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Light-emitting diodes

Xiao Jin, Chun Chang, Weifeng Zhao, Shujuan Huang, Xiaobing Gu, Qin Zhang, Feng Li, Yubao Zhang, Qinghua Li
The electron blocking layer (EBL) is important to balance the charge carrier transfer and achieve highly efficient quantum dot light-emitting diodes (QLEDs). Here we report the utilization of a soluble tert-butyldimethylsilyl chloride-modified poly(p-phenylene benzobisoxazole) (TBS-PBO) as an EBL for simultaneous good charge carrier transfer balance while maintaining high current density. We show that the versatile TBS-PBO blocks excess electron injection into the QDs, thus leading to better charge carrier transfer balance...
April 18, 2018: ACS Applied Materials & Interfaces
Haojian Yu, Xudong Dai, Fangnan Yao, Xiang Wei, Jin Cao, Chulgyu Jhun
In this paper, efficient phosphorescent white organic light-emitting diodes (WOLEDs) were fabricated based on ultrathin doping-free emissive layers and mixed bipolar interlayers. The energy transfer processes were proved via the research of WOLEDs with different interlayer thicknesses and transient photoluminescence lifetime. WOLEDs with optimized thickness of doping-free emissive layers show maximum current efficiency of 47.8 cd/A and 44.9 cd/A for three-colors and four-colors WOLEDs, respectively. The Commission Internationale de L'Eclairage coordinates shows a very slight variation of ( ± 0...
April 17, 2018: Scientific Reports
Egle Paskeviciute, Bernadeta Zudyte, Zivile Luksiene
The aim of this study is to evaluate the antimicrobial efficiency of Chlorophyllin-based photosensitization for microbial control of cherry tomatoes. Chlorophyllin-based photosensitization (1.5 × 10-4  M, 3 J/cm2 ) significantly (2.4 log) reduced the population of naturally distributed surface attached various mesophilic bacteria (microbiota) on tomatoes. Moreover, the population of thermoresistant strains of food pathogens Bacillus cereus and Listeria monocytogenes inoculated on tomatoes was reduced by 1...
April 11, 2018: Journal of Photochemistry and Photobiology. B, Biology
Chia-Lung Tsai, Yi-Chen Lu, Sheng Hsiung Chang
Photocurrent extraction and electron injection in CH3NH3PbBr3 (MAPbBr3) perovskite-based optoelectronic devices are both significantly increased by improving the contact at the PCBM/MAPbBr3 interface with an extended solvent annealing (ESA) process. Photoluminescence quenching and X-ray diffraction experiments show that the ESA not only improves the contact at the PCBM/MAPbBr3 interface but also increases the crystallinity of the MAPbBr3 thin films. The optimized dual-functional PCBM-MAPbBr3 heterojunction based optoelectronic device has a high power conversion efficiency of 4...
April 17, 2018: Nanotechnology
Hyeonggeun Yu, Yuanhang Cheng, Menglin Li, Sai-Wing Tsang, Franky So
Direct integration of an infrared photodetector with an organic light-emitting diode (OLED) enables low cost, pixel-free infrared imaging. However, the operation voltage of the resulting infrared-to-visible up-conversion is large due to the series device architecture. Here, we report a low voltage near infrared (NIR)-to-visible up-conversion device using formamidinium lead iodide as a NIR absorber integrated with a phosphorescent OLED. Due to the efficient photocarrier injection from the hybrid perovskite layer to the OLED, we observed a sub-bandgap turn-on of the OLED under NIR illumination...
April 17, 2018: ACS Applied Materials & Interfaces
Gintare Grybauskaite-Kaminskiene, Dmytro Volyniuk, Viktorija Mimaite, Oleksandr Bezvikonnyi, Audrius Bucinskas, Gintautas Bagdziunas, Juozas Vidas Grazulevicius
Derivatives of 9-phenyl-9H-carbazole were synthesized as efficient emitters exhibiting both thermally activated delayed fluorescence and aggregation induced emission enhancement. Effects of methoxy and tert-butyl substituents at the different positions of carbazolyl groups on the properties of the emitters were studied. Depending on the substitutions, photoluminescence quantum yields (PLQY) of non-doped solid films of the compounds ranged from 17% to 53% which were much higher than those observed for the solutions in low-polarity solvent toluene...
April 16, 2018: Chemistry: a European Journal
Quan Niu, Roland Rohloff, Gert-Jan A H Wetzelaer, Paul W M Blom, N Irina Crăciun
Polymer light-emitting diodes (PLEDs) are attractive for use in large-area displays and lighting panels, but their limited stability under current stress impedes commercialization. In spite of large efforts over the last two decades a fundamental understanding of the degradation mechanisms has not been accomplished. Here we demonstrate that the voltage drift of a PLED driven at constant current is caused by the formation of hole traps, which leads to additional non-radiative recombination between free electrons and trapped holes...
April 16, 2018: Nature Materials
Yulong Feng, Zhizhong Chen, Shuang Jiang, Chengcheng Li, Yifan Chen, Jinglin Zhan, Yiyong Chen, Jingxin Nie, Fei Jiao, Xiangning Kang, Shunfeng Li, Tongjun Yu, Guoyi Zhang, Bo Shen
We analyzed the coupling behavior between the localized surface plasmon (LSP) and quantum wells (QWs) using cathodoluminescence (CL) in a green light-emitting diodes (LED) with Ag nanoparticles (NPs) filled in photonic crystal (PhC) holes. Photoluminescence (PL) suppression and CL enhancement were obtained for the same green LED sample with the Ag NP array. Time-resolved PL (TRPL) results indicate strong coupling between the LSP and the QWs. Three-dimensional (3D) finite difference time domain (FDTD) simulation was performed using a three-body model consisting of two orthogonal dipoles and a single Ag NP...
April 16, 2018: Nanomaterials
Xiao-Ke Liu, Feng Gao
Recently, lead halide perovskite materials have attracted extensive interest, in particular, in the research field of solar cells. These materials are fascinating "soft" materials with semiconducting properties comparable to the best inorganic semiconductors like silicon and gallium arsenide. As one of the most promising perovskite family members, organic-inorganic hybrid Ruddlesden-Popper perovskites (HRPPs) offer rich chemical and structural flexibility for exploring excellent properties for optoelectronic devices, such as solar cells and light-emitting diodes (LEDs)...
April 13, 2018: Journal of Physical Chemistry Letters
Benedita Maria Costa-Neta, Abdias Ribeiro Lima-Neto, Apoliana Araújo da Silva, Jefferson Mesquita Brito, João Vitor Castro Aguiar, Islana Silva Ponte, Francinaldo Soares Silva
In this study the phototactic response of anopheline mosquitoes to different luminous intensity light-emitting diodes (LEDs) was investigated. Centers for Disease Control-type light traps were changed by replacement of the incandescent lamps by 5 mm round type green (520 nm) and blue (470 nm) LEDs of different luminous intensities: green-LED traps with luminous intensities of 10,000, 15,000 and 20,000 millicandela (mcd) and the blue-LED traps with luminous intensities of 4000, 12,000 and 15,000 mcd...
April 9, 2018: Acta Tropica
John Diaz-Montano, James F Campbell, Thomas W Phillips, James E Throne
Psocids have become global pests of stored commodities as they can cause considerable economic losses. These insects are difficult to control because they have developed resistance to many chemical insecticides. Therefore, it is crucial to investigate alternative integrated pest management (IPM) approaches, such as the use of light attraction for monitoring and/or controlling psocids. Light attraction has been studied for Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae) but not for other psocid species...
April 10, 2018: Journal of Economic Entomology
Jungwoon Kim, Suhan Lee, Jaemin Lee, Eunhee Lim, Byung Jun Jung
Solution-processed organic light-emitting diodes (OLEDs) are attractive due to their low-cost, large area displays, and lighting features. Small molecules as well as polymers can be used as host materials within the solution-processed emitting layer. Herein, we report two 3,3'-bicarbazole-based host small molecules, which possess a structural isomer relationship. 9,9'-Di-4-n-butylphenyl-9 H ,9' H -3,3'-bicarbazole ( BCz-nBuPh ) and 9,9'-di-4-t-butylphenyl-9 H ,9' H -3,3'-bicarbazole ( BCz-tBuPh ) exhibited similar optical properties within solutions but different photoluminescence within films...
April 8, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Juan Rodríguez, Diego G Lamar, Daniel G Aller, Pablo F Miaja, Javier Sebastián
Visible light communication (VLC) based on solid-state lighting (SSL) is a promising option either to supplement or to substitute existing radio frequency (RF) wireless communication in indoor environments. VLC systems take advantage of the fast modulation of the visible light that light emitting diodes (LEDs) enable. The switching-mode dc-to-dc converter (SMCdc-dc ) must be the cornerstone of the LED driver of VLC transmitters in order to incorporate the communication functionality into LED lighting, keeping high power efficiency...
April 7, 2018: Sensors
Qiong Wu, Ramanaskanda Braveenth, Heng Qiang Zhang, Il-Ji Bae, Miyoung Kim, Kyu Yun Chai
In this study, a series of bipolar fluorescence emitters named 2DPAc-OXD, DPAc-OXD, 2PTZ-OXD and PTZ-OXD were designed and synthesized with excellent yields. The characterization of materials was investigated by using nuclear magnetic resonance (NMR) (¹H, 13 C), mass spectrometry and thermogravimetric analysis (TGA). To investigate device efficiencies, two different OLED devices (Device 1, Device 2) were fabricated with two different host materials (Bepp₂, DPEPO). The Device 2 with 2PTZ-OXD as fluorescent emitter exhibited excellent power and current efficiencies of 6...
April 7, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Konda Karthik Roy, Kanumuru Pavan Kumar, Gijo John, Sujatha Gopal Sooraparaju, Surya Kumari Nujella, Kyatham Sowmya
Aim: The aim of this study is to compare and to evaluate effect of curing light and curing modes on the nanohybrid composite resins with conventional Bis-GMA and novel tricyclodecane (TCD) monomers. Methodology: Two nanohybrid composites, IPS empress direct and charisma diamond were used in this study. Light-emitting diode (LED)-curing unit and quartz-tungsten-halogen (QTH)-curing unit which were operated into two different modes: continuous and soft start. Based on the composite resin, curing lights, and mode of curing used, the samples were divided into 8 groups...
January 2018: Journal of Conservative Dentistry: JCD
Qi Lu, Tushar H Ganjawala, Samer Hattar, Gary W Abrams, Zhuo-Hua Pan
Purpose: To develop an animal behavioral assay for the quantitative assessment of the functional efficacy of optogenetic therapies. Methods: A triple-knockout (TKO) mouse line, Gnat1-/-Cnga3-/-Opn4-/-, and a double-knockout mouse line, Gnat1-/-Cnga3-/-, were employed. The expression of channelrhodopsin-2 (ChR2) and its three more light-sensitive mutants, ChR2-L132C, ChR2-L132C/T159C, and ChR2-132C/T159S, in inner retinal neurons was achieved using rAAV2 vectors via intravitreal delivery...
March 1, 2018: Investigative Ophthalmology & Visual Science
Shuchao Xu, Zhijun Wang, Panlai Li, Ting Li, Qiongyu Bai, Zhiping Yang
In order to achieve broad-band white emitting phosphor, Ce3+ /Dy3+ codoped Ba2 B2 O5 were synthesized by a solid-state method, and the luminescence property and energy transfer were discussed in detail. Dy3+ doped Ba2 B2 O5 shows white emission, and the two narrow peaks which are assigned to the4 F9/2 →6 H15/2 and4 F9/2 →6 H13/2 transitions of Dy3+ ions, respectively. When codoped Ce3+ as sensitizer, the broad-band white emission can be obtained by the energy transfer from Ce3+ to Dy3+ ions in Ba2 B2 O5 , and the mechanism is the dipole-dipole interaction...
March 27, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
W R Kim, S G Bae, T H Oh
In veterinary medicine, infection caused by Malassezia pachydermatis is spreading and necessity of alternative treatment is emphasized. Photodynamic therapy (PDT) is therapeutic method using specific spectrum of light with photosensitizer. In this study, applying PDT not only using red light which is used in human medicine commonly, but also using blue light into skin infection causative microorganism with photosensitizer, confirm the effect of PDT and possibility of being an alternative treatment. Four isolates of M...
March 2018: Polish Journal of Veterinary Sciences
Lin Gan, Xianglong Li, Xinyi Cai, Kunkun Liu, Wei Li, Shi-Jian Su
The design of orange-light emitting, thermally activated, delayed fluorescence (TADF) materials is necessary and important for the development and application of organic light-emitting diodes (OLEDs). Herein, two donor-acceptor-donor (D-A-D)-type orange TADF materials based on fluorenone and acridine, namely 2,7-bis(9,9-dimethylacridin-10(9 H )-yl)-9 H -fluoren-9-one (27DACRFT, 1 ) and 3,6-bis(9,9-dimethylacridin-10(9 H )-yl)-9 H -fluoren-9-one (36DACRFT, 2 ), were successfully synthetized and characterized...
2018: Beilstein Journal of Organic Chemistry
Hyo-Ju Lee, Semi Oh, Ki-Yeop Cho, Woo-Lim Jeong, Dong-Seon Lee, Seong-Ju Park
Metal nanowires have been gaining increasing attention as the most promising stretchable transparent electrodes for emerging field of stretchable optoelectronic devices.Nano-welding technology is a major challenge in the fabrication of metal nanowire networks since the optoelectronic performances of metal nanowire networks are mostly limited by the high junction resistance between nanowires. We demonstrate the spontaneous and selective welding of Ag nanowires (AgNWs) by Ag solders via an electrochemical Ostwald ripening process and high electrostatic potential at the junctions of AgNWs...
April 5, 2018: ACS Applied Materials & Interfaces
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