Cesium-lead-bromide perovskites with balanced stoichiometry enabled by sodium-bromide doping for all-vacuum deposited silicon-based light-emitting diodes

Abstract

Perovskite light-emitting diodes (PeLEDs) have drawn tremendous research attention recently. However, they are mainly prepared via solution processes, while the devices fabricated using the all-vacuum deposition procedure still remain largely unexplored. In this work, we prepared a cesium-lead-bromide perovskite film using the vacuum deposition method, and realized a more balanced stoichiometry by replacing some CsBr with NaBr. It was discovered that the introduction of an appropriate amount of NaBr not only reduced the insulating Cs₄PbBr₆ phase in the active layer, but also passivated the trap states effectively, which resulted in a 2-fold increase of the peak external quantum efficiency (EQE) of the PeLEDs to 2% with the maximum luminance reaching close to 40 000 cd m⁻² and significantly improved device operational stability compared to the undoped counterparts. Furthermore, we fabricated the first top-emissive silicon-based PeLED using the all-vacuum deposition method based on the NaBr doped perovskite films, and achieved a peak EQE of 0.33%, which has provided a promising alternative way for the design and preparation of high-performance silicon-based display devices in the future.