1,721,500 research outputs found
Transfer or delivery of micro light-emitting diodes for light-emitting diode displays
Full text linkAs the next-generation display technology, microscale light-emitting diode (mu-LED) displays have attracted significant attention recently. For applying mu-LEDs as direct emissive pixels in everyday display applications, many chips in a relatively small-sized wafer must be relocated and distributed quickly over a wide screen area via so-called transfer technology. After a brief review of current conventional transfer technologies for placing mu-LEDs on a wide screen, for perspective, a new and versatile delivery technique for mu-LEDs is presented, in which an LED chip is converted to a ball shape in order to facilitate handling and processing of mu-LEDs for practical applications. Plausible procedures including the formation, arrangement, and removal of the plastic ball are discussed to envision potential impacts of the technology. (c) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).11Ysciescopu
Efficiency droop in GaInN high-power light-emitting diodes
No full textGaN-based light-emitting diodes suffer from high-current loss mechanisms that lead to a significant decrease in internal quantum efficiency at high drive currents. This phenomenon, known as "efficiency droop," is a major problem for solid-state lighting applications, in which light-emitting diodes are driven at high currents to deliver large optical powers. Although substantial effort has been invested to uncover the physical origin and mitigate the effects of efficiency droop, there is still a lack of consensus on the dominant mechanism responsible. In this article, we review several mechanisms that have been proposed as explanations of efficiency droop, including junction heating, carrier delocalization, Auger recombination, and electron leakage from the active region. In addition, device structures intended to mitigate the droop-causing mechanism – (i) thick quantum wellsl, (ii) enhanced hole-injection efficiency structures, and (iii) polarization-matched active region – are discussed.113scopu
DO ALCOHOLIC KORSAKOFF 'S SYNDROME PATIENTS ACQUIRE AFFECTIVE REACTIONS?
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An effect of a mandatory counseling program for college students on academic probation: a preliminary study
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White light-emitting diodes: History, progress, and future
No full textAbout twenty years ago, in the autumn of 1996, the first white light-emitting diodes (LEDs) were offered for sale. These then-new devices ushered in a new era in lighting by displacing lower-efficiency conventional light sources including Edison's venerable incandescent lamp as well as the Hg-discharge-based fluorescent lamp. We review the history of the conception, improvement, and commercialization of the white LED. Early models of white LEDs already exceeded the efficiency of low-wattage incandescent lamps, and extraordinary progress has been made during the last 20 years. The review also includes a discussion of advances in blue LED chips, device architecture, light extraction, and phosphors. Finally, we offer a brief outlook on opportunities provided by smart LED technology.115211sciescopu
Highly-sensitive H2 sensor operating at room temperature using Pt/TiO2 nanoscale Schottky contacts
No full textDespite growing demands for high performance hydrogen (H-2) sensors operating at low temperature, metal oxides-based H-2 sensors intrinsically require an elevated operating temperature due to a high activation energy for gas adsorption on metal oxides surface. Here, we present a highly-sensitive H-2 sensor operating even at room temperature, enabled by the Pt/TiO2 nanoscale Schottky contacts which utilizes sensitive modulation of the Schottky barrier height by dissociative H-2 adsorption on the catalytic Pt layer, followed by the dipole layer formation at the junction. Our device showed very high H-2 response and short response and recovery times at low temperatures which are attributed to the unique device architecture having the highly-porous nanoscale Schottky contacts facilitating the gas diffusion and dissociation, and the top-and-bottom electrodes configuration making effective current modulation. Based on our results, we propose Schottky contact-assisted H-2 sensing mechanisms and a promising approach to further improve H-2 sensing performance at room temperature. (C) 2016 Elsevier B.V. All rights reserved.1115sciescopu
Remarkable increase in triboelectrification by enhancing the conformable contact and adhesion energy with a film-covered pillar structure
No full textStructural modification of the surface has been widely investigated in triboelectric energy generation to improve the power harvested. Large contact area, large surface area and good dielectric performance are the basic design principles needed for the structures, while energy harvesting from low-energy mechanical motions is desirable. This work suggests that a film-covered pillar structure made of polydimethylsiloxane (PDMS) improved its output performance by satisfying all the basic design parameters, especially, the conformable contact and easy deformation. The contact area and the adhesion energy of the film-covered pillar structure are quantitatively compared with those from the flat PDMS substrates and the pillar-only structures. We report that the film-covered pillar structure remarkably enhances the charge generation and increases the output voltage and the current density. We also emphasize the optimized thickness of the cover film for triboelectric performance. The triboelectric power generator operating by low-energy mechanical motions like a gentle finger-touch has been demonstrated as a possibility for human-based energy harvesting device in the future. ? 2017 Elsevier Ltd117Nsciescopu
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