Impeding anion exchange to improve composition stability of CsPbX₃ (X = Cl, Br) nanocrystals through facilely fabricated Cs₄Pb X₆ shell*

Inorganic lead halide perovskite nanocrystals (NCs) with superior photoelectric properties are expected to have excellent performance in many fields. However, the anion exchange changes their features and is unfavorable for their applications in many fields. Hence, impeding anion exchange is important for improving the composition stability of inorganic lead halide perovskite NCs. Herein, CsPbX 3 (X = Cl, Br) NCs are coated with Cs4PbX 6 shell to impede anion exchange and reduce anion mobility. The Cs4PbX 6 shell is facily fabricated on CsPbX 3 NCs through high temperature injection method. Anion exchange experiments demonstrate that the Cs4PbX 6 shell completely encapsulates CsPbX 3 NCs and greatly improves the composition stability of CsPbX 3 NCs. Moreover, our work also sheds light on the potential design approaches of various heterostructures to expand the application of CsPbM3 (M = Cl, Br, I) NCs.