发表机构
University of Cologne; Korea Advanced Institute of Science and Technology (KAIST); University of St Andrews（科隆大学; 韩国科学技术院; 圣安德鲁斯大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究针对OLED外部量子效率停滞的问题，提出光提取多通过程的往返损耗是关键，通过添加低损耗辅助反射镜提升了EQE，推导设计规则预测可达90%的EQE。
AI 中文摘要
现代有机发光二极管（OLED）的内部量子效率接近100%，但在平面器件中仅有20%-30%的光子能够逸出。高折射率衬底上的外部耦合结构可回收部分被捕获的光，不过不同光学设计下的外部量子效率（EQE）已停滞在55%-60%，且该效率上限的成因尚未完全明晰。本文将此类OLED的光提取过程界定为多通过程：耦合结构未能提取的光会返回OLED，经反射后可能在多通过程中逸出，其效率由每通的吸收损耗决定。吸收损耗在常规平面OLED中占比极小，但在加装耦合结构后会成为主导因素，且是观测到的效率上限的成因。与该结论一致的是，添加低损耗辅助反射镜可使高折射率微透镜衬底上的OLED的EQE从51%提升至77%，且无需改变OLED叠层或耦合结构，这是无宏观提取透镜的单结OLED的最高报道值；对于常规玻璃衬底上的OLED，输送至衬底的光中约92%被成功提取。本文推导了四条设计规则，可将往返损耗控制在几个百分点，并预测采用现有材料可实现约90%的EQE。遵循这些规则时，微腔调谐和发光体取向的影响基本消失，且在大范围的微透镜设计和散射层中均可保持高效率。
英文摘要
Modern organic light-emitting diodes (OLEDs) reach internal quantum efficiencies close to 100%, yet in a planar device only 20-30% of photons escape. External outcoupling structures on high-index substrates recover some of the trapped light, but external quantum efficiencies (EQEs) have stalled at 55-60% across different optical designs, and the origin of this ceiling is not fully understood. Here we identify light extraction in such OLEDs as a multi-pass process: light that the outcoupling structure fails to extract returns to the OLED, is reflected back and may escape over multiple passes, with the efficiency governed by the absorption per round trip. Absorption loss is minor in conventional planar OLEDs, but it becomes dominant and accounts for the observed efficiency ceiling when an outcoupling structure is attached. Consistent with this picture, adding a low-loss auxiliary reflector raised the EQE of an OLED on a high-index microlens substrate from 51% to 77% without any change to the OLED stack or the outcoupling structure, the highest value reported for a single-junction OLED without a macroscopic extraction lens; for an OLED on a conventional glass substrate an estimated 92% of the light delivered to the substrate was extracted. We derive four design rules that keep round-trip losses to a few percent and predict that EQEs around 90% are feasible with established materials. Under these rules, microcavity tuning and emitter orientation largely cease to matter, and high efficiency is retained across a wide range of microlens designs and scattering layers.
Comments39 pages, 4 figures, 12 supplementary figures, 1 supplementary table
