Integration of special chip process and secondary elements for light emitting diodes illumination module

Autor: Sheng-Han Tu, 杜昇翰
Rok vydání: 2010
Druh dokumentu: 學位論文 ; thesis
Popis: 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.
Databáze: Networked Digital Library of Theses & Dissertations
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