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標題: | 發光二極體顯示元件之光學模擬與分析之研究 Simulation and Analyses of Light-Emitting Diode Display Pixels |
其他標題: | Simulation and Analyses of Light-Emitting Diode Display Pixels |
作者: | 李章誠 Chang-Cheng Lee |
指導教授: | 吳忠幟 Chung-Chih Wu |
關鍵字: | 有機發光二極體,微發光二極體,光萃取效率,有限元素分析,蒙地卡羅光追跡方法,電流分布效應,電流聚集效應,表面發光強度分布, Organic light-emitting diodes,Micro light-emitting diodes,optical out-coupling efficiency,finite element analysis,Monte Carlo ray tracing method,current spreading,current crowding,surface emission intensity distribution, |
出版年 : | 2023 |
學位: | 博士 |
摘要: | 由於對先進顯示技術的高度需求,有機發光二極體(OLED)顯示器與微發光二極體(micro-LED)顯示器日益蓬勃發展。在本論文研究中,我們致力於研究OLED與micro-LED顯示器之光電物理機制,藉由嚴謹的有限元素分析之數值模擬與蒙地卡羅光追跡方法進行模擬研究。
在論文的第一部分,我們將全電磁波波動光學模擬應用在跨尺度之三維反射式OLED像素結構,此像素結構在上電極之上有額外的高折射率填料(Filler),此高折射率填料可導引那些在填料中初始入射角大於填料/空氣介面全反射臨界角之光線,經由四周的反射表面改變光線的入射方向而出光,進而提升光學萃取效率;為了解決在先前的跨尺度模擬方法(波動光學+光追跡)中無法預測頻譜量測中所觀察到的干涉調變效應,我們改採全電磁波波動光學的數值分析方法,值得一提的是由於三維OLED像素的尺寸相當的大,很難直接做運算,因此論文中會提出簡化數值運算量的方法;我們也將全波動光學的模擬結果:場型、變角度的頻譜與光萃取效率之增益與原來的光學模擬方法(波動+光追跡)還有實驗數據做比較,證實模擬之準確性及有效性。 在論文的第二部分,我們針對覆晶式氮化銦鎵micro-LED進行電性與光學特性上之模擬研究。首先,我們採用Comsol多重物理耦合模擬軟體之半導體模組利用有限體積法來進行覆晶式micro-LED的電性研究,元件內部的物理機制透過柏松方程式(Poisson’s equation)、電流不連續方程式、載子傳輸方程式與光子產生率方程式來進行求解;探討電流分布(Current spreading)效應、電流聚集(Current crowding)效應與Shockley-Read-Hall非輻射再結合效應,分析在不同操作電流密度下的多重量子井(MQW)內不均勻自發放光率的分布;接著,我們將此不均勻的自發放光率當作光源放入光跡模型,用以研究兩種光學結構,包含無保護層(OC)及具粗糙化表面之micro-LED、有保護層(OC)及具粗糙化表面之micro-LED,分析這兩種micro-LED結構的發光特性,包含發光場型,光萃取效率,並分析加上保護層(OC)之後所造成的光學損失,以及操作在不同電流密度下之正向表面發光強度分布,並將各種光學模擬結果與實驗資料做比對,獲取合理一致的結果,證實了所研究方法之有效性。 With the great demand for advanced display technologies, organic light emitting diode (OLED) and micro-light emitting diode (micro-LED) displays are becoming important display technologies. This thesis is devoted to simulation studies of the physical and optical properties of OLED and micro-LED displays, employing the rigorous numerical simulation based on the finite element analysis (FEM) and the Monte Carlo ray tracing method. In the first part of the dissertation, fully electromagnetic wave optic simulation and analyses of the cross-scale reflective 3D OLED pixel configuration were conducted. The pixel configuration with additional patterned high-index filler and concave reflector is capable of re-directing the light entering the filler with the initial internal angle larger than the TIR (total internal reflection) critical angle of the filler-air interface through surrounding reflective surfaces and enhancing the optical out-coupling efficiency. However, the interference modulation observed in EL spectra could not be well predicted by the previous multi-scale (wave+ray tracing) optical simulation. As such, the numerical analysis based on the fully EM optics was conducted in the study. As the size of the 3D OLED pixels is too huge to be calculated straightforwardly by the FEM based numerical simulation, so several methods to reduce the calculation loading have been devised. The wave optic simulation results, including emission patterns, angle-dependent EL spectra, and enhancement of out-coupling efficiencies were compared with the previous multi-scale (wave+ray tracing) optical simulation results and experimental results as well. In the second part of the dissertation, the comprehensive investigation on electrical and optical characteristics of InGaN-based flip-chip micro-light emitting diodes was conducted. We employed the finite volume method from the semiconductor module of the Comsol Multiphysics simulation tool to study the electrical properties of flip-chip micro-LEDs, considering Poisson’s equation, current discontinuity equation, carrier transport equation, and recombination rate equations, etc. The inhomogeneous spatial distribution of spontaneous emission rates in the MQW active regions resulting from the current spreading, current crowding, and Shockley-Read-Hall non-radiative recombination, etc. at different operating current densities were analyzed. We then used the non-uniform distributions of spontaneous emission rates to set up the light sources in the ray-tracing modeling. Two different micro-LED devices: (i) bare surface textured micro-LED without overcoat (OC), and (ii) surface textured micro-LED with OC, were studied. Optical characteristics such as the far-field emission patterns, optical out-coupling efficiencies of the micro-LEDs, and the optical loss with the additional OC were analyzed. The normal-direction surface emission intensity distribution profiles under different current densities were also analyzed. The optical simulation results were compared with the experimental data. Good agreement indicates the effectiveness of the simulation method here. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/83265 |
DOI: | 10.6342/NTU202300127 |
全文授權: | 未授權 |
顯示於系所單位: | 電子工程學研究所 |
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