在發光二極體及有機發光二極體中加入光子晶體結構來增加 發光萃取效率的探討

Abstract

本論文發展了一套可以有彈性、有效率計算發光元件發光效率的方法。本方法 以有限時域差分法為主輔以傅式分析得到目標頻率的強度, 再將各個位置、各 個角度的能量加總得到進入空氣的總出光率。 發光二極體及有機發光二極體可能成為顯示及照明的主要元件之一, 然而發光 二極體和有機發光二極體都有發光效率低落的問題。有鑒於此, 本篇論文將焦 點放在發光二極體及有機發光二極體的模擬。我們採用的提高發光效率的方式 為在發光二極體及有機發光二極體中加入光子晶體。在參數範圍內進行掃描以 取得最佳情形的最佳出光率和出光率與各個參數間的關係, 以進一步了解各種 參數的影響及設計考量。 我門定義未加入光子晶體的結構為原始結構。先以最常見的方形結構來計算。 另外, 三角形結構、半圓形結構以及圓形結構也列入考慮。最後我們可以得到 在發光二極體中, 方形結構相對於原始結構可以得到三倍的出光率提升為最佳。 而在有機發光二極體中, 方形加平板的結構相對於原始結構可以得到三成的出 光率提升為最佳。

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.