between ITO and ZnO was found to favorably modify the energy-level alignment at the interface, contributing to the charge collection efficiency as well as protecting the adjacent light absorbing polymer layers from degradation. The mechanism behind the improvement in PCE and stability is analyzed using the electrochemical impedance spectroscopy and dark I-V characteristics.

  19. INFLUENCE OF MILDRONATE ON EFFICIENCY OF ANTIANGINAL THERAPY IN PATIENTS WITH STABLE BURDEN ANGINA

    Directory of Open Access Journals (Sweden)

    N. P. Kutishenko

    2005-01-01

    Full Text Available Aim. To study influence of mildronate (M on treatment efficiency of patients with ischemic heart disease (IHD, receiving standard antianginal therapy (AATMaterials and methods. Double-blind, randomized, placebo-controlled study was carried out in parallel groups. All patients continued the earlier prescribed AAT without changes. After control period (10-14 days was over, randomization of patients either to the treatment group (M 500mg twice per day, or to the control group (placebo (Pl twice per day was made for 6 weeks therapy. Criterion of treatment efficiency: increase in duration of trial with burden on treadmill (TB, decrease in angina attack frequency (AA and reduction in nitroglycerin taking (NTT. TB was carried out at the beginning (TB-1, at the end of the control period (TB-2, and at the end of the treatment (TB-3.Results. TB-1 and TB-2 had good reproducibility, their duration didn’t differ. At the end of the treatment additionally with M, growth in duration of TB-3 (p=0,002 was registered, while there was no growth of TB duration with the Pl treatment (p=0,07. During the treatment decrease in AA number both with M (p=0,002, and with Pl (p=0,02 was noted. With M treatment decrease in NTT treatment (p=0.02 was observed, while NTT with Pl didn’t change (p=0,7. Number of side effects, registered with M and Pl, didn’t differ.Conclusion. Mildronate provides additional benefits for patients with IHD with stable burden angina, when they do not reach desired effect with the prescribed AAT.

  20. Light use efficiency for vegetables production in protected and indoor environments

    Science.gov (United States)

    Cocetta, Giacomo; Casciani, Daria; Bulgari, Roberta; Musante, Fulvio; Kołton, Anna; Rossi, Maurizio; Ferrante, Antonio

    2017-01-01

    In recent years, there is a growing interest for vegetables production in indoor or disadvantaged climatic zones by using greenhouses. The main problem of crop growing indoor or in environment with limited light availability is the correct choice of light source and the quality of lighting spectrum. In greenhouse and indoor cultivations, plant density is higher than in the open field and plants have to compete for light and nutrients. Nowadays, advanced systems for indoor horticulture use light emitting diodes (LED) for improving crop growth, enhancing the plant productivity and favouring the best nutritional quality formation. In closed environments, as indoor growing modules, the lighting system represents the only source of light and its features are fundamental for obtaining the best lighting performances for plant and the most efficient solution. LED lighting engines are more efficient compared to the lighting sources used traditionally in horticulture and allow light spectrum and intensity modulations to enhance the light use efficiency for plants. The lighting distribution and the digital controls are fundamental for tailoring the spectral distribution on each plant in specific moments of its growth and play an important role for optimizing growth and produce high-quality vegetables. LED lights can increase plant growth and yield, but also nutraceutical quality, since some light intensities increase pigments biosynthesis and enhance the antioxidants content of leaves or fruits: in this regards the selection of LED primary light sources in relation to the peaks of the absorbance curve of the plants is important.

  1. Generation of Triple-Transgenic Forsythia Cell Cultures as a Platform for the Efficient, Stable, and Sustainable Production of Lignans.

    Science.gov (United States)

    Murata, Jun; Matsumoto, Erika; Morimoto, Kinuyo; Koyama, Tomotsugu; Satake, Honoo

    2015-01-01

    unprecedented platform for efficient, stable, and sustainable production of sesamin, and shows that a transgenic and specific light-regulated Forsythia cell-based metabolic engineering is a promising strategy for the acquisition of rare and beneficial lignans.

  2. Synthesis and characterization of highly efficient and stable Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt ternary hybrid structure

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Jiatao; Liu, Lin; Niu, Tongjun; Sun, Xiaosong, E-mail: sunxs@scu.edu.cn

    2017-05-01

    Highlights: • Visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalysts were prepared. • Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt showed highly efficient and stable photocatalystic activity. • The photocatalytic mechanism of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was given. - Abstract: Ag{sub 3}PO{sub 4} is an excellent photocatalyst with high efficiency and quantum yield, but suffers from the fast recombination of photogenerated electron-hole pairs and photo-corrosion. Hereby, the highly efficient and stable visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalyst were prepared via a three-step wet chemical approach. The as-prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was characterized by X-ray diffraction, US-vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra and transient photocurrent as well. Comparing with single Pr{sub 6}O{sub 11} or Ag{sub 3}PO{sub 4}, the prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite exhibited much higher photocatalytic activity and stability for the degradation of Rhodamine B under visible light irradiation (>420 nm). The enhanced photocatalytic performance of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite has been attributed to the efficient separation of photo-generated electron-hole pairs through a scheme system composed of Pr{sub 6}O{sub 11,} Ag{sub 3}PO{sub 4} and Pt.

  3. Improving Light Outcoupling Efficiency for OLEDs with Microlens Array Fabricated on Transparent Substrate

    Directory of Open Access Journals (Sweden)

    Jun Wang

    2014-01-01

    Full Text Available Low light outcoupling efficiency restricts the wide application of organic light-emitting diodes in solid state light market although the internal quantum efficiency of the device could reach near to 100%. In order to improve the output efficiency, different kinds of microlens array on the substrate emission surface were designed and simulated using light tracing method. Simulation results indicate that the microlens array on the substrate could efficiently improve the light output efficiency and an enhancement of 1.8 could be obtained with optimized microlens structure design. The microlens array with semicircle shape using polymer material was fabricated on glass substrate by a facile approach. Finally, the organic device with microlens array substrate was manufactured and the light output of the device with surface microlens structure could increase to 1.64 times comparing with the device without microlens.

  4. Reducing the efficiency–stability–cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells

    KAUST Repository

    Baran, Derya

    2016-11-21

    Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7.7 ± 0.1% without any solvent additives. The improvement is assigned to changes in microstructure that reduce charge recombination and increase the photovoltage, and to improved light harvesting across the visible region. The stability of P3HT-based devices in ambient conditions is also significantly improved relative to polymer:fullerene devices. Combined with a low-bandgap donor polymer (PBDTTT-EFT, also known as PCE10), the two mixed acceptors also lead to solar cells with 11.0 ± 0.4% efficiency and a high open-circuit voltage of 1.03 ± 0.01 V.

  5. Efficiency of Roundabouts as Compared to Traffic Light Controlled ...

    African Journals Online (AJOL)

    Comparison is made between roundabouts with traffic light and without traffic light and signalized intersections on the basis of their performance to simplify traffic congestion. Computer simulations are used to propose critical arrival rates to separate between the three mentioned modes to decrease congestion at intersection ...

  6. Analysis of CMOS hot carrier light sources using back-end-of-line light directing structures for improved light extraction efficiency

    Science.gov (United States)

    Bulling, Anthony F.; Venter, Petrus J.; du Plessis, Monuko

    2014-06-01

    Light emission from silicon is possible in CMOS through hot carrier electroluminescence. Low conversion and low extraction efficiency remains a challenge. By using existing back-end-of-line interconnect structures it is possible to improve the extraction efficiency. Such light directing structures were analysed with the use of a focused ion beam and scanning electron microscope. It was found that it is possible to improve light extraction efficiency and directionality of the light sources through a combination of back-end-of-line structures and field oxide manipulation resulting in an improved optical path for emitted photon radiation. However, further analysis indicates that total internal reflections, scattering and electromagnetic absorption from the via plugs and metal interconnects in the back-end-of-line stack are some of the key contributors to the inefficient light extraction efficiency.

  7. Synergetic Effect between Lighting Efficiency Enhancement and Building Energy Reduction Using Alternative Thermal Operating System of Indoor LED Lighting

    Directory of Open Access Journals (Sweden)

    Byung-Lip Ahn

    2015-08-01

    Full Text Available We investigated the synergetic effect between light-emitting diode (LED lighting efficiency and building energy savings in heating and cooling using an alternative thermal operating system (ATOS of indoor LED lighting integrated with the ventilation system of a building as an active cooling device. The heat generated from LED lighting and the indoor lighting illuminance were experimentally determined. The indoor heat gains in cooling and heating periods were determined using measurement data; the annual energy savings of an office building in heating and cooling were calculated through simulation. The LED lighting illuminance increased by approximately 40% and the lighting contribution for indoor heat gain was 7.8% in summer, while 69.8% in winter with the ATOS. Consequently, the annual total energy use of the office building could be reduced by 5.9%; the energy use in cooling and heating was reduced by 18.4% and 3.3%, respectively.

  8. Mesoscopic Oxide Double Layer as Electron Specific Contact for Highly Efficient and UV Stable Perovskite Photovoltaics.

    Science.gov (United States)

    Tavakoli, Mohammad Mahdi; Giordano, Fabrizio; Zakeeruddin, Shaik Mohammed; Grätzel, Michael

    2018-03-15

    The solar to electric power conversion efficiency (PCE) of perovskite solar cells (PSCs) has recently reached 22.7%, exceeding that of competing thin film photovoltaics and the market leader polycrystalline silicon. Further augmentation of the PCE toward the Shockley-Queisser limit of 33.5% warrants suppression of radiationless carrier recombination by judicious engineering of the interface between the light harvesting perovskite and the charge carrier extraction layers. Here, we introduce a mesoscopic oxide double layer as electron selective contact consisting of a scaffold of TiO 2 nanoparticles covered by a thin film of SnO 2 , either in amorphous (a-SnO 2 ), crystalline (c-SnO 2 ), or nanocrystalline (quantum dot) form (SnO 2 -NC). We find that the band gap of a-SnO 2 is larger than that of the crystalline (tetragonal) polymorph leading to a corresponding lift in its conduction band edge energy which aligns it perfectly with the conduction band edge of both the triple cation perovskite and the TiO 2 scaffold. This enables very fast electron extraction from the light perovskite, suppressing the notorious hysteresis in the current-voltage ( J-V) curves and retarding nonradiative charge carrier recombination. As a result, we gain a remarkable 170 mV in open circuit photovoltage ( V oc ) by replacing the crystalline SnO 2 by an amorphous phase. Because of the quantum size effect, the band gap of our SnO 2 -NC particles is larger than that of bulk SnO 2 causing their conduction band edge to shift also to a higher energy thereby increasing the V oc . However, for SnO 2 -NC there remains a barrier for electron injection into the TiO 2 scaffold decreasing the fill factor of the device and lowering the PCE. Introducing the a-SnO 2 coated mp-TiO 2 scaffold as electron extraction layer not only increases the V oc and PEC of the solar cells but also render them resistant to UV light which forebodes well for outdoor deployment of these new PSC architectures.

  9. Forensic Applications of Light-Element Stable Isotope Ratios of Ricinus communis Seeds and Ricin Preparations

    Energy Technology Data Exchange (ETDEWEB)

    Kreuzer, Helen W.; West, Jason B.; Ehleringer, James

    2013-01-01

    Seeds of the castor plant Ricinus communis, also known as castor beans, are of forensic interest because they are the source of the poison ricin. We have tested whether stable isotope ratios of castor seeds and ricin prepared by various methods can be used as a forensic signature. We collected over 300 castor seed samples from locations around the world and measured the C, N, O, and H stable isotope ratios of the whole seeds, oil, and three types of ricin preparations. Our results demonstrate that N isotope ratios can be used to correlate ricin prepared by any of these methods to source seeds. Further, stable isotope ratios distinguished >99% of crude and purified ricin protein samples in pair-wise comparison tests. Stable isotope ratios therefore constitute a valuable forensic signature for ricin preparations.

  10. Efficient light propagation for multiple anisotropic volume scattering

    Energy Technology Data Exchange (ETDEWEB)

    Max, N. [Lawrence Livermore National Lab., CA (United States)]|[California Univ., Davis, CA (United States)

    1993-12-01

    Realistic rendering of participating media like clouds requires multiple anisotropic light scattering. This paper presents a propagation approximation for light scattered into M direction bins, which reduces the ``ray effect`` problem in the traditional ``discrete ordinates`` method. For a volume of n{sup 3} elements, it takes O(M n{sup 3} log n + M{sup 2} n{sup 3}) time and O(M n{sup 3}) space.

  11. Stable, accurate and efficient computation of normal modes for horizontal stratified models

    Science.gov (United States)

    Wu, Bo; Chen, Xiaofei

    2016-08-01

    We propose an adaptive root-determining strategy that is very useful when dealing with trapped modes or Stoneley modes whose energies become very insignificant on the free surface in the presence of low-velocity layers or fluid layers in the model. Loss of modes in these cases or inaccuracy in the calculation of these modes may then be easily avoided. Built upon the generalized reflection/transmission coefficients, the concept of `family of secular functions' that we herein call `adaptive mode observers' is thus naturally introduced to implement this strategy, the underlying idea of which has been distinctly noted for the first time and may be generalized to other applications such as free oscillations or applied to other methods in use when these cases are encountered. Additionally, we have made further improvements upon the generalized reflection/transmission coefficient method; mode observers associated with only the free surface and low-velocity layers (and the fluid/solid interface if the model contains fluid layers) are adequate to guarantee no loss and high precision at the same time of any physically existent modes without excessive calculations. Finally, the conventional definition of the fundamental mode is reconsidered, which is entailed in the cases under study. Some computational aspects are remarked on. With the additional help afforded by our superior root-searching scheme and the possibility of speeding calculation using a less number of layers aided by the concept of `turning point', our algorithm is remarkably efficient as well as stable and accurate and can be used as a powerful tool for widely related applications.

  12. Investigation on efficiency of stable iodine distribution around Golfech nuclear power station

    International Nuclear Information System (INIS)

    Payoux, P.; Simon, J.; Campana Briault, H.; Fenolland, J.L.

    2003-01-01

    Background. In order to prevent thyroid cancer radio induced during civil nuclear accident french regulations plan stable iodine distribution for populations living near nuclear power stations. We evaluate availability of stable iodine and understanding of such measure with investigation around Golfech nuclear power station. Methods. In 2001, 1148 families living in a 10 km perimeter around power station were questioned through their schooled child. Our anonymous questionnaire (22 questions, 91 items) was linked with stable iodine availability, organ protection, most exposed persons, dosage and time of stable iodine ingestion. Results. 72,1 % families replied. Among them, 60,8% could easily and quickly find stable iodine in case of emergency, 87,8% know that such measure is to protect thyroid, 80,5% know that children and pregnant women (62,7%) are the most exposed people, 82,3% know that such ingestion is allowed by Prefect order. Conclusion. Answer rate and stable iodine prophylaxis knowledge are satisfactory. On the other hand, in case of necessity about 40% of the concerned families don't have a rapid access to stable iodine, which will forced authorities to distribute as a matter of urgency supplementary stable iodine. Statistical analysis of the answers demonstrate that the most iodine prophylaxis ignorant people are the most refractory to this approach. (author)

  13. Far-red light is needed for efficient photochemistry and photosynthesis.

    Science.gov (United States)

    Zhen, Shuyang; van Iersel, Marc W

    2017-02-01

    The efficiency of monochromatic light to drive photosynthesis drops rapidly at wavelengths longer than 685nm. The photosynthetic efficiency of these longer wavelengths can be improved by adding shorter wavelength light, a phenomenon known as the Emerson enhancement effect. The reverse effect, the enhancement of photosynthesis under shorter wavelength light by longer wavelengths, however, has not been well studied and is often thought to be insignificant. We quantified the effect of adding far-red light (peak at 735nm) to red/blue or warm-white light on the photosynthetic efficiency of lettuce (Lactuca sativa). Adding far-red light immediately increased quantum yield of photosystem II (Φ PSII ) of lettuce by an average of 6.5 and 3.6% under red/blue and warm-white light, respectively. Similar or greater increases in Φ PSII were observed after 20min of exposure to far-red light. This longer-term effect of far-red light on Φ PSII was accompanied by a reduction in non-photochemical quenching of fluorescence (NPQ), indicating that far-red light reduced the dissipation of absorbed light as heat. The increase in Φ PSII and complementary decrease in NPQ is presumably due to preferential excitation of photosystem I (PSI) by far-red light, which leads to faster re-oxidization of the plastoquinone pool. This facilitates reopening of PSII reaction centers, enabling them to use absorbed photons more efficiently. The increase in Φ PSII by far-red light was associated with an increase in net photosynthesis (P n ). The stimulatory effect of far-red light increased asymptotically with increasing amounts of far-red. Overall, our results show that far-red light can increase the photosynthetic efficiency of shorter wavelength light that over-excites PSII. Copyright © 2016 Elsevier GmbH. All rights reserved.

  14. Investigation of a scanning laser projector as an energy-efficient light source in plant production

    NARCIS (Netherlands)

    Murase, Haruhiko; Helm, van der Bob; Oke, Satoshi

    2015-01-01

    The energy costs for artificial lighting in plant factories are very high, but may be decreased by introducing more efficient light sources. Light absorption in plants takes place in the order of a femtosecond, while the chemical reactions for carbon fixation of 5 milliseconds are limiting the

  15. Photosynthetic efficiency and oxygen evolution of Chlamydomonas reinhardtii under continuous and flashing light.

    NARCIS (Netherlands)

    Vejrazka, C.; Janssen, M.; Benvenuti, G.; Streefland, M.; Wijffels, R.H.

    2013-01-01

    As a result of mixing and light attenuation in a photobioreactor (PBR), microalgae experience light/dark (L/D) cycles that can enhance PBR efficiency. One parameter which characterizes L/D cycles is the duty cycle; it determines the time fraction algae spend in the light. The objective of this study

  16. Connected Lighting Systems Efficiency Study$-$ PoE Cable Energy Losses, Part 1

    Energy Technology Data Exchange (ETDEWEB)

    Tuenge, Jason [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kelly, Karsten [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Poplawski, Michael [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-11-30

    First report in a study of the efficiency of connected lighting systems. The report summarizes the results of an exploratory study investigating power losses in Ethernet cables used between PoE switches and luminaires in PoE connected lighting systems. Testing was conducted at the Pacific Northwest National Laboratory (PNNL) Connected Lighting Test Bed in September 2017. The results were analyzed to explore the impact of cable selection on PoE lighting system energy efficiency, as well as the effectiveness of guidelines recently introduced by the American National Standards Institute (ANSI) C137 Lighting Systems Committee.

  17. Stable and Flexible CuInS2/ZnS:Al-TiO2 Film for Solar-Light-Driven Photodegradation of Soil Fumigant.

    Science.gov (United States)

    Yan, Lili; Li, Zhichun; Sun, Mingxing; Shen, Guoqing; Li, Liang

    2016-08-10

    Semiconductor quantum dots (QDs) are suitable light absorbers for photocatalysis because of their unique properties. However, QDs generally suffer from poor photochemical stability against air, limiting their applications in photocatalysis. In this study, a stable solar-light-driven QDs-containing photocatalytic film was developed to facilitate photocatalytic degradation of the soil fumigant 1,3-dichloropropene (1,3-D). Highly stable CuInS2/ZnS:Al core/shell QDs (CIS/ZnS:Al QDs) were synthesized by doping Al into the ZnS shell and controlling ZnS:Al shell thickness; the CIS/ZnS:Al QDs were subsequently combined with TiO2 to form a CIS/ZnS:Al-TiO2 photocatalyst. The optimized ZnS:Al shell thickness for 1,3-D photodegradation was approximately 1.3 nm, which guaranteed and balanced the good photocatalytic activity and stability of the CIS/ZnS:Al-TiO2 photocatalyst. The photodegradation efficiency of 1,3-D can be maintained up to more than 80% after five cycles during recycling experiment. When CIS/ZnS:Al-TiO2 was deposited as photocatalytic film on a flexible polyethylene terephthalate substrate, over 99% of cis-1,3-D and 98% of trans-1,3-D were depleted as they passed through the film during 15 h of irradiation under natural solar light. This study demonstrated that the stable CIS/ZnS:Al-TiO2 photocatalyst both in powder and film form is a promising agent for photodegradation and emission reduction of soil fumigants.

  18. Graphene/phase change material nanocomposites: light-driven, reversible electrical resistivity regulation via form-stable phase transitions.

    Science.gov (United States)

    Wang, Yunming; Mi, Hongyi; Zheng, Qifeng; Ma, Zhenqiang; Gong, Shaoqin

    2015-02-04

    Innovative photoresponsive materials are needed to address the complexity of optical control systems. Here, we report a new type of photoresponsive nanomaterial composed of graphene and a form-stable phase change material (PCM) that exhibited a 3 orders of magnitude change in electrical resistivity upon light illumination while retaining its overall original solid form at the macroscopic level. This dramatic change in electrical resistivity also occurred reversibly through the on/off control of light illumination. This was attributed to the reversible phase transition (i.e., melting/recrystallization) behavior of the microscopic crystalline domains present in the form-stable PCM. The reversible phase transition observed in the graphene/PCM nanocomposite was induced by a reversible temperature change through the on/off control of light illumination because graphene can effectively absorb light energy and convert it to thermal energy. In addition, this graphene/PCM nanocomposite also possessed excellent mechanical properties. Such photoresponsive materials have many potential applications, including flexible electronics.

  19. Geometric light trapping with a V-trap for efficient organic solar cells

    KAUST Repository

    Kim, Soo Jin

    2013-03-14

    The efficiency of today’s most efficient organic solar cells is primarily limited by the ability of the active layer to absorb all the sunlight. While internal quantum efficiencies exceeding 90% are common, the external quantum efficiency rarely exceeds 70%. Light trapping techniques that increase the ability of a given active layer to absorb light are common in inorganic solar cells but have only been applied to organic solar cells with limited success. Here, we analyze the light trapping mechanism for a cell with a V-shape substrate configuration and demonstrate significantly improved photon absorption in an 5.3%-efficient PCDTBT:PC70BM bulk heterojunction polymer solar cell. The measured short circuit current density improves by 29%, in agreement with model predictions, and the power conversion efficiency increases to 7.2%, a 35% improvement over the performance in the absence of a light trap.

  20. A high efficiency lateral light emitting device on SOI

    NARCIS (Netherlands)

    Hoang, T.; Le Minh, P.; Holleman, J.; Zieren, V.; Goossens, M.J.; Schmitz, Jurriaan

    2005-01-01

    The infrared light emission of lateral p/sup +/-p-n/sup +/ diodes realized on SIMOX-SOI (separation by implantation of oxygen - silicon on insulator) substrates has been studied. The confinement of the free carriers in one dimension due to the buried oxide was suggested to be a key point to increase

  1. Stable propagation of light-ion beam in inertial confinement fusion

    International Nuclear Information System (INIS)

    Okada, T.; Murakami, H.

    1996-01-01

    The stabilization mechanism of the filamentation instability for a light ion beam (LIB) penetrating plasma is investigated. For the stabilization of the filamentation instability, external magnetic field which is parallel to the direction of the light ion beam propagation is applied. Linear growth rates of filamentation instabilities in a light ion beam-plasma system with an external magnetic field were obtained by means of a dispersion relation. Numerical simulations were carried out using the particle-in-cell (PIC) method. The stabilizing mechanism of the filamentation instability is described. The theory and simulation comparisons illustrate the results. (author). 1 tab., 1 fig., 10 refs

  2. Organic light emitting diodes with environmentally and thermally stable doped graphene electrodes

    DEFF Research Database (Denmark)

    Kuruvila, Arun; Kidambi, Piran R.; Kling, Jens

    2014-01-01

    We present a comparative study of the environmental and thermal stability of graphene charge transfer doping using molybdenum– trioxide (MoO3), vanadium–pentoxide (V2O5) and tungsten–trioxide (WO3). Our results show that all these metal oxides allow a strong and stable p-type doping of graphene, ...

  3. National award for energy-efficient town lighting. Compilation of energy-efficient town lighting techniques; Bundeswettbewerb Energieeffiziente Stadtbeleuchtung. Sammlung energieeffizienter Techniken fuer die Stadtbeleuchtung

    Energy Technology Data Exchange (ETDEWEB)

    Piller, Sabine; Huebner, Vanessa; Barbre, Felix; Schaefer, Moritz [Berliner Energieagentur GmbH, Berlin (Germany)

    2009-02-11

    The national award for innovative urban lighting was initiated by the Federal Environmental Office. The resulting publication presents innovative techniques for urban lighting. While it is not a complete market survey, it provides an outline of modern, energy-efficient and environment-friendly technologies that are commercially available. Most systems are also available at comparatively low cost. For more information, interested users should refer to http://www.bmu.de/klimaschutzinitiative/aktuell/41708.php. (orig./AKB)

  4. Growth of GaN-based non- and semipolar heterostructures for high efficiency light emitters

    International Nuclear Information System (INIS)

    Wernicke, Tim

    2010-01-01

    Optoelectronic devices based on GaN and its alloys InGaN and AlGaN are capable of emitting light from the visible to the ultraviolet spectral region. Blue and green lasers have applications in laser projectors, DNA sequencing and spectroscopy. But it is extremely difficult to fabricate green laser diodes. Currently almost all of the light emitting diodes (LEDs) and lasers are grown on GaN crystals that are oriented in the polar (0001) c-plane direction, which provides the most stable growth surface. However the resulting polarization fields on (0001)GaN have detrimental effects on the optical properties of nitride light emitters, e.g. causing significant wavelength shifts and reduced efficiencies in InGaN LEDs. Growth on crystal surfaces with non- and semipolar orientations, e.g. (10 anti 10) m-plane or (11 anti 22), could enable devices with new and improved optical properties. For example, for nonpolar and semipolar LEDs the degree of polarization of the emitted light can be tailored. Furthermore easier to grow devices with green light emission, since the indium incorporation is enhanced for semipolar orientations. In contrast to c-plane GaN there is no polarization field across quantum wells on nonpolar GaN. By reducing the polarization fields an increase in the radiative recombination rate can be expected and would lead to higher LED efficiencies and lower laser thresholds. One of the biggest challenges for the growth of light emitters on non- and semipolar GaN is the choice of a suitable substrate: Heteroepitaxial growth on sapphire or LiAlO 2 allows the deposition of GaN on 2'' diameter wafers and larger. However, these layers show a very high defect density in particular basal plane stacking faults, in comparison to c-plane GaN on sapphire. In order to reduce the defect density we applied successfully epitaxial lateral overgrowth to heteroepitaxial nonpolar a-plane GaN and verified the improvement by spatially and spectrally cathodoluminescence imaging as

  5. Efficient lighting in a coal fired generating station

    Energy Technology Data Exchange (ETDEWEB)

    Panchal, B. [Ontario Power Generation, Toronto, ON (Canada)

    2001-02-01

    Upgrading the lighting in one of Ontario Power Generation's (formerly Ontario Hydro) coal-fired generating plants by replacing the open strip Very High Output (VHO) and F40 fixtures with metal halide fixtures (30-40 watt and 10-25 watt fixtures, respectively) is discussed. The wholesale replacement was preceded by a one year long trial in which 81 VHO and 79 F40 were replaced with 40 metal halide fixtures. The subsequent choice of metal halide for the entire plant was based on the results of this pilot project. Results showed a four-fold increase in light levels, a significant reduction in the number and types of lamps and ballasts used, a 60 per cent reduction in energy consumption and a 50 per cent reduction in maintenance costs. 2 photos.

  6. Phosphorescent organic light emitting diodes with high efficiency and brightness

    Energy Technology Data Exchange (ETDEWEB)

    Forrest, Stephen R; Zhang, Yifan

    2015-11-12

    An organic light emitting device including a) an anode; b) a cathode; and c) an emissive layer disposed between the anode and the cathode, the emissive layer comprising an organic host compound and a phosphorescent compound exhibiting a Stokes Shift overlap greater than 0.3 eV. The organic light emitting device may further include a hole transport layer disposed between the emissive layer and the anode; and an electron transport layer disposed between the emissive layer and the cathode. In some embodiments, the phosphorescent compound exhibits a phosphorescent lifetime of less than 10 .mu.s. In some embodiments, the concentration of the phosphorescent compound ranges from 0.5 wt. % to 10 wt. %.

  7. Very high efficiency phosphorescent organic light-emitting devices by using rough indium tin oxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yingjie; Aziz, Hany, E-mail: h2aziz@uwaterloo.ca [Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada)

    2014-07-07

    The efficiency of organic light-emitting devices (OLEDs) is shown to significantly depend on the roughness of the indium tin oxide (ITO) anode. By using rougher ITO, light trapped in the ITO/organic wave-guided mode can be efficiently extracted, and a light outcoupling enhancement as high as 40% is achieved. Moreover, contrary to expectations, the lifetime of OLEDs is not affected by ITO roughness. Finally, an OLED employing rough ITO anode that exhibits a current efficiency of 56 cd/A at the remarkably high brightness of 10{sup 5} cd/m{sup 2} is obtained. This represents the highest current efficiency at such high brightness to date for an OLED utilizing an ITO anode, without any external light outcoupling techniques. The results demonstrate the significant efficiency benefits of using ITO with higher roughness in OLEDs.

  8. Near-infrared branding efficiently correlates light and electron microscopy.

    Science.gov (United States)

    Bishop, Derron; Nikić, Ivana; Brinkoetter, Mary; Knecht, Sharmon; Potz, Stephanie; Kerschensteiner, Martin; Misgeld, Thomas

    2011-06-05

    The correlation of light and electron microscopy of complex tissues remains a major challenge. Here we report near-infrared branding (NIRB), which facilitates such correlation by using a pulsed, near-infrared laser to create defined fiducial marks in three dimensions in fixed tissue. As these marks are fluorescent and can be photo-oxidized to generate electron contrast, they can guide re-identification of previously imaged structures as small as dendritic spines by electron microscopy.

  9. The impact of clerestory lights on energy efficiency of buildings

    Directory of Open Access Journals (Sweden)

    Đenadić Dalibor M.

    2015-01-01

    Full Text Available The buildings are among major energy consumers, whose energy efficiency is rather low. Clerestory windows are responsible for a large portion of energy losses from the buildings. The energy efficiency of buildings can greatly be improved by upgrading clerestory and other windows. This paper focuses on the theoretical and experimental investigations on how this can be performed in an old school building in the town of Bor in eastern part of Serbia. For that purpose a modern measuring technique has been applied to identify the existing status, and to compare theoretical and actual conditions.

  10. Approach to Low-Cost High-Efficiency OLED Lighting. Building Technologies Solid State Lighting (SSL) Program Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Pei, Qibing [Univ. of California, Los Angeles, CA (United States). Dept. of Materials Science and Engineering

    2017-10-06

    This project developed an integrated substrate which organic light emitting diode (OLED) panel developers could employ the integrated substrate to fabricate OLED devices with performance and projected cost meeting the MYPP targets of the Solid State Lighting Program of the Department of Energy. The project optimized the composition and processing conditions of the integrated substrate for OLED light extraction efficiency and overall performance. The process was further developed for scale up to a low-cost process and fabrication of prototype samples. The encapsulation of flexible OLEDs based on this integrated substrate was also investigated using commercial flexible barrier films.

  11. Stable and Efficient CuO Based Photocathode through Oxygen-Rich Composition and Au-Pd Nanostructure Incorporation for Solar-Hydrogen Production.

    Science.gov (United States)

    Masudy-Panah, Saeid; Siavash Moakhar, Roozbeh; Chua, Chin Sheng; Kushwaha, Ajay; Dalapati, Goutam Kumar

    2017-08-23

    Enhancing stability against photocorrosion and improving photocurrent response are the main challenges toward the development of cupric oxide (CuO) based photocathodes for solar-driven hydrogen production. In this paper, stable and efficient CuO-photocathodes have been developed using in situ materials engineering and through gold-palladium (Au-Pd) nanoparticles deposition on the CuO surface. The CuO photocathode exhibits a photocurrent generation of ∼3 mA/cm 2 at 0 V v/s RHE. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis and X-ray spectroscopy (XPS) confirm the formation of oxygen-rich (O-rich) CuO film which demonstrates a highly stable photocathode with retained photocurrent of ∼90% for 20 min. The influence of chemical composition on the photocathode performance and stability has been discussed in detail. In addition, O-rich CuO photocathodes deposited with Au-Pd nanostructures have shown enhanced photoelectrochemical performance. Linear scan voltammetry characteristic shows ∼25% enhancement in photocurrent after Au-Pd deposition and reaches ∼4 mA/cm 2 at "0" V v/s RHE. Hydrogen evolution rate significantly depends on the elemental composition of CuO and metal nanostructure. The present work has demonstrated a stable photocathode with high photocurrent for visible-light-driven water splitting and hydrogen production.

  12. All-solution processed polymer light-emitting diodes with air stable metal-oxide electrodes

    NARCIS (Netherlands)

    Bruyn, P. de; Moet, D.J.D.; Blom, P.W.M.

    2012-01-01

    We present an all-solution processed polymer light-emitting diode (PLED) using spincoated zinc oxide (ZnO) and vanadium pentoxide (V2O5) as electron and hole injecting contact, respectively. We compare the performance of these devices to the standard PLED design using PEDOT:PSS as anode and Ba/Al as

  13. All-solution processed polymer light-emitting diodes with air stable metal-oxide electrodes

    NARCIS (Netherlands)

    de Bruyn, P.; Moet, D. J. D.; Blom, P. W. M.

    We present an all-solution processed polymer light-emitting diode (PLED) using spincoated zinc oxide (ZnO) and vanadium pentoxide (V2O5) as electron and hole injecting contact, respectively. We compare the performance of these devices to the standard PLED design using PEDOT:PSS as anode and Ba/Al as

  14. High efficiency blue phosphorescent organic light-emitting diodes without electron transport layer

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Soon Ok [Department of Polymer Science and Engineering, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of); Lee, Jun Yeob, E-mail: leej17@dankook.ac.kr [Department of Polymer Science and Engineering, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of)

    2011-08-15

    High efficiency blue phosphorescent organic light-emitting diodes were fabricated without an electron transport layer using a spirobifluorene based blue triplet host material. The simple blue PHOLEDs without the electron transport layer showed a high external quantum efficiency and current efficiency of 16.1% and 30.2 cd/A, respectively. The high device performances of the electron transport layer free blue PHOLEDs were comparable to those of blue PHOLEDs with the electron transport layer. - Highlights: > Simple device structure without electron transport layer. > High efficiency blue phosphorescent organic light-emitting diode. > Spirobifluorene based high triplet energy host material.

  15. Super RLuc8: A novel engineered Renilla luciferase with a red-shifted spectrum and stable light emission.

    Science.gov (United States)

    Rahnama, Somaieh; Saffar, Behnaz; Kahrani, Zahra Fanaei; Nazari, Mahboobeh; Emamzadeh, Rahman

    2017-01-01

    Renilla luciferase is a bioluminescent enzyme which is broadly used as a reporter protein in molecular biosensors. In this study, a novel luciferase with desired light emission wavelength and thermostability is reported. The results indicated that the new luciferase, namely super RLuc8, had a red-shifted spectrum and showed stable light emission. Super RLuc8 showed a 10-fold (p-value=0.0084) increase in the thermostability at 37°C after 20min incubation, in comparison to the native enzyme. The optimum temperature of the mutant increased from 30 to 37°C. Molecular dynamics simulation analysis indicated that the increased thermostability was most probably caused by a better structural compactness and more local rigidity in the regions out of the emitter site. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. The power conversion efficiency of visible light emitting devices in standard BiCMOS processes

    NARCIS (Netherlands)

    Kuindersma, P.; Hoang, T.; Schmitz, Jurriaan; Vijayaraghavan, M.N.; Dijkstra, Mindert; Dijkstra, M.; van Noort, W.A.; Vanhoucke, T.; Peters, W.C.M.; Kramer, M.C.J.C.M.

    2008-01-01

    We present experimental and theoretical proof for a single and unique relationship between the breakdown voltage and power efficiency of visible light emitting devices fabricated in standard BiCMOS processes.

  17. Guidebook for the Development of a Nationally Appropriate Mitigation Action on Efficient Lighting

    DEFF Research Database (Denmark)

    Conway, Kathryn M.; Lütken, Søren; Peña, Javier Otero

    This Guidebook illustrates how to create an efficient lighting NAMA based on a country-led national efficient lighting strategy. It aims to be a practical resource for governments (ministries of energy, environment, housing, climate change, finance, planning and others), private sector investors....... Articulating the NAMA facilitates communication with stakeholders, including citizens, the private sector, and national and international funders. Chapter 2 gives a generic background for the NAMA concept, origin and founding principles, as well as current interpretations among international stakeholders...... and the UNFCCC Secretariat. Chapter 3 provides specifics on how to develop a NAMA from a national efficient lighting strategy, using UNEP en.lighten initiative’s Achieving the Global Transition to Energy Efficient Lighting Toolkit and other tools, such as models and forecasts, to provide evidence...

  18. Fabrication of periodic microstructures for improving light-extraction efficiencies of light-emitting ZnO/Si devices

    Directory of Open Access Journals (Sweden)

    Oji Matsumoto

    Full Text Available This article presents the first demonstration of integrating a simple one-dimensional (1-D periodic microstructure and a light-emitting zinc oxide (ZnO thin film on a silicon (Si substrate using a simple process with two-beam interference lithography and sputtering. A 1-D microstructure composed of ZnO was obtained using our fabrication process without using a photomask and dry etching. The intensity of a photoluminescence (PL peak observed from a sample with the periodic microstructure was approximately 5.3 times stronger than that without it. The light-extraction efficiency from the ZnO thin film seems to be improved by the integration of the 1-D periodic microstructure. Keywords: ZnO/Si, Luminescence, Periodic microstructure, Light-extraction efficiency, Sputtering, Two-beam interference lithography

  19. Silicon nanocrystals as light sources: stable, efficient and fast photoluminescence with suitable passivation

    Czech Academy of Sciences Publication Activity Database

    Kůsová, Kateřina

    2012-01-01

    Roč. 9, 8/9 (2012), s. 717-731 ISSN 1475-7435 R&D Projects: GA AV ČR(CZ) IAA101120804; GA MŠk LC510; GA AV ČR KJB100100903 Institutional research plan: CEZ:AV0Z10100521 Keywords : silicon nanocrystals * surface passivation * photoluminescence * lasing Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.087, year: 2012

  20. Efficient light scattering through thin semi-transparent objects

    DEFF Research Database (Denmark)

    Frisvad, Jeppe Revall; Christensen, Niels Jørgen; Falster, Peter

    2005-01-01

    and almost opaque. To capture such visual effects in the standard rendering pipeline, Blinn [1982] proposed an efficient local illumination model based on radiative transfer theory. He assumed media of low density, hence, his equations can render media such as clouds, smoke, and dusty surfaces. Our...... observation is that Chandrasekhar [1960] has derived the same equations from a different set of assumptions. This alternative derivation makes the theory useful for realistic real-time rendering of dense, but thin, semi-transparent objects such as cloth. We demonstrate that application of the theory...

  1. Design, characterization and modelling of high efficient solar powered lighting systems

    DEFF Research Database (Denmark)

    Svane, Frederik; Nymann, Peter; Poulsen, Peter Behrensdorff

    2016-01-01

    This paper discusses some of the major challenges in the development of L2L (Light-2-Light) products. It’s the lack of efficient converter electronics, modelling tools for dimensioning and furthermore, characterization facilities to support the successful development of the products. We report th...

  2. Mechanisms that increase the growth efficiency of diatoms in low light.

    Science.gov (United States)

    Fisher, Nerissa L; Halsey, Kimberly H

    2016-08-01

    Photoacclimation was studied in Thalassiosira pseudonana to help understand mechanisms underlying the success of diatoms in low-light environments, such as coastal and deep mixing ecosystems. Light harvesting and other cell characteristics were combined with oxygen and carbon production measurements to assess the water-splitting reaction at PSII ([Formula: see text]) and intermediate steps leading to net carbon production (NPPC). These measurements revealed that T. pseudonana is remarkably efficient at converting harvested light energy into biomass, with at least 57 % of [Formula: see text] retained as NPPC across all light-limited growth rates examined. Evidence for upregulation of ATP generation pathways that circumvent carbon fixation indicated that high growth efficiency at low light levels was at least partly due to increases in the efficiency of ATP production. Growth rate-dependent demands for ATP and NADPH were reflected in carbon composition and in unexpected shifts in the light-limited slope (α) of photosynthesis-irradiance relationships generated from chlorophyll-specific (14)C-uptake. Overall, these results suggest that pathway gating of carbon and energy flow depends on light availability and is a key factor promoting the efficiency of diatom growth at low light intensities.

  3. Luminostat operation: A tool to maximize microalgae photosynthetic efficiency in photobioreactors during the daily light cycle?

    NARCIS (Netherlands)

    Cuaresma, M.; Janssen, M.G.J.; End, van den E.J.; Vílchez, C.; Wijffels, R.H.

    2011-01-01

    The luminostat regime has been proposed as a way to maximize light absorption and thus to increase the microalgae photosynthetic efficiency within photobioreactors. In this study, simulated outdoor light conditions were applied to a lab-scale photobioreactor in order to evaluate the luminostat

  4. India : Energy-Efficient Street Lighting--Implementation and Financing Solutions

    OpenAIRE

    World Bank

    2015-01-01

    There has been a clear need for energy-efficient (EE) technologies that can be applicable in the municipal street lighting sector. The objective of this manual is to support the preparation and implementation of street lighting projects in India, using performance contracting and other public private partnership-based delivery approaches. This manual draws upon global best practices, inclu...

  5. Environmental friendly high efficient light source plasma lamp - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Courret, G.; Calame, L. [Haute Ecole d' ingenierie et de gestion du canton de Vaud, Institut de micro et nano techniques, Yverdon-les-Bains (Switzerland); Meyer, A. [Solaronix SA, Aubonne (Switzerland)

    2007-07-01

    This illustrated final report for the Swiss Federal Office of Energy (SFOE) takes a look at work done on the development of a sulphur-based plasma lamp. In 2007, the capability of a new modulator has been explored. The most important results are discussed. With the production of a 1.2 cm{sup 3} bulb, the way towards the production of a 100 W lamp has been opened. The authors comment that modulation by impulses increases the luminous efficiency in comparison to modulation using a continuous sinusoidal wave. The report deals with the history of the project, the development of the new modulator, the use of rotational effects and the optimisation of the amount of active substances - tellurium and selenium - in the bulb. The electromagnetic coupling system used is described and discussed.

  6. GPC Light Shaper for energy efficient laser materials processing

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Villangca, Mark Jayson

    with steep, well defined edges that would further increase laser cutting precision or allow “single shot” laser engraving of arbitrary 2D profiles, as opposed to point scanning [3,4]. Instead of lossy approaches, GPC beam shaping is achieved with simplified, binary phase-only optics [5] that redistributes......The biggest use of lasers is in materials processing. In manufacturing, lasers are used for cutting, drilling, marking and other machining processes. Similarly, lasers are important in microfabrication processes such as photolithography, direct laser writing, or ablation. Lasers are advantageous...... because they do not wear out, have no physical contact with the processed material, avoid heating or warping effects, and are generally more precise. Since lasers are easier to adapt to different optimized shapes, they can be even more precise and energy efficient for materials processing. The cost...

  7. Berkeley Lab Sheds Light on Improving Solar Cell Efficiency

    International Nuclear Information System (INIS)

    Lawrence Berkeley National Laboratory

    2007-01-01

    Typical manufacturing methods produce solar cells with an efficiency of 12-15%; and 14% efficiency is the bare minimum for achieving a profit. In work performed at the Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley, CA, 5 10-486-577 1)--a US Department of Energy national laboratory that conducts unclassified scientific research and is managed by the University of California--scientist Scott McHugo has obtained keen insights into the impaired performance of solar cells manufactured from polycrystalline silicon. The solar cell market is potentially vast, according to Berkeley Lab. Lightweight solar panels are highly beneficial for providing electrical power to remote locations in developing nations, since there is no need to build transmission lines or truck-in generator fuel. Moreover, industrial nations confronted with diminishing resources have active programs aimed at producing improved, less expensive solar cells. 'In a solar cell, there is a junction between p-type silicon and an n-type layer, such as diffused-in phosphorous', explained McHugo, who is now with Berkeley Lab's Accelerator and Fusion Research Division. 'When sunlight is absorbed, it frees electrons, which start migrating in a random-walk fashion toward that junction. If the electrons make it to the junction; they contribute to the cell's output of electric current. Often, however, before they reach the junction, they recombine at specific sites in the crystal' (and, therefore, cannot contribute to current output). McHugo scrutinized a map of a silicon wafer in which sites of high recombination appeared as dark regions. Previously, researchers had shown that such phenomena occurred not primarily at grain boundaries in the polycrystalline material, as might be expected, but more often at dislocations in the crystal. However, the dislocations themselves were not the problem. Using a unique heat treatment technique, McHugo performed electrical measurements to investigate the material

  8. Efficient Light Extraction from Organic Light-Emitting Diodes Using Plasmonic Scattering Layers

    Energy Technology Data Exchange (ETDEWEB)

    Rothberg, Lewis

    2012-11-30

    Our project addressed the DOE MYPP 2020 goal to improve light extraction from organic light-emitting diodes (OLEDs) to 75% (Core task 6.3). As noted in the 2010 MYPP, “the greatest opportunity for improvement is in the extraction of light from [OLED] panels”. There are many approaches to avoiding waveguiding limitations intrinsic to the planar OLED structure including use of textured substrates, microcavity designs and incorporating scattering layers into the device structure. We have chosen to pursue scattering layers since it addresses the largest source of loss which is waveguiding in the OLED itself. Scattering layers also have the potential to be relatively robust to color, polarization and angular distributions. We note that this can be combined with textured or microlens decorated substrates to achieve additional enhancement.

  9. Cost-efficient light control for production of two campanula species

    DEFF Research Database (Denmark)

    Kjær, Katrine Heinsvig; Ottosen, Carl-Otto; Nørregaard Jørgensen, Bo

    2011-01-01

    A cost-efficient light control system based on weather forecasts, electricity prices and daily photosynthesis integral (DPI) was evaluated for application in the commercial production of the long-day (LD) plant Campanula portenschlagiana ‘Blue Get Mee’ and C. cochlearifolia ‘Blue Wonder......’. Experiments were conducted under both autumn and spring conditions and included four treatments. Three treatments were controlled by the software system DynaLight Desktop which automatically defined the most costefficient use of supplemental light, -based on a predefined set point of DPI, forecasted solar...... periods of solar irradiance combined with supplemental light in low light periods and a night period interrupted by irregular light breaks (NB-lighting). Both campanula species flowered in the DPI-based treatments during spring, but the flowering percentage was low and non-uniform during autumn...

  10. A synthetic, light-driven consortium of cyanobacteria and heterotrophic bacteria enables stable polyhydroxybutyrate production.

    Science.gov (United States)

    Weiss, Taylor L; Young, Eric J; Ducat, Daniel C

    2017-11-01

    We previously reported that Synechococcus elongatus PCC 7942, engineered with the sucrose transporter CscB, can export up to 85% of its photosynthetically-fixed carbon as sucrose and shows considerable promise as an alternative carbohydrate source. One approach to effectively utilize this cyanobacterium is to generate synthetic, light-driven consortia in which sucrose-metabolizing heterotrophs catalyze the conversion of the low-value carbohydrate into higher-value compounds in co-culture. Here, we report an improved synthetic photoautotroph/chemoheterotroph consortial design in which sucrose secreted by S. elongatus CscB directly supports the bacterium Halomonas boliviensis, a natural producer of the bioplastic precursor, PHB. We show that alginate encapsulation of S. elongatus CscB enhances sucrose-export rates ~2-fold within 66h, to ~290mg sucrose L -1 d -1 OD 750 -1 and enhances the co-culture stability. Consortial H. boliviensis accumulate up to 31% of their dry-weight as PHB, reaching productivities up to 28.3mg PHB L -1 d -1 . This light-driven, alginate-partitioned co-culture platform achieves PHB productivities that match or exceed those of traditionally engineered cyanobacterial monocultures. Importantly, S. elongatus CscB/H. boliviensis co-cultures were continuously productive for over 5 months and resisted invasive microbial species without the application of antibiotics or other chemical selection agents. Copyright © 2017 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.

  11. Epoxy-Based Organogels for Thermally Reversible Light Scattering Films and Form-Stable Phase Change Materials.

    Science.gov (United States)

    Puig, Julieta; Dell' Erba, Ignacio E; Schroeder, Walter F; Hoppe, Cristina E; Williams, Roberto J J

    2017-03-29

    Alkyl chains of β-hydroxyesters synthesized by the capping of terminal epoxy groups of diglycidylether of bisphenol A (DGEBA) with palmitic (C16), stearic (C18), or behenic (C22) fatty acids self-assemble forming a crystalline phase. Above a particular concentration solutions of these esters in a variety of solvents led to supramolecular (physical) gels below the crystallization temperature of alkyl chains. A form-stable phase change material (FS-PCM) was obtained by blending the ester derived from behenic acid with eicosane. A blend containing 20 wt % ester was stable as a gel up to 53 °C and exhibited a heat storage capacity of 161 J/g, absorbed during the melting of eicosane at 37 °C. Thermally reversible light scattering (TRLS) films were obtained by visible-light photopolymerization of poly(ethylene glycol) dimethacrylate-ester blends (50 wt %) in the gel state at room temperature. The reaction was very fast and not inhibited by oxygen. TRLS films consisted of a cross-linked methacrylic network interpenetrated by the supramolecular network formed by the esters. Above the melting temperature of crystallites formed by alkyl chains, the film was transparent due to the matching between refractive indices of the methacrylic network and the amorphous ester. Below the crystallization temperature, the film was opaque because of light dispersion produced by the organic crystallites uniformly dispersed in the material. Of high significance for application was the fact that the contrast ratio did not depend on heating and cooling rates.

  12. Light Stable Isotopes in Aquifers Affected by Mining Activities in a Brazilian Mining Province

    Science.gov (United States)

    Moreira, R. M.; de Carvalho, J. B.

    2013-05-01

    collected on a monthly base had to be stored in specially designed containers to avoid fractionation due to evaporation. Meteoric and groundwater samples were collected at a monthly rate along a whole year period at a total of forty seven stations including wells, springs and drainage sources, encompassing six aquifer units. Physical-chemical parameters, major ions, and both stable and radioactive nuclides were measured in the collected samples. Stable isotope measurements comprised the 2H/1H and 18O/16O ratios. Tritium level measurements were measured to evaluate the water residence time in the aquifers; since these levels are presently so low in the southern hemisphere electrolytic enrichment was required.

  13. High-efficiency white organic light-emitting diodes using thermally activated delayed fluorescence

    International Nuclear Information System (INIS)

    Nishide, Jun-ichi; Hiraga, Yasuhide; Nakanotani, Hajime; Adachi, Chihaya

    2014-01-01

    White organic light-emitting diodes (WOLEDs) have attracted much attention recently, aimed for next-generation lighting sources because of their high potential to realize high electroluminescence efficiency, flexibility, and low-cost manufacture. Here, we demonstrate high-efficiency WOLED using red, green, and blue thermally activated delayed fluorescence materials as emissive dopants to generate white electroluminescence. The WOLED has a maximum external quantum efficiency of over 17% with Commission Internationale de l'Eclairage coordinates of (0.30, 0.38).

  14. Efficient organic light-emitting devices with platinum-complex emissive layer

    KAUST Repository

    Yang, Xiaohui

    2011-01-18

    We report efficient organic light-emitting devices having a platinum-complex emissive layer with the peak external quantum efficiency of 17.5% and power efficiency of 45 lm W−1. Variation in the device performance with platinum-complex layer thickness can be attributed to the interplay between carrier recombination and intermolecular interactions in the layer. Efficient white devices using double platinum-complex layers show the external quantum efficiency of 10%, the Commission Internationale d’Énclairage coordinates of (0.42, 0.41), and color rendering index of 84 at 1000 cd m−2.

  15. Highly Efficient and Stable Flexible Perovskite Solar Cells with Metal Oxides Nanoparticle Charge Extraction Layers.

    Science.gov (United States)

    Najafi, Mehrdad; Di Giacomo, Francesco; Zhang, Dong; Shanmugam, Santhosh; Senes, Alessia; Verhees, Wiljan; Hadipour, Afshin; Galagan, Yulia; Aernouts, Tom; Veenstra, Sjoerd; Andriessen, Ronn

    2018-02-09

    In this study, the fabrication of highly efficient and durable flexible inverted perovskite solar cells (PSCs) is reported. Presynthesized, solution-derived NiO x and ZnO nanoparticles films are employed at room temperature as a hole transport layer (HTL) and electron transport layer (ETL), respectively. The triple cation perovskite films are produced in a single step and for the sake of comparison, ultrasmooth and pinhole-free absorbing layers are also fabricated using MAPbI 3 perovskite. The triple cation perovskite cells exhibit champion power conversion efficiencies (PCEs) of 18.6% with high stabilized power conversion efficiency of 17.7% on rigid glass/indium tin oxide (ITO) substrates (comparing with 16.6% PCE with 16.1% stabilized output efficiency for the flexible polyethylene naphthalate (PEN)/thin film barrier/ITO substrates). More interestingly, the durability of flexible PSC under simulation of operative condition is proved. Over 85% of the maximum stabilized output efficiency is retained after 1000 h aging employing a thin MAPbI 3 perovskite (over 90% after 500 h with a thick triple cation perovskite). This result is comparable to a similar state of the art rigid PSC and represents a breakthrough in the stability of flexible PSC using ETLs and HTLs compatible with roll to roll production speed, thanks to their room temperature processing. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Ultra-bright and highly efficient inorganic based perovskite light-emitting diodes

    Science.gov (United States)

    Zhang, Liuqi; Yang, Xiaolei; Jiang, Qi; Wang, Pengyang; Yin, Zhigang; Zhang, Xingwang; Tan, Hairen; Yang, Yang (Michael); Wei, Mingyang; Sutherland, Brandon R.; Sargent, Edward H.; You, Jingbi

    2017-06-01

    Inorganic perovskites such as CsPbX3 (X=Cl, Br, I) have attracted attention due to their excellent thermal stability and high photoluminescence quantum efficiency. However, the electroluminescence quantum efficiency of their light-emitting diodes was CsPbBr3 lattice and by depositing a hydrophilic and insulating polyvinyl pyrrolidine polymer atop the ZnO electron-injection layer to overcome these issues. As a result, we obtained light-emitting diodes exhibiting a high brightness of 91,000 cd m-2 and a high external quantum efficiency of 10.4% using a mixed-cation perovskite Cs0.87MA0.13PbBr3 as the emitting layer. To the best of our knowledge, this is the brightest and most-efficient green perovskite light-emitting diodes reported to date.

  17. Interfacial engineering of metal-insulator-semiconductor junctions for efficient and stable photoelectrochemical water oxidation

    Science.gov (United States)

    Digdaya, Ibadillah A.; Adhyaksa, Gede W. P.; Trześniewski, Bartek J.; Garnett, Erik C.; Smith, Wilson A.

    2017-06-01

    Solar-assisted water splitting can potentially provide an efficient route for large-scale renewable energy conversion and storage. It is essential for such a system to provide a sufficiently high photocurrent and photovoltage to drive the water oxidation reaction. Here we demonstrate a photoanode that is capable of achieving a high photovoltage by engineering the interfacial energetics of metal-insulator-semiconductor junctions. We evaluate the importance of using two metals to decouple the functionalities for a Schottky contact and a highly efficient catalyst. We also illustrate the improvement of the photovoltage upon incidental oxidation of the metallic surface layer in KOH solution. Additionally, we analyse the role of the thin insulating layer to the pinning and depinning of Fermi level that is responsible to the resulting photovoltage. Finally, we report the advantage of using dual metal overlayers as a simple protection route for highly efficient metal-insulator-semiconductor photoanodes by showing over 200 h of operational stability.

  18. Stable and Highly Efficient Electrochemical Production of Formic Acid from Carbon Dioxide Using Diamond Electrodes.

    Science.gov (United States)

    Natsui, Keisuke; Iwakawa, Hitomi; Ikemiya, Norihito; Nakata, Kazuya; Einaga, Yasuaki

    2018-03-01

    High faradaic efficiencies can be achieved in the production of formic acid (HCOOH) by metal electrodes, such as Sn or Pb, in the electrochemical reduction of carbon dioxide (CO 2 ). However, the stability and environmental load in using them are problematic. The electrochemical reduction of CO 2 to HCOOH was investigated in a flow cell using boron-doped diamond (BDD) electrodes. BDD electrodes have superior electrochemical properties to metal electrodes, and, moreover, are highly durable. The faradaic efficiency for the production of HCOOH was as high as 94.7 %. Furthermore, the selectivity for the production of HCOOH was more than 99 %. The rate of the production was increased to 473 μmol m -2  s -1 at a current density of 15 mA cm -2 with a faradaic efficiency of 61 %. The faradaic efficiency and the production rate are almost the same as or larger than those achieved using Sn and Pb electrodes. Furthermore, the stability of the BDD electrodes was confirmed by 24 h operation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Light extraction efficiency improvement by multiple laser stealth dicing in InGaN-based blue light-emitting diodes.

    Science.gov (United States)

    Zhang, Yiyun; Xie, Haizhong; Zheng, Haiyang; Wei, Tongbo; Yang, Hua; Li, Jing; Yi, Xiaoyan; Song, Xiangyang; Wang, Guohong; Li, Jinmin

    2012-03-12

    We report a multiple laser stealth dicing (multi-LSD) method to improve the light extraction efficiency (LEE) of InGaN-based light-emitting diodes (LEDs) using a picosecond (Ps) laser. Compared with conventional LEDs scribed by a nanosecond (Ns) laser and single stealth-diced LEDs, the light output power (LOP) of the LEDs using multi-LSD method can be improved by 26.5% and 11.2%, respectively. The enhanced LOP is due to the increased side emission from the large-area roughened sidewalls of the sapphire substrates fabricated in the multi-LSD process. Numerical simulation results show that the multi-LSD process has little thermal damages to the multiple quantum wells (MQWs) of the LEDs.

  20. Chip designs for high efficiency III-nitride based ultraviolet light emitting diodes with enhanced light extraction

    OpenAIRE

    Lobo Ploch, Neysha

    2015-01-01

    Ziel dieser Arbeit war es hocheffiziente III-nitridbasierte UV-LEDs für Anwendungen wie z.B. Wasserdesinfektion, medizinische Phototherapie oder Gasdetektion zu entwerfen und herzustellen. Der Schwerpunkt lag dabei auf dem Design der UV-LEDs, wodurch nicht nur das elektrische Verhalten, sondern auch die Lichtauskopplung (engl. light extraction efficiency, LEE) der UV-LED verbessert wird. Der erste Teil dieser Arbeit beschätigt sich mit dem Chipdesign von UV-LEDs und den es beeinflussenden ...

  1. One-step fabrication of copper sulfide nanoparticles decorated on graphene sheets as highly stable and efficient counter electrode for CdS-sensitized solar cells

    Science.gov (United States)

    Hessein, Amr; Wang, Feiju; Masai, Hirokazu; Matsuda, Kazunari; Abd El-Moneim, Ahmed

    2016-11-01

    Quantum-dot-sensitized solar cells (QDSSCs) are thin-film photovoltaics and highly promising as next-generation solar cells owing to their high theoretical efficiency, easy fabrication process, and low production cost. However, the practical photoconversion efficiencies (PCEs) of QDSSCs are still far below the theoretically estimated value owing to the lack of an applicable design of the materials and electrodes. In this work, we developed a highly stable and efficient counter electrode (CE) from copper sulfide nanocrystals and reduced graphene oxide (Cu x S@RGO) for QDSSC applications. The Cu x S@RGO electrocatalyst was successfully prepared by a facile one-pot hydrothermal method, then directly applied to a fluorine-doped tin oxide (FTO)-coated glass substrate by the simple drop-casting technique. Owing to the synergistic effect between Cu x S nanocrystals and conductive RGO sheets, the Cu x S@RGO CE showed high electrocatalytic activity for polysulfide electrolyte reduction. A CdS QDSSC based on the Cu x S@RGO CE yielded a high and reproducible PCE of 2.36%, exceeding those of 1.57 and 1.33% obtained with the commonly used Cu2S/brass and Pt CEs, respectively. Moreover, the QDSSC with the Cu x S@RGO CE showed excellent photostability in a light-soaking test without any obvious decay in the photocurrent, whereas the cell based on the Cu2S/brass CE was severely degraded.

  2. Hydrolytically stable fluorinated metal-organic frameworks for energy-efficient dehydration

    KAUST Repository

    Cadiau, Amandine

    2017-05-18

    Natural gas must be dehydrated before it can be transported and used, but conventional drying agents such as activated alumina or inorganic molecular sieves require an energy-intensive desiccant-regeneration step. We report a hydrolytically stable fluorinated metal-organic framework, AlFFIVE-1-Ni (KAUST-8), with a periodic array of open metal coordination sites and fluorine moieties within the contracted square-shaped one-dimensional channel. This material selectively removed water vapor from gas streams containing CO2, N2, CH4, and higher hydrocarbons typical of natural gas, as well as selectively removed both H2O and CO2 in N2-containing streams. The complete desorption of the adsorbed water molecules contained by the AlFFIVE-1-Ni sorbent requires relatively moderate temperature (~105°C) and about half the energy input for commonly used desiccants.

  3. HDTV projection display based on high-efficiency optically addressed PDLC light valves

    Science.gov (United States)

    Kikuchi, Hiroshi; Fujii, Takanori; Kawakita, Masahiro; Fujikake, Hideo; Aida, Tahito; Takizawa, Kuniharu

    1999-05-01

    The polymer-dispersed liquid crystal (PDLC) films of the optically addressed light valves in the high-definition television (HDTV) projection display described here can modulate unpolarized light with high spatial resolution as well as with a high optical efficiency based on the light scattering effect. A PDLC film suitable for use in HDTV projection display was developed by evaluating the microscopic spatial light modulation and polymer-network morphological properties of test films prepared using various curing conditions for photopolymerization-induced phase separation. Films produced under optimum curing conditions have a fine polymer-network structure appropriate for films used in the light valves of a HDTV projection display. Our prototype full-color HDTV projection display using three PDLC light valves provides a resolution of 850 TV lines, a brightness greater than 1800 ANSI lumens, and a maximum contrast ratio of 100:1.

  4. A SOFTWARE PRODUCT LINE FOR ENERGY-EFFICIENT CONTROL OF SUPPLEMENTARY LIGHTING IN GREENHOUSES

    DEFF Research Database (Denmark)

    Mærsk-Møller, Hans Martin; Jørgensen, Bo Nørregaard

    2011-01-01

    Web, for computing potential savings of our approach, and a desktop version, DynaLight Desktop, that computes an optimal supplementary light plan and controls the supplementary lighting accordantly. DynaLight Desktop is currently being field-tested at five industrial-size greenhouses. The development......In 2009, the industrial-size greenhouses in Denmark consumed 0.8 percent of the national electricity consumption. The increasing energy costs for heating and supplementary lighting have bankrupt many growers in 2010 causing an urgent need for remaining growers to reduce the consumption while...... preserving production quality. This paper presents a novel approach addressing this issue. We use weather forecasts and electricity prices to compute cost- and energy-efficient supplementary light plans that achieve the required plant growth defined by the grower. Experiments performed during the winter...

  5. Efficient, air-stable colloidal quantum dot solar cells encapsulated using atomic layer deposition of a nanolaminate barrier

    KAUST Repository

    Ip, Alexander H.

    2013-12-23

    Atomic layer deposition was used to encapsulate colloidal quantum dot solar cells. A nanolaminate layer consisting of alternating alumina and zirconia films provided a robust gas permeation barrier which prevented device performance degradation over a period of multiple weeks. Unencapsulated cells stored in ambient and nitrogen environments demonstrated significant performance losses over the same period. The encapsulated cell also exhibited stable performance under constant simulated solar illumination without filtration of harsh ultraviolet photons. This monolithically integrated thin film encapsulation method is promising for roll-to-roll processed high efficiency nanocrystal solar cells. © 2013 AIP Publishing LLC.

  6. LED arrays as cost effective and efficient light sources for widefield microscopy.

    Directory of Open Access Journals (Sweden)

    Dinu F Albeanu

    Full Text Available New developments in fluorophores as well as in detection methods have fueled the rapid growth of optical imaging in the life sciences. Commercial widefield microscopes generally use arc lamps, excitation/emission filters and shutters for fluorescence imaging. These components can be expensive, difficult to maintain and preclude stable illumination. Here, we describe methods to construct inexpensive and easy-to-use light sources for optical microscopy using light-emitting diodes (LEDs. We also provide examples of its applicability to biological fluorescence imaging.

  7. Determination of gas recovery efficiency at two Danish landfills by performing downwind methane measurements and stable carbon isotopic analysis.

    Science.gov (United States)

    Aghdam, Ehsan F; Fredenslund, Anders M; Chanton, Jeffrey; Kjeldsen, Peter; Scheutz, Charlotte

    2018-03-01

    In this study, the total methane (CH 4 ) generation rate and gas recovery efficiency at two Danish landfills were determined by field measurements. The landfills are located close to each other and are connected to the same gas collection system. The tracer gas dispersion method was used for quantification of CH 4 emissions from the landfills, while the CH 4 oxidation efficiency in the landfill cover layers was determined by stable carbon isotopic technique. The total CH 4 generation rate was estimated by a first-order decay model (Afvalzorg) and was compared with the total CH 4 generation rate determined by field measurements. CH 4 emissions from the two landfills combined ranged from 29.1 to 49.6 kg CH 4 /h. The CH 4 oxidation efficiency was 6-37%, with an average of 18% corresponding to an average CH 4 oxidation rate of 8.1 kg CH 4 /h. The calculated gas recovery efficiency was 59-76%, indicating a high potential for optimization of the gas collection system. Higher gas recovery efficiencies (73-76%) were observed after the commencement of gas extraction from a new section of one of the landfills. A good agreement was observed between the average total CH 4 generation rates determined by field measurements (147 kg CH 4 /h) and those estimated by the Afvalzorg model (154 kg CH 4 /h). Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Materials and Device Engineering for Efficient and Stable Polymer Solar Cells

    OpenAIRE

    Hansson, Rickard

    2017-01-01

    Polymer solar cells form a promising technology for converting sunlight into electricity, and have reached record efficiencies over 10% and lifetimes of several years. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor materials in the active layer. To achieve longer lifetimes, degradation processes in the materials have to be understood. In this thesis, a set of complementary spectroscopy and microscopy techniques, among which soft X-ra...

  9. Intrinsic Flame-Retardant and Thermally Stable Epoxy Endowed by a Highly Efficient, Multifunctional Curing Agent

    Directory of Open Access Journals (Sweden)

    Chunlei Dong

    2016-12-01

    Full Text Available It is difficult to realize flame retardancy of epoxy without suffering much detriment in thermal stability. To solve the problem, a super-efficient phosphorus-nitrogen-containing reactive-type flame retardant, 10-(hydroxy(4-hydroxyphenylmethyl-5,10-dihydrophenophosphazinine-10-oxide (HB-DPPA is synthesized and characterized. When it is used as a co-curing agent of 4,4′-methylenedianiline (DDM for curing diglycidyl ether of bisphenol A (DGEBA, the cured epoxy achieves UL-94 V-0 rating with the limiting oxygen index of 29.3%. In this case, the phosphorus content in the system is exceptionally low (0.18 wt %. To the best of our knowledge, it currently has the highest efficiency among similar epoxy systems. Such excellent flame retardancy originates from the exclusive chemical structure of the phenophosphazine moiety, in which the phosphorus element is stabilized by the two adjacent aromatic rings. The action in the condensed phase is enhanced and followed by pressurization of the pyrolytic gases that induces the blowing-out effect during combustion. The cone calorimeter result reveals the formation of a unique intumescent char structure with five discernible layers. Owing to the super-efficient flame retardancy and the rigid molecular structure of HB-DPPA, the flame-retardant epoxy acquires high thermal stability and its initial decomposition temperature only decreases by 4.6 °C as compared with the unmodified one.

  10. Evaluation of particulate filtration efficiency of retrofit particulate filters for light duty vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Van Asch, R.; Verbeek, R.

    2009-10-15

    In the light of the currently running subsidy programme for particulate filters in the Netherlands, the Dutch ministry of spatial planning and environment (VROM) asked TNO to execute a desk study to evaluate the particulates filtration efficiency of retrofit particulate filters for light duty vehicles (passenger cars and vans). The typical retrofit particulate filters for light duty vehicles are also called 'open' or 'half-open' filters, because a part of the exhaust gas can pass through the particulate filter unfiltered. From design point they are very different from the majority of the factory installed particulate filters, which are also called wall-flow or 'closed' particulate filters. Due to these differences there is a large difference in filtration efficiency. Whereas the 'dosed' particulate filters show a filtration efficiency of larger than 90%, the filtration efficiency of 'open' particulate filters is generally lower (type approval minimum 30%), and strongly dependent on the conditions of use. The objective of the current project was to assess the average filtration efficiency of retrofit (open) particulate fillters on light duty vehicles in real world day to day driving, based on available literature data. Also, the reasons of a possible deviation with the type approval test results (minimum filtration efficiency of 30%) was investigated.

  11. Adjusted light and dark cycles can optimize photosynthetic efficiency in algae growing in photobioreactors.

    Directory of Open Access Journals (Sweden)

    Eleonora Sforza

    Full Text Available Biofuels from algae are highly interesting as renewable energy sources to replace, at least partially, fossil fuels, but great research efforts are still needed to optimize growth parameters to develop competitive large-scale cultivation systems. One factor with a seminal influence on productivity is light availability. Light energy fully supports algal growth, but it leads to oxidative stress if illumination is in excess. In this work, the influence of light intensity on the growth and lipid productivity of Nannochloropsis salina was investigated in a flat-bed photobioreactor designed to minimize cells self-shading. The influence of various light intensities was studied with both continuous illumination and alternation of light and dark cycles at various frequencies, which mimic illumination variations in a photobioreactor due to mixing. Results show that Nannochloropsis can efficiently exploit even very intense light, provided that dark cycles occur to allow for re-oxidation of the electron transporters of the photosynthetic apparatus. If alternation of light and dark is not optimal, algae undergo radiation damage and photosynthetic productivity is greatly reduced. Our results demonstrate that, in a photobioreactor for the cultivation of algae, optimizing mixing is essential in order to ensure that the algae exploit light energy efficiently.

  12. Adjusted light and dark cycles can optimize photosynthetic efficiency in algae growing in photobioreactors.

    Science.gov (United States)

    Sforza, Eleonora; Simionato, Diana; Giacometti, Giorgio Mario; Bertucco, Alberto; Morosinotto, Tomas

    2012-01-01

    Biofuels from algae are highly interesting as renewable energy sources to replace, at least partially, fossil fuels, but great research efforts are still needed to optimize growth parameters to develop competitive large-scale cultivation systems. One factor with a seminal influence on productivity is light availability. Light energy fully supports algal growth, but it leads to oxidative stress if illumination is in excess. In this work, the influence of light intensity on the growth and lipid productivity of Nannochloropsis salina was investigated in a flat-bed photobioreactor designed to minimize cells self-shading. The influence of various light intensities was studied with both continuous illumination and alternation of light and dark cycles at various frequencies, which mimic illumination variations in a photobioreactor due to mixing. Results show that Nannochloropsis can efficiently exploit even very intense light, provided that dark cycles occur to allow for re-oxidation of the electron transporters of the photosynthetic apparatus. If alternation of light and dark is not optimal, algae undergo radiation damage and photosynthetic productivity is greatly reduced. Our results demonstrate that, in a photobioreactor for the cultivation of algae, optimizing mixing is essential in order to ensure that the algae exploit light energy efficiently.

  13. White light emission from radical carbonyl-terminations in Al2O3-SiO2 porous glasses with high luminescence quantum efficiencies

    International Nuclear Information System (INIS)

    Hayakawa, Tomokatsu; Hiramitsu, Ai; Nogami, Masayuki

    2003-01-01

    Development of white phosphors with highly emissive, stable, and less toxic characteristics has been important for display and lighting technology. In this letter, it is shown that sol-gel-derived glasses of aluminosilicate composition, followed by a heat treatment in air at low temperatures around 500 deg. C, exhibit two intense, visible photoluminescence bands: One is due to point defects in these glasses and the other comes from radical carbonyl-terminations on the surface of pores. The photoluminescence provides a white light with high luminescence quantum efficiency (∼66.5%) under long-wavelength ultraviolet excitation

  14. MoO3–Au composite interfacial layer for high efficiency and air-stable organic solar cells

    DEFF Research Database (Denmark)

    Pan, Hongbin; Zuo, Lijian; Fu, Weifei

    2013-01-01

    Efficient and stable polymer bulk-heterojunction solar cells based on regioregular poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) blend active layer have been fabricated with a MoO3–Au co-evaporation composite film as the anode interfacial layer (AIL). The optical...... resistance and thus improving the fill factor and efficiency of the devices. Additionally, the air stability of devices with different AILs (MoO3–Au composite, MoO3 and PEDOT:PSS) were studied and it was found that the MoO3–Au composite layer remarkably improved the stability of the solar cells with shelf...

  15. In-situ studies of microbial CH4 oxidation efficiency in Arctic wetland soils. Applications of stable carbon isotopes

    International Nuclear Information System (INIS)

    Preuss, Inken-Marie

    2013-01-01

    Arctic wetland soils are significant sources of the climate-relevant trace gas methane (CH 4 ). The observed accelerated warming of the Arctic is expected to cause deeper permafrost thawing followed by increased carbon mineralization and CH 4 formation in water-saturated permafrost-affected tundra soils thus creating a positive feedback to climate change. Aerobic CH 4 oxidation is regarded as the key process reducing CH 4 emissions from wetlands, but quantification of turnover rates has remained difficult so far. This study improved the in-situ quantification of microbial CH 4 oxidation efficiency in arctic wetland soils in Russia's Lena River Delta based on stable isotope signatures of CH 4 . In addition to the common practice of determining the stable isotope fractionation during oxidation, additionally the fractionation effect of diffusion, an important gas transport mechanism in tundra soils, was investigated for both saturated and unsaturated conditions. The isotopic fractionation factors α ox and α diff were used to calculate the CH 4 oxidation efficiency from the CH 4 stable isotope signatures of wet polygonal tundra soils of different hydrology. Further, the method was used to study the short-term effects of temperature increase with a climate manipulation experiment. For the first time, the stable isotope fractionation of CH 4 diffusion through water-saturated soils was determined with α diff = 1.001 ± 0.0002 (n = 3). CH 4 stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was α diff = 1.013 ± 0.003 (n = 18). For the studied sites the fractionation factor for diffusion under saturated conditions α diff = 1.001 seems to be of utmost importance for the quantification of the CH 4 oxidation efficiency, since most of the CH 4 is oxidized in the saturated part at the aerobic-anaerobic interface. Furthermore, it was found that α ox differs widely between sites and horizons (mean α ox = 1

  16. Catalysts and conditions for the highly efficient, selective and stable heterogeneous oligomerisation of ethylene

    Energy Technology Data Exchange (ETDEWEB)

    Heveling, J.; Nicolaides, C.P.; Scurrell [Catalysis Programme, Division of Energy Technology, CSIR, PO Box 395, Pretoria 0001 (South Africa)

    1998-10-11

    The oligomerisation of ethylene into products in the C{sub 4}-C{sub 20} range over heterogeneous nickel catalysts in a fixed-bed reactor at low temperature and high pressure (LT-HP) is reported. The catalysts were obtained by Ni(II) exchange or impregnation of two differently prepared amorphous and mesoporous silica-alumina supports. A plot of catalytic activity versus temperature at 35bar and MHSV=2 produces a volcano-type curve with a maximum around 120C. Experiments performed under the LT-HP reaction conditions, viz. 120C, 35bar and MHSV=2, give an ethylene conversion level of 99% and a 97% selectivity to products with an even number of carbon atoms. The product spectrum (C{sub n} distribution) was dependent on the type of catalyst used, with the percentage of the C{sub 10+} coligomers lying in the range 23-41% by mass. Of practical significance, these types of catalyst were found to be extremely stable in use showing no detectable drop in conversion after 108 days on stream under the LT-HP employed

  17. Efficient and stable polymer solar cells prepared using plasmonic graphene oxides as anode buffers

    Science.gov (United States)

    Chen, Chung-Lei; Chuang, Ming-Kai; Chen, Chyong-Hua; Chu, Chih-Wei; Keshtov, Muchamed L.; Chen, Fang-Chung

    2015-08-01

    Gold nanoparticle-decorated graphene oxides (AuNP-GOs) have been incorporated into inverted organic photovoltaic devices (OPVs) as anode interlayers. The OPVs fabricated with AuNP-GOs exhibited significant improvement in both the short-circuit current and fill factor compared to a reference device fabricated with neat GOs. We attribute the improvement in the efficiency of the device to the plasmonic effects of the AuNP-GO nanocomposites, which induced local enhancement of the electromagnetic field. More importantly, the inverted OPVs also exhibited better reliability after the use of AuNP-GO nanocomposites.

  18. Integration of 3D printed lens with InGaN light-emitting diodes with enhanced light extraction efficiency

    Science.gov (United States)

    Ooi, Yu Kee; Ugras, Christopher; Liu, Cheng; Hartensveld, Matthew; Gandhi, Shaunak; Cormier, Denis; Zhang, Jing

    2017-02-01

    III-nitride based light-emitting diodes (LEDs) have great potential in various applications due to their higher efficiency and longer lifetime. However, conventional planar structure InGaN LED suffers from total internal reflection due to large refractive index contrast between GaN (nGaN = 2.5) and air (nair = 1), which results in low light extraction efficiency (ηextraction). Accordingly, various approaches have been proposed previously to enhance the ηextraction. Nevertheless, most of the proposed methods involve elaborated fabrication processes. Therefore, in this work, we proposed the integration of three-dimensional (3D) printing with LED fabrication as a straightforward and highlyreproducible method to improve the ηextraction. Specifically, 500-μm diameter dome-shaped lens of optically transparent acrylate-based photopolymer is 3D-printed on planar structure 500 × 500 μm2 blue-emitting LEDs. Light output power measurement shows that up to 9% enhancement at injection current 4 mA can be obtained from the LEDs with 3D printed lens on top as compared to LEDs without the lens. Angle-dependent electroluminescence measurement also exhibits significant light output enhancement between angles 0 and 30° due to the larger photon escape cone introduced by the higher refractive index of the 3D printed lens (nlens = 1.5) than the air medium as well as the enhanced light scattering effect attributed to the curvature surface of the 3D printed lens. Our simulation results based on 3D finitedifference time-domain method also show that up to 1.61-times enhancement in ηextraction can be achieved by the use of 3D-printed lens of various dimensions as compared to conventional structure without the lens.

  19. Efficient and stable solution-processed planar perovskite solar cells via contact passivation

    KAUST Repository

    Tan, Hairen

    2017-02-03

    Planar perovskite solar cells (PSCs) made entirely via solution processing at low temperatures (<150°C) offer promise for simple manufacturing, compatibility with flexible substrates, and perovskite-based tandem devices. However, these PSCs require an electron-selective layer that performs well with similar processing. We report a contact-passivation strategy using chlorine-capped TiO2 colloidal nanocrystal film that mitigates interfacial recombination and improves interface binding in low-temperature planar solar cells. We fabricated solar cells with certified efficiencies of 20.1 and 19.5% for active areas of 0.049 and 1.1 square centimeters, respectively, achieved via low-temperature solution processing. Solar cells with efficiency greater than 20% retained 90% (97% after dark recovery) of their initial performance after 500 hours of continuous room-temperature operation at their maximum power point under 1-sun illumination (where 1 sun is defined as the standard illumination at AM1.5, or 1 kilowatt/square meter).

  20. A graded catalytic-protective layer for an efficient and stable water-splitting photocathode

    Science.gov (United States)

    Gu, Jing; Aguiar, Jeffery A.; Ferrere, Suzanne; Steirer, K. Xerxes; Yan, Yong; Xiao, Chuanxiao; Young, James L.; Al-Jassim, Mowafak; Neale, Nathan R.; Turner, John A.

    2017-01-01

    Achieving solar-to-hydrogen efficiencies above 15% is key for the commercial success of photoelectrochemical water-splitting devices. While tandem cells can reach those efficiencies, increasing the catalytic activity and long-term stability remains a significant challenge. Here we show that annealing a bilayer of amorphous titanium dioxide (TiOx) and molybdenum sulfide (MoSx) deposited onto GaInP2 results in a photocathode with high catalytic activity (current density of 11 mA cm-2 at 0 V versus the reversible hydrogen electrode under 1 sun illumination) and stability (retention of 80% of initial photocurrent density over a 20 h durability test) for the hydrogen evolution reaction. Microscopy and spectroscopy reveal that annealing results in a graded MoSx/MoOx/TiO2 layer that retains much of the high catalytic activity of amorphous MoSx but with stability similar to crystalline MoS2. Our findings demonstrate the potential of utilizing a hybridized, heterogeneous surface layer as a cost-effective catalytic and protective interface for solar hydrogen production.

  1. Energy-level matching of Fe(III) ions grafted at surface and doped in bulk for efficient visible-light photocatalysts.

    Science.gov (United States)

    Liu, Min; Qiu, Xiaoqing; Miyauchi, Masahiro; Hashimoto, Kazuhito

    2013-07-10

    Photocatalytic reaction rate (R) is determined by the multiplication of light absorption capability (α) and quantum efficiency (QE); however, these two parameters generally have trade-off relations. Thus, increasing α without decreasing QE remains a challenging issue for developing efficient photocatalysts with high R. Herein, using Fe(III) ions grafted Fe(III) doped TiO2 as a model system, we present a novel method for developing visible-light photocatalysts with efficient R, utilizing the concept of energy level matching between surface-grafted Fe(III) ions as co-catalysts and bulk-doped Fe(III) ions as visible-light absorbers. Photogenerated electrons in the doped Fe(III) states under visible-light efficiently transfer to the surface grafted Fe(III) ions co-catalysts, as the doped Fe(III) ions in bulk produced energy levels below the conduction band of TiO2, which match well with the potential of Fe(3+)/Fe(2+) redox couple in the surface grafted Fe(III) ions. Electrons in the surface grafted Fe(III) ions efficiently cause multielectron reduction of adsorbed oxygen molecules to achieve high QE value. Consequently, the present Fe(III)-FexTi1-xO2 nanocomposites exhibited the highest visible-light R among the previously reported photocatalysts for decomposition of gaseous organic compounds. The high R can proceed even under commercial white-light emission diode irradiation and is very stable for long-term use, making it practically useful. Further, this efficient method could be applied in other wide-band gap semiconductors, including ZnO or SrTiO3, and may be potentially applicable for other photocatalysis systems, such as water splitting, CO2 reduction, NOx removal, and dye decomposition. Thus, this method represents a strategic approach to develop new visible-light active photocatalysts for practical uses.

  2. Improved Light Extraction Efficiency by Photonic Crystal Arrays on Transparent Contact Layer Using Focused Ion Beams

    International Nuclear Information System (INIS)

    Wu, G.M.; Tsai, B.H.; Kung, S.F.; Wu, C.F.

    2011-01-01

    Nitride-based thin-film materials have become increasingly important for the high brightness light-emitting diode applications. The improvements in light extraction and lower power consumption are highly desired. Although the internal quantum efficiency of GaN-based LED has been relatively high, only a small fraction of light can be extracted. In this study, a new design of two-dimensional photonic crystal array has been prepared on the top transparent contact layer of indium-tin oxide film to improve the light extraction efficiency using focused ion beam. The acceleration voltage of the Ga dual-beam nanotechnology system SMI 3050 was 30 kV and the ion beam current was 100 pA. The cylindrical air holes had the diameter of 150 nm and depth of 100 nm. The micro photoluminescence analysis results showed that the light output intensity could be 1.5 times of that of the non-patterned control sample. In addition, the structural damage from the focused ion beam drilling of GaN step could be eliminated. The excellent I-V characteristics have been maintained, and the external light extraction efficiency would be still improved for the LED devices. (author)

  3. Silicon nanocrystal-based photonic crystal slabs with broadband and efficient directional light emission.

    Science.gov (United States)

    Ondič, L; Varga, M; Pelant, I; Valenta, J; Kromka, A; Elliman, R G

    2017-07-18

    Light extraction from a thin planar layer can be increased by introducing a two-dimensional periodic pattern on its surface. This structure, the so-called photonic crystal (PhC) slab, then not only enhances the extraction efficiency of light but can direct the extracted emission into desired angles. Careful design of the structures is important in order to have a spectral overlap of the emission with extraction (leaky) modes. We show that by fabricating PhC slabs with optimized dimensions from silicon nanocrystals (SiNCs) active layers, the extraction efficiency of vertical light emission from SiNCs at a particular wavelength can be enhanced ∼ 11 times compared to that of uncorrugated SiNCs-rich layer. More importantly, increased light emission can be obtained in a broad spectral range and, simultaneously, the extracted light can stay confined within relatively narrow angle around the normal to the sample plane. We demonstrate experimentally and theoretically that the physical origin of the enhancement is such that light originating from SiNCs first couples to leaky modes of the PhCs and is then efficiently extracted into the surrounding.

  4. Hierarchical 3C-SiC nanowires as stable photocatalyst for organic dye degradation under visible light irradiation

    International Nuclear Information System (INIS)

    Zhang, Judong; Chen, Jianjun; Xin, Lipeng; Wang, Mingming

    2014-01-01

    Graphical abstract: The photocatalytic performance was enhanced by hierarchical nanostructural SiC nanowires due to the increased specific surface areas and efficient incident light scattering. The positive effect of SiO 2 layer growth on the surface of nanowires during the catalytic process on the high decolorization efficiency of SiC nanowires was attributed to SiO 2 surface oxygen vacancies. -- Highlights: • High decolorization rate of methylene blue using hierarchical 3C-SiC nanowires was obtained. • The effect of methylene blue with different concentration to catalytic result was investigated. • The photocatalytic reaction mechanism of degrading methylene blue was explained. • The SiO 2 layer generating on nanowire surface in the catalytic process was analyzed. -- Abstract: 3C-SiC nanowires with hierarchical structure were synthesized by sol–gel carbothermal reduction method. The photocatalytic property of SiC nanowires was investigated. 3C-SiC hierarchical nanowires exhibited an enhanced photocatalytic activity by accelerating the photocatalytic degradation of methylene blue solution under visible light irradiation. Methylene blue was degraded efficiently after 5 h irradiation over the photocatalyst. The photocatalytic activity was affected by the initial concentration of the methylene blue solution. Silicon dioxide layer was observed on the surface of nanowires after the catalytic process. The positive effect of SiO 2 surface oxygen vacancies and 3C-SiC hierarchical nanostructures on the high decolorization efficiency of SiC nanowires was discussed. The detailed photocatalytic redox processes were also explained

  5. Efficient Sub-Bandgap Light Absorption and Signal Amplification in Silicon Photodetectors

    Science.gov (United States)

    Liu, Yu-Hsin

    This thesis focuses on two areas in silicon photodetectors, the first being enhancing the sub-bandgap light absorption of IR wavelenghts in silicon, and the second being intrinsic signal amplification in silicon photodetectors. Both of these are achieved using heavily doped p-n junction devices which create localized states that relax the k-selection rule of indirect bandgap material. The probability of transitions between impurity band and the conduction/valence band would be much more efficient than the one between band-to-band transition. The waveguide-coupled epitaxial p-n photodetector was demonstrated for 1310 nm wavelength detection. Incorporated with the Franz-Keldysh effect and the quasi-confined epitaxial layer design, an absorption coefficient around 10 cm-1 has been measured and internal quantum efficiency nearly 100% at -2.5V. The absorption coefficient is calculated from the wave function of the electron and hole in p-n diode. The heavily doped impurity wave function can be formulated as a delta function, and the quasi-confined conduction band energy states, and the wave function on each level can be obtained from the Silvaco software. The calculated theoretical absorption coefficient increases with the increasing applied bias and the doping concentration, which matches the experimental results. To solve the issues of large excess noise and high operation bias for avalanche photodiodes based on impact ionization, I presented a detector using the Cycling Excitation Process (CEP) for signal amplification. This can be realized in a heavily doped and highly compensated Si p-n junction, showing ultra high gain about 3000 at very low bias (<4 V), and possessing an intrinsic, phonon-mediated regulation process to keep the device stable without any quenching device required in today's Geiger-mode avalanche detectors. The CEP can be formulated with the rate equations in conduction bands and impurity states. The gain expression, which is a function of the

  6. Efficient light emitting devices based on phosphorescent partially doped emissive layers

    KAUST Repository

    Yang, Xiaohui

    2013-05-29

    We report efficient organic light emitting devices employing an ultrathin phosphor emissive layer. The electroluminescent spectra of these devices can be tuned by introducing a low-energy emitting phosphor layer into the emission zone. Devices with the emissive layer consisting of multiple platinum-complex/spacer layer cells show a peak external quantum efficiency of 18.1%, which is among the best EQE values for platinum-complex based light emitting devices. Devices with an ultrathin phosphor emissive layer show stronger luminance decay with the operating time compared to the counterpart devices having a host-guest emissive layer.

  7. Determination of gas recovery efficiency at two Danish landfills by performing downwind methane measurements and stable carbon isotopic analysis

    DEFF Research Database (Denmark)

    Fathi Aghdam, Ehsan; Fredenslund, Anders Michael; Chanton, Jeffrey

    2017-01-01

    In this study, the total methane (CH4) generation rate and gas recovery efficiency at two Danish landfills were determined by field measurements. The landfills are located close to each other and are connected to the same gas collection system. The tracer gas dispersion method was used...... for quantification of CH4 emissions from the landfills, while the CH4 oxidation efficiency in the landfill cover layers was determined by stable carbon isotopic technique. The total CH4 generation rate was estimated by a first-order decay model (Afvalzorg) and was compared with the total CH4 generation rate...... determined by field measurements. CH4 emissions from the two landfills combined ranged from 29.1 to 49.6 kg CH4/h. The CH4 oxidation efficiency was 6–37%, with an average of 18% corresponding to an average CH4 oxidation rate of 8.1 kg CH4/h. The calculated gas recovery efficiency was 59–76%, indicating...

  8. High Performance and Energy Efficient Traffic Light Controller Design Using FPGA

    DEFF Research Database (Denmark)

    Pandey, Sujeet; Shrivastav, Vivek Kumar; Sharma, Rashmi

    2017-01-01

    In this work, Verilog is used as hardware description language for implementation of traffic light controller. It shows Red, Green and Yellow color at a predefined interval. Technology scaling is used as energy efficient technique. We have used 90nm, 65nm, 40nm and 28nm technology based FPGA...... and then we have analyzed power consumption for traffic light controller on different FPGA. Leakage power is in range of 97.5-99% of total power consumption by traffic light controller on Virtex-7 FPGA. Signal power, clock power and IOs power are almost negligible. Power dissipation is measured on XPOWER...

  9. Combining light-harvesting with detachability in high-efficiency thin-film silicon solar cells.

    Science.gov (United States)

    Ram, Sanjay K; Desta, Derese; Rizzoli, Rita; Bellettato, Michele; Lyckegaard, Folmer; Jensen, Pia B; Jeppesen, Bjarke R; Chevallier, Jacques; Summonte, Caterina; Larsen, Arne Nylandsted; Balling, Peter

    2017-06-01

    Efforts to realize thin-film solar cells on unconventional substrates face several obstacles in achieving good energy-conversion efficiency and integrating light-management into the solar cell design. In this report a technique to circumvent these obstacles is presented: transferability and an efficient light-harvesting scheme are combined for thin-film silicon solar cells by the incorporation of a NaCl layer. Amorphous silicon solar cells in p-i-n configuration are fabricated on reusable glass substrates coated with an interlayer of NaCl. Subsequently, the solar cells are detached from the substrate by dissolution of the sacrificial NaCl layer in water and then transferred onto a plastic sheet, with a resultant post-transfer efficiency of 9%. The light-trapping effect of the surface nanotextures originating from the NaCl layer on the overlying solar cell is studied theoretically and experimentally. The enhanced light absorption in the solar cells on NaCl-coated substrates leads to significant improvement in the photocurrent and energy-conversion efficiency in solar cells with both 350 and 100 nm thick absorber layers, compared to flat-substrate solar cells. Efficient transferable thin-film solar cells hold a vast potential for widespread deployment of off-grid photovoltaics and cost reduction.

  10. Cost-efficient light control for production of two campanula species

    DEFF Research Database (Denmark)

    Kjær, Katrine Heinsvig; Ottosen, Carl-Otto; Jørgensen, Bo Nørregaard

    2011-01-01

    A cost-efficient light control system based on weather forecasts, electricity prices and daily photosynthesis integral (DPI) was evaluated for application in the commercial production of the long-day (LD) plant Campanula portenschlagiana ‘Blue Get Mee’ and C. cochlearifolia ‘Blue Wonder...... irradiance and the market price on electricity. The set points of DPI in the three treatments were 300, 450 and 600 mmol CO2 m−2 leaf d−1 and the treatments were compared with a traditional LD 19-h treatment. The DPI-based light control strategy resulted in very irregular light patterns including daily...... in LD species grown under low light intensities. Growth in terms of carbon gain was marginally affected by the irregular light and a 25% reduction in electricity costs was achieved without major reductions in plant quality in spring. Our results illustrate that plant production of LD species can...

  11. Use of space interlayer in phosphorescent organic light-emitting diodes to improve efficiency and reduce efficiency roll-off

    International Nuclear Information System (INIS)

    Guo, Kunping; Wei, Bin; Chen, Changbo; Peng, Cuiyun; Yang, Lianqiao; Sun, Chang; Cai, Miao; Zhang, Xiaowen

    2016-01-01

    Typical phosphorescent organic light-emitting diodes (PhOLEDs) encounter efficiency roll-off problems and detrimentally degrades the device performance for practical applications particularity at high-brightness lightening. Here, we report high efficiency and reduced efficiency roll-off PhOLEDs by employing both 4,4′,4″-tris-( N -carbazolyl)-triphenylamine (TCTA) and 1,3,5-tris(2- N -phenylbenzimidazolyl)benzene (TPBi) as transporting, hosting and space interlayer (SIL) materials. The use of SIL blending TCTA into TPBi enables the current efficiency roll-up from 57.8 to 60.1 cd A −1 with luminance increasing from 10.0 to 1143.0 cd m −2 . In particular, the current efficiency drops  <10% from 1143.0 to 5020.0 cd m −2 . In addition, the red-emitting sensitized dye further demonstrates that the SIL is dominant in expanding the dual exciton formation zone and suppressing efficiency roll-off. Also, the hole/electron balance can be manipulated by adjusting the doping ratio of the two materials in the SIL. (paper)

  12. Use of space interlayer in phosphorescent organic light-emitting diodes to improve efficiency and reduce efficiency roll-off

    Science.gov (United States)

    Guo, Kunping; Chen, Changbo; Sun, Chang; Peng, Cuiyun; Yang, Lianqiao; Cai, Miao; Zhang, Xiaowen; Wei, Bin

    2016-06-01

    Typical phosphorescent organic light-emitting diodes (PhOLEDs) encounter efficiency roll-off problems and detrimentally degrades the device performance for practical applications particularity at high-brightness lightening. Here, we report high efficiency and reduced efficiency roll-off PhOLEDs by employing both 4,4‧,4″-tris-(N-carbazolyl)-triphenylamine (TCTA) and 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBi) as transporting, hosting and space interlayer (SIL) materials. The use of SIL blending TCTA into TPBi enables the current efficiency roll-up from 57.8 to 60.1 cd A-1 with luminance increasing from 10.0 to 1143.0 cd m-2. In particular, the current efficiency drops  <10% from 1143.0 to 5020.0 cd m-2. In addition, the red-emitting sensitized dye further demonstrates that the SIL is dominant in expanding the dual exciton formation zone and suppressing efficiency roll-off. Also, the hole/electron balance can be manipulated by adjusting the doping ratio of the two materials in the SIL.

  13. Chlorine-functionalized carbon dots for highly efficient photodegradation of pollutants under visible-light irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Shengliang, E-mail: hsliang@yeah.net [School of Material Science and Engineering, North University of China, Taiyuan 030051 (China); Ding, Yanli [School of Material Science and Engineering, North University of China, Taiyuan 030051 (China); Chang, Qing, E-mail: changneu@gmail.com [School of Material Science and Engineering, North University of China, Taiyuan 030051 (China); Yang, Jinlong [State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084 (China); Lin, Kui, E-mail: linkui@tju.edu.cn [Analytical Instrumentation Center, Tianjin University, Tianjin 300072 (China)

    2015-11-15

    Graphical abstract: Chlorine-functionalized carbon dots (Cl-CDs) were synthesized through the substitution reaction. Cl-CDs show highly photocatalytic activity under visible-light irradiation, and can quickly degrade phthalocyanine with the thermal and chemical stability. This work suggests that surface engineering of carbon dots with heteroatoms can be used to enhance their photochemical properties. - Highlights: • Chlorine-functionalized carbon dots (Cl-CDs) were synthesized by substitution reaction. • Cl-CDs show highly photocatalytic activity under visible-light irradiation. • The thermally and chemically stable phthalocyanine is even photodegraded by Cl-CDs. - Abstract: Chlorine-functionalized carbon dots (Cl-CDs) were prepared by the substitution reaction between Cl radicals into thionyl chloride molecules and carbon dots with containing OH/COOH groups at their surface (O-CDs). The obtained Cl-CDs with a size of 2–5 nm contain 2–3% Cl atoms and emit blue light. Compared with amine-functionalzed carbon dots (N-CDs) and O-CDs, Cl-CDs exhibit much higher photocatalytic activity under visible-light irradiation. The thermally and chemically stable phthalocyanine can be even degraded quickly through Cl-CDs. This work suggests that surface engineering of carbon dots with heteroatoms can be used to enhance their photochemical properties.

  14. A nano-graphite cold cathode for an energy-efficient cathodoluminescent light source

    Directory of Open Access Journals (Sweden)

    Alexander N. Obraztsov

    2013-08-01

    Full Text Available The development of new types of light sources is necessary in order to meet the growing demands of consumers and to ensure an efficient use of energy. The cathodoluminescence process is still under-exploited for light generation because of the lack of cathodes suitable for the energy-efficient production of electron beams and appropriate phosphor materials. In this paper we propose a nano-graphite film material as a highly efficient cold cathode, which is able to produce high intensity electron beams without energy consumption. The nano-graphite film material was produced by using chemical vapor deposition techniques. Prototypes of cathodoluminescent lamp devices with a construction optimized for the usage of nano-graphite cold cathodes were developed, manufactured and tested. The results indicate prospective advantages of this type of lamp and the possibility to provide advanced power efficiency as well as enhanced spectral and other characteristics.

  15. Improving the efficiency of red phosphorescent organic light emitting diodes by exciton management

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yi-Lu; Wang, Zhibin; Helander, Michael G.; Qiu, Jacky; Lu, Zheng-Hong [Department of Materials Science and Engineering, University of Toronto, 184 College St., M5S 3E4, Toronto (Canada); Puzzo, Danny P. [Department of Chemistry, University of Toronto, 80 St George St., M5S 3H6, Toronto (Canada); Castrucci, Jeffrey [Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, M5S 3E5, Toronto (Canada)

    2012-12-15

    Phosphorescent organic light emitting diodes (PHOLEDs) have undergone remarkable development from both academia and industry in the past decade. Nevertheless, devices with higher efficiency remain highly desirable for energy-efficient general lighting as well as low power consumption LED backlight applications. In this respect, several groups have conducted complex device engineering designs such as doping of the transport layers to increase charge carrier mobility, incorporation of blocking layers to confine excitons/charge carriers, or use of multiple emissive layers to widen the emission zone, in order to achieve higher device performances. In this work, we report an alternative and relatively simple approach to improve the efficiency of red PHOLEDs by exciton management to attain a high external quantum efficiency (EQE) of >20%. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. NIR light-induced tumor phototherapy using photo-stable ICG delivery system based on inorganic hybrid.

    Science.gov (United States)

    Zhang, Huijuan; Zhang, Xiaoge; Zhu, Xing; Chen, Jianjiao; Chen, Qianqian; Zhang, Hongling; Hou, Lin; Zhang, Zhenzhong

    2018-01-01

    NIR responsive inorganic hybrid (Ti@GO) was synthesized. It could absorb NIR light and convert it into local hyperthermia and ROS synchronously. Ti@GO was firstly developed as a photosensitizer and a photothermal agent to realize tumor PTT and PDT. For anti-tumor application, HA was grafted on Ti@GO simultaneously as water solubility improver and tumor targeting moiety. ICG was chosen as a model drug. Results demonstrated that HA-Ti@GO could remarkably improve ICG stability and drug accumulation in 4T1 cells, enhance tumor phototherapy efficiency and reduce light-associated side effects. HA-Ti@GO/ICG under NIR laser irradiation showed a significant decreased cell viability of 20.7±2.6% and a high DNA damage degree of 82.4±8.3%. Moreover, in vivo results showed that HA-Ti@GO/ICG plus NIR laser achieved almost complete tumor regression on 4T1 tumor-bearing mice, with a tumor volume of 67.0 mm 3 . Taken together, our study provided a promising strategy to realize synergistic PTT/PDT tumor therapy with a single NIR light. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Efficient blue organic light-emitting devices based on oligo(phenylenevinylene)

    Science.gov (United States)

    Zhang, Yingfang; Cheng, Gang; Chen, Shufen; Li, Yan; Zhao, Yi; Liu, Shiyong; He, Feng; Tian, Leilei; Ma, Yuguang

    2006-05-01

    Highly bright and efficient blue organic light-emitting devices based on two oligo(phenylenevinylene) derivatives, 1,4-di(4'-N,N-diphenylaminostyryl)benzene (DPA-DSB) and 2,5,2',5'-tetrastyryl-biphenyl (TSB), are fabricated. Using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) combined with 4,4',4″-tri(N-carbazolyl) triphenylamine as the hole-transporting layer and DPA-DSB doped TSB as the blue emitter, a maximum luminous efficiency of 12.2 cd/A (corresponding to an external quantum efficiency of 6.2%) and a maximum power efficiency of 6.39lm/W are obtained. The maximum brightness of 17350cd/m2 is attained. These fairly high brightness and efficiencies are due to the efficient energy transfer from TSB to DPA-DSB and depression of concentration quenching by doping.

  18. Graphite oxide-TiO{sub 2} nanocomposite and its efficient visible-light-driven photocatalytic hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Peng; Zhang Qinggang; Zhang Xungao [College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072 (China); Peng Tianyou, E-mail: typeng@whu.edu.cn [College of Chemistry and Molecular Science, Wuhan University, Wuhan 430072 (China)

    2012-03-05

    Highlights: Black-Right-Pointing-Pointer GO-TiO{sub 2} nanocomposites were fabricated by a facile hydrothermal process. Black-Right-Pointing-Pointer The implanted GO expand the spectral responsive range of TiO{sub 2} to visible light for H{sub 2} production. Black-Right-Pointing-Pointer As a result, stable photocatalytic H{sub 2} production efficiency were obtained over GO-TiO{sub 2}. - Abstract: Graphite oxide (GO)-TiO{sub 2} nanocomposite was prepared by a facile hydrothermal process and was characterized by X-ray powder diffraction, Transmission electron microscopy, UV-vis diffusion reflectance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. TiO{sub 2} particles with average particle size of {approx}20 nm in the nanocomposites are attached to the surface of GO and/or intercalated into the interlayer of GO. The obtained GO-TiO{sub 2} was used as photocatalyst for H{sub 2} production under visible light ({lambda} {>=} 420 nm) irradiation, and an optimal photocatalytic H{sub 2} production rate of 380 {mu}mol h{sup -1} can be obtained over 2 wt% GO-TiO{sub 2}. The encouraging results presented here demonstrate that GO can serve as visible-light-driven photocatalyst and photosensitizer to expand the photoresponsive range of TiO{sub 2} to visible light for H{sub 2} production. The possible mechanism for H{sub 2} production was proposed for better understanding the visible-light-driven photocatalytic behaviour of the GO-TiO{sub 2} nanocomposite.

  19. Efficient and stable, structurally inverted poly(3-hexylthiopen): [6,6]-phenyl-C61-butyric acid methyl ester heterojunction solar cells with fibrous like poly(3-hexylthiopen)

    International Nuclear Information System (INIS)

    Bandara, Jayasundera; Shankar, Karthik; Grimes, Craig A.; Thelakkat, Mukundan

    2011-01-01

    We investigated an inverted organic photovoltaic device structure in which a densely packed ∼ 100 nm thin TiO 2 layer on fluorine doped conducting glass serves as anode and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)/Au layer on top of the active layer serves as cathode. The active layer is comprised of a blend of poly(3-hexylthiopene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The rectification behavior of such a device is improved significantly and injection losses are minimized compared to devices without any compact TiO 2 layer. Moreover, nanostructured P3HT active layer was achieved in-situ by spin coating concentrated pure P3HT and P3HT:PCBM blend and solar cell performances on thickness of the active layer were also investigated. For the inverted solar cells constructed with different concentrations of P3HT and PCBM keeping the P3HT:PCBM ratio 1:0.8 (wt.%), the highest short circuit current and efficiency was observed when the P3HT and PCBM concentration was equal to 1.5 (wt.%) and 1.2 (wt.%) respectively. This leads to highly stable and reproducible power conversion efficiency above 3.7% at 100 mW/cm 2 light intensity under AM 1.5 conditions.

  20. Constructing Efficient and Stable Perovskite Solar Cells via Interconnecting Perovskite Grains.

    Science.gov (United States)

    Hou, Xian; Huang, Sumei; Ou-Yang, Wei; Pan, Likun; Sun, Zhuo; Chen, Xiaohong

    2017-10-11

    A high-quality perovskite film with interconnected perovskite grains was obtained by incorporating terephthalic acid (TPA) additive into the perovskite precursor solution. The presence of TPA changed the crystallization kinetics of the perovskite film and promoted lateral growth of grains in the vicinity of crystal boundaries. As a result, sheet-shaped perovskite was formed and covered onto the bottom grains, which made some adjacent grains partly merge together to form grains-interconnected perovskite film. Perovskite solar cells (PSCs) with TPA additive exhibited a power conversion efficiency (PCE) of 18.51% with less hysteresis, which is obviously higher than that of pristine cells (15.53%). PSCs without and with TPA additive retain 18 and 51% of the initial PCE value, respectively, aging for 35 days exposed to relative humidity 30% in air without encapsulation. Furthermore, MAPbI 3 film with TPA additive shows superior thermal stability to the pristine one under 100 °C baking. The results indicate that the presence of TPA in perovskite film can greatly improve the performance of PSCs as well as their moisture resistance and thermal stability.

  1. Efficient and stable transformation of Lactuca sativa L. cv. Cisco (lettuce) plastids.

    Science.gov (United States)

    Kanamoto, Hirosuke; Yamashita, Atsushi; Asao, Hiroshi; Okumura, Satoru; Takase, Hisabumi; Hattori, Masahira; Yokota, Akiho; Tomizawa, Ken-Ichi

    2006-04-01

    Transgenic plastids offer unique advantages in plant biotechnology, including high-level foreign protein expression. However, broad application of plastid genome engineering in biotechnology has been largely hampered by the lack of plastid transformation systems for major crops. Here we describe the development of a plastid transformation system for lettuce, Lactuca sativa L. cv. Cisco. The transforming DNA carries a spectinomycin-resistance gene (aadA) under the control of lettuce chloroplast regulatory expression elements, flanked by two adjacent lettuce plastid genome sequences allowing its targeted insertion between the rbcL and accD genes. On average, we obtained 1 transplastomic lettuce plant per bombardment. We show that lettuce leaf chloroplasts can express transgene-encoded GFP to approximately 36% of the total soluble protein. All transplastomic T0 plants were fertile and the T1 progeny uniformly showed stability of the transgene in the chloroplast genome. This system will open up new possibilities for the efficient production of edible vaccines, pharmaceuticals, and antibodies in plants.

  2. The efficiency, energy intensity and visual impact of the accent lighting in the retail grocery stores

    Directory of Open Access Journals (Sweden)

    Ľudmila Nagyová

    2014-11-01

    Full Text Available Over the last few years, topics of displaying, presentation, lighting, energy saving and issues related to the environment while selling the fresh food (fruits, vegetable, bakery products, meat are becoming an important matter among traders. However, just bigger companies with transnational capital have devoted their attention to this issue yet. Generally, the energy costs make up 70% of operating costs in retail stores where the cooling system and lighting are the most energy consuming. Accent lighting in modern retails is largely involved in the overall design and atmosphere in shops and plays a crucial role in presenting the goods as well. Using of accent lighting can draw the customer's attention to a specific part of the sales area and achieve the overall harmonization in the store. With the rational using of combination of energy saving and effective accent lighting retailers can achieve not only attractive presentation of displayed products but also appreciable savings in the operation of their stores. It is the only factor that can be exactly measured and controlled. Using a Colour and Lux Meters we found out the intensity and color temperature of accent lighting used in domestic and foreign retail chains for the different kinds of fresh food products. Based on the obtained values we have compiled graphs, which are showing visual comfort. We also identified different types of accent lighting, which we assigned to their impact on emotional involvement of consumers. The starting points were the tests we conducted in simulated laboratory conditions. While searching of a compromise between effective and energy efficient accent lighting we take into consideration consumers' emotional response as well as the annual electricity consumption of different types of light sources. At the end we recommend options for energy-efficient, effective and spectacular lighting while using the optimal number of light sources and their logical organization

  3. Energy efficient biological air cleaning for farm stable ventilation; Energieffektiv biologisk luftrensning til staldventilation

    Energy Technology Data Exchange (ETDEWEB)

    Groenborg Nicolaisen, C.; Hansen, Mads P.R. [Teknologisk Institut, Aarhus (Denmark); Stroem, J.; Soerensen, Keld [DXT. Danish Exergy Technology A/S, Skoerping (Denmark); Goetke, C. [Lokalenergi Aarhus, Viby J. (Denmark); Morsing, S.; Soerensen, Lars C. [SKOV A/S, Roslev (Denmark); Ladegaerd Jensen, T.; Pedersen, Poul [Videncenter for svineproduktion, Copenhagen (Denmark)

    2013-05-01

    The project has been designed to reduce energy consumption for air purification by 30% while having a payback period of maximum 3 years. The project has achieved very significant results which are far above the target. Particularly satisfying is the wide range of new components that are launched in late 2012. By implementing the newly developed system at 100% cleaning (LPC 13 ventilators and Dynamic multistep control) in relation to Best Practice (SKOV's original system with DA600 fans) in a concrete pigsty, a saving of 61% and a simple payback of 1.7 years is achieved. Similarly, it is found that the energy used for pump operation can be reduced by 37% with the new Dynamic sprinkling control. At 20% cleaning a potential saving of 15% per year and a payback period of between 0 and 5 years was found, which is dependent on the desired performance as the capacities in the bio-filter's upper capacity range between 26 thousand to 30 thousand m3 / h entails costs for an additional extraction unit in the new solution. Furthermore, the newly developed components proved highly suitable for standard installations without air cleaning where a savings potential is 53% and the payback period 1.5 years. Product-wise, the project formed the basis for the development of: 1. New energy-efficient ventilation units (LPC11, 12,13) that are suitable for air purification; 2. A new energy-saving control principle (Dynamic Multi-Step) which is particularly suitable for low-energy ventilators; 3. A new energy-saving flow measurement system for ventilating ducts (Dynamic air to the central exhaust); 4. An energy-saving pressure control in common ducts (pressure control as a function of outside temperature); 5. Proposal for a new energy-saving pump operation for sprinkling of biological filters (Dynamic sprinkling). (LN)

  4. EFFECT OF ENERGY EFFICIENT LIGHT SOURCES ON READABILITY OF STUDENTS – AN EXPERIMENTAL APPROACH

    Directory of Open Access Journals (Sweden)

    SATHYA P.

    2016-01-01

    Full Text Available The objective of this paper is to investigate the effect of light sources on readability of students using psychophysical methods. Light sources such as Compact Fluorescent Lamp (CFL and Light Emitting Diode lamp (LED of same power rating were used in this research work because of their high lighting efficiency and uniformity of illuminance compared to that of Incandescent lamp (IL and florescent lamp (FL. A group of prospective students having normal vision, and abnormal vision like myopia, hypermetropia and astigmatism were involved in the test process. Three types of test like Snellen visual acuity, Color contrast test and Readability test were conducted on student participants under different lighting conditions. Test results showed the visibility and color contrast sensitivity of the students were high in the LED illumination. The quantitative measure of readability under different circumstances showed that the lightness difference on text under different color combination and font size, affected their readability. The computed average results confirmed that the luminance and color contrast were improved in LED illumination and also proved a high readability measure in the experimentation. Both the results of psychophysical test were proven that LED lighting was the best lighting system suitable for color distinction and readability.

  5. Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels.

    Science.gov (United States)

    Dickman, Elizabeth M; Newell, Jennifer M; González, María J; Vanni, Michael J

    2008-11-25

    The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not been tested experimentally in food chains with 3 or more trophic levels. In a field experiment manipulating light, nutrients, and food-chain length, we show that FCE is constrained by algal food quality and food-chain length. FCE across 3 trophic levels (phytoplankton to carnivorous fish) was highest under low light and high nutrients, where algal quality was best as indicated by taxonomic composition and nutrient stoichiometry. In 3-level systems, FCE was constrained by the efficiency at which both herbivores and carnivores converted food into production; a strong nutrient effect on carnivore efficiency suggests a carryover effect of algal quality across 3 trophic levels. Energy transfer efficiency from algae to herbivores was also higher in 2-level systems (without carnivores) than in 3-level systems. Our results support the hypothesis that FCE is strongly constrained by light, nutrients, and food-chain length and suggest that carryover effects across multiple trophic levels are important. Because many environmental perturbations affect light, nutrients, and food-chain length, and many ecological services are mediated by FCE, it will be important to apply these findings to various ecosystem types.

  6. Zinc oxide nanostructures and its nano-compounds for efficient visible light photo-catalytic processes

    Science.gov (United States)

    Adam, Rania E.; Alnoor, Hatim; Elhag, Sami; Nur, Omer; Willander, Magnus

    2017-02-01

    Zinc oxide (ZnO) in its nanostructure form is a promising material for visible light emission/absorption and utilization in different energy efficient photocatalytic processes. We will first present our recent results on the effect of varying the molar ratio of the synthesis nutrients on visible light emission. Further we will use the optimized conditions from the molar ration experiments to vary the synthesis processing parameters like stirring time etc. and the effect of all these parameters in order to optimize the efficiency and control the emission spectrum are investigated using different complementary techniques. Cathodoluminescence (CL) is combined with photoluminescence (PL) and electroluminescence (EL) as the techniques to investigate and optimizes visible light emission from ZnO/GaN light emitting diodes. We will then show and discuss our recent finding of the use of high quality ZnO nanoparticles (NPs) for efficient photo-degradation of toxic dyes using the visible spectra, namely with a wavelength up to 800 nm. In the end, we show how ZnO nanorods (NRs) are used as the first template to be transferred to bismuth zinc vanadate (BiZn2VO6). The BiZn2VO6 is then used to demonstrate efficient and cost effective hydrogen production through photoelectrochemical water splitting using solar radiation.

  7. Enclosed outdoor photobioreactors: light regime, photosynthetic efficiency, scale-up, and future prospects

    NARCIS (Netherlands)

    Janssen, M.G.J.; Tramper, J.; Mur, L.R.; Wijffels, R.H.

    2003-01-01

    Enclosed outdoor photobioreactors need to be developed and designed for large-scale production of phototrophic microorganisms. Both light regime and photosynthetic efficiency were analyzed in characteristic examples of state-of-the-art pilot-scale photobioreactors. In this study it is shown that

  8. Efficiency simulations of thin film chalcogenide photovoltaic cells for different indoor lighting conditions

    International Nuclear Information System (INIS)

    Minnaert, B.; Veelaert, P.

    2011-01-01

    Photovoltaic (PV) energy is an efficient natural energy source for outdoor applications. However, for indoor applications, the efficiency of PV cells is much lower. Typically, the light intensity under artificial lighting conditions is less than 10 W/m 2 as compared to 100-1000 W/m 2 under outdoor conditions. Moreover, the spectrum is different from the outdoor solar spectrum. In this context, the question arises whether thin film chalcogenide photovoltaic cells are suitable for indoor use. This paper contributes to answering that question by comparing the power output of different thin film chalcogenide solar cells with the classical crystalline silicon cell as reference. The comparisons are done by efficiency simulation based on the quantum efficiencies of the solar cells and the light spectra of typical artificial light sources i.e. an LED lamp, a 'warm' and a 'cool' fluorescent tube and a common incandescent and halogen lamp, which are compared to the outdoor AM 1.5 spectrum as reference.

  9. Efficient all solid-state continuous-wave yellow-orange light source

    DEFF Research Database (Denmark)

    Janousek, Jiri; Johansson, Sandra; Tidemand-Lichtenberg, Peter

    2005-01-01

    We present highly efficient sum-frequency generation between two CW IR lasers using periodically poled KTP. The system is based on the 1064 and 1342 nm laser-lines of two Nd:YVO4 lasers. This is an all solid-state light source in the yellow-orange spectral range. The system is optimized in terms ...

  10. Quantum efficiency harmonic analysis of exciton annihilation in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Price, J. S.; Giebink, N. C., E-mail: ncg2@psu.edu [Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2015-06-29

    Various exciton annihilation processes are known to impact the efficiency roll-off of organic light emitting diodes (OLEDs); however, isolating and quantifying their contribution in the presence of other factors such as changing charge balance continue to be a challenge for routine device characterization. Here, we analyze OLED electroluminescence resulting from a sinusoidal dither superimposed on the device bias and show that nonlinearity between recombination current and light output arising from annihilation mixes the quantum efficiency measured at different dither harmonics in a manner that depends uniquely on the type and magnitude of the annihilation process. We derive a series of analytical relations involving the DC and first harmonic external quantum efficiency that enable annihilation rates to be quantified through linear regression independent of changing charge balance and evaluate them for prototypical fluorescent and phosphorescent OLEDs based on the emitters 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran and platinum octaethylporphyrin, respectively. We go on to show that, in most cases, it is sufficient to calculate the needed quantum efficiency harmonics directly from derivatives of the DC light versus current curve, thus enabling this analysis to be conducted solely from standard light-current-voltage measurement data.

  11. Photosynthesis, light use efficiency, and yield of reduced-chlorophyll soybean mutants in field conditions

    Science.gov (United States)

    Reducing chlorophyll (chl) content may improve the conversion efficiency of absorbed radiation into biomass (ec) and therefore yield in dense monoculture crops by improving light penetration and distribution within the canopy. Modeling suggests that reducing chl content may also reduce leaf temperat...

  12. Highly Efficient p-i-n Type Organic Light-emitting Diodes Using ...

    African Journals Online (AJOL)

    set of three quantum states of a system, each with total spin S=1. The process of charge injection and recombination in OLEDs (Tang and Van Slyke,. 1987) results in the generation of singlets and triplets. Furthermore, high efficiency electro-phosphorescent organic light-emitting diodes using phosphorescent dyes have ...

  13. Energy efficient lighting in the residences of staff of the University of ...

    African Journals Online (AJOL)

    CFL) as an energy-efficient lighting system. The results of the study show that even though academics in the university have received information about the use of CFLs as a way of saving energy, very few show interest in their use. It is inferred ...

  14. Highly efficient and stable inverted perovskite solar cell employing PEDOT:GO composite layer as a hole transport layer.

    Science.gov (United States)

    Yu, Jae Choul; Hong, Ji A; Jung, Eui Dae; Kim, Da Bin; Baek, Soo-Min; Lee, Sukbin; Cho, Shinuk; Park, Sung Soo; Choi, Kyoung Jin; Song, Myoung Hoon

    2018-01-18

    The beneficial use of a hole transport layer (HTL) as a substitution for poly(3,4-ethlyenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) is regarded as one of the most important approaches for improving the stability and efficiency of inverted perovskite solar cells. Here, we demonstrate highly efficient and stable inverted perovskite solar cells by applying a GO-doped PEDOT:PSS (PEDOT:GO) film as an HTL. The high performance of this solar cell stems from the excellent optical and electrical properties of the PEDOT:GO film, including a higher electrical conductivity, a higher work function related to the reduced contact barrier between the perovskite layer and the PEDOT:GO layer, enhanced crystallinity of the perovskite crystal, and suppressed leakage current. Moreover, the device with the PEDOT:GO layer showed excellent long-term stability in ambient air conditions. Thus, the enhancement in the efficiency and the excellent stability of inverted perovskite solar cells are promising for the eventual commercialization of perovskite optoelectronic devices.

  15. Navigational efficiency of nocturnal Myrmecia ants suffers at low light levels.

    Directory of Open Access Journals (Sweden)

    Ajay Narendra

    Full Text Available Insects face the challenge of navigating to specific goals in both bright sun-lit and dim-lit environments. Both diurnal and nocturnal insects use quite similar navigation strategies. This is despite the signal-to-noise ratio of the navigational cues being poor at low light conditions. To better understand the evolution of nocturnal life, we investigated the navigational efficiency of a nocturnal ant, Myrmecia pyriformis, at different light levels. Workers of M. pyriformis leave the nest individually in a narrow light-window in the evening twilight to forage on nest-specific Eucalyptus trees. The majority of foragers return to the nest in the morning twilight, while few attempt to return to the nest throughout the night. We found that as light levels dropped, ants paused for longer, walked more slowly, the success in finding the nest reduced and their paths became less straight. We found that in both bright and dark conditions ants relied predominantly on visual landmark information for navigation and that landmark guidance became less reliable at low light conditions. It is perhaps due to the poor navigational efficiency at low light levels that the majority of foragers restrict navigational tasks to the twilight periods, where sufficient navigational information is still available.

  16. An Efficient and Stable Hydrophobic Molecular Cobalt Catalyst for Water Electro-oxidation at Neutral pH

    KAUST Repository

    Chen, Ba-Tian

    2016-06-14

    The synthesis of a library of molecular water oxidation catalysts based on the Co complex of tris(2-benzimidazolylmethyl)amine is described. Hydrophobicity was identified as the key variable in mediating the catalytic competence of the complexes. The change in this parameter correlates with both the conformational mobility of the ligand core and the structural changes in the local solvent environment around the metal site. The optimal Co complex identified is hydrophobic, because of three semifluorinated side chains. It catalyzes water electro-oxidation efficiently at neutral pH, with an overpotential of 390 mV and a turnover frequency (TOF) of 1.83 s-1 in the absence of soluble Co salts. The catalyst can be immobilized through physisorption, and it remains stable in prolonged electrolysis experiments. © 2016 American Chemical Society.

  17. Environmental friendly high efficient light source. Plasma lamp. 2006 annual report

    Energy Technology Data Exchange (ETDEWEB)

    Courret, G.

    2006-07-01

    This annual report for 2006 for the Swiss Federal Office of Energy (SFOE) reports on work being done on the development of a high-efficiency source of light based on the light emission of a plasma. The report presents a review of work done in 2006, including thermodynamics and assessment of the efficiency of the magnetron, tests with small bulbs, study of the standing wave ratio (microwave fluxes) and the development of a new coupling system to allow ignition in very small bulbs. Also, knowledge on the fillings of the bulb and induced effects of the modulator were gained. The development of a second generation of modulator to obtain higher efficiency at lower power is noted.

  18. Transportation Energy Futures Series. Potential for Energy Efficiency Improvement Beyond the Light-Duty-Vehicle Sector

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, A. D. [Argonne National Lab. (ANL), Argonne, IL (United States); Patel, D. M. [Argonne National Lab. (ANL), Argonne, IL (United States); Bertram, K. M. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2013-02-01

    Considerable research has focused on energy efficiency and fuel substitution options for light-duty vehicles, while much less attention has been given to medium- and heavy-duty trucks, buses, aircraft, marine vessels, trains, pipeline, and off-road equipment. This report brings together the salient findings from an extensive review of literature on future energy efficiency options for these non-light-duty modes. Projected activity increases to 2050 are combined with forecasts of overall fuel efficiency improvement potential to estimate the future total petroleum and greenhouse gas (GHG) emissions relative to current levels. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  19. Transportation Energy Futures Series: Potential for Energy Efficiency Improvement Beyond the Light-Duty-Vehicle Sector

    Energy Technology Data Exchange (ETDEWEB)

    Vyas, A. D.; Patel, D. M.; Bertram, K. M.

    2013-03-01

    Considerable research has focused on energy efficiency and fuel substitution options for light-duty vehicles, while much less attention has been given to medium- and heavy-duty trucks, buses, aircraft, marine vessels, trains, pipeline, and off-road equipment. This report brings together the salient findings from an extensive review of literature on future energy efficiency options for these non-light-duty modes. Projected activity increases to 2050 are combined with forecasts of overall fuel efficiency improvement potential to estimate the future total petroleum and greenhouse gas (GHG) emissions relative to current levels. This is one of a series of reports produced as a result of the Transportation Energy Futures (TEF) project, a Department of Energy-sponsored multi-agency project initiated to pinpoint underexplored strategies for abating GHGs and reducing petroleum dependence related to transportation.

  20. Improving Control Efficiency of Dynamic Street Lighting by Utilizing the Dual Graph Grammar Concept

    Directory of Open Access Journals (Sweden)

    Igor Wojnicki

    2018-02-01

    Full Text Available The paper introduces a definition of dual graph grammar. It enables two graphs to share information in a synchronized way. A smart city example application, which is an outdoor lighting control system utilizing the dual graph grammar, is also demonstrated. The system controls dimming of street lights which is based on traffic intensity. Each luminaire’s light level is adjusted individually to comply with the lighting norms to ensure safety. Benefits of applying the dual graph grammar are twofold. First, it increases expressive power of the mathematical model that the system uses. It becomes possible to take into account complex geographical distribution of sensors and logical dependencies among them. Second, it increases the system’s efficiency by reducing the problem size during run-time. Experimental results show a reduction of the computation time by a factor of 2.8. The approach has been verified in practice.

  1. Graded-host phosphorescent light-emitting diodes with high efficiency and reduced roll-off

    Directory of Open Access Journals (Sweden)

    S. W. Liu

    2012-03-01

    Full Text Available We demonstrated graded-host phosphorescent organic light-emitting diodes with high efficiency and reduced efficiency roll-off. The emissive layer of the graded host device consists of both electron and hole transport type hosts, 1,3,5-tris(N-phenylbenzimidazole-2-ylbenzene (TPBI and 4,4′,4′′-tris(N-carbazolyltriphenylamine, respectively, with graded composition, and the phosphorescent red emitter bis(2-phenylquinoline (acetylacetonate iridium(III, which was uniformly doped into the graded host matrix. The graded host device shows improved quantum efficiency and power efficiency with significantly reduced efficiency roll-off as compared to the unipolar-host and double layer heterojunction host devices.

  2. Using a Fuzzy Light Sensor to Improve the Efficiency of Solar Panels

    Science.gov (United States)

    Suryono; Suseno, Jatmiko Endro; Sulistiati, Ainie Khuriati Riza; Prahara, Tahan

    2018-02-01

    Solar panel efficiency can be increased by improving the quality of photovoltaic material, the effectiveness of electronic circuit, and the light source tracking model. This research is aimed at improving the quality of solar panels by tracking light source using a fuzzy logic sensor. A fuzzy light sensor property is obtained from two LDR (light dependent resistor) light sensors installed in parallel to each other and is given a light separator in between them. Both sensors are mounted on a solar panel. Sensor output is acquired using a 12 bit ADC from an ATSAM3XE microcontroller and is then sent to a computer using WIFI radio. A PID (Proportional-Integral-Derivative) control algorithm is used to manage the position of the solar panel in line with the input given by the fuzzy light sensor. This control mechanism works based on the margin of fuzzy membership from both sensors that is used to move a motor DC that in turn moves the solar panel. Experimental results show a characteristically symmetrical fuzzy membership of both sensors with a reflected correlation of R=0.9981 after gains from both sensors are arranged with a program. Upon being tested in the field, this system was capable of improving the performance of solar panels in gaining power compared to their original fixed position. The discrepancy was evident when the angle of incoming sunlight approached both 0° and 180°. Further calculations of data acquired by the fuzzy light sensor show increased solar panel power efficiency by up to 5.6%.

  3. Analysis of federal policy options for improving US lighting energy efficiency: Commercial and residential buildings

    Energy Technology Data Exchange (ETDEWEB)

    Atkinson, B.A.; McMahon, J.E.; Mills, E.; Chan, P.; Chan, T.W.; Eto, J.H.; Jennings, J.D.; Koomey, J.G.; Lo, K.W.; Lecar, M.; Price, L.; Rubinstein, F.; Sezgen, O.; Wenzel, T.

    1992-12-01

    The US Department of Energy (DOE) has recognized the opportunity to achieve energy, economic, and environmental benefits by promoting energy-efficient lighting through federal policies, including lighting standards, financial incentives, and information programs. To assist in this process, the Office of Conservation and Renewable Energy`s Office of Codes and Standards invited Lawrence Berkeley Laboratory to assess prospective national impacts for a variety of policy options. Some progress has already been made in developing lighting policies at both the federal and state levels. The US DOE`s Office of Building Technologies has evaluated lighting efficiency incentives as part of its analysis for the National Energy Strategy. Fluorescent and incandescent lamp standards are included in the national Energy Policy Act of 1992 (P.L. 102-486, October 24, 1992). A few states have analyzed or implemented lamp and luminaire standards. Many policy-related issues merit further investigation. For example, there is considerable debate over issues such as mandatory or voluntary standards versus component labeling and other education-oriented strategies. Several different technologies are involved that interact with each other-lamps (incandescent, compact fluorescent, and HID), ballasts (for fluorescent and HID lamps), and fixtures with reflectors and lenses. Control systems and operation patterns must also be considered (timers, automated dimming, or occupancy sensors). Lighting applications are diverse, ranging from offices, restaurants, hallways, hospital operating rooms, to exterior lights. Lighting energy use influences heating and cooling requirements in buildings. Successful lighting system design must also address interactions between architectural design elements and daylighting availability. Proper system installation and ongoing operation and maintenance are crucial. The economic aspects of the preceding points must also be considered for policy making.

  4. Analysis of federal policy options for improving US lighting energy efficiency: Commercial and residential buildings

    Energy Technology Data Exchange (ETDEWEB)

    Atkinson, B.A.; McMahon, J.E.; Mills, E.; Chan, P.; Chan, T.W.; Eto, J.H.; Jennings, J.D.; Koomey, J.G.; Lo, K.W.; Lecar, M.; Price, L.; Rubinstein, F.; Sezgen, O.; Wenzel, T.

    1992-12-01

    The US Department of Energy (DOE) has recognized the opportunity to achieve energy, economic, and environmental benefits by promoting energy-efficient lighting through federal policies, including lighting standards, financial incentives, and information programs. To assist in this process, the Office of Conservation and Renewable Energy's Office of Codes and Standards invited Lawrence Berkeley Laboratory to assess prospective national impacts for a variety of policy options. Some progress has already been made in developing lighting policies at both the federal and state levels. The US DOE's Office of Building Technologies has evaluated lighting efficiency incentives as part of its analysis for the National Energy Strategy. Fluorescent and incandescent lamp standards are included in the national Energy Policy Act of 1992 (P.L. 102-486, October 24, 1992). A few states have analyzed or implemented lamp and luminaire standards. Many policy-related issues merit further investigation. For example, there is considerable debate over issues such as mandatory or voluntary standards versus component labeling and other education-oriented strategies. Several different technologies are involved that interact with each other-lamps (incandescent, compact fluorescent, and HID), ballasts (for fluorescent and HID lamps), and fixtures with reflectors and lenses. Control systems and operation patterns must also be considered (timers, automated dimming, or occupancy sensors). Lighting applications are diverse, ranging from offices, restaurants, hallways, hospital operating rooms, to exterior lights. Lighting energy use influences heating and cooling requirements in buildings. Successful lighting system design must also address interactions between architectural design elements and daylighting availability. Proper system installation and ongoing operation and maintenance are crucial. The economic aspects of the preceding points must also be considered for policy making.

  5. A functional form-stable phase change composite with high efficiency electro-to-thermal energy conversion

    International Nuclear Information System (INIS)

    Wu, Wenhao; Huang, Xinyu; Li, Kai; Yao, Ruimin; Chen, Renjie; Zou, Ruqiang

    2017-01-01

    Graphical abstract: The thermal conductivity of PU was enhanced to 43 times of the pristine value by encapsulation in a PGF, PU@PGF can be used for highly efficient electro-to-heat energy conversion and storage with the highest energy storage efficiency up to 85%. - Highlights: • The composite exhibits an in-situ solid-solid phase change behavior. • The enthalpy of polyurethane is enhanced within the matrix. • The thermal conductivity of the composite is 43 times as much as that of the polyurethane. • Supercooling of polyurethane is greatly reduced. • The composite is applied to cold protection as a wear layer. - Abstract: A novel solid-to-solid phase change composite brick was prepared by combination of polyurethane (PU) and pitch-based graphite foam (PGF). The carbonaceous support, which can be used for mass production, not only greatly improves the thermal conductivity but promote electro-to-heat conversion efficiency of organic phase change materials (PCMs). Our composite retained the enthalpy of PCM and exhibited a greatly reduced supercooling temperature. The novel composite was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The enthalpy of polyurethane has increased about 8.6% after infiltrating into graphite foam. The composite was very stable during thermal cycle test, and the electro-to-heat conversion efficiency achieves to 85% at lower voltages (1.5–1.8 V), which can vastly reduce energy consumption. The as-prepared composite was used in a wear layer to test its performance comparing with normal fabric.

  6. Light dilution via wavelength management for efficient high-density photobioreactors.

    Science.gov (United States)

    Ooms, Matthew D; Graham, Percival J; Nguyen, Brian; Sargent, Edward H; Sinton, David

    2017-06-01

    The spectral distribution of light influences microalgae productivity; however, development of photobioreactors has proceeded largely without regard to spectral optimization. Here, we use monochromatic light to quantify the joint influence of path length, culture density, light intensity, and wavelength on productivity and efficiency in Synechococcus elongatus. The productivity of green light was ∼4× that of red at the highest levels of culture density, depth, and light intensity. This performance is attributed to the combination of increased dilution and penetration of this weakly absorbed wavelength over a larger volume fraction of the reactor. In contrast, red light outperformed other wavelengths in low-density cultures with low light intensities. Low-density cultures also adapted more rapidly to reduce absorption of longer wavelengths, allowing for prolonged cultivation. Taken together, these results indicate that, particularly for artificially lit photobioreactors, wavelength needs to be included as a critical operational parameter to maintain optimal performance. Biotechnol. Bioeng. 2017;114: 1160-1169. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  7. Stable angular emission spectra in white organic light-emitting diodes using graphene/PEDOT:PSS composite electrode.

    Science.gov (United States)

    Cho, Hyunsu; Lee, Hyunkoo; Lee, Jonghee; Sung, Woo Jin; Kwon, Byoung-Hwa; Joo, Chul-Woong; Shin, Jin-Wook; Han, Jun-Han; Moon, Jaehyun; Lee, Jeong-Ik; Cho, Seungmin; Cho, Nam Sung

    2017-05-01

    In this work, we suggest a graphene/ poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) composite as a transparent electrode for stabilizing white emission of organic light-emitting diodes (OLEDs). Graphene/PEDOT:PSS composite electrodes have increased reflectance when compared to graphene itself, but their reflectance is still lower than that of ITO itself. Changes in the reflectance of the composite electrode have the advantage of suppressing the angular spectral distortion of white emission OLEDs and achieving an efficiency of 16.6% for white OLEDs, comparable to that achieved by graphene-only electrodes. By controlling the OLED structure to compensate for the two-beam interference effect, the CIE color coordinate change (Δxy) of OLEDs based on graphene/PEDOT:PSS composite electrodes is 0.018, less than that based on graphene-only electrode, i.e.,0.027.

  8. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation.

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-27

    Light isotopes separation, such as (3)He/(4)He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as (3)He/(4)He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high (3)He/(4)He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

  9. Luminostat operation: a tool to maximize microalgae photosynthetic efficiency in photobioreactors during the daily light cycle?

    Science.gov (United States)

    Cuaresma, María; Janssen, Marcel; van den End, Evert Jan; Vílchez, Carlos; Wijffels, René H

    2011-09-01

    The luminostat regime has been proposed as a way to maximize light absorption and thus to increase the microalgae photosynthetic efficiency within photobioreactors. In this study, simulated outdoor light conditions were applied to a lab-scale photobioreactor in order to evaluate the luminostat control under varying light conditions. The photon flux density leaving the reactor (PFD(out)) was varied from 4 to 20 μmol photons m(-2)s(-1)and the productivity and photosynthetic efficiency of Chlorella sorokiniana were assessed. Maximal volumetric productivity (1.22g kg(-1)d(-1)) and biomass yield on PAR photons (400-700 nm) absorbed (1.27 g mol(-1)) were found when PFD(out) was maintained between 4 and 6 μmol photons m(-2)s(-1). The resultant photosynthetic efficiency was comparable to that already reported in a chemostat-controlled reactor. A strict luminostat regime could not be maintained under varying light conditions. Further modifications to the luminostat control are required before application under outdoor conditions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

  11. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    Science.gov (United States)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application. PMID:26813491

  12. Broadband Light Collection Efficiency Enhancement of Carbon Nanotube Excitons Coupled to Metallo-Dielectric Antenna Arrays

    Energy Technology Data Exchange (ETDEWEB)

    Shayan, Kamran [Department; Rabut, Claire [Department; Kong, Xiaoqing [Department; Li, Xiangzhi [Department; Luo, Yue [Department; Mistry, Kevin S. [National Renewable; Blackburn, Jeffrey L. [National Renewable; Lee, Stephanie S. [Department; Strauf, Stefan [Department

    2017-11-09

    The realization of on-chip quantum networks ideally requires lossless interfaces between photons and solid-state quantum emitters. We propose and demonstrate on-chip arrays of metallo-dielectric antennas (MDA) that are tailored toward efficient and broadband light collection from individual embedded carbon nanotube quantum emitters by trapping air gaps on chip that form cavity modes. Scalable implementation is realized by employing polymer layer dry-transfer techniques that avoid solvent incompatibility issues, as well as a planar design that avoids solid-immersion lenses. Cryogenic measurements demonstrate 7-fold enhanced exciton intensity when compared to emitters located on bare wafers, corresponding to a light collection efficiency (LCE) up to 92% in the best case (average LCE of 69%) into a narrow output cone of +/-15 degrees that enables a priori fiber-to-chip butt coupling. The demonstrated MDA arrays are directly compatible with other quantum systems, particularly 2D materials, toward enabling efficient on-chip quantum light sources or spin-photon interfaces requiring unity light collection, both at cryogenic or room temperature.

  13. Measuring of filtration efficiency of nonwoven textiles in volume from scattered light by seeding particles

    Directory of Open Access Journals (Sweden)

    Sidlof P.

    2013-04-01

    Full Text Available This paper deals with the method which calculates a filtration efficiency of nonwoven textiles from scattered light intensity by seeding particles. Thefiltration efficiency is commonly measured by particle counters. Samples of liquid or gas are taken during a test in front of and behind a filtration material. The concentration of particles is measured and the filtration efficiency is calculated. The filtration efficiency does not have to be uniform in itswhole surface. The uniformity of filtration is another indicator of a quality of filtration materials. Measurements described in this article were performed on a water filtration setup which enables optical access to the place where the filtration material is mounted. Pictures of illuminated seeding particles are made by a laser sheet and a camera. Visualisation of the filtration process enables measuring of the efficiency of separation versus time and also versus two-dimensional position in case of use of a traverse mechanism. The filtration textiles were tested by 1 μm seeding particles. Mean value of light intensity and number of bright pixels in evaluative areas during image analysis were obtained. On the basis of these data, the filtration efficiency iscalculated. The best image analysis method was chosen.

  14. Evaluation of energy efficiency in street lighting: model proposition considering climate variability

    Directory of Open Access Journals (Sweden)

    Amaury Caruzzo

    2015-12-01

    Full Text Available This paper assesses the impacts of climate variability on efficient electricity consumption in street lighting in Brazil. The Climate Demand Method (CDM was applied, and the energy savings achieved by Brazil’s National Efficient Street Lighting Program (ReLuz in 2005 were calculated, considering the monthly climatology of sunshine duration, disaggregated by county in Brazil. The total energy savings in street lighting in 2005 were estimated at 63 GWh/year or 1.39% higher than the value determined by ReLuz/Eletrobrás and there was a 15 MW reduction in demand in Brazil, considering the nearly 393,000 points in ReLuz served in 2005. The results indicate that, besides the difference in latitude, climate variability in different county increases the daily usage of street lighting up to 19%. Furthermore, Brazil’s large size means that seasonality patterns in energy savings are not homogeneous, and there is a correlation between the monthly variability in sunshine duration and the latitude of mesoregions. The CDM was also shown to be suitable for ranking mesoregions with the highest levels of energy saving lighting.

  15. Modeling light use efficiency in a subtropical mangrove forest equipped with CO2 eddy covariance

    Directory of Open Access Journals (Sweden)

    J. G. Barr

    2013-03-01

    Full Text Available Despite the importance of mangrove ecosystems in the global carbon budget, the relationships between environmental drivers and carbon dynamics in these forests remain poorly understood. This limited understanding is partly a result of the challenges associated with in situ flux studies. Tower-based CO2 eddy covariance (EC systems are installed in only a few mangrove forests worldwide, and the longest EC record from the Florida Everglades contains less than 9 years of observations. A primary goal of the present study was to develop a methodology to estimate canopy-scale photosynthetic light use efficiency in this forest. These tower-based observations represent a basis for associating CO2 fluxes with canopy light use properties, and thus provide the means for utilizing satellite-based reflectance data for larger scale investigations. We present a model for mangrove canopy light use efficiency utilizing the enhanced green vegetation index (EVI derived from the Moderate Resolution Imaging Spectroradiometer (MODIS that is capable of predicting changes in mangrove forest CO2 fluxes caused by a hurricane disturbance and changes in regional environmental conditions, including temperature and salinity. Model parameters are solved for in a Bayesian framework. The model structure requires estimates of ecosystem respiration (RE, and we present the first ever tower-based estimates of mangrove forest RE derived from nighttime CO2 fluxes. Our investigation is also the first to show the effects of salinity on mangrove forest CO2 uptake, which declines 5% per each 10 parts per thousand (ppt increase in salinity. Light use efficiency in this forest declines with increasing daily photosynthetic active radiation, which is an important departure from the assumption of constant light use efficiency typically applied in satellite-driven models. The model developed here provides a framework for estimating CO2 uptake by these forests from reflectance data and

  16. Modeling light use efficiency in a subtropical mangrove forest equipped with CO2 eddy covariance

    Science.gov (United States)

    Barr, J.G.; Engel, V.; Fuentes, J.D.; Fuller, D.O.; Kwon, H.

    2013-01-01

    Despite the importance of mangrove ecosystems in the global carbon budget, the relationships between environmental drivers and carbon dynamics in these forests remain poorly understood. This limited understanding is partly a result of the challenges associated with in situ flux studies. Tower-based CO2 eddy covariance (EC) systems are installed in only a few mangrove forests worldwide, and the longest EC record from the Florida Everglades contains less than 9 years of observations. A primary goal of the present study was to develop a methodology to estimate canopy-scale photosynthetic light use efficiency in this forest. These tower-based observations represent a basis for associating CO2 fluxes with canopy light use properties, and thus provide the means for utilizing satellite-based reflectance data for larger scale investigations. We present a model for mangrove canopy light use efficiency utilizing the enhanced green vegetation index (EVI) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) that is capable of predicting changes in mangrove forest CO2 fluxes caused by a hurricane disturbance and changes in regional environmental conditions, including temperature and salinity. Model parameters are solved for in a Bayesian framework. The model structure requires estimates of ecosystem respiration (RE), and we present the first ever tower-based estimates of mangrove forest RE derived from nighttime CO2 fluxes. Our investigation is also the first to show the effects of salinity on mangrove forest CO2 uptake, which declines 5% per each 10 parts per thousand (ppt) increase in salinity. Light use efficiency in this forest declines with increasing daily photosynthetic active radiation, which is an important departure from the assumption of constant light use efficiency typically applied in satellite-driven models. The model developed here provides a framework for estimating CO2 uptake by these forests from reflectance data and information about

  17. Energy stable and efficient finite-difference nonlinear multigrid schemes for the modified phase field crystal equation

    Science.gov (United States)

    Baskaran, Arvind; Hu, Zhengzheng; Lowengrub, John S.; Wang, Cheng; Wise, Steven M.; Zhou, Peng

    2013-10-01

    In this paper we present two unconditionally energy stable finite difference schemes for the modified phase field crystal (MPFC) equation, a sixth-order nonlinear damped wave equation, of which the purely parabolic phase field crystal (PFC) model can be viewed as a special case. The first is a convex splitting scheme based on an appropriate decomposition of the discrete energy and is first order accurate in time and second order accurate in space. The second is a new, fully second-order scheme that also respects the convex splitting of the energy. Both schemes are nonlinear but may be formulated from the gradients of strictly convex, coercive functionals. Thus, both are uniquely solvable regardless of the time and space step sizes. The schemes are solved by efficient nonlinear multigrid methods. Numerical results are presented demonstrating the accuracy, energy stability, efficiency, and practical utility of the schemes. In particular, we show that our multigrid solvers enjoy optimal, or nearly optimal complexity in the solution of the nonlinear schemes.

  18. Stable carbon isotope ratios and intrinsic water-use efficiency of Miocene fossil leaves compared to modern congeners

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, J.D.; Zhang, J.; Rember, W.C.; Jennings, D.; Larson, P. (Univ. of Idaho, Moscow, ID (United States))

    1994-06-01

    Miocene fossil leaves of forest trees were extracted from the Clarkia, Idaho fossil beds and their stable carbon isotope ratios were analyzed. Fossils had higher lignin concentrations and lower cellulose concentrations that modern leaves due to diagenesis and the HF used to extract the fossils. Therefore, [delta][sup 13]C of extracted fossil lignin was compared to that of modern lignin. Fossil lignin [delta][sup 13]C was significantly different from that of congeneric modern leaves (paired t-test, P<0.0001), but was 1.9% less negative. Gymnosperms (Metasequoia, Taxodium) were less negative than angiosperms (e.g., Magnolia, Quercus, Acer, Persea), but no difference between evergreen and deciduous species was detected. Using published estimates of the concentration and [delta][sup 13]C of atmospheric CO[sub 2] during the Miocene was estimated the CO[sub 2] partial pressure gradient across the stomata (intrinsic water-use efficiency). Intrinsic water-use efficiency was at least 70% higher during this past [open quotes]greenhouse[close quotes] period than at present.

  19. Tailoring the Energy Landscape in Quasi-2D Halide Perovskites Enables Efficient Green-Light Emission

    KAUST Repository

    Quan, Li Na

    2017-05-10

    Organo-metal halide perovskites are a promising platform for optoelectronic applications in view of their excellent charge-transport and bandgap tunability. However, their low photoluminescence quantum efficiencies, especially in low-excitation regimes, limit their efficiency for light emission. Consequently, perovskite light-emitting devices are operated under high injection, a regime under which the materials have so far been unstable. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield, even at low excitation intensities. We tailor the composition of quasi-2D perovskites to direct the energy transfer into the lowest-bandgap minority phase and to do so faster than it is lost to nonradiative centers. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm2, yielding a ratio of quantum yield to excitation intensity of 0.3 cm2/mW; this represents a decrease of 2 orders of magnitude in the excitation power required to reach high efficiency compared with the best prior reports. Using this strategy, we report light-emitting diodes with external quantum efficiencies of 7.4% and a high luminescence of 8400 cd/m2.

  20. Slow-light-enhanced energy efficiency for graphene microheaters on silicon photonic crystal waveguides.

    Science.gov (United States)

    Yan, Siqi; Zhu, Xiaolong; Frandsen, Lars Hagedorn; Xiao, Sanshui; Mortensen, N Asger; Dong, Jianji; Ding, Yunhong

    2017-02-09

    Slow light has been widely utilized to obtain enhanced nonlinearities, enhanced spontaneous emissions and increased phase shifts owing to its ability to promote light-matter interactions. By incorporating a graphene on a slow-light silicon photonic crystal waveguide, here we experimentally demonstrate an energy-efficient graphene microheater with a tuning efficiency of 1.07 nmmW -1 and power consumption per free spectral range of 3.99 mW. The rise and decay times (10-90%) are only 750 and 525 ns, which, to the best of our knowledge, are the fastest reported response times for microheaters in silicon photonics. The corresponding figure of merit of the device is 2.543 nW s, one order of magnitude better than results reported in previous studies. The influence of the length and shape of the graphene heater to the tuning efficiency is further investigated, providing valuable guidelines for enhancing the tuning efficiency of the graphene microheater.

  1. Tailoring the Energy Landscape in Quasi-2D Halide Perovskites Enables Efficient Green-Light Emission.

    Science.gov (United States)

    Quan, Li Na; Zhao, Yongbiao; García de Arquer, F Pelayo; Sabatini, Randy; Walters, Grant; Voznyy, Oleksandr; Comin, Riccardo; Li, Yiying; Fan, James Z; Tan, Hairen; Pan, Jun; Yuan, Mingjian; Bakr, Osman M; Lu, Zhenghong; Kim, Dong Ha; Sargent, Edward H

    2017-06-14

    Organo-metal halide perovskites are a promising platform for optoelectronic applications in view of their excellent charge-transport and bandgap tunability. However, their low photoluminescence quantum efficiencies, especially in low-excitation regimes, limit their efficiency for light emission. Consequently, perovskite light-emitting devices are operated under high injection, a regime under which the materials have so far been unstable. Here we show that, by concentrating photoexcited states into a small subpopulation of radiative domains, one can achieve a high quantum yield, even at low excitation intensities. We tailor the composition of quasi-2D perovskites to direct the energy transfer into the lowest-bandgap minority phase and to do so faster than it is lost to nonradiative centers. The new material exhibits 60% photoluminescence quantum yield at excitation intensities as low as 1.8 mW/cm 2 , yielding a ratio of quantum yield to excitation intensity of 0.3 cm 2 /mW; this represents a decrease of 2 orders of magnitude in the excitation power required to reach high efficiency compared with the best prior reports. Using this strategy, we report light-emitting diodes with external quantum efficiencies of 7.4% and a high luminescence of 8400 cd/m 2 .

  2. Highly efficient and simplified phosphorescence white organic light-emitting diodes based on synthesized deep-blue host and orange emitter

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Ja Ryong; Lee, Seok Jae; Hyung, Gun Woo; Kim, Bo Young; Lee, Dong Hyung [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Kim, Woo Young [Department of Green Energy and Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Lee, Kum Hee [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Yoon, Seung Soo, E-mail: ssyoon@skku.edu [Department of Chemistry, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Young Kwan, E-mail: kimyk@hongik.ac.kr [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of)

    2013-10-01

    The authors have demonstrated a highly efficient and stable phosphorescent white organic light-emitting diode (WOLED), which has been achieved by doping only one orange phosphorescent emitter, Bis(5-benzoyl-2-(4-fluorophenyl)pyridinato-C,N)iridium(III) acetylacetonate into an appropriate deep blue phosphorescent host, 4,4'-bis(4-(triphenylsilyl)phenyl)-1,1'-binaphthyl as an emitting layer (EML). The WOLED has been achieved by effective confinement of triplet excitons to emit a warm white color. The optimized WOLED, with a simple structure as a hole transporting layer-EML-electron transporting layer, showed a maximum luminous efficiency of 22.38 cd/A, a maximum power efficiency of 12.01 lm/W, a maximum external quantum efficiency of 7.32%, and CIEx,y coordinates of (0.38,0.42) at 500 cd/m{sup 2}, respectively. - Highlights: • Highly efficient phosphorescent white organic light-emitting diode (WOLED) • Single emitting layer consists of synthesized deep blue host and orange emitter • The WOLED with high EL efficiencies due to efficient triplet exciton confinement.

  3. Highly stable CsPbBr3 quantum dots coated with alkyl phosphate for white light-emitting diodes.

    Science.gov (United States)

    Xuan, Tongtong; Yang, Xianfeng; Lou, Sunqi; Huang, Junjian; Liu, Yong; Yu, Jinbo; Li, Huili; Wong, Ka-Leung; Wang, Chengxin; Wang, Jing

    2017-10-19

    Inorganic halide perovskite quantum dots (QDs) suffer from problems related to poor water stability and poor thermal stability. Here we developed a simple strategy to synthesize alkyl phosphate (TDPA) coated CsPbBr 3 QDs by using 1-tetradecylphosphonic acid both as the ligand for the CsPbBr 3 QDs and as the precursor for the formation of alkyl phosphate. These QDs not only retain a high photoluminescence quantum yield (PLQY, 68%) and narrow band emission (FHWM ∼ 22 nm) but also exhibit high stability against water and heat. The relative PL intensity of the QDs was maintained at 75% or 59% after being dispersed in water for 5 h or heated to 375 K (100 °C), respectively. Finally, white light-emitting diodes (WLEDs) with a high luminous efficiency of 63 lm W -1 and a wide color gamut (122% of NTSC) were fabricated by using green-emitting CsPbBr 3 /TDPA QDs and red-emitting K 2 SiF 6 :Mn 4+ phosphors as color converters. The luminous efficiency of the WLEDs remained at 90% after working under a relative humidity (RH) of 60% for 15 h, thereby showing promise for use as backlight devices in LCDs.

  4. Efficiency and stray light measurements and calculations of diffraction gratings for the ALS

    International Nuclear Information System (INIS)

    McKinney, W.R.; Mossessian, D.; Gullikson, E.; Heimann, P.

    1994-07-01

    Water cooled gratings manufactured for spherical grating monochromators of the Advanced Light Source beamlines 7.0, 8.0 and 9.0 were measured with the laser plasma source and reflectometer in the Center for X-ray Optics at LBL. The square-wave gratings are ion-milled into the polished electroless nickel surface after patterning by holographic photolithography. Absolute efficiency data are compared with exact electromagnetic theory calculation. Inter-order stray light and groove depths can be estimated from the measurements

  5. Highly Efficient Light-Emitting Diodes of Colloidal Metal-Halide Perovskite Nanocrystals beyond Quantum Size.

    Science.gov (United States)

    Kim, Young-Hoon; Wolf, Christoph; Kim, Young-Tae; Cho, Himchan; Kwon, Woosung; Do, Sungan; Sadhanala, Aditya; Park, Chan Gyung; Rhee, Shi-Woo; Im, Sang Hyuk; Friend, Richard H; Lee, Tae-Woo

    2017-07-25

    Colloidal metal-halide perovskite quantum dots (QDs) with a dimension less than the exciton Bohr diameter D B (quantum size regime) emerged as promising light emitters due to their spectrally narrow light, facile color tuning, and high photoluminescence quantum efficiency (PLQE). However, their size-sensitive emission wavelength and color purity and low electroluminescence efficiency are still challenging aspects. Here, we demonstrate highly efficient light-emitting diodes (LEDs) based on the colloidal perovskite nanocrystals (NCs) in a dimension > D B (regime beyond quantum size) by using a multifunctional buffer hole injection layer (Buf-HIL). The perovskite NCs with a dimension greater than D B show a size-irrespective high color purity and PLQE by managing the recombination of excitons occurring at surface traps and inside the NCs. The Buf-HIL composed of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) and perfluorinated ionomer induces uniform perovskite particle films with complete film coverage and prevents exciton quenching at the PEDOT:PSS/perovskite particle film interface. With these strategies, we achieved a very high PLQE (∼60.5%) in compact perovskite particle films without any complex post-treatments and multilayers and a high current efficiency of 15.5 cd/A in the LEDs of colloidal perovskite NCs, even in a simplified structure, which is the highest efficiency to date in green LEDs that use colloidal organic-inorganic metal-halide perovskite nanoparticles including perovskite QDs and NCs. These results can help to guide development of various light-emitting optoelectronic applications based on perovskite NCs.

  6. Highly efficient white organic light-emitting devices consisting of undoped ultrathin yellow phosphorescent layer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shengqiang [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Yu, Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Ma, Zhu; Zhao, Juan [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

    2013-02-15

    High-efficiency white organic light-emitting devices (WOLEDs) based on an undoped ultrathin yellow light-emitting layer and a doped blue light-emitting layer were demonstrated. While the thickness of blue light-emitting layer, formed by doping a charge-trapping phosphor, iridium(III) bis(4 Prime ,6 Prime -difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6) in a wide bandgap host, was kept constant, the thickness of neat yellow emissive layer of novel phosphorescent material, bis[2-(4-tertbutylphenyl)benzothiazolato-N,C{sup 2 Prime }]iridium (acetylacetonate) [(t-bt){sub 2}Ir(acac)] was varied to optimize the device performance. The optimized device exhibited maximum luminance, current efficiency and power efficiency of 24,000 cd/m{sup 2} (at 15.2 V), 79.0 cd/A (at 1550 cd/m{sup 2}) and 40.5 lm/W (at 1000 cd/m{sup 2}), respectively. Besides, the white-light emission covered a wide range of visible spectrum, and the Commission Internationale de l'Eclairage coordinates were (0.32, 0.38) with a color temperature of 5800 K at 8 V. Moreover, high external quantum efficiency was also obtained in the high-efficiency WOLEDs. The performance enhancement was attributed to the proper thickness of (t-bt){sub 2}Ir(acac) layer that enabled adequate current density and enough phosphorescent dye to trap electrons. - Highlights: Black-Right-Pointing-Pointer Highly efficient WOLEDs based on two complementary layers were fabricated. Black-Right-Pointing-Pointer The yellow emissive layer was formed by utilizing undoping system. Black-Right-Pointing-Pointer The blue emissive layer was made by host-guest doping system. Black-Right-Pointing-Pointer The thickness of the yellow emissive layer was varied to make device optimization. Black-Right-Pointing-Pointer The optimized device achieved high power efficiency of 40.5 lm/W.

  7. Highly Efficient and Stable Organic Solar Cells via Interface Engineering with a Nanostructured ITR-GO/PFN Bilayer Cathode Interlayer

    Directory of Open Access Journals (Sweden)

    Ding Zheng

    2017-08-01

    Full Text Available An innovative bilayer cathode interlayer (CIL with a nanostructure consisting of in situ thermal reduced graphene oxide (ITR-GO and poly[(9,9-bis(3′-(N,N-dimethylamionpropyl-2,7-fluorene-alt-2,7-(9,9-dioctyl fluorene] (PFN has been fabricated for inverted organic solar cells (OSCs. An approach to prepare a CIL of high electronic quality by using ITR-GO as a template to modulate the morphology of the interface between the active layer and electrode and to further reduce the work function of the electrode has also been realized. This bilayer ITR-GO/PFN CIL is processed by a spray-coating method with facile in situ thermal reduction. Meanwhile, the CIL shows a good charge transport efficiency and less charge recombination, which leads to a significant enhancement of the power conversion efficiency from 6.47% to 8.34% for Poly({4,8-bis[(2-ethylhexyloxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexylcarbonyl]thieno[3,4-b]thiophenediyl} (PTB7:[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM-based OSCs. In addition, the long-term stability of the OSC is improved by using the ITR-GO/PFN CIL when compared with the pristine device. These results indicate that the bilayer ITR-GO/PFN CIL is a promising way to realize high-efficiency and stable OSCs by using water-soluble conjugated polymer electrolytes such as PFN.

  8. Efficient and accurate laser shaping with liquid crystal spatial light modulators

    Energy Technology Data Exchange (ETDEWEB)

    Maxson, Jared M.; Bartnik, Adam C.; Bazarov, Ivan V. [Cornell Laboratory for Accelerator-Based Sciences and Education, Cornell University, Ithaca, New York 14853 (United States)

    2014-10-27

    A phase-only spatial light modulator (SLM) is capable of precise transverse laser shaping by either functioning as a variable phase grating or by serving as a variable mask via polarization rotation. As a phase grating, the highest accuracy algorithms, based on computer generated holograms (CGHs), have been shown to yield extended laser shapes with <10% rms error, but conversely little is known about the experimental efficiency of the method in general. In this work, we compare the experimental tradeoff between error and efficiency for both the best known CGH method and polarization rotation-based intensity masking when generating hard-edged flat top beams. We find that the masking method performs comparably with CGHs, both having rms error < 10% with efficiency > 15%. Informed by best practices for high efficiency from a SLM phase grating, we introduce an adaptive refractive algorithm which has high efficiency (92%) but also higher error (16%), for nearly cylindrically symmetric cases.

  9. Radiative Energy Budgets of Phototrophic Surface-Associated Microbial Communities and their Photosynthetic Efficiency Under Diffuse and Collimated Light.

    Science.gov (United States)

    Lichtenberg, Mads; Brodersen, Kasper E; Kühl, Michael

    2017-01-01

    We investigated the radiative energy budgets of a heterogeneous photosynthetic coral reef sediment and a compact uniform cyanobacterial biofilm on top of coastal sediment. By combining electrochemical, thermocouple and fiber-optic microsensor measurements of O 2 , temperature and light, we could calculate the proportion of the absorbed light energy that was either dissipated as heat or conserved by photosynthesis. We show, across a range of different incident light regimes, that such radiative energy budgets are highly dominated by heat dissipation constituting up to 99.5% of the absorbed light energy. Highest photosynthetic energy conservation efficiency was found in the coral sediment under low light conditions and amounted to 18.1% of the absorbed light energy. Additionally, the effect of light directionality, i.e., diffuse or collimated light, on energy conversion efficiency was tested on the two surface-associated systems. The effects of light directionality on the radiative energy budgets of these phototrophic communities were not unanimous but, resulted in local spatial differences in heat-transfer, gross photosynthesis, and light distribution. The light acclimation index, E k , i.e., the irradiance at the onset of saturation of photosynthesis, was >2 times higher in the coral sediment compared to the biofilm and changed the pattern of photosynthetic energy conservation under light-limiting conditions. At moderate to high incident irradiances, the photosynthetic conservation of absorbed energy was highest in collimated light; a tendency that changed in the biofilm under sub-saturating incident irradiances, where higher photosynthetic efficiencies were observed under diffuse light. The aim was to investigate how the physical structure and light propagation affected energy budgets and light utilization efficiencies in loosely organized vs. compact phototrophic sediment under diffuse and collimated light. Our results suggest that the optical properties and the

  10. Light vehicle energy efficiency programs and their impact on Brazilian CO2 emissions

    International Nuclear Information System (INIS)

    Wills, William; La Rovere, Emilio Lebre

    2010-01-01

    This paper analyses the impact of an energy efficiency program for light vehicles in Brazil on emissions of carbon dioxide (CO 2 ), the main greenhouse gas in the atmosphere. Several energy efficiency programs for light vehicles around the world are reviewed. The cases of Japan and Europe were selected for presentation here given their status as current and future world leaders in the control of passenger vehicle fuel consumption. The launching of the National Climate Change Plan and the pressure on the Brazilian car industry due to the world financial crisis make it a good time for the Brazilian government to implement such a program, and its various benefits are highlighted in this study. Three scenarios are established for Brazil covering the 2000-2030 period: the first with no efficiency goals, the second with the Japanese goals applied with a 10 years delay, and the third, with the Japanese goals applied with no delay. The consequences of a vehicular efficiency program and its middle and long-term effects on the consumption of energy and the CO 2 emissions are quantified and discussed. The simulation results indicate that efficiency goals may make an important contribution to reducing vehicular emissions and fuel consumption in Brazil, compared to a baseline scenario.

  11. Enhancement of efficiency and stability of phosphorescent OLEDs based on heterostructured light-emitting layers

    Energy Technology Data Exchange (ETDEWEB)

    Chin, Byung Doo, E-mail: bdchin@dankook.ac.kr [Department of Polymer Science and Engineering and Center for Photofunctional Energy Materials, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of)

    2011-03-23

    The light-emitting efficiency and stability of a phosphorescent organic light-emitting device (OLED), whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping influenced by heterostructured emissive layers, are studied. The variation of the material combination of the heterostructured emitter, both for mixed and double layer configuration, affects the charge injection behaviour, luminous efficiency and stability. Both double and mixed emitter configurations yield low-voltage and high-efficiency behaviour (51 lm W{sup -1} at 1000 cd m{sup -2}; 30 lm W{sup -1} at 10 000 cd m{sup -2}). Such an improvement in power efficiency at elevated brightness is sufficiently universal, while the enhancement of device half-lifetime is rather sensitive to the circumstantial layout of heterostructural emitters. With an optimal mixture of hole-transport type and electron-transport type, a half-lifetime of more than 2500 h at 4000 cd m{sup -2} is obtained, which is 8 times the half-lifetime of control devices with a single emitter structure. The origin and criterion for enhancement of efficiency and lifetime are discussed in terms of the carrier transport behaviour with a specific device architecture.

  12. Efficient charge balance in blue phosphorescent organic light emitting diodes by two types of mixed layer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hyung Jin; Lee, Ho Won; Lee, Song Eun; Sun, Yong; Hwang, Kyo Min; Yoo, Han Kyu; Lee, Sung Kyu [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Kim, Woo Young, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Kim, Young Kwan, E-mail: kimyk@hongik.ac.kr [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of)

    2015-07-31

    The authors have demonstrated a highly efficient and long-lifetime blue phosphorescent organic light emitting diode (PHOLED) that uses two types of mixed layers. The mixed layers play the role of carrier injection control and exciton generation zone extension. One of the layers is applied for mixing the hole transport layer (HTL) and host material at the HTL side for carrier injection control. The other works as a mixed electron transporting layer (ETL) and host material at the ETL side. The optimized blue PHOLED has been shown to achieve high performance owing to the mixed layer effects. It gave a maximum luminous efficiency of 25.55 cd/A, maximum external quantum efficiency of 13.05%, and lifetime of 7.24 h under 500 cd/m{sup 2}. These results indicate that applying mixed layers is a simple and efficient method that does not require significant structural change. - Highlights: • Highly efficient blue phosphorescent organic light-emitting diode (PHOLEDs) • Hole transporting layer consists with mixed layer for delayed hole injection • The blue PHOLEDs with long lifetime due to suppression of quenching process.

  13. Stable and efficient Q-compensated least-squares migration with compressive sensing, sparsity-promoting, and preconditioning

    Science.gov (United States)

    Chai, Xintao; Wang, Shangxu; Tang, Genyang; Meng, Xiangcui

    2017-10-01

    The anelastic effects of subsurface media decrease the amplitude and distort the phase of propagating wave. These effects, also referred to as the earth's Q filtering effects, diminish seismic resolution. Ignoring anelastic effects during seismic imaging process generates an image with reduced amplitude and incorrect position of reflectors, especially for highly absorptive media. The numerical instability and the expensive computational cost are major concerns when compensating for anelastic effects during migration. We propose a stable and efficient Q-compensated imaging methodology with compressive sensing, sparsity-promoting, and preconditioning. The stability is achieved by using the Born operator for forward modeling and the adjoint operator for back propagating the residual wavefields. Constructing the attenuation-compensated operators by reversing the sign of attenuation operator is avoided. The method proposed is always stable. To reduce the computational cost that is proportional to the number of wave-equation to be solved (thereby the number of frequencies, source experiments, and iterations), we first subsample over both frequencies and source experiments. We mitigate the artifacts caused by the dimensionality reduction via promoting sparsity of the imaging solutions. We further employ depth- and Q-preconditioning operators to accelerate the convergence rate of iterative migration. We adopt a relatively simple linearized Bregman method to solve the sparsity-promoting imaging problem. Singular value decomposition analysis of the forward operator reveals that attenuation increases the condition number of migration operator, making the imaging problem more ill-conditioned. The visco-acoustic imaging problem converges slower than the acoustic case. The stronger the attenuation, the slower the convergence rate. The preconditioning strategy evidently decreases the condition number of migration operator, which makes the imaging problem less ill-conditioned and

  14. Efficient interfacing of light and surface plasmon polaritons for quantum optics applications

    DEFF Research Database (Denmark)

    Eran, Kot

    oscillations propagating on the surface of metals have been shown to be useful in coupling to quantum dots, nanodiamond NV-centers defects and other quantum emitters. However, being lossy these modes too need to be efficiently coupled out to photons in order to facilitate experimental control of the system...... in a proximity to a metallic interface. Concentric grating rings then couple light propagating normal to the surface to a inward propagating plasmons, showing coupling efficiencies of 70% and enhancement of the emitters decay rate by up to 45 times that of the isolated emitter’s decay rate. Finally, we explore...

  15. Efficiency Enhancement of Gallium Arsenide Photovoltaics Using Solution-Processed Zinc Oxide Nanoparticle Light Scattering Layers

    Directory of Open Access Journals (Sweden)

    Yangsen Kang

    2015-01-01

    Full Text Available We demonstrate a high-throughput, solution-based process for subwavelength surface texturing of a III-V compound solar cell. A zinc oxide (ZnO nanoparticle ink is spray-coated directly on top of a gallium arsenide (GaAs solar cell. The nanostructured ZnO films have demonstrated antireflection and light scattering properties over the visible/near-infrared (NIR spectrum. The results show a broadband spectral enhancement of the solar cell external quantum efficiency (EQE, a 16% enhancement of short circuit current, and a 10% increase in photovoltaic efficiency.

  16. Efficiency Enhancement of Gallium Arsenide Photovoltaic Using Solution-Processed Zinc Oxide Nanoparticle Light Scattering Layers

    International Nuclear Information System (INIS)

    Kang, Y.; Huo, Y.; Chen, Y.; Christoforo, M. G.; Harris, J.S.; Liang, D.; Mehra, S.; Salleo, A.; Harris, J.S.; Harris, J.S.

    2015-01-01

    We demonstrate a high-throughput, solution-based process for sub wavelength surface texturing of a III-V compound solar cell. A zinc oxide (ZnO) nanoparticle ink is spray-coated directly on top of a gallium arsenide (GaAs) solar cell. The nano structured ZnO films have demonstrated antireflection and light scattering properties over the visible/near-infrared (NIR) spectrum. The results show a broadband spectral enhancement of the solar cell external quantum efficiency (EQE), a 16% enhancement of short circuit current, and a 10% increase in photovoltaic efficiency

  17. Improving the efficiency of GaP LED's which emit green light

    Science.gov (United States)

    Ladany, I.; Kressel, H.

    1972-01-01

    A study of techniques for preparing n-type material and junctions which yield the most consistent high diode efficiency values high lighted the role that Ga vacancies and/or associated defects play in reducing the green luminescent efficiency of n-type GaP. A useful method for obtaining good quality material was developed. It is shown that junction formation at high temperatures in a process where the n to p transition occurs without removing the substrate from the furnace yields devices superior to those obtained by diffusion or double epitaxy in the conventional manner previously used for GaP junction formation.

  18. Enhancement of mosquito trapping efficiency by using pulse width modulated light emitting diodes

    Science.gov (United States)

    Liu, Yu-Nan; Liu, Yu-Jen; Chen, Yi-Chian; Ma, Hsin-Yi; Lee, Hsiao-Yi

    2017-01-01

    In this study, a light-driving bug zapper is presented for well controlling the diseases brought by insects, such as mosquitoes. In order to have the device efficient to trap the insect pests in off-grid areas, pulse width modulated light emitting diodes (PWM-LED) combined with a solar power module are proposed and implemented. With specific PWM electric signals to drive the LED, it is found that no matter what the ability of catching insects or the consumed power efficiency can be enhanced thus. It is demonstrated that 40% of the UV LED consumed power and 25.9% of the total load power consumption can be saved, and the trapped mosquitoes are about 250% increased when the PWM method is applied in the bug zapper experiments.

  19. Physics of Efficiency Droop in GaN:Eu Light-Emitting Diodes.

    Science.gov (United States)

    Fragkos, Ioannis E; Dierolf, Volkmar; Fujiwara, Yasufumi; Tansu, Nelson

    2017-12-01

    The internal quantum efficiency (IQE) of an electrically-driven GaN:Eu based device for red light emission is analyzed in the framework of a current injection efficiency model (CIE). The excitation path of the Eu +3 ion is decomposed in a multiple level system, which includes the carrier transport phenomena across the GaN/GaN:Eu/GaN active region of the device, and the interactions among traps, Eu +3 ions and the GaN host. The identification and analysis of the limiting factors of the IQE are accomplished through the CIE model. The CIE model provides a guidance for high IQE in the electrically-driven GaN:Eu based red light emitters.

  20. Diffusion of new automotive technologies for improving energy efficiency in Brazil's light vehicle fleet

    International Nuclear Information System (INIS)

    Bastin, Cristina; Szklo, Alexandre; Rosa, Luiz Pinguelli

    2010-01-01

    Historically, Brazil has promoted the development and sales of light duty vehicles running on ethanol (firstly, ethanol-dedicated cars, and recently flexfuel cars). In the 1990s, the country also favored the sales of compact cars to middle and low-income classes. However, in the last years, the profile of vehicles sold in Brazil has converged towards larger and less-efficient vehicles. In 2008, Brazil launched the vehicle labeling program. Based on the outcomes of the historical programs oriented towards the development of automotive innovations, and on a survey conducted with the country's main auto makers, this article evaluates whether the vehicle labeling program will both improve the energy efficiency of light vehicles, and introduce new technologies. Our results indicate that, despite its virtuous intentions, the program will not control the tendency of rising fuel consumption of passenger cars sold in Brazil. Therefore, other policies are needed to boost innovations in Brazil's automotive industry. (author)

  1. Light-Regulated Electrochemical Sensor Array for Efficiently Discriminating Hazardous Gases.

    Science.gov (United States)

    Liang, Hongqiu; Zhang, Xin; Sun, Huihui; Jin, Han; Zhang, Xiaowei; Jin, Qinghui; Zou, Jie; Haick, Hossam; Jian, Jiawen

    2017-10-27

    Inadequate detection limit and unsatisfactory discrimination features remain the challenging issues for the widely applied electrochemical gas sensors. Quite recently, we confirmed that light-regulated electrochemical reaction significantly enhanced the electrocatalytic activity, and thereby can potentially extend the detection limit to the parts per billion (ppb) level. Nevertheless, impact of the light-regulated electrochemical reaction on response selectivity has been discussed less. Herein, we systematically report on the effect of illumination on discrimination features via design and fabrication of a light-regulated electrochemical sensor array. Upon illumination (light on), response signal to the examined gases (C 3 H 6 , NO, and CO) is selectively enhanced, resulting in the sensor array demonstrating disparate response patterns when compared with that of the sensor array operated at light off. Through processing all the response patterns derived from both light on and light off with a pattern recognition algorithm, a satisfactory discrimination feature is observed. In contrast, apparent mutual interference between NO and CO is found when the sensor array is solely operated without illumination. The impact mechanism of the illumination is studied and it is deduced that the effect of the illumination on the discriminating features can be mainly attributed to the competition of electrocatalytic activity and gas-phase reactivity. If the enhanced electrocatalytic activity (to specific gas) dominates the whole sensing progress, enhancements in the corresponding response signal would be observed upon illumination. Otherwise, illumination gives a negligible impact. Hence, the response signal to part of the examined gases is selectively enhanced by illumination. Conclusively, light-regulated electrochemical reaction would provide an efficient approach to designing future smart sensing devices.

  2. High coupling efficiency of foam spherical hohlraum driven by 2ω laser light

    Science.gov (United States)

    Chen, Yao-Hua; Lan, Ke; Zheng, Wanguo; Campbell, E. M.

    2018-02-01

    The majority of solid state laser facilities built for laser fusion research irradiate targets with third harmonic light (0.35 μm) up-converted from the fundamental Nd wavelength at 1.05 μm. The motivation for this choice of wavelength is improved laser-plasma coupling. Significant disadvantages to this choice of wavelength are the reduced damage threshold of optical components and the efficiency of energy conversion to third harmonic light. Both these issues are significantly improved if second harmonic (0.53 μm) radiation is used, but theory and experiments have shown lower optical to x-ray energy conversion efficiency and increased levels of laser-plasma instabilities, resulting in reduced laser-target coupling. In this letter, we propose to use a 0.53 μm laser for the laser ignition facilities and use a low density foam wall to increase the coupling efficiency from the laser to the capsule and present two-dimensional radiation-hydrodynamic simulations of 0.53 μm laser light irradiating an octahedral-spherical hohlraum with a low density foam wall. The simulations show that the reduced optical depth of the foam wall leads to an increased laser-light conversion into thermal x-rays and about 10% higher radiation flux on the capsule than that achieved with 0.35 μm light irradiating a solid density wall commonly used in laser indirect drive fusion research. The details of the simulations and their implications and suggestions for wavelength scaling coupled with innovative hohlraum designs will be discussed.

  3. Crop yield and light / energy efficiency in a closed ecological system: two laboratory biosphere experiments

    Science.gov (United States)

    Nelson, M.; Dempster, W. F.; Silverstone, S.; Alling, A.; Allen, J. P.; van Thillo, M.

    Two crop growth experiments in the soil-based closed ecological facity, Laboratory Biosphere, were conducted from 2003-2004 with candidate space life support crops. Apogee wheat (Utah State University variety) was grown, planted in 2 densities, 400 and 800 seeds m-2. The lighting regime for the wheat crop was 16 hours of light -- 8 hours dark at a total light intensity of around 840 mol m2 sec-1 and 48.4 mol m-2 d-1 over 84 days Average biomass was 1395 g m-2, 16.0 g m-2 day-1 and average seed production was 689 g m-2 and 7.9 g m2 day-1. The less densely planted side was more productive than the denser planting, with 1634 g m-2 and 18.8g m-2 day-1 of biomass vs. 1156 g m-2 and 13.3 g m-2 day-1; and a seed harvest of 812.3 g m-2 and 9.3 g m-2 day-1 vs. 566.5 g m-2 and 6.5 g m-2 day-1 Harvest index was 0.49 for the wheat crop. The experiment with sweet potato used TU-82-155, a compact variety developed at Tuskegee University. Light during the sweet potato experiment, on a 16 hour on/8 hours dark cycle, totalled 5568 total moles of light in 126 days for the sweet potatoes, or an average of 44.2 moles m-2 day-1. Temperature regime was 28 deg +/- 3 deg C day /22 deg +/- 4 deg C night. Sweet potato tuber yield was 39.7 kg wet weight, or an average of 7.4 kg m-2 and 7.7 kg dry weight of tubers since dry weight was about 18.6% wet weight.^Average per day production was 58.7 g m-2 day-1 wet weight and 11.3 g m-2 day-1. For the wheat, average light efficiency was 0.34 grams biomass per mole, and 0.17 grams seed per mole. The best area of wheat had an efficiency of light utilization of 0.51 g biomass per mole and 0.22 g seed per mole. For the sweet potato crop, light efficiency per tuber wet weight was 7.13 g/mole and 1.38 g dry weight of tuber per mole of light. The best area of tuber production had 9.49 g/mole wet weight and 1.85 g/mole of light dry weight. Production from the wheat was The Laboratory Biosphere experiment's light efficiency was somewhat higher than the USU

  4. Highly Efficient Perovskite-Quantum-Dot Light-Emitting Diodes by Surface Engineering

    KAUST Repository

    Pan, Jun

    2016-08-16

    A two-step ligand-exchange strategy is developed, in which the long-carbon-chain ligands on all-inorganic perovskite (CsPbX3, X = Br, Cl) quantum dots (QDs) are replaced with halide-ion-pair ligands. Green and blue light-emitting diodes made from the halide-ion-paircapped quantum dots exhibit high external quantum efficiencies compared with the untreated QDs.

  5. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    OpenAIRE

    Yuanyuan Qu; Feng Li; Hongcai Zhou; Mingwen Zhao

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculati...

  6. Controlled Defects of Zinc Oxide Nanorods for Efficient Visible Light Photocatalytic Degradation of Phenol

    Directory of Open Access Journals (Sweden)

    Jamal Al-Sabahi

    2016-03-01

    Full Text Available Environmental pollution from human and industrial activities has received much attention as it adversely affects human health and bio-diversity. In this work we report efficient visible light photocatalytic degradation of phenol using supported zinc oxide (ZnO nanorods and explore the role of surface defects in ZnO on the visible light photocatalytic activity. ZnO nanorods were synthesized on glass substrates using a microwave-assisted hydrothermal process, while the surface defect states were controlled by annealing the nanorods at various temperatures and were characterized by photoluminescence and X-ray photoelectron spectroscopy. High performance liquid chromatography (HPLC was used for the evaluation of phenol photocatalytic degradation. ZnO nanorods with high surface defects exhibited maximum visible light photocatalytic activity, showing 50% degradation of 10 ppm phenol aqueous solution within 2.5 h, with a degradation rate almost four times higher than that of nanorods with lower surface defects. The mineralization process of phenol during degradation was also investigated, and it showed the evolution of different photocatalytic byproducts, such as benzoquinone, catechol, resorcinol and carboxylic acids, at different stages. The results from this study suggest that the presence of surface defects in ZnO nanorods is crucial for its efficient visible light photocatalytic activity, which is otherwise only active in the ultraviolet region.

  7. Enhanced efficiency in single-host white organic light-emitting diode by triplet exciton conversion

    International Nuclear Information System (INIS)

    Wu, Qingyang; Zhang, Shiming; Yue, Shouzhen; Zhang, Zhensong; Xie, Guohua; Zhao, Yi; Liu, Shiyong

    2013-01-01

    The authors observe that the external quantum efficiency (EQE) of the Iridium (III) bis(4-phenylthieno [3,2-c]pyridinato-N,C 2′ )acetylacetonate (PO-01) based yellow organic light-emitting diode (OLED) is significantly increased by uniformly co-doping Iridium (III)bis[(4,6-difluorophenyl)-pyridinato-N,C 2− ] (FIrpic) and PO-01 into the same wide band-gap host of N,N ′ -dicarbazolyl-3, 5-benzene (mCP). Detailed investigation indicates that the efficiency enhancement is ascribed to effective triplet exciton gathering by FIrpic, followed by energy transfer to PO-01. Compared to the control device, which has maximum EQE of 10.5%, an improved maximum EQE of 13.2% is obtained in the optimization white device based on FIrpic and PO-01 emission according to this principle. This work makes it easier for a single host white OLED to simultaneously harvest high efficiency in both blue and yellow units. Comprehensive experimental results show that this phenomenon can also be found and utilized in other popular hosts to realize more efficient white devices. -- Highlights: • This work makes easier for a single host white OLED to harvest high efficiency in both blue and yellow units. • Efficiency enhancement is ascribed to effective triplet exciton gathering by FIrpic, followed by energy transfer to PO-01. • This phenomenon can also be found and utilized in other popular hosts to realize more efficient white devices

  8. Dark states and delocalization: Competing effects of quantum coherence on the efficiency of light harvesting systems

    Science.gov (United States)

    Hu, Zixuan; Engel, Gregory S.; Alharbi, Fahhad H.; Kais, Sabre

    2018-02-01

    Natural light harvesting systems exploit electronic coupling of identical chromophores to generate efficient and robust excitation transfer and conversion. Dark states created by strong coupling between chromophores in the antenna structure can significantly reduce radiative recombination and enhance energy conversion efficiency. Increasing the number of the chromophores increases the number of dark states and the associated enhanced energy conversion efficiency yet also delocalizes excitations away from the trapping center and reduces the energy conversion rate. Therefore, a competition between dark state protection and delocalization must be considered when designing the optimal size of a light harvesting system. In this study, we explore the two competing mechanisms in a chain-structured antenna and show that dark state protection is the dominant mechanism, with an intriguing dependence on the parity of the number of chromophores. This dependence is linked to the exciton distribution among eigenstates, which is strongly affected by the coupling strength between chromophores and the temperature. Combining these findings, we propose that increasing the coupling strength between the chromophores can significantly increase the power output of the light harvesting system.

  9. Spatial extrapolation of light use efficiency model parameters to predict gross primary production

    Directory of Open Access Journals (Sweden)

    Karsten Schulz

    2011-12-01

    Full Text Available To capture the spatial and temporal variability of the gross primary production as a key component of the global carbon cycle, the light use efficiency modeling approach in combination with remote sensing data has shown to be well suited. Typically, the model parameters, such as the maximum light use efficiency, are either set to a universal constant or to land class dependent values stored in look-up tables. In this study, we employ the machine learning technique support vector regression to explicitly relate the model parameters of a light use efficiency model calibrated at several FLUXNET sites to site-specific characteristics obtained by meteorological measurements, ecological estimations and remote sensing data. A feature selection algorithm extracts the relevant site characteristics in a cross-validation, and leads to an individual set of characteristic attributes for each parameter. With this set of attributes, the model parameters can be estimated at sites where a parameter calibration is not possible due to the absence of eddy covariance flux measurement data. This will finally allow a spatially continuous model application. The performance of the spatial extrapolation scheme is evaluated with a cross-validation approach, which shows the methodology to be well suited to recapture the variability of gross primary production across the study sites.

  10. Development of gallium-nitride-based light-emitting diodes (LEDs) and laser diodes for energy-efficient lighting and displays

    International Nuclear Information System (INIS)

    DenBaars, Steven P.; Feezell, Daniel; Kelchner, Katheryn; Pimputkar, Siddha; Pan, Chi-Chen; Yen, Chia-Chen; Tanaka, Shinichi; Zhao, Yuji; Pfaff, Nathan; Farrell, Robert; Iza, Mike; Keller, Stacia; Mishra, Umesh; Speck, James S.; Nakamura, Shuji

    2013-01-01

    Light-emitting diodes (LEDs) fabricated from gallium nitride (GaN) have led to the realization of high-efficiency white solid-state lighting. Currently, GaN white LEDs exhibit luminous efficacy greater than 150 lm W −1 , and external quantum efficiencies higher than 60%. This has enabled LEDs to compete with traditional lighting technologies, such as incandescent and compact fluorescent (CFL) lighting. Further improvements in materials quality and cost reduction are necessary for widespread adoption of LEDs for lighting. A review of the unique polarization anisotropy in GaN is included for the different crystal orientations. The emphasis on nonpolar and semipolar LEDs highlights high-power violet and blue emitters, and we consider the effects of indium incorporation and well width. Semipolar GaN materials have enabled the development of high-efficiency LEDs in the blue region and recent achievements of green laser diodes at 520 nm

  11. Light extraction efficiency enhancement of GaN-based light emitting diodes by a ZnO current spreading layer

    Science.gov (United States)

    Hua, Yang; Xiaofeng, Wang; Jun, Ruan; Zhicong, Li; Xiaoyan, Yi; Yao, Duan; Yiping, Zeng; Guohong, Wang

    2009-09-01

    Gallium nitride (GaN) based light emitting diodes (LEDs) with a thick and high quality ZnO film as a current spreading layer grown by metal-source vapor phase epitaxy (MVPE) are fabricated successfully. Compared with GaN-based LEDs employing a Ni/Au or an indium tin oxide transparent current spreading layer, these LEDs show an enhancement of the external quantum efficiency of 93% and 35% at a forward current of 20 mA, respectively. The full width at half maximum of the ZnO (002) ω-scan rocking curve is 93 arcsec, which corresponds to a high crystal quality of the ZnO film. Optical microscopy and atomic force microscopy are used to observe the surface morphology of the ZnO film, and many regular hexagonal features are found. A spectrophotometer is used to study the different absorption properties between the ZnO film and the indium tin oxide film of the GaN LED. The mechanisms of the extraction quantum efficiency increase and the series resistance change of the GaN-based LEDs with ZnO transparent current spreading layers are analyzed.

  12. Highly Efficient Orange and Red Phosphorescent Organic Light-Emitting Diodes with Low Roll-Off of Efficiency using a Novel Thermally Activated Delayed Fluorescence Material as Host.

    Science.gov (United States)

    Wang, Hui; Meng, Lingqiang; Shen, Xingxing; Wei, Xiaofang; Zheng, Xiuli; Lv, Xiaopeng; Yi, Yuanping; Wang, Ying; Wang, Pengfei

    2015-07-15

    MTXSFCz with thermally activated delayed fluorescence is synthesized. Orange and red phosphorescent organic light-emitting diodes (PHOLEDs) with low efficiency roll-off exhibit external quantum efficiencies (EQE) up to 11.8% and 15.6%. The efficient upconversion from triplet to singlet of the host reduces the triplet density and thus affords a low efficiency roll-off of PHOLEDs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. High-Efficiency Nitride-Based Solid-State Lighting. Final Technical Progress Report

    International Nuclear Information System (INIS)

    Paul T. Fini; Shuji Nakamura

    2005-01-01

    In this final technical progress report we summarize research accomplished during Department of Energy contract DE-FC26-01NT41203, entitled ''High-Efficiency Nitride-Based Solid-State Lighting''. Two teams, from the University of California at Santa Barbara (Principle Investigator: Dr. Shuji Nakamura) and the Lighting Research Center at Rensselaer Polytechnic Institute (led by Dr. N. Narendran), pursued the goals of this contract from thin film growth, characterization, and packaging/luminaire design standpoints. The UCSB team initially pursued the development of blue gallium nitride (GaN)-based vertical-cavity surface-emitting lasers, as well as ultraviolet GaN-based light emitting diodes (LEDs). In Year 2, the emphasis shifted to resonant-cavity light emitting diodes, also known as micro-cavity LEDs when extremely thin device cavities are fabricated. These devices have very directional emission and higher light extraction efficiency than conventional LEDs. Via the optimization of thin-film growth and refinement of device processing, we decreased the total cavity thickness to less than 1 (micro)m, such that micro-cavity effects were clearly observed and a light extraction efficiency of over 10% was reached. We also began the development of photonic crystals for increased light extraction, in particular for so-called ''guided modes'' which would otherwise propagate laterally in the device and be re-absorbed. Finally, we pursued the growth of smooth, high-quality nonpolar a-plane and m-plane GaN films, as well as blue light emitting diodes on these novel films. Initial nonpolar LEDs showed the expected behavior of negligible peak wavelength shift with increasing drive current. M-plane LEDs in particular show promise, as unpackaged devices had unsaturated optical output power of ∼ 3 mW at 200 mA drive current. The LRC's tasks were aimed at developing the subcomponents necessary for packaging UCSB's light emitting diodes, and packaging them to produce a white light

  14. Phosphorescent cyclometalated complexes for efficient blue organic light-emitting diodes.

    Science.gov (United States)

    Suzuri, Yoshiyuki; Oshiyama, Tomohiro; Ito, Hiroto; Hiyama, Kunihisa; Kita, Hiroshi

    2014-10-01

    Phosphorescent emitters are extremely important for efficient organic light-emitting diodes (OLEDs), which attract significant attention. Phosphorescent emitters, which have a high phosphorescence quantum yield at room temperature, typically contain a heavy metal such as iridium and have been reported to emit blue, green and red light. In particular, the blue cyclometalated complexes with high efficiency and high stability are being developed. In this review, we focus on blue cyclometalated complexes. Recent progress of computational analysis necessary to design a cyclometalated complex is introduced. The prediction of the radiative transition is indispensable to get an emissive cyclometalated complex. We summarize four methods to control phosphorescence peak of the cyclometalated complex: (i) substituent effect on ligands, (ii) effects of ancillary ligands on heteroleptic complexes, (iii) design of the ligand skeleton, and (iv) selection of the central metal. It is considered that novel ligand skeletons would be important to achieve both a high efficiency and long lifetime in the blue OLEDs. Moreover, the combination of an emitter and a host is important as well as the emitter itself. According to the dependences on the combination of an emitter and a host, the control of exciton density of the triplet is necessary to achieve both a high efficiency and a long lifetime, because the annihilations of the triplet state cause exciton quenching and material deterioration.

  15. Structurally Deformed MoS2 for Electrochemically Stable, Thermally Resistant, and Highly Efficient Hydrogen Evolution Reaction.

    Science.gov (United States)

    Chen, Yen-Chang; Lu, Ang-Yu; Lu, Ping; Yang, Xiulin; Jiang, Chang-Ming; Mariano, Marina; Kaehr, Bryan; Lin, Oliver; Taylor, André; Sharp, Ian D; Li, Lain-Jong; Chou, Stanley S; Tung, Vincent

    2017-11-01

    The emerging molybdenum disulfide (MoS 2 ) offers intriguing possibilities for realizing a transformative new catalyst for driving the hydrogen evolution reaction (HER). However, the trade-off between catalytic activity and long-term stability represents a formidable challenge and has not been extensively addressed. This study reports that metastable and temperature-sensitive chemically exfoliated MoS 2 (ce-MoS 2 ) can be made into electrochemically stable (5000 cycles), and thermally robust (300 °C) while maintaining synthetic scalability and excellent catalytic activity through physical-transformation into 3D structurally deformed nanostructures. The dimensional transition enabled by a high throughput electrohydrodynamic process provides highly accessible, and electrochemically active surface area and facilitates efficient transport across various interfaces. Meanwhile, the hierarchically strained morphology is found to improve electronic coupling between active sites and current collecting substrates without the need for selective engineering the electronically heterogeneous interfaces. Specifically, the synergistic combination of high strain load stemmed from capillarity-induced-self-crumpling and sulfur (S) vacancies intrinsic to chemical exfoliation enables simultaneous modulation of active site density and intrinsic HER activity regardless of continuous operation or elevated temperature. These results provide new insights into how catalytic activity, electrochemical-, and thermal stability can be concurrently enhanced through the physical transformation that is reminiscent of nature, in which properties of biological materials emerge from evolved dimensional transitions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Structurally Deformed MoS2 for Electrochemically Stable, Thermally Resistant, and Highly Efficient Hydrogen Evolution Reaction

    KAUST Repository

    Chen, Yen-Chang

    2017-10-12

    The emerging molybdenum disulfide (MoS2) offers intriguing possibilities for realizing a transformative new catalyst for driving the hydrogen evolution reaction (HER). However, the trade-off between catalytic activity and long-term stability represents a formidable challenge and has not been extensively addressed. This study reports that metastable and temperature-sensitive chemically exfoliated MoS2 (ce-MoS2) can be made into electrochemically stable (5000 cycles), and thermally robust (300 °C) while maintaining synthetic scalability and excellent catalytic activity through physical-transformation into 3D structurally deformed nanostructures. The dimensional transition enabled by a high throughput electrohydrodynamic process provides highly accessible, and electrochemically active surface area and facilitates efficient transport across various interfaces. Meanwhile, the hierarchically strained morphology is found to improve electronic coupling between active sites and current collecting substrates without the need for selective engineering the electronically heterogeneous interfaces. Specifically, the synergistic combination of high strain load stemmed from capillarity-induced-self-crumpling and sulfur (S) vacancies intrinsic to chemical exfoliation enables simultaneous modulation of active site density and intrinsic HER activity regardless of continuous operation or elevated temperature. These results provide new insights into how catalytic activity, electrochemical-, and thermal stability can be concurrently enhanced through the physical transformation that is reminiscent of nature, in which properties of biological materials emerge from evolved dimensional transitions.

  17. Highly efficient tandem organic light-emitting devices employing an easily fabricated charge generation unit

    Science.gov (United States)

    Yang, Huishan; Yu, Yaoyao; Wu, Lishuang; Qu, Biao; Lin, Wenyan; Yu, Ye; Wu, Zhijun; Xie, Wenfa

    2018-02-01

    We have realized highly efficient tandem organic light-emitting devices (OLEDs) employing an easily fabricated charge generation unit (CGU) combining 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile with ultrathin bilayers of CsN3 and Al. The charge generation and separation processes of the CGU have been demonstrated by studying the differences in the current density–voltage characteristics of external-carrier-excluding devices. At high luminances of 1000 and 10000 cd/m2, the current efficiencies of the phosphorescent tandem device are about 2.2- and 2.3-fold those of the corresponding single-unit device, respectively. Simultaneously, an efficient tandem white OLED exhibiting high color stability and warm white emission has also been fabricated.

  18. Efficient light-emitting devices based on platinum-complexes-anchored polyhedral oligomeric silsesquioxane materials

    KAUST Repository

    Yang, Xiaohui

    2010-08-24

    The synthesis, photophysical, and electrochemical characterization of macromolecules, consisting of an emissive platinum complex and carbazole moieties covalently attached to a polyhedral oligomeric silsesquioxane (POSS) core, is reported. Organic light-emitting devices based on these POSS materials exhibit a peak external quantum efficiency of ca. 8%, which is significantly higher than that of the analogous devices with a physical blend of the platinum complexes and a polymer matrix, and they represent noticeable improvement in the device efficiency of solution-processable phosphorescent excimer devices. Furthermore, the ratio of monomer and excimer/aggregate electroluminescent emission intensity, as well as the device efficiency, increases as the platinum complex moiety presence on the POSS macromolecules decreases. © 2010 American Chemical Society.

  19. Applying FBD-power theory to analysing effective lighting devices’ impact on power quality and electric grid efficiency

    Directory of Open Access Journals (Sweden)

    Andrés Pavas

    2011-06-01

    Full Text Available Currently the impact of high efficient lighting devices such as compact fluorescent lamps (CFL and light emitting diodes (LED is an important concern for the electrotechnical community. This paper makes a contribution towards determining the impact of these devices on electric grid power quality and efficiency, proposed by means of applying FBD-power theory to the currents absorbed by CFLs and LEDs. An analysis of the waveform distortion regarding IEEE standard 519 and efficiency detriment quantification are presented.

  20. Metal oxide core shell nanostructures as building blocks for efficient light emission (SISGR)

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Jane P [Univ. of California, Los Angeles, CA (United States); Dorman, James [Univ. of California, Los Angeles, CA (United States); Cheung, Cyrus [Univ. of California, Los Angeles, CA (United States)

    2016-01-12

    The objective of this research is to synthesize core-shell nano-structured metal oxide materials and investigate their structural, electronic and optical properties to understand the microscopic pathways governing the energy conversion process, thereby controlling and improving their efficiency. Specifically, the goal is to use a single metal oxide core-shell nanostructure and a single excitation source to generate photons with long emission lifetime over the entire visible spectrum and when controlled at the right ratio, generating white light. In order to achieve this goal, we need to control the energy transfer between light emitting elements, which dictates the control of their interatomic spacing and spatial distribution. We developed an economical wet chemical process to form the nanostructured core and to control the thickness and composition of the shell layers. With the help from using DOE funded synchrotron radiation facility, we delineated the growth mechanism of the nano-structured core and the shell layers, thereby enhancing our understanding of structure-property relation in these materials. Using the upconversion luminescence and the lifetime measurements as effective feedback to materials sysnthes is and integration, we demonstrated improved luminescence lifetimes of the core-shell nano-structures and quantified the optimal core-multi-shell structure with optimum shell thickness and composition. We developed a rare-earths co-doped LaPO4 core-multishell structure in order to produce a single white light source. It was decided that the mutli-shell method would produce the largest increase in luminescence efficiency while limiting any energy transfer that may occur between the dopant ions. All samples resulted in emission spectra within the accepted range of white light generation based on the converted CIE color coordinates. The white light obtained varied between warm and cool white depending on the layering architecture, allowing for the

  1. Synergetic electrode architecture for efficient graphene-based flexible organic light-emitting diodes.

    Science.gov (United States)

    Lee, Jaeho; Han, Tae-Hee; Park, Min-Ho; Jung, Dae Yool; Seo, Jeongmin; Seo, Hong-Kyu; Cho, Hyunsu; Kim, Eunhye; Chung, Jin; Choi, Sung-Yool; Kim, Taek-Soo; Lee, Tae-Woo; Yoo, Seunghyup

    2016-06-02

    Graphene-based organic light-emitting diodes (OLEDs) have recently emerged as a key element essential in next-generation displays and lighting, mainly due to their promise for highly flexible light sources. However, their efficiency has been, at best, similar to that of conventional, indium tin oxide-based counterparts. We here propose an ideal electrode structure based on a synergetic interplay of high-index TiO2 layers and low-index hole-injection layers sandwiching graphene electrodes, which results in an ideal situation where enhancement by cavity resonance is maximized yet loss to surface plasmon polariton is mitigated. The proposed approach leads to OLEDs exhibiting ultrahigh external quantum efficiency of 40.8 and 62.1% (64.7 and 103% with a half-ball lens) for single- and multi-junction devices, respectively. The OLEDs made on plastics with those electrodes are repeatedly bendable at a radius of 2.3 mm, partly due to the TiO2 layers withstanding flexural strain up to 4% via crack-deflection toughening.

  2. Study on Suitable Light Conditions and Efficient Lipid Extraction Technologies for Biodiesel Production Based on Microalgae

    Science.gov (United States)

    Wang, Yao; Zhang, Qingtao; Sun, Yuan; Yang, Chengjia

    2018-01-01

    As a new generation biodiesel feedstock, microalgae have most potential to replace fossil fuel. However, the limited scale and high cost are two bottleneck problems. Efficient microwave-assisted lipid extraction technologies and suitable light conditions for Chlorella Sorokiniana need further study for lowering the cost. In this study, three photoperiod groups(24L:0D, 12L:12D, 0L:24D), three illumination intensity groups (1800 lux, 3600 lux, 5400 lux)and four light spectrum groups (Red, green, blue, and white) were used to culture Chlorella Sorokiniana to investigate those effects on algae growth rate and biomass accumulation. The suitable microwave treatment was also studied to achieve an optimizing quantum fracturing technology. 400 w, 750 w and 1000 w microwave power were set and 60 °C, 75 °C, 90 °C microwave conditions were investigated. The results showed that Chlorella Sorokiniana under 24L:0D photoperiod with 5400 lux white light can achieve better growth rate. The 90 °C / 1000w microwave treatment was identified as the most simple, easy, and effective way for lipid extraction from Chlorella Sorokiniana. As the raw material of biodiesel production, C18:1, C18:2 and C18:3 have accounted for important components of fatty acid in Chlorella Sorokiniana. Therefore, Chlorella Sorokiniana is a good raw material for the production of good quality biodiesel under suitable and efficient technologies.

  3. Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

    KAUST Repository

    Lin, Ronghui

    2018-04-21

    A nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

  4. Curing efficiency of dual-cure resin cement under zirconia with two different light curing units.

    Science.gov (United States)

    Gultekin, Pınar; Pak Tunc, Elif; Ongul, Deger; Turp, Volkan; Bultan, Ozgur; Karataslı, Burcin

    2015-01-01

    Adequate polymerization is a crucial factor in obtaining optimal physical properties and a satisfying clinical performance from composite resin materials. The aim of this study was to evaluate the polymerization efficiency of dual-cure resin cement cured with two different light curing units under zirconia structures having differing thicknesses. 4 zirconia discs framework in 4 mm diameter and in 0.5 mm, 1 mm and 1.5 mm thickness were prepared using computer-aided design system. One of the 0.5 mm-thick substructures was left as mono-layered whereas others were layered with feldspathic porcelain of same thickness and ceramic samples with 4 different thicknesses (0.5, 1, 1.5 and 2.0 mm) were prepared. For each group (n=12) resin cement was light cured in polytetrafluoroethylene molds using Light Emitting Diode (LED) or Quartz-Tungsten Halogen (QHT) light curing units under each of 4 zirconia based discs (n=96). The values of depth of cure (in mm) and the Vickers Hardness Number values (VHN) were evaluated for each specimen. The use of LED curing unit produced a greater depth of cure compared to QTH under ceramic discs with 0.5 and 1 mm thickness (punit produced significantly greater VHN values compared to the QTH unit (pLight curing may not result in adequate resin cement polymerization under thick zirconia structures. LED light sources should be preferred over QTH for curing dual-cure resin cements, especially for those under thicker zirconia restorations.

  5. CURING EFFICIENCY OF DUAL-CURE RESIN CEMENT UNDER ZIRCONIA WITH TWO DIFFERENT LIGHT CURING UNITS

    Directory of Open Access Journals (Sweden)

    Pınar GÜLTEKİN

    2015-04-01

    Full Text Available Purpose: Adequate polymerization is a crucial factor in obtaining optimal physical properties and a satisfying clinical performance from composite resin materials. The aim of this study was to evaluate the polymerization efficiency of dual-cure resin cement cured with two different light curing units under zirconia structures having differing thicknesses. Materials and Methods: 4 zirconia discs framework in 4 mm diameter and in 0.5 mm, 1 mm and 1.5 mm thickness were prepared using computer-aided design system. One of the 0.5 mm-thick substructures was left as mono-layered whereas others were layered with feldspathic porcelain of same thickness and ceramic samples with 4 different thicknesses (0.5, 1, 1.5 and 2.0 mm were prepared. For each group (n=12 resin cement was light cured in polytetrafluoroethylene molds using Light Emitting Diode (LED or Quartz-Tungsten Halogen (QHT light curing units under each of 4 zirconia based discs (n=96. The values of depth of cure (in mm and the Vickers Hardness Number values (VHN were evaluated for each specimen. Results: The use of LED curing unit produced a greater depth of cure compared to QTH under ceramic discs with 0.5 and 1 mm thickness (p<0.05.At 100μm and 300 μm depth, the LED unit produced significantly greater VHN values compared to the QTH unit (p<0.05. At 500 μm depth, the difference between the VHN values of LED and QTH groups were not statistically significant. Conclusion: Light curing may not result in adequate resin cement polymerization under thick zirconia structures. LED light sources should be preferred over QTH for curing dual-cure resin cements, especially for those under thicker zirconia restorations.

  6. Exergy efficiency of light conversion into biomass in the macroalga Ulva sp. (Chlorophyta) cultivated under the pulsed light in a photobioreactor.

    Science.gov (United States)

    Habiby, Oz; Nahor, Omri; Israel, Alvaro; Liberzon, Alexander; Golberg, Alexander

    2018-03-14

    Marine macroalgae are a potential feedstock for biorefineries that can reduce dependence on fossil fuels and contribute to bioeconomy. New knowledge and technologies for efficient conversion of solar energy into macroalgae biomass are needed to increase biomass yields and energy conversion efficiency. In this work, we show that the green macroalgae from Ulva sp. can grow under the pulsed light in a photobioreactor with higher exergy conversion efficiency in comparison to cultivation under constant light with the same intensity. In the tested frequencies, 1-40 Hz and duty cycles (DC) 1-100%, DC has a stronger impact on the growth rate than frequency. The efficiency of light transformation into biomass increased with decreasing DC. Pulsating with DC 20% led to 60% of the biomass chemical energy yield for the respective constant light (DC 100%). Models of Ulva sp. growth rate and exergy conversion efficiency as a function of pulsating light parameters were developed. These results open new directions to enhance solar to chemical energy conversion through macroalgae by controlling the light distribution in the macroalgal biomass. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  7. An empirical study on energy efficiency improvement through photovoltaic systems and a LED lighting control system

    Science.gov (United States)

    Choi, Young Kwan; Lee, Jae Hyeong

    2015-09-01

    In this research, a facility was constructed and its performance was analyzed to improve the energy efficiency of a vertical-type water treatment building. After the design and construction of a fixed tilt Photovoltaic in Building (PVIB) on the rooftop using a crystalline silicon solar cell module and photovoltaic generator integrated with the building by using a Building Integrated Photovoltaic System (BIPV), a thin-film module on the rooftop and outer wall of water treatment building, and the generation efficiency was analyzed. Also, a DC distribution was established for use of a brushless DC (BLDC) pump motor, and the existing lighting-facility-based manual on-off method was turned into a system for energy conservation by controlling light emitting diode (LED) through a wireless motion sensor and dimming control. In addition, a Building Energy Management System (BEMS) for a real-time analysis of the energy efficiency for a vertical0type water treatment building was prepared and tested. The vertical-type water treatment building developed in this study is currently operating the BEMS. The vertical-type water treatment building reported in this paper is expected to reduce energy consumption by about 30% compared to existing water treatment systems.

  8. Characterization of a high efficiency optical memory for the storage of quantum light states

    Science.gov (United States)

    Kupchak, Connor; Thomas, Ryan; Lvovsky, Alex

    2012-06-01

    We have developed a coherent optical storage device based on a Gradient Echo Memory scheme showing efficiencies of above 65%. The memory is realized in a warm vapor of ^87Rb atoms utilizing a λ-type energy level scheme. We use a co-propagating, co-rotating circular polarized pump beam coupled with pulsed coherent states to create an off-resonant Raman absorption line suitable for storage. Through sufficient filtration of the strong pump field, the stored light pulse is retrieved after a desired time and subjected to time-domain homodyne tomography. By repeating this sequence on an ensemble of 50 000 identical coherent states we gain enough information to completely reconstruct the quantum state of light retrieved from the memory. Furthermore, by repeating this characterization for a set of coherent states with at sufficient range of amplitudes we can completely characterize the memory process itself. This is possible by implementing a method devised by our group called coherent state Quantum Process Tomography which also has the capability to predict how well the memory will perform on any arbitrary quantum input state. We show our current storage efficiencies and what needs to be further done to demonstrate a true high efficiency, quantum optical memory.

  9. Stable luminescent metal-organic frameworks as dual-functional materials to encapsulate ln(3+) ions for white-light emission and to detect nitroaromatic explosives.

    Science.gov (United States)

    Xie, Wei; Zhang, Shu-Ran; Du, Dong-Ying; Qin, Jun-Sheng; Bao, Shao-Juan; Li, Jing; Su, Zhong-Min; He, Wen-Wen; Fu, Qiang; Lan, Ya-Qian

    2015-04-06

    A stable porous carbazole-based luminescent metal-organic framework, NENU-522, was successfully constructed. It is extremely stable in air and acidic/basic aqueous solutions, which provides the strategy for luminescent material encapsulation of Ln(3+) ions with tunable luminescence for application in light emission. More importantly, Ln(3+)@NENU-522 can emit white light by encapsulating different molar ratios of Eu(3+) and Tb(3+) ions. Additionally, Tb(3+)@NENU-522 is found to be useful as a fluorescent indicator for the qualitative and quantitative detection of nitroaromatic explosives with different numbers of -NO2 groups, and the concentrations of complete quenching are about 2000, 1000, and 80 ppm for nitrobenzene, 1,3-dinitrobenzene, and 2,4,6-trinitrophenol, respectively. Meanwhile, Tb(3+)@NENU-522 displays high selectivity and recyclability in the detection of nitroaromatic explosives.

  10. Innovative Development of Next Generation and Energy Efficient Solid State Light Sources for General Illumination

    Energy Technology Data Exchange (ETDEWEB)

    Ian Ferguson

    2006-07-31

    This two year program resulted in a novel broadband spectrally dynamic solid state illumination source (BSDLED) that uses a dual wavelength light emitting diode (LED) and combinations of phosphors to create a broadband emission that is real-time controllable. Four major focuses of this work were as follows: (1) creation of a two terminal dual wavelength LED with control of the relative intensities of the two emission peaks, (2) bandgap modeling of the two terminal dual LED to explain operation based on the doping profile, (3) novel use of phosphor combinations with dual LEDs to create a broadband spectral power distribution that can be varied to mimic a blackbody radiator over a certain range and (4) investigation of novel doping schemes to create tunnel junctions or equivalent buried current spreading layers in the III-nitrides. Advances were achieved in each of these four areas which could lead to more efficient solid state light sources with greater functionality over existing devices. The two-terminal BSDLED is an important innovation for the solid-state lighting industry as a variable spectrum source. A three-terminal dual emitter was also investigated and appears to be the most viable approach for future spectrally dynamic solid state lighting sources. However, at this time reabsorption of emission between the two active regions limits the usefulness of this device for illumination applications.

  11. Improved electron injection and transport by use of baking soda as a low-cost, air-stable, n-dopant for solution-processed phosphorescent organic light-emitting diodes

    Science.gov (United States)

    Earmme, Taeshik; Jenekhe, Samson A.

    2013-06-01

    Sodium bicarbonate (baking soda, NaHCO3) is found to be an efficient low-cost, air-stable, and environmentally friendly n-dopant for electron-transport layer (ETL) in solution-processed phosphorescent organic light-emitting diodes (PhOLEDs). A 2.0-fold enhancement in power efficiency of blue PhOLEDs is observed by use of NaHCO3-doped 4,7-diphenyl-1,10-phenanthroline (BPhen) ETL. The bulk conductivity of NaHCO3-doped BPhen film is increased by 5 orders of magnitude. Enhanced performance of PhOLEDs is similarly observed by use of NaHCO3-doped 1,3,5-tris(m-pyrid-3-yl-phenyl)benzene ETL. These results demonstrate that sodium bicarbonate is an effective n-dopant in organic electronics.

  12. Exciplex-Forming Cohost for High Efficiency and High Stability Phosphorescent Organic Light-Emitting Diodes.

    Science.gov (United States)

    Shih, Chun-Jen; Lee, Chih-Chien; Chen, Ying-Hao; Biring, Sajal; Kumar, Gautham; Yeh, Tzu-Hung; Sen, Somaditya; Liu, Shun-Wei; Wong, Ken-Tsung

    2018-01-17

    An exciplex forming cohost system is employed to achieve a highly efficient organic light-emitting diode (OLED) with good electroluminescent lifetime. The exciplex is formed at the interfacial contact of a conventional star-shaped carbazole hole-transporting material, 4,4',4″-tris(N-carbazolyl)-triphenylamine (TCTA), and a triazine electron-transporting material, 2,4,6-tris[3-(1H-pyrazol-1-yl)phenyl]-1,3,5-triazine (3P-T2T). The excellent combination of TCTA and 3P-T2T is applied as the cohost of a common green phosphorescent emitter with almost zero energy loss. When Ir(ppy) 2 (acac) is dispersed in such exciplex cohost system, OLED device with maximum external quantum efficiency of 29.6%, the ultrahigh power efficiency of 147.3 lm/W, and current efficiency of 107 cd/A were successfully achieved. More importantly, the OLED device showed a low-efficiency roll-off and an operational lifetime (τ 80 ) of ∼1020 min with the initial brightness of 2000 cd/m 2 , which is 56 times longer than the reference device. The significant difference of device stability was attributed to the degradation of exciplex system for energy transfer process, which was investigated by the photoluminescence aging measurement at room temperature and 100 K, respectively.

  13. Efficiency Control in Iridium Complex-Based Phosphorescent Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Boucar Diouf

    2012-01-01

    Full Text Available Key factors to control the efficiency in iridium doped red and green phosphorescent light emitting diodes (PhOLEDs are discussed in this review: exciton confinement, charge trapping, dopant concentration and dopant molecular structure. They are not independent from each other but we attempt to present each of them in a situation where its specific effects are predominant. A good efficiency in PhOLEDs requires the triplet energy of host molecules to be sufficiently high to confine the triplet excitons within the emitting layer (EML. Furthermore, triplet excitons must be retained within the EML and should not drift into the nonradiative levels of the electron or hole transport layer (resp., ETL or HTL; this is achieved by carefully choosing the EML’s adjacent layers. We prove how reducing charge trapping results in higher efficiency in PhOLEDs. We show that there is an ideal concentration for a maximum efficiency of PhOLEDs. Finally, we present the effects of molecular structure on the efficiency of PhOLEDs using red iridium complex dopant with different modifications on the ligand to tune its highest occupied molecular orbital (HOMO and lowest unoccupied molecular orbital (LUMO energies.

  14. Cost and energy-efficient (LED, induction and plasma) roadway lighting.

    Science.gov (United States)

    2013-11-01

    There is an increasing interest in using new lighting technologies such as light emitting diode (LED), Induction, and Plasma light sources : in roadway lighting. The most commonly claimed benefits of the new lighting systems include increased reliabi...

  15. Model Predictive Vibration Control Efficient Constrained MPC Vibration Control for Lightly Damped Mechanical Structures

    CERN Document Server

    Takács, Gergely

    2012-01-01

    Real-time model predictive controller (MPC) implementation in active vibration control (AVC) is often rendered difficult by fast sampling speeds and extensive actuator-deformation asymmetry. If the control of lightly damped mechanical structures is assumed, the region of attraction containing the set of allowable initial conditions requires a large prediction horizon, making the already computationally demanding on-line process even more complex. Model Predictive Vibration Control provides insight into the predictive control of lightly damped vibrating structures by exploring computationally efficient algorithms which are capable of low frequency vibration control with guaranteed stability and constraint feasibility. In addition to a theoretical primer on active vibration damping and model predictive control, Model Predictive Vibration Control provides a guide through the necessary steps in understanding the founding ideas of predictive control applied in AVC such as: ·         the implementation of ...

  16. Increased light-use efficiency in northern terrestrial ecosystems indicated by CO 2 and greening observations: INCREASE IN NH LIGHT USE EFFICIENCY

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Rebecca T. [Science and Solutions for a Changing Planet DTP, Imperial College London, London UK; AXA Chair Programme in Biosphere and Climate Impacts, Department of Life Sciences, Imperial College London, London UK; Department of Physics, Imperial College London, London UK; Prentice, Iain Colin [AXA Chair Programme in Biosphere and Climate Impacts, Department of Life Sciences, Imperial College London, London UK; Grantham Institute: Climate Change and the Environment, Imperial College London, London UK; Graven, Heather [Department of Physics, Imperial College London, London UK; Grantham Institute: Climate Change and the Environment, Imperial College London, London UK; Ciais, Philippe [Laboratoire des Sciences du Climat et de l' Environnement, Saint-Aubin France; Fisher, Joshua B. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena California USA; Hayes, Daniel J. [School of Forest Resources, University of Maine, Orono Maine USA; Huang, Maoyi [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Huntzinger, Deborah N. [School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff Arizona USA; Ito, Akihiko [Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba Japan; Jain, Atul [Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, Urbana Illinois USA; Mao, Jiafu [Climate Change Science Institute and Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge Tennessee USA; Michalak, Anna M. [Department of Global Ecology, Carnegie Institution for Science, Stanford California USA; Peng, Shushi [Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing China; Poulter, Benjamin [Department of Ecology, Montana State University, Bozeman Montana USA; Ricciuto, Daniel M. [Climate Change Science Institute and Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge Tennessee USA; Shi, Xiaoying [Climate Change Science Institute and Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge Tennessee USA; Schwalm, Christopher [Woods Hole Research Center, Falmouth Massachusetts USA; Tian, Hanqin [International Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, Auburn Alabama USA; Zeng, Ning [Department of Atmospheric and Oceanic Science and Earth System Science Interdisciplinary Center, University of Maryland, College Park Maryland USA

    2016-11-04

    Observations show an increasing amplitude in the seasonal cycle of CO2 (ASC) north of 45°N of 56 ± 9.8% over the last 50 years and an increase in vegetation greenness of 7.5–15% in high northern latitudes since the 1980s. However, the causes of these changes remain uncertain. Historical simulations from terrestrial biosphere models in the Multiscale Synthesis and Terrestrial Model Intercomparison Project are compared to the ASC and greenness observations, using the TM3 atmospheric transport model to translate surface fluxes into CO2 concentrations. We find that the modeled change in ASC is too small but the mean greening trend is generally captured. Modeled increases in greenness are primarily driven by warming, whereas ASC changes are primarily driven by increasing CO2. We suggest that increases in ecosystem-scale light use efficiency (LUE) have contributed to the observed ASC increase but are underestimated by current models. We highlight potential mechanisms that could increase modeled LUE.

  17. ZnO PN Junctions for Highly-Efficient, Low-Cost Light Emitting Diodes

    International Nuclear Information System (INIS)

    David P. Norton; Stephen Pearton; Fan Ren

    2007-01-01

    By 2015, the US Department of Energy has set as a goal the development of advanced solid state lighting technologies that are more energy efficient, longer lasting, and more cost-effective than current technology. One approach that is most attractive is to utilize light-emitting diode technologies. Although III-V compound semiconductors have been the primary focus in pursuing this objective, ZnO-based materials present some distinct advantages that could yield success in meeting this objective. As with the nitrides, ZnO is a direct bandgap semiconductor whose gap energy (3.2 eV) can be tuned from 3.0 to 4 eV with substitution of Mg for higher bandgap, Cd for lower bandgap. ZnO has an exciton binding energy of 60 meV, which is larger than that for the nitrides, indicating that it should be a superior light emitting semiconductor. Furthermore, ZnO thin films can be deposited at temperatures on the order of 400-600 C, which is significantly lower than that for the nitrides and should lead to lower manufacturing costs. It has also been demonstrated that functional ZnO electronic devices can be fabricated on inexpensive substrates, such as glass. Therefore, for the large-area photonic application of solid state lighting, ZnO holds unique potential. A significant impediment to exploiting ZnO in light-emitting applications has been the absence of effective p-type carrier doping. However, the recent realization of acceptor-doped ZnO material overcomes this impediment, opening the door to ZnO light emitting diode development In this project, the synthesis and properties of ZnO-based pn junctions for light emitting diodes was investigated. The focus was on three issues most pertinent to realizing a ZnO-based solid state lighting technology, namely (1) achieving high p-type carrier concentrations in epitaxial and polycrystalline films, (2) realizing band edge emission from pn homojunctions, and (3) investigating pn heterojunction constructs that should yield efficient light

  18. MPWide: a light-weight library for efficient message passing over wide area networks

    Directory of Open Access Journals (Sweden)

    Derek Groen

    2013-12-01

    Full Text Available We present MPWide, a light weight communication library which allows efficient message passing over a distributed network. MPWide has been designed to connect application running on distributed (supercomputing resources, and to maximize the communication performance on wide area networks for those without administrative privileges. It can be used to provide message-passing between application, move files, and make very fast connections in client-server environments. MPWide has already been applied to enable distributed cosmological simulations across up to four supercomputers on two continents, and to couple two different bloodflow simulations to form a multiscale simulation.

  19. New Light-Harvesting Materials Using Accurate and Efficient Bandgap Calculations

    DEFF Research Database (Denmark)

    Castelli, Ivano Eligio; Hüser, Falco; Pandey, Mohnish

    2014-01-01

    of materials for different applications where the bandgaps are used as descriptors for the efficiency of a photoelectrochemical device. Here, new light harvesting materials are proposed to be used in a one-photon photoelectrochemical device for water splitting by combining the estimation of the bandgaps...... with the stability analysis using Pourbaix diagrams and with the evaluation of the position of the band edges. Using this methodology, 25 candidate materials are obtained and 5 of them appear to have a realistic possibility of being used as photocatalyst in a one-photon water splitting device. © 2014 WILEY...

  20. In silico evaluation of highly efficient organic light-emitting materials

    Science.gov (United States)

    Kwak, H. Shaun; Giesen, David J.; Hughes, Thomas F.; Goldberg, Alexander; Cao, Yixiang; Gavartin, Jacob; Dixon, Steve; Halls, Mathew D.

    2016-09-01

    Design and development of highly efficient organic and organometallic dopants is one of the central challenges in the organic light-emitting diodes (OLEDs) technology. Recent advances in the computational materials science have made it possible to apply computer-aided evaluation and screening framework directly to the design space of organic lightemitting diodes (OLEDs). In this work, we will showcase two major components of the latest in silico framework for development of organometallic phosphorescent dopants - (1) rapid screening of dopants by machine-learned quantum mechanical models and (2) phosphorescence lifetime predictions with spin-orbit coupled calculations (SOC-TDDFT). The combined work of virtual screening and evaluation would significantly widen the design space for highly efficient phosphorescent dopants with unbiased measures to evaluate performance of the materials from first principles.

  1. Phosphorescent dye-based supramolecules for high-efficiency organic light-emitting diodes.

    Science.gov (United States)

    Kim, Kwon-Hyeon; Lee, Sunghun; Moon, Chang-Ki; Kim, Sei-Yong; Park, Young-Seo; Lee, Jeong-Hwan; Woo Lee, Jin; Huh, June; You, Youngmin; Kim, Jang-Joo

    2014-09-10

    Organic light-emitting diodes (OLEDs) are among the most promising organic semiconductor devices. The recently reported external quantum efficiencies (EQEs) of 29-30% for green and blue phosphorescent OLEDs are considered to be near the limit for isotropically oriented iridium complexes. The preferred orientation of transition dipole moments has not been thoroughly considered for phosphorescent OLEDs because of the lack of an apparent driving force for a molecular arrangement in all but a few cases, even though horizontally oriented transition dipoles can result in efficiencies of over 30%. Here we use quantum chemical calculations to show that the preferred orientation of the transition dipole moments of heteroleptic iridium complexes (HICs) in OLEDs originates from the preferred direction of the HIC triplet transition dipole moments and the strong supramolecular arrangement within the co-host environment. We also demonstrate an unprecedentedly high EQE of 35.6% when using HICs with phosphorescent transition dipole moments oriented in the horizontal direction.

  2. Highly Efficient Photocatalytic H2 Evolution from Water using Visible Light and Structure-Controlled Graphitic Carbon Nitride**

    Science.gov (United States)

    Martin, David James; Qiu, Kaipei; Shevlin, Stephen Andrew; Handoko, Albertus Denny; Chen, Xiaowei; Guo, Zhengxiao; Tang, Junwang

    2014-01-01

    The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low-cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported. The g-C3N4 exhibits an extraordinary hydrogen-evolution rate (ca. 20 000 μmol h−1 g−1 under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5 % under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced. PMID:25045013

  3. Highly efficient photocatalytic H₂ evolution from water using visible light and structure-controlled graphitic carbon nitride.

    Science.gov (United States)

    Martin, David James; Qiu, Kaipei; Shevlin, Stephen Andrew; Handoko, Albertus Denny; Chen, Xiaowei; Guo, Zhengxiao; Tang, Junwang

    2014-08-25

    The major challenge of photocatalytic water splitting, the prototypical reaction for the direct production of hydrogen by using solar energy, is to develop low-cost yet highly efficient and stable semiconductor photocatalysts. Herein, an effective strategy for synthesizing extremely active graphitic carbon nitride (g-C3N4) from a low-cost precursor, urea, is reported. The g-C3N4 exhibits an extraordinary hydrogen-evolution rate (ca. 20,000 μmol h(-1) g(-1) under full arc), which leads to a high turnover number (TON) of over 641 after 6 h. The reaction proceeds for more than 30 h without activity loss and results in an internal quantum yield of 26.5% under visible light, which is nearly an order of magnitude higher than that observed for any other existing g-C3N4 photocatalysts. Furthermore, it was found by experimental analysis and DFT calculations that as the degree of polymerization increases and the proton concentration decreases, the hydrogen-evolution rate is significantly enhanced. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  4. Analysis of Minimum Efficiency Performance Standards for Residential General Service Lighting in Chile

    Energy Technology Data Exchange (ETDEWEB)

    Letschert, Virginie E.; McNeil, Michael A.; Leiva Ibanez, Francisco Humberto; Ruiz, Ana Maria; Pavon, Mariana; Hall, Stephen

    2011-06-01

    Minimum Efficiency Performance Standards (MEPS) have been chosen as part of Chile's national energy efficiency action plan. As a first MEPS, the Ministry of Energy has decided to focus on a regulation for lighting that would ban the sale of inefficient bulbs, effectively phasing out the use of incandescent lamps. Following major economies such as the US (EISA, 2007) , the EU (Ecodesign, 2009) and Australia (AS/NZS, 2008) who planned a phase out based on minimum efficacy requirements, the Ministry of Energy has undertaken the impact analysis of a MEPS on the residential lighting sector. Fundacion Chile (FC) and Lawrence Berkeley National Laboratory (LBNL) collaborated with the Ministry of Energy and the National Energy Efficiency Program (Programa Pais de Eficiencia Energetica, or PPEE) in order to produce a techno-economic analysis of this future policy measure. LBNL has developed for CLASP (CLASP, 2007) a spreadsheet tool called the Policy Analysis Modeling System (PAMS) that allows for evaluation of costs and benefits at the consumer level but also a wide range of impacts at the national level, such as energy savings, net present value of savings, greenhouse gas (CO2) emission reductions and avoided capacity generation due to a specific policy. Because historically Chile has followed European schemes in energy efficiency programs (test procedures, labelling program definitions), we take the Ecodesign commission regulation No 244/2009 as a starting point when defining our phase out program, which means a tiered phase out based on minimum efficacy per lumen category. The following data were collected in order to perform the techno-economic analysis: (1) Retail prices, efficiency and wattage category in the current market, (2) Usage data (hours of lamp use per day), and (3) Stock data, penetration of efficient lamps in the market. Using these data, PAMS calculates the costs and benefits of efficiency standards from two distinct but related perspectives: (1) The

  5. Simplified efficient phosphorescent organic light-emitting diodes by organic vapor phase deposition

    Science.gov (United States)

    Pfeiffer, P.; Beckmann, C.; Stümmler, D.; Sanders, S.; Simkus, G.; Heuken, M.; Vescan, A.; Kalisch, H.

    2017-12-01

    The most efficient phosphorescent organic light-emitting diodes (OLEDs) are comprised of complex stacks with numerous organic layers. State-of-the-art phosphorescent OLEDs make use of blocking layers to confine charge carriers and excitons. On the other hand, simplified OLEDs consisting of only three organic materials have shown unexpectedly high efficiency when first introduced. This was attributed to superior energy level matching and suppressed external quantum efficiency (EQE) roll-off. In this work, we study simplified OLED stacks, manufactured by organic vapor phase deposition, with a focus on charge balance, turn-on voltage (Von), and efficiency. To prevent electrons from leaking through the device, we implemented a compositionally graded emission layer. By grading the emitter with the hole transport material, charge confinement is enabled without additional blocking layers. Our best performing organic stack is composed of only three organic materials in two layers including the emitter Ir(ppy)3 and yields a Von of 2.5 V (>1 cd/m2) and an EQE of 13% at 3000 cd/m2 without the use of any additional light extraction techniques. Changes in the charge balance, due to barrier tuning or adjustments in the grading parameters and layer thicknesses, are clearly visible in the current density-voltage-luminance (J-V-L) measurements. As charge injection at the electrodes and organic interfaces is of great interest but difficult to investigate in complex device structures, we believe that our simplified organic stack is not only a potent alternative to complex state-of-the-art OLEDs but also a well suited test vehicle for experimental studies focusing on the modification of the electrode-organic semiconductor interface.

  6. A brighter future? Quantifying the rebound effect in energy efficient lighting

    International Nuclear Information System (INIS)

    Schleich, Joachim; Mills, Bradford; Dütschke, Elisabeth

    2014-01-01

    This paper quantifies the direct rebound effects associated with the switch from incandescent lamps (ILs) or halogen bulbs to more energy efficient compact fluorescent lamps (CFLs) or light emitting diodes (LEDs) using a large nationally representative survey of German households. The direct rebound effect is measured as the elasticity of energy demand for lighting with respect to changes in energy efficient lamps. In particular, the rebound effect is decomposed into changes in lamp luminosity and burn time. For the average bulb, the associated total direct rebound effect is estimated at about 6%. The larger part (around 60%) of this rebound effect results from increases in bulb luminosity. For the most frequent (modal) bulb switch, i.e. the replacement of the main bulb in the living or dining room, the total direct rebound effect is just below 3%, with around 60% attributable to an increase in burn time. Average and modal bulb differences suggest that the magnitude of the rebound effect may decrease with intensity of initial bulb use. The magnitude of the direct rebound and the relative contributions of changes in luminosity and burn time also differ by initial bulb type and by replacement bulb type. - Highlights: • A rebound of 6% is estimated for the average switch to an energy efficient bulb. • A rebound of ca. 3% is estimated for the main bulb in the living or dining room. • Higher luminosity makes up 60% (40%) of the rebound for the average (modal) bulb. • The magnitude of the rebound differs by initial bulb and replacement bulb type. • A third of the switches to energy efficient bulbs entail negative rebound effects

  7. A new bismuth-based coordination polymer as an efficient visible light responding photocatalyst under white LED irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ya-Jing; Zheng, Yue-Qing, E-mail: zhengyueqing@nbu.edu.cn; Wang, Jin-Jian; Zhou, Lin-Xia

    2017-02-15

    A new bismuth-based polymer, [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O (H{sub 2}pydc=pyridine-2,5-dicarboxylic acid, bpe=trans-bis(4-pyridyl) ethylene) has been hydrothermally synthesized. Transient photocurrent response and electrochemical impedance spectroscopy studies indicate that the synthesized polymer with efficient charge separation and transportation can be used as a potential photocatalyst. So we use it for the degradation of rhodamine B (RhB) dye wastewater under visible light. The comparative study on commercial Bi{sub 2}O{sub 3} shows [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O has the higher photocatalytic performance, with the degradation rate of 97% and 2% within 100 min for [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O and commercial Bi{sub 2}O{sub 3} respectively. Additionally, the five cycle reproducibility results of [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O implies that it can be used as a stable photocatalyst. - Graphical abstract: We report a new 1D coordination polymer [Hbpe][Bi(Hpydc){sub 2}(pydc)]·H{sub 2}O by a facile hydrothermal method. The Bi-CP shows good photoelectric property and photocatalytic activity for RhB degradation under visible white LED lamp irradiation. And the stability of the visible-light-responsive bismuth-based coordination polymer has also been examined. - Highlights: • A new Bi(III) coordination polymer is hydrothermally synthesized. • The Bi-CP shows good photoelectric and photocatalytic properties. • Bi-CP shows higher activity than the commercial Bi{sub 2}O{sub 3} for RhB degradation.

  8. Smart LED allocation scheme for efficient multiuser visible light communication networks.

    Science.gov (United States)

    Sewaiwar, Atul; Tiwari, Samrat Vikramaditya; Chung, Yeon Ho

    2015-05-18

    In a multiuser bidirectional visible light communication (VLC), a large number of LEDs or an LED array needs to be allocated in an efficient manner to ensure sustainable data rate and link quality. Moreover, in order to support an increasing or decreasing number of users in the network, the LED allocation is required to be performed dynamically. In this paper, a novel smart LED allocation scheme for efficient multiuser VLC networks is presented. The proposed scheme allocates RGB LEDs to multiple users in a dynamic and efficient fashion, while satisfying illumination requirements in an indoor environment. The smart LED array comprised of RGB LEDs is divided into sectors according to the location of the users. The allocated sectors then provide optical power concentration toward the users for efficient and reliable data transmission. An algorithm for the dynamic allocation of the LEDs is also presented. To verify its effective resource allocation feature of the proposed scheme, simulations were performed. It is found that the proposed smart LED allocation scheme provides the effect of optical beamforming toward individual users, thereby increasing the collective power concentration of the optical signals on the desirable users and resulting in significantly increased data rate, while ensuring sufficient illumination in a multiuser VLC environment.

  9. 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.

  10. Novel concepts for high-efficiency white organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Gregor

    2007-07-01

    This work deals with novel concepts to realize high efficiency white OLEDs by combining fluorescent blue and phosphorescent green and orange emitters. A key point determining the maximum efficiency possible, as well as the device structure to be chosen to reach high efficiency, is the triplet exciton energy of the fluorescent blue emitter. If its triplet state is lower than that of the phosphorescent emitters, mutual exciton quenching can occur. This problem is solved by the first concept with spatial separation of the fluorescent blue from the phosphorescent emitters by a large-gap exciton blocking layer. To still realize exciton generation on both sides, the interlayer has to be ambipolar. On the other hand, if the triplet exciton energy of the fluorescent blue is higher than that of at least one of the phosphorescent emitters, appropriate arrangement of the emission layers makes a separation layer obsolete, since phosphorescence quenching does not occur anymore. Moreover, the intrinsically non-radiative triplet excitons of the fluorescent blue emitter may be harvested by the phosphor for light emission, which means that even 100% internal quantum efficiency is possible. The last chapter 6 deals with this second concept, where the main issue is to simultaneously achieve exciton harvesting as complete as possible and a balanced white emission spectrum by appropriately distributing singlet and triplet excitons to the used emitters. All emitters used in this work are commercially available and their molecular structure is disclosed in order to make the results transparent. (orig.)

  11. Efficient non-doped phosphorescent orange, blue and white organic light-emitting devices.

    Science.gov (United States)

    Yin, Yongming; Yu, Jing; Cao, Hongtao; Zhang, Letian; Sun, Haizhu; Xie, Wenfa

    2014-10-24

    Efficient phosphorescent orange, blue and white organic light-emitting devices (OLEDs) with non-doped emissive layers were successfully fabricated. Conventional blue phosphorescent emitters bis [4,6-di-fluorophenyl]-pyridinato-N,C(2')] picolinate (Firpic) and Bis(2,4-difluorophenylpyridinato) (Fir6) were adopted to fabricate non-doped blue OLEDs, which exhibited maximum current efficiency of 7.6 and 4.6 cd/A for Firpic and Fir6 based devices, respectively. Non-doped orange OLED was fabricated utilizing the newly reported phosphorescent material iridium (III) (pbi)₂Ir(biq), of which manifested maximum current and power efficiency of 8.2 cd/A and 7.8 lm/W. The non-doped white OLEDs were achieved by simply combining Firpic or Fir6 with a 2-nm (pbi)₂Ir(biq). The maximum current and power efficiency of the Firpic and (pbi)₂Ir(biq) based white OLED were 14.8 cd/A and 17.9 lm/W.

  12. Efficient light emitting diodes by photon recycling and their application in pixelless infrared imaging devices

    Science.gov (United States)

    Dupont, E.; Chiu, S.

    2000-02-01

    The success of the pixelless imaging concept using a quantum well infrared photodetector integrated with a light emitting diode (QWIP-LED) depends critically on the extent of spatial lateral spreading of both photocurrent generated in the QWIP and near infrared (NIR) photons emitted by the LED as they escape from the device layers. According to the photon recycling model proposed by Schnitzer et al. [Appl. Phys. Lett. 62, 131 (1993)] there appears to be a trade-off between a high LED external quantum efficiency and a small photon lateral spread, the former being a necessary condition for achieving high detector sensitivity. This lateral spreading due to multireflections and reincarnations of the NIR photons could potentially degrade the image quality or resolution of the device. By adapting Schnitzer's model to the QWIP-LED structure, we have identified device parameters that could potentially influence the NIR photon lateral spread and the LED external efficiency. In addition, we have developed a simple sequential model to estimate the crosstalk between the incoming far infrared image and the up-converted NIR image. We have found that the thickness of the LED is an important parameter that needs to be optimized in order to maximize the external efficiency and to minimize the crosstalk. A 6000-Å-thick LED active layer should give a resolution of ˜30 μm and an external efficiency of ˜10%.

  13. Highly efficient red phosphorescent organic light-emitting diodes based on solution processed emissive layer

    International Nuclear Information System (INIS)

    Liu, Baiquan; Xu, Miao; Tao, Hong; Ying, Lei; Zou, Jianhua; Wu, Hongbin; Peng, Junbiao

    2013-01-01

    Highly efficient red phosphorescent organic polymer light-emitting diodes (PhOLEDs) were fabricated based on a solution-processed small-molecule host 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) by doping an iridium complex, tris(1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine)iridium (III) (Ir(MPCPPZ) 3 ). A hole blocking layer 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBI) with a function of electron transport was thermally deposited onto the top of CBP layer. The diode with the structure of ITO/PEDOT:PSS (50 nm)/CBP:Ir(MPCPPZ) 3 (55 nm)/TPBI (30 nm)/Ba (4 nm)/Al (120 nm) showed an external quantum efficiency (QE ext ) of 19.3% and luminous efficiency (LE) of 18.3 cd/A at a current density of 0.16 mA/cm 2 , and Commission International de I'Eclairage (CIE) coordinates of (0.607, 0.375). It was suggested that the diodes using TPBI layer exhibited nearly 100% internal quantum efficiency and one order magnitude enhanced LE or QE ext efficiencies. -- Highlights: • Efficient red PhOLEDs based on a solution-processed small-molecule host were fabricated. • By altering volume ratio of chloroform/chlorobenzene solvent, we got best film quality of CBP. • EQE of the diode was 19.3%, indicating nearly 100% internal quantum yield was achieved

  14. Highly efficient red phosphorescent organic light-emitting diodes based on solution processed emissive layer

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Baiquan; Xu, Miao; Tao, Hong; Ying, Lei [Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640 (China); State Key Laboratory of Luminescent Materials and Devices, Guangzhou 510640 (China); Zou, Jianhua, E-mail: zou1007@gmail.com [Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640 (China); State Key Laboratory of Luminescent Materials and Devices, Guangzhou 510640 (China); Wu, Hongbin; Peng, Junbiao [Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou 510640 (China); State Key Laboratory of Luminescent Materials and Devices, Guangzhou 510640 (China)

    2013-10-15

    Highly efficient red phosphorescent organic polymer light-emitting diodes (PhOLEDs) were fabricated based on a solution-processed small-molecule host 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) by doping an iridium complex, tris(1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine)iridium (III) (Ir(MPCPPZ){sub 3}). A hole blocking layer 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBI) with a function of electron transport was thermally deposited onto the top of CBP layer. The diode with the structure of ITO/PEDOT:PSS (50 nm)/CBP:Ir(MPCPPZ){sub 3} (55 nm)/TPBI (30 nm)/Ba (4 nm)/Al (120 nm) showed an external quantum efficiency (QE{sub ext}) of 19.3% and luminous efficiency (LE) of 18.3 cd/A at a current density of 0.16 mA/cm{sup 2}, and Commission International de I'Eclairage (CIE) coordinates of (0.607, 0.375). It was suggested that the diodes using TPBI layer exhibited nearly 100% internal quantum efficiency and one order magnitude enhanced LE or QE{sub ext} efficiencies. -- Highlights: • Efficient red PhOLEDs based on a solution-processed small-molecule host were fabricated. • By altering volume ratio of chloroform/chlorobenzene solvent, we got best film quality of CBP. • EQE of the diode was 19.3%, indicating nearly 100% internal quantum yield was achieved.

  15. Enhancement of near-UV GaN LED light extraction efficiency by GaN/sapphire template patterning

    International Nuclear Information System (INIS)

    Ali, M; Svensk, O; Riuttanen, L; Suihkonen, S; Törmä, P T; Sopanen, M; Lipsanen, H; Kruse, M; Romanov, A E; Odnoblyudov, M A; Bougrov, V E

    2012-01-01

    We present near-UV GaN light-emitting diodes (LEDs) grown on patterned GaN/sapphire templates with improved material quality and light extraction efficiency. Enhancement of light extraction efficiency is attributed to voids generated at the GaN/sapphire interface. The sidewall inclination angle of the voids can be controlled from nearly vertical (∼ 85°) to fully inclined (∼ 60°) by changing the initial patterning dimensions. Light extraction efficiency and material quality improve with a decreasing void sidewall angle. A 20% increase in the light output is observed at 20 mA of input current for LED structures with ∼60° inclined sidewall voids. (fast track communication)

  16. Microdischarge Array Flexible Light Source for High-Efficiency Irradiation of Spaced-Based Crops, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — It is desirable to develop a high-efficiency lighting source for large-area irradiation of space-based crops. The key requirements for such a system include high...

  17. Reducing Barriers To The Use of High-Efficiency Lighting Systems

    Energy Technology Data Exchange (ETDEWEB)

    Peter Morante

    2005-12-31

    With funding from the U.S. Department of Energy (DOE), the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute completed the four-year research project, Reducing Barriers to the Use of High-Efficiency Lighting Systems. The initial objectives were: (1) identifying barriers to widespread penetration of lighting controls in commercial/industrial (C/I) applications that employ fluorescent lamp technologies, and (2) making recommendations to overcome these barriers. The addition of a fourth year expanded the original project objectives to include an examination of the impact on fluorescent lamps from dimming utilizing different lamp electrode heating and dimming ratios. The scope of the project was narrowed to identify barriers to the penetration of lighting controls into commercial-industrial (C/I) applications that employ fluorescent lamp technologies, and to recommend means for overcoming these barriers. Working with lighting manufacturers, specifiers, and installers, the project identified technological and marketing barriers to the widespread use of lighting controls, specifically automatic-off controls, occupancy sensors, photosensors, dimming systems, communication protocols and load-shedding ballasts. The primary barriers identified include cost effectiveness of lighting controls to the building owner, lack of standard communication protocols to allow different part of the control system to communicate effectively, and installation and commissioning issues. Overcoming the identified barriers requires lighting control products on the market to achieve three main goals: (1) Achieve sufficient functionality to meet the key requirements of their main market. (2) Allow significant cost reduction compared to current market standard systems. Cost should consider: hardware capital cost including wiring, design time required by the specifier and the control system manufacturer, installation time required by the electrician, and commissioning time and

  18. Fast Postmoisture Treatment of Luminescent Perovskite Films for Efficient Light-Emitting Diodes.

    Science.gov (United States)

    Wang, Haoran; Li, Xiaomin; Yuan, Mingjian; Yang, Xuyong

    2018-02-23

    Despite the recent advances in the performance of perovskite light-emitting diodes (PeLEDs), the effects of water on the perovskite emissive layer and its electroluminescence are still unclear, even though it has been previously demonstrated that moisture has a significant impact on the quality of perovskite films in the fabrication process of perovskite solar cells and is a prerequisite for obtaining high-performance PeLEDs. Here, the effects of postmoisture on the luminescent CH 3 NH 3 PbBr 3 (MAPbBr 3 ) perovskite films are systematically investigated. It is found that postmoisture treatment can efficiently control the morphology and growth of perovskite films and only a fast moisture exposure at a 60% high relative humidity results in significantly improved crystallinity, carrier lifetime, and photoluminescence quantum yield of perovskite films. With the optimized moisture-treated perovskite films, a high-performance PeLED is fabricated, exhibiting a maximum current efficiency of 20.4 cd A -1 , which is an almost 20-fold enhancement when compared with perovskite films without moisture treatment. The results provide valuable insights into the moisture-assisted growth of luminescent perovskite films and will aid in the development of high-performance perovskite light-emitting devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Highly efficient photocatalytic hydrogen evolution of graphene/YInO3 nanocomposites under visible light irradiation.

    Science.gov (United States)

    Ding, Jianjun; Yan, Wenhao; Xie, Wei; Sun, Song; Bao, Jun; Gao, Chen

    2014-02-21

    Visible-light-driven hydrogen evolution with high efficiency is important in the current photocatalysis research. Here we report for the first time the design and synthesis of a new graphene-semiconductor nanocomposite consisting of YInO3 nanoparticles and two-dimensional graphene sheets as efficient photocatalysts for hydrogen evolution under visible light irradiation. The graphene/YInO3 nanocomposites were synthesized using a facile solvothermal method in which the formation of graphene and the deposition of YInO3 nanoparticles on the graphene sheets can be achieved simultaneously. The addition of graphene as a cocatalyst can narrow the band gap of YInO3 to visible photon energy and prolong the separation and lifetime of electron-hole pairs by the chemical bonding between YInO3 and graphene. The photocatalytic reaction with this nanocomposite reaches a high H2 evolution rate of 400.4 μmol h(-1) g(-1) when the content of graphene is 0.5 wt%, over 127 and 3.7 times higher than that of pure YInO3 and Pt/YInO3, respectively. This work can provide an effective approach to the fabrication of graphene-based photocatalysts with high performance in the field of energy conversion.

  20. Intrinsic climate dependency of ecosystem light and water-use-efficiencies across Australian biomes

    International Nuclear Information System (INIS)

    Shi, Hao; Li, Longhui; Eamus, Derek; Cleverly, James; Huete, Alfredo; Yu, Qiang; Beringer, Jason; Van Gorsel, Eva; Hutley, Lindsay

    2014-01-01

    The sensitivity of ecosystem gross primary production (GPP) to availability of water and photosynthetically active radiation (PAR) differs among biomes. Here we investigated variations of ecosystem light-use-efficiency (eLUE: GPP/PAR) and water-use-efficiency (eWUE: GPP/evapotranspiration) among seven Australian eddy covariance sites with differing annual precipitation, species composition and temperature. Changes to both eLUE and eWUE were primarily correlated with atmospheric vapor pressure deficit (VPD) at multiple temporal scales across biomes, with minor additional correlations observed with soil moisture and temperature. The effects of leaf area index on eLUE and eWUE were also relatively weak compared to VPD, indicating an intrinsic dependency of eLUE and eWUE on climate. Additionally, eLUE and eWUE were statistically different for biomes between summer and winter, except eWUE for savannas and the grassland. These findings will improve our understanding of how light- and water-use traits in Australian ecosystems may respond to climate change. (letter)

  1. Energy resolution and efficiency of phonon-mediated kinetic inductance detectors for light detection

    Energy Technology Data Exchange (ETDEWEB)

    Cardani, L., E-mail: laura.cardani@roma1.infn.it [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); Physics Department, Princeton University, Washington Road, 08544, Princeton, New Jersey (United States); Colantoni, I.; Coppolecchia, A. [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); Cruciani, A.; Vignati, M.; Bellini, F.; Casali, N.; Cosmelli, C. [Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); INFN - Sezione di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy); Di Domizio, S. [Dipartimento di Fisica, Università degli Studi di Genova, Via Dodecaneso 33, 16146 Genova (Italy); INFN - Sezione di Genova, Via Dodecaneso 33, 16146 Genova (Italy); Castellano, M. G. [Istituto di Fotonica e Nanotecnologie - CNR, Via Cineto Romano 42, 00156 Roma (Italy); Tomei, C. [INFN - Sezione di Roma, Piazzale Aldo Moro 2, 00185 Roma (Italy)

    2015-08-31

    The development of sensitive cryogenic light detectors is of primary interest for bolometric experiments searching for rare events like dark matter interactions or neutrino-less double beta decay. Thanks to their good energy resolution and the natural multiplexed read-out, Kinetic Inductance Detectors (KIDs) are particularly suitable for this purpose. To efficiently couple KIDs-based light detectors to the large crystals used by the most advanced bolometric detectors, active surfaces of several cm{sup 2} are needed. For this reason, we are developing phonon-mediated detectors. In this paper, we present the results obtained with a prototype consisting of four 40 nm thick aluminum resonators patterned on a 2 × 2 cm{sup 2} silicon chip, and calibrated with optical pulses and X-rays. The detector features a noise resolution σ{sub E} = 154 ± 7 eV and an (18 ± 2)% efficiency.

  2. Nanopatterned aluminum nitride template for high efficiency light-emitting diodes.

    Science.gov (United States)

    Kim, Sang-Mook; Park, Tae-Young; Park, Seong-Ju; Lee, Seung-Jae; Baek, Jong Hyeob; Park, Yun Chang; Jung, Gun Young

    2009-08-17

    Nanopatterned aluminum nitride (NP-AlN) templates were used to enhance the light extraction efficiency of the light-emitting diodes (LEDs). Here, the NP-AlN interlayer between the sapphire substrate and GaN-based LED was used as an effective light outcoupling layer at the direction of bottom side and as a buffer layer for growth of GaN LEDs. The cross-sectional transmission electron microscopy (TEM) analysis showed that the formation of stacking faults and voids could help reduce the threading dislocations. Micro Raman spectra also revealed that the GaN-based epilayer grown on the NP-AlN template had smaller residual stress than that grown on a planar sapphire substrate. The normalized electroluminescence (EL) spectra at the top and bottom sides of device revealed that the enhancement of the bottom side emission of the LED with the NP-AlN interlayer was more notable than a planar sapphire substrate due to the graded-refractive-index (GRIN) effect of the NP-AlN. (c) 2009 Optical Society of America

  3. Vitamin K5 is an efficient photosensitizer for ultraviolet A light inactivation of bacteria.

    Science.gov (United States)

    Xu, Fei; Li, Ying; Ahmad, Justen; Wang, Yonggang; Scott, Dorothy E; Vostal, Jaroslav G

    2018-02-01

    Photodynamic treatment combining light and a photosensitizer molecule can be an effective method to inactivate pathogenic bacteria. This study identified vitamin K5 as an efficient photosensitizer for ultraviolet light A (UVA)-induced bacterial inactivation. Six bacterial species, Bacillus cereus (vegetative form), Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella pneumoniae, and two species of antibiotic-resistant bacteria, Pseudomonas aeruginosa* and Staphylococcus aureus*, were suspended in aqueous solutions with or without vitamin K5 and exposed to UVA irradiation. UVA irradiation (5.8 J cm-2) with vitamin K5 (1600 μmol l-1) reduced the colony forming units (CFU) of these bacteria by three to seven logs. Antibiotic resistant bacteria were also susceptible to the bactericidal effects of UVA and vitamin K5 combination treatment. Inactivation of bacteria in human plasma required higher doses of UVA light and vitamin K5. UVA irradiation (30 J cm-2) with vitamin K5 (2000 μmol l-1) reduced E. coli and S. aureus spiked into human plasma by seven logs CFU/ml. Reactive oxygen species, such as superoxide anion radicals and hydroxyl radicals, were found to be generated in vitamin K5 aqueous solution after UVA irradiation, suggesting these oxygen species may mediate the inactivation of the bacteria. Published by Oxford University Press on behalf of FEMS 2018.

  4. Increasing the efficiency of silicon heterojunction solar cells and modules by light soaking

    KAUST Repository

    Kobayashi, Eiji

    2017-06-24

    Silicon heterojunction solar cells use crystalline silicon (c-Si) wafers as optical absorbers and employ bilayers of doped/intrinsic hydrogenated amorphous silicon (a-Si:H) to form passivating contacts. Recently, we demonstrated that such solar cells increase their operating voltages and thus their conversion efficiencies during light exposure. We found that this performance increase is due to improved passivation of the a-Si:H/c-Si interface and is induced by injected charge carriers (either by light soaking or forward-voltage biasing of the device). Here, we discuss this counterintuitive behavior and establish that: (i) the performance increase is observed in solar cells as well as modules; (ii) this phenomenon requires the presence of doped a-Si:H films, but is independent from whether light is incident from the a-Si:H(p) or the a-Si:H(n) side; (iii) UV and blue photons do not play a role in this effect; (iv) the performance increase can be observed under illumination intensities as low as 20Wm (0.02-sun) and appears to be almost identical in strength when under 1-sun (1000Wm); (v) the underlying physical mechanism likely differs from annealing-induced surface passivation.

  5. Understanding moisture stress on light use efficiency across terrestrial ecosystems based on global flux and remote-sensing data

    Science.gov (United States)

    Yulong Zhang; Conghe Song; Ge Sun; Lawrence E. Band; Asko Noormets; Quanfa Zhang

    2015-01-01

    Light use efficiency (LUE) is a key biophysical parameter characterizing the ability of plants to convert absorbed light to carbohydrate. However, the environmental regulations on LUE, especially moisture stress, are poorly understood, leading to large uncertainties in primary productivity estimated by LUE models. The objective of this study is to investigate the...

  6. Stable and efficient retrospective 4D-MRI using non-uniformly distributed quasi-random numbers

    Science.gov (United States)

    Breuer, Kathrin; Meyer, Cord B.; Breuer, Felix A.; Richter, Anne; Exner, Florian; Weng, Andreas M.; Ströhle, Serge; Polat, Bülent; Jakob, Peter M.; Sauer, Otto A.; Flentje, Michael; Weick, Stefan

    2018-04-01

    The purpose of this work is the development of a robust and reliable three-dimensional (3D) Cartesian imaging technique for fast and flexible retrospective 4D abdominal MRI during free breathing. To this end, a non-uniform quasi random (NU-QR) reordering of the phase encoding (k y –k z ) lines was incorporated into 3D Cartesian acquisition. The proposed sampling scheme allocates more phase encoding points near the k-space origin while reducing the sampling density in the outer part of the k-space. Respiratory self-gating in combination with SPIRiT-reconstruction is used for the reconstruction of abdominal data sets in different respiratory phases (4D-MRI). Six volunteers and three patients were examined at 1.5 T during free breathing. Additionally, data sets with conventional two-dimensional (2D) linear and 2D quasi random phase encoding order were acquired for the volunteers for comparison. A quantitative evaluation of image quality versus scan times (from 70 s to 626 s) for the given sampling schemes was obtained by calculating the normalized mutual information (NMI) for all volunteers. Motion estimation was accomplished by calculating the maximum derivative of a signal intensity profile of a transition (e.g. tumor or diaphragm). The 2D non-uniform quasi-random distribution of phase encoding lines in Cartesian 3D MRI yields more efficient undersampling patterns for parallel imaging compared to conventional uniform quasi-random and linear sampling. Median NMI values of NU-QR sampling are the highest for all scan times. Therefore, within the same scan time 4D imaging could be performed with improved image quality. The proposed method allows for the reconstruction of motion artifact reduced 4D data sets with isotropic spatial resolution of 2.1  ×  2.1  ×  2.1 mm3 in a short scan time, e.g. 10 respiratory phases in only 3 min. Cranio-caudal tumor displacements between 23 and 46 mm could be observed. NU-QR sampling enables for stable 4D

  7. Efficient propagation of TM polarized light in photonic crystal components exhibiting band gaps for TE polarized light

    DEFF Research Database (Denmark)

    Borel, Peter Ingo; Frandsen, Lars Hagedorn; Thorhauge, Morten

    2003-01-01

    D finite-difference-time-domain method. The simulated spectra are in excellent agreement with the experimental results, which show a propagation loss as low as 2.5±4 dB/mm around 1525 nm and bend losses at 2.9±0.2 dB for TM polarized light. We demonstrate a high coupling for TM polarized light......We have investigated the properties of TM polarized light in planar photonic crystal waveguide structures, which exhibit photonic band gaps for TE polarized light. Straight and bent photonic crystal waveguides and couplers have been fabricated in silicon-on-insulator material and modelled using a 3...

  8. Efficient, Hysteresis-Free, and Stable Perovskite Solar Cells with ZnO as Electron-Transport Layer: Effect of Surface Passivation.

    Science.gov (United States)

    Cao, Jing; Wu, Binghui; Chen, Ruihao; Wu, Youyunqi; Hui, Yong; Mao, Bing-Wei; Zheng, Nanfeng

    2018-01-19

    The power conversion efficiency of perovskite solar cells (PSCs) has ascended from 3.8% to 22.1% in recent years. ZnO has been well-documented as an excellent electron-transport material. However, the poor chemical compatibility between ZnO and organo-metal halide perovskite makes it highly challenging to obtain highly efficient and stable PSCs using ZnO as the electron-transport layer. It is demonstrated in this work that the surface passivation of ZnO by a thin layer of MgO and protonated ethanolamine (EA) readily makes ZnO as a very promising electron-transporting material for creating hysteresis-free, efficient, and stable PSCs. Systematic studies in this work reveal several important roles of the modification: (i) MgO inhibits the interfacial charge recombination, and thus enhances cell performance and stability; (ii) the protonated EA promotes the effective electron transport from perovskite to ZnO, further fully eliminating PSCs hysteresis; (iii) the modification makes ZnO compatible with perovskite, nicely resolving the instability of ZnO/perovskite interface. With all these findings, PSCs with the best efficiency up to 21.1% and no hysteresis are successfully fabricated. PSCs stable in air for more than 300 h are achieved when graphene is used to further encapsulate the cells. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Low Efficiency Upconversion Nanoparticles for High-Resolution Coalignment of Near-Infrared and Visible Light Paths on a Light Microscope.

    Science.gov (United States)

    Sundaramoorthy, Sriramkumar; Garcia Badaracco, Adrian; Hirsch, Sophia M; Park, Jun Hong; Davies, Tim; Dumont, Julien; Shirasu-Hiza, Mimi; Kummel, Andrew C; Canman, Julie C

    2017-03-08

    The combination of near-infrared (NIR) and visible wavelengths in light microscopy for biological studies is increasingly common. For example, many fields of biology are developing the use of NIR for optogenetics, in which an NIR laser induces a change in gene expression and/or protein function. One major technical barrier in working with both NIR and visible light on an optical microscope is obtaining their precise coalignment at the imaging plane position. Photon upconverting particles (UCPs) can bridge this gap as they are excited by NIR light but emit in the visible range via an anti-Stokes luminescence mechanism. Here, two different UCPs have been identified, high-efficiency micro 540 -UCPs and lower efficiency nano 545 -UCPs, that respond to NIR light and emit visible light with high photostability even at very high NIR power densities (>25 000 Suns). Both of these UCPs can be rapidly and reversibly excited by visible and NIR light and emit light at visible wavelengths detectable with standard emission settings used for Green Fluorescent Protein (GFP), a commonly used genetically encoded fluorophore. However, the high efficiency micro 540 -UCPs were suboptimal for NIR and visible light coalignment, due to their larger size and spatial broadening from particle-to-particle energy transfer consistent with a long-lived excited state and saturated power dependence. In contrast, the lower efficiency nano-UCPs were superior for precise coalignment of the NIR beam with the visible light path (∼2 μm versus ∼8 μm beam broadening, respectively) consistent with limited particle-to-particle energy transfer, superlinear power dependence for emission, and much smaller particle size. Furthermore, the nano-UCPs were superior to a traditional two-camera method for NIR and visible light path alignment in an in vivo Infrared-Laser-Evoked Gene Operator (IR-LEGO) optogenetics assay in the budding yeast Saccharomyces cerevisiae. In summary, nano-UCPs are powerful new tools

  10. Low efficiency upconversion nanoparticles for high-resolution coalignment of near-infrared and visible light paths on a light microscope

    Science.gov (United States)

    Sundaramoorthy, Sriramkumar; Badaracco, Adrian Garcia; Hirsch, Sophia M.; Park, Jun Hong; Davies, Tim; Dumont, Julien; Shirasu-Hiza, Mimi; Kummel, Andrew C.; Canman, Julie C.

    2017-01-01

    The combination of near infrared (NIR) and visible wavelengths in light microscopy for biological studies is increasingly common. For example, many fields of biology are developing the use of NIR for optogenetics, in which an NIR laser induces a change in gene expression and/or protein function. One major technical barrier in working with both NIR and visible light on an optical microscope is obtaining their precise coalignment at the imaging plane position. Photon upconverting particles (UCPs) can bridge this gap as they are excited by NIR light but emit in the visible range via an anti-Stokes luminescence mechanism. Here, two different UCPs have been identified, high-efficiency micro540-UCPs and lower efficiency nano545-UCPs, that respond to NIR light and emit visible light with high photostability even at very high NIR power densities (>25,000 Suns). Both of these UCPs can be rapidly and reversibly excited by visible and NIR light and emit light at visible wavelengths detectable with standard emission settings used for Green Fluorescent Protein (GFP), a commonly used genetically-encoded fluorophore. However, the high efficiency micro540-UCPs were suboptimal for NIR and visible light coalignment, due to their larger size and spatial broadening from particle-to-particle energy transfer consistent with a long lived excited state and saturated power dependence. In contrast, the lower efficiency nano-UCPs were superior for precise coalignment of the NIR beam with the visible light path (~2 µm versus ~8 µm beam broadening respectively) consistent with limited particle-to-particle energy transfer, superlinear power dependence for emission, and much smaller particle size. Furthermore, the nano-UCPs were superior to a traditional two-camera method for NIR and visible light path alignment in an in vivo Infrared-Laser-Evoked Gene Operator (IR-LEGO) optogenetics assay in the budding yeast S. cerevisiae. In summary, nano-UCPs are powerful new tools for coaligning NIR and

  11. Platinum nanoparticles strongly associated with graphitic carbon nitride as efficient co-catalysts for photocatalytic hydrogen evolution under visible light.

    Science.gov (United States)

    Shiraishi, Yasuhiro; Kofuji, Yusuke; Kanazawa, Shunsuke; Sakamoto, Hirokatsu; Ichikawa, Satoshi; Tanaka, Shunsuke; Hirai, Takayuki

    2014-12-14

    Platinum (Pt) nanoparticles with C3N4) by reduction at 673 K behave as efficient co-catalysts for photocatalytic hydrogen evolution under visible light (λ >420 nm). This is achieved by strong Pt-support interaction due to the high temperature treatment, which facilitates efficient transfer of photoformed conduction band electrons on g-C3N4 to Pt particles.

  12. Theoretical and experimental investigations of efficient light coupling with spatially varied all dielectric striped waveguides

    Science.gov (United States)

    Yilmaz, Y. A.; Tandogan, S. E.; Hayran, Z.; Giden, I. H.; Turduev, M.; Kurt, H.

    2017-07-01

    Integrated photonic systems require efficient, compact, and broadband solutions for strong light coupling into and out of optical waveguides. The present work investigates an efficient optical power transferring the problem between optical waveguides having different widths of in/out terminals. We propose a considerably practical and feasible concept to implement and design an optical coupler by introducing gradually index modulation to the coupler section. The index profile of the coupler section is modulated with a Gaussian function by the help of striped waveguides. The effective medium theory is used to replace the original spatially varying index profile with dielectric stripes of a finite length/width having a constant effective refractive index. 2D and 3D finite-difference time-domain analyzes are utilized to investigate the sampling effect of the designed optical coupler and to determine the parameters that play a crucial role in enhancing the optical power transfer performance. Comparing the coupling performance of conventional benchmark adiabatic and butt couplers with the designed striped waveguide coupler, the corresponding coupling efficiency increases from approximately 30% to 95% over a wide frequency interval. In addition, to realize the realistic optical coupler appropriate to integrated photonic applications, the proposed structure is numerically designed on a silicon-on-insulator wafer. The implemented SOI platform based optical coupler operates in the telecom wavelength regime (λ = 1.55 μm), and the dimensions of the striped coupler are kept as 9.77 μm (along the transverse to propagation direction) and 7.69 μm (along the propagation direction) where the unit distance is fixed to be 465 nm. Finally, to demonstrate the operating design principle, the microwave experiments are conducted and the spot size conversion ratio as high as 7.1:1 is measured, whereas a coupling efficiency over 60% in the frequency range of 5.0-16.0 GHz has been also

  13. Light

    DEFF Research Database (Denmark)

    Prescott, N.B.; Kristensen, Helle Halkjær; Wathes, C.M.

    2004-01-01

    This chapter presents the effect of artificial light environments (light levels, colour, photoperiod and flicker) on the welfare of broilers in terms of vision, behaviour, lameness and mortality......This chapter presents the effect of artificial light environments (light levels, colour, photoperiod and flicker) on the welfare of broilers in terms of vision, behaviour, lameness and mortality...

  14. Stopped Light at High Storage Efficiency in a Pr3 + :Y2SiO5 Crystal

    Science.gov (United States)

    Schraft, Daniel; Hain, Marcel; Lorenz, Nikolaus; Halfmann, Thomas

    2016-02-01

    We demonstrate efficient storage and retrieval of light pulses by electromagnetically induced transparency (EIT) in a Pr3 +:Y2SiO5 crystal. Using a ring-type multipass configuration, we increase the optical depth (OD) of the medium up to a factor of 16 towards OD ≈96 . Combining the large optical depth with optimized conditions for EIT, we reach a light storage efficiency of (76.3 ±3.5 )% . In addition, we perform extended systematic measurements of the storage efficiency versus optical depth, control Rabi frequency, and probe pulse duration. The data confirm the theoretically expected behavior of an EIT-driven solid-state memory.

  15. Highly efficient greenish-blue platinum-based phosphorescent organic light-emitting diodes on a high triplet energy platform

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Y. L., E-mail: yilu.chang@mail.utoronto.ca; Gong, S., E-mail: sgong@chem.utoronto.ca; White, R.; Lu, Z. H., E-mail: zhenghong.lu@utoronto.ca [Department of Materials Science and Engineering, University of Toronto, 184 College St., Toronto, Ontario M5S 3E4 (Canada); Wang, X.; Wang, S., E-mail: wangs@chem.queensu.ca [Department of Chemistry, Queen' s University, 90 Bader Lane, Kingston, Ontario K7L 3N6 (Canada); Yang, C. [Department of Chemistry, Wuhan University, Wuhan 430072 (China)

    2014-04-28

    We have demonstrated high-efficiency greenish-blue phosphorescent organic light-emitting diodes (PHOLEDs) based on a dimesitylboryl-functionalized C^N chelate Pt(II) phosphor, Pt(m-Bptrz)(t-Bu-pytrz-Me). Using a high triplet energy platform and optimized double emissive zone device architecture results in greenish-blue PHOLEDs that exhibit an external quantum efficiency of 24.0% and a power efficiency of 55.8 lm/W. This record high performance is comparable with that of the state-of-the-art Ir-based sky-blue organic light-emitting diodes.

  16. Light energy partitioning, photosynthetic efficiency and biomass allocation in invasive Prunus serotina and native Quercus petraea in relation to light environment, competition and allelopathy.

    Science.gov (United States)

    Robakowski, Piotr; Bielinis, Ernest; Sendall, Kerrie

    2018-02-07

    This study addressed whether competition under different light environments was reflected by changes in leaf absorbed light energy partitioning, photosynthetic efficiency, relative growth rate and biomass allocation in invasive and native competitors. Additionally, a potential allelopathic effect of mulching with invasive Prunus serotina leaves on native Quercus petraea growth and photosynthesis was tested. The effect of light environment on leaf absorbed light energy partitioning and photosynthetic characteristics was more pronounced than the effects of interspecific competition and allelopathy. The quantum yield of PSII of invasive P. serotina increased in the presence of a competitor, indicating a higher plasticity in energy partitioning for the invasive over the native Q. petraea, giving it a competitive advantage. The most striking difference between the two study species was the higher crown-level net CO 2 assimilation rates (A crown ) of P. serotina compared with Q. petraea. At the juvenile life stage, higher relative growth rate and higher biomass allocation to foliage allowed P. serotina to absorb and use light energy for photosynthesis more efficiently than Q. petraea. Species-specific strategies of growth, biomass allocation, light energy partitioning and photosynthetic efficiency varied with the light environment and gave an advantage to the invader over its native competitor in competition for light. However, higher biomass allocation to roots in Q. petraea allows for greater belowground competition for water and nutrients as compared to P. serotina. This niche differentiation may compensate for the lower aboveground competitiveness of the native species and explain its ability to co-occur with the invasive competitor in natural forest settings.

  17. Estimating crop yield using a satellite-based light use efficiency model

    DEFF Research Database (Denmark)

    Yuan, Wenping; Chen, Yang; Xia, Jiangzhou

    2016-01-01

    for simulating crops’ GPP. At both irrigated and rainfed sites, the EC-LUE model exhibits a similar level of performance. However, large errors are found when simulating yield based on crop harvest index. This analysis highlights the need to improve the representation of the harvest index and carbon allocation......Satellite-based techniques that provide temporally and spatially continuous information over vegetated surfaces have become increasingly important in monitoring the global agriculture yield. In this study, we examine the performance of a light use efficiency model (EC-LUE) for simulating the gross...... primary production (GPP) and yield of crops. The EC-LUE model can explain on average approximately 90% of the variability in GPP for 36 FLUXNET sites globally. The results indicate that a universal set of parameters, independent of crop species (except for C4 crops), can be adopted in the EC-LUE model...

  18. Semiconductor heterostructures and optimization of light-trapping structures for efficient thin-film solar cells

    International Nuclear Information System (INIS)

    McPheeters, Claiborne O; Yu, Edward T; Hu, Dongzhi; Schaadt, Daniel M

    2012-01-01

    Sub-wavelength photonic structures and nanoscale materials have the potential to greatly improve the efficiencies of solar cells by enabling maximum absorption of sunlight. Semiconductor heterostructures provide versatile opportunities for improving absorption of infrared radiation in photovoltaic devices, which accounts for half of the power in the solar spectrum. These ideas can be combined in quantum-well solar cells and related structures in which sub-wavelength metal and dielectric scattering elements are integrated for light trapping. Measurements and simulations of GaAs solar cells with less than one micron of active material demonstrate the benefits of incorporating In(Ga)As quantum-wells and quantum-dots to improve their performance. Simulations that incorporate a realistic model of absorption in quantum-wells show that the use of broadband photonic structures with such devices can substantially improve the benefit of incorporating heterostructures, enabling meaningful improvements in their performance

  19. The Global Drivers of Photosynthesis and Light Use Efficiency Seasonality: A Granger Frequency Causality Analysis

    Science.gov (United States)

    Nemani, Ramakrishna R.

    2016-01-01

    Photosynthesis and light use efficiency (LUE) are major factors in the evolution of the continental carbon cycle due to their contribution to gross primary production (GPP). However, while the drivers of photosynthesis and LUE on a plant or canopy scale can often be identified, significant uncertainties exist when modeling these on a global scale. This is due to sparse observations in regions such as the tropics and the lack of a direct global observation dataset. Although others have attempted to address this issue using correlations (Beer, 2010) or calculating GPP from vegetation indices (Running, 2004), in this study we take a new approach. We combine the statistical method of Granger frequency causality and partial Granger frequency causality with remote sensing data products (including sun-induced fluorescence used as a proxy for GPP) to determine the main environmental drivers of GPP across the globe.

  20. Study of organic light emitting devices (OLEDs) with optimal emission efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Jai [School of Engineering and IT, B-purple 12, Faculty of EHS, Charles Darwin University, Darwin, NT 0909 (Australia)

    2010-04-15

    The external emission efficiency of organic light emitting devices (OLEDs) is analysed by studying the rate of spontaneous emission of both singlet and triplet excitons and their corresponding radiative lifetimes. Rates of spontaneous emissions are calculated from the first order perturbation theory using the newly discovered time-dependent spin-orbit-exciton-photon interaction operator as the perturbation operator. It is clearly shown how the new interaction operator is responsible for attracting triplet excitons to a phosphor (heavy metal atom) and then it flips the spins to a singlet configuration. Thus, the spin forbidden transition becomes spin allowed. Calculated rates agree with the experimental results qualitatively. Results are of general interests for OLED studies. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Harvesting solar light with crystalline carbon nitrides for efficient photocatalytic hydrogen evolution

    KAUST Repository

    Bhunia, Manas Kumar

    2014-08-14

    Described herein is the photocatalytic hydrogen evolution using crystalline carbon nitrides (CNs) obtained by supramolecular aggregation followed by ionic melt polycondensation (IMP) using melamine and 2,4,6-triaminopyrimidine as a dopant. The solid state NMR spectrum of 15N-enriched CN confirms the triazine as a building unit. Controlling the amount and arrangements of dopants in the CN structure can dramatically enhance the photocatalytic performance for H2 evolution. The polytriazine imide (PTI) exhibits the apparent quantum efficiency (AQE) of 15% at 400 nm. This method successfully enables a substantial amount of visible light to be harvested for H2 evolution, and provides a promising route for the rational design of a variety of highly active crystalline CN photocatalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Energy-efficiency labels and standards: A guidebook for appliances, equipment and lighting

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, James E.; Wiel, Stephen

    2001-02-16

    Energy-performance improvements in consumer products are an essential element in any government's portfolio of energy-efficiency and climate change mitigation programs. Governments need to develop balanced programs, both voluntary and regulatory, that remove cost-ineffective, energy-wasting products from the marketplace and stimulate the development of cost-effective, energy-efficient technology. Energy-efficiency labels and standards for appliances, equipment, and lighting products deserve to be among the first policy tools considered by a country's energy policy makers. The U.S. Agency for International Development (USAID) and the United Nations Foundation (UNF) recognize the need to support policy makers in their efforts to implement energy-efficiency standards and labeling programs and have developed this guidebook, together with the Collaborative Labeling and Appliance Standards Program (CLASP), as a primary reference. This guidebook was prepared over the course of the past year with significant contribution from the authors and reviewers mentioned previously. Their diligent participation has made this the international guidance tool it was intended to be. The lead authors would also like to thank the following individuals for their support in the development, production, and distribution of the guidebook: Marcy Beck, Elisa Derby, Diana Dhunke, Ted Gartner, and Julie Osborn of Lawrence Berkeley National Laboratory as well as Anthony Ma of Bevilacqua-Knight, Inc. This guidebook is designed as a manual for government officials and others around the world responsible for developing, implementing, enforcing, monitoring, and maintaining labeling and standards-setting programs. It discusses the pros and cons of adopting energy-efficiency labels and standards and describes the data, facilities, and institutional and human resources needed for these programs. It provides guidance on the design, development, implementation, maintenance, and evaluation of the

  3. Efficient Light-Driven Water Oxidation Catalysis by Dinuclear Ruthenium Complexes.

    Science.gov (United States)

    Berardi, Serena; Francàs, Laia; Neudeck, Sven; Maji, Somnath; Benet-Buchholz, Jordi; Meyer, Franc; Llobet, Antoni

    2015-11-01

    Mastering the light-induced four-electron oxidation of water to molecular oxygen is a key step towards the achievement of overall water splitting to produce alternative solar fuels. In this work, we report two rugged molecular pyrazolate-based diruthenium complexes that efficiently catalyze visible-light-driven water oxidation. These complexes were fully characterized both in the solid state (by X-ray diffraction analysis) and in solution (spectroscopically and electrochemically). Benchmark performances for homogeneous oxygen production have been obtained for both catalysts in the presence of a photosensitizer and a sacrificial electron acceptor at pH 7, and a turnover frequency of up to 11.1 s(-1) and a turnover number of 5300 were obtained after three successive catalytic runs. Under the same experimental conditions with the same setup, the pyrazolate-based diruthenium complexes outperform other well-known water oxidation catalysts owing to both electrochemical and mechanistic aspects. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Quantum Dots in Two-Dimensional Perovskite Matrices for Efficient Near-Infrared Light Emission

    KAUST Repository

    Yang, Zhenyu

    2017-03-13

    Quantum-dot-in-perovskite solids are excellent candidates for infrared light-emitting applications. The first generation of dot-in-perovskite light-emitting diodes (LEDs) has shown bright infrared electroluminescence with tunable emission wavelength; however, their performance has been limited by degradation of the active layer at practical operating voltages. This arises from the instability of the three-dimensional (3D) organolead halide perovskite matrix. Herein we report the first dot-in-perovskite solids that employ two-dimensional (2D) perovskites as the matrix. 2D perovskite passivation is achieved via an in situ alkylammonium/alkylamine substitution carried out during the quantum dot (QD) ligand exchange process. This single-step film preparation process enables deposition of the QD/perovskite active layers with thicknesses of 40 nm, over seven times thinner than the first-generation dot-in-perovskite thin films that relied on a multistep synthesis. The dot-in-perovskite film roughness improved from 31 nm for the first-generation films to 3 nm for films as a result of this new approach. The best devices exhibit external quantum efficiency peaks exceeding 2% and radiances of ∼1 W sr–1 m–2, with an improved breakdown voltage up to 7.5 V. Compared to first-generation dot-in-perovskites, this new process reduces materials consumptions 10-fold and represents a promising step toward manufacturable devices.

  5. High-efficient light absorption of monolayer graphene via cylindrical dielectric arrays and the sensing application

    Science.gov (United States)

    Zhou, Peng; Zheng, Gaige

    2018-04-01

    The efficiency of graphene-based optoelectronic devices is typically limited by the poor absolute absorption of light. A hybrid structure of monolayer graphene with cylindrical titanium dioxide (TiO2) array and aluminum oxide (Al2O3) spacer layer on aluminum (Al) substrate has been proposed to enhance the absorption for two-dimensional (2D) materials. By combining dielectric array with metal substrate, the structure achieves multiple absorption peaks with near unity absorbance at near-infrared wavelengths due to the resonant effect of dielectric array. Completed monolayer graphene is utilized in the design without any demand of manufacture process to form the periodic patterns. Further analysis indicates that the near-field enhancement induced by surface modes gives rise to the high absorption. This favorable field enhancement and tunability of absorption not only open up new approaches to accelerate the light-graphene interaction, but also show great potential for practical applications in high-performance optoelectronic devices, such as modulators and sensors.

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

    Science.gov (United States)

    Maeda, Kazuhiko

    2014-02-12

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

  7. stableGP

    Data.gov (United States)

    National Aeronautics and Space Administration — The code in the stableGP package implements Gaussian process calculations using efficient and numerically stable algorithms. Description of the algorithms is in the...

  8. Review of organic light-emitting diodes with thermally activated delayed fluorescence emitters for energy-efficient sustainable light sources and displays

    Science.gov (United States)

    Volz, Daniel

    2016-04-01

    Thermally activated delayed fluorescence (TADF) is an emerging hot topic. Even though this photophysical mechanism itself has been described more than 50 years ago and optoelectronic devices with organic matter have been studied, improved, and even commercialized for decades now, the realization of the potential of TADF organic light-emitting diodes (OLEDs) happened only recently. TADF has been proven to be an attractive and very efficient alternative for phosphorescent materials, such as dopants in OLEDs, light-emitting electrochemical cells as well as potent emitters for chemiluminescence. In this review, the TADF concept is introduced in terms that are also understandable for nonchemists. The basic concepts behind this mechanism as well as state-of-the-art examples are discussed. In addition, the future economic impact, especially for the lighting and display market, is addressed here. We conclude that TADF materials are especially helpful to realize efficient, durable deep blue and white displays.

  9. Self-assembly of natural light-harvesting bacteriochlorophylls of green sulfur photosynthetic bacteria in silicate capsules as stable models of chlorosomes.

    Science.gov (United States)

    Saga, Yoshitaka; Akai, Sho; Miyatake, Tomohiro; Tamiaki, Hitoshi

    2006-01-01

    Naturally occurring bacteriochlorophyll(BChl)s-c, -d, and -e from green sulfur photosynthetic bacteria were self-assembled in an aqueous solution in the presence of octadecyltriethoxysilane and tetraethoxysilane, followed by polycondensation of the alkoxysilanes by incubation for 50 h at 25 degrees C. The resulting BChl self-assemblies in silicate capsules exhibited visible absorption and circular dichroism spectra similar to the corresponding natural light-harvesting systems (chlorosomes) of green sulfur bacteria. Dynamic light scattering measurements indicated that the silicate capsules had an average hydrodynamic diameter of several hundred nanometers. BChl self-aggregates in silicate capsules were significantly stable to a nonionic surfactant Triton X-100, which was apt to decompose the BChl aggregates to their monomeric form, compared with conventional micelle systems. BChls in silicate capsules were more tolerant to demetalation of the central magnesium under acidic conditions than the natural systems.

  10. A performance improvement and cost-efficient ACO-OFDM scheme for visible light communications

    Science.gov (United States)

    Zhang, Tiantian; Zhou, Ji; Zhang, Zhenshan; Qiao, Yaojun; Su, Fei; Yang, Aiying

    2017-11-01

    In this paper, we propose a performance improvement and cost-efficient discrete Hartley transform (DHT)-based asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) scheme for visible light communications (VLC). The simple one-dimensional modulation constellation and simplified encoding structure reduce the complexity of system considerably. The DHT-spreading technique is employed to reduce peak-to-average power ratio (PAPR) of ACO-OFDM signals. Moreover, the intra-symbol frequency-domain averaging (ISFA) technique is used to increase the accuracy of channel estimation by removing the effect of ambient noise in the VLC channel effectively. To verify the feasibility of the proposed scheme, we study its performance via simulation. This scheme reduces the requirement to the resolution of DAC and increases the tolerance to the nonlinear characteristics of LED, both of which are cost-efficient. At forward error correction (FEC) limit (BER = 1 × 10-3), simulation results illustrate that compared with DHT-based ACO-OFDM without the ISFA technique, our scheme has 3.2 dB and 2.7 dB improvement of the required Eb /N0 when BPSK and 4-PAM are modulated, respectively.

  11. Improving Global Gross Primary Productivity Estimates by Computing Optimum Light Use Efficiencies Using Flux Tower Data

    Science.gov (United States)

    Madani, Nima; Kimball, John S.; Running, Steven W.

    2017-11-01

    In the light use efficiency (LUE) approach of estimating the gross primary productivity (GPP), plant productivity is linearly related to absorbed photosynthetically active radiation assuming that plants absorb and convert solar energy into biomass within a maximum LUE (LUEmax) rate, which is assumed to vary conservatively within a given biome type. However, it has been shown that photosynthetic efficiency can vary within biomes. In this study, we used 149 global CO2 flux towers to derive the optimum LUE (LUEopt) under prevailing climate conditions for each tower location, stratified according to model training and test sites. Unlike LUEmax, LUEopt varies according to heterogeneous landscape characteristics and species traits. The LUEopt data showed large spatial variability within and between biome types, so that a simple biome classification explained only 29% of LUEopt variability over 95 global tower training sites. The use of explanatory variables in a mixed effect regression model explained 62.2% of the spatial variability in tower LUEopt data. The resulting regression model was used for global extrapolation of the LUEopt data and GPP estimation. The GPP estimated using the new LUEopt map showed significant improvement relative to global tower data, including a 15% R2 increase and 34% root-mean-square error reduction relative to baseline GPP calculations derived from biome-specific LUEmax constants. The new global LUEopt map is expected to improve the performance of LUE-based GPP algorithms for better assessment and monitoring of global terrestrial productivity and carbon dynamics.

  12. Efficient green phosphorescent tandem organic light emitting diodes with solution processable mixed hosts charge generating layer

    Energy Technology Data Exchange (ETDEWEB)

    Talik, N.A.; Yeoh, K.H.; Ng, C.Y.B [Low Dimensional Research Center, Department of Physics, University Malaya, 50603 Kuala Lumpur (Malaysia); ItraMAS Corporation. Sdn. Bhd., 542A-B Mukim 1, Lorong Perusahaan Baru 2, Kawasan Perindustrian, Perai 13600, Penang (Malaysia); Yap, B.K. [Center of Microelectronic and Nanotechnology Engineering (CeMNE), College of Engineering, Universiti Tenaga Nasional, Jln. Uniten-Ikram, 4300 Kajang, Selangor (Malaysia); Woon, K.L., E-mail: ph7klw76@um.edu.my [Low Dimensional Research Center, Department of Physics, University Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-10-15

    A novel solution processable charge generating layer (CGL) that consists of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HATCN{sub 6})/Poly(N-vinylcarbazole) (PVK): 1,1-bis-(4-bis(4-tolyl)-aminophenyl) cyclohexene (TAPC) for a tandem green phosphorescent organic light emitting diode (PHOLED) is demonstrated. The use of orthogonal solvent to dissolve HATCN{sub 6} and PVK:TAPC is the key to overcome the interface erosion problem for the solution processed CGL. The current efficiency of the 2 wt% TAPC mixed with PVK is the highest at 24.2 cd/A, which is more than three-folds higher than that of the single device at 1000 cd/m{sup 2}. - Highlights: • A solution processable tandem OLED is built using a novel charge generating layer. • HATCN{sub 6} and PVK:TAPC are shown to be effective charge generating layers. • The turn on voltages for tandem devices are almost similar to single unit. • 2 wt% TAPC blended with PVK exhibits three-folds increase in efficiency.

  13. Enhancing the Light-Extraction Efficiency of AlGaN Nanowires Ultraviolet Light-Emitting Diode by using Nitride/Air Distributed Bragg Reflector Nanogratings

    KAUST Repository

    Alias, Mohd Sharizal

    2017-09-11

    The performance and efficiency of AlGaN ultraviolet light-emitting diodes have been limited by the extremely low light-extraction efficiency (LEE) due to the intrinsic material properties of AlGaN. Here, to enhance the LEE of the device, we demonstrate an AlGaN nanowires light-emitting diode (NWs-LED) integrated with nitride/air Distributed Bragg Reflector (DBR) nanogratings. Compared to a control device (only mesa), the AlGaN NWs-LED with the nitride/air DBR nanogratings exhibit enhancement in the light output power and external quantum efficiency (EQE) by a factor of ∼1.67. The higher light output power and EQE are attributed mainly to the multiple reflectances laterally for the transverse magnetic (TM)-polarized light and scattering introduced by the nanogratings. To further understand the LEE enhancement, the electrical field distribution, extraction ratio and polar pattern of the AlGaN NWs-LED with and without the nitride/air DBR nanogratings were analyzed using the finite-difference-time-domain method. It was observed that the TM-field emission was confined and scattered upward whereas the polar pattern was intensified for the AlGaN NWs-LED with the nanogratings. Our approach to enhance the LEE via the nitride/air DBR nanogratings can provide a promising route for increasing the efficiency of AlGaN-based LEDs, also, to functioning as facet mirror for AlGaN-based laser diodes.

  14. The production of consuming less: Energy efficiency, climate change, and light bulbs in North Carolina

    Science.gov (United States)

    Thoyre, Autumn

    In this research, I have analyzed the production of consuming less electricity through a case study of promotions of compact fluorescent light bulbs (CFLs). I focused on the CFL because it has been heavily promoted by environmentalists and electricity companies as a key tool for solving climate change, yet such promotions appear counter-intuitive. The magnitude of CFL promotions by environmentalists is surprising because CFLs can only impact less than 1% of U.S. greenhouse gas emissions. CFL promotions by electricity providers are surprising given such companies' normal incentives to sell more of their product. I used political ecological and symbolic interactionist theories, qualitative methods of data collection (including interviews, participant-observation, texts, and images), and a grounded theory analysis to understand this case. My findings suggest that, far from being a self-evident technical entity, energy efficiency is produced as an idea, a part of identities, a resource, and a source of value through social, political, and economic processes. These processes include identity formation and subjectification; gender-coded household labor; and corporate appropriation of household value resulting from environmental governance. I show how environmentalists use CFLs to make and claim neoliberal identities, proposing the concept of green neoliberal identity work as a mechanism through which neoliberal ideologies are translated into practices. I analyze how using this seemingly easy energy efficient technology constitutes labor that is gendered in ways that reflect and reproduce inequalities. I show how electricity companies have used environmental governance to valorize and appropriate home energy efficiency as an accumulation strategy. I conclude by discussing the symbolic power of CFLs, proposing a theory of green obsolescence, and framing the production of energy efficiency as a global production network. I found that promoting energy efficiency involves

  15. Quantitative Investigation of Efficiency of Ultraviolet and Visible Light in Eradication of Candida albicans In Vitro

    Science.gov (United States)

    Maver-Bišćanin, Mirela; Mravak-Stipetić, Marinka; Bukovski, Suzana; Bišćanin, Alen

    2014-01-01

    Abstract Objective: The aim of this study was to quantitatively investigate the efficiency of the ultraviolet (UV) and visible light in eradication of Candida albicans in vitro; in particular, to determine, for selected wavelengths, the specific eradication coefficients and thresholds in terms of energy density levels required to effect 3.0log10 and 4.0log10 reduction. Background data: Oral candidosis is the most common infection of the oral cavity and is caused by Candida species. The widespread use of topical and systemic antifungal agents as conventional treatment for oral candidosis has resulted in the development of resistance in C. albicans. Therefore, it has become necessary to develop alternative therapies for the treatment of oral candidosis. Methods: C. albicans ATCC® 90028™ was irradiated with 254 nm, 365 nm, 406 nm, 420 nm, and broadband Xe spectrum. For each wavelength, a fit of experimental data (survival fraction vs. applied energy density) with an exponential decay function enabled estimation of the specific eradication coefficients and thresholds. Results: Based on estimated specific efficiencies (Δ) and eradication thresholds (ET) of the investigated wavelengths, the ranking in eradication efficiency of C. albicans (most to least effective) is: 254 nm (Δ=6.1 mJ/cm−2, ET99.99=56 mJ/cm−2), broadband Xe spectrum (Δ=27.7 mJ/cm−2, ET99.99=255 mJ/cm−2), 365 nm (Δ=4.3 J/cm−2, ET99.99=39 J/cm−2), 420 nm (Δ=0.65 J/cm−2, ET99.99=6 J/cm−2), and 406 nm (Δ=11.4 J/cm−2, ET99.99=104 J/cm−2). Conclusions: The results provide insight into the wavelength-dependent dynamics of eradication of C. albicans. For each investigated wavelength, the eradication coefficient and corresponding eradication threshold were estimated. The observed different eradication efficiencies are consequence of different spectrally dependent inactivation mechanisms. The established methodology enables unambiguous quantitative

  16. Photosynthesis, Light Use Efficiency, and Yield of Reduced-Chlorophyll Soybean Mutants in Field Conditions

    Science.gov (United States)

    Slattery, Rebecca A.; VanLoocke, Andy; Bernacchi, Carl J.; Zhu, Xin-Guang; Ort, Donald R.

    2017-01-01

    Reducing chlorophyll (chl) content may improve the conversion efficiency of absorbed photosynthetically active radiation into biomass and therefore yield in dense monoculture crops by improving light penetration and distribution within the canopy. The effects of reduced chl on leaf and canopy photosynthesis and photosynthetic efficiency were studied in two reportedly robust reduced-chl soybean mutants, Y11y11 and y9y9, in comparison to the wild-type (WT) “Clark” cultivar. Both mutants were characterized during the 2012 growing season whereas only the Y11y11 mutant was characterized during the 2013 growing season. Chl deficiency led to greater rates of leaf-level photosynthesis per absorbed photon early in the growing season when mutant chl content was ∼35% of the WT, but there was no effect on photosynthesis later in the season when mutant leaf chl approached 50% of the WT. Transient benefits of reduced chl at the leaf level did not translate to improvements in canopy-level processes. Reduced pigmentation in these mutants was linked to lower water use efficiency, which may have dampened any photosynthetic benefits of reduced chl, especially since both growing seasons experienced significant drought conditions. These results, while not confirming our hypothesis or an earlier published study in which the Y11y11 mutant significantly outyielded the WT, do demonstrate that soybean significantly overinvests in chl. Despite a >50% chl reduction, there was little negative impact on biomass accumulation or yield, and the small negative effects present were likely due to pleiotropic effects of the mutation. This outcome points to an opportunity to reinvest nitrogen and energy resources that would otherwise be used in pigment-proteins into increasing biochemical photosynthetic capacity, thereby improving canopy photosynthesis and biomass production. PMID:28458677

  17. Stable silver nanoclusters electrochemically deposited on nitrogen-doped graphene as efficient electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Jin, Shi; Chen, Man; Dong, Haifeng; He, Bingyu; Lu, Huiting; Su, Lei; Dai, Wenhao; Zhang, Qiaochu; Zhang, Xueji

    2015-01-01

    Metal nanoclusters exhibit unusually high catalytic activity toward oxygen reduction reaction (ORR) due to their small size and unique electronic structures. However, controllable synthesis of stable metal nanoclusters is a challenge, and the durability of metal clusters suffers from the deficiency of dissolution, aggregation, and sintering during catalysis reactions. Herein, silver nanoclusters (AgNCs) (diameter , which is vital in high performance fuel cells, batteries and nanodevices.

  18. Strategy of Solution-Processed All-Inorganic Heterostructure for Humidity/Temperature-Stable Perovskite Quantum Dot Light-Emitting Diodes.

    Science.gov (United States)

    Shi, Zhifeng; Li, Sen; Li, Ying; Ji, Huifang; Li, Xinjian; Wu, Di; Xu, Tingting; Chen, Yongsheng; Tian, Yongtao; Zhang, Yuantao; Shan, Chongxin; Du, Guotong

    2018-02-27

    Recently, a pressing requirement of solid-state lighting sources with high performance and low cost has motivated increasing research in metal halide perovskites. However, the relatively low emission efficiency and poor operation stability of perovskite light-emitting diodes (LEDs) are still critical drawbacks. In this study, a strategy of solution-processed all-inorganic heterostructure was proposed to overcome the emission efficiency and operation stability issues facing the challenges of perovskite LEDs. Solution-processed n-ZnO nanoparticles and p-NiO are used as the carrier injectors to fabricate all-inorganic heterostructured CsPbBr 3 quantum dot LEDs, and a high-efficiency green emission is achieved with maximum luminance of 6093.2 cd/m 2 , external quantum efficiency of 3.79%, and current efficiency of 7.96 cd/A. More importantly, the studied perovskite LEDs possess a good operation stability after a long test time in air ambient. Typically, the devices can endure a high humidity (75%, 12 h) and a high working temperature (393 K, three heating/cooling cycles) even without encapsulation, and the operation stability is better than any previous reports. It is anticipated that this work will provide an effective strategy for the fabrication of high-performance perovskite LEDs with good stability under ambient and harsh conditions, making practical applications of such LEDs a real possibility.

  19. An isopropanol-assisted fabrication strategy of pinhole-free perovskite films in air for efficient and stable planar perovskite solar cells

    Science.gov (United States)

    Ren, Ziqiu; Zhu, Menghua; Li, Xin; Dong, Cunku

    2017-09-01

    As a promising photovoltaic device, perovskite solar cells have attracted numerous attention in recent years, where forming a compact and pinhole-free perovskite film in air is of great importance. Herein, we evaluate highly efficient and air stable planar perovskite solar cells in air (relative humidity over 50%) with the modified two-step sequential deposition method by adjusting the CH3NH3I (MAI) concentrations and regulating the crystallization process of the perovskite film. The optimum MAI concentration is 60 mg mL-1 in isopropanol. With a planar structure of FTO/TiO2/MAPbI3/spiro-OMeTAD/Au, the efficient devices composed of compact and pinhole-free perovskite films are constructed in air, achieving a high efficiency of up to 15.10% and maintaining over 80% after 20 days storing without any encapsulation in air. With a facile fabrication process and high photovoltaic performance, this work represents a promising method for fabricating low-cost, highly efficient and stable photovoltaic device.

  20. Fabrication of Photothermal Stable Gold Nanosphere/Mesoporous Silica Hybrid Nanoparticle Responsive to Near-Infrared Light.

    Science.gov (United States)

    Cheng, Bei; Xu, Peisheng

    2017-01-01

    Various gold nanoparticles have been explored in biomedical systems and proven to be promising in photothermal therapy and drug delivery. Among them, nanoshells were regarded as traditionally strong near infrared absorbers that have been widely used to generate photothermal effect for cancer therapy. However, the nanoshell is not photo-thermal stable and thus is not suitable for repeated irradiation. Here, we describe a novel discrete gold nanostructure by mimicking the continuous gold nanoshell-gold/mesoporous silica hybrid nanoparticle (GoMe). It possesses the best characteristics of both conventional gold nanoparticles and mesoporous silica nanoparticles, such as excellent photothermal converting ability as well as high drug loading capacity and triggerable drug release.

  1. Strong enhancement of emission efficiency in GaN light-emitting diodes by plasmon-coupled light amplification of graphene

    Science.gov (United States)

    Kim, Jong Min; Kim, Sung; Hwang, Sung Won; Kim, Chang Oh; Shin, Dong Hee; Kim, Ju Hwan; Jang, Chan Wook; Kang, Soo Seok; Hwang, Euyheon; Choi, Suk-Ho; El-Gohary, Sherif H.; Byun, Kyung Min

    2018-02-01

    Recently, we have demonstrated that excitation of plasmon-polaritons in a mechanically-derived graphene sheet on the top of a ZnO semiconductor considerably enhances its light emission efficiency. If this scheme is also applied to device structures, it is then expected that the energy efficiency of light-emitting diodes (LEDs) increases substantially and the commercial potential will be enormous. Here, we report that the plasmon-induced light coupling amplifies emitted light by ∼1.6 times in doped large-area chemical-vapor-deposition-grown graphene, which is useful for practical applications. This coupling behavior also appears in GaN-based LEDs. With AuCl3-doped graphene on Ga-doped ZnO films that is used as transparent conducting electrodes for the LEDs, the average electroluminescence intensity is 1.2–1.7 times enhanced depending on the injection current. The chemical doping of graphene may produce the inhomogeneity in charge densities (i.e., electron/hole puddles) or roughness, which can play a role as grating couplers, resulting in such strong plasmon-enhanced light amplification. Based on theoretical calculations, the plasmon-coupled behavior is rigorously explained and a method of controlling its resonance condition is proposed.

  2. Strong photocurrent enhancements in plasmonic organic photovoltaics by biomimetic nanoarchitectures with efficient light harvesting.

    Science.gov (United States)

    Leem, Jung Woo; Kim, Sehwan; Park, Chihyun; Kim, Eunkyoung; Yu, Jae Su

    2015-04-01

    We propose the biomimetic moth-eye nanoarchitectures as a novel plasmonic light-harvesting structure for further enhancing the solar-generated photocurrents in organic photovoltaics (OPVs). The full moth-eye nanoarchitectures are composed of two-dimensional hexagonal periodic grating arrays on surfaces of both the front zinc oxide (ZnO) and rear active layers, which are prepared by a simple and cost-effective soft imprint nanopatterning technique. For the 380 nm period ZnO and 650 nm period active gratings (i.e., ZnO(P380)/Active(P650)), the poly(3-hexylthiophene-2,5-diyl):indene-C60 bis-adduct (P3HT:ICBA)-based plasmonic OPVs exhibit an improvement of the absorption spectrum compared to the pristine OPVs over a broad wavelength range of 350-750 nm, showing absorption enhancement peaks at wavelengths of ∼370, 450, and 670 nm, respectively. This leads to a considerable increase of short-circuit current density (Jsc) from 10.9 to 13.32 mA/cm(2), showing a large Jsc enhancement percentage of ∼22.2%. As a result, the strongly improved power conversion efficiency (PCE) of 6.28% is obtained compared to that (i.e., PCE = 5.12%) of the pristine OPVs. For the angle-dependent light-absorption characteristics, the plasmonic OPVs with ZnO(P380)/Active(P650) have a better absorption performance than that of the pristine OPVs at incident angles of 20-70°. For optical absorption characteristics and near-field intensity distributions of plasmonic OPVs, theoretical analyses are also performed by a rigorous coupled-wave analysis method, which gives a similar tendency with the experimentally measured data.

  3. Highly Efficient and Visible Light Responsive Heterojunction Composites as Dual Photoelectrodes for Photocatalytic Fuel Cell

    Directory of Open Access Journals (Sweden)

    Honghui Pan

    2018-01-01

    Full Text Available In the present work, a novel photocatalytic fuel cell (PFC system involving a dual heterojunction photoelectrodes, viz. polyaniline/TiO2 nanotubes (PANI/TiO2 NTs photoanode and CuO/Co3O4 nanorods (CuO/Co3O4 NRs photocathode, has been designed. Compared to TiO2 NTs electrode of PFC, the present heterojunction design not only enhances the visible light absorption but also offers the higher efficiency in degrading Rhodamine B–a model organic pollutant. The study includes an evaluation of the dual performance of the photoelectrodes as well. Under visible-light irradiation of 3 mW cm−2, the cell composed of the photoanode PANI/TiO2 NTs and CuO/Co3O4 NRs photocathode forms an interior bias of +0.24 V within the PFC system. This interior bias facilitated the transfer of electrons from the photoanode to photocathode across the external circuit and combined with the holes generated therein along with a simultaneous power production. In this manner, the separation of electron/hole pair was achieved in the photoelectrodes by releasing the holes and electrons of PANI/TiO2 NTs photoanode and CuO/Co3O4 NRs photocathode, respectively. Using this PFC system, the degradation of Rhodamine B in aqueous media was achieved to an extent of 68.5% within a reaction duration of a four-hour period besides a simultaneous power generation of 85 μA cm−2.

  4. A high efficient protocol for soybean root transformation by Agrobacterium rhizogenes and most stable reference genes for RT-qPCR analysis.

    Science.gov (United States)

    Kuma, K M; Lopes-Caitar, V S; Romero, C C T; Silva, S M H; Kuwahara, M K; Carvalho, M C C G; Abdelnoor, R V; Dias, W P; Marcelino-Guimarães, F C

    2015-11-01

    A 55% transformation efficiency was obtained by our optimized protocol; and we showed that GmELF1 - β and GmELF1 - α are the most stable reference genes for expression analyses under this specific condition. Gene functional analyses are essential to the validation of results obtained from in silico and/or gene-prospecting studies. Genetic transformation methods that yield tissues of transient expression quickly have been of considerable interest to researchers. Agrobacterium rhizogenes-mediated transformation methods, which are employed to generate plants with transformed roots, have proven useful for the study of stress caused by root phytopathogens via gene overexpression and/or silencing. While some protocols have been adapted to soybean plants, transformation efficiencies remain limited; thus, few viable plants are available for performing bioassays. Furthermore, mRNA analyses that employ reverse transcription quantitative polymerase chain reactions (RT-qPCR) require the use of reference genes with stable expression levels across different organs, development steps and treatments. In the present study, an A. rhizogenes-mediated soybean root transformation approach was optimized. The method delivers significantly higher transformation efficiency levels and rates of transformed plant recovery, thus enhancing studies of soybean abiotic conditions or interactions between phytopathogens, such as nematodes. A 55% transformation efficiency was obtained following the addition of an acclimation step that involves hydroponics and different selection processes. The present study also validated the reference genes GmELF1-β and GmELF1-α as the most stable to be used in RT-qPCR analysis in composite plants, mainly under nematode infection.

  5. Highly efficient green light harvesting from Mg doped ZnO nanoparticles: Structural and optical studies

    International Nuclear Information System (INIS)

    Sharma, Sarla; Vyas, Rishi; Sharma, Neha; Singh, Vidyadhar; Singh, Arvind; Kataria, Vanjula; Gupta, Bipin Kumar; Vijay, Y.K.

    2013-01-01

    Graphical abstract: Demonstration of highly efficient green light emission harvesting from Mg doped ZnO nanoparticles were synthesized via facile wet chemical route with an average particle size ∼15 nm. The resulted nanoparticles exhibit intense green emission peaking at 530 nm upon 325 nm excitation. The photoluminescence (PL) intensity of visible emission depends upon the doping concentration of Mg. The PL intensity was found maximum up to 4% doping of Mg and beyond it exhibits a decrees in emission. The obtained highly luminescent green emission of ZnO nanoparticle would be an ultimate choice for next generation optoelectronics device materials. Highlights: ► Zn 1−x Mg x O nanoparticles were prepared by mechanochemical processing. ► High blue emission intensity was observed contrary to previous reports. ► Blue emission is suggested to be originating from the high density of defects. ► Defect density in as-milled condition is very high resulting in high emission. ► Mg promoted non-radiative recombination and lowered intensities. -- Abstract: Highly efficient green light emission was observed from Mg doped ZnO nanoparticles synthesized via facile wet chemical route with an average particle size ∼15 nm. The XRD analysis confirmed the growth of wurtzite phase of ZnO nanoparticles. Moreover, the optical properties of these nanoparticles were investigated by different spectroscopic techniques. The resulted nanoparticles exhibit intense green emission peaking at 530 nm (2.34 eV) upon 325 nm (3.81 eV) excitation. The photoluminescence (PL) intensity of visible emission depends upon the doping concentration of Mg. The PL intensity was found maximum up to 4% doping of Mg, and beyond it exhibits a decrees in emission. Furthermore, by varying the band gap from 3.50 to 3.61 eV, the PL spectra showed a near band edge (NBE) emission at wavelength around 370 nm (3.35 eV) and a broad deep level emission in the visible region. The obtained highly luminescent green

  6. Surface Emitting, High Efficiency Near-Vacuum Ultraviolet Light Source with Aluminum Nitride Nanowires Monolithically Grown on Silicon.

    Science.gov (United States)

    Zhao, S; Djavid, M; Mi, Z

    2015-10-14

    To date, it has remained challenging to realize electrically injected light sources in the vacuum ultraviolet wavelength range (∼200 nm or shorter), which are important for a broad range of applications, including sensing, surface treatment, and photochemical analysis. In this Letter, we have demonstrated such a light source with molecular beam epitaxially grown aluminum nitride (AlN) nanowires on low cost, large area Si substrate. Detailed angle dependent electroluminescence studies suggest that, albeit the light is TM polarized, the dominant light emission direction is from the nanowire top surface, that is, along the c axis, due to the strong light scattering effect. Such an efficient surface emitting device was not previously possible using conventional c-plane AlN planar structures. The AlN nanowire LEDs exhibit an extremely large electrical efficiency (>85%), which is nearly ten times higher than the previously reported AlN planar devices. Our detailed studies further suggest that the performance of AlN nanowire LEDs is predominantly limited by electron overflow. This study provides important insight on the fundamental emission characteristics of AlN nanowire LEDs and also offers a viable path to realize an efficient surface emitting near-vacuum ultraviolet light source through direct electrical injection.

  7. Efficiency Enhancement of InGaN-Based Solar Cells via Stacking Layers of Light-Harvesting Nanospheres

    KAUST Repository

    Alamri, Amal M.

    2016-06-24

    An effective light-harvesting scheme for InGaN-based multiple quantum well solar cells is demonstrated using stacking layers of polystyrene nanospheres. Light-harvesting efficiencies on the solar cells covered with varied stacks of nanospheres are evaluated through numerical and experimental methods. The numerical simulation reveals that nanospheres with 3 stacking layers exhibit the most improved optical absorption and haze ratio as compared to those obtained by monolayer nanospheres. The experimental demonstration, agreeing with the theoretical analyses, shows that the application of 3-layer nanospheres improves the conversion efficiency of the solar cell by ~31%.

  8. Noble-metal-free g-C3N4/Ni(dmgH)2 composite for efficient photocatalytic hydrogen evolution under visible light irradiation

    Science.gov (United States)

    Cao, Shao-Wen; Yuan, Yu-Peng; Barber, James; Loo, Say Chye Joachim; Xue, Can

    2014-11-01

    We report an economic photocatalytic H2 generation system consisting of earth-abundant elements only by coupling graphitic carbon nitride (g-C3N4) with Ni(dmgH)2 sub-microwires that serve as effective co-catalysts for H2 evolution. This composite photocatalyst exhibits efficient hydrogen evolution under visible-light irradiation in the presence of triethanolamine as electron donor. The optimal coupling of 3.5 wt% Ni(dmgH)2 to g-C3N4 (5 mg composite) allows for a steady H2 generation rate of 1.18 μmol/h with excellent stability. This study demonstrates that the combination of polymeric g-C3N4 semiconductor and small proportion of transition-metal-based co-catalyst could serve as a stable, earth-abundant and low-cost system for solar-to-hydrogen conversion.

  9. Light use efficiency over two temperate steppes in inner Mongolia, China.

    Directory of Open Access Journals (Sweden)

    Yu Wang

    Full Text Available Vegetation light use efficiency (LUE is a key parameter of Production Efficiency Models (PEMs for simulating gross primary production (GPP of vegetation, from regional to global scales. Previous studies suggest that grasslands have the largest inter-site variation of LUE and controlling factors of grassland LUE differ from those of other biomes, since grasslands are usually water-limited ecosystems. Combining eddy covariance flux data with the fraction of photosynthetically active radiation absorbed by the plant canopy from MODIS, we report LUE on a typical steppe and a desert steppe in Inner Mongolia, northern China. Results show that both annual average LUE and maximum LUE were higher on the desert steppe (0.51 and 1.13 g C MJ(-1 than on the typical steppe (0.34 and 0.88 g C MJ(-1, despite the higher GPP of the latter. Water availability was the primary limiting factor of LUE at both sites. Evaporative fraction (EF or the ratio of actual evapotranspiration to potential evapotranspiration (AET/PET can explain 50-70% of seasonal LUE variations at both sites. However, the slope of linear regression between LUE and EF (or AET/PET differed significantly between the two sites. LUE increased with the diffuse radiation ratio on the typical steppe; however, such a trend was not found for the desert steppe. Our results suggest that a biome-dependent LUE(max is inappropriate, because of the large inter-site difference of LUE(max within the biome. EF could be a promising down-regulator on grassland LUE for PEMs, but there may be a site-specific relationship between LUE and EF.

  10. Graphene Oxide by UV-Ozone Treatment as an Efficient Hole Extraction Layer for Highly Efficient and Stable Polymer Solar Cells.

    Science.gov (United States)

    Xia, Yingdong; Pan, Yufeng; Zhang, Haijuan; Qiu, Jian; Zheng, Yiting; Chen, Yonghua; Huang, Wei

    2017-08-09

    The hole extraction layer has a significant impact on the achievement of high-efficiency polymer solar cells (PSCs). Here, we report an efficient approach to direct UV-ozone treatment by larger device performance enhancement employing graphene oxide (GO). The dramatic performance enhancement of PSCs with the P3HT:PCBM blend as an active layer was demonstrated by the UV-ozone treatment of GO for 30 min: best power conversion efficiency (PCE) of 4.18%, fill factor of 0.63, J sc of 10.94 mA cm -2 , and V oc of 0.61 V, which are significantly higher than those of the untreated GO (1.82%) and highly comparable PEDOT:PSS-based PSCs (3.73%). In addition, PSCs with UV-ozone-treated GO showed a longer stability than PSCs with PEDOT:PSS. The significant enhancement of PCEs of PSCs can be attributed to the fact that ozone molecules can oxidize GO into CO 2 and leave highly conductive graphene particles. We suggest that this simple UV-ozone treatment can provide an efficient method for highly efficient GO hole extraction in high-performance PSCs.

  11. Facile fabrication of Ag3VO4/attapulgite composites for highly efficient visible light-driven photodegradation towards organic dyes and tetracycline hydrochloride

    Science.gov (United States)

    Luo, Yuting; Luo, Jie; Duan, Guorong; Liu, Xiaoheng

    2017-12-01

    An efficient one-dimensional attapulgite (ATP)-based photocatalyst, Ag3VO4/ATP nanocomposite, was fabricated by a facile deposition precipitation method with well-dispersed Ag3VO4 nanoparticles anchored on the surface of natural ATP fibers. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and UV-visible diffused reflectance spectroscopy (UV-vis DRS) were employed to investigate the morphologies, structure, and optical property of the prepared photocatalysts. The photocatalytic experiments indicated that the Ag3VO4/ATP nanocomposites exhibited enhanced visible light-driven photocatalytic activity towards the degradation of rhodamine B (RhB), methyl orange (MO), and tetracycline hydrochloride (TCH), of which the 20 wt% Ag3VO4/ATP sample showed superb photocatalytic performance. As demonstrated by N2 adsorption-desorption, photocurrent measurements, electrochemical impedance spectroscopy (EIS), and photoluminescence (PL) spectra analyses, the improved photocatalytic activity arose from the enlarged surface area, the facilitated charge transfer, and the suppressed recombination of photogenerated charge carriers in Ag3VO4/ATP system. Furthermore, radical scavengers trapping experiments and recycling tests were also conducted. This work gives a new insight into fabrication of highly efficient, stable, and cost-effective visible light-driven photocatalyst for practical application in wastewater treatment and environmental remediation.

  12. New class of photocatalytic materials and a novel principle for efficient water splitting under infrared and visible light: MgB2 as unexpected example.

    Science.gov (United States)

    Kravets, V G; Grigorenko, A N

    2015-11-30

    Water splitting is unanimously recognized as environment friendly, potentially low cost and renewable energy solution based on the future hydrogen economy. Especially appealing is photocatalytic water splitting whereby a suitably chosen catalyst dramatically improves efficiency of the hydrogen production driven by direct sunlight and allows it to happen even at zero driving potential. Here, we suggest a new class of stable photocatalysts and the corresponding principle for catalytic water splitting in which infrared and visible light play the main role in producing the photocurrent and hydrogen. The new class of catalysts - ionic or covalent binary metals with layered graphite-like structures - effectively absorb visible and infrared light facilitating the reaction of water splitting, suppress the inverse reaction of ion recombination by separating ions due to internal electric fields existing near alternating layers, provide the sites for ion trapping of both polarities, and finally deliver the electrons and holes required to generate hydrogen and oxygen gases. As an example, we demonstrate conversion efficiency of ~27% at bias voltage Vbias = 0.5V for magnesium diboride working as a catalyst for photoinduced water splitting. We discuss its advantages over some existing materials and propose the underlying mechanism of photocatalytic water splitting by binary layered metals.

  13. Efficiently Harvesting Sun Light for Silicon Solar Cells through Advanced Optical Couplers and A Radial p-n Junction Structure

    Directory of Open Access Journals (Sweden)

    Hsin-Cheng Lee

    2010-04-01

    Full Text Available Silicon-based solar cells (SCs promise to be an alternative energy source mainly due to: (1 a high efficiency-to-cost ratio, (2 the absence of environmental-degradation issues, and (3 great reliability. Transition from wafer-based to thin-film SC significantly reduces the cost of SCs, including the cost from the material itself and the fabrication process. However, as the thickness of the absorption (or the active layer decreases, the energy-conversion efficiency drops dramatically. As a consequence, we discuss here three techniques to increase the efficiency of silicon-based SCs: (1 photonic crystal (PC optical couplers and (2 plasmonic optical couplers to increase efficiency of light absorption in the SCs, and (3 a radial p-n junction structure, decomposing light absorption and diffusion path into two orthogonal directions. The detailed mechanisms and recent research progress regarding these techniques are discussed in this review article.

  14. Stable Carbon Isotope Composition (δ13C), Water Use Efficiency, and Biomass Productivity of Lycopersicon esculentum, Lycopersicon pennellii, and the F1 Hybrid

    Science.gov (United States)

    Martin, Bjorn; Thorstenson, Yvonne R.

    1988-01-01

    Three tomatoes, Lycopersicon esculentum Mill. cv UC82B, a droughttolerant wild related species, Lycopersicon pennellii (Cor.) D'Arcy, and their F1 hybrid, were grown in containers maintained at three levels of soil moisture. Season-long water use was obtained by summing over the season daily weight losses of each container corrected for soil evaporation. Plant biomass was determined by harvesting and weighing entire dried plants. Season-long water use efficiency (gram dry weight/kilogram H2O) was calculated by dividing the dry biomass by the season-long water use. The season-long water use efficiency was greatest in the wild parent, poorest in the domestic parent, and intermediate (but closer to the wild parent) in the F1 hybrid. Instantaneous water-use efficiency (micromole CO2/millimole H2O) determined by gas exchange measurements on individual leaves was poorly correlated with season-long water use efficiency. However, the relative abundance of stable carbon isotopes of leaf tissue samples was strongly correlated with the season-long water use efficiency. Also, the isotopic composition and the season-long water use efficiency of each genotype alone were strongly negatively correlated with plant dry weight when the dry weight varied as a function of soil moisture. PMID:16666269

  15. Stable carbon isotope composition (δ13C), water use efficiency, and biomass productivity of Lycopersicon esculentum, Lycopersicon pennellii, and the F1 hybrid

    International Nuclear Information System (INIS)

    Martin, B.; Thorstenson, Y.R.

    1988-01-01

    Three tomatoes, Lycopersicon esculentum Mill. cv UC82B, a droughttolerant wild related species, Lycopersicon pennellii (Cor.) D'Arcy, and their F 1 , hybrid, were grown in containers maintained at three levels of soil moisture. Season-long water use was obtained by summing over the season daily weight losses of each container corrected for soil evaporation. Plant biomass was determined by harvesting and weighing entire dried plants. Season-long water use efficiency (gram dry weight/kilogram H 2 O) was calculated by dividing the dry biomass by the season-long water use. The season-long water use efficiency was greatest in the wild parent, poorest in the domestic parent, and intermediate (but closer to the wild parent) in the F, hybrid. Instantaneous water-use efficiency (micromole CO 2 /millimole H 2 O) determined by gas exchange measurements on individual leaves was poorly correlated with season-long water use efficiency. However, the relative abundance of stable carbon isotopes of leaf tissue samples was strongly correlated with the season-long water use efficiency. Also, the isotopic composition and the season-long water use efficiency of each genotype alone were strongly negatively correlated with plant dry weight when the dry weight varied as a function of soil moisture. (author)

  16. Design of a Highly Stable, High-Conversion-Efficiency, Optical Parametric Chirped-Pulse Amplification System with Good Beam Quality

    International Nuclear Information System (INIS)

    Guardalben, M.J.; Keegan, J.; Waxer, L.J.; Bagnoud, V.; Begishev, I.A.; Puth, J.; Zuegel, J.D.

    2003-01-01

    OAK B204 An optical parametric chirped-pulse amplifier (OPCPA) design that provides 40% pump-to-signal conversion efficiency and over-500-mJ signal energy at 1054 nm for front-end injection into a Nd:glass amplifier chain is presented. This OPCPA system is currently being built as the prototype front end for the OMEGA EP (extended performance) laser system at the University of Rochester's Laboratory for Laser Energetics. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good output stability, and good beam quality are discussed. The dependence of OPCPA output on the pump beam's spatiotemporal shape and the relative size of seed and pump beams is described. This includes the effects of pump intensity modulation and pump-signal walk-off. The trade-off among efficiency, stability, and low output beam intensity modulation is discussed

  17. High-efficiency pyrene-based blue light emitting diodes: Aggregation suppression using a calixarene 3D-scaffold

    KAUST Repository

    Chan, Khaileok

    2012-01-01

    An efficient blue light emitting diode based on solution processable pyrene-1,3-alt-calix[4]arene is demonstrated, providing a record current efficiency of 10.5 cd A -1 in a simple non-doped OLED configuration. Complete suppression of pyrene aggregation in the solid state is achieved by controlling chromophore dispersion using the 1,3-alt-calix[4]arene scaffold. © 2012 The Royal Society of Chemistry.

  18. High-efficiency fluorescent organic light-emitting devices using sensitizing hosts with a small singlet-triplet exchange energy.

    Science.gov (United States)

    Zhang, Dongdong; Duan, Lian; Li, Chen; Li, Yilang; Li, Haoyuan; Zhang, Deqiang; Qiu, Yong

    2014-08-06

    Materials with small singlet-triplet splits (ΔEST s) are introduced as sensitizing hosts to excite fluorescent dopants, breaking the trade-off between small ΔEST and high radiative decay rates. A highly efficient orange-fluorescent organic light-emitting diode (OLED) is prepared, showing a maximum external quantum efficiency of 12.2%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Synergistic "ping-pong" energy transfer for efficient light activation in a chromophore-catalyst dyad.

    Science.gov (United States)

    Quaranta, Annamaria; Charalambidis, Georgios; Herrero, Christian; Margiola, Sofia; Leibl, Winfried; Coutsolelos, Athanassios; Aukauloo, Ally

    2015-10-07

    The synthesis of a porphyrin-Ru(II) polypyridine complex where the porphyrin acts as a photoactive unit and the Ru(II) polypyridine as a catalytic precursor is described. Comparatively, the free base porphyrin was found to outperform the ruthenium based chromophore in the yield of light induced electron transfer. Mechanistic insights indicate the occurrence of a ping-pong energy transfer from the (1)LC excited state of the porphyrin chromophore to the (3)MCLT state of the catalyst and back to the (3)LC excited state of the porphyrin unit. The latter, triplet-triplet energy transfer back to the chromophore, efficiently competes with fast radiationless deactivation of the excited state at the catalyst site. The energy thus recovered by the chromophore allows improved yield of formation of the oxidized form of the chromophore and concomitantly of the oxidation of the catalytic unit by intramolecular charge transfer. The presented results are among the rare examples where a porphyrin chromophore is successfully used to drive an oxidative activation process where reductive processes prevail in the literature.

  20. Highly efficient photocatalytic hydrogen evolution from nickel quinolinethiolate complexes under visible light irradiation

    Science.gov (United States)

    Rao, Heng; Yu, Wen-Qian; Zheng, Hui-Qin; Bonin, Julien; Fan, Yao-Ting; Hou, Hong-Wei

    2016-08-01

    Earth-abundant metal complexes have emerged as promising surrogates of platinum for catalyzing the hydrogen evolution reaction (HER). In this study, we report the design and synthesis of two novel nickel quinolinethiolate complexes, namely [Ni(Hqt)2(4, 4‧-Z-2, 2‧-bpy)] (Hqt = 8-quinolinethiol, Z = sbnd H [1] or sbnd CH3 [2], bpy = bipyridine). An efficient three-component photocatalytic homogeneous system for hydrogen generation working under visible light irradiation was constructed by using the target complexes as catalysts, triethylamine (TEA) as sacrificial electron donor and xanthene dyes as photosensitizer. We obtain turnover numbers (TON, vs. catalyst) for H2 evolution of 5923/7634 under the optimal conditions with 5.0 × 10-6 M complex 1/2 respectively, 1.0 × 10-3 M fluorescein and 5% (v/v) TEA at pH 12.3 in EtOH/H2O (1:1, v/v) mixture after 8 h irradiation (λ > 420 nm). We discuss the mechanism of H2 evolution in the homogeneous photocatalytic system based on fluorescence spectrum and cyclic voltammetry data.

  1. Highly Efficient Blue Phosphorescent Organic Light-Emitting Diodes Employing a Host Material with Small Bandgap.

    Science.gov (United States)

    Zhang, Lei; Zhang, Ye-Xin; Hu, Yun; Shi, Xiao-Bo; Jiang, Zuo-Quan; Wang, Zhao-Kui; Liao, Liang-Sheng

    2016-06-29

    Blue phosphorescent organic light-emitting diode (PhOLED) with a high maximum external quantum efficiency (EQE) of 26.6% was achieved using a new material, 2,8-bis(9,9-dimethylacridin-10(9H)-yl)dibenzo[b,d]furan (DBF-DMS) with a small bandgap, as the host. The device with DBF-DMS showed improved performance compared with that with 1,3-di-9-carbazolylbenzene, which is ascribed to the enhancement in carrier injection and transporting abilities and material stability of DBF-DMS. A lifetime of more than 100 h (time to 50% of the initial luminance, 1000 cd/m(2) with an EQE of 19.6%) in the other DBF-DMS-based device is obtained by further utilizing better device structure. This is a report indicating that host material with a small bandgap like DBF-DMS can be successfully utilized toward blue PhOLEDs with high performance.

  2. Efficient double-emitting layer inverted organic light-emitting devices with different spacer layers

    Science.gov (United States)

    Nie, Qu-yang; Zhang, Fang-hui

    2017-09-01

    Double-emitting layer inverted organic light-emitting devices (IOLEDs) with different spacer layers were investigated, where 2,20,7,70-tetrakis(carbazol-9-yl)-9,9-spirobifluorene (CBP), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 4,40,400-tris(N-carbazolyl)-triphenylamine (TCTA) were used as spacer layers, respectively, and GIr1 and R-4b were used as green and red guest phosphorescent materials, respectively. The results show that the device with BCP spacer layer has the best performance. The maximum current efficiency of the BCP spacer layer device reaches up to 24.15 cd·A-1 when the current density is 3.99 mA·cm-2, which is 1.23 times bigger than that of the CBP spacer layer device. The performance is better than that of corresponding conventional device observably. The color coordinate of the device with BCP spacer layer only changes from (0.625 1, 0.368 0) to (0.599 5, 0.392 8) when the driving voltage increases from 6 V to 10 V, so it shows good stability in color coordinate, which is due to the adoption of the co-doping evaporation method for cladding luminous layer and the effective restriction of spacer layer to carriers in emitting layer.

  3. Large Differences in Terrestrial Vegetation Production Derived from Satellite-Based Light Use Efficiency Models

    Directory of Open Access Journals (Sweden)

    Wenwen Cai

    2014-09-01

    Full Text Available Terrestrial gross primary production (GPP is the largest global CO2 flux and determines other ecosystem carbon cycle variables. Light use efficiency (LUE models may have the most potential to adequately address the spatial and temporal dynamics of GPP, but recent studies have shown large model differences in GPP simulations. In this study, we investigated the GPP differences in the spatial and temporal patterns derived from seven widely used LUE models at the global scale. The result shows that the global annual GPP estimates over the period 2000–2010 varied from 95.10 to 139.71 Pg C∙yr−1 among models. The spatial and temporal variation of global GPP differs substantially between models, due to different model structures and dominant environmental drivers. In almost all models, water availability dominates the interannual variability of GPP over large vegetated areas. Solar radiation and air temperature are not the primary controlling factors for interannual variability of global GPP estimates for most models. The disagreement among the current LUE models highlights the need for further model improvement to quantify the global carbon cycle.

  4. Improved efficiency in blue phosphorescent organic light-emitting diodes by the stepwise doping structure

    Science.gov (United States)

    Yang, Liping; Wang, Xiaoping; Kou, Zhiqi; Ji, Changyan

    2017-04-01

    The electro-optical properties of the blue phosphorescent organic light-emitting diodes (PHOLEDs) can be affected by the stepwise doping structure in the emitting layer (EML). A series of multi-EML devices with different doping concentration of blue dopant (FIrpic) are fabricated. The effect of the stepwise doping structure close to the electron transport layer is more obvious than that close to the hole transport layer. When the doping concentration increases gradually from the hole injection side to the electron injection side, the maximum values of the luminance, current and power efficiency can reach to 9745 cd/m2 (at 9 V), 32.0 cd/A and 25.1 lm/W in the device with the asymmetric tri-EML structure, which is improved by about 10% compared with that in the bi-EML device. When the number of the EML is four, the performance of the device becomes worse because of the interface effect resulting from different concentration of dopant.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-10-15

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

  6. Consumer preferences and willingness to pay for compact fluorescent lighting: Policy implications for energy efficiency promotion in Saint Lucia

    International Nuclear Information System (INIS)

    Reynolds, Travis; Kolodinsky, Jane; Murray, Byron

    2012-01-01

    This article examines consumer willingness to pay for energy-saving compact fluorescent light bulbs using the results of a stated preferences study conducted in the Caribbean island nation of Saint Lucia. Geographic location, low income status, and age are found to affect willingness-to-pay for compact fluorescent lighting, while higher income status and other demographic variables appear to have minimal or no significant impacts. Energy efficiency knowledge is associated with increased willingness-to-pay for energy-efficient bulbs and with increased use of compact fluorescent lighting. Contrary to theoretical expectations, past purchase of compact fluorescent bulbs is found to have no impact on self-reported willingness to pay. We hypothesize that this null result is due to the recent emergence of low-cost, low-quality compact fluorescent bulbs in the Saint Lucian lighting market, which may be negatively influencing consumers' preferences and expectations regarding energy-efficient lighting. Findings support the argument that government-sponsored education and subsidy programs will likely result in increased use of energy-saving technologies in Saint Lucia. But such behavioral changes may not be sustained in the long run unless low quality bulbs – the “lemons” of the compact fluorescent lighting market – can be clearly identified by consumers. - Highlights: ▶ We model how knowledge, attitudes, and past purchase affect CFL adoption. ▶ Saint Lucian consumers have some knowledge of and favorable attitudes toward CFLs. ▶ Energy efficiency knowledge increases stated willingness-to-pay (WTP) for CFLs. ▶ Past purchase does not increase WTP; low-quality ‘lemons’ may influence consumers. ▶ Policy can lower consumer risks in lighting markets where low quality bulbs exist.

  7. Highly efficient InGaN-based light emitting devices grown on nanoscale patterned substrates by MOCVD

    Science.gov (United States)

    Lin, Chien-Chung; Chiu, Ching-Hsueh; Huang, H. W.; Chang, Shih-Pang; Kuo, Hao-Chung; Chang, Chun-Yen

    2011-12-01

    Highly efficient InGaN-base light emitting diodes are crucial for next generation solid state lighting. However, drawbacks in substrate materials such as lattice and thermal expansion coefficient mismatches hold back the lamination efficiency improvement. In the past, patterned sapphire sustrate (PSS) has been proven to be effect to enhance the LED's performance. In this work, we reviewed several promising nano-scale technologies which successfully increase the output of LED through better material quality and light extraction. First, we presented a study of high-performance blue emission GaN LEDs using GaN nanopillars (NPs). It exhibits smaller blue shift in electroluminescent peak wavelength and great enhancement of the light output (70% at 20 mA) compared with the conventional LEDs. Secondly, GaN based LEDs with nano-hole patterned sapphire (NHPSS) by nano-imprint lithography are fabricated structure grown on sapphire substrate. At an injection current of 20mA, the LED with NHPSS increased the light output power of LEDs by 1.33 times, and the wall-plug efficiency is 30% higher at 20mA indicating that it had larger light extraction efficiency (LEE). Finally, we fabricated the high performance electrical pumping GaN-based semipolar {10-11} nano-pyramid LEDs on c-plane sapphire substrate by selective area epitaxy (SAE). The emission wavelength only blue-shifted about 5nm as we increased the forward current from 40 to 200mA, and the quantum confine stark effect (QCSE) had been remarkably suppressed on semipolar surface at long emission wavelength region. These results manifest the promising role of novel nanotechnology in the future III-nitride light emitters.

  8. Guide for optimizing the effectiveness and the efficiency of roadway lighting.

    Science.gov (United States)

    2012-06-01

    The objective of the present project was to develop a simple guide for roadway lighting replacement : approaches using new light source technologies to maintain visibility for safety, while reducing energy use. : Several roadway types were evaluated:...

  9. Controlling shape anisotropy of hexagonal CdS for highly stable and efficient photocatalytic H2evolution and photoelectrochemical water splitting.

    Science.gov (United States)

    Ma, Yongjin; Liu, Yi; Bian, Yuan; Zhu, Anquan; Yang, Yang; Pan, Jun

    2018-05-15

    Photocorrosion and low solar conversion efficiency hindered widely applications of CdS in photocatalytic (PC) H 2 evolution and photoelectrochemical (PEC) water splitting. Hence, this work reports the shape anisotropy of hexagonal CdS possesses highly stable and efficient PC H 2 evolution and PEC water splitting by simply mixed diethylenetriamine (DETA) and deionized water (DIW) solvothermal. Here we demonstrate that the shape of hexagonal CdS plays an important role in their PC activity. The CdS-Nanorod yields optimal 5.4 mmol/g/h PC H 2 production and photocurrent density 2.63 mA/cm 2 at open circuit potential (OCP). The enhanced performance is attributed to the effective separation and transport of the photogenerated electron-hole pairs, which were verified by PL and transisent absorbance. Moreover, hexagonal CdS-Nanorod shows long-term PC H 2 production and highly stable photocurrent density. As compared with CdS-Nanosphere, the hexagonal CdS-Nanorod exhibits 27 times and 19.2 times in H 2 production and photocurrent density, respectively. What's more, STH efficiency of hexagonal CdS-Nanorod is 3.23% and an impressive applied bias photon-to-current efficiency (ABPE) is 2.63% at 0.134 V (vs. RHE). Temperature is also explored and reported. The possible mechanism of PC H 2 evolution and PEC water spiltting are proposed for CdS-Nanorod. This work may provide a promising strategy to fabricate efficient PC and PEC systems for solar-to-fuel energy conversion. Copyright © 2018 Elsevier Inc. All rights reserved.

  10. Industrial energy efficiency in light of climate change negotiations: Comparing major developing countries and the U.S

    International Nuclear Information System (INIS)

    Phylipsen, D.; Price, L.; Worrell, E.; Blok, K.

    1999-01-01

    In light of the commitments accepted within the Framework Convention on Climate Change there is an increasing need for useful information on energy consumption and energy efficiency. Governments can use this information in designing policies to reduce greenhouse gas emissions and prioritizing energy savings options. International comparison of energy efficiency can provide a benchmark against which a country's performance can be measured and policies can be evaluated. A methodology for international comparisons of industrial energy efficiency was developed by the International Network on Energy Demand analysis in the Industrial Sector. In this paper this methodology is used to analyze the energy efficiency of two energy-intensive industries in major developing countries. Energy consumption trends are shown for the steel and cement industry and an analysis is made of technologies used. In light of the Byrd-Hagel resolution, which states that the US will not ratify any climate treaty unless it also mandates commitments to limit greenhouse gas emissions for developing countries, the energy efficiency in the two sectors is compared to that of the US. The analysis shows that in the iron and steel sector South Korea and Brazil are more energy-efficient than the US, while Mexico has achieved a comparable energy efficiency level in recent years. For cement, South Korea, Brazil and Mexico are the most efficient countries analyzed. In recent years, China, and especially, India appear to have achieved energy efficiency levels, more or less comparable to that of the US. In light of data constraints, however, further analysis is required

  11. Deprotonation of g-C3N4 with Na ions for efficient nonsacrificial water splitting under visible light

    DEFF Research Database (Denmark)

    Guo, Feng; Chen, Jingling; Zhang, Minwei

    2016-01-01

    Developing a photocatalyst with the necessary characteristics of being cheap, efficient and robust for visible-light-driven water splitting remains a serious challenge within the photocatalysis field. Herein, an effective strategy, deprotonating g-C3N4 with Na ions from low-cost precursors...

  12. Efficient generation of continuous-wave yellow-orange light using sum-frequency in periodically poled KTP

    DEFF Research Database (Denmark)

    Janousek, Jiri; Johansson, Sandra; Tidemand-Lichtenberg, Peter

    We present highly efficient sum-frequency generation between two CW 1064 and 1342 nm laser lines of two Nd:YVO4 lasers using periodically poled KTP. This is an all solid-state light source in the yellow-orange spectral range....

  13. A statistical light use efficiency model explains 85% variations in global GPP

    Science.gov (United States)

    Jiang, C.; Ryu, Y.

    2016-12-01

    Photosynthesis is a complicated process whose modeling requires different levels of assumptions, simplification, and parameterization. Among models, light use efficiency (LUE) model is highly compact but powerful in monitoring gross primary production (GPP) from satellite data. Most of LUE models adopt a multiplicative from of maximum LUE, absorbed photosynthetically active radiation (APAR), and temperature and water stress functions. However, maximum LUE is a fitting parameter with large spatial variations, but most studies only use several biome dependent constants. In addition, stress functions are empirical and arbitrary in literatures. Moreover, meteorological data used are usually coarse-resolution, e.g., 1°, which could cause large errors. Finally, sunlit and shade canopy have completely different light responses but little considered. Targeting these issues, we derived a new statistical LUE model from a process-based and satellite-driven model, the Breathing Earth System Simulator (BESS). We have already derived a set of global radiation (5-km resolution), carbon and water fluxes (1-km resolution) products from 2000 to 2015 from BESS. By exploring these datasets, we found strong correlation between APAR and GPP for sunlit (R2=0.84) and shade (R2=0.96) canopy, respectively. A simple model, only driven by sunlit and shade APAR, was thus built based on linear relationships. The slopes of the linear function act as effective LUE of global ecosystem, with values of 0.0232 and 0.0128 umol C/umol quanta for sunlit and shade canopy, respectively. When compared with MPI-BGC GPP products, a global proxy of FLUXNET data, BESS-LUE achieved an overall accuracy of R2 = 0.85, whereas original BESS was R2 = 0.83 and MODIS GPP product was R2 = 0.76. We investigated spatiotemporal variations of the effective LUE. Spatially, the ratio of sunlit to shade values ranged from 0.1 (wet tropic) to 4.5 (dry inland). By using maps of sunlit and shade effective LUE the accuracy of

  14. Efficient white phosphorescent organic light-emitting diodes consisting of orange ultrathin and blue mixed host emission layers

    Science.gov (United States)

    Sheng, Ren; Zuo, Liangmei; Xue, Kaiwen; Duan, Yu; Chen, Ping; Cheng, Gang; Zhao, Yi

    2016-08-01

    We have successfully demonstrated highly efficient white phosphorescent organic light-emitting diodes (OLEDs) by inserting an ultrathin non-doped orange layer within blue mixed host emission layer. The key feature of the novel device is the employment of blue mixed host and orange ultrathin layers, resulting in an extended recombination region and more balanced charge carrier. The maximum efficiencies of 33.8 lm W-1 and 32.2 cd A-1 are obtained. Moreover, the resulting white device achieves a slight efficiency roll-off and a high luminance at low operating voltage. Our versatile concept suggests a promising simple method to achieve high performance white OLEDs.

  15. Efficient interfacing of light and surface plasmon polaritons for quantum optics applications

    DEFF Research Database (Denmark)

    Eran, Kot

    light and quantum emitters proves a difficult task. Current days solutions range from cavities, atomic ensembles, photonic band gaps structures, ion traps and optical latices are all being improved and studied but none has yet to emerge as superior. Recently, another proposal for such a strong coupling......The research of light and matter interactions is the most fascinating and powerful tool in advancing our understanding of both atomic and light physics. From the pioneering work of Niels Bohr in devising a model for the atom to recent research in manipulation of single atoms, light matter...... system has been put forward. By exploiting the strong confinement of light in a surface plasmon mode, a cavity-free, broadband tool can be designed to engineer the light-emitter interaction in the vicinity of metallic nano-structures. These surface plasmons, hybrid waves of light and electronic...

  16. A Review on Experimental Measurements for Understanding Efficiency Droop in InGaN-Based Light-Emitting Diodes

    Directory of Open Access Journals (Sweden)

    Lai Wang

    2017-10-01

    Full Text Available Efficiency droop in GaN-based light emitting diodes (LEDs under high injection current density perplexes the development of high-power solid-state lighting. Although the relevant study has lasted for about 10 years, its mechanism is still not thoroughly clear, and consequently its solution is also unsatisfactory up to now. Some emerging applications, e.g., high-speed visible light communication, requiring LED working under extremely high current density, makes the influence of efficiency droop become more serious. This paper reviews the experimental measurements on LED to explain the origins of droop in recent years, especially some new results reported after 2013. Particularly, the carrier lifetime of LED is analyzed intensively and its effects on LED droop behaviors are uncovered. Finally, possible solutions to overcome LED droop are discussed.

  17. Photocatalytic Bactericidal Efficiency of Ag Doped TiO2/Fe3O4 on Fish Pathogens under Visible Light

    Directory of Open Access Journals (Sweden)

    Ekkachai Kanchanatip

    2014-01-01

    Full Text Available This research evaluates photocatalytic bactericidal efficiencies of Ag-TiO2/Fe3O4 in visible light using target pollutants that include Aeromonas hydrophila, Edwardsiella tarda, and Photobacterium damselae subsp. piscicida. The investigation started with Ag-TiO2/Fe3O4 synthesis and calcination followed by a series of product tests that include the examination of crystallite phase, light absorption, element composition morphology, and magnetic properties. The results of the experiment indicate that Ag and Fe3O4 significantly enhanced the light absorption capacity of TiO2 in the entire visible light range. The Ag-TiO2/Fe3O4 prepared in this study displays significantly enhanced visible light absorption and narrowed band gap energy. The magnetic property of Ag-TiO2/Fe3O4 made it easy for retrieval using a permanent magnet bar. The photocatalytic activity of Ag-TiO2/Fe3O4 remains above 85% after three application cycles, which indicates high and favorable efficiency in bactericidal evaluation. The experiments have proved that the Ag-TiO2/Fe3O4 magnetic photocatalyst is a promising photocatalyst for antibacterial application under visible light.

  18. Effect of Magnesium on Gas Exchange and Photosynthetic Efficiency of Coffee Plants Grown under Different Light Levels

    Directory of Open Access Journals (Sweden)

    Kaio Gonçalves de Lima Dias

    2017-09-01

    Full Text Available The aim of the present study was to investigate the effects of magnesium on the gas exchange and photosynthetic efficiency of Coffee seedlings grown in nutrient solution under different light levels. The experiment was conducted under controlled conditions in growth chambers and nutrient solution at the Department of Plant Pathology of the Federal University of Lavras. The treatments consisted of five different Mg concentrations (0, 48, 96, 192 and 384 mg·L−1 and four light levels (80, 160, 240 and 320 µmol photon m−2·s−1. Both the Mg concentration and light levels affected gas exchange in the coffee plants. Photosynthesis increased linearly with the increasing light, indicating that the light levels tested were low for this crop. The highest CO2 assimilation rate, lowest transpiration, and highest water use efficiency were observed with 250 mg·Mg·L−1, indicating that this concentration was the optimal Mg supply for the tested light levels.

  19. Response of gross ecosystem productivity, light use efficiency, and water use efficiency of Mongolian steppe to seasonal variations in soil moisture

    Science.gov (United States)

    Li, Sheng-Gong; Eugster, Werner; Asanuma, Jun; Kotani, Ayumi; Davaa, Gombo; Oyunbaatar, Dambaravjaa; Sugita, Michiaki

    2008-03-01

    The examination of vegetation productivity and use of light and water resources is important for understanding the carbon and water cycles in semiarid and arid environments. We made continuous measurements of carbon dioxide and water vapor fluxes over an arid steppe ecosystem in Mongolia by using the eddy covariance (EC) technique. These measurements allow an examination of EC-estimated gross ecosystem productivity (GEP), light use efficiency (LUE), and water use efficiency (WUE) of the steppe. Daily variations of GEP, LUE, and WUE were associated with daily variations of incident photosynthetically active radiation (PAR), ambient temperature (Ta), and vapor pressure deficit (VPD). The magnitudes of these variations were also dependent on canopy development. On the daily basis, GEP linearly correlated with evapotranspiration rate and PAR. LUE correlated positively with leaf area index, Ta, and soil moisture availability but negatively with the surface reflectivity for short-wave solar radiation. Throughout the growing season, both GEP and LUE responded strongly to precipitation-fed soil moisture in the top 20 cm of the soil. An examination of the responses of LUE and WUE to PAR under different soil moisture conditions shows that when soil water availability exceeded VPD, the steppe was most efficient in light use, whereas it was less efficient in water use. The multivariate analysis of variance also suggests that soil moisture availability, especially water status in the upper 20-cm soil layer with dense distribution of grass roots, is the most significant factor that governs GEP, WUE, and LUE. This study provides a preliminary assessment of the use of available water and light by the Mongolian arid steppe ecosystems under seasonally varying soil moisture conditions. A better understanding of these functional responses is required to predict how climate change may affect arid steppe ecosystems.

  20. Light

    CERN Document Server

    Robertson, William C

    2003-01-01

    Why is left right and right left in the mirror? Baffled by the basics of reflection and refraction? Wondering just how the eye works? If you have trouble teaching concepts about light that you don t fully grasp yourself, get help from a book that s both scientifically accurate and entertaining with Light. By combining clear explanations, clever drawings, and activities that use easy-to-find materials, this book covers what science teachers and parents need to know to teach about light with confidence. It uses ray, wave, and particle models of light to explain the basics of reflection and refraction, optical instruments, polarization of light, and interference and diffraction. There s also an entire chapter on how the eye works. Each chapter ends with a Summary and Applications section that reinforces concepts with everyday examples. Whether you need a deeper understanding of how light bends or a good explanation of why the sky is blue, you ll find Light more illuminating and accessible than a college textbook...

  1. Highly efficient and heavily-doped organic light-emitting devices based on an orange phosphorescent iridium complex

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Shunliang; Wang, Qi [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China); Li, Ming [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Lu, Zhiyun, E-mail: luzhiyun@scu.edu.cn [College of Chemistry, Sichuan University, Chengdu, 610064 (China); Yu, Junsheng, E-mail: jsyu@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

    2014-10-15

    Heavily doped and highly efficient phosphorescent organic light-emitting devices (PhOLEDs) had been fabricated by utilizing an orange iridium complex, bis[2-(3′,5′-di-tert-butylbiphenyl-4-yl)benzothiazolato-N,C{sup 2'}]iridium(III) (acetylacetonate) [(tbpbt){sub 2}Ir(acac)], as a phosphor. When the doping concentration of [(tbpbt){sub 2}Ir(acac)] reached as high as 15 wt%, the PhOLEDs exhibited a power efficiency, current efficiency, and external quantum efficiency of 24.5 lm/W, 32.1 cd/A, 15.7%, respectively, implying a promising quenching-resistant characteristics of this novel phosphor. Furthermore, the efficient white PhOLEDs had been obtained by employing (tbpbt){sub 2}Ir(acac) as a self-host orange emitter, indicating that (tbpbt){sub 2}Ir(acac) could serve as a promising phosphor to fabricate white organic light-emitting devices with simplified manufacturing process. - Highlights: • Efficient phosphorescent devices were fabricated. • Optimized phosphor doping ratio reached as high as 15 wt%. • The results proved a promising quench-resistant property of the phosphor. • Efficient white devices based on this phosphor as self-host layer had been realized.

  2. Combined host–guest doping and host-free systems for high-efficiency white organic light-emitting devices

    International Nuclear Information System (INIS)

    Zhao Juan; Yu Junsheng; Liu Shengqiang; Jiang Yadong

    2012-01-01

    Highly efficient white organic light-emitting devices (WOLEDs) with a four-layer structure were realized by utilizing phosphorescent blue and yellow emitters. The key concept of device construction is to combine host–guest doping system of the blue emitting layer (EML) and the host-free system of yellow EML. Two kinds of WOLEDs incorporated with distinct host materials, namely N,N'-dicarbazolyl-3,5-benzene (mCP) and p-bis(triphenylsilyly)benzene (UGH2), were fabricated. Without using light out-coupling technology, a maximum current efficiency (η C ) of 58.8 cd/A and a maximum external quantum efficiency (η EQE ) of 18.77% were obtained for the mCP-based WOLED; while a maximum η C of 65.3 cd/A and a maximum η EQE of 19.04% were achieved for the UGH2-based WOLED. Meanwhile, both WOLEDs presented higher performance than that of conventionally full-doping WOLEDs. Furthermore, systematic studies of the high-efficiency WOLEDs were progressed. - Highlights: ► Efficient WOLEDs by combining two systems. ► Host–guest doping system for blue emitting layer. ► Host-free system for yellow emitting layer. ► Maximum current efficiency of 65.3 cd/A and external quantum efficiency of 19.04%.

  3. Nonuniform Effect of Carrier Separation Efficiency and Light Absorption in Type-II Perovskite Nanowire Solar Cells.

    Science.gov (United States)

    Wang, Weiping; He, Jialun; Cao, Yiyan; Kong, Lijing; Zheng, Xuanli; Wu, Yaping; Chen, Xiaohong; Li, Shuping; Wu, Zhiming; Kang, Junyong

    2017-12-01

    Coaxial structures exhibit great potential for the application of high-efficiency solar cells due to the novel mechanism of radial charge separation. Here, we intensively investigate the nonuniform effect of carrier separation efficiency (CSE) and light absorption in perovskite-based type-II coaxial nanowire solar cells (ZnO/CH 3 NH 3 PbI 3 ). Results show that the CSE rapidly decreases along the radial direction in the shell, and the value at the outer side becomes extremely low for the thick shell. Besides, the position of the main light absorption gradually moves to the outer side with the increase of the shell thickness. As a result, the external quantum efficiency shows a positional dependence with a maximal value close to the border of the nanowire. Eventually, in our case, it is found that the maximal power conversion efficiency of the solar cells reduces from 19.5 to 17.9% under the effect of the nonuniformity of CSE and light absorption. This work provides a basis for the design of high-efficiency solar cells, especially type-II nanowire solar cells.

  4. Nonuniform Effect of Carrier Separation Efficiency and Light Absorption in Type-II Perovskite Nanowire Solar Cells

    Science.gov (United States)

    Wang, Weiping; He, Jialun; Cao, Yiyan; Kong, Lijing; Zheng, Xuanli; Wu, Yaping; Chen, Xiaohong; Li, Shuping; Wu, Zhiming; Kang, Junyong

    2017-03-01

    Coaxial structures exhibit great potential for the application of high-efficiency solar cells due to the novel mechanism of radial charge separation. Here, we intensively investigate the nonuniform effect of carrier separation efficiency (CSE) and light absorption in perovskite-based type-II coaxial nanowire solar cells (ZnO/CH3NH3PbI3). Results show that the CSE rapidly decreases along the radial direction in the shell, and the value at the outer side becomes extremely low for the thick shell. Besides, the position of the main light absorption gradually moves to the outer side with the increase of the shell thickness. As a result, the external quantum efficiency shows a positional dependence with a maximal value close to the border of the nanowire. Eventually, in our case, it is found that the maximal power conversion efficiency of the solar cells reduces from 19.5 to 17.9% under the effect of the nonuniformity of CSE and light absorption. This work provides a basis for the design of high-efficiency solar cells, especially type-II nanowire solar cells.

  5. Temporal Variability of Canopy Light Use Efficiency and its Environmental Controls in a Subtropical Mangrove Wetland

    Science.gov (United States)

    Zhu, X.

    2016-12-01

    Mangrove wetlands play an important role in global carbon cycle due to their strong carbon sequestration resulting from high plant carbon assimilation and low soil respiration. However, temporal variability of carbon sequestration in mangrove wetlands is less understood since carbon processes of mangrove wetlands are influenced by many complicated and concurrent environmental controls including tidal activities, site climate and soil conditions. Canopy light use efficiency (LUE), is the most important plant physiological parameter that can be used to describe the temporal dynamics of canopy photosynthesis, and therefore a better characterization of temporal variability of canopy LUE will improve our understanding in mangrove photosynthesis and carbon balance. One of our aims is to study the temporal variability of canopy LUE and its environmental controls in a subtropical mangrove wetland. Half-hourly canopy LUE is derived from eddy covariance (EC) carbon flux and photosynthesis active radiation observations, and half-hourly environmental controls we measure include temperature, humidity, precipitation, radiation, tidal height, salinity, etc. Another aim is to explore the links between canopy LUE and spectral indices derived from near-surface tower-based remote sensing (normalized difference vegetation index, enhanced vegetation index, photochemical reflectance index, solar-induced chlorophyll fluorescence, etc.), and then identify potential quantitative relationships for developing remote sensing-based estimation methods of canopy LUE. At present, some instruments in our in-situ observation system have not yet been installed (planned in next months) and therefore we don't have enough measurements to support our analysis. However, a preliminary analysis of our historical EC and climate observations in past several years indicates that canopy LUE shows strong temporal variability and is greatly affected by environmental factors such as tidal activity. Detailed and

  6. High quantum efficiency in solution processed blue phosphorescent organic light-emitting diodes based on an asymmetric benzothienopyridine host

    Energy Technology Data Exchange (ETDEWEB)

    Yook, Kyoung Soo; Lee, Jun Yeob, E-mail: leej17@dankook.ac.kr

    2014-09-15

    Highly efficient blue phosphorescent organic light-emitting diodes were developed using a benzothienopyridine based host material with an asymmetric molecular structure. 3-(3-(9H-carbazol-9-yl)phenyl)benzothieno[2,3-b]pyridine (BTP1) was used as the asymmetric host material for the solution processed blue devices. The BTP1 host showed a smooth morphology with a surface roughness of 0.30 nm and high quantum efficiency of 14.5% in blue phosphorescent organic light-emitting diodes. - Highlights: • High quantum efficiency in solution processed blue devices. • Smooth film morphology with a low surface roughness. • Benzothienopyridine based asymmetric host material for solution process.

  7. Two-dimensional high efficiency thin-film silicon solar cells with a lateral light trapping architecture.

    Science.gov (United States)

    Fang, Jia; Liu, Bofei; Zhao, Ying; Zhang, Xiaodan

    2014-08-22

    Introducing light trapping structures into thin-film solar cells has the potential to enhance their solar energy harvesting as well as the performance of the cells; however, current strategies have been focused mainly on harvesting photons without considering the light re-escaping from cells in two-dimensional scales. The lateral out-coupled solar energy loss from the marginal areas of cells has reduced the electrical yield indeed. We therefore herein propose a lateral light trapping structure (LLTS) as a means of improving the light-harvesting capacity and performance of cells, achieving a 13.07% initial efficiency and greatly improved current output of a-Si:H single-junction solar cell based on this architecture. Given the unique transparency characteristics of thin-film solar cells, this proposed architecture has great potential for integration into the windows of buildings, microelectronics and other applications requiring transparent components.

  8. Solution-processable organic-inorganic hybrid hole injection layer for high efficiency phosphorescent organic light-emitting diodes.

    Science.gov (United States)

    Lee, Min Hsuan; Choi, Wing Hong; Zhu, Furong

    2016-03-21

    The presence of a solution-processed hybrid PSS-MoO3-based hole injection layer (HIL) promotes a good interfacial contact between the indium tin oxide anode and hole-transporting layer for efficient operation of organic light-emitting diodes (OLEDs). This work reveals that the use of the hybrid HIL benefits the performance of phosphorescent OLEDs in two ways: (1) to assist in efficient hole injection, thereby improving power efficiency of OLEDs, and (2) to improve electron-hole current balance and suppression of interfacial defects at the organic/anode interface. The combined effects result in the power efficiency of 89.2 lm/W and external quantum efficiency of 23.9% for phosphorescent green OLEDs. The solution-processed hybrid PSS-MoO3-based HIL is beneficial for application in solution-processed organic electronic devices.

  9. Light

    CERN Document Server

    Rivera, Andrea

    2017-01-01

    Light is all around us. Learn how it is used in art, technology, and engineering. Five easy-to-read chapters explain the science behind light, as well as its real-world applications. Vibrant, full-color photos, bolded glossary words, and a key stats section let readers zoom in even deeper. Aligned to Common Core Standards and correlated to state standards. Abdo Zoom is a division of ABDO.

  10. Power and spectrally efficient integrated high-speed LED drivers for visible light communication

    OpenAIRE

    Venugopalan Nair Jalajakumari, Aravind

    2018-01-01

    Recent trends in mobile broadband indicates that the available radio frequency (RF) spectrum will not be enough to support the data requirements of the immediate future. Visible light communication, which uses visible spectrum to transmit wirelessly could be a potential solution to the RF ’Spectrum Crunch’. Thus there is growing interest all over the world in this domain with support from both academia and industry. Visible light communication( VLC) systems make use of light em...

  11. Passivation of interstitial and vacancy mediated trap-states for efficient and stable triple-cation perovskite solar cells

    Science.gov (United States)

    Mahmud, Md Arafat; Elumalai, Naveen Kumar; Upama, Mushfika Baishakhi; Wang, Dian; Gonçales, Vinicius R.; Wright, Matthew; Xu, Cheng; Haque, Faiazul; Uddin, Ashraf

    2018-04-01

    The current work reports the concurrent passivation of interstitial and oxygen vacancy mediated defect states in low temperature processed ZnO electron transport layer (ETL) via Ultraviolet-Ozone (UVO) treatment for fabricating highly efficient (maximum efficiency: 16.70%), triple cation based MA0.57FA0.38Rb0.05PbI3 (MA: methyl ammonium, FA: formamidinium, Rb: rubidium) perovskite solar cell (PSC). Under UV exposure, ozone decomposes to free atomic oxygen and intercalates into the interstitial and oxygen vacancy induced defect sites in the ZnO lattice matrix, which contributes to suppressed trap-assisted recombination phenomena in perovskite device. UVO treatment also reduces the content of functional hydroxyl group on ZnO surface, that increases the inter-particle connectivity and grain size of perovskite film on UVO treated ZnO ETL. Owing to this, the perovskite film atop UVO treated ZnO film exhibits reduced micro-strain and dislocation density values, which contribute to the enhanced photovoltaic performance of PSC with modified ZnO ETL. The modified PSCs exhibit higher recombination resistance (RRec) ∼40% compared to pristine ZnO ETL based control devices. Adding to the merit, the UVO treated ZnO PSC also demonstrates superior device stability, retaining about 88% of its initial PCE in the course of a month-long, systematic degradation study.

  12. 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

    2016-01-01

    We investigated a graphene oxide (GO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT: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 PEDOT: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 PEDOT: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.

  13. Resource use efficiency of closed plant production system with artificial light: concept, estimation and application to plant factory.

    Science.gov (United States)

    Kozai, Toyoki

    2013-01-01

    Extensive research has recently been conducted on plant factory with artificial light, which is one type of closed plant production system (CPPS) consisting of a thermally insulated and airtight structure, a multi-tier system with lighting devices, air conditioners and fans, a CO2 supply unit, a nutrient solution supply unit, and an environment control unit. One of the research outcomes is the concept of resource use efficiency (RUE) of CPPS.This paper reviews the characteristics of the CPPS compared with those of the greenhouse, mainly from the viewpoint of RUE, which is defined as the ratio of the amount of the resource fixed or held in plants to the amount of the resource supplied to the CPPS.It is shown that the use efficiencies of water, CO2 and light energy are considerably higher in the CPPS than those in the greenhouse. On the other hand, there is much more room for improving the light and electric energy use efficiencies of CPPS. Challenging issues for CPPS and RUE are also discussed.

  14. Fabrication of Light Extraction Efficiency of Organic Light-Emitting Diodes with 3D Aspherical Microlens by Using Dry Etching Process

    Directory of Open Access Journals (Sweden)

    Y. C. Chen

    2013-01-01

    Full Text Available organic light-emitting diode (OLED can enable a greater artificial contrast ratio and viewing angle compared to liquid crystal display (LCD because OLED pixels directly emit light. There is a shortcoming that the internal quantum efficiency can reach values close to 100%, but about 80% light disperses because of the difference among the refractive indices of the substrate, anode, indium tin oxide (ITO film, and air. In this paper, three dimensions aspherical microlens arrays (3D A-MLAs with substrate modifications are developed to simulate the optical luminous field by using FRED software. This study modified parameters of 3D A-MLAs such as the diameter, fill-factor, aspect ratio, dry etching parameters, and electroforming rates of microlens to improve the extraction efficiency of the OLED. In dry etching, not only the aspect ratio with better extraction rate can be obtained by reactive ion etching (RIE dry etching, but also an undercutting phenomenon can be avoided. The dimensions of 3D A-MLAs can be accurately controlled in the electroforming process used to make a nickel-cobalt (Ni-Co metal mold to achieve the designed dimensions. According to the measured results, the average luminance efficacy of the OLEDs with 3D A-MLAs can be enhanced.

  15. Cationic Vacancy Defects in Iron Phosphide: A Promising Route toward Efficient and Stable Hydrogen Evolution by Electrochemical Water Splitting.

    Science.gov (United States)

    Kwong, Wai Ling; Gracia-Espino, Eduardo; Lee, Cheng Choo; Sandström, Robin; Wågberg, Thomas; Messinger, Johannes

    2017-11-23

    Engineering the electronic properties of transition metal phosphides has shown great effectiveness in improving their intrinsic catalytic activity for the hydrogen evolution reaction (HER) in water splitting applications. Herein, we report for the first time, the creation of Fe vacancies as an approach to modulate the electronic structure of iron phosphide (FeP). The Fe vacancies were produced by chemical leaching of Mg that was introduced into FeP as "sacrificial dopant". The obtained Fevacancy-rich FeP nanoparticulate films, which were deposited on Ti foil, show excellent HER activity compared to pristine FeP and Mg-doped FeP, achieving a current density of 10 mA cm -2 at overpotentials of 108 mV in 1 m KOH and 65 mV in 0.5 m H 2 SO 4 , with a near-100 % Faradaic efficiency. Our theoretical and experimental analyses reveal that the improved HER activity originates from the presence of Fe vacancies, which lead to a synergistic modulation of the structural and electronic properties that result in a near-optimal hydrogen adsorption free energy and enhanced proton trapping. The success in catalytic improvement through the introduction of cationic vacancy defects has not only demonstrated the potential of Fe-vacancy-rich FeP as highly efficient, earth abundant HER catalyst, but also opens up an exciting pathway for activating other promising catalysts for electrochemical water splitting. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  16. Energy Efficient Lighting in the Residences of Staff of the University ...

    African Journals Online (AJOL)

    kofimereku

    probably faster than overall electricity demand. One area in which consumption of electricity is prominent and in high demand is household lighting. General incandescent lamp and linear fluorescent lamp- types are most popular lighting fixtures in Ghana. However the low-priced, luminous and popular incandescent lamps ...

  17. Synthesis and characterization of a new efficient blue-light- emitting copolymer

    NARCIS (Netherlands)

    Hilberer, A; Brouwer, H.J; van der Scheer, B.J.; Wildeman, J.; Hadziioannou, G

    1995-01-01

    In this paper we present the synthesis, the characterization, and the use in light-emitting diodes of a new blue-light-emitting copolymer, poly[2,5,2'',5''-tetraoctyl-p-terphenyl-4,4''-ylenevinylene-p-phenylenevinylene]. This copolymer, obtained by a poly-Heck reaction, has a fully unsaturated

  18. Concerning the sound insulation of building elements made up of light concretes. [acoustic absorption efficiency calculations

    Science.gov (United States)

    Giurgiu, I. I.

    1974-01-01

    The sound insulating capacity of building elements made up of light concretes is considered. Analyzing differentially the behavior of light concrete building elements under the influence of incident acoustic energy and on the basis of experimental measurements, coefficients of correction are introduced into the basic formulas for calculating the sound insulating capacity for the 100-3,2000 Hz frequency band.

  19. Light, nutrients, and food-chain length constrain planktonic energy transfer efficiency across multiple trophic levels

    OpenAIRE

    Dickman, Elizabeth M.; Newell, Jennifer M.; González, María J.; Vanni, Michael J.

    2008-01-01

    The efficiency of energy transfer through food chains [food chain efficiency (FCE)] is an important ecosystem function. It has been hypothesized that FCE across multiple trophic levels is constrained by the efficiency at which herbivores use plant energy, which depends on plant nutritional quality. Furthermore, the number of trophic levels may also constrain FCE, because herbivores are less efficient in using plant production when they are constrained by carnivores. These hypotheses have not ...

  20. Flexible deep-ultraviolet light-emitting diodes for significant improvement of quantum efficiencies by external bending

    KAUST Repository

    Shervin, Shahab

    2018-01-26

    Deep ultraviolet (DUV) light at the wavelength range of 250‒280 nm (UVC spectrum) is essential for numerous applications such as sterilization, purification, sensing, and communication. III-nitride-based DUV light-emitting diodes (DUV LEDs), like other solid-state lighting sources, offer a great potential to replace the conventional gas-discharged lamps with short lifetimes and toxic-element-bearing nature. However, unlike visible LEDs, the DUV LEDs are still suffering from low quantum efficiencies (QEs) and low optical output powers. In this work, reported is a new route to improve QEs of AlGaN-based DUV LEDs using mechanical flexibility of recently developed bendable thin-film structures. Numerical studies show that electronic band structures of AlGaN heterostructures and resulting optical and electrical characteristics of the devices can be significantly modified by external bending through active control of piezoelectric polarization. Internal quantum efficiency (IQE) is enhanced higher than three times, when the DUV LEDs are moderately bent to induce in-plane compressive strain in the heterostructure. Furthermore, efficiency droop at high injection currents is mitigated and turn-on voltage of diodes decreases with the same bending condition. The concept of bendable DUV LEDs with a controlled external strain can provide a new path for high-output-power and high-efficiency devices.

  1. Improved efficiencies in organic light emitting diodes made with CdSe/ZnS quantum dots and a semiconducting polymer.

    Science.gov (United States)

    Lee, Chih-Wen; Yang, Sheng-Hsiung; Hsu, Chain-Shu; Meng, Hsin-Fei

    2009-03-01

    In this study, we report the fabrication and characterization of organic/inorganic hybrid polymer light emitting diodes (PLEDs) made with ZnS-capped CdSe core/shell type nanocrystals and a light-emitting polymer poly[2-phenyl-3-(9,9-dihexylfluoren-2-yl)-1,4-phenylene vinylene]-co-[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene]. The device using pristine polymer as active layer emitted yellow light with a maximum brightness of 3949 cd/m2 and maximum external quantum efficiency of 0.27 cd/A at 10 V. After blending with the CdSe/ZnS quantum dots (QDs), the device showed a much higher brightness of 8192 cd/m2 and external quantum efficiency of 1.27 cd/A at 7 V, while the driving voltage was lowered. The experimental results revealed that CdSe/ZnS QDs act as a hole-blocker in the devices. More efficient electron-hole recombination process inside polymer layer results in large improvement in luminescence and efficiency.

  2. Dual-Layer Nanostructured Flexible Thin-Film Amorphous Silicon Solar Cells with Enhanced Light Harvesting and Photoelectric Conversion Efficiency.

    Science.gov (United States)

    Lin, Yinyue; Xu, Zhen; Yu, Dongliang; Lu, Linfeng; Yin, Min; Tavakoli, Mohammad Mahdi; Chen, Xiaoyuan; Hao, Yuying; Fan, Zhiyong; Cui, Yanxia; Li, Dongdong

    2016-05-04

    Three-dimensional (3-D) structures have triggered tremendous interest for thin-film solar cells since they can dramatically reduce the material usage and incident light reflection. However, the high aspect ratio feature of some 3-D structures leads to deterioration of internal electric field and carrier collection capability, which reduces device power conversion efficiency (PCE). Here, we report high performance flexible thin-film amorphous silicon solar cells with a unique and effective light trapping scheme. In this device structure, a polymer nanopillar membrane is attached on top of a device, which benefits broadband and omnidirectional performances, and a 3-D nanostructure with shallow dent arrays underneath serves as a back reflector on flexible titanium (Ti) foil resulting in an increased optical path length by exciting hybrid optical modes. The efficient light management results in 42.7% and 41.7% remarkable improvements of short-circuit current density and overall efficiency, respectively. Meanwhile, an excellent flexibility has been achieved as PCE remains 97.6% of the initial efficiency even after 10 000 bending cycles. This unique device structure can also be duplicated for other flexible photovoltaic devices based on different active materials such as CdTe, Cu(In,Ga)Se2 (CIGS), organohalide lead perovskites, and so forth.

  3. Stable anatase TiO2 coating on quartz fibers by atomic layer deposition for photoactive light-scattering in dye-sensitized solar cells

    Science.gov (United States)

    Kim, Do Han; Koo, Hyung-Jun; Jur, Jesse S.; Woodroof, Mariah; Kalanyan, Berç; Lee, Kyoungmi; Devine, Christina K.; Parsons, Gregory N.

    2012-07-01

    Quartz fibers provide a unique high surface-area substrate suitable for conformal coating using atomic layer deposition (ALD), and are compatible with high temperature annealing. This paper shows that the quartz fiber composition stabilizes ALD TiO2 in the anatase phase through TiO2-SiO2 interface formation, even after annealing at 1050 °C. When integrated into a dye-sensitized solar cell, the TiO2-coated quartz fiber mat improves light scattering performance. Results also confirm that annealing at high temperature is necessary for better photoactivity of ALD TiO2, which highlights the significance of quartz fibers as a substrate. The ALD TiO2 coating on quartz fibers also boosts dye adsorption and photocurrent response, pushing the overall efficiency of the dye-cells from 6.5 to 7.4%. The mechanisms for improved cell performance are confirmed using wavelength-dependent incident photon to current efficiency and diffuse light scattering results. The combination of ALD and thermal processing on quartz fibers may enable other device structures for energy conversion and catalytic reaction applications.

  4. Stable anatase TiO₂ coating on quartz fibers by atomic layer deposition for photoactive light-scattering in dye-sensitized solar cells.

    Science.gov (United States)

    Kim, Do Han; Koo, Hyung-Jun; Jur, Jesse S; Woodroof, Mariah; Kalanyan, Berç; Lee, Kyoungmi; Devine, Christina K; Parsons, Gregory N

    2012-08-07

    Quartz fibers provide a unique high surface-area substrate suitable for conformal coating using atomic layer deposition (ALD), and are compatible with high temperature annealing. This paper shows that the quartz fiber composition stabilizes ALD TiO(2) in the anatase phase through TiO(2)-SiO(2) interface formation, even after annealing at 1050 °C. When integrated into a dye-sensitized solar cell, the TiO(2)-coated quartz fiber mat improves light scattering performance. Results also confirm that annealing at high temperature is necessary for better photoactivity of ALD TiO(2), which highlights the significance of quartz fibers as a substrate. The ALD TiO(2) coating on quartz fibers also boosts dye adsorption and photocurrent response, pushing the overall efficiency of the dye-cells from 6.5 to 7.4%. The mechanisms for improved cell performance are confirmed using wavelength-dependent incident photon to current efficiency and diffuse light scattering results. The combination of ALD and thermal processing on quartz fibers may enable other device structures for energy conversion and catalytic reaction applications.

  5. Graphitic carbon nitride (g-C3N4)-Pt-TiO2 nanocomposite as an efficient photocatalyst for hydrogen production under visible light irradiation.

    Science.gov (United States)

    Chai, Bo; Peng, Tianyou; Mao, Jing; Li, Kan; Zan, Ling

    2012-12-28

    Porous graphitic carbon nitride (g-C(3)N(4)) was prepared by a simple pyrolysis of urea, and then a g-C(3)N(4)-Pt-TiO(2) nanocomposite was fabricated via a facile chemical adsorption followed by a calcination process. The obtained products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance absorption spectra, and electron microscopy. It is found that the visible-light-induced photocatalytic hydrogen evolution rate can be remarkably enhanced by coupling TiO(2) with the above g-C(3)N(4), and the g-C(3)N(4)-Pt-TiO(2) composite with a mass ratio of 70 : 30 has the maximum photoactivity and excellent photostability for hydrogen production under visible-light irradiation, and the stable photocurrent of g-C(3)N(4)-TiO(2) is about 1.5 times higher than that of the bare g-C(3)N(4). The above experimental results show that the photogenerated electrons of g-C(3)N(4) can directionally migrate to Pt-TiO(2) due to the close interfacial connections and the synergistic effect existing between Pt-TiO(2) and g-C(3)N(4) where photogenerated electrons and holes are efficiently separated in space, which is beneficial for retarding the charge recombination and improving the photoactivity.

  6. Light

    CERN Document Server

    Ditchburn, R W

    1963-01-01

    This classic study, available for the first time in paperback, clearly demonstrates how quantum theory is a natural development of wave theory, and how these two theories, once thought to be irreconcilable, together comprise a single valid theory of light. Aimed at students with an intermediate-level knowledge of physics, the book first offers a historical introduction to the subject, then covers topics such as wave theory, interference, diffraction, Huygens' Principle, Fermat's Principle, and the accuracy of optical measurements. Additional topics include the velocity of light, relativistic o

  7. Flexible deep-ultraviolet light-emitting diodes for significant improvement of quantum efficiencies by external bending

    Science.gov (United States)

    Shervin, Shahab; Oh, Seung Kyu; Park, Hyun Jung; Lee, Keon-Hwa; Asadirad, Mojtaba; Kim, Seung-Hwan; Kim, Jeomoh; Pouladi, Sara; Lee, Sung-Nam; Li, Xiaohang; Kwak, Joon Seop; Ryou, Jae-Hyun

    2018-03-01

    We report a new route to improve quantum efficiencies of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) using mechanical flexibility of recently developed bendable thin-film structures. Numerical studies show that electronic band structures of AlGaN heterostructures and resulting optical and electrical characteristics of the devices can be significantly modified by external bending through active control of piezoelectric polarization. Internal quantum efficiency is enhanced higher than three times, when the DUV LEDs are moderately bent with concave curvatures. Furthermore, an efficiency droop at high injection currents is mitigated and turn-on voltage of diodes decreases with the same bending condition. The concept of bendable DUV LEDs with a controlled external strain can provide a new path for high-output-power and high-efficiency devices.

  8. Highly efficient white phosphorescent organic light emitting diodes using a mixed host structure in deep blue emitting layer

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Chang Woo; Lee, Jun Yeob, E-mail: leej17@dankook.ac.kr

    2012-05-31

    Highly efficient phosphorescent white organic light-emitting diodes (PHWOLEDs) were developed using a deep blue phosphorescent emitter doped into a mixed host of high triplet energy host materials. The deep blue emitting layer was combined with a red:green emitting layer to fabricate PHWOLEDs. A high quantum efficiency of 19.5% with a color coordinate of (0.29,0.38) and 19.8% with a color coordinate of (0.39,0.46) were achieved in the PHWOLEDs using the mixed host emitting layer doped with a deep blue phosphorescent dopant. In addition, a low optimum doping concentration below 5% in red, green and blue dopants was realized in the PHWOLEDs. - Highlights: Black-Right-Pointing-Pointer High quantum efficiency in phosphorescent white device. Black-Right-Pointing-Pointer Mixed host structure for high power efficiency. Black-Right-Pointing-Pointer Low doping concentration below 5% in phosphorescent white device.

  9. Synchronization of Traffic Light Systems for Maximum Efficiency along Jalan Bukit Gambier, Penang, Malaysia

    Directory of Open Access Journals (Sweden)

    Ahmad Rafidi M.A.

    2014-01-01

    Full Text Available The synchronization of traffic light systems is one of the best solutions in order to avoid problematic traffic jams. Traffic timing is a major concern when it comes to traffic management. One of the common causes of traffic jams is because of nonsynchronized traffic light systems. Once a light turns green, traffic begins to move, but by the time the moving traffic reaches the next light, the signal is still red. This will disrupt the continuity of the traffic flow, especially for large main roads. The smooth flow of traffic on main routes is important to clear dense traffic in a given time. This study examined the density of vehicles on Jalan Bukit Gambier and also the traffic timing was documented in order to plan out proper re-timing for traffic lights along the studied road. The outcomes of this study support the hypothesis that retiming traffic lights to create a synchronized traffic light system for main roads will greatly improve traffic flow.

  10. Energy-efficient multicast traffic grooming strategy based on light-tree splitting for elastic optical networks

    Science.gov (United States)

    Liu, Huanlin; Yin, Yarui; Chen, Yong

    2017-07-01

    In order to address the problem of optimizing the spectrum resources and power consumption in elastic optical networks (EONs), we investigate the potential gains by jointly employing the light-tree splitting and traffic grooming for multicast requests. An energy-efficient multicast traffic grooming strategy based on light-tree splitting (EED-MTGS-LS) is proposed in this paper. Firstly, we design a traffic pre-processing mechanism to decide the multicast requests' routing order, which considers the request's bandwidth requirement and physical hops synthetically. Then, by dividing a light-tree to some sub-light-trees and grooming the request to these sub-light-trees, the light-tree sharing ratios of multicast requests can be improved. What's more, a priority scheduling vector is constructed, which aims to improve the success rate of spectrum assignment for grooming requests. Finally, a grooming strategy is designed to optimize the total power consumption by reducing the use of transponders and IP routers during routing. Simulation results show that the proposed strategy can significantly improve the spectrum utilization and save the power consumption.

  11. Research on natural lighting in reading spaces of university libraries in Jinan under the perspective of energy-efficiency

    Science.gov (United States)

    Yang, Zengzhang

    2017-11-01

    The natural lighting design in the reading spaces of university libraries not only influences physical and mental health of readers but also concerns the energy consumption of the libraries. The scientific and rational design of natural lighting is the key to the design of energy saving for physical environment of the reading space. The paper elaborates the present situation and existed problems of natural lighting in reading spaces of university libraries across Jinan region based on characteristics of light climate of Jinan region and concrete utilization of reading spaces in university libraries, and combining field measurement, survey, research and data analysis of reading spaces in Shandong Women’s University’s library. The paper, under the perspective of energy-efficiency, puts forward proposals to improve natural lighting in the reading spaces of university libraries from five aspects, such as adjustment of interior layout, optimization of outer windows design, employment of the reflector panel, design lighting windows on inner walls and utilization of adjustable sun shading facilities.

  12. Wirelessly powered submerged-light illuminated photobioreactors for efficient microalgae cultivation

    DEFF Research Database (Denmark)

    Murray, Alexandra Marie; Fotidis, Ioannis; Isenschmid, Alex

    2017-01-01

    A novel submerged-light photobioreactor (SL-PBR) with free-floating, wireless internal light sources powered by near-field resonant inductive coupling was investigated using a quick (Chlorella vulgaris) and a slow (Haematococcus pluvialis) growing microalgal species. During testing of the SL...... of the true yield. Interestingly, the SL-PBR provided more uniform light to the culture and had the ability to reduce the presence of dark zones and the effect of self-shading. Thus, the SL-PBR showed potential, if subsequent prototype designs address the technical challenges identified during this study....

  13. Stalled on the road to the market: Analysis of field experience with a project to promote lighting efficiency in India

    Energy Technology Data Exchange (ETDEWEB)

    Gadgil, A.J. [Lawrence Berkeley Lab., CA (United States); Sastry, M.A. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Alfred P. Sloan School of Management

    1992-10-01

    Several factors have been recognized in the energy policy literature as constraints that have retarded the wide-scale diffusion of high-efficiency appliances. In the developing countries, despite the apparent benefits of energy efficiency as an answer to problems in both environment and development arenas, the diffusion of highly-efficient appliances has been limited. Research suggests that these appliances appear more attractive from the collective or societal perspective than from any one actor`s viewpoint, and that current market and institutional arrangements do not automatically allow for an efficient sharing of costs and benefits. There is little incentive for individuals or organizations to promote increased energy efficiency on their own. This paper outlines the differing perspectives of consumers, utilities, and appliance manufacturers and describes the resulting barriers that appear in the Indian electric sector. An attempt to overcome these constraints, by means of a field experiment in Bombay, is then described. The project was to lease high-efficiency lamps to households where their use would reduce evening demand, thus saving or freeing up badly-needed peak power. A consortium of the north Bombay utility, a lighting manufacturer, and a local research institution was convened and jointly developed the Bombay Efficient Lighting Large-scale Experiment (or BELLE). The practical progress of BELLE and the lessons learned in attempting to get it off the ground are described. Participants learned that the purely economic constraints that BELLE was designed to address are not the only factors that can influence the diffusion of increased-efficiency appliances: the project encountered resistance from other organizations, leading to the refusal by a review committee of the consortium`s request for access to hard currency. The paper concludes with an assessment of factors that led to the proposal`s failure and some thoughts on next steps.

  14. Rague-Like FeP Nanocrystal Assembly on Carbon Cloth: An Exceptionally Efficient and Stable Cathode for Hydrogen Evolution

    KAUST Repository

    Yang, Xiulin

    2015-05-25

    There is a strong demand to replace expensive Pt catalysts with cheap metal sulfides or phosphides for hydrogen generation in water electrolysis. The earth-abundant Fe can be electroplated on carbon cloth (CC) to form high surface area rague-like FeOOH assembly. Subsequent gas phase phosphidation converts the FeOOH to FeP or FeP2 and the morphology of the crystal assembly is controlled by the phosphidation temperature. The FeP prepared at 250 oC presents lower crystallinity and those prepared at higher temperatures 400 oC and 500 oC possess higher crystallinity but lower surface area. The phosphidation at 300 oC produces nanocrystalline FeP and preserves the high-surface area morphology; thus it exhibits the highest HER efficiency in 0.5 M H2SO4; i.e. the required overpotential to reach 10 and 20 mA/cm2 is 34 and 43 mV respectively. These values are lowest among the reported non-precious metal phosphides on CC. The Tafel slope for the FeP prepared at 300 oC is around 29.2 mV/dec comparable to that of Pt/CC, indicating that the hydrogen evolution for our best FeP is limited by Tafel reaction (same as Pt). Importantly, the FeP/CC catalyst exhibits much better stability in a wide range working current density (up to 1 V/cm2), suggesting that it is a promising replacement of Pt for HER.

  15. NIR-Emitting Alloyed CdTeSe QDs and Organic Dye Assemblies: A Nontoxic, Stable, and Efficient FRET System

    Directory of Open Access Journals (Sweden)

    Doris E. Ramírez-Herrera

    2018-04-01

    Full Text Available In the present work, we synthesize Near Infrared (NIR-emitting alloyed mercaptopropionic acid (MPA-capped CdTeSe quantum dots (QDs in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable and have high quantum yields (QYs up to 84%. The alloyed MPA-capped CdTeSe QDs exhibit a red-shifted emission, whose color can be tuned between visible and NIR regions (608–750 nm by controlling the Te:Se molar ratio in the precursor mixtures and/or changing the time reaction. The MPA-capped QDs were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM, energy dispersive X-ray spectroscopy (EDS, and zeta potential measurements. Photostability studies were performed by irradiating the QDs with a high-power xenon lamp. The ternary MPA-CdTeSe QDs showed greater photostability than the corresponding binary MPA-CdTe QDs. We report the Förster resonance energy transfer (FRET from the MPA-capped CdTeSe QDs as energy donors and Cyanine5 NHS-ester (Cy5 dye as an energy acceptor with efficiency (E up to 95%. The distance between the QDs and dye (r, the Förster distance (R0, and the binding constant (K are reported. Additionally, cytocompatibility and cell internalization experiments conducted on human cancer cells (HeLa cells revealed that alloyed MPA-capped CdTeSe QDs are more cytocompatible than MPA-capped CdTe QDs and are capable of ordering homogeneously all over the cytoplasm, which allows their use as potential safe, green donors for biological FRET applications.

  16. 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.

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

    International Nuclear Information System (INIS)

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

    2007-01-01

    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

  18. Co-existence of LiI and KI in filler-free, quasi-solid-state electrolyte for efficient and stable dye-sensitized solar cell

    Science.gov (United States)

    Agarwala, S.; Thummalakunta, L. N. S. A.; Cook, C. A.; Peh, C. K. N.; Wong, A. S. W.; Ke, L.; Ho, G. W.

    A quasi-solid-state electrolyte employing a poly (ethylene oxide)/LiI system without a filler is evaluated. The electrolyte is optimized for various potassium iodide (KI) concentrations. The electrolyte containing 14.5 wt.% KI exhibits the highest conductivity (3.0 × 10 -3 S cm -1). An efficiency of 4.5% is achieved using this composition of the electrolyte. It is shown that the introduction of KI in a conventional PEO/I 2/LiI electrolyte system prevents the crystallization of the polymer matrix and enhances the ionic conductivity. The energy conversion efficiency of the device is further enhanced to 5.8% by incorporating a light-scattering layer.

  19. High-efficiency vertical GaN slab light-emitting diodes using self-coherent directional emitters.

    Science.gov (United States)

    Kim, Sun-Kyung; Lee, Jin Wook; Ee, Ho-Seok; Moon, Yong-Tae; Kwon, Soon-Hong; Kwon, Hoki; Park, Hong-Gyu

    2010-05-24

    We demonstrate a highly-efficient, large-area (1x1 mm2) GaN slab light-emitting diode using a vertically directional emitter produced from constructive interference. The vertical radiation can be coupled effectively into leaky modes from the beginning and thus a high-extraction efficiency can be expected with reduced material absorption. The far-field measurements show that the desired vertical emission profiles are obtained by varying the thickness of the dielectric layer between the emitter and bottom silver mirror. With the combination of a light extractor of a randomly textured surface, the output power was increased approximately 1.4 fold compared to a non-patterned device at a standard current of 350 mA without electrical degradation.

  20. The Microbial Efficiency-Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter?

    Science.gov (United States)

    Cotrufo, M Francesca; Wallenstein, Matthew D; Boot, Claudia M; Denef, Karolien; Paul, Eldor

    2013-04-01

    The decomposition and transformation of above- and below-ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been largely uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling and storage. We present the current understanding of the importance of microbial substrate use efficiency and C and N allocation in controlling the proportion of plant-derived C and N that is incorporated into SOM, and of soil matrix interactions in controlling SOM stabilization. We synthesize this understanding into the Microbial Efficiency-Matrix Stabilization (MEMS) framework. This framework leads to the hypothesis that labile plant constituents are the dominant source of microbial products, relative to input rates, because they are utilized more efficiently by microbes. These microbial products of decomposition would thus become the main precursors of stable SOM by promoting aggregation and through strong chemical bonding to the mineral soil matrix. © 2012 Blackwell Publishing Ltd.