Enhancing efficiency in vacuum-evaporated perovskite light emitting diodes through an artificial multiple quantum well structure

Abstract

Halide perovskite has been reported as the next generation materials for light-emitting diodes (LEDs) due to their high color purity (FWHM, full width at half maxima, ~ 20 nm), high photoluminescence efficiency and tunable bandgap. When compared to solution processes, the vacuum deposition allows for precise control of film thickness and facilitates scalability to large-area processes. However, the most of the perovskite films are fabricated by the solution process, while the vacuum deposition method approach has not yet been thoroughly investigated. Here, CsPbBr3 was synthesized by vacuum deposition of CsBr and PbBr2, and an artificial multi quantum well (MQW) structure light-emitting diode was fabricated by stacking layers of CsPbBr3 and sodium fluoride. The interface between the NaF layer and CsPbBr3 layer played a role as the barrier of the MQW structure. Through the utilization of the MQW structure, the exciton binding energy was increased, and surface bromide defects were passivated, resulting in an EQE of 5.13% and a luminance of 4,876 cd/m2. Furthermore, the introduction of a trioctylphosphine oxide (TOPO) layer led to an enhanced EQE of 6.74%.