Dissertations / Theses on the topic 'Impulse light emitting diode'
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Дядечко, Алла Миколаївна, Алла Николаевна Дядечко, Alla Mykolaivna Diadechko, and D. V. Shapko. "Organic light-emitting diode." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/13445.
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An organic light emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes. Generally, at least one of these electrodes is transparent.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/13445
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Leirset, Erlend. "Photonic crystal light emitting diode." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10014.
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This master's thesis describe electromagnetic simulations of a gallium antimonide (GaSb) light emitting diode, LED. A problem for such devices is that most of the generated light is reflected from the surface due to total internal reflection, and is therefore prevented from coupling out of the semiconductor material. Etching out a 2D photonic crystal grating on the LED surface would put aside the absolute rule of total internal reflection, and could therefore be used to increase the total transmission. The simulation method which was developed was supposed to find geometry parameters for the photonic crystal to optimize the light extraction. A set of plane waves were therefore simulated using FDTD to build an equivalent to the Fresnel equations for the photonic crystal surface. From that the total transmittance and radiation patterns for the simulated geometries were calculated. The results indicated an increase in the transmission properties of up to 70% using a square grating of holes where the holes have a radius of 0.5µm, the hole depth is 0.4µm, and the grating constant is 1µm. A hexagonal grating of holes and a square grating of isotropically etched holes were also simulated, and featured improvements on the same scale, but with different dimensions for the holes. The simulations were computationally very demanding, and the simulation structure therefore had to be highly trimmed to limit the calculation time to reasonable values. This might have reduced the accuracy of the results. Especially the optimum grating constant, and the value of the optimum improvement itself is believed to be somewhat inaccurate.
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Guan, Nan. "Nitride nanowire light-emitting diode." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS372/document.
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Les nanofils nitrures présentent des propriétés optoélectroniques extraordinaires et sont considérés comme des matériaux prometteurs pour des diodes électroluminescentes (LEDs), grâce à leur haute qualité cristalline, leurs surfaces non-polaires, leur bonne flexibilité mécanique, leur rapport d’aspect élevé, etc.Cette thèse adresse la croissance, la fabrication, les caractérisations optiques et électriques et la simulation optique des dispositifs à base de nanofils nitrures, avec un accent particulier sur les LEDs à nanofils.Premièrement, cette thèse présente la croissance par épitaxie en phase vapeur aux organométalliques de nanofils nitrures cœur-coquille auto-assemblés contenant des puits quantiques InGaN/GaN sur les facettes plan m avec différentes concentrations d’In. Puis est décrite la fabrication de LEDs utilisant ces nanofils suivant deux différentes stratégies d’intégration (intégrations planaires et verticales).L’intégration planaire est basée sur des nanofils uniques dispersés horizontalement. J’ai proposé une plateforme photonique intégrée composée d’une LED à nanofil, d’un guide d’onde optimisé et d’un photodétecteur à nanofil. J’ai également développé un système d’alignement des nanofils.L’intégration verticale a pour objectif la réalisation de LEDs flexibles reposant sur une assemblée de nanofils verticaux encapsulées dans des polymères. Je montre que ceci permet la fabrication de LEDs flexibles monochromatiques, bi-couleurs ou blanches.Les nanofils épitaxiés sur des matériaux 2D par épitaxie de van de Waals sont faciles à décoller de leur substrat natif. Avec cette motivation, dans la dernière partie de cette thèse, j’ai étudié la croissance organisée des nanofils GaN sur du graphène micro et nano-structuré utilisant l’épitaxie par jets moléculairesNitride nanowires exhibit outstanding opto-electronic and mechanical properties and are considered as promising materials for light-emitting diodes (LEDs), thanks to their high crystalline quality, non-polar facets, good mechanical flexibility, high aspect ratio, etc.This Ph.D. thesis addresses the growth, the device fabrication, the optical and electrical characterizations and the optical simulations of III-nitride NW devices, with a special emphasis on the LED applications.First, this thesis presents the growth of m-plane InGaN/GaN quantum wells with different In concentrations in self-assembled core-shell nanowires by metal-organic chemical vapor deposition. Then, by using these nanowires, LED devices based on two different integration strategies (namely, in-plane and vertical integration) are demonstrated.The in-plane integration is based on the horizontally dispersed single nanowires. I have proposed a basic integrated photonic platform consisting of a nanowire LED, an optimized waveguide and a nanowire photodetector. I have also developed a nanowire alignment system using dielectrophoresis.The vertical integration targets the fabrication of flexible LEDs based on vertical nanowire arrays embedded in polymer membranes. Flexible monochromatic, bi-color, white LEDs have been demonstrated. Their thermal properties have been analyzed.The nanowires grown on 2D materials by van der Waals epitaxy are easy to be lifted-off from their native substrate, which should facilitate the fabrication of flexible nanowire devices. With this motivation, in the last part of this thesis, I have investigated the selective area growth of GaN NWs on micro- and nano- scale graphene by molecular beam epitaxy
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Lau, Kwok Hing Connie. "Stacked organic light emitting diode." HKBU Institutional Repository, 2008. http://repository.hkbu.edu.hk/etd_ra/916.
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Hood, Sean. "Light emitting diode color rendition properties." Kansas State University, 2013. http://hdl.handle.net/2097/15647.
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Master of ScienceDepartment of Architectural Engineering and Construction Science
Fred Hasler
This paper discusses the color rendition capabilities of light emitting diodes (LEDs) and their relationship with the current standard for color rendition quality. The current standard for judging light source color rendering properties, known as the color rendering index (CRI), has come under heavy scrutiny in recent years with the introduction of LED in commercial lighting applications. LEDs, depending on construction type, have highly structured spectral distributions which do not scale well under the color rendering index; moreover, CRI for LEDs has become disjointed with the subjective measurement of human color preference. Unfortunately, given the multidimensional nature of color, an all-encompassing scale with a single rated value for color rendition capabilities of a light source has proven difficult to establish. An analysis on the human visual system is first discussed, establishing how the visual system first detects color in the eye and subsequently encodes that color information through a color-opponent process, formulating conscious color appearance. The formation of color appearance leads into a discussion on human color vision and the creation of three dimensional color space, which is subsequently used for the measurement of color fidelity (CRI) of consumer light sources. An overview of how LED lamps create light and color is then discussed, showing that the highly structured spectral distribution of LED lamps is often the cause of discrepancy within the CRI system. Existing alternatives to the CRI system are then compared and contrasted to each other, and the existing CRI system. A final color preference study was conducted where four LED lamps where compared to a reference lamp of equal correlated color temperature. Observers were asked to rate the various test lamps against the reference lamp in terms of vividness, naturalness, overall preference, and individual color preference. It was found that no significant difference was found between the first three dimensions measured but significant trend lines existed for the preference of individual colors when illuminated by either LED lamps or the reference source. Recommendations are then made for how the lighting industry could move forward in terms of color metrics.
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Ferreira, Ricardo Xavier da Graça. "Gallium nitride light-emitting diode enabled visible light communications." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28805.
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This thesis focuses on the development, measurement and application of novel micrometre-sized light emitting diodes (micro-LEDs) based on Gallium Nitride (GaN) for visible light communications (VLC) in both free-space and guided wave configurations. The goal is to set benchmarks for LED-based wireless optical communications. An overview of the field integrating research, industry and standards is presented. A top-down approach is taken with application requirements driving development of new micro-LEDs with simultaneously increased optical power and modulation bandwidth. This was achieved by mitigating two limitations, namely current crowding and mutual device heating. Two novel techniques were developed to access pixel performance: spatially-resolved mapping of modulation bandwidth and spectral characteristics, and thermal imaging. On this basis, broad-area LEDs were used to understand the independent benefits, providing insight for the design of novel micro-LEDs. Circular segmented micro-LEDs emitting at 450nm achieved modulation bandwidths in excess of 800MHz, the highest reported for LEDs, while maintaining optical power above 2mW. In data transmission using systems with 1.8GHz bandwidth,the devices achieved 8Gbps in free-space and guided-wave operation at wavelengths of 400nm, 450nm and 520nm. Ring and half-ring micro-LEDs introduced here have shown modulation bandwidths that scale with the increase of active area and consequently optical power. Bandwidths in excess of of 600MHz were achieved at optical powers over 5mW. In data transmission using a system limited to 1GHz bandwidth, these devices achieved 7Gbps in free-space operation.
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Ng, Wai-nap, and 吳卉納. "Micro-and nano-light-emitting diode arrays." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B4088787X.
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Lai, Yin Hing. "High power flip-chip light emitting diode /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20LAI.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 60-68). Also available in electronic version. Access restricted to campus users.
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Ng, Wai-nap. "Micro-and nano-light-emitting diode arrays." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B4088787X.
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Башлак, Ірина Анатоліївна, Ирина Анатольевна Башлак, Iryna Anatoliivna Bashlak, and D. Y. Panasiuk. "Organic light emitting diode technology in brief." Thesis, Вид-во СумДУ, 2009. http://essuir.sumdu.edu.ua/handle/123456789/16798.
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Li, Zonglin, and 李宗林. "Reliability study of InGaN/GaN light-emitting diode." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43224155.
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Li, Zonglin. "Reliability study of InGaN/GaN light-emitting diode." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43224155.
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Deram, Paul. "Light-emitting-diode (LED) lighting for greenhouse tomato production." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116996.
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The cost of artificial lighting is a major expense in the greenhouse production industry, especially during the winter where supplemental lighting is required to maintain production. Current technology uses broad spectrum high pressure sodium lamps (HPS), which, despite being excellent luminous sources, are not the most efficient light source for plant production. Specific light frequencies have been shown to impact photosynthesis more directly than others (especially in the red and blue ranges); focusing on specific wavelengths, light-emitting diodes (LEDs) could diminish lighting costs due to their high efficiency and lower operating temperatures. LEDs can be selected to target the wavelengths absorbed by plants, enabling the growers to customize the wavelengths of light required to maximize production and limit wavelengths that do not significantly impact plant growth. The primary purpose of this experiment was to test tomato plants (Solanum lycopersicum), in a research greenhouse using a full factorial design with three light intensities (High: 135 µmol m-2 s-1, Medium: 115 µmol m-2 s-1 and Low: 100 µmol m-2 s-1) at three red to blue ratio levels (5:1, 10:1 and 19:1) compared to 100% HPS, and a control (no supplemental lighting). The exact wavelengths chosen were 449 nm for the blue and 661 nm for the red. Secondary treatments were also tested using 100% red light supplied from the top, 100% red light supplied from the bottom, a 50%:50% LED:HPS and a replicate of the 10:1 ratio with High light intensity. The experiment was replicated over two different seasons (Summer-Fall 2011 and Winter-Spring 2011-2012). During the experiment, the highest biomass production (excluding fruit) occurred with the 19:1 ratio (red to blue), with increasing intensity resulting in more growth, whereas a higher fruit production was obtained using the 5:1 ratio. The highest marketable fruit production (fruit over 90 g, Savoura internal standard) was the 50%:50% LED:HPS, followed by 5:1 High and 19:1 High. From this research, LEDs have been shown to be superior in fruit production over HPS alone, and LEDs can improve tomato fruit production with HPS and have the ability to become the dominant supplemental greenhouse lighting system.Le coût de l'éclairage artificiel est une dépense importante dans le secteur de la production en serre, surtout en hiver lorsqu'un éclairage supplémentaire est nécessaire pour maintenir le niveau de production. La technologie actuelle utilise des lampes à haute pression de sodium (HPS), qui en dépit d'être d'excellentes sources lumineuses, ne sont pas les sources lumineuses les plus efficaces pour la production végétale. Certaines fréquences spécifiques de lumière ont montré avoir un impact plus direct sur la photosynthèse que d'autres (en particulier dans les gammes de rouge et de bleu); en mettant l'accent sur certaines longueurs d'onde, les diodes électroluminescentes (LED) pourraient diminuer les coûts d'éclairage, en raison du rendement élevé et des températures plus basses de ce type de lampe. Les LED peuvent cibler les principales fréquences de lumière mieux absorbées par les plantes, ce qui permettrait aux producteurs de créer une lumière aux longueurs d'onde adaptées à la production optimale des plantes. Le principal objectif de cette expérience était de tester les lampes sur des plants de tomate (Solanum lycopersicum) dans une serre de recherche en utilisant un plan factoriel complet avec trois intensités lumineuses (Haute: 135 μmol m-2 s-1, Moyenne: 115 μmol m-2 s-1 et Basse: 100 μmol m-2 s-1) et trois proportions de rouge et bleu (5:1, 10:1 et19: 1), et comparer leur performance à celle de 100% HPS, et d'un contrôle (pas d'éclairage supplémentaire). Les longueurs d'onde choisies sont 449 nm (bleu) et 661 nm (rouge). Certains traitements secondaires ont également été testés, dont 100% rouge (éclairage par le haut ou le bas), un 50%:50% LED:HPS et une reproduction du 10:1 à haute intensité. L'expérience a été menée au cours de deux saisons différentes (été-automne et hiver-printemps). La production végétative la plus importante s'est produite avec le rapport 19:1 (rouge : bleu). La production de fruits était la plus élevé avec le rapport 5:1. La production en fruits commercialisables la plus importante (fruits de 90 g et plus : étalon interne de Savoura) a été pour le 50%:50% LED:HPS, suivi du 5:1 et 19:1 à haute intensité. Les LED se sont montrés supérieures aux HPS quant à la production de tomates.
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Gunning, Jack Peter. "Poly(dendrimer)s for organic light emitting diode displays." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509953.
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Chan, Kin Wing. "Multiplexing and angular distribution of organic light emitting diode /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202002%20CHANK.
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Zhao, Xinyue M. Eng Massachusetts Institute of Technology. "Commercialization of Quantum Dot White Light Emitting Diode technology." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37678.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.Includes bibliographical references.
It is well known that the use of high-brightness LEDs for illumination has the potential to substitute conventional lighting and revolutionize the lighting industry over the next 10 to 20 years. However, successful penetration of this extremely large lighting market would require vast improvements in power conversion efficiencies, color index, light output per device and drastic reduction in cost. Quantum Dot white LED (QD WLED) technology may be one of the best choices, due to its higher energy efficiency, larger color render in index, better versatility and more importantly lower cost, compared to conventional blue LED plus YAG: Ce yellow phosphor technology. Due to the fundamental difference of the material structure, QD LEDs will win a steady position among existing white LED patents and a hybrid fabless plus IP business model has the best position to promote this technology to maximize its benefits and potential for the entire LED industry.
by Xinyue Zhao.
M.Eng.
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Soon, Chian Myau. "White light emitting diode as liquid crystal display backlight." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42159.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references.
The discovery of high brightness (white) light emitting diode (LED) is considered as a real threat to the current lighting industry in various applications. One of the most promising sectors would be using white LED to replace the current Cold Cathode Fluorescent Light (CCFL) technology as the backlight of the large screen Liquid Crystal Display (LCD) screen due to the fact that LCD is a rapidly booming market.
by Chian Myau Soon.
M.Eng.
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Salter, Cameron Lewis. "Development and application of an entangled-light-emitting diode." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610428.
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Darade, Balasaheb S. "Hole-Confining Concept for Blue Organic Light Emitting Diode." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321370334.
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Gau, Huan-Jie, and 高煥捷. "Blue Phosphorescent Organic Light-Emitting Diode and Alternating Driven Current Organic Light-Emitting Diode." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/r2we9f.
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碩士元智大學
光電工程學系
104
In this thesis, the first part is disclosed a series of novel host materials combining hole-transporting moiety, Carbazole, and electron-transporting moieties Triazole and Pyridine, as bipolar host to fabricate high efficiency blue phosphorescence organic light-emitting diode (OLED) with the blue phosphorescent emitting dopant, FIrpic. Second part is the development of an alternating current (AC)-driven organic light emitting diodes (OLED). We co-depositied these materials to modulate their energy level. We designed a symmetrical device structure, to achieve the lit-on OLED at positive and negative half-cycle stage in AC driven. In the chapter I, we introduced the OLED relatives, including history, principle, recent development of OLED in materials and device. Chapter II described the experimental detail to fabricate the OLED devices and some know-how. Chapter III results and discussion, we characterized four novel host materials by, measuring of the absorption spectrum, highest occupied electronic energy levels (HOMO), lowest electronic unfilled full energy level (LUMO), and photoexited fluorescence spectrum. They were employed to host material of emitting layer (EML) of blue OLEDs. Varying the dopant concentration, and the thickness of electron-transporting layer to achieve electron-hole balance for high efficiency blue OLED. Furthermore, we also investigated the main recombination zone of EML using partial doped dopant at distinct EML position. Chapter IV introduced a method using a partial mixed host as a part of EML, combining o-DiCbzBz with various electron-transporting hosts, such as BTBP, DPPS, and TmPyPB. Varying the layer thickness of partial mixed host in EML, the main recombination zone was enlarged and the carrier balance could be achieved because we obtained a great improvement in the device efficiency. Chapter V demonstrated an alternating current (AC)-driven organic light emitting diodes (OLED) by modifying the carrier injection layer. The purpose was to fabricate a direct AC-driven OLED with any dielectric layer. The last Chapter VI was the thesis conclusions.
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Peng, Sheng-yang, and 彭聖揚. "Multifunctional white light emitting diode." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/79934244374666129071.
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碩士國立臺灣科技大學
光電工程研究所
100
The objective of this thesis to increase the functionality of white light emitting diode (WLED) use the multi-chips structure, modified omni-directional reflector (ODR) and TiO2 photocatalyst to package the WLED which has functionality of the tunable color garmut and air purification. The modified ODR has been improved according to the previous research, which property is that when light incident angle is 40°, the wavelength of 380 nm of transmittance is 40%. Because TiO2 photocatalyst have to be under the UV light emitting and TiO2 photocatalyst can be used to do air purification, we spray the TiO2 photocatalyst on the back side of the modified ODR to fabricate the compound element, and packaged with UV-excited white LED, where TiO2 can be work over the emitting angle of 40°. To packaged WLED with compound element and controlled the composition and concentration of phosphors blend layer by means of Taguchi Method. When TiO2 photocatalyst layers is 3 layers and WLED is at a constant driving current of 20 mA, the color coordinate for light source made was (0.3319, 0.3324), the color correlated temperature (CCT) was 5518 K, the color rendering index (CRI) was 94, the angle distribution of properties of WLED is uniformity, and it could work for degradation of methylene blue. This study proposed a purple light chip (λpeak = 410 nm) and a blue light chip (λpeak = 465 nm) combined with the above structure of UV-excited WLED, and we can achieve a multifunctional WLED which can be color tunable and for air purification by controlling the concentration of phosphor and driving current. Specifically, the color coordinate for light source made was (0.3332, 0.3357), the CCT was 5461 K and CRI was 83. Finally, we changed the chips of a multifunctional WLED for high power chips, and fabricated the WLED lamp to do the experiment of degradation of ammonia concentration. The result showed the multifunctional WLED can really work for air purification. The UV light chips and blue light chips were applied driving current at 20 mA or 100 mA, and it worked for 5 hrs, the degradation rate of ammonia concentration were 42.5 % or 64.3 %.
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Lin, Yu-Tang, and 林育瑭. "White Organic Light Emitting Diode." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/vpyk74.
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碩士中原大學
物理研究所
106
This work focusing on the realization of white organic light-emitting diodes by mixing blue and yellow-orange light. The Bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) with emission peak at about 490 nm and the LY220 with emission peak at about 600 nm were blended with the host polymer to realize the white light emission. The influences of blending ratio, emissive layer thickness, and annealing temperature on the device performance were investigated. The influence of the thickness LiF on the device performance were also investigated.
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Hsieh, Chun-Yu, and 謝濬宇. "Candle Light-Style Organic Light Emitting Diode." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/50845307637013042446.
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Генкін, Олексій Михайлович. "Еталонні джерела оптичного випромінювання на основі явища електричного пробою у P-N-структурах на карбіді кремнію." Doctoral thesis, 2010. https://ela.kpi.ua/handle/123456789/643.
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吳日中. "Organic Light-Emitting Diode Based Artificial Dusk-Light." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/31730494468755683827.
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Chang, Chin-Yeh, and 張勤業. "Contact-Printed Organic Light-Emitting Diode." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/14279122240202644377.
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chu-shin, Liang, and 梁竹欣. "Al2O3-Superlattice Light-Emitting Tunnel Diode." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/50684681770027768580.
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碩士國立交通大學
電子工程系
89
An ITO/superlattice/p-Si tunnel diode used as a light-emitting device was made on the Si substrate. The superlattice (SL) is formed by alternatively depositing ITO and Al2O3 materials, and the thickness of each SL layer is in the range of 10~20Å. At a forward bias -3V, strong and uniform electroluminescence (EL) from SL tunnel diode is detected, and the emitted light is mainly located in the infrared region. The light intensity from SL tunnel diode is three orders of magnitude larger than hot-carrier induced light emission in MOSFETs, and near 10000 greater than gate-injected MOS tunnel diode. At higher biasing conditions (>-7V), the high-energy tail can even be seen by naked eyes. We thought electrons from the minibands of SL tunnel into Si substrate and relax their extra energy via radiative recombination and/or impact ionization. The SL structure is used to elevate the injecting electron energy and reduce electric field inside Al2O3 layers. The use of Al2O3 arises from the advantages of its good dielectric integrity and high permittivity. Better hole confinement and larger extra momentum of carriers are found in the Al2O3 SL tunnel diodes. The momentum conservation for radiative recombination is easier to achieve, thus EL from the Si substrate will be enhanced.
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Chang, Chuan-Ming, and 章絹明. "The ZnSe Light Emitting Diode Process." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/23827058288946107273.
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碩士國立成功大學
電機工程學系碩博士班
93
In this thesis, We study ZnSe white Light Emitter Diode. We focus two topics. One is self-emitting white LED. Another one is phosphors effective with ZnSe LED. The self-emitting ZnSe white LED we study two types model. One is normal type p-side up. Another is N-side up. The same wafer Used different process we can get more light efficiency and change CIE . The ZnSe white LED used phosphors can easily change CIE . The CIE X from 0.3 to 0.45, Y from 0.28 to 0.4, the ZnSe LED color can be change from bluish to golden.
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Hsu, Hao-Chun, and 徐浩淳. "Study on light extraction of organic light-emitting diode." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/bnk32k.
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碩士國立臺灣大學
光電工程學研究所
106
In this thesis, we study on light extraction of organic light-emitting device (OLED) with nanostructures. There are two part in the thesis. The first one is varying the pitch of nanostructured for the OLEDs. And the second is varying the electron transport layer (ETL) thickness of the nanostructured OLEDs. In chapter 3, we use gratings with three different pitches (833.33, 416.67, 277.78 nm) to fabricate nanostructured OLED. With macrolens and 416.67-nm pitch nanostructure, 103.02% external quantum efficiency (EQE) enhancement can be obtained. With polarizer, we can separate transverse electric (TE) and transverse magnetic (TM) waves, which can be used to calculate the light extraction from surface plasmon (SP) mode and waveguiding mode. In chapter 4, electron transport layer (ETL) of the nanostructured OLEDs (pitch= 416.67 nm) was modulated (15, 40, 115, 165 and 215 nm). With 40-nm ETL nanostructured OLED, maximum EQE performance could be obtained. From the EL measurement of the nanostructured OLED, it was found that extraction of SP mode decreased with increasing the ETL thickness. On the other hand, extraction of waveguiding mode increased then decreased at the same time.
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Chuang, Yu-Cheng, and 莊又澄. "Interface Characteristics Of Green Light Organic Light Emitting Diode." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/tc85a4.
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碩士國立中興大學
物理學系所
106
Organic light emitting diode (OLED) is one of the main display technologies. Compared with LCD displays, it has advantages of self-illumination, wide viewing angle, high contrast, low power consumption, high response rate, full color and simple process. OLED is also used as a light source for warning lights on automobiles, which is a technology that has considerable business potential and high research value. In this study, first, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to observe the surface morphology, surface roughness, and adhesiveness of the OLED''s hole transport layer, emitting material layer and electron injection layer, use the above information to analyze the properties of materials at the nanometer scale. And using photoelectron spectroscopy (PES) analyzer such as X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) analyzes the kinetic energy distribution, chemical bonding, chemical elements and other information of the OLED''s hole transport layer, emitting material layer and electron injection layer, use these kinds of information to analyze and speculate on the transition of electrons and holes in OLEDs. Second, Prepare an OLED device and measure its current-voltage relationship and brightness,use this research to find effective ways to improve the competitiveness of products.
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Lin, Yan-De, and 林彥德. "The development of GaAs Red Light Emitting Diode and 960×540 GaAs-based Micro Light Emitting Diode Array." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/egznk2.
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Wu, Chia-Lin, and 吳佳霖. "High Power Light Emitting Diode Package Study." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/41451175903243777660.
Full textAbstract:
碩士國立交通大學
工學院碩士在職專班半導體材料與製程設備組
95
By the increasing of Light output at light-emitting diodes(LED), the LED is beginning to show widespread application on the market. From the indicator light, traffic signal light, backlighting for LCD television and cellphone, car lighting and the market of white light source, it makes a new vitality in the LED industry. With the variety of application area, the LED technology goes toward two direction. One of the application is the chip miniaturization, it is used in the cellphone, digital camera and the Laptop. The other one is the large format panel, it is used to the backlighting for LCD television, lamp of projector, car headlight, architectural and the outdoor lighting. No matter what the chip miniaturization or the large area display, how to improve the light efficiency of LED chip for increasing light intensity is the common topic. To enhance the bright intensity of LED, one is to increase the light efficiency of LED and the other one is to increase the input power. By increasing the input power to achieve high brightness, the adequate heat-sinking is required to be improved. to be improved. In this thesis, we focused on the large area LED in the high input power application. We developed a new package experiment to improve the heat-sinking problem. Based on the cost and functionality, we choose the Silicon for the package substrate. We designed two layout on the Silicon chip in order to fix the same phase P/N and different phase P/N of 40mil chip on the substrate. After we accomplished the substrate, we used array method to fix the two chips and applied the current from 20mA to 2A to measure the Luminous flux、Vf、and Dominate wavelength.
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He, Guan-Ru, and 何冠儒. "Quality Improvement of Light Emitting Diode Drivers." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/30805863861456888894.
Full textAbstract:
碩士國立中央大學
光電科學研究所碩士在職專班
100
This thesis uses a Flyback Converter power supply as the LED constant drive source circuit,collocating discontinuous conduction mode and choosing IC BCD SEMICONDUCTOR CORPORATION AP1680K6TR-G1 being the main component.In order to improve the shortcomings of the low power factor and high current total harmonic distortion (THD) of this IC,by increasing the power factor circuit architecture in the circuit, the power factor was improved significantly by 0.234 and the current total harmonic distortion (THD) was decreased significantly by 54.27%. Finally, use the Taguchi method on the circuit to conduct quality design to achieve optimization of 49.68% and conform EN 61000-3-2.
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Nien, Yi-Hsin, and 粘逸昕. "Germanium P-N Junction Light Emitting Diode." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/77003483256756392472.
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碩士國立臺灣大學
光電工程學研究所
100
In this thesis, we discussed the reduction of direct bandgap emission which is caused by the reabsorption effect of Germanium emission. The variation of effective lifetime caused by different surface recombination velocity affects the carrier distribution profile. As the reabsorption effect is a function of distance, carriers diffuse to the deeper side of wafer which enhances reabsorption effect by decreasing back surface recombination velocity. By the way, extremely large back surface recombination velocity leads the carrier to crowd at the surface to reduce reabsorption effect. The emission ratio of direct and indirect transition can be explained by the carrier distribution profile which is simulated using Sentaurus. In the vertical germanium light emitting diode structure, electrons will be drifted to the deeper side of wafer by electric field which enhances reabsorption effect. The lateral germanium light emitting diode structure allows electrons to crowd at the surface which not only moves the electron Fermi level upwards and the increase in electron population in direct valley enhance the luminescence but also reduces reabsorption effect. The crowding effect increases with the closer lateral contact.
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Wu, Jou-Hsuan, and 吳柔萱. "An Improved InGaN/GaN Light Emitting Diode." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55854314231693323998.
Full textAbstract:
碩士國立宜蘭大學
電子工程學系碩士班
101
In these studies, the state-of-the-art two-dimensional device simulation tool, ATLAS, from SILVACO is being evaluated for the purpose of studying light-emitting diodes (LEDs). It predicts the electron behavior of specified semiconductor structures, and provides insight into the internal physical mechanisms associated with device operation. We designed the active layer area is 300 μm 300 μm for blue InGaN/GaN multiple-quantum well (MQW) light-emitting diodes, using the SILVACO ATLAS tool, the two-dimensional device simulation package ATLAS was used to theoretically analyze physical device characteristic. Other important physical mechanisms and optical properties, such as luminescent power, electroluminescence intensity, energy band, electric field, carrier concentration, and recombination rate were also investigated in this study. First, doping of the electron-blocking, barrier and active region layers plays a crucial role in the efficiency of blue InGaN/GaN light-emitting diodes. The carrier concentration characteristics of InGaN/GaN LEDs are systematically studied. Next we investigate the original structure of InGaN/GaN LED. By inserting using Si δ-doped (n+) GaN/InGaN structure into the original structure, we can analyse whether it can improve the carrier confinement effect of quantum well in active region or not. And find out the best region to use Si δ-doped (n+) GaN/InGaN structure. Finally, the proposed structures with Si delta-doped GaN/InGaN are numerically simulated. In the meantime, a systematic analysis on the critical physical mechanisms relevant to the improvement of the optical performance. The carrier confinement effect has enhanced effectively with Si delta-doped GaN/InGaN structure. Key words: light-emitting diodes, InGaN, multiple-quantum well, δ-doped Author* Jou-Hsuan Wu Advisor** Shiou-Ying Cheng Ph. D.
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Yang, Y. K., and 楊延鍇. "AlGaInP Light Emitting Diode Junction Temperature study." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/20239708469798222678.
Full textAbstract:
碩士長庚大學
光電工程研究所
94
There are two generally and accurately method to measure junction temperature. These two methods are called emission peak wavelength shift method and diode forward-voltage method. The defect of these methods is that the junction temperature measurements are strongly depend on the device structures above the substrate. The influence of structures induced deviation and incommodity when measured junction temperature. This work discussed with using photoluminescence spectra of GaAs substrate excited by active layer. According to Varshni equation and the red shift of spectra, we have a new method of measuring junction temperature. The results of new method were consisting with emission peak wavelength shift method, and because the substrate PL spectra shift depend directly on temperature unaffected by the structures. On the other hand, by reaching the circular pattern for p-contact, the unevenness of temperature distribution and current crowding effect in high power AlGaInP LED when the operation current increase.
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Chen, Ming-Sheng, and 陳銘勝. "Process of GaN-based Light-emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/49245573361857716249.
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Lee, Chia-Ming, and 李家銘. "Investigation of InGaN/GaN Light Emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/18152097049547423378.
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博士國立中央大學
電機工程研究所
92
This dissertation includes the growth, fabrication, and characterization of Mg-doped GaN and InGaN/GaN multiple-quantum-well (MQW) light-emitting diode (LED) by metalorganic chemical vapor deposition (MOCVD). First, we utilized Hall measurement, photoluminescence (PL), and second ion mass spectrum (SIMS) to characterize p-type GaN and Mg distribution in GaN films. Although the Mg flow is constant during growth, the measurement data shows that the Mg concentration increases with growth time since the Mg concentration is higher when closer to the surface. Even when the thickness of p-type GaN reaches 2.5 μm, the increasing hasn’t slow down yet. The effect of different growth condition, such as growth temperature, III/V ratio and carrier gas, upon Mg incorporation in GaN is studied also. We found Mg diffusion not only in bulk p-type GaN but also in InGaN/GaN MQW LEDs. To improve the characteristics of InGaN/GaN MQW LED, we must understand its behavior first. So we tried to identify its emission mechanism by changing the operation temperature and current, and found the major cause of blue shift, which means peak emission wavelength shifts to shorter wavelength with higher injection current, is band-filling effect but not free carrier screen effect. In addition, we can identify whether the emission comes from well states or localized states from the way it shifts. When analyzing the emission mechanism of InGaN/GaN MQW LED, we also found the emission generated by Mg-doped GaN. Therefore, we designed another experiment to study the effect of Mg doping upon InGaN/GaN MQW LED. By the electroluminescence (EL) spectra measured under different operation temperatures, the peak emission wavelength of quantum wells and Mg-doped GaN is 3.1 eV and 2.7 eV respectively. When analyzing this emission behavior with rate equation and the relative intensity variation of these two peaks under different temperature, we can calculate and obtain the activation energy of Mg doping in GaN being 126 meV, which agrees with the results from other academic organization utilizing different otherwise method. We utilized selective activation technique in InGaN/GaN MQW LED process to improve its external quantum efficiency. Using this technique to activate Mg-doped GaN except the area underneath P-type bonding pad made us able to maintain its semi-insulating property, and further, it became a semi-insulating current blocking layer during device operation. This layer is utilized to prevent the injection current flowing through the area below P-pad since P-pad blocks the emission light from below and thus reduces the emission efficiency. From the luminescence intensity versus injection current chart, we did succeed in our effort to improve the external quantum efficiency when comparing to normal InGaN/GaN MQW LED. Since p-type GaN shows poor conductivity, normal InGaN/GaN MQW LED process utilizes a transparent conductive layer for current spreading. However, despite its name, this layer isn’t 100 % transparent, and thus would absorb/reflect certain portion of emission light. To prevent this loss, we changed the normal InGaN/GaN MQW LED structure, which is p-type above and n-type under MQW, by switching the p-type and n-type layers’ positions and adding a n+/p+ tunnel junction. By this change, there’s no need of this transparent conductive layer for current spreading, and the device external quantum efficiency become almost twice as high as before.
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Liu, Yu-Chuan, and 劉育全. "Investigation of InGaN/GaN Light Emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/79969050495085222285.
Full textAbstract:
碩士國立中央大學
電機工程研究所
92
A light-emitting device comprises a multi-layer structure including one or more active layer configured to irradiate light in response to the application of an electric signal, a transparent passivation layer laid over an outmost surface of the multi-layer stack, a reflector layer laid over the passivation layer, and a plurality of electrode pads coupled with the multi-layer structure. In a manufacture process of the light-emitting device, the reflector layer and the passivation layer are patterned to form at least one opening exposing an area of the multi-layer structure. One electrode pad is formed through the opening of the reflector layer and the passivation layer to connect with the multi-layer structure.
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Tsai, Chia-Lin, and 蔡佳霖. "Studies of White Polymer Light Emitting Diode." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/40661757859748513563.
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碩士國立清華大學
化學工程學系
97
This study involves polyspirofluorenes (sPF) modified by incorporation of charge transporting moieties on side-chain and chain-end to facilitate hole and electron injections. We investigate their electroluminescence behaviors with and without doping with orange fluorescent and red phosphor small molecules as the guest to obtain white and red emission devices. Three parts are included in this thesis. Firstly, by incorporation of triphenylamine (as hole receiver) and carbazole (as transporting bridge) as side-chain of sPF to yield TPA-Cz-sPF, balanced bipolar fluxes and charge mobilities can be realized. By using TPA-Cz-sPF as host material and (5,6,11,12)-Tetraphenylnaphthacene (rubrene) as guest material, single layer white emission LED is obtained having high efficiency of 21.07 cd/A (8.96%), and high luminance of 17,431 cd/m2. The present efficiency is the highest among reported white PLEDs. Secondly, we further modify sPF by incorporation of TPA and Cz on the same side-chain and of electron deficient 3-(4-phenyl)-4-phenyl-5-(4-tert-butylbenzene)-1,2,4-triazole (TAZ) group on polymer chain-end. The designed polymer exhibits improved bipolar injection transport capabilities and deeper blue emission as compared to that without chain-end modification. Single layer LED based on 50GsPF-end-TAZ achieves high efficiency of 6.08%, high luminance of 10,131 cd/m2, and deep blue emission with CIE (1.161, 0.052), revealing the present molecular design is a powerful methodology. Thirdly, We utilize the deep blue polymer 50GsPF-end-TAZ as host material, and dope with 2wt% red small molecule Bis(1-phenylisoquinoline) (acetylacetonate)iridium(III) (Ir(piq)2(acac)). Its single layer LED achieves high efficiency of 9.92% (12.06 cd/A), high luminance of 6,372 cd/m2, and red emission with CIE (0.67, 0.33) which is very closely to 1931 Commission International de l’Eclairage coordinate (CIEx,y 1931) saturation red light.
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Yun-Hsuan, Hsu, and 許勻亘. "The study of light emitting diode properties." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/qnh466.
Full textAbstract:
碩士國立高雄應用科技大學
電子工程系碩士班
102
Light emitting diodes （LEDs） have been rapidly developed and widely applied to our livelihood and other special applications, according to their high efficiency, small size, lower power consumption and long lifetime. In order to study the characteristics of LEDs, this work applies the first-principle theory as implemented in the CASTEP code to study new IV-group illuminating material, and applies the APSYS code to simulate the N-base LED characteristics. First, the density functional theory （DFT） is applied to study the energy gaps of GeSn alloy. The calculation results show that the direct-indirect crossover occurs at the mole fraction of ~ 6%. The calculated emitting powers for these gaps reveal that the lowest peak energy in experiment of strained Ge0.922Sn0.078 LED is mainly caused by the direct gap rather than indirect. Our results show that the strained Ge0.922Sn0.078 is direct gap. Second, the effect of strong polarization in N-base LEDs is studied. To reduce this effect, a pulse laser annealing （PLA） is used. Our experimental results show that the PLA significantly reduces the Piezoelectric fields and crystal imperfection of GaN LEDs.
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HUANG, KUAN-NENG, and 黃冠能. "Recycling of Waste Light-Emitting Diode Chip." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9uanee.
Full textAbstract:
碩士大葉大學
環境工程學系碩士班
105
The purpose of this research is to recover the valuable gallium and copper resources from waste light emitting diode chips. The main tasks of this research including waste light emitting diode chip sample collection, roasting, grinding, screeing, composition analysis, leaching, pH adjustment, replacement, precipitation and crystallization. The result of this research reveals that the composition of the collected waste light emitting diode chip was determined as 0.27% moisture content, 82.21% ash content and 17.51% combustible content. After roasting, grinding and screening, the total content of gallium and copper metal respectively in the -50 mesh sample were 475mg/kg and 393333 mg/kg. The best leaching conditions were as follows： 9N sulfuric acid, 2 hours, 70℃, 10ml hydrogen peroxide and a solid-liquid ratio of 1g/50ml. Under these conditions, 100% gallium and copper were leached. Next, iron plate replacement and pH adjustment to 13.5 using sodium hydroxide were evaluated for metal separation efficiency. Albeit both methods were able to achieve 100% gallium and copper separation, considering economic feasibility, the iron replacement method was selected as the most cost-efficient technique to separate the two metals. With this, high purity copper was obtained in solid form, and the remaining solution containing only gallium was filtered and crystalized to obtain a gallium crystal product.
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Chung, Chao-Chi, and 鍾超己. "Anelasticity study in GaN Light-emitting Diode." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/66796759266305880518.
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博士國立中央大學
化學工程與材料工程學系
105
Defects decline the light output efficient and life time of GaN-based LED. In our study, as the defect density of device is 2.17×10-9 cm-2, 3.636×10-9 cm-2, 4.654×10-9 cm-2, respectively, the external quantum efficient is 20.546 %, 19.563%, 16.785%, respectively. To establish a high accuracy and convenient defect measuring system is necessary. However, the defect measuring methods that commonly used have many limits. For example, XRD spectrum is only suitable for wafer size sample. TEM and EPD evaluating method are destructive measurement that waste many sample and cost much time. We established a defect measuring method in this study by analyzing anelasticity behavior of GaN-based LED after applying stress or external electric field. Defects develop Anelasticity behavior in solid. It causes the strain delay-responding after applying stress on material. Although there has complete study about anelasticity behavior of bulk material, the research of thin-film materials and the influence of semiconductors is lack. In this study, the anelasticity of the GaN layer in the GaN light-emitting-diode device was discussed. And, establish defect measurement system can be established. The studied chip was applied by thermal stress, piezoelectric stress, and external stress. The present results show that the decrease of forward-voltage of GaN LED is due to the degree of energy-level change as forward external electric field applied. After removing external electric field, the forward voltage increase with time. We found that the increment of the forward-voltage with time attributes to the delay-response of the piezoelectric fields (internal electrical fields in GaN LED device). We applied -0.5 V reverse bias and heat the chip to 100 oC, respectively. Thus, the forward voltage increases gradually due to the energy-level in GaN LED is flattened with time by thermal stress and external electric field. Furthermore, reverse bias (-1 V) flatten the energy level much more, so, the forward voltage enhancement is higher. As -5 V reverse bias is applying on the GaN LED, the voltage dropped due to the higher reverse bias tilted the energy-level in GaN LED again. Using the correlation of strain-piezoelectric-forward voltage, a plot of strain of the GaN layer against time can be obtained by measuring the forward-voltage of the studied GaN LED against time. The key anelasticity parameter, characteristic relaxation time τ, and anelastic strain Uan of the GaN would be analyzed by the curves of the thermal strain in GaN epi-layers versus time. For estimating the dislocation density, the studied GaN LED chips were etched by H3PO4 in 260 oC. The etching pits on GaN LED after H3PO4 reacted were calculated. GaN LED chip with higher dislocation density has higher τ and Umax, furthermore, the dislocation density and anelastic strain is linear relation. The results show the anelasticity behavior is attributed by defect. In other side, it is possible for establishing a defect measurement system by analyzing anelasticity behavior of GaN LED. The relation of defect density and anelastic strain can be expressed as Vf,max=0.00168×Ddis+0.00329. Vf,max is the forward-voltage difference induced by anelastic strain of GaN-based LED. Ddis is the density of dislocation in GaN-based LED.
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Chen, Wen-Yan, and 陳文彥. "Study of White Light Emitting Diode Package." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/03090168878464220794.
Full textAbstract:
碩士國立臺灣科技大學
電子工程系
96
White light emitting diodes (LEDs) are attractive for using as an illumination light source. Phosphor-converted white light LEDs, fabricated by near ultraviolate (UV) LED chips, have many advantages such as high color rendering index (CRI), and near true white chromaticity coordinates. However, the drawbacks of the white light LEDs are low luminous efficiency and instability of packaging materials. White light LED fabricated by two layers packaging structure was demonstrated. The requirements of lighting source such as correlated color temperature, average color rendering index (Ra) and chromaticity coordinates were measured. The correlated color temperature of white light LED is 5700K. The average color rendering index is 92 and chromaticity coordinates is (0.33, 0.33) respectively. The instability of correlated color temperature (CCT) with the light emitting angle is improved. The enhancement of luminous efficiency is about 10% by applying a photonic crystal on top of the white LED. The degradation of white light LED was discussed at the same time.
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Chen, Yu-Qiu, and 陳昱酋. "InGaN / GaN Light Emitting Diode Polarization Analysis." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/14783776738955605854.
Full textAbstract:
碩士國立宜蘭大學
電子工程學系碩士班
102
In these studies, the state-of-the-art two-dimensional device simulation tool, ATLAS, from SILVACO is being evaluated for the purpose of studying light-emitting diodes (LEDs). It predicts the electron behavior of specified semiconductor structures, and provides insight into the internal physical mechanisms associated with device operation. We designed the active layer area is 300 μm 300 μm for blue InGaN/GaN multiple-quantum well (MQW) light-emitting diodes, using the SILVACO ATLAS tool, the two-dimensional device simulation package ATLAS was used to theoretically analyze physical device characteristic. Other important physical mechanisms and optical properties, such as luminescent power, electroluminescence intensity, energy band, electric field, carrier concentration, and recombination rate were also investigated in this study. In this thesis, the first chapter, a brief history of the development of light-emitting diodes and motivation. The second chapter introduces the basic principles and characteristics of light-emitting diode materials, and a complete discussion of III-V nitride material properties. The third chapter describes the basic elements of this thesis depth to do a complete discussion of the model equations and theories used when TCAD simulation, the model used to do a complete discussion. Chapter IV simulation to identify InGaN / GaN layers doped concentration parameter optimization. Finally, changes its polarization effect, and analyzed at different polarization effects, the influence of an energy band diagram characteristic change element analysis. Key words：light-emitting diodes, InGaN, Polarization effects Author* Yu-Qiu Chen Advisor** Shiou-Ying Cheng Ph.D.
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Chuang, Ching-han, and 莊景涵. "Fabrication of Resonant-Cavity Light-emitting Diode." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/15126301381763027165.
Full textAbstract:
碩士國立臺灣大學
電子工程學研究所
91
This thesis presents the fabrication and optoelectronic properties of 870nm resonant-cavity light-emitting diodes (RCLED). The device structure of the RCLED is composed of a 30-pair AlGaAs bottom DBR reflector, a 1-λ cavity with 3 InGaAs quantum wells embedded on its center, an AlGaAs top DBR reflector, and a 5-μm-thick AlGaAs window layer. The window layer is used to avoid the current crowding effect at high current density. Devices with different upper DBR pair and with window layer removed were fabricated and compared. The device with 3 pairs DBR reflector and window layer has the highest light output intensity, 30 mW/sr. The near field measurement shows that window layer improves the current spreading. However, the luminescence spectrums indicate that the 5-μm-thick AlGaAs window layer itself provides an extra cavity and makes the device a couple-cavity RCLED. Three electroluminescence modes was observed in the RCLED with window layer. From current-dependent and temperature-dependent electroluminescence measurements, the obtained temperature coefficient of emission wavelength in all devices is about 0.1nm/°C and the calculated thermal resistance in devices without window layer is about 40°C /W.
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Huang, Hao-Hsuan, and 黃浩軒. "Recycling of Waste Light-Emitting Diode Backlight." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/96163544543562814159.
Full textAbstract:
碩士大葉大學
環境工程學系碩士班
103
The main purpose of this research is to analyze the composition and to study the recovery of valuable metals of light-emitting diode backlight of waste liquid crystal display. The result of research shows that LED backlight obtained from waste LCD screen accounts for 0.15% of the total weight of the LCD. Rare earth metals gallium (Ga), europium (Eu), yttrium (Y) and cerium were all present in the LED backlight with a concentration of 738.43mg/kg, 63.76mg/kg, 18.43mg/kg and 8.89mg/kg, respectively. 63.14% of a size -100 mesh sample was obtained after the collected LED backlight was roasted at 800℃ for 3 hours and then ground for 10 minutes. The roasted and ground LED backlight with a size -50 mesh was leached at 70℃, 0.5N NaOH, 0.5% H2O2 and 1g/25ml to obtain a 100% leaching recovery of Ga, whereas the leaching recovery of Eu and Y are 0%. Also, this Ga leaching solution was adjusted the pH to 5 by adding sulfuric acid to reach a 100% Gallium precipitation. After Ga leaching, the Eu and Y contained in the remaining solid was leached under the condition at 70℃, 4N HCl , 1 hour and 3g/50ml to obtain a 100% leaching recovery for both Eu and Y. The obtained Eu and Y leaching solution was adjusted the pH to 7 by adding sodium hydroxide and 100% Eu and Y precipitation can be achieved.
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Jen-Chieh, Yu, and 余仁傑. "The Application of Light Emitting Diode in Illumination Light Source." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/65341191793679504275.
Full textAbstract:
碩士輔仁大學
物理學系
97
In this research, the rugate notch filter is deposited by e-gun system in order to improve the daylight simulator spectrum; the daylight simulator is consisted of a few light emitting diodes (LEDs). Recently, the LED has extensively applied in illumination, e.g., streetlamp and taillight. However, most spectra of white LEDs are quite intense from near UV to 470 nm region. The intense light near the 470 nm wavelength will hurt the eyes and affect the combination of daylight simulator. The rugate notch filter fabricated by multilayer is used to reduce the spectrum near the 470 nm. By using this correction method, the property of daylight simulator can be improved. The correlated color temperature (CCT) and color rendering index (CRI) will be calculated and discussed.
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Chen, Jing-Ru, and 陳靜茹. "Enhancement of Light Extraction of GaN Blue Light Emitting Diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/17429763357719245487.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
92
In recent years, even though the light output of GaN-based LED continues to increase, the brightness (~20 lm/W) is still low compared to conventional lighting systems and it is necessary to further improve the light extraction of LEDs. In this study, we utilize flip-chip technique, photoresist microlenses, reflectors and thermoelectric cooler to increase the light extraction of GaN MQW LED. Electroluminescence (EL) and power angular distribution are used to measure the light output intensity of LED. From temperature dependent current-voltage (I-V-T) characteristics, the charge carrier transport mechanisms at different biased regions are also investigated. In the results, back emission of LED with SiO2/Al reflector has maximum light intensity ( 3.28μW ) , which is higher than front emission one ( 2.73μW ) in vertical emitting area ( at 90 angles). LED with P.R. microlenses (refractive index, n=1.62) on backside could improve the light extraction of LED (about 1.2 times) as well. The enhancement of light output is duo to the reduction of light absorption from the metal contact and Fresnel’s transmission losses at GaN (n=2.4)/air (n=1) interface. Finally, we fabricate a high brightness LED with above light enhancement design. EL intensity of LED is increased about 1.25 times than conventional one. Therefore, we can manufacture a LEDs array with above designs to obtain high light output for future solid-state illumination.
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CHEN, BO-HUI, and 陳柏諱. "Emission Spectrum Tunable Phosphor-Converted Light Emitting Diode Light Sources." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/zx2sws.
Full textAbstract:
碩士國立臺灣科技大學
電子工程系
104
Since plants needed different spectrum in different growth stages, the light sources of plant factory are composed of various number of blue or red LED, therefore the light source of plant factory is unable to satisfy the spec¬trum needed of the plant growth. In this study, the use of multi-wavelength excited multi-phosphor for LED packaging structure to achieve the pur¬pose of changing the emission spectral characteristics of a single LED, this re-search is proposed to provide the spectrum corresponding to different stages for plants growth. To find the best recipe of light source required, this study is divided into three parts, the first part is phosphor effi¬ciency analysis, calculating energy conversion efficiencies at the emission wave¬length of each LED die of dif-ferent phosphors and their combinations. The en¬ergy conversion characteristics of phosphor is divided into the wavelength conversion efficiency and Stokes shift loss, in addition, the inter-action between phos¬phors which can provide a criterior for the optimized combina¬tion of efficiency need. The second part is the Taguchi method analysis, this method acts a de-sign tools for choice of the combination of LED exciting wavelength and phosphors, the first purpose of Taguchi is to reduce varia¬tion, the second purpose is improve to target average, also use of Taguchi method can be used to find the optimal formula¬tions of phosphors concentration. The third part is to discuss LED light characteristic of the optimized phosphors concentration formulations, which can be divided into three con-clusions, 1.Red and blue are the most effective wavelengths for plant photo-synthesis, according to the different periods for plant growth and the different plants, therefore, the ratio between red and blue will be also different; 2.The spectrum distribution of the relative strength enables plants different phyto-chemical to absorb; 3. The full width at half maximum (FWHM) of the LED emission spectrum changes the plant absorption spectrum result in different absorption ratio for various growth state, in addition to the illumination ap-plication, the FWHM of the emission spectrum also improved color rendering characteristics.