Waveguide Mode Outcoupling in Deep-Stacked White OLEDs Using a Subelectrode Microlens Array

The performance of organic light emitting diodes (OLEDs) is limited by the efficiency of light outcoupling from the emissive layer to visible air modes. This has resulted in many strategies to outcouple substrate, waveguide, and plasmonic modes. The subelectrode microlens array has previously been used to outcouple nearly 100% of waveguided modes while maintaining color quality and angle-independence, making the SEMLA a promising outcoupling scheme for white OLEDs (WOLEDs). Here, we demonstrate the effectiveness of SEMLAs used in conjunction with deep-stacked WOLED structures consisting of four separate emissive layers (EMLs). With the use of the SEMLA and an external microlens array, we achieve an external quantum efficiency of EQE = 162 ± 1% and a 1.9× enhancement relative to the control substrate while maintaining a color-rendering index >80. Moreover, we demonstrate that the SEMLA extends operational lifetime by a factor proportional to the EQE enhancement observed; approximately 1.8× for a single-EML green phosphorescent OLED.