Slowing Down for Growth Mechanism and Speeding Up for Performance Optimization Based on Single Ligand Passivated CsPbBr₃ Nanoplatelets

Abstract Quasi 2D metal halide perovskite nanoplatelets (NPls), as a kind of important materials to achieve pure blue emission, attract significant attention in pursuit of high gamut trichromatic display. However, in‐depth study on the specific growth processes of NPls is still lacking due to the ultrafast reaction rate. Here, a single ligand passivation strategy to investigate the concrete growth mechanism of NPls is proposed, in which the PbBr_x(OAm)_y clusters play a pivotal template role in guiding the growth of crystals, and the final products with 3‐monolayer (3ML) are grown from the intermediate 2ML NPls instead of being synthesized directly. Based on the new discovery about growth mechanism of NPls, the reaction time has been shortened from hours to seconds by introducing hydrobromic acid and ethanol. The ethanol used here is considered as an accelerator for the transition from 2ML to 3ML NPls rather than an initiator for nucleation of products, which is different from the generally accepted viewpoints. With further passivation of hydrobromic acid, the synthesized 3ML NPls show 462 nm emission with quantum yield of 97.04% and great photostability. The novel growth model proposed in this work will provide a paradigm for future design and optimization of new synthesis schemes.