Synthesis of Highly Photoluminescent All-Inorganic CsPbX₃ Nanocrystals via Interfacial Anion Exchange Reactions

All-inorganic cesium lead halide perovskite CsPbX₃ (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 CsPbX₃ NCs at room temperature by the direct-synthesis method. Herein, we synthesize CsPbX₃ NCs by a facile and environmentally friendly method, which uses an aqueous solution of metal halides to react with Cs₄PbBr₆ NCs via interfacial anion exchange reactions and without applying any pretreatment. This method produces monodisperse and air-stable CsPbX₃ 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 Cs₄PbBr₆ NCs and CsPbX₃ NCs was investigated. The Cs₄PbBr₆ NCs were converted to CsPbBr₃ NCs first by stripping CsBr, and then, the as-prepared CsPbBr₃ NCs reacted with metal halides to form CsPbX₃ NCs. This work takes advantage of the chemical transformation mechanism of Cs₄PbBr₆ NCs and provides an efficient and environmentally friendly way to synthesize CsPbX₃ NCs.