Ligand Mediated Transformation of Cesium Lead Bromide Perovskite Nanocrystals to Lead Depleted CsPbBr Nanocrystals.

Lead halide perovskite nanocrystals (NCs) have emerged as attractive nanomaterials owing to their excellent optical and optoelectronic properties. Their intrinsic instability and soft nature enable a post-synthetic controlled chemical transformation. We studied a ligand mediated transformation of presynthesized CsPbBr NCs to a new type of lead-halide depleted perovskite derivative nanocrystal, namely CsPbBr. The transformation is initiated by amine addition, and the use of alkyl-thiol ligands greatly improves the size uniformity and chemical stability of the derived NCs. The thermodynamically driven transformation is governed by a two-step dissolution-recrystallization mechanism, which is monitored optically. Our results not only shed light on a decomposition pathway of CsPbBr NCs but also present a method to synthesize uniform colloidal CsPbBr NCs, which may actually be a common product of perovskite NCs degradation.