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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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<p>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.</p>
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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 moléculaires<br>Nitride 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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Bergenek, Krister. "Thin-film photonic crystal LEDs with enhanced directionality." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/912.
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Schwab, Tobias. "Top-Emitting OLEDs." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-157992.
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In the last decades, investigations of organic light-emitting diodes (OLEDs) have tackled several key challenges of this lighting technology and have brought the electron to photon conversion efficiency close to unity. However, currently only 20% to 30% of the photons can typically be extracted from OLED structures, as total internal reflection traps the major amount of the generated light inside the devices.
This work focuses on the optimization of the optical properties of top-emitting OLEDs, in which the emission is directed away from the substrate. In this case, opaque materials, e.g. a metal foil or a display backplane can be used as substrate as well. Even though top-emitting OLEDs are often preferred for applications such as displays, two main challenges remain: the application of light extraction structures and the deposition of highly transparent materials as top electrode, without harming the organic layers below. Both issues are addressed in this work.
First, top-emitting OLEDs are deposited on top of periodically corrugated light outcoupling structures, in order to extract internally trapped light modes by Bragg scattering and to investigate the basic scattering mechanisms in these devices. It is shown for the first time that the electrical performance is maintained in corrugated top-emitting OLEDs deposited on top of light extraction structures. Furthermore, as no adverse effects to the internal quantum efficiency have been observed, the additional emission from previously trapped light modes directly increases the device efficiency. It has been proven that the spectral emission of corrugated OLEDs is determined by the interference of all light modes inside the air light-cone, including the observation of destructive interference and anti-crossing phenomena. The formation of a coherently coupled mode pair of the initial radiative cavity mode and a Bragg scattered mode has been first observed, when grating structures with an aspect ratio > 0.2 are applied. There, the radiative cavity mode partially vanishes. The observation and analysis of such new emission phenomena in corrugated top-emitting OLEDs has been essential in obtaining a detailed insight on fundamental scattering processes as well as for the optimization and control of the spectral emission by light extraction structures.
Second, the adverse impact of using only moderately transparent silver electrodes in white top-emitting OLEDs has been compensated improving the metal film morphology, as the organic materials often prevent a replacement by state-of-the-art electrodes, like Indium-tin-oxide (ITO). A high surface energy Au wetting layer, also in combination with MoO3, deposited underneath the Ag leads to smooth, homogeneous, and closed films. This allows to decrease the silver thickness from the state-of-the-art 15 nm to 3 nm, which has the advantage of increasing the transmittance significantly while maintaining a high conductivity. Thereby, a transmittance comparable to the ITO benchmark has been reached in the wavelength regime of the emitters. White top-emitting OLEDs using the wetting layer electrodes outperform state-of-the art top-emitting devices with neat Ag top electrodes, by improving the angular colorstability, the color rendering, and the device efficiency, further reaching sightly improved characteristics compared to references with ITO bottom electrode. The enormous potential of wetting layer metal electrodes in improving the performance of OLEDs has been further validated in inverted top-emitting devices, which are preferred for display applications, as well as transparent OLEDs, in which the brittle ITO electrode is replaced by a wetting layer electrode.
Combining both concepts, wetting layer electrodes and light extraction structures, allows for the optimization of the grating-OLED system. The impact of destructive mode interference has been reduced and thus the efficiency increased by a decrease of the top electrode thickness, which would have not been achieved without a wetting layer. The optimization of corrugated white top-emitting OLEDs with a top electrode of only 2 nm gold and 7 nm silver on top of a grating with depth of 150 nm and period of 0.8 µm have yielded a reliable device performance and increased efficiency by a factor of 1.85 compared to a planar reference (5.0% to 9.1% EQE at 1000 cd/m2). This enhancement is comparable to common light extraction structures, such as half-sphere lenses or microlens foils, which are typically restricted to bottom-emitting devices. Overall, the deposition of top-emitting OLEDs on top of light extraction structures finally allow for an efficient extraction of internally trapped light modes from these devices, while maintaining a high device yield.
Finally, the investigations have resulted in a significant efficiency improvement of top-emitting OLEDs and the compensation of drawbacks (optimization of the white light emission and the extraction of internal light modes) in comparison to the bottom-emitting devices. The investigated concepts are beneficial for OLEDs in general, since the replacement of the brittle ITO electrodes and the fabrication of roll-to-roll processing compatible light extraction structures are also desirable for bottom-emitting, or transparent OLEDs.
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Choi, Wai Kit. "Organic light-emitting diodes." HKBU Institutional Repository, 1999. http://repository.hkbu.edu.hk/etd_ra/190.
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Stevenson, Stuart G. "Dendrimer light-emitting diodes." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/581.
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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 Science<br>Department of Architectural Engineering and Construction Science<br>Fred Hasler<br>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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Chen, Chih-Lei. "Processing light-emitting dendrimers for organic light-emitting diodes." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489420.
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Light-emitting dendrimers with iridium(III) complex cores have given rise to some of the simplest and most efficient organic light-emitting diodes. However, whilst monochrome devices can be prepared there is currently no method for the patterning of the dendrimer films to give rise to pixelated colour displays. The main aim of this project was to develop methodology for the patterning of dendrimer films. In particular, dendrimers are designed that have an oxetane surface group that can be crosslinked to form patterns by a photo-generated acid.
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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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Young, Jung Gun. "Electroluminescent devices based on polymeric thin films." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3963/.
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This thesis is concerned with the preparation of organic light-emitting diodes (LEDs) by using different thin film technologies: the Langmuir-Blodgett (LB) technique; spin-coating and thermal evaporation. The π-conjugated polymer, poly(2-methoxy-5-(5'-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV), was used as the emissive layer and was deposited onto patterned indium-tin oxide (ITO) glass using the LB technique or spin-coating. Y-type LB films of MEH-PPV were deposited at a surface pressure of 17 mN m(^-1) with a transfer ratio of 0.95 ± 0.03. Many efforts were made to improve the LB film device performance parameters, such as external quantum efficiency and operating lifetime, by inserting an electron transporting or insulating layer between the emissive layer and top cathode. Annealing the LB films was found to result in an improved operating lifetime. LEDs based on spun films possessed higher external quantum efficiencies than devices made from LB films. The more ordered LB films had a higher probability of intra- and intermolecular interactions and formed more excimer states within the structure. This led to a lower quantum efficiency compared to devices incorporating spun films. The operating lifetime of the LEDs was highly dependent on the morphology of the film surface. A smoother film surface is required for a longer device operating lifetime. A new electron transporting material, 2,5-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl]pyridine (PDPyDP), was deposited on top of the MEH-PPV spun film. Despite a high external quantum efficiency of 0.7 %, this device suffered from dark regions in the electroluminescence output resulting in degradation of the device. The dark area formation was attributed to delamination of the aluminium electrode from the PDPyDP layer, which was lessened by: (a) annealing the degraded devices; (b) evaporating a thicker aluminium layer at a high rate and (c) inserting a buffer layer (Alq(_3)) between the PDPyDP and the Al top electrode.
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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.<br>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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Rosenow, Thomas. "White Organic Light Emitting Diodes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-67342.
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Die vorliegende Arbeit beschäftigt sich mit drei Ansätzen der hocheffizienten Erzeugung von weißem Licht mit organischen Leuchtdioden (OLEDs) auf der Basis kleiner Moleküle.
Ein Ansatz kombiniert die Emission eines fluoreszenten und zweier phosphoreszenter Emitter in einer einzelnen Emissionsschicht. Da das Triplettniveau des verwendeten Blauemitters niedriger ist als die Triplettniveaus der phosphoreszenten Emitter, werden die Konzentrationen der Emitter so gewählt, dass ein Exzitonenübertrag zwischen ihnen unterbunden wird. Die strahlungslose Rekombination von Tripletts auf dem fluoreszenten Blauemitter begrenzt die Effizienz dieses Ansatzes, jedoch besticht die resultierende weiße OLED durch eine bemerkenswerte Farbstabilität.
Der zweite Ansatz basiert auf dem “Triplet Harvesting” Konzept. Ansonsten ungenutzte Triplett Exzitonen werden von einem fluoreszenten Blauemitter auf phosphoreszente Emitter übertragen, wodurch interne Quanteneffizienzen bis zu 100 % möglich sind. Der zur Verfügung stehende Blauemitter 4P-NPD erlaubt aufgrund seines niedrigen Triplettniveaus nicht den Triplett übertrag auf einen grünen Emitter. Daher wird das “Triplet Harvesting” auf zwei unterschiedliche phosphoreszente Emitter, anhand des gelben Emitters Ir(dhfpy)2acac und des roten Emitters Ir(MDQ)2acac untersucht. Es wird gezeigt, dass beide phosphoreszente Emitter indirekt durch Exzitonendiffusion angeregt werden und nicht durch direkte Rekombination von Ladungsträgern auf den Emittermolekülen. Eine genaue Justage der Anregungsverteilung zwischen den phosphoreszenten Emittern ist durch Schichtdickenvariation in der Größenordnung üblicher Schichtdicken möglich. Spätere Produktionsanlagen brauchen daher keinen speziellen Genauigkeitsanforderungen gerecht zu werden.
Der dritte und zugleich erfolgreichste Ansatz beruht auf einer Weiterentwicklung des zweiten Ansatzes. Er besteht zunächst darin den Tripletttransfer auf den Übertrag von einem fluoreszenten blauen auf einen phosphoreszenten roten Emitter zu beschränken. Die sich ergebende spektrale Lücke wird durch direktes Prozessieren einer unabhängigen voll phosphoreszenten OLED auf diese erste OLED gefüllt. Verbunden sind beide OLEDs durch eine ladungsträgererzeugende Schicht, in welcher durch das angelegte Feld Elektron/Loch-Paare getrennt werden. Dieser Aufbau entspricht elektrisch der Reihenschaltung zweier OLEDs, welche im Rahmen dieser Arbeit individuell untersucht und optimiert werden. Dabei ergibt sich, dass die Kombination von zwei verschiedenen phosphoreszenten Emittern in einer gemeinsamen Matrix die Ladungsträgerbalance in der Emissionszone sowie die Quanteneffizienz der vollphosphoreszenten OLED stark verbessert. Als Ergebnis steht eine hocheffiziente weiße OLED, welche durch die ausgewogene Emission von vier verschiedenen Emittern farbstabiles Licht mit warm weißen Farbkoordinaten (x, y) = (0.462, 0.429) und ausgezeichneten Farbwiedergabeeigenschaften (CRI = 80.1) erzeugt. Dabei sind die mit diesem Ansatz erreichten Lichtausbeuten (hv = 90.5 lm/W) mit denen von voll phosphoreszenten OLEDs vergleichbar.
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Thomschke, Michael. "Inverted Organic Light Emitting Diodes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-106255.
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This study focuses on the investigation of the key parameters that determine the optical and electrical characteristics of inverted top-emitting organic light emitting diodes (OLED). A co-deposition of small molecules in vacuum is used to establish electrically doped films that are applied in n-i-p layered devices. The knowledge about the functionality of each layer and parameter is important to develop efficient strategies to reach outstanding device performances.
In the first part, the thin film optics of top-emitting OLEDs are investigated, focusing on light extraction via cavity tuning, external outcoupling layers (capping layer), and the application of microlens films. Optical simulations are performed to determine the layer configuration with the maximum light extraction efficiency for monochrome phosphorescent devices. The peak efficiency is found at 35%, while varying the thickness of the charge transport layers, the
semitransparent anode, and the capping layer simultaneously. Measurements of the spatial light distribution validate, that the capping layer influences the spectral width and the resonance wavelength of the extracted cavity mode, especially for TM polarization. Further, laminated microlens films are applied to benefit from strong microcavity effects in stacked OLEDs by spatial mixing of external and to some extend internal light modes. These findings are used to demonstrate white top-emitting OLEDs on opaque substrates showing power conversion efficiencies up to 30 lm/W and a color rendering index of 93, respectively.
In the second part, the charge carrier management of n-i-p layered diodes is investigated as it strongly deviates from that of the p-i-n layered counterparts. The influence of the bottom cathode material and the electron transport layer is found to be negligible in terms of driving voltage, which means that the assumption of an ohmic bottom contact is valid. The hole transport and the charge carrier injection at the anode is much more sensitive to the evaporation sequence, especially when using hole transport materials with a glass transition
temperature below 100°C. As a consequence, thermal annealing of fabricated inverted OLEDs is found to drastically improve the device electronics, resulting in lower driving voltages and an increased internal efficiency. The annealing effect on charge transport comes from a reduced charge accumulation due to an altered film morphology of the transport layers, which is proven for electrons and for holes independently. The thermal treatment can further lead to a device degradation. Finally, the thickness and the material of the blocking layers which usually control the charge confinement inside the OLED are found to influence the recombination much more effectively in inverted OLEDs compared to non-inverted ones.
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Gray, Jonathan William. "Resonant cavity light emitting diodes." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399518.
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Hemingway, Leon Robert. "Dendrimers for light emitting diodes." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325840.
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Liu, Yee-Chen. "Polymer blend light-emitting diodes." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610709.
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Fenwick, William Edward. "Metalorganic chemical vapor deposition of gallium nitride on sacrificial substrates." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/34687.
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GaN-based light emitting diodes (LEDs) face several challenges if the technology is to make a significant impact on the solid state lighting market. The two most pressing of these challenges are cost and efficiency. The development of alternative substrate technologies shows promise toward addressing both of these challenges, as both GaN-based device technology and the associated metalorganic chemical vapor deposition (MOCVD) technology are already relatively mature. Zinc oxide (ZnO) and silicon (Si) are among the most promising alternative substrates for GaN epitaxy. This work focuses on the development of MOCVD growth processes to yield high quality GaN-based materials and devices on ZnO and Si.
ZnO, because of its similar lattice constant and thermal expansion coefficient, is a promising substrate for growth of low defect-density GaN. The major hurdles for GaN growth on ZnO are the instability of ZnO in a hydrogen atmosphere and out-diffusion of zinc and oxygen from the substrate. A process was developed for the MOCVD growth of wurtzite GaN and InxGa1-xN on ZnO, and the structural and optical properties of these films were studied. High zinc and oxygen concentrations remained an issue, however, and the diffusion of zinc and oxygen into the subsequent GaN layer was studied more closely.
Silicon is the most promising material for the development of an inexpensive, large-area substrate technology. The challenge in GaN growth on Si is the tensile strain induced by the lattice and thermal mismatch between GaN and Si. A thin atomic layer deposition (ALD)-grown Al2O3 interlayer was employed to relieve strain while also simplifying the growth process. While some strain was still observed, the oxide interlayer leads to an improvement in thin film quality and a reduction in both crack density and screw dislocation density in the GaN films.
A comparison of GaN-based LEDs grown on sapphire and Al2O3/Si shows similar performance characteristics for both devices. IQE of the devices on silicon is ~32%, compared to ~37% on sapphire. These results show great promise toward an inexpensive, large-area, silicon-based substrate technology for MOCVD growth of GaN-based optoelectronic devices.
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Cheung, Chi-hang. "Fabrication and characterization of microcavity organic light emitting diodes." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B34618090.
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Cheung, Chi-hang, and 張智恆. "Fabrication and characterization of microcavity organic light emittingdiodes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B34618090.
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譚祐怡 and Yau-yee Tam. "Dual use of visible light-emitting diodes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31223436.
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Zhu, Ling, and 朱玲. "Manipulating optical emission from light-emitting diodes and their applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47297463.
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Material properties, coupled with typical device structures of GaN-based
light-emitting diode (LED) wafer give rise to Lambertian emission patterns with
large beam divergence. However, this pattern may not be useful or beneficial to
many applications. In some specific applications, such as spot lighting or light
sources for fiber coupling, emission with narrow beam divergence is required,
whereas in general lighting such as the street lamps and indoor lighting, a diffused
light source rather than a point source is needed. By manipulating the optical emission of LEDs at the chip level, some performance metrics of LEDs can be
enhanced and their applications can be extended into new fields rather than
merely for lighting. Additionally, the need for external optics can be eliminated,
thereby increasing the flexibility of design. In this thesis, five implementations
are reported to achieve emission control, namely chip design, optics design,
package design and system design, which are ordered according to the LED
fabrication process flow. Manipulation of optical emission can be observed by
comparing the proposed devices with the conventional devices, or the successful
demonstration of a new application.
By chip shaping via laser micromachining, a three-dimensional
truncated-conic LED (TC-LED) is proposed to cut off efficiently lateral emissions
from the LED sidewall, thus enhancing color uniformity from its top quantum-dot
coated surface. The optical properties of TC-LED are investigated: the beam
divergence is reduced by 32o and the power in the normal direction is enhanced by
21.7%. After applying quantum dots to achieve white-light emission, the top
emission color uniformity is improved by 37%.
By including optics on the chip level, beam divergence can be narrowed
down. The hemispherical lens LED (HL-LED) with directional beam is
proposed, achieving a 53.8% enhancement of fiber coupling efficiency. On top
of a flip-chip-packaged TC-LED, a hemispherical BK-7 lens is capillary-bonded
onto the sapphire surface. Compared with TC-LED, the divergence of HL-LED
is significantly reduced by 50o.
Vertically-mounted LED (vmLED) is proposed to broaden the emission
pattern at the packaging level. By mounting the LED die upright to expose two
large illumination surfaces instead of the traditional way of bonding the die flat
down, the optical emission pattern is converted from Lambertian to a two-lobed
pattern. Both the optical properties and thermal properties are investigated and it
is found that there is a trade-off between the heat dissipation and light output. A
sapphire-prism-mounted vmLED is further proposed to improve the heat sinking.
In the last two chapters, micro-LED arrays with smaller illuminated active
regions are introduced and the combination with external optics, including optical
fibers and projection lens sets are used to demonstrate novel LED applications.
By coupling a bi-linear micro-LED array into a fiber bundle, a portable
microdisplay system is demonstrated and this comprehensive system can be used
for image projection. Another application involved a linear UV-micro-LED
array coupled with a projection lens set; this optical system has been demonstrated
as a direct-write lithographic tool for the fabrication of polymer microlens arrays
on InGaN LEDs.<br>published_or_final_version<br>Electrical and Electronic Engineering<br>Doctoral<br>Doctor of Philosophy
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Tam, Yau-yee. "Dual use of visible light-emitting diodes /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21949001.
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O, Yin Wan. "White light organic light emitting device." HKBU Institutional Repository, 2008. http://repository.hkbu.edu.hk/etd_ra/907.
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Fang, Fang. "Investigation of green light emitting diodes." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610094.
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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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Webster, Graham R. "Advanced polymers for light emitting diodes." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393551.
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LI, KUN-LIN, and 李坤霖. "Preparation and Charaterization of Organic Light Emiting Diode for Lighting Devices." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/cvhj3v.
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碩士<br>明新科技大學<br>電子工程系碩士班<br>105<br>Organic light emitting diode (OLED) devices for the subject of Master theme are investigated, because of its high luminous efficiency, without auxiliary lamps, and surface light source, and have some advantages of light, thin, soft, high light efficiency, low heat consumption and so on. The OLED lighting devices with the natural light no injury the health condition and promote the development of the lighting industry under the significant technological transformation.
In this theme, the experimental white light OLED element is a stacked two-stage -wave type configuration in structure, and compares the influence of the light-emitting layer with different thickness on the illumination characteristics of white-light OLED. The device structure is composed of ITO / HIL / HTL / EML- (B / Y / B) / ETL / LiF / Al, i.e. the substrate, anode, cathode, electron hole injection layer and the transport layer, the material thickness, the concentration and the process parameters are fixed, while the first layer of blue light-emitting layer is modulated to be 10Å, 15Å, 20Å, and furthermore investigates the effect of the light-emitting layer with various thickness on characteristics of devices. These influential factors include the variation of the position of the electron-hole recombination region, the variation of the position of the exciton generation region, the difference in luminous intensity caused by the different current density distribution, the life time and decay rate of the OLED devices. The influential factors on optoelectronic characteristics and the related physical mechanism of organic light emitting diode lighting devices are investigated and discussed.
The experimental results show that the best device with the brightness of about 680 cd/m2, efficiency of about 15 lm/W, the color coordinates of CIE (0.32, 0.35) which is near white light, under the operation voltage of 4V. The OLED device with the optimal thickness of 15Å blue-light layer can be used more than 43,800 hours in the brightness of 1000cd/m2, which has achieved the commercial standard OLED lighting will be applied in our daily lives.
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Lee, Kuen-da, and 李昆達. "Study of bicycle traffic lights with Light Emitting Diode." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/71754099906579035008.
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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<br>元智大學<br>光電工程學系<br>104<br>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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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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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<br>國立臺灣科技大學<br>光電工程研究所<br>100<br>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<br>中原大學<br>物理研究所<br>106<br>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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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, Mau-Shang, and 張貿翔. "Top-emitting Polymer Light-emitting Diodes." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/67891518469301255707.
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碩士<br>國立成功大學<br>微電子工程研究所碩博士班<br>94<br>Recently, polymer light-emitting diodes (PLEDs) have been significantly fabricated with top-emitting architecture. The emission intensity enhancement and narrowing electroluminescence (EL) spectrum can be attributed to microcavity effects. In this thesis, a top-emitting structure was Glass/ITO/Ag(120nm)/PEDOT:PSS(40nm)/DB-PPV/Ca(10nm)/Ag, and then the device emitted light through the cathode side Ca/Ag. The polymer emissive layer was DB-PPV (2,3-dibutoxy 1,4-poly(phenylene vinylene)), which was sandwiched between two metal electrodes. One electrode was the bottom reflective anode, which was the surface modified silver film, and the
other one was the top semitransparent double-layer cathode Ca/Ag. Finally, the emitting light emitted from the semitransparent cathode under forward bias. By changing the thickness of
polymer emissive layer in the microcavity structure and the thickness of Ag in the double-layer cathode, narrower EL spectrum and enhancement of emission intensity was obtained simultaneously. By way of appropriately tuned the thickness of polymer emissive layer and
concentration, we general found that the maximum luminance efficiency in the concentration of 0.6% with spin speed of 2000rpm (65nm) and 0.7% with spin speed of 4000rpm (58nm), respectively. This was because most of the recombination or emission zone was closer to the antinode, and the normal direction luminance efficiency increased by a factor of 1.13 ~ 1.65 (2.22 to
3.25cd/A) for 0.6% and 1.01 ~ 1.79 (1.68 to 2.99cd/A) for 0.7%, respectively. Besides, the EL peak wavelength of device with a single emissive layer has a wide variation in the spectral range, from 522 to 622nm, due to the different thickness of DB-PPV. Consequently, tuned the emitting color from original yellowish green (λD=560nm) to saturated green (λD=527nm) and yellow orange (λD=582nm). The full width at half maximum (FWHM) of original EL spectra could be reduced from about 70nm to 20nm.
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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<br>國立交通大學<br>電子工程系<br>89<br>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<br>國立成功大學<br>電機工程學系碩博士班<br>93<br>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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CHANG, TUN-MIN, and 張敦岷. "Light-Extraction Enhancement of Light Emitting Diodes andOrganic Light Emitting Diodes by Photonic Crystal Structures." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/30191578760954676719.
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碩士<br>國立臺灣大學<br>光電工程學研究所<br>95<br>In this thesis, a flexible and efficient method to calculate light extraction
efficiency of light-emitting device is developed. This method is primarily
based on finite-difference time-domain ( FDTD) method aided with
Fourier analysis to obtain the intensity of the target frequency. Energy
through all angles or positions is summed up to evaluate total extraction
efficiency.
LEDs ( light emitting diodes) and OLEDs ( organic light emitting diodes)
might become one of the primary components in displays and lighting.
However, both suffer low light extraction efficiency. Considering this issue,
this thesis focuses on LED and OLED simulation. Photonic crystal
is applied to LED and OLED for light extraction efficiency improvement.
Numerous parameters are scanned within parameter bounds to evaluate
the best case and the relationship between light extraction efficiency and
each individual parameter, enabling us to understand effects of various
parameters and design considerations.
We define structure without photonic crystals an ”original structure.”
The thesis starts with ordinary rectangular structure. Furthermore, triangular,
semi-circle and circle structures are also taken into consideration.
Finally, simulation results indicate that rectangular structure in LED offers an optimal improvement at three times of the light extraction
efficiency compared with original structure, while rectangular structure
combined with flat plate in OLED offers an optimal improvement
of thirty percent in light extraction efficiency compared with original
structure.
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Ying-ChienChu and 朱盈蒨. "The Development of Micro-Light-Emitting Diode Array and the Research of Collimation, Light Extraction, and Color Conversion on Micro-Pixelated Light-Emitting Diodes." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/fzqzjy.
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博士<br>國立成功大學<br>微電子工程研究所<br>102<br>In the past twenty years, high brightness light-emitting diodes (LEDs) have achieved significant progress and advanced developments in indicators, displays and solid-state lighting. With the intrinsic material properties and low voltage operation characteristics, LEDs are an ideal candidate for many applications where performance, reliability and lifetime are critical. Due to the restriction of micro-sized process technology, LED components were only applied in the backlights of the display industries. In this dissertation, we propose an innovation to simplify the device of micro display called micro-LED technology. Small optical engine can be obtained and be suitable for the wearable device.
The optimized micro-LED process have been fabricated including mirror contact, mesa etching, passivation deposition, planarization, and black matrix integration. The yield and uniformity are modified to above 99% and 90% respectively. Preliminary ultra-compact pico-projector with micro-pixelated GaN LED imager of 80 x 60 resolution was demonstrated with the projector size of around 2 cm^3. Furthermore, the monochrome active matrix micro-sized LED chip by assembling micro-LED array and CMOS wafer through compound semiconductor process technology has also been proposed. Size and resolution of the active micro-LED array are 0.37 inches and 427 x 240 respectively. The brightness and yield of device are over 1500 nits and 99%. The micro-display is with 1,323 ppi which efficiency is around 15 lm/W within ±15 degree extraction cone under CMOS vertical scanning mode. This micro-display with the module efficiency of 21.3 lm/W/cc can not only present the static images but also dynamic videos.
Regarding the prospects of LEDs in the next generation microprojectors, higher radiation intensity and directionality of extracted light are the critical points. Further improvements of light extraction and directionality are required to reduce the optical crosstalk and enhance the projection efficiency. Although several schemes have been proposed to improve the light extraction efficiency, they only emphasized on macro-devices (i.e. regular size, ~ 100 μm or above) rather than micro-LEDs essential for micro-LED array. We have proposed three approaches as photonic crystal (PhC), micro-chip shaping (μCS), and resonant cavity to not only improve the light extraction efficiency but also enhance collimation properties on micro-LEDs. PhC based on the off-Γ diffractions performs a flat-top far-field profile in microsized thin-film LEDs. The off-Γ diffractions improve light-collection efficiency from 6.57% to 10.79% within a ±15 degree extraction cone. In addition, the light output power of the PhC micro-LED is 2.93 times than that of conventional micro-LEDs. The μCSs on the sidewall of micro-LEDs refract light rays through sidewalls into the light extraction cone and consequently improve the luminance. The maximum efficiency improvement on the μCS micro-LED array is over 45% compared with the vertical sidewall micro-LED array. Furthermore, the efficiency improvement exceeds 48% measured within ±15 degree extraction cone. Moreover, the viewing angle of 50 μm (100 μm) ultrathin-film RCLED (uT-RCLED) was near ±51 degree (±47 degree) through the beam profiler and presented the best light-collection efficiency of 8.18% (9.73%) within ±15 degree light extraction cone contrasted with regular non-DBR ultrathin-film light-emitting diodes (uT-LED) (6.57 %). In addition, the absolute light output power of the 50 μm (100 μm) uT-RCLED was 95.26% (127.36%) much higher than the uT-LEDs. These results contribute to the development of LED micro-projectors meeting a high luminance output requirement under the etendue limitation.
At last, CdSe/ZnS quantum dot (QD) and organic light-emitting polymer have been successfully incorporated with LED chip to perform wavelength transferring. The aggregation of QD and chain-conjugated of organic light-emitter polymer is modified by PMMA. The maximum color conversion efficiency of organic light-emitting polymer is also improved from 3% to around 20%. Finally, organic light-emitting polymer has been successfully ink-jet printed onto micro-LED array to perform the full color display.
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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<br>國立臺灣大學<br>光電工程學研究所<br>106<br>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<br>國立中興大學<br>物理學系所<br>106<br>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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Wei, Jung-Ting, and 魏榮廷. "Uniform illumination of Vehicle Tail Lights by Using Light-Emitting Diodes." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/374cvn.
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碩士<br>國立交通大學<br>光電科技學程<br>103<br>The modeling of automobile light has become a special design language for describing an automobile brand in the car industry. With an index significance, it is used to show a different charm. Under the leadership of international companies, a light guiding bar is widely applied to the design of car lights. However, common design methods cannot be applied to the design of car tail lights of more than 60 cm in size with a transparent sense and without highlights that visually meet the ECE Regulation No. 7.Therefore, this paper attempts to determine the best optimal design parameter combination that will address the issues mentioned.
This paper discusses the ECE Regulation No. 7, the composition of lights, specifications of a car and the principle behind the design, and the design and composition of car tail lights. LED arrangement spacing, inner surface treatment, reflecting mirror at the base, and other multiple parameters are used to attain no visual highlights. If the LED spacing is 12 mm, the test is conducted for black base accompanied by a transparent plain inner case, inner blasting, inner with white paint, and inner with diffused film. Test results shows that the evenness degree of the inner with diffused film is best at 77.5%. If LED spacing is shortened from 12 mm to 9 mm, the evenness degree of the inner with diffused film is increased by 6.71%, or 84.21% in total. After being accompanied by a reflecting mirror at the base, the average illumination of car tail lights increased by 35.6%, from 140.66 Lux to 190.77 Lux as a result of the reflecting effect of the sidewalls at the base. However, the evenness degree decreased by 11.91% from 84.21% to 72.3%.
This paper shows the optimal conditions that satisfy customer requirements are as follows: no obvious visual highlights 120˚LED, LED spacing of 9mm, inner with diffused film, and a black base. A goniophotometer is used to conduct photometric verification. Photometric results show that the brightness of partial test spots in inner with diffused plate is 17cd, which is higher than the upper limit for tail lights in the ECE Regulation No. 7. Therefore, the inner with white paint with an evenness degree lower than the inner with diffused film is used to conduct the photometric test. The results show that the photometric results of fixed side lights and fixed side lights with movable side lights can meet the photometric requirements of ECE Regulation No. 7 with regard to tail lights.
From the above results, the conditions meeting the customer’s requirements such as no obvious visual highlights, the provisions in the ECE Regulation No. 7 regarding the tail lights include 120˚LED, LED spacing of 9 mm, inner with diffused film, and black base. Car tail lights with these conditions can be approved by the automotive research &; testing center, and receive a certificate from vehicle safety certification center.
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HSU, YUEH, and 徐岳. "Modeling the diode equation with quantum wells for vertical-injection GaN-based light emitting diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/49633188571021859770.
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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.
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碩士<br>國立交通大學<br>工學院碩士在職專班半導體材料與製程設備組<br>95<br>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.
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碩士<br>國立中央大學<br>光電科學研究所碩士在職專班<br>100<br>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.