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Light-emitting diodes

Jin-Hoon Kim, Jin-Woo Park
We present a simple, low-cost, and scalable method to form various patterns of nanomaterials with different dimensions and shapes using capillary and centrifugal forces. The desired patterns were formed on the surfaces of polydimethylsiloxane (PDMS) stamps, and the PDMS stamps were conformally contacted with the surfaces of flexible polymer substrates. Solutions of nanomaterials, such as metal nanowires and nanoparticles, were then drop-casted at one open end of the microchannels formed at the interface of the polymer substrate and PDMS stamp...
February 23, 2018: ACS Applied Materials & Interfaces
Haoran Wang, Xiaomin Li, Mingjian Yuan, Xuyong Yang
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 CH3 NH3 PbBr3 (MAPbBr3 ) perovskite films are systematically investigated...
February 23, 2018: Small
Wei-Lun Liang, Guo-Dung J Su
We propose a train headlamp system using dual half-circular parabolic aluminized reflectors. Each half-circular reflector contains five high-efficiency and small-package light-emitting diode (LED) chips, and the halves are 180° rotationally symmetric. For traffic safety, the headlamp satisfies the Code of Federal Regulations. To predict the pattern of illumination, an analytical derivation is developed for the optical path of a ray that is perpendicular to and emitted from the center of an LED chip. This ray represents the main ray emitted from the LED chip and is located at the maximum illuminance of the spot projected by the LED source onto a screen...
February 20, 2018: Applied Optics
Feng Li, Chao Nie, Lai You, Xiao Jin, Qin Zhang, Yuancheng Qin, Feng Zhao, Yinglin Song, Zhongping Chen, Qinghua Li
White light emitting diodes (WLEDs) based on quantum dots (QDs) are emerging as robust candidates for white light source, however they are suffering from the problem of energy loss resulted from the re-absorption and self-absorption among the employed QDs of different peak wavelengths. It still remains a challenging task to construct WLEDs based on single-phase QD emitters. Here, CdS QDs with short synthesis time is introduced to the fabrication of WLEDs. With short synthesis time, on one hand, CdS QD of small diameter with blue emission can be obtained...
February 22, 2018: Nanotechnology
Le Han, Ben Liu, Xianyan Chen, Haiyan Chen, Wenjia Deng, Changsheng Yang, Bin Ji, Miaojian Wan
Activation of the Wnt/β-catenin signaling pathway plays an important role in hair follicle morphogenesis and hair growth. Recently, low-level laser therapy (LLLT) was evaluated for stimulating hair growth in numerous clinical studies, in which 655-nm red light was found to be most effective and practical for stimulating hair growth. We evaluated whether 655-nm red light + light-emitting diode (LED) could promote human hair growth by activating Wnt/β-catenin signaling. An in vitro culture of human hair follicles (HFs) was irradiated with different intensities of 655-nm red light + LED, 21 h7 (an inhibitor of β-catenin), or both...
February 21, 2018: Lasers in Medical Science
Qiaogang Song, Tong Lin, Xue Sun, Bei Chu, Zisheng Su, Huishan Yang, Wenlian Li, Chun-Sing Lee
The electronic level alignment at the ITO/PbI2 interface is investigated by an ultraviolet photoelectron spectroscopy. An n-type conductivity property is found for PbI2 as well as a downward shift energy level at the ITO/PbI2 interface. These indicate that PbI2 can be used as an anode buffer layer for organic electronic devices. The power conversion efficiency of the organic solar cell based on tetraphenyldibenzoperiflanthene/C70 planar heterojunction is dramatically increased from 1.05% to 3.82%. Meanwhile, the thermally activated delayed fluorescence organic light-emitting diode based on 4,4´,4"-tri(N-carbazolyl)triphenylamine:((1,3,5-triazine-2,4,6-triyl)tris(benzene-3,1diyl))tris(diphenylphosphine oxide) shows a significant reduced turn-on voltage and enhanced power efficiency from 6...
February 21, 2018: ACS Applied Materials & Interfaces
Ryo Karakawa, Hidehiko Yoshimatsu, Takuya Iida
Supplemental Digital Content is available in the text.
January 2018: Plastic and Reconstructive Surgery. Global Open
Lingling Wu, Guojun Wen, Yudan Wang, Lei Huang, Jiang Zhou
Horizontal auger boring (HAB) is a widely used trenchless technology for the high-accuracy installation of gravity or pressure pipelines on line and grade. Differing from other pipeline installations, HAB requires a more precise and automated guidance system for use in a practical project. This paper proposes an economic and enhanced automated optical guidance system, based on optimization research of light-emitting diode (LED) light target and five automated image processing bore-path deviation algorithms...
February 15, 2018: Sensors
Matthew D Smith, Hemamala I Karunadasa
With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white...
February 20, 2018: Accounts of Chemical Research
Sebastian Stolz, Uli Lemmer, Gerardo Hernandez-Sosa, Eric Mankel
We investigate three amine-based polymers, polyethylenimine and two amino-functionalized polyfluorenes, as electron injection layer (EIL) in organic light-emitting diodes (OLEDs) and find correlations between the molecular structure of the polymers, the electronic alignment at the emitter/EIL interface and the resulting device performance. X-ray photoelectron spectroscopy (XPS) measurements of the emitter/EIL interface indicate that all three EIL polymers induce an upwards shift of the Fermi level in the emitting layer close to the interface similar to n-type doping...
February 20, 2018: ACS Applied Materials & Interfaces
Hussam Milly, Avijit Banerjee
PURPOSE: To clinically examine the effect of the type of ight-curing unit on the light intensity output and to assess different operator variables which affect light curing of photo-initiated restorative dental materials, in Damascus, Syria. MATERIALS AND METHODS: A total of 185 private dental practices in the Damascus area were visited to invite the clinicians to participate in this study. The intensity of 163 light-curing units (LCUs) was assessed by radiometry in a standard protocol...
2018: Oral Health & Preventive Dentistry
Naresh B Kotadiya, Hao Lu, Anirban Mondal, Yutaka Ie, Denis Andrienko, Paul M W Blom, Gert-Jan H A Wetzelaer
Barrier-free (Ohmic) contacts are a key requirement for efficient organic optoelectronic devices, such as organic light-emitting diodes, solar cells, and field-effect transistors. Here, we propose a simple and robust way of forming an Ohmic hole contact on organic semiconductors with a high ionization energy (IE). The injected hole current from high-work-function metal-oxide electrodes is improved by more than an order of magnitude by using an interlayer for which the sole requirement is that it has a higher IE than the organic semiconductor...
February 19, 2018: Nature Materials
Navaporn Sritong, Siwat Chumsook, Sineenat Siri
Due to size- and shape-dependent properties, a shape-controlled synthesis of silver nanoparticles (AgNPs) is one of the research challenging topics for their production and potential applications. This work reported the simple eco-friendly syntheses of different shaped AgNPs controlled by the plasmid DNA content and light emitting diodes (LEDs) irradiation. The synthesized AgNPs appeared as yellow, orange and green colloidal AgNPs, which transmission electron microscope (TEM) images revealed their different shapes; spherical AgNPs, a mixture of spherical and hexagonal AgNPs, and a mixture of spherical, hexagonal and corner-truncated triangle AgNPs, respectively...
February 19, 2018: Artificial Cells, Nanomedicine, and Biotechnology
Saiedeh Saghafi, Nikoo Haghi-Danaloo, Klaus Becker, Inna Sabdyusheva, Massih Foroughipour, Christian Hahn, Marko Pende, Martina Wanis, Michael Bergmann, Judith Stift, Balazs Hegedus, Balazs Dome, Hans-Ulrich Dodt
Based on the modal analysis method, we developed a model that describes the output beam of a diode pumped solid state (DPSS) laser emitting a multimode beam. Measuring the output beam profile in the near field and at the constructed far field the individual modes, their respective contributions, and their optical parameters are determined. Using this information, the beam is optically reshaped into a quasi-Gaussian beam by the interference and superposition of the various modes. This process is controlled by a mode modulator unit that includes different meso-aspheric elements and a soft-aperture...
February 19, 2018: Journal of Biophotonics
Xu Wang, Fang Li, Ziqi Cai, Kaifan Liu, Jing Li, Boyang Zhang, Jianbo He
In this work, a multilayer-modified paper-based colorimetric sensing platform with improved color uniformity and intensity was developed for the sensitive and selective determination of uric acid and glucose with smartphone as signal readout. In detail, chitosan, different kinds of chromogenic reagents, and horseradish peroxidase (HRP) combined with a specific oxidase, e.g., uricase or glucose oxidase (GOD), were immoblized onto the paper substrate to form a multilayer-modified test paper. Hydrogen peroxide produced by the oxidases (uricase or GOD) reacts with the substrates (uric acid or glucose), and could oxidize the co-immoblized chromogenic reagents to form colored products with HRP as catalyst...
February 17, 2018: Analytical and Bioanalytical Chemistry
C Suresh, H Nagabhushana, R B Basavaraj, G P Darshan, D Kavyashree, B Daruka Prasad, S C Sharma, R Vanithamani
For the first time, intense red color composite of SiO2 @LaOF:Eu3+ core-shell nanostructures (NS) were fabricated via facile solvothermal method followed by thermal treatment. The obtained core-shell particles display better spherical shape and non-agglomeration with a narrow size distribution. Photoluminescence (PL) emission spectra exhibits intense peaks at ∼593 nm, 611 nm, 650 nm corresponds to5 D0 → 7 FJ (J = 0, 1 and 2) Eu3+ transitions respectively. The spectral intensity parameters and Eu-O ligand behaviors are estimated by means of Judd-Ofelt (J-O) theory...
February 15, 2018: Journal of Colloid and Interface Science
Ji Young Kim, Woo Young Kim, Kok Wai Cheah
This work seeks to establish a quantitative method which can estimate the holes and electrons ratio in the emission zones. We fabricated multilayered white organic light-emitting diodes (WOLEDs) with the device structure of ITO/NPB(80 nm)/MADN:BUBD-1(7%)(20 nm)/MADN:DCJTB(0.3%)(20 nm)/TPBi(X nm)/LiF(2 nm)/Al as a case study on the charge recombination distribution in the emissive layer. The result shows a trend in the charge recombination ratio depending on the electron transport layer thickness. We obtained an empirical relationship between electron transport layer thicknesses and emission ratio in EML...
February 16, 2018: Scientific Reports
Cheng-Ting Chiu, Dong-Hwang Chen
Three-dimensional (3D) porous Ni-Co sulfide/reduced graphene oxide composite with the appropriate incorporation of carbon nanotubes (NCS/rGO/CNT) was fabricated as a promising material for supercapacitor electrodes. It combined the high pseudo-capacitance of Ni-Co sulfide as well as the large specific surface area and electrical double layer capacitance of reduced graphene oxide (rGO). Carbon nanotubes (CNTs) were incorporated to act as the spacer for hindering the restacking of rGO and to construct a conductive network for enhancing the electron transport...
February 16, 2018: Nanotechnology
Seungjin Lee, Thanh Luan Nguyen, Sang Yun Lee, Chung Hyeon Jang, Bo Ram Lee, Eui Dae Jung, Song Yi Park, Yung Jin Yoon, Jin Young Kim, Han Young Woo, Myoung Hoon Song
Conjugated polyelectrolytes (CPEs) with π-delocalized main backbones and ionic pendant groups are intensively studied as interfacial layers for efficient polymer-based optoelectronic devices (POEDs) because they facilitate facile control of charge injection/extraction barriers. Here, a simple and effective method of performing precise interfacial energy level adjustment is presented by employing CPEs with different thicknesses and various ion densities under electric poling to realize efficient charge injection/extraction of POEDs...
February 16, 2018: Advanced Materials
R R Valiev, V N Cherepanov, G V Baryshnikov, D Sundholm
A method for calculating the rate constants for internal-conversion (k IC ) and intersystem-crossing (k ISC ) processes within the adiabatic and Franck-Condon (FC) approximations is proposed. The applicability of the method is demonstrated by calculation of k IC and k ISC for a set of organic and organometallic compounds with experimentally known spectroscopic properties. The studied molecules were pyrromethene-567 dye, psoralene, hetero[8]circulenes, free-base porphyrin, naphthalene, and larger polyacenes...
February 16, 2018: Physical Chemistry Chemical Physics: PCCP
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