Synthesis of Highly Photoluminescent All-Inorganic CsPbX Nanocrystals via Interfacial Anion Exchange Reactions.

All-inorganic cesium lead halide perovskite CsPbX (X = Cl, Br, I) nanocrystals (NCs) have attracted significant attention owing to their fascinating electronic and optical properties. However, researchers still face challenges to achieve highly stable and photoluminescent CsPbX NCs at room temperature by the direct-synthesis method. Herein, we synthesize CsPbX NCs by a facile and environmentally friendly method, which uses an aqueous solution of metal halides to react with CsPbBr NCs via interfacial anion exchange reactions and without applying any pretreatment. This method produces monodisperse and air-stable CsPbX NCs with tunable spectra covering the entire visible range, narrow photoluminescence emission bandwidth, and high photoluminescence quantum yield (PL QY, 80%). In addition, the chemical transformation mechanism between CsPbBr NCs and CsPbX NCs was investigated. The CsPbBr NCs were converted to CsPbBr NCs first by stripping CsBr, and then, the as-prepared CsPbBr NCs reacted with metal halides to form CsPbX NCs. This work takes advantage of the chemical transformation mechanism of CsPbBr NCs and provides an efficient and environmentally friendly way to synthesize CsPbX NCs.