Optical properties of Mn2+ doped cesium lead halide perovskite nanocrystals via a cation–anion co-substitution exchange reaction

Abstract

The emission colors of cesium lead halide perovskite nanocrystals (NCs) can be controlled by dynamic ion exchange and Mn²⁺ doping. Herein we report a novel strategy for the synthesis of Cs(Pb_xMn_1−x)(Cl_yBr_1−y)₃ NCs via a post-synthetic cation–anion cosubstitution exchange reaction to tailor their optical properties in a wide range. Colloidal CsPbBr₃ and CsPb_1−xMn_xCl₃ NCs are firstly prepared, separately, and then mixed together in hexane solution. The Pb²⁺ and Br⁻ ions in the CsPbBr₃ NCs are simultaneously exchanged for the Mn²⁺ and Cl⁻ ions in the CsPb_1−xMn_xCl₃ NCs, resulting in homogeneous Cs(Pb_xMn_1−x)(Cl_yBr_1−y)₃, with preservation of the shape and crystal structure of the initial NCs. This in situ ion exchange method avoids the degradation of photoluminescence originating from the additional purification process of the NCs, and in situ Mn²⁺ substitution also greatly enhances the emission intensity and quantum yield of the as-obtained NCs, which is found to be related to the bound exciton effect.