Coupled Optical Modeling for Optimization of Organic Light-Emitting Diodes with External Outcoupling Structures

We present an optical optimization on a red bottom-emitting OLED with an enhanced cavity in combination with external outcoupling textures, periodically positive and negative hexagonal dome-shaped structures. A coupled optical modeling, combining simulations of coherent planar and incoherent structured layers, is verified and employed for optimization of the OLED structure and applied textures. Special attention is paid on the study of optical effects, related to the limited device area. Using optical modeling, we present and quantify main optical losses in the device. We show the importance of considering external outcoupling structures in optimization of thicknesses of organic films, which define the optical cavity. When optimized, an OLED with 50.5% light extraction efficiency (39.4% external quantum efficiency) and improved angular intensity distribution is predicted for devices with positive shaped dome structures. This approach allows for global efficiency optimization of complete OLEDs, comprising arbitrarily shaped outcoupling structures.