Fast, tunable and reversible anion-exchange in CsPbBr3 perovskite nanocrystals with hydrohalic acids

Anion exchange in colloidal caesium-lead-halide perovskite nanocrystals (NCs) (CsPbX3, X = Cl, Br, I) is a highly efficient protocol to tune their chemical composition and optoelectronic properties. Here, we report for the first time the use of hydrohalic acids (HX; X = Cl and Br) as precursors for anion exchange, which can be an efficient way to control the composition and optical properties of CsPbBr3 perovskite nanocrystals (NCs). In this work, it is demonstrated that a facile and efficient anion-exchange approach is implemented to tune the optical properties of CsPbX3 perovskite NCsviaa simple post-synthetic modification with hydrohalic acids. For the Cl-exchanged NCs, back exchange can be established in terms of variation in halide composition to retain the photoluminescence (PL) properties of parent CsPbBr3 perovskite NCs to the maximum extent. Along with hydrohalic acids, various other halide sources have been used to achieve tunable anion-exchange of CsPbBr3 NCs. Treatment with hydrohalic acids allows for fast and feasible anion-exchange of CsPbX3 perovskite NCs which makes them stand out from the rest of the halide sources. Importantly, this work presents a simple, feasible, reproducible synthetic route to control halide exchange in metal halide perovskite NCs with various optoelectronic properties.