透明電極光電特性之研究應用於上發光式有機發光元件

Abstract

本文主要探討上發光式有機發光元件半透明陰極的改善，分成以下兩個部分。

第一部分，針對IZO/Ag/IZO三明治半透明陰極做探討，由實驗得知其中Ag的最薄成膜厚度為10nm，在此條件下(30/10/30)nm三明治陰極相對於單層IZO(60nm)電極的片電阻值下降了92%，穿透率在 390~630nm平均提升了8.5%。在元件部分，由於此上發光元件具有微共振腔效應，透過光學模擬軟體將三明治陰極整合於上發光綠光元件，在IZO/Ag/IZO厚度為(10/10/80)nm時為最佳化光學厚度，最後將其製作成上發光綠光元件，在10電流密度操作下，元件電流效率較標準元件相對增加7.18cd/A，功率效率增加5.19lm/W，外部量子效率增加2.35%。控制三明治陰極的光學厚度，等於控制共振腔長度以及電極反射率，便可調控元件的光學特性。視角方面，電致發光頻譜會隨著視角改變而藍位移，利用共振腔效應將正向增益設定在接近元件本質放光頻譜時，其藍位移現象較不明顯。發光強度部分，具有較強正向增益的元件，隨著視角增加發光強度下降的趨勢較明顯。

第二部分，我們持續尋找更好的透明導電膜，初步發現Indium Gallium Oxide(IGO)具有較高的穿透率。由於IGO的低吸收、高穿透率特性，使用於有機發光二極體的陰極覆蓋層，在相同厚度為800Å時，在10電流密度操作下，IGO電流效率相較於IZO提昇6%。

This thesis focus on improve the half-transparent cathode of Top Emission Organic Light Emitting Diode (TOLED).

First, We have demonstrated the top emitting OLED, which have multi-layer structure cathode consist IZO/Ag/IZO. The critical dimension of Ag is 10nm. The sheet resistance of the sandwich (30/10/30) nm is significant lower than single IZO (60nm) film of 95%. In the spectrum of 390~630nm, the transmittance of sandwich cathode is higher than single IZO film of 8.5%.

In order to optimize micro-cavity effect, the optical thickness of sandwich cathode is optimized to (10/10/80) nm. The current efficiency, Power efficiency and EQE which compare to control device can be improved 7.18cd/A, 5.19lm/W and 2.35% at 10mA/cm2 operating respectively. Devices optical performance can be controlled by adjusting sandwich electrode optical thickness. From the portion of view angle. The blue shifting of spectrum could be improved via introduce Micro-cavity effect into the devices design but electroluminescent intensity will be decay significantly if increase the view angle.

Second, study on the transparent conductive oxide. Indium Gallium Oxide (IGO) exhibits high transmittance and low absorption characteristic. We have demonstrated top tandem white OLED with IGO capping layer which has better optical performance. The current efficiency could be improved to 6% at 10mA/cm2 operating.