In Situ Halide Exchange of Cesium Lead Halide Perovskites for Blue Light-Emitting Diodes

摘要

3D perovskites are promising to achieve efficient and bright deep-blue lightemittingdiodes (LEDs), which are required for lighting and display applications.However, the efficiency of deep-blue 3D perovskite-based LEDs islimited by high density of defects in perovskites, and their deep-blue emissionis not easy to achieve due to the halide phase separation and low solubilityof chloride in precursor solutions. Here, an in situ halide exchange methodis developed to achieve deep-blue 3D perovskites by spin-coating an organichalide salts solution to treat blue 3D perovskites. It is revealed that the halideexchangeprocess is mainly determined by halide ion diffusion targeting aconcentration equalization, which leads to homogeneous 3D mixed-halideperovskites. By further introducing multifunctional organic ammonium halidesalts into the exchange solution to passivate defects, high-quality deep-blueperovskites with reduced trap density can be obtained. This approach leads toefficient deep-blue perovskite LEDs with a peak external quantum efficiency(EQE) of 4.6% and a luminance of 1680 cd m?2, which show color coordinatesof (0.131, 0.055), very close to the Rec. 2020 blue standard. Moreover, the halideexchange method is bidirectional, and blue perovskite LEDs can be achievedwith color coordinates of (0.095, 0.160), exhibiting a high EQE of 11.3%.