High-index transparent electrodes have been one major origin of light trapping and lower light extraction in organic light emitting diodes (OLEDs). In this work, influences of the bottom transparent electrode thickness on emission properties of OLEDs are systematically studied by both simulation and experiments. Simulation shows that with substantially decreasing the thickness of the high-index indium tin oxide (ITO) electrode, waveguided modes, that otherwise would be significantly induced in regular/thicker ITO devices, can be effectively eliminated. Consequently, the overall coupling efficiencies of OLED emission into substrates can be much enhanced. Through further effective light extraction from the substrate, green phosphorescent OLEDs with a high external quantum efficiency (EQE) of up to ≈57.5% were experimentally demonstrated by adopting the very thin (20 nm) ITO electrode and preferentially horizontal dipole emitters (with a horizontal dipole ratio of 76%). The simulation further predicts that very high optical coupling efficiencies into substrates and EQEs approaching 80% are possible with further adopting purely horizontal dipole emitters and/or low-index electron transport layer (ETL) to suppress surface plasmon modes. Overall, this study clearly reveals the potential of using thin transparent electrodes for highly efficient OLEDs.

高折射率透明电极已经成为有机发光二极管（OLED）中光捕获和较低光提取的主要来源之一。在这项工作中，通过仿真和实验系统地研究了底部透明电极厚度对OLED发射特性的影响。仿真表明，通过大幅降低高折射率铟锡氧化物（ITO）电极的厚度，可以有效消除常规模式/较厚ITO器件中会明显诱发的波导模式。因此，可以大大提高OLED发射到基板中的整体耦合效率。通过从基板进一步有效地提取光，绿色磷光OLED具有高达≈57的高外部量子效率（EQE）。通过采用非常薄的（20 nm）ITO电极和优先采用水平偶极子发射器（水平偶极子比率为76％），实验证明了5％。该模拟进一步预测，通过进一步采用纯水平偶极子发射极和/或低折射率电子传输层（ETL）来抑制表面等离子体激元模，可以实现接近80％的基板和EQE很高的光耦合效率。总的来说，这项研究清楚地表明了将薄透明电极用于高效OLED的潜力。该模拟进一步预测，通过进一步采用纯水平偶极子发射极和/或低折射率电子传输层（ETL）来抑制表面等离子体激元模，可以实现接近80％的基板和EQE很高的光耦合效率。总的来说，这项研究清楚地表明了将薄透明电极用于高效OLED的潜力。该模拟进一步预测，通过进一步采用纯水平偶极子发射极和/或低折射率电子传输层（ETL）来抑制表面等离子体激元模，可以实现接近80％的基板和EQE很高的光耦合效率。总的来说，这项研究清楚地表明了将薄透明电极用于高效OLED的潜力。