Nano-modified indium tin oxide incorporated with ideal microlens array for light extraction of OLED

Abstract

Nano-modified indium tin-oxide (ITO) glass substrates are fabricated for an internal light-extraction structure to enhance the out-coupling efficiency of green organic light-emitting diode (OLED) devices. This nano-modified anode with low haze was prepared by wet chemical etching. Polystyrene (PS) hemispheres, which were distributed randomly on the ITO anode surface, were used as the etching mold. With the help of nano-modified ITO glass substrate, the light trapped by the internal waveguide mode can be extracted effectively compared with conventional planar OLED devices. When OLED devices are incorporated with a nano-modified ITO anode, the highest enhancements of current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) are about 40.7%, 37.1% and 36.9%, respectively, relative to a standard device without any light out-coupling structure in the forward direction. To further improve the performance of OLED devices, an ideal microlens array (IMLA) is introduced to the air-side of the glass substrate to extract substrate waveguide. With both internal and external out-coupling structures, the CE, PE and EQE of OLED devices are enhanced by 101.5%, 100% and 96%, reaching 119.3 cd A⁻¹, 108.8 lm W⁻¹ and 31.4% in the forward direction, respectively. Moreover, the nano-modified ITO anode with low haze has no detrimental effect on the performance of OLED devices and is suitable for lighting and display application.