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Light-emitting diodes

Qiuhong Cui, Guillermo C Bazan
Two essential structural elements define a class of materials called conjugated polyelectrolytes (CPEs). The first is a polymer framework with an electronically delocalized, π-conjugated structure. This component allows one to adjust desirable optical and electronic properties, for example the range of wavelengths absorbed, emission quantum yields, electron affinity, and ionization potential. The second defining feature is the presence of ionic functionalities, which are usually linked via tethers that can modulate the distance of the charged groups relative to the backbone...
December 14, 2017: Accounts of Chemical Research
Jae-Yong Lee, Sungbin Jeon, Jin-Sang Lim, Se-Hwan Jang, No-Cheol Park, Young-Joo Kim
This Letter proposes a dual-wavelength, low-coherence digital holography system with a single light source, which utilizes a quantum dot (QD) film as a wavelength converter. By changing the size of the QDs, the proposed method easily yields higher and more uniform illumination of any target wavelength, compared with bandpass-filtered light-emitting diodes. Fabrication parameters of the QD film for better conversion efficiency are discussed. Using this light source with the dual-wavelength reconstruction method extends the efficiency and range of nanoscale three-dimensional height measurements...
December 15, 2017: Optics Letters
Mehdi Ahmadi, Farshid Ghanbari
Several efforts have been carried out to present an efficient method for PMS activation. This work presented the use of UVC-LEDs (light emitting diodes) and US (ultrasound) to activate PMS for decolorization of Direct Orange 26 (DO26). The performance of UVC-LEDs/US/PMS process was effective in a broad range of pH (3.0-9.0). Complete decolorization was obtained in only 12 min in pH = 7.0 and 1.5 mM PMS. Bicarbonate and nitrite ions showed inhibitory effect on decolorization while sulfate, chloride, and nitrate had no significant effect on the performance of the process...
December 13, 2017: Environmental Science and Pollution Research International
Tingting Liu, Jianwen Zhao, Weiwei Xu, Junyan Dou, Xinluo Zhao, Wei Deng, Changting Wei, Wenya Xu, Wenrui Guo, Wenming Su, Jiansheng Jie, Zheng Cui
Fabrication and application of hybrid functional circuits have become a hot research topic in the field of printed electronics. In this study, a novel flexible diode-transistor logic (DTL) driving circuit is proposed, which was fabricated based on a light emitting diode (LED) integrated with printed high-performance single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs). The LED, which is made of AlGaInP on GaAs, is commercial off-the-shelf, which could generate free electrical charges upon white light illumination...
December 13, 2017: Nanoscale
Jiangyong Pan, Changting Wei, Lixi Wang, Jinyong Zhuang, Qianqian Huang, Wenming Su, Zheng Cui, Arokia Nathan, Wei Lei, Jing Chen
We report an inverted and multilayer quantum dot light emitting diode (QLED) which boosts high efficiency by tuning the energy band alignment between charge transport and light emitting layers. The electron transport layer (ETL) was ZnO nanoparticles (NPs) with an optimized doping concentration of cesium azide (CsN3) to effectively reduce electron flow and balance charge injection. This is by virtue of a 0.27 eV upshift of the ETL's conduction band edge, which inhibits the quenching of excitons and preserves the superior emissive properties of the quantum dots due to the insulating characteristics of CsN3...
December 13, 2017: Nanoscale
Ali Hariri, Jeanne Lemaster, Junxin Wang, AnanthaKrishnan S Jeevarathinam, Daniel L Chao, Jesse V Jokerst
Photoacoustic imaging (PAI) is a non-invasive, high-resolution hybrid imaging modality that combines optical excitation and ultrasound detection. PAI can image endogenous chromophores (melanin, hemoglobin, etc.) and exogenous contrast agents in different medical applications. However, most current equipment uses sophisticated and complicated OPO lasers with tuning and stability features inconsistent with broad clinical deployment. As the number of applications of PAI in medicine increases, there is an urgent need to make the imaging equipment more compact, portable, and affordable...
March 2018: Photoacoustics
Iurii Kim, Pyry Kivisaari, Jani Oksanen, Sami Suihkonen
Almost all modern inorganic light-emitting diode (LED) designs are based on double heterojunctions (DHJs) whose structure and current injection principle have remained essentially unchanged for decades. Although highly efficient devices based on the DHJ design have been developed and commercialized for energy-efficient general lighting, the conventional DHJ design requires burying the active region (AR) inside a pn-junction. This has hindered the development of emitters utilizing nanostructured ARs located close to device surfaces such as nanowires or surface quantum wells...
December 12, 2017: Materials
Francine Benetti, Cleidiel Aparecido Araújo Lemos, Marjorie de Oliveira Gallinari, Amanda Miyuki Terayama, André Luiz Fraga Briso, Rogério de Castilho Jacinto, Gustavo Sivieri-Araújo, Luciano Tavares Angelo Cintra
OBJECTIVES: This systematic review (PROSPERO register: CRD42016053140) investigated the influence of different types of light on the pulp tissue during dental bleaching. MATERIALS AND METHODS: Two independent authors conducted a systematic search and risk of bias evaluations. An electronic search was undertaken (PubMed/Medline, Embase, The Cochrane Library, and other databases) until May 2017. The population, intervention, comparison, outcomes (PICO) question was: "Does the light in dental bleaching change the response of the pulp to the bleaching procedure?" The intervention involved pulp tissue/cells after bleaching with light, while the comparison involved pulp tissue/cells after bleaching without light...
December 11, 2017: Clinical Oral Investigations
Xinping Chen, Walter D Leon-Salas, Taylor Zigon, Donald F Ready, Vikki M Weake
A programmable optical stimulator for Drosophila eyes is presented. The target application of the stimulator is to induce retinal degeneration in fly photoreceptor cells by exposing them to light in a controlled manner. The goal of this work is to obtain a reproducible system for studying age-related changes in susceptibility to environmental ocular stress. The stimulator uses light emitting diodes and an embedded computer to control illuminance, color (blue or red) and duration in two independent chambers...
October 2017: HardwareX
Huicheng Hu, Linzhong Wu, Yeshu Tan, Qixuan Zhong, Min Chen, Yinghua Qiu, Di Yang, Baoquan Sun, Qiao Zhang, Yadong Yin
The poor stability of CsPbX3 (X = Cl, Br, I) nanocrystals has severely impeded their practical applications. Although there are some successful examples on encapsulating multiple CsPbX3 nanocrystals into an oxide or polymer matrix, it has remained a serious challenge for the surface modification/encapsulation using oxides or polymers at a single particle level. In this work, monodisperse CsPbX3/SiO2 and CsPbBr3/Ta2O5 Janus nanoparticles were successfully prepared by combining a water-triggered transformation process and a sol-gel method...
December 11, 2017: Journal of the American Chemical Society
Xining Zang, Caiwei Shen, Emmeline Kao, Roseanne Warren, Ruopeng Zhang, Kwok Siong Teh, Junwen Zhong, Minsong Wei, Buxuan Li, Yao Chu, Mohan Sanghadasa, Adam Schwartzberg, Liwei Lin
While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS2 ) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g-1 in an Li-rich electrolyte...
December 11, 2017: Advanced Materials
Giyeong Son, Byung Il Lee, You Jung Chung, Chan Beum Park
The self-assembly of β-amyloid (A β) peptides into highly stable plaques is a major hallmark of Alzheimer's disease. Here, we report visible light-driven dissociation of β -sheet-rich A β aggregates into small, nontoxic fragments using ruthenium (II) complex {[Ru(bpy)3]2+} that functions as a highly sensitive, biocompatible, photoresponsive anti-A β agent. According to our multiple analyses using thioflavin T, bicinchoninic acid, dynamic light scattering, atomic force microscopy, circular dichroism, and Fourier transform infrared spectroscopy, [Ru(bpy)3]2+ successfully disassembled A β aggregates by destabilizing the β -sheet secondary structure under illumination of white light-emitting diode light...
December 5, 2017: Acta Biomaterialia
Rui Deng, Jing He, Yang Hong, Jin Shi, Lin Chen
The camera-based visible light communication (CVLC) exploiting rolling shutter effect (RSE) is a cost-efficient technique that ensures secured data transmission. By controlling the on-off state of the light emitting diode (LED), data can be modulated onto the emitting visible light. The corresponding data recovery can be realized by exploiting the RSE of the mobile-phone camera. In this paper, based on a commercial RGB-LED and a single mobile-phone camera, a wavelength division-multiplexing (WDM) CVLC system exploiting RSE is experimentally demonstrated...
November 27, 2017: Optics Express
Honglei Wang, Shih-Chia Liu, Balasubramaniam Balachandran, Jiyoung Moon, Ross Haroldson, Zhitong Li, Artur Ishteev, Qing Gu, Weidong Zhou, Anvar Zakhidov, Walter Hu
Recently, solution-processed hybrid halide perovskite has emerged as promising materials for advanced optoelectronic devices such as photovoltaics, photodetectors, light emitting diodes and lasers. In the mean time, all-dielectric metasurfaces with high-index materials have attracted attention due to their low-loss and high-efficient optical resonances. Because of its tunable by composition band gap in the visible frequencies, organolead halide perovskite could serve as a powerful platform for realizing high-index, low-loss metasurfaces...
November 27, 2017: Optics Express
Sun-Kap Kwon, Eun-Hyung Lee, Kwan-Soo Kim, Hyun-Chul Choi, Mi Jin Park, Seong Keun Kim, Ramchandra Pode, Jang Hyuk Kwon
Micro-cavity top-emitting organic light emitting diodes (TEOLEDs) are now receiving prominence as a technology for the active matrix display applications. The semi-transparent metal cathode plays the crucial role in realizing TEOLEDs structure. Here, we report the optimization results on Mg:Ag ratio as the semitransparent cathode deposited by vacuum thermal evaporation. The optimized Mg:Ag cathode with 1:10 ratio (wt %) shows a sheet resistance value as low as 5.2 Ω/□, an average transmittance of 49.7%, reflectance of 41...
November 27, 2017: Optics Express
Junyi Gong, Yue Wang, Sheng Liu, Pan Zeng, Xilu Yang, Rongqing Liang, Qiongrong Ou, Xiang Wu, Shuyu Zhang
Halide perovskite materials have rapidly emerged as outstanding optoelectronic materials for solar cells, light-emitting diodes (LEDs), and lasers. Compared to hybrid organic-inorganic perovskites, all-inorganic perovskites have shown unique merits that may contribute to the ultimate goal of developing electrically-pumped lasers. In this paper, we demonstrate a distributed feedback (DFB) resonator using an all-inorganic perovskite thin film as the gain medium. The film has a gain coefficient of 161.1 cm-1 and a loss coefficient of 30...
November 27, 2017: Optics Express
Naoki Okamura, Takeshi Maeda, Hideki Fujiwara, Anjaly Soman, K N Narayanan Unni, Ayyappanpillai Ajayaghosh, Shigeyuki Yagi
Novel heteroleptic cyclometalated platinum(ii) complexes consisting of 5'-benzoylated 2-phenylpyridinate (ppy) cyclometalated and acetylacetonate ancillary ligands were synthesized, and their photoluminescence (PL) properties were investigated. The 5'-benzoylated complex without any other substituents exhibited phosphorescence-based monomer emission at 479 nm in dichloromethane (10 μM, rt) with a PL quantum yield of 0.28. On the other hand, in poly(methyl methacrylate) (PMMA) film, remarkable excimer emission additionally emerged at ca...
December 8, 2017: Physical Chemistry Chemical Physics: PCCP
Jong Min Kim, Sung Kim, Sung Won Hwang, Chang Oh Kim, Dong Hee Shin, Ju Hwan Kim, Chan Wook Jang, Soo Seok Kang, Euyheon Hwang, Suk-Ho Choi, Sherif H El-Gohary, Kyung Min Byun
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...
December 8, 2017: Nanotechnology
Fanqi Wu, Liang Chen, Anyi Zhang, Yi-Lun Hong, Nai-Yun Shih, Seong-Yong Cho, Gryphon A Drake, Tyler Fleetham, Sen Cong, Xuan Cao, Qingzhou Liu, Yihang Liu, Chi Xu, Yuqiang Ma, Moonsub Shim, Mark E Thompson, Wencai Ren, Hui-Ming Cheng, Chongwu Zhou
Printing technology has potential to offer a cost-effective and scalable way to fabricate electronic devices based on two-dimensional (2D) transition metal dichalcogenides (TMDCs). However, limited by the registration accuracy and resolution of printing, the previously reported printed TMDC field-effect transistors (FETs) have relatively long channel lengths (13-200 μm), thus suffering low current-driving capabilities (≤0.02 μA/μm). Here, we report a "flood-dike" self-aligned printing technique that allows the formation of source/drain metal contacts on TMDC materials with sub-micrometer channel lengths in a reliable way...
December 8, 2017: ACS Nano
Weixuan Zeng, Hsin-Yu Lai, Wei-Kai Lee, Min Jiao, Yi-Jiun Shiu, Cheng Zhong, Shaolong Gong, Tao Zhou, Guohua Xie, Monima Sarma, Ken-Tsung Wong, Chung-Chih Wu, Chuluo Yang
The combination of rigid acridine donor and 1,8-naphthalimide acceptor has afforded two orange-red emitters of NAI-DMAC and NAI-DPAC with high rigidity in molecular structure and strongly pretwisted charge transfer state. Endowed with high photoluminescence quantum yields (ΦPL ), distinct thermally activated delayed fluorescence (TADF) characteristics, and preferentially horizontal emitting dipole orientations, these emitters afford record-high orange-red TADF organic light-emitting diodes (OLEDs) with external quantum efficiencies of up to 21-29...
December 8, 2017: Advanced Materials
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