Ligand Mediated Transformation of Cesium Lead Bromide Perovskite Nanocrystals to Lead Depleted Cs 4 PbBr 6 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 3 NCs to a new type of lead–halide depleted perovskite derivative nanocrystal, namely Cs 4 PbBr 6 . 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 3 NCs but also present a method to synthesize uniform colloidal Cs 4 PbBr 6 NCs, which may actually be a common product of perovskite NCs degradation.