Effect of Refractive Index Contrast on Out-Coupling Efficiency of Corrugated OLEDs using Low-Refractive-Index LiF Interlayer

In organic light-emitting diodes (OLEDs), the low out-coupling efficiency of 20–30% limits the external quantum efficiency (EQE). Corrugated structures for OLED light extraction can increase the out-coupling efficiency by extracting the thin-film-guided mode as well as the surface plasmon (SP) mode. To further enhance the out-coupling efficiency of a corrugated OLED, we increase the refractive index contrast by incorporating a low-index light out-coupling layer in the device and the resulting OLED has an external quantum efficiency of 67%. By fabricating these corrugated OLEDs with the emitting layer located at the first and second antinode positions, we confirm that the enhanced extraction comes from the enhanced extraction of thin-film-guided modes.