Dissertations / Theses on the topic 'LIGHT ENHANCEMENT'
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1
Lawrence, Nathaniel. "Engineering photonic and plasmonic light emission enhancement." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11114.
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Thesis (Ph.D.)--Boston UniversitySemiconductor photonic devices are a rapidly maturing technology which currently occupy multi-billion dollar markets in the areas of LED lighting and optical data communication. LEDs currently demonstrate the highest luminous efficiency of any light source for general lighting. Long-haul optical data communication currently forms the backbone of the global communication network. Proper design of light management is required for photonic devices, which can increase the overall efficiency or add new device functionality. In this thesis, novel methods for the control of light propagation and confinement are developed for the use in integrated photonic devices. The first part of this work focuses on the engineering of field confinement within deep subwavelength plasmonic resonators for the enhancement of light-matter interaction. In this section, plasmonic ring nanocavities are shown to form gap plasmon modes confined to the dielectric region between two metal layers. The scattering properties, near-field enhancement and photonic density of states of nanocavity devices are studied using analytic theory and 3D finite difference time domain simulations. Plasmonic ring nanocavities are fabricated and characterized using photoluminescence intensity and decay rate measurements. A 25 times increase in the radiative decay rate of Er:Si02 is demonstrated in nanocavities where light is confined to volumes as small as 0.01(λ/n)^3 . The potential to achieve lasing, due to the enhancement of stimulated emission rate in ring nanocavities, is studied as a route to Si-compatible plasmon-enhanced nanolasers. The second part of this work focuses on the manipulation of light generated in planar semiconductor devices using arrays of dielectric nanopillars. In particular, aperiodic arrays of nanopillars are engineered for omnidirectional light extraction enhancement. Arrays of Er:SiNx nanopillars are fabricated and a ten times increase in light extraction is experimentally demonstrated, while simultaneously controlling far-field radiation patterns in ways not possible with periodic arrays. Additionally, analytical scalar diffraction theory is used to study light propagation from Vogel spiral arrays and demonstrate generation of OAM. Using phase shifting interferometry, the presence of OAM is experimentally verified. The use of Vogel spirals presents a new method for the generation of OAM with applications for secure optical communications.
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Yang, Qingyi. "Broadband light absorption enhancement in organic solar cells." HKBU Institutional Repository, 2014. https://repository.hkbu.edu.hk/etd_oa/54.
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The aim of this thesis was to undertake a comprehensive research to study the broadband light absorption enhancement in organic solar cells (OSCs) with different nano-structures, thereby improving short-circuit current density and efficiency. Absorption enhancement in OSCs having different photonic structures, compared to the control planar cell configuration, was analyzed and studied using the optical admittance analysis and finite-difference time-domain (FDTD) method. After a brief overview of the latest progresses made in OSCs, the basic optical principles of light scattering, surface plasmon polaritons (SPPs), localized surface plasmon resonance (LSPR), diffraction effect and waveguide mode, that had been employed for light trapping in OSCs, are discussed. Optical admittance analysis reveals that light absorption in inverted OSCs, based on polymer blend layer of P3HT:PCBM, is always greater than the conventional geometry OSCs fabricated using an ITO/PEDOT:PSS anode. The inverted bulk heterojunction OSCs, made with a pair of an ultrathin Al-modified ITO front cathode and a bi-layer MoO3/Ag anode, exhibited a superior power conversion efficiency (PCE) of 4.16%, which is about 13% more efficient than a control normal OSC. It is shown that the reverse configuration allows improving charge collection at cathode/blend interface and also possessing a dawdling degradation behavior as compared to a control regular OSC in the accelerated aging test. Light absorption enhancement in ZnPc:C60-based OSCs, made with substrates having different structures, for example, surface-modified Ag nanoparticles and 1-D photonic structures, was analyzed. The effect of an ultra-thin plasma-polymerized fluorocarbon film (CFx)-modified Ag nanoparticles ii (NPs)/ITO anode on the performance of OSCs was optimized through theoretical simulation and experimental optimization. This work yielded a promising PCE of 3.5 ± 0.1%, notably higher than that with a bare ITO anode (2.7±0.1%). The work was extended to study the performance of OSCs made with CFx-modified Ag NPs/ITO/polyethylene terephthalate (PET) substrate. The resulting flexible OSCs had a relatively high PCE of 3.1±0.1%, comparable to that of structurally identical OSCs fabricated on ITO-coated glass substrate (PCE of 3.5±0.1%). The distribution of the sizes of the Ag NPs, formed by the thermal evaporation, was over the range from 2.0 nm to 10 nm. The results reveal that the localized surface plasmon resonance, contributing to the broadband light absorption enhancement in the organic photoactive layer, was strongly influenced by the size of Ag NPs and the dielectric constant of the surrounding medium. A new OSC structure incorporating a transparent PMMA/ITO double layer grating electrode was also developed. 1-D PMMA/ITO double layer grating, fabricated using nano-imprinting and low processing temperature ITO sputtering method, has a period of 500 nm. Light absorption in grating OSCs under TM, TE and TM/TE hybrid polarizations was calculated using FDTD simulation in the wavelength range from 400 nm to 800 nm. We profiled the electric field distribution and analyzed the structural requirement for confining the waveguide modes in the organic photoactive layer. The effects of the periodicity and the pitch size on light scattering, simultaneous excitation of horizontally propagating SPPs, LSPR and the waveguide modes for light harvesting in grating OSCs were analyzed. The efficiency enhancement in the grating OSCs (PCE 3.29%) over the planar control device (PCE 2.86%) is primarily due to the increase in the short-circuit current density from 11.93 mA/cm2 to 13.57 mA/cm2 (13.7% enhancement). The theoretical results agree with the experimental findings in showing that the improved performance in grating OSCs is attributed to the absorption enhancement in the active layer
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Hart, Matthew. "Optical characterization and enhancement of liquid-crystal spatial light modulators." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/14011.
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Liquid crystal spatial light modulators (LC SLMs) are used in a variety of applications including information display, optical computing and information processing, holographic data storage and adaptive optics. Only in displays, however, have they achieved widespread use outside the research laboratory. Part of the reason for this is the comparatively low optical quality of most LC modulators currently available. This thesis explores methods which can be used to characterize and enhance these devices: particularly those intended for use in non-display applications where output wavefront quality, and spatial device uniformity, can be critical. One key device parameter to be determined is the value and uniformity of the cell gap which defines the thickness of the LC layer. Surface profile measurement is also important for assessing, for example, the optical quality of reflective VLSI pixel arrays. In addition, characterization of LC response for a given input drive signal is often needed to allow prediction of SLM performance in a particular optical system. The development of methods for accurate determination of LC cell gaps is described. Broadband and multiple-wavelength interferometry are used to provide the large unambiguous measurement range necessary for absolute measurement of these micron-scale distances. One method is based on the technique of phase-shifting interferometry and allows the spatial variations to be mapped relatively quickly from a small number of interferograms acquired at different wavelengths. Techniques for reducing systematic measurement errors are discussed and demonstrated both through numerical simulation and experiment. A novel white-light interferometer configuration is also described, based on spectral analysis of white light interferograms using an imaging stationary Fourier transform spectrometer. It is shown that this configuration permits real-time visualization of spatial variations in interferometer path difference, as well as giving unambiguous depth measurements with nanometre resolution. Applications to surface profiling and to cell gap determination are discussed and experimental surface measurement results given.
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Gandhi, Keyur. "Enhancement of light coupling to solar cells using plasmonic structures." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/808845/.
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Photovoltaic technologies are likely to become one of the world’s major renewable energy generators in the future provided they are able to meet the increasing world energy demands at a significantly lower generation cost compared to conventional non-renewable energy sources. Photovoltaic systems based on 1st generation mono or poly crystalline silicon wafers have already been commercially successful over the past two decades. As the technology further develops however, it faces fundamental limits to further reduce cost which are primarily due to processing of silicon wafers. Hence, a 2nd generation of “thin film” photovoltaic systems, such as amorphous and poly silicon, CdTe and CIGS, which use cheap materials and inexpensive manufacturing processes with relatively high power conversion efficiency, have been developed. In order to commercialise the 2nd generation technology successfully, the efficiency of the thin film photovoltaic panels needs to increase to compete with the 1st generation silicon photovoltaics. Plasmonic structures provide a route to increase the efficiency of 2nd generation thin film photovoltaic devices. With the unique properties of plasmonic structures, such as ability to guide and trap light at nanometre dimensions, light absorption in the photoactive layer of thin film photovoltaic device can be increased resulting in improved device performance. In this research, plasmonic nanoparticles are utilised as an anti-reflection coating on the front side of the PV, coupling light into the active PV layer, and as scattering centres at the back reflector, increasing the path length of the light through the photoactive layer. The optical and electrical effects of the plasmonic structures are modelled simultaneously using a commercial technology computer aided design (TCAD) simulation package to understand and optimise the plasmonic effects on the performance of the 2nd generation thin film amorphous silicon, and 3rd generation organic, photovoltaic devices. The thesis describes the first ever dedicated optoelectronic model to simultaneously simulate optical and electrical properties of plasmonic thin film photovoltaics devices in collaboration with the TCAD software developer Silvaco Inc. The model demonstrates a maximum 12% relative increase in the power conversion efficiency of plasmon enhanced n-i-p configured amorphous silicon thin film photovoltaic devices. This remarkable increase in the performance is due to the light trapping in the photoactive layer of the thin film amorphous silicon photovoltaic devices, which results in improvements in the both the optical and electrical properties. Experimental work was also carried out to observe the plasmonic effects of the metal nanoparticles on the performance of 3rd generation organic photovoltaic devices which were subsequently modelled using the simulation package. A 4% relative increase in the efficiency was achieved using gold nanoparticles. A plasmonic organic photovoltaic device model and material library for the commercial organic semiconductor P3HT:PCBM, has also been developed and benchmarked experimentally. The model has assisted in the understanding of the effect of the plasmonic gold nanoparticles on the increased performance, as well as degradation effects due to the incorporation of silver nanoparticles.
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Karna, Sanjay K. "Enhancement of Light Emission from Metal Nanoparticles Embedded Graphene Oxide." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849637/.
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A fully oxidized state of graphene behaves as a pure insulating while a pristine graphene behaves as a pure conducting. The in-between oxide state in graphene which is the controlled state of oxide behaves as a semiconducting. This is the key condition for tuning optical band gap for the better light emitting property. The controlling method of oxide in graphene structure is known as reduction which is the mixed state of sp2 and sp3 hybrid state in graphene structure. sp2 hybridized domains correspond to pure carbon-carbon bond i.e. pristine graphene while sp3 hybridized domains correspond to the oxide bond with carbon i.e. defect in graphene structure. This is the uniqueness of the graphene-base material. Graphene is a gapless material i.e. having no bandgap energy and this property prevents it from switching device applications and also from the optoelectronic devices applications. The main challenge for this material is to tune as a semiconducting which can open the optical characteristics and emit light of desired color. There may be several possibilities for the modification of graphene-base material that can tune a band gap. One way is to find semiconducting property by doping the defects into pristine graphene structure. Other way is oxides functional groups in graphene structure behaves as defects. The physical properties of graphene depend on the amount of oxides present in graphene structure. So if there are more oxides in graphene structure then this material behaves as a insulating. By any means if it can be reduced then oxides amount to achieve specific proportion of sp2 and sp3 that can emit light of desired color. Further, after achieving light emission from graphene base material, there is more possibility for the study of non-linear optical property. In this work, plasmonic effect in graphene oxide has been focused. Mainly there are two kinds of plasmon effects have been studied, one is long range (surface) and short range (localized) plasmon. For long range plasmon gold thin film was deposited on partially reduced graphene oxide and for short range plasmon silver nanoparticles have used. Results show that there are 10-fold enhancement in light emission from partial graphene oxide coated with gold thin film while 4-fold enhancement from reduced graphene oxide solution with silver nanoparticles. Chemical method and photocatalytic method have been employed for the reduction of graphene oxide for the study of surface plasmon and localized plasmon. For the characterization UV-Vis spectrometer for absorption, spectrofluorophotometer for fluorescent emission, Raman spectrometer for material characterization, photoluminescence and time resolved photoluminescence have been utilized. Silver and gold nanoparticles are spherical of average size of 80 nm and 40 nm have been used as plasmons.
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Karna, Sanjay K. "Enhancement of Light Emission from Metal Nanoparticles Embedded Graphene Oxide." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc849637/.
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A fully oxidized state of graphene behaves as a pure insulating while a pristine graphene behaves as a pure conducting. The in-between oxide state in graphene which is the controlled state of oxide behaves as a semiconducting. This is the key condition for tuning optical band gap for the better light emitting property. The controlling method of oxide in graphene structure is known as reduction which is the mixed state of sp2 and sp3 hybrid state in graphene structure. sp2 hybridized domains correspond to pure carbon-carbon bond i.e. pristine graphene while sp3 hybridized domains correspond to the oxide bond with carbon i.e. defect in graphene structure. This is the uniqueness of the graphene-base material. Graphene is a gapless material i.e. having no bandgap energy and this property prevents it from switching device applications and also from the optoelectronic devices applications. The main challenge for this material is to tune as a semiconducting which can open the optical characteristics and emit light of desired color. There may be several possibilities for the modification of graphene-base material that can tune a band gap. One way is to find semiconducting property by doping the defects into pristine graphene structure. Other way is oxides functional groups in graphene structure behaves as defects. The physical properties of graphene depend on the amount of oxides present in graphene structure. So if there are more oxides in graphene structure then this material behaves as a insulating. By any means if it can be reduced then oxides amount to achieve specific proportion of sp2 and sp3 that can emit light of desired color. Further, after achieving light emission from graphene base material, there is more possibility for the study of non-linear optical property. In this work, plasmonic effect in graphene oxide has been focused. Mainly there are two kinds of plasmon effects have been studied, one is long range (surface) and short range (localized) plasmon. For long range plasmon gold thin film was deposited on partially reduced graphene oxide and for short range plasmon silver nanoparticles have used. Results show that there are 10-fold enhancement in light emission from partial graphene oxide coated with gold thin film while 4-fold enhancement from reduced graphene oxide solution with silver nanoparticles. Chemical method and photocatalytic method have been employed for the reduction of graphene oxide for the study of surface plasmon and localized plasmon. For the characterization UV-Vis spectrometer for absorption, spectrofluorophotometer for fluorescent emission, Raman spectrometer for material characterization, photoluminescence and time resolved photoluminescence have been utilized. Silver and gold nanoparticles are spherical of average size of 80 nm and 40 nm have been used as plasmons.
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Ellaboudy, Ashton. "ENHANCEMENT OF LIGHT ABSORPTION EFFICIENCY Of SOLAR CELL USING DUAL." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/672.
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In this research we study the effect of adding a single diffraction grating on top of a solar cell. We simulated the square diffraction grating, as well as triangular diffraction grating. The single square grating showed more favorable results, achieved 330% power improvement compared to 270% power improvement in the single triangular grating case.
We simulated a triangle/triangle (top-bottom) and triangular/rectangular (top-bottom) grating cases. The Triangular grating achieved higher light absorption compared to rectangular grating. The best top grating was around 200nm grating period. We realized solar cell efficiency improvement about 42.4% for the triangular rectangular (top-bottom) grating.
We studied the light transmitted power in a silicon solar cell using double diffraction triangular nano-grating. We simulated the solar cell behavior as it absorbs sunlight through its structure in various cases, results showed 270% increase of the weighted transmitted power when the top grating period (At) varies from 300nm to 800nm, and the bottom grating period (Ab) is at 500nm.
We finally studied the effect of changing the location of the diffraction gratings with respect to the solar cell. We were able to increase the light efficiency by 120%. The study showed that the power absorbed by the solar cell is not sensitive to the grating location.
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West, Charles Stanley. "Backscattering enhancement from plasmon polaritons on rough metal surfaces." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/29914.
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Dalasari, Venkata Gopi Krishna, and Sri Krishna Jayanty. "Low Light Video Enhancement along with Objective and Subjective Quality Assessment." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13500.
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Enhancing low light videos has been quite a challenge over the years. A video taken in low light always has the issues of low dynamic range and high noise. This master thesis presents contribution within the field of low light video enhancement. Three models are proposed with different tone mapping algorithms for extremely low light low quality video enhancement. For temporal noise removal, a motion compensated kalman structure is presented. Dynamic range of the low light video is stretched using three different methods. In Model 1, dynamic range is increased by adjustment of RGB histograms using gamma correction with a modified version of adaptive clipping thresholds. In Model 2, a shape preserving dynamic range stretch of the RGB histogram is applied using SMQT. In Model 3, contrast enhancement is done using CLAHE. In the final stage, the residual noise is removed using an efficient NLM. The performance of the models are compared on various Objective VQA metrics like NIQE, GCF and SSIM. To evaluate the actual performance of the models subjective tests are conducted, due to the large number of applications that target humans as the end user of the video.The performance of the three models are compared for a total of ten real time input videos taken in extremely low light environment. A total of 25 human observers subjectively evaluated the performance of the three models based on the parameters: contrast, visibility, visually pleasing, amount of noise and overall quality. A detailed statistical evaluation of the relative performance of the three models is also provided.
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Payne, David N. R. "The characterization and enhancement of light scattering for thin solar cells." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/369416/.
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Photovoltaic (PV) power is one of the most promising technologies for worldwide clean and sustainable energy production and as the technology begins to enter the mainstream the requirement for efficient use of materials becomes increasingly important. However, reducing material thickness typically lowers optical absorption, leading to lower cell efficiency. One proven method for enhancing absorption in a thin device is by texturing interfaces, typically achieved in the top transparent conducting oxide (TCO) of a thin-film design. This works by scattering transmitted light and therefore increasing its effective optical path length within the absorber layer. However, introducing rough surfaces to a PV device can lead to fabrication issues and also increases surface recombination which is detrimental to the electrical characteristics of the end device. In recent years, possible alternatives to reliance on random texturing have been found through the use of optimized diffraction gratings and the plasmonic effects of metal nanoparticles. In this work, comprehensive optical characterization has been carried out on a range of samples using traditional and novel techniques. In particular, a custom built wavelength and angle resolved scattering (WARS) measurement system has been developed and used to determine key characteristics that would remain undetected by conventional measurements. The investigation of several commercial and experimental TCO films has been carried out and clear links between topography and optical characteristics have been determined. These textured surfaces have also been modelled using finite difference time domain (FDTD) simulations which have shown good agreement with measurement results. This has allowed for further investigation of the effects of TCO topography through simulation which has revealed that scattering is best enhanced by increasing the aspect ratio of the texture rather than the overall scale. Periodic arrays of silver nanoparticles incorporated into a thin-film solar cell back-reflector design have also been extensively characterized and modelled and shown to provide scattering through both diffraction and plasmonic mechanisms, leading to an increase in useful absorption by up to 140% in comparison to a planar device.
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Palestino, Escobedo Alma Gabriela. "Biosensing and light enhancement by means of biofunctionalized porous silicon devices." Montpellier 2, 2008. http://www.theses.fr/2008MON20046.
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Wang, Huan. "Study of an Optical Enhancement Cavity for Thomson Scattering Light Sources." Thesis, université Paris-Saclay, 2020. https://tel.archives-ouvertes.fr/tel-03179872.
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Les cavités d'amélioration optique (OEC) de puissance moyenne élevée ont un large éventail d'applications, y compris la diffusion Thomson produisant des rayons X / gamma quai monochromatiques à flux moyen élevé, la génération d'harmoniques d'ordre élevé (HHG) améliorée par cavité, les interféromètres à ondes gravitationnelles, Sources de lumière de microbunching en régime permanent (SSMB) et expériences d'énergie de fusion, etc. Les travaux de cette thèse se concentrent sur les études théoriques et expérimentales des OEC de puissance moyenne élevée dédiées aux sources lumineuses diffusantes Thomson. Dans le but d'augmenter le flux moyen des photons générés par diffusion Thomson, il est demandé que le faisceau laser à l'intérieur de l'OEC ait une petite taille avec une taille de rayon de quelques dizaines de microns, une longueur d'impulsion de l'ordre de la picoseconde et une puissance moyenne intra-cavité stable de quelques centaines de kilowatts. Pour décrire précisément et efficacement le champ laser hautement focalisé à l'intérieur de l'OEC à utiliser dans les simulations de la diffusion Thomson, une expression de champ de champ laser polarisé linéairement hautement focalisé corrigé non paraxial est dérivée avec une méthode d'expansion de la série Lax généralisée. Pour supprimer les instabilités modales commencent à apparaître apparemment sur OEC avec une puissance moyenne intra-cavité atteignant ~ 100 kW qui affectent la stabilité de la cavité et pourraient conduire à une perte de verrouillage, les instabilités modales sont bien décrites avec des dégénérations de mode induites par une déformation thermoélastique de la surface du miroir caractérisée par le modèle Winkler. Nous avons évoqué la méthode du miroir en forme de D pour supprimer les instabilités modales et prouvé son efficacité par simulation. Une puissance moyenne intra-cavité stable à l'échelle horaire de 200 kW a été réalisée sur le prototype OEC de la source de lumière diffusée Thomson Thomson avec mise en œuvre de miroirs en forme de D à l'intérieur. L'analyse est effectuée pour comprendre le phénomène de chute de puissance rapide apparaissant sur l'OEC qui affecte la stabilité de la cavité et empêche la puissance intra-cavité d'atteindre l'objectif conçu. Des chutes de puissance intra-cavité sont apparues avec une ampleur et une échelle de temps en fonction du niveau de puissance. L'augmentation supplémentaire de la puissance incidente a conduit à des dommages irréversibles de la surface du miroir de couplage de cavité. L'origine de ce phénomène est étudiée par imagerie de surface de miroir post mortem et analyse des signaux transmis et réfléchis par l'OEC. La perte de diffusion induite par la déformation de la surface du miroir due à un contaminant de point chaud est très probablement la physique dominante derrière ce phénomène et le comportement de la cavité pourrait être bien reproduit par simulation. Cette analyse pourrait aider à comprendre le processus physique derrière ce type de phénomène de chute de puissance apparaissant sur l'OEC appliqué dans une large gamme d'applications et à prévenir les dommages permanents au miroir. La conception complète du prototype OEC de la source de rayons X à diffusion Tsinghua Thomson (TTX) est présentée et une expérience préliminaire est effectuée dessus, réalisant l'objectif de verrouiller un laser à injection à ondes continues avec la cavité avec le gain de cavité mesuré à 133. La conception de l'installation expérimentale haute puissance pour le prototype TTX OEC et la conception pour TTX OEC à coupler avec l'anneau de stockage d'électrons sont fourniesHigh-average-power optical enhancement cavities (OEC), have a wide range of applications including Thomson scattering producing high average flux quasi-monochromatic X/gamma-rays, cavity-enhanced high-order harmonic generation (HHG), gravitational wave interferometers, steady-state microbunching (SSMB) light sources and fusion energy experiments etc. The works of this thesis focus on the theoretical and experimental studies of high-average-power OEC dedicated to Thomson scattering light sources. With the purpose of increasing the average flux of Thomson scattering generated photons, it is demanded for the laser beam inside OEC to have small waist with radius size of few tens of microns, pulse length at the order of picosecond and stable intra-cavity average power of few hundreds of kilowatts. To precisely and effectively describe the highly focused laser field inside OEC to be used in simulations of Thomson scattering, a field expression of nonparaxial corrected highly focused linearly polarized laser field is derived with a generalized Lax series expansion method. To suppress the modal instabilities start to appear apparently on OEC with an intra-cavity average power reaching ~100 kW which affect cavity stability and could lead to lose of lock, the modal instabilities are well described with mode degeneracies induced by mirror surface thermoelastic deformation characterized by Winkler model. We brought up the D-shape mirror method for suppressing modal instabilities and proved its effectiveness with simulation. An hour-time-scale stable intra-cavity average power of 200 kW was realized on the prototype OEC of Thomson scattering light source ThomX with implementation of D-shape mirrors inside. Analysis is carried out for understanding the fast power drop phenomenon appearing on OEC which affects the cavity stability and hinders the intra-cavity power reaching the designed goal. Intra-cavity power drops appeared with magnitude and time scale depending on the power level. Increasing further the incident power led to irreversible damage of the cavity coupling mirror surface. The origin of this phenomenon is investigated with post mortem mirror surface imaging and analysis of the signals transmitted and reflected by the OEC. Scattering loss induced by mirror surface deformation due to a hot-spot contaminant is found to be most likely the dominant physics behind this phenomenon and the cavity behavior could be well reproduced by simulation. This analysis could help to understand the physical process behind this kind of power drop phenomenon appearing on OEC being applied in wide range of applications and to prevent permanent mirror damage. Full design of the prototype OEC of Tsinghua Thomson scattering X-ray source (TTX) is presented and preliminary experiment is carried out on it, realizing the goal of locking a continuous wave injection laser with the cavity with the cavity gain measured to be 133. Design of the high power experimental setup for TTX prototype OEC and the design for TTX OEC to be coupled with the electron storage ring are provided
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Zhou, Dayu. "Light-trapping enhancement in thin film solar cells with photonic crystals." [Ames, Iowa : Iowa State University], 2008.
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Harkin, David. "Fluorescence enhancement strategies for polymer semiconductors." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/267904.
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One of the major challenges in the field of organic semiconductors is to develop molecular design rules and processing routes which optimise the charge carrier mobility, whilst independently controlling the radiative and non-radiative processes. To date there has existed a seeming trade-off between charge carrier mobility and photoluminescence efficiency, which limits the development of some devices such as electrically pumped laser diodes. This thesis investigates fluorescence enhancement strategies for high-mobility polymer semiconductor systems and the mechanisms by which they currently display poor emission properties. Four independent approaches were taken and are detailed as follows. 1. Solubilising chain engineering It is shown that for the high mobility polymer poly(indacenodithiophene-co-benzothiadiazole), the addition of a phenyl- initiated side chain can enhance the solid-state fluorescence quantum yield, exciton lifetime and exciton diffusion length significantly in comparison to that without phenyl-addition. 2. Energy transfer to a highly fluorescent chromophore It is shown that for the high mobility polymer poly(indacenodithiophene-co-benzothiadiazole) efficient energy transfer to a more emissive squaraine dye molecule is possible despite fast non-radiative decay short exciton diffusion lengths. This results in a significant fluorescence enhancement, which in turn facilitates an order of magnitude increase of the efficiency of polymer light emitting diodes made from this material combination. 3. Energy gap engineering The well known Energy Gap Law predicts an increase in the non-radiative rate as the optical bandgap of an organic chromophore decreases in energy. In combination with this, almost all polymer semiconductors reported to date with high charge carrier mobility have low optical bandgaps. Therefore, molecular design principles which act to increase the optical bandgap of polymer semiconductors whilst retaining a high mobility were sought out. One specific system was successfully identified and showed a significant fluorescence enhancement compared to is predecessor poly(indacenodithiophene-co-benzothiadiazole) in both the solution and the solid state. It is found that the Frenkel exciton lifetime in this new system is a factor of four larger which also results in a significantly increased exciton diffusion length. An inter-chain electronic state is also identified and discussed. 4. Hydrogen substitution For some low-bandgap material systems such as erbium chromophores, high energy vibrational modes such as the C-H stretching mode can act as non-radiative pathways. The effect of hydrogen substitution with deuterium and fluorine was therefore investigated in a series of polythiophene derivative families. It was found that in the solid state, fluorescence and exciton lifetime enhancement occurred when the backbone hydrogen atoms were replaced with fluorine. However, evidence is given that this was not owing to the initial hypothesis, and is more likely owing to structural differences which occur in these substituted material systems.
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Dolan, Philip R. "Ultra-small open access microcavities for enhancement of the light-matter interaction." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:d949537f-cef4-4ee9-aa98-471331857a15.
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The design, construction and characterisation of a novel, arrayed, open-access optical microcavity is described. Included in this thesis are the precise fabrication details, making use of the focused ion beam. A technique for analysing and optimising the microcavities constructed, making use of an atomic force microscope is also included. Results from the optical characterisation of the fabricated microcavities are presented, including quality factors of around 104, and fitnesses of around 400. The optical analysis then progressed onto coupling colloidal semiconductor nanocrystals to the microcavity modes. This yielded room temperature Purcell enhancements, single particle sensing, and also allowed for the characterisation of a second iteration of cavities. This improved set was shown to achieve fitnesses in excess of 1800 and quality factors with a lower limit of 15000. The optical identification of single NV centres in nanodiamond is discussed, along with the development of an optical apparatus to couple them to microcavities at cryogenic temperatures. Finally several results from finite difference time domain simulations will be presented, showing ultimate mode volumes of less than 0.5 cubic wavelengths are possible for this approach.
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Smerilli, Arianna. "Enhancement of carotenoid biosynthesis and antioxidant responses in diatoms by light modulation." Thesis, Open University, 2018. http://oro.open.ac.uk/53106/.
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The ecological success of diatoms is mostly attributed to their ability to adjust biological performances to the variable environmental conditions they experience in the water column. While the efficient photoacclimative and photoprotective mechanisms in diatoms are already reported, the involvement of the antioxidant network in lowering or repairing light stress or damage is poorly understood. My thesis consists of the concomitant investigation of the photoprotective and antioxidant network functioning in the coastal diatom Skeletonema marinoi, and during an experiment at sea in the Gulf of Naples. The aims of my work are to explore the antioxidant network in diatoms to better understand its activation in coping with light variation, and the functional link between antioxidant molecules synthesis/activity and photoprotection. Results showed the spectral light dependent activity of antioxidant enzymes such as ascorbate peroxidase, catalase, and superoxide dismutase. They act in complementarity of the antioxidant molecules synthesis. A high concentration of ascorbic acid, phenolics compounds and among them flavonoids were found in diatoms. These molecules respond to light variations in terms of spectral composition, photon flux density, daily light dose, light shape distribution and photoperiod duration. Also, in a natural microalgal community, these molecules were found at high concentration following a dynamics that relied on light, nutrient stress and photosynthetic regulation. The photoprotective xanthophyll cycle, involving the pigments diatoxanthin and diadinoxanthin, is activated by light and modulated in concordance with antioxidant molecules synthesis. Indeed, under different light climates, a link between these two defense processes was found. I also show that the xanthophyll cycle pigments have a high antioxidant activity. This feature explains why they increase together with antioxidant molecules during cell senescence. More generally, the physiological state of the cells modulates the antioxidant and photoprotective network in diatoms.
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Llopis, Antonio. "Electrostatic Mechanism of Emission Enhancement in Hybrid Metal-semiconductor Light-emitting Heterostructures." Thesis, University of North Texas, 2012. https://digital.library.unt.edu/ark:/67531/metadc115113/.
Full textAbstract:
III-V nitrides have been put to use in a variety of applications including laser diodes for modern DVD devices and for solid-state white lighting. Plasmonics has come to the foreground over the past decade as a means for increasing the internal quantum efficiency (IQE) of devices through resonant interaction with surface plasmons which exist at metal/dielectric interfaces. Increases in emission intensity of an order of magnitude have been previously reported using silver thin-films on InGaN/GaN MQWs. the dependence on resonant interaction between the plasmons and the light emitter limits the applications of plasmonics for light emission. This dissertation presents a new non-resonant mechanism based on electrostatic interaction of carriers with induced image charges in a nearby metallic nanoparticle. Enhancement similar in strength to that of plasmonics is observed, without the restrictions imposed upon resonant interactions. in this work we demonstrate several key features of this new interaction, including intensity-dependent saturation, increase in the radiative recombination lifetime, and strongly inhomogeneous light emission. We also present a model for the interaction based on the aforementioned image charge interactions. Also discussed are results of work done in the course of this research resulting in the development of a novel technique for strain measurement in light-emitting structures. This technique makes use of a spectral fitting model to extract information about electron-phonon interactions in the sample which can then be related to strain using theoretical modeling.
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Li, Xing. "Efficiency droop mitigation and quantum efficiency enhancement for nitride Light-Emitting Diodes." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/395.
Full textAbstract:
In the past decade, GaN-based nitrides have had a considerable impact in solid state lighting and high speed high power devices. InGaN-based LEDs have been widely used for all types of displays in TVs, computers, cell phones, etc. More and more high power LEDs have also been introduced in general lighting market. Once widely used, such LEDs could lead to the decrease of worldwide electrical consumption for lighting by more than 50% and reduce total electricity consumption by > 10%. However, there are still challenges for current state-of-the art InGaN-based LEDs, including ‘efficiency droop’ issues that cause output power quenching at high current injection levels (> 100 A/cm2). In this dissertation, approaches were investigated to address the major issues related to state-of-the-art nitride LEDs, in particular related to (1) efficiency droop investigations on m-plane and c-plane LEDs: enhanced matrix elements in m-plane LEDs and smaller hole effective mass favors the hole transport across the active region so that m-plane LEDs exhibit 30% higher quantum efficiency and negligible efficiency droop at high injection levels compared to c-plane counterparts; (2) engineering of InGaN active layers for achieving high quantum efficiency and minimal efficiency droop: lower and thinner InGaN barrier enhance hole transport as well as improves the quantum efficiencies at injection levels; (3) double-heterostructure (DH) active regions: various thicknesses were also investigated in order to understand the electron and hole recombination mechanism. We also present that using multi-thin DH active regions is a superior approach to enhance the quantum efficiency compared with simply increasing the single DH thickness or the number of quantum wells (QWs, 2 nm-thick) in multi-QW (MQW) LED structures due to the better material quality and higher density of states. Additionally, increased thickness of stair-case electron injectors (SEIs) has been demonstrated to greatly mitigate electron overflow without sacrificing material quality of the active regions. Finally, approaches to enhance light extraction efficiency including using Ga doped ZnO as the p-GaN contact layer to improve light extraction as well as current spreading was introduced.
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Zhao, Peng. "Analysis of Light Extraction Efficiency Enhancement for Deep Ultraviolet and Visible Light-Emitting Diodes with III-Nitride Micro-Domes." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1346876941.
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Lin, Ching-Liang, and 林京亮. "Light Enhancement of Thin-GaN Light Emitting Diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/51951559488289706667.
Full textAbstract:
博士國立中央大學
化學工程與材料工程研究所
96
GaN-based materials have leaped to a brand new stage in the past two decades. The single crystalline and direct band-gap GaN film can be grown on the sapphire substrate by metal-organic chemical vapor deposition (MOCVD). The wavelength of the emitting light from GaN ranges from ultra-violate (UV) to blue light region by doping various indium content. Nowadays, the material of the blue light emitting diodes is based on the GaN material. Pumping phosphors or other wavelength converter by blue light, the white light can be generated. Hence, the GaN material is the key material for white solid-state lighting. For the solid-state lighting applications, the GaN-based LED operates under a high electric power. Under such a high operation power, the heat dissipation is a critical issue. The sapphire substrate of the conventional LED has a poor thermal conduction. Also, the degradation of the electric and optical property would be very serious due to the high operation temperature. Therefore, in this study, the thin-GaN LED device is produced by the wafer bonding process and the laser lift-off process, which are used to transfer GaN thin film from the sapphire substrate to a better thermal conductive Si substrate. Owing to the better thermal dissipation, the thin-GaN LED structure is a very promising candidate for developing high-power GaN LED. Two main topics of the studied thin-GaN LED structure in this work: (1) Design a suitable p-GaN contacts and reflector for thin-GaN LED structure. (2) Increase the light extraction efficiency of thin-GaN LED. In thin-GaN LED process, the wafer bonding process is necessary and it is a high temperature and high pressure process. Furthermore, the Si substrate is a non-transparent material for the blue light region. So, the p-type GaN contact should consist of an ohmic contact layer and a reflector as well. It is very important to develop a high thermally stable p-GaN contact. In this study, the Ni/Au/Ni/Al p-GaN contacts and Ni/Ag(Al) p-GaN contacts are investigated. These two thermally stable p-GaN contacts can reduce the degradation of the specific contact resistance and the reflection upon the thermal process. The specific contact resistance of the Ni/Au/Ni/Al p-GaN contact keeps on the order of 10-2 Ω-cm2 after 500 ℃ annealing. The reflectance of the Ni/Au/Ni/Al metal scheme is 60 % after 500 ℃ annealing. This high thermally stable Ni/Au/Ni/Al p-GaN contact is very suitable for the thin-GaN LED structure. Another critical issue is the low light extraction efficiency due to large refraction index difference between GaN and air. The light emitted from the active layer in GaN is significantly trapped in the GaN epi-layer, and a serious total internal reflection occurs. In this study, the aluminum oxide and silicon oxide honeycomb structure are produced on the n-GaN emitting surface by poly-styrene spheres template and sol-gel method. The aluminum oxide and silicon oxide honeycomb structures capping on the n-GaN surface can increase the external quantum efficiency by 35 % and 19 %, respectively. The mechanism of increasing light out-put by the oxide honeycomb structure would be discussed.
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顧浩民. "Light extraction enhancement for LED having periodically corrugated enhancement structures." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/26891315863065011647.
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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, Zhou-Chi, and 陳肇祈. "Light Extraction Enhancement of Light Emitting Diodes by the Pulse Laser." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/gcqy7d.
Full textAbstract:
碩士中原大學
機械工程研究所
99
In this study, pulsed lasers were used to fabricate micro/nano structures on the transparent conducting oxide (TCO) layers of the light emitting diodes (LEDs) to destroy the total internal reflectionat TCO/air and enhance the light extraction efficiency. The formation of laserinduced periodic surface structures (LIPSS) depends on the pulsed duration. For nanosecond laser, LIPSS was attributed to the interference of surface scattering wave and incident laser, but second harmonic wave generated from the interference of surface scattering and surface plasma induces ripples for the femtosecond laser. This study showed that light-emitting efficiency increases with surface roughness by femtosecond laser, and achieved an improvement of 16.46 %. But the forward voltage is also higher through femtosecond laser processing, meaning the laser fluence damaged the p-GaN. However, light output power enhanced to 24% and the forward voltage was not changed after nanosecond laser processing, this showed that flat-top beam of nanosecond laser was only fabricate ripple structure but not damaged the electrical property of LED.
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Tang, Kuo-Liang, and 湯國樑. "Enhancement in Light Extraction Efficiency of AlGaInP Light-Emitting Diodes (Amber)." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/89226214193013393107.
Full textAbstract:
碩士國立中興大學
精密工程學系所
98
The brightness of a LED is determined by its radiant efficiency, i.e. the multiplication of the internal quantum efficiency and the external quantum efficiency. Even though the internal quantum efficiency of high quality LEDs with double hetero junction can reach as high as 99%, it is still very difficult to achieve an external quantum efficiency higher than 10%. This thesis studies the potential methods for increasing the external quantum efficiency of LEDs, including the roughening of the window layer and applying various patterns on the mirror layer; the patterns applied on the mirror layer are disordered roughening, ordered array, and regular flat surfaces, respectively. The experimental data show that the light emitting angle measured in full width half maximum (FWHM) of these specially-treated AlGaInP LEDs can vary from 12° reduction to 14° enhancement as compared to that of the traditional LEDs with flat window layer and flat mirror. The statistically averaged radiant efficiency of LEDs with rough window layer and flat mirror is 1.45 times that of traditional LEDs. However, the statistically-averaged radiant efficiency of LEDs with rough window layer and patterned mirror can only reach up to 1.38 times that of traditional LEDs. These results demonstrate that the patterned mirror can indeed change the radiant efficiency, but the patterns used in this study are not effective enough to increase the LED radiant efficiency. This might be due to the facts that an optimal mirror pattern has not been found or the itching process has reduced the mirror surface flatness, causing diffused scattering, trapping and absorption of the photons within the LEDs. If an optimal and higher quality patterned mirror can be designed and fabricated with the assistance of theoretical simulations, it should be possible to raise the radiant efficiency of LEDs.
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Hsieh, Hsien-Ming, and 謝憲明. "Light extraction enhancement for Light-Emitting Diodes by Wafer Transfer Technologies." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/37325592403232883811.
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Alizadeh, Mohammadhossein. "Plasmonic enhancement of chiral light-matter interactions." Thesis, 2016. https://hdl.handle.net/2144/14539.
Full textAbstract:
Plasmonic nanostructures provide unique opportunities to improve the detection limits of chiroptical spectroscopies by enhancing chiral light-matter interactions. The most significant of such interaction occur in ultraviolet (UV) range of the electromagnetic spectrum that remains challenging to access by conventional localized plasmon resonance based sensors. Although Surface Plasmon Polaritons (SPPs) on noble metal films can sustain resonances in the desired spectral range, their transverse magnetic nature has been an obstacle for enhancing chiroptical effects. We demonstrate, both analytically and numerically, that SPPs excited by near-field sources can exhibit rich and non-trivial chiral characteristics. In particular, we show that the excitation of SPPs by a chiral source not only results in a locally enhanced optical chirality but also achieves manifold enhancement of net optical chirality. Our finding that SPPs facilitate a plasmonic enhancement of optical chirality in the UV part of the spectrum is of great interest in chiral bio-sensing. Next we focus on the new concepts of transverse spin angular momentum and Belinfante spin momentum of evanescent waves, which have recently drawn considerable attention. We investigate these novel physical properties of electromagnetic fields in the context of chiral surface plasmon polaritons. We demonstrate, both analytically and numerically, that locally excited surface plasmon polaritons possess transverse Spin angular momentum and Belinfante momentum with rich and non-trivial characteristics. We also show that the transverse spin angular momentum of locally excited surface plasmon polaritons leads to the emergence of transverse chiral forces in opposite directions for chiral objects of different handedness. The magnitude of such a transverse force is comparable to the optical gradient force and scattering forces. This finding may pave the way for realization of optical separation of chiral biomolecules
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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.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
95
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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Chih-ChienLin and 林志堅. "Investigation of light output extraction enhancement in GaN-based light emitting diodes." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/28749446707170459089.
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Guo, Bingchang, and 郭秉昌. "Light Extraction Enhancement of Light-Emitting Diodes based on Circular Photonic Structures." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/69004783119833990700.
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Chang, Wei-En, and 張維恩. "Light Extraction Enhancement of AlGaN-based Ultraviolet-C Light-Emitting Diodes device." Thesis, 2019. http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107NCHU5159051%22.&searchmode=basic.
Full textAbstract:
碩士國立中興大學
材料科學與工程學系所
107
In this study, Ultraviolet C Light Emitting Diodes (UV-C LEDs) were used in epitaxial structure on sapphire by Metal Organic Chemical-Vapor Deposition (MOCVD) system. The SiO2/Al reflectors were coated on the inclined sidewalls of the active mesa stripes upon the shape of finger electrode (pin) by using the Flip-Chip process of typical photolithography(i.e., the optical path from the active layer toward the sapphire substrate). In addition, P-type gallium nitride (p-GaN) epitaxial film thickness changed 50 nm for 150 nm with surface texture of the active mesa stripes were formed on the inclined sidewalls by using electrochemical etching. Transverse Electric mode (TE mode) and Transverse Magnetic mode (TM mode) were investi-gated by using the Integrating sphere (IS), X-ray diffractometer (XRD), Scanning Electron Microscope (SEM), and polarization-dependent Electroluminescence (EL). The effect of the light extraction efficiency (LEE) were investigated in various num-ber of active mesa stripes、angles of the inclined sidewalls, and thickness of the p-GaN layer. According to the result of experiment、2D-DDCC simulation, and ray tracing measurement, the result in current crowding due to increasing the contact resistance of the ITO and resistance of the p-GaN layer, which contribute to the side-wall-emission-enhanced UV-C LED breaks through the fundamental limitations caused by the intrinsic properties of AlGaN, thus shows a remarkable improvement in light output power by 40% result from total internal reflection, which improves the LEE of TM mode compare with the 5pin 75o inclined sidewalls. On the other hand, the 25pin 30o inclined sidewalls enhanced the LEE of TE mode and TM mode due to increasing the light escape rate.
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Chen, Guan-Chen, and 陳冠辰. "Performance Enhancement of DMFCs with Light Current Collectors." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/88211545034095401826.
Full textAbstract:
碩士國立勤益科技大學
冷凍空調系
100
In this study, the performance of four different Direct Methanol Fuel Cells with current collectors utilizing different materials as subtract was investigated under various operating temperatures. Subtracts of the current collectors were stainless steel, fiberglass and PDMS (polydimethylsiloxane) respectively. The electric conductive boards on subtracts of fiberglass and PDMS were fabricated by thermal plating with gold. It was found that the performance of the DMFC with PDMS as subtract was the worst among the DMFCs under the same operating conditions. The maximum power density of the DMFC was only 2.253 mW•cm-2. However, for the DMFC with stainless steel as subtract, the performance of the fuel cell was the best among the DMFCs, and the maximum power density of the DMFC was 13.945 mW•cm-2. Furthermore, by adding some platinum catalyst on the surface of PDMS fuel channel, the performance of the DMFCs can be seriously enhanced. In the case of the DMFC with fiberglass as subtract, almost 282% of performance enhancement percentage can be reached for the DMFC with 2.0mm channel width and in the operating temperature of 30℃.
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Chen, Kuei-Ting, and 陳奎廷. "Efficiency Enhancement Technologies for InGaN Light Emitting Diodes." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/08172457979863026957.
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Chen, Yi-Hong, and 陳奕宏. "Enhancement the Performance of AlGaInP Light-Emitting Diodes." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/08024195767411973569.
Full textAbstract:
碩士國立交通大學
材料科學與工程系所
96
In this thesis, the AlGaInP epi layer was successfully transferred from GaAs to diamond substrate by wafer bonding technology at first. Then the light-extraction efficiency was also increased by metal mirror reflector. The results of the experiments showed that the saturation current of diamond-light emitting diodes (LEDs) was increased. Therefore, the issue of joule-heat effect was solved by using diamond substrates because of the better heat conduction diamond substrates have. This allows the diamond-substrate LED with mirror system to operate a current up to 350 mA and a peak luminous intensity of 1849 mcd. The improvement of the light-extraction efficiency was due to the surface roughening and metal reflector. As the light driven by multi-quantum well passed through the boundary of air and LED, the rougher surface can decreased the probability of the total reflection. Therefore, the light-extraction efficiency was improved. A structure with p-roughed AlGaInP LED on GaAs substrate was fabricated by wet etching. The luminous intensity of LED was enhanced 57.4% at an injection current of 20 mA after wet etching 1 minute. A structure with p-roughed AlGaInP LED on silicon substrate was fabricated by wet etching, mirror system and wafer-bonding. The luminous intensity of LED with 3µm wet etching pattern was enhanced 53.5% at an injection current of 20 mA. Moreover, the forward voltage was decreased slightly because the augmentation of contact area. A structure with double-roughed AlGaInP LED on silicon substrate was fabricated by wet etching, mirror system, wafer-bonding and ICP dry etching. The luminous intensity was decreased after ICP dry etching. We do not know the reason exactly right now. Moreover, the forward voltage was increased because the debasement of current spreading and damage to the epi layer.
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Lee, Min-i., and 李旻怡. "Photodetector - Light Harvesting and specific surface Enhancement (LivE)." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/zec6tj.
Full textAbstract:
碩士國立中央大學
材料科學與工程研究所
103
Nanorods of zinc oxide (ZnO) suitable for making of photodetectors and dye-sensitized solar cell (DSSC) were prepared by means of chemical bath deposition (CBD) method in this work. For making photodetectors, the ZnO nanorods were deposited on silicon substrate; whereas for making of photovoltaics, the ZnO nanorods were deposited on the glass of indium-tin oxide (ITO). On the purpose to develop the nanorods with high aspect ratio, large specific surface area and good alignment of matrices suitable for light trapping and harvesting, the conditions of the CBD should be carefully controlled. This work comprised three parts: the first one focused the conditions to prepare ZnO nanorods those are qualified enough for making the photodetectors and photovoltaics. The second is the preparation of photodetectors from a concept of the heterojunction between an n-type ZnO and the p-type Si based, and the photodetection was also demonstrated to check the detectors. The third part was to construct the ZnO-based photovoltaic devices, a simple Grätzel type solar cell (DSSC), and the demonstration to test their performance. The performance of the proto-type photodetectors and photovoltaics indicated that ZnO nanorods prepared by CBD in this work were satisfactory for their use in the devices. Another interest was to prepare the transparent conductive oxide (TCO) films of ZnO (doped with aluminium and tin) by sol-gel dip-coating process. This was a trial to replace ITO-coating on the glass for a concept with overall oxide-devices on the base of simple ZnO. Unfortunately, even the optical transparency was competitive; the electrical conductivity of the Al, Sn-doped ZnO films was inferior to ITO. Therefore, the preparation and characterization of Al, Sn-doped ZnO films were put in the appendix.
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Yueh-YuHung and 洪玥煜. "Study on Light-Output Enhancement of Light Emitting Diodes by Etching process technology." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/55624725452395589766.
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碩士國立成功大學
微電子工程研究所碩博士班
98
In this thesis, we use two methods of fabrication-process to improve light-output of Light emitting diodes. The first part is to fabricate a surface-textured AlGaInP light-emitting diodes coated with transparent AZO thin film which is produced by wet etching treatment with hydrochloric acid. At 20 mA, the light output power of the AlGaInP LED coated with surface-textured AZO thin film is enhanced by ~117.43% compared with the conventional LED. The enhanced light output power is attributed to the improved extraction efficiency resulting from an overall decrease in the total internal reflection due to the AZO thin film and increased surface roughness that causes angular randomization of the photons. The second part is to fabricate a selective high barrier region (SHBR) with inductively coupled plasma (ICP) etching that induces an increase of series resistance in p-type GaN. The plasma exposed area revealed higher resistivity in conjunction with an increased barrier height. We attribute this phenomenon to a combination of two mechanisms, one of which is the nitrogen vacancies, acting as donors for electrons were produced at the etched surface, resulting in a shift of the Fermi level moves away from the valence band maximum edge. The second mechanism is the ICP-induced Ga dangling bonds, which would adsorb oxygen from the ambient. Those leads to the rised in contact resistivity through the increase of the Schottky barrier for the conduction of electrons. Thus , the current blocking layer is simply developed below the p-pad electrode of the GaN-based light-emitting diodes (LEDs). The light-output power for the LED chip with a SHBR is significantly increased by 12% as compared with the conventional LED chip. The enhancement in the light-output power can be explained for the additional current injection into the effective active layer area of the LED by the SHBR structure and a reduction in optical absorption under the p-pad electrode.
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Yang, Yuan-Lin, and 楊元霖. "Observation of Light-Induced Enhancement in Organic solar cells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/80086331091395725276.
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碩士國立清華大學
電子工程研究所
98
In this work, we demonstrated a high-performance and long-lifetime inverted polymer solar cell employing PBD as electron transport layer. The active layer was a bulk heterojunction (BHJ) consisting of blending of poly(3-hexylthiophene)(P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in 1, 2-Dichlorobenzene, with the inverted device structure：ITO / PBD / P3HT:PCBM / PEDOT / Ag. We discovered the performance of the device became better though continuous measuring the device. Eliminating reasons by many aftertreatments, the only method found to greatly enhance the performance is continued light soaking the device by using the solar simulator. After continuous light soaking two hours, this approach improves the short-circuit current from11.70mA/cm2 to 13.10mA/cm2, open-circuit voltage from 0.32V to 0.61V, fill factor from 0.29 to 0.60, and power conversion efficiency from 1.11% to 4.79%.(AM1.5G 100 mW/cm2) We also traced lifetime of the device, all devices were encapsulated and stored in an ambient atmosphere. The device using Cs2CO3 with deterioration more than 50% after 25 days, but the device using PBD increased slightly at first 16 days then decreased slowly. After 41 days the PCE maintained the same as fabricated. The lifetime of devices with PBD as ETL is much longer than those with Cs2CO3 as ETL.
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Wang, Szu-Chieh, and 王思傑. "Extreme Low Light Image Enhancement with Generative Adversarial Networks." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/cz8pqb.
Full textAbstract:
碩士國立臺灣大學
資訊工程學研究所
107
Taking photos under low light environments is always a challenge for current imaging pipelines. Image noise and artifacts corrupt the image. Tak- ing the great success of deep learning into consideration recently, it may be straightforward to train a deep convolutional network to perform enhance- ment on such images to restore the underlying clean image. However, the large number of parameters in deep models may require a large amount of data to train. For the low light image enhancement task, paired data requires a short exposure image and a long exposure image to be taken with perfect alignment, which may not be achievable in every scene, thus limiting the choice of possible scenes to capture paired data and increasing the effort to collect training data. Also, data-driven solutions tend to replace the entire camera pipeline and cannot be easily integrated to existing pipelines. There- fore, we propose to handle the task with our 2-stage pipeline, consisting of an imperfect denoise network, and a bias correction net BC-UNet. Our method only requires noisy bursts of short exposure images and unpaired long expo- sure images, relaxing the effort of collecting training data. Also, our method works in raw domain and is capable of being easily integrated into the ex- isting camera pipeline. Our method achieves comparable improvements to other methods under the same settings.
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MUPPARAPU, RAJESHKUMAR. "Absorption Enhancement by Light Scattering for Solar Energy Applications." Doctoral thesis, 2013. http://hdl.handle.net/2158/796858.
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In this thesis, I discuss few novel approaches to enhance the light-matter
interaction, which have applications in solar energy. Enhancement of absorption/
fluorescence is a topic of immense interest in recent years for its importance
in various fields: bio-sensing and diagnostics, solar energy, imaging,
forensics, etc.. Often, applications involving fluorescence are quite low efficient,
and which is mainly attributed to poor fluorescence from constituent
fluorescent molecules. Enhancing fluorescence of molecules can enable to
realize very efficient applications. And, one such application which needs
attention is Luminescent solar concentrator, which is a main topic of discussion
in this thesis. Luminescent solar concentrators (LSCs) are polymer
slabs filled with fluorescent molecules which absorb incoming sunlight and
emit fluorescence inside the slab, and which is partially guided to the edges
where photovoltaic cells are attached. Poor absorption/fluorescence of organic molecules is due to their intrinsic chemical structure, due to which either they display huge non-radiative decay
losses or poor absorption efficiency, etc.. It is well know that the amount of
light emitted by molecules also depends on their surrounding medium properties.
Modifying the surrounding environment very close to the molecules
can actually modify the intrinsic fluorescence properties of molecules. This
idea has been applied quite a lot to modify the properties of molecules close
to metallic nanostructures/nanoparticles. When it comes to enhance the
fluorescence of molecules embedded in polymer slabs like LSCs all existing
approaches fail to work. In thesis, I discuss elaborately, in particular answering
following questions: why existing approaches fail to work, essentially
what kind of approaches are needed, and how they should be implemented.
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Su, Chiu-Yen, and 蘇秋燕. "The study of enhancement of luminous efficiency of blue light organic light emitting diode." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/v8q948.
Full textAbstract:
碩士崑山科技大學
電機工程研究所
92
The blue light organic light emitting diode (blue OLED) plays an important role in the full-colorization of plat-panels. Thus, the key point of this study is to discuss the way we improve the efficiency of the blue OLED. The greatest progression of this study is that we lower down the turn-on voltage (from 10V to 3V) and promote the luminance and efficiency. In this study, we discuss five major topics of blue light device structure respectively: (1) We take TPD as a hole transport layer and evaluate the effects when adjusting the parameters. (2) We discuss the effect of different ITO sheet resistance and plasma clean. (3) We consider the effect of different organic materials. (4) We consider the effect of adding Teflon buffer layer. (5) We discuss the effects when adjusting the blue light doped parameters. Finally, we find the best structure we promoted in this study: Double spaced quantum well doped structure with doped thickness 0.3 nm (and concentration 2.91%), the luminous efficiency and luminance yield is 3.2 lm/w and 4.5 cd/A (@ 5 mA/cm2) and the luminance attain to 2040 cd/m2 (@ 8V).
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Yen, Chia Chun, and 顏家駿. "Effects of nanostructured photonic crystals on light extraction enhancement of nitride light-emitting diodes." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/19766633492780920030.
Full textAbstract:
碩士長庚大學
光電工程研究所
98
The light extraction efficiency of an InGaN/GaN light-emitting diode (LED) can be enhanced by incorporating nanostructured photonic crystals inside the LED structure. In this paper, we employed plane wave expansion (PWE) method along with finite difference time domain (FDTD) method to reveal the optical confinement effects with the relevant parameters, such as periodicity arrangement and dielectric constant. The results showed that bandgap modulation could increase the efficiency for light extraction with the air-hole periodicity of 200 nm and depth of 200 nm. Focused ion beam (FIB) of Ga was used to create the desired nanostrucured patterns. The technique provides one-step patterning and is adaptable to complicated patterns when compared with other methods. The device micro-PL (photoluminescence) results have demonstrated that the photonic crystal structures could increase the LED peak illumination intensity by 60%. The peak wavelength remained unchanged. As the ratio of the patterned area was optimized to 85%, the peak intensity improvement was further achieved at 90%. A threefold enhancement in the integrated light extraction efficiency was thus accomplished. The experimental details would be presented and discussed.
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Deng, Zih-Teng, and 鄧資騰. "Enhancement of Visible Light Photocatalytic Efficiency Using Light Emitting Diode and Bismuth/Titanium Dioxide." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/20600636742994649682.
Full textAbstract:
碩士國立屏東科技大學
環境工程與科學系所
100
The adventages of using light emitting diodes (LED), a new generation of light source, lead to the global lighting revolution including its light weight, small size, long life, low power consumption, shock resistance, and good monochromaticity. LED research and application gain a great deal of attention. In recent years, the photocatalysts are mainly used on environmental protection research. However, the most widely used photocatalyt is titanium dioxide (TiO2). The sol - gel preparation of TiO2 composed with defferent amounts of bismuth (Bi), to form pure TiO2, 0.1%-Bi/TiO2, 0.5%-Bi/TiO2, 1.0%-Bi/TiO2, 3.0%-Bi/TiO2, 5.0%-Bi/TiO2, and 10.0%-Bi/TiO2. Bismuth was applied to enhance the photocatalytic capacity to improve the visible light absorption, and to further explore the treatment of methylene blue and PCBs aqueous solution. The results of Bi/TiO2 investigation can really enhance the visible light absorption. The XRD analytical results were used to compare the JCPDS authentication database used in this study to comfirm the crystal types of TiO2. The findings of SEM tests showed the addition of bismuth is capable of increasing the light absorption of TiO2. The optimum operating conditions of photodegradation test results were using 1.0%-Bi/TiO2, 400 ℃, pH = 4.0 under natural sunlight. The degradation percentages of PCBs were up to 60.93 %, and 12.87 % of mineralization. The IC analysis found that with increasing illumination time, the yield of Cl- was increased. PCBs concentration decreased with increasing illumination times. This phenomenon may be caused by bismuth and titanium dioxide calcination that changed the lattice type of TiO2 and to lower its energy gap. The results of this study found that the Bi-doped TiO2 photocatalyst can effectively improve the photocatalytic activity under visible light radiation. The LED light source can be expected to use on photocatalytic research in the future because LED light is more in line with its economic benefits compared to other light sources.
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Hsu, Cheng-wei, and 徐誠偉. "Light extraction electroluminescence efficiency enhancement of GaN light-emitting diodes by circular photonic crystal." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/12534401667425063568.
Full textAbstract:
碩士國立中正大學
物理學系暨研究所
101
In this work, we demonstrate the enhancement of light extraction efficiency of GaN light–emitting diodes (LEDs) by circular photonic crystal (CPC) structures. The parameters were considered including: the distance between two neighbor circles (d), etched depth and filling ratio. In experiment, focused ion beam lithography was employed to directly pattern the optimal CPC structure onto the emitting surface of GaN-based LEDs. The electroluminescence intensity of this CPC LED is enhanced up to 7 times, compared to a normal LED without patterning the CPC structure.
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Hsieh, Cheng-en, and 謝承恩. "Light output efficiency enhancement of InGaN-Based Light Emitting Diode by Photoelectrochemical (PEC) Technique." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/28158108680730203604.
Full textAbstract:
碩士國立交通大學
光電工程系所
96
The enhancement of light extraction efficiency of InGaN-based light emitting diodes has fabricated and studied by photoelectrochemical wet etching/oxidation in the thesis. The fabricated InGaN-based LED structures are treated through micro-hole array process and photoelectrochemical (PEC) wet oxidation and etching process using Hg lamp illumination and DI water or KOH solution. We study the influence of photoelectrochemical (PEC) oxidation and etching methods on micro-hole array LED structures. In this study, two ways were used to increase the light extraction efficiency. Firstly, micro-hole array patterning structure was fabricated on the broad area LED structures. It can increase light extraction efficiency from the sidewall area of multiple quantum wells (MQWs). Secondly, photoelectrochemical (PEC) oxidation and etching methods were applied to the micro-hole LED structures. PEC process on GaN/ LED can decrease total reflection angle between GaN and air and also has surface roughness effect on GaN material. Compared with the conventional broad-area LED structure, micro-hole array LED structure has larger GaN and InGaN surface area. It increases PEC oxidation and etching area on LED structures. Theoretically, The more oxidation or etching area, the higher light extraction efficiency increases. We combined micro-hole array structure and photoelectrochemical methods performed on the conventional broad-area structure to increase light extraction efficiency. PEC oxidation is used to form oxidation layer and increase surface roughness on the micro-holes array sidewall surface. After PEC oxidation process, the micro-hole array LEDs were performed L-I-V, SEM , AFM, and beam-view image measurement. Comparing with the conventional broad-area LEDs, the experiment results show that the light output power of micro-hole array LEDs and 10min PEC-oxidized micro-a array LEDs have increase of 1.38 and 1.82 times at bias current of 20mA, respectively. PEC KOH roughening is only used to increase surface roughness on the micro-holes array sidewall surface. After PEC oxidation process, the micro-hole array LEDs were performed L-I-V, SEM , AFM, and beam-view image measurement. Compared with conventional broad-area LEDs, micro-hole array LEDs with 5min PEC KOH roughening has a increase of 1.51 times at a bias current of 20mA GaN thin-film vertical LED is fabricated by photoelectrochemical oxidation method. GaOx film about 100nm thickness is successively deposited on n-GaN surface. Compared with thin-film vertical LED without GaOx film, 36% light output power increases at 100mA.
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Chan, Kuei-Cheng, and 詹貴丞. "Enhancement of Light Output in Flip-Chip Light-Emitting Diodes by Patterned Sapphire Surface." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/24916124757818650642.
Full textAbstract:
碩士崑山科技大學
光電工程研究所
100
Nitride-based high-power flip-chip light emitting diode （FC LED） with patterned sapphire surface （PSS） was proposed and realized. The generated light in the active layer is mostly absorbed by the gradually disappears due to total internal reflection . It is therefore very important that the photons generated from LEDs experience multiple opportunities of escaping to improve the light extraction efficiency. We use the of 0, 30, 60, 120 minutes different dry etching time, compare the optical and electrical properties and observe the graphic changes. Under 350 mA current injection, it was found that output powers were 460 and 491 mW for the conventional FC LED and FC LED with patterned sapphire surface, respectively. In other words, we can enhance the light output power by 10% without increasing operation voltage of the fabricated LED. The enhancement efficiency can be simulated and the simulated results showed the same trend as the results of experiment.
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Cheng, Cheng-Hsin, and 鄭政欣. "Enhancement in Light Output of GaN-based Light-Emitting Diodes with Omni-Directional Reflectors." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/74510736220659570468.
Full textAbstract:
碩士國立臺北科技大學
光電與能源產業研發碩士專班
99
In this study, TiO2/SiO2/Ag Omni-Directional Reflectors（ODRs）were deposited on the backside of the sapphire substrate of the GaN-based lighting-emitting diodes (LEDs) by radio-frequency reactive magnetron sputtering deposition, to avoid loss of light from the back of components to enhance the efficiency of light emitting diodes. This experiment is based on sputtering power, Ar air flow, and time. Deposit 1, 3, and 5 pairs of TiO2/SiO2/Ag ODRs on the backside of the sapphire substrates of the GaN-based LEDs and the glass substrates to make it become an experimental sample. The exact time of the deposits and the thickness should be TiO2：110 minutes/55nm、SiO2：20 minutes /80nm、Ag：3 minutes/75nm. The reflect spectrum measure the deposition on the glass substrates of 1, 3, and 5 pairs of TiO2/SiO2/Ag ODRs and they are about 460nm. It shows that the reflection is about 85~96%. It shows that the TiO2/SiO2/Ag ODRs have great effect on the reflection of the GaN-based LEDs luminescence band. The last step is to measure the L-I of the GaN-based LEDs’s electric quality. Use five pairs of TiO2 / SiO2 / Ag ODRs and traditional GaN-based LEDs which have been increase about 61% on the 20mA. This proves that the TiO2 / SiO2 / Ag can improve GaN-based LEDs light efficiency.
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Sheng-Chih, Hsu. "Blur Effect and Light Efficiency Enhancement of Organic Light-Emitting Devices by Using Microstructure Attachment." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2607200618125500.
Full text
47
Lee, Ya-Ju, and 李亞儒. "Research on Light Emission Enhancement of III-V Light- Emitting Diodes by Surface Modified Techniques." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/taa9tg.
Full textAbstract:
博士國立交通大學
光電工程系所
96
Light-emitting diodes (LEDs) are revolutionizing the world. Due to the unique characteristics of III-V compound semiconductor that provides the direct transfer of electrical energy into light, LEDs have been forecasted as lighting sources of next generation. However, efficiency of present state-of-the-art visible-spectrum LEDs are still low, as compared to that of conventional lighting sources specifically applied for high-flux utilization. In addition, since concerns of energy-conservation and environment-protection become emergent over the world, the desire for more sophisticated and high-efficiency LEDs structure’s designs is even intense than ever. In the first section of this thesis, we design a novel structure to simultaneously enhance both internal quantum efficiency and light extraction efficiency of InGaN-based LEDs. For InGaN-based LEDs, in addition to the total internal reflection restricting photons extraction, the major difficulty is the lack of low-cost, single-crystal GaN to use as a growth substrate. Thus bunches of dislocation defects are normally observed inside active regions and served as nonradiative recombination centers. To alleviate these issues, we propose a novel structure of InGaN-based LEDs grown on chemical wet etching-patterned sapphire substrate (CWE-PSS) for simultaneously enhancing both internal quantum and light extraction efficiencies. The detail of physical mechanisms responsible for the dual enhancement in internal quantum efficiency and light extraction efficiency are also investigated in this thesis. In the very end of this thesis, to alleviate the phosphor-convention issue commonly observed in conventional white light LEDs, phosphor-free InGaN-based dichromatic-color blue/green (470-nm/550-nm) LEDs are well designed and successfully fabricated by using sapphire laser lift-off (LLO) and wafer-bonding schemes. Flat and broad EL spectra with combination of blue and green colors are emitted, accompanying with the maximum luminous efficiency of 120lm/W. This integrated dichromatic lighting structure has a great potential to facilitate the early coming of solid-state lighting.
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YU, CHIA-CHEN, and 游家志. "Enhancement of light extraction efficiency in organic light emitting diodes with WO3 micro/nano structure." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/v33wkv.
Full textAbstract:
碩士國立中正大學
物理系研究所
104
We present a new, simple method to improve internal light out coupling of organic light emitting diodes (OLED) by incorporating the micro- and nano- islands or network structures in the device. These structures were fabricated by a self-assembly technique based on the deliquescence of Cesium Chloride (CsCl) salt. The size and type of structures can be controlled by varying the CsCl film thickness, relative humidity, developing time and temperature. The fabricated structures can be used as a mask to transfer to Tungsten trioxide (WO3) hole injection layer by using thermal evaporation deposition. The light emitting performance of the WO3 patterned OLEDs was investigated. The maximum improvement of luminance efficiency of the WO3 patterned OLEDs can reach up to 76% for islands structures and 92% for networks structures compared with an unpatterned OLED.
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Lin, Tsung-Yu, and 林宗瑜. "Image Quality and Light Efficiency Enhancement of Organic Light-Emitting Devices by Using Microstructure Attachment." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/82521291541002203369.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
95
In this thesis, we set up a simulation model of organic light-emitting devices (OLED) with microstructure attachment. We demonstrated the simulation model and ray tracing analysis with the optical software LightTools TM. In order to improve the out coupling efficiency, we considered the total internal reflection (TIR) between air and substrate interface is a key place to be modified. We apply the micro-pyramid array to organic light-emitting devices (OLED) to reduce the total internal reflection (TIR) between air and substrate interface. Instead of merely concerning the efficiency for lighting purposes, we must take both the light extraction efficiency and image quality into account for display applications. In this simulation, we modulate some parameters such as base width, base angle, fill factor and arrangement of perfect micro-pyramid and truncated micro-pyramid, and try to find out the effects on angular intensity distribution, total power enhancement, and blurred image of the OLED. Finally we bring up several new microstructures and arrangement to control the blur effect and increase light extraction efficiency significantly.
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Hsu, Sheng-Chih, and 許聖志. "Blur Effect and Light Efficiency Enhancement of Organic Light-Emitting Devices by Using Microstructure Attachment." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/19561787051739967102.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
94
In this thesis, we demonstrated the simulation results of optical performance of organic light-emitting devices (OLED) by different kind of microstructure attachment. The simulations include the intensity, luminance efficiency, power efficiency, blurred image, and blur-width of the device which is attached by different microstructures. For lighting applications, we focus on light extraction efficiency and intensity distribution. For display applications, we pay attention to blurred image and blur-width. We also take the power and luminance enhancement into consideration. Finally, we bring up an innovation about specific arrangement of microstructure array on OLED display. We conclude the design rule for some parameters such as size, area ratio, height ratio, and arrangement of microlens array.