Enhance the Light Extraction Efficiency of QLED with Surface Micro-Nanostructure

Abstract

Quantum dot light-emitting diodes (QLEDs) are usually a flat multilayer structure. The luminous efficiency of QLEDs is limited because the light extraction is constrained owing to the substrate mode at the air/substrate interface, the waveguide mode at the conductive glass/organic interface, and the surface plasmon polaritons (SPPs) along the metal/organic interface. To improve the light extraction for the luminous efficiency of QLEDs, light transmission through the QLEDs coupled with three different surface micro-nanostructures is simulated by using a ray-tracing method. Furthermore, QLEDs (red, green, and blue emission) coupled with micro-nanostructures are also fabricated to investigate the influence of the micro-nanostructures on the luminous efficiency. Our simulation results show that more light escapes from the QLEDs coupled with surface micro-nanostructures than the control devices without micro-nanostructures. Our experimental results are consistent with the simulation results. By coupling with surface micro-nanostructures, the luminous efficiencies of the devices exhibited great improvement, and the EQE of R/G/B trichromatic reached 17.3%, 2.81%, and 10%, respectively, which are about 1~2 times higher than those of the control devices without any surface structure. Our results should make a contribution to building a strategy for improving the luminous efficiency of QLEDs.