Chloride Vapor\nAnnealing for Efficient Deep-Blue Perovskite\nLight-Emitting Diodes

Achieving\ndeep-blue emission is crucial for the practical application\nof perovskite light-emitting diodes (LEDs) in displays. Increasing\nthe ratio of chlorine to bromine in the perovskite is a facile method\nto achieve deep-blue emission. However, the low solubility of chloride\nin the perovskite precursor solution and the low formation energy\nof defects present challenges that limit device efficiency. Here,\nwe demonstrate a chloride vapor annealing method utilizing ethylammonium\nchloride (EAC) to enable in situ halide exchange and defect passivation.\nWe find that the chloride ions from EAC can effectively exchange with\nthe bromide ions in the perovskite, resulting in blue-shifted emission.\nAdditionally, the ammonium group in EAC can coordinate with unsaturated\nlead, reducing trap-assisted nonradiative recombination. Based on\nthis approach, we achieve efficient deep-blue perovskite LEDs with\na peak external quantum efficiency of 6.8% and color coordinates of\n(0.131, 0.044), which fully meet the Rec. 2020 blue standard.