Дисертації з теми "Light emitting elements"
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Siddiqui, Saiful Anam. "Erbium doped silicon light emitting diodes." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/843408/.
Повний текст джерелаHabtemichael, Yishak Tekleab. "Packaging designs for ultraviolet light emitting diodes." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45764.
Повний текст джерелаYeo, Hyeonuk. "Synthesis of Optical Materials Based on Element-Blocks and Their Properties." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225317.
Повний текст джерелаWilliams, Jonathan H. T. "Finite element simulations of excitonic solar cells and organic light emitting diodes." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445404.
Повний текст джерелаMusolino, Mattia. "Growth, fabrication, and investigation of light-emitting diodes based on GaN nanowires." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17409.
Повний текст джерелаThis PhD thesis provides an in-depth insight on various crucial aspects of light-emitting diodes (LEDs) based on (In,Ga)N/GaN heterostructures grown along the axis of nanowires (NWs) by molecular beam epitaxy on Si substrates. In particular, the growth parameters are adjusted so as to suppress the coalescence of NWs; in this way the photoluminescence (PL) intensity emitted from the NW-LEDs can be increased by about ten times. The opto-electronic properties of the NW-LEDs can be further improved by exclusively employing indium tin oxide instead of Ni/Au as top contact. Furthermore, the compatibility of selective-area growth (SAG) of GaN NWs on AlN-buffered Si substrates with device operation is demonstrated, thus paving the way for a new generation of LEDs based on homogeneous NW ensembles on Si. Ordered arrays of ultrathin NWs are also successfully obtained by combining SAG and in situ post-growth thermal decomposition. A double-line structure is observed in the electroluminescence (EL) spectra emitted by the NW-LEDs; it is likely caused by compressive strain introduced by the (Al,Ga)N electron blocking layer in the neighbouring (In,Ga)N quantum well. An in-depth analysis of temperature dependent PL and EL measurements indicates that carrier localization phenomena do not dominate the EL emission properties of the NW-LEDs. The forward bias current-voltage (I-V) characteristics of different NW-LEDs are analysed by means of an original model that takes into account the multi-element nature of LEDs based on NW ensembles by assuming a linear dependence of the ideality factor on applied bias. The transport mechanisms in reverse bias regime are carefully studied by means of deep level transient spectroscopy (DLTS) and temperature dependent I-V measurements. The physical origin of the detected deep states is discussed. Then, a physical model able to describe quantitatively the peculiar I-V-T characteristics of NW-LEDs is developed.
Eritt, Michael. "Großflächige Abscheidung organischer Leuchtdioden und Nutzung optischer Verfahren zur in situ Prozesskontrolle." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-63184.
Повний текст джерелаThe thesis deals with the large area deposition of organic light-emitting diodes (OLED) for lighting applications with a novel deposition tool. The special needs of film thicknesses homogeneity and high deposition rates for organic layers request the combination of thermal vacuum deposition (VTE) and organic vapour phase deposition (OVPD) processes to fabricate OLEDs on 370 x 470 mm² substrates. The deposition sources are qualified regarding layer homogeneity and morphology of the deposition processes. The layer properties are controlled in a wide range by the variation of the organic vapour phase deposition parameters: substrate temperature and deposition rate. The in situ determination of the substrate thickness is shown by the application of spectroscopic reflectometry. The thesis demonstrates the thickness analysis of single and multi-layer stacks by reflectometry. The data fit well to ex situ ellipsometry. Robust OLED devices with an additional short-circuit protection layer deposited by OVPD technology are introduced. The current limiting properties of this layer reduce the leakage currents in the OLED device. The fabrication of 100 x 100 mm² white emitting OLED modules with power efficiencies about 13 lm/W shows the great potential of the manufacturing technology
Connors, Benjamin James. "Simulation of current crowding mitigation in GaN core-shell nanowire led designs." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41206.
Повний текст джерелаBender, Vitor Cristiano. "Metodologia de projeto eletrotérmico de LEDs aplicada ao desenvolvimento de sistemas de iluminação pública." Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/8510.
Повний текст джерелаThis work presents an LED electrothermal design methodology applied to a street lighting system. The methodology aims to provide indicatives of the optimal LED operating point for lighting systems design, considering electrical, thermal and photometric system features. Different projects are developed according to the methodology, the theoretical results are compared with fluid dynamics simulation and demonstrated by experimental results. A research including luminous flux, luminous efficacy and flicker is performed considering the LED current ripple, defining acceptable levels of ripple based on the optimal operational point. The methodology is applied by developing a lighting system composed of an LED driver and a thermal dissipation system, comprising a luminaire, a heatsink and fans. The lighting system includes electrothermal feedback control. The results provide high power factor with low current harmonic distortion to the power grid. The LED operational temperature ensures the luminous flux maintenance over the system lifetime.
Este trabalho apresenta uma metodologia de projeto eletrotérmico de LEDs aplicada a um sistema de iluminação pública. A metodologia tem o objetivo de proporcionar indicativos do melhor ponto de operação do LED para o projeto de sistemas de iluminação, considerando os aspectos elétricos, térmicos e fotométricos envolvidos no sistema. Diferentes projetos são desenvolvidos utilizando a metodologia, os resultados teóricos obtidos são comparados com simulações computacionais de dinâmica dos fluidos e comprovados através de resultados experimentais. Um estudo do fluxo, eficácia e cintilação luminosa é também realizado considerando a ondulação de corrente aplicada aos LEDs, definindo os níveis aceitáveis de ondulação com base no ponto ótimo de operação. Para aplicação da metodologia é desenvolvido um sistema de iluminação pública composto por um circuito de acionamento dos LEDs e um sistema de dissipação térmica, formado por uma luminária, um dissipador de calor e ventiladores. O sistema de iluminação possui controle com realimentação eletrotérmica. Os resultados obtidos proporcionam alto fator de potência com baixa distorção harmônica ao sistema elétrico e temperatura de operação que garante a manutenção do fluxo luminoso dos LEDs durante toda a vida útil do sistema.
Bender, Vitor Cristiano. "Modelagem e acionamento de diodos orgânicos emissores de luz (OLEDs) para sistemas de iluminação." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/3691.
Повний текст джерелаThis thesis presents the study and characterization of organic light-emitting diodes (OLEDs) with the proposal of obtaining an equivalent model that is useful in the OLED driver design and in lighting systems projects. Initially, a literature review covering the operating principle and the constructive aspects of OLEDs is presented. From this, a model that integrates scale, photometrical, electrical and thermal aspects is proposed. This model is static and dynamic and is called EFET. A procedure for parameter identification of the model is proposed, jointly with an analysis of the intrinsic capacitance effect on the OLED electrical, thermal and photometrical performance. The proposed model is able to predict and simulate the OLED based lighting systems before building, saving time and cost. The model is validated using different OLED samples and conclusions are derived from the experimental validation and simulation results. An approach considering the dimming methods of OLEDs is presented, showing the chromatic impact caused by each method. Finally, an OLED driver based on the concept of switched capacitor converters is proposed. The thesis results are satisfactory and provide an enhancement to the state of the art in modeling and OLED driving.
A presente tese de doutorado apresenta o estudo e a caracterização de diodos orgânicos emissores de luz (OLEDs) com a proposta de um modelo equivalente que é útil no desenvolvimento de circuitos de acionamento e na análise de OLEDs, quando aplicados em sistemas de iluminação. Inicialmente, é apresentada uma revisão bibliográfica contemplando o princípio de funcionamento e os aspectos construtivos dos OLEDs. A partir disto, um modelo que integra os aspectos de escala, fotométricos, elétricos e térmicos é proposto. Esse modelo é denominado EFET e é dividido em estático e dinâmico. Uma proposta de procedimento para identificação dos parâmetros do modelo é apresentada, juntamente com a análise do efeito da capacitância intrínseca dos OLEDs no seu desempenho elétrico, térmico e fotométrico. Com o modelo proposto pode-se predizer e simular o comportamento dos OLEDs antes de construir o sistema de iluminação, reduzindo custos e tempo de desenvolvimento. O modelo é validado empregando diferentes amostras de OLEDs. Conclusões são obtidas a partir da validação experimental e de simulações empregando simuladores elétricos e da fluidodinâmica computacional através do método de elementos finitos. Uma abordagem considerando os métodos de ajuste da intensidade luminosa de OLEDs é apresentada, evidenciando o impacto cromático provocado por cada método. Por fim, um circuito de acionamento para OLEDs baseado no conceito de capacitores chaveados é proposto. Os resultados obtidos são satisfatórios e proporcionam um incremento ao estado da arte da modelagem e acionamento de OLEDs.
Tu, Sheng-Han, and 杜昇翰. "Integration of special chip process and secondary elements for light emitting diodes illumination module." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/82409340006152693592.
Повний текст джерела國立中央大學
光電科學研究所
98
For the sake of energy shortage, the developments of new energy and energy saving have attracted the interests of advanced nations. The light emitting diodes possesses advantages such as low power consumption, compact volume and long life time so that it has took the place of conventional light source gradually. In this thesis we developed a series of methods that to crossed the chip process and lighting module enhance the light performance of light emitting diodes. We integrated special chip process and secondary optics element to form a lighting module that can be applied to different applications such as back light module of liquid crystal display, projector and street lamp. The adopted methods include imprinting technique, pad reflector, surface roughness, ThinGaN LED pattern design, the guided mode resonance (GMR) filter to enhance the output power efficiency of LED and modulate the lighting performances. The secondary optics elements were used to modulate the far-field pattern of LED to achieve an expanded or a collimator far-field pattern. In order to increase the light extraction efficiency and modulate the lighting performance of LED, we adopted the thermal stress free and room temperature imprinting technique. We imprinted the one and two dimension onto the chip surface by stable material SOG. After imprinting structure application, the output power enhancement reached 17% to 35%. Furthermore, the blazed grating can deflect the peak intensity of far-field pattern to 20° and the two dimensional structure can achieve an expansion far-field pattern. A GaN-based light-emitting diode (LED) with non-alloyed metal contacts and textured Ga-doped ZnO (GZO) contact layer were served as the n- and p-type electrode pads, respectively. Compared with the conventional LEDs with flat surface and Cr/Au metal contacts, the non-alloyed Ag/Cr/Au contacts used in the present experimental LEDs play the role of reflector to prevent the emitted light from absorption by the opaque electrode pads. Enhancement of light output power observed from the experimental LEDs is also due to the textured GZO layer that can disperse the angular distribution of photons at the GZO/air interface. With an injection current of 20mA, the enhancement of the LOP approximately has a 30% magnitude compared with conventional GaN-based LEDs. Finally, the numerical method was used to discussion the relation between output power and pad reflectivity. Several n-type electrode patterns were designed to evaluate the current spreading effects in high power ThinGaN light emitting diodes. A proposed three dimensional numerical simulation was used to investigate the current spreading distributions. The experimental current spreading tendencies in various n-type electrodes were consistent with the simulation results. The maximum lighting output power was enhanced to 11% in our electrode pattern designs. The current-voltage and luminance-current performance of LED chips can apparently be improved with a better current spreading distribution. Therefore, this three dimensional simulation method could be used for the advanced analysis and optimization of LED performance. A simple and hybrid combination of a green light-emitting diode (LED) chip with an asymmetric guided-mode resonance (GMR) filter is proposed to reduce the full-width-at-half-maximum (FWHM) of LED emission spectrum for the LED backlight system. The color gamut consisting of multiple LEDs is significantly expanded from 122 to 137. It also possesses stable transmittance within 5 degree incident angle for the unpolarized light. This GMR filter provides superior transmittance efficiency (84%), and FWHM performance (15nm). The fabrication tolerances of asymmetric GMR are also analyzed and discussed. A cost effective, high throughput, and high yield method for the increase of street lamp potency was proposed in this paper. We integrated the imprinting technology and the reflective optical element to obtain a street lamp with high illumination efficiency and without glare effect. The imprinting technique can increase the light extraction efficiency and modulate the intensity distribution in the chip level. The non-Lambertian light source was achieved by using imprinting technique. The compact reflective optical element was added to efficiently suppress the emitting light intensity with small emitting angle for the uniform of illumination intensity and excluded the light with high emitting angle for the prevention of glare. Compared to the convectional street lamp, the novel design has 40% enhancement in illumination intensity, the uniform illumination and the glare effect elimination.
Ying-ChihChen and 陳應誌. "Investigation of Inorganic Quantum Dots in Light-Emitting Diodes and Nonvolatile Organic Memory Elements." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/20046002711054135721.
Повний текст джерелаTzer, An Hung, and 洪澤安. "Group IV Element Metal-Oxide-Semiconductor Light Emitting Devices." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/62421984380314050293.
Повний текст джерела國立臺灣大學
電子工程學研究所
96
In this thesis, various metal-oxide-semiconductor light-emitting-devices (MOS LED) were fabricated and investigated of their luminescence characteristics. The MOS LED structures include the Ge MOS LED with silicon dioxide (SiO2), Ge MOS LED with aluminum oxide (Al2O3) and the 6H-SiC MOS LED. Infrared emission is observed from the Ge MOS LED. A spectral line fit is performed on the luminescence spectrum with the electron-hole-plasma (EHP) recombination model with 5 phonon assisted replica, including TO, LA, TA emission, and TA, LA absorption. Intensity of the TA phonon absorption is seen to increase at elevated temperatures. Reduced thermal quenching in electroluminescence compared to photoluminescence measurements is due to the large difference in concentration between the majority and minority carriers in EL, which limits the cause of the decrease of radiative recombination probability to only the lowering of the minority concentration. The Ge MOS LED with Al2O3 insulator shows improvements in performance that include smaller operating voltage, smaller leakage current, stronger light emission, reduced nonradiative radiation and an increase in light emission intensity at elevated operation temperatures. Blue luminescence at reverse bias is observed in the 6H-SiC MOS LED.
林濟翔. "Light-Emitting Diode and the Secondary Optics Element Applied to Coral Raised Lamp." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/18813266661381464004.
Повний текст джерела中華科技大學
機電光工程研究所碩士班
104
Abstract Coral reefs in a marine ecosystem ecosystem, we call it the "tropical rain forest in the ocean," it is the most biologically diverse marine ecosystem. However, global climate change and man-made destruction, has resulted in a large number of the world's coral death, so coral protection and restoration of coral is a very important issue. When coral growth rely on a source of nutrition for an illuminating light, so the first study of coral growth required spectral range, and the use of light-emitting diode characteristics of the synthesized approximation of the spectrum, then "TracePro" secondary optics design through simulation software, the different wavelengths of light to make a uniform mixed light, so that corals can receive the appropriate light exposure. This study and the "National Museum of Marine Science and Technology" cooperation, we will design a lamp placed in the museum to do the actual experiment coral keeper. By making corals aquarium system water quality and temperature of the environment consistent with the experimental changes only light, lighting compared with other aquarium, coral breeding period of time to observe the rate of survival of coral growth rate, color effect, the verification result Lamps of this study prove more suitable for coral growth.
Yang, Chih-Yu, and 楊知育. "Design and Research of Polymer Light Emitting Diode Element with Roll to Roll Coating Machine." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/s47jk8.
Повний текст джерела國立高雄科技大學
化學工程與材料工程系
107
A procedure is the PLED component production process without of vacuum equipment. We apply a polymer film by an independently developed roll-to-roll slit coating machine. Research and adjust equipment and paints to find the best process parameters. Improved PEDOT: PSS coatings are used more effectively in PLED components to increase luminous intensity to 1300 A.U. Zinc oxide is selected as the electron transport layer, and the PLED component is divided into two parts, the cathode and the anode, and the two electrodes are combined by means of hot pressing. The PLED component can be successfully fabricated without vacuum equipment and can illuminated 800 A.U. at least 3 hour.
Eritt, Michael. "Großflächige Abscheidung organischer Leuchtdioden und Nutzung optischer Verfahren zur in situ Prozesskontrolle." Doctoral thesis, 2010. https://monarch.qucosa.de/id/qucosa%3A19423.
Повний текст джерелаThe thesis deals with the large area deposition of organic light-emitting diodes (OLED) for lighting applications with a novel deposition tool. The special needs of film thicknesses homogeneity and high deposition rates for organic layers request the combination of thermal vacuum deposition (VTE) and organic vapour phase deposition (OVPD) processes to fabricate OLEDs on 370 x 470 mm² substrates. The deposition sources are qualified regarding layer homogeneity and morphology of the deposition processes. The layer properties are controlled in a wide range by the variation of the organic vapour phase deposition parameters: substrate temperature and deposition rate. The in situ determination of the substrate thickness is shown by the application of spectroscopic reflectometry. The thesis demonstrates the thickness analysis of single and multi-layer stacks by reflectometry. The data fit well to ex situ ellipsometry. Robust OLED devices with an additional short-circuit protection layer deposited by OVPD technology are introduced. The current limiting properties of this layer reduce the leakage currents in the OLED device. The fabrication of 100 x 100 mm² white emitting OLED modules with power efficiencies about 13 lm/W shows the great potential of the manufacturing technology.