Study on the ultimate efficiency of organic light-emitting diodes based on trans-scale optical simulation

Abstract

We explored a systematic way to realize the achievable highest external quantum efficiency (EQE) for a given organic light-emitting diode (OLED) device with micro-lens array (MLA) or scattering layer (SL) based on trans-scale optical simulation. In the case of OLEDs fabricated on a glass substrate with SL, optimized OLED stacks based on highly horizontally oriented dipole emitters exhibited a maximum EQE of 56.3% by coupling with nanoparticle-based scattering layers tailored via Mie theory. However, global optimization result comparing MLA and a SL revealed that MLA could give the higher maximum EQE when high refractive index outcoupling layer as well as substrate is applied to OLED to extract light in waveguided mode additionally. Therefore, the sapphire MLA was applied to the optimized OLEDs fabricated on high refractive index substrate. At this time, the maximum 63% of EQE was demonstrated.