Analysis and optimization of light outcoupling in OLEDs with external hierarchical textures

Hierarchical textures (combining 2D periodic large and small micro textures) as an external outcoupling solution for OLEDs have been researched, both experimentally by optical simulations. For the case of a red bottom emitting OLED, different hierarchical were fabricated using laser-based methods replication step applied to OLED substrate, resulting in increased light outcoupling. Laboratory-size devices with textured foils show smaller increase efficiency compared final area devices. The results that full exploitation laboratory-size samples is mainly limited lateral size thin film stack collection measuring equipment. Modeling simulations are used further evaluate prospective Optimization done simultaneously changing aspect ratios potential 57% improvement EQE without predicted Optimized similar efficiencies optimized single textures, while on other hand require less pronounced features, lower ratios, achieve same efficiencies. also help eliminating flat parts limit efficiency. Finally, limiting factors prevent higher addressed. We dominant factor non-ideal reflection from organic due parasitic absorption. In addition, possible ways thick substrate indicated.