High Br^– Content CsPb(Cl_<i>y</i>Br_1–<i>y</i>)₃ Perovskite Nanocrystals with Strong Mn²⁺ Emission through Diverse Cation/Anion Exchange Engineering

The unification of tunable band edge (BE) emission and strong Mn²⁺ doping luminescence in all-inorganic cesium lead halide perovskite nanocrystals (NCs) CsPbX₃ (X = Cl and Br) is of fundamental importance in fine tuning their optical properties. Herein, we demonstrate that benefiting from the differentiation of the cation/anion exchange rate, ZnBr₂ and preformed CsPb_{1- x}Cl₃: xMn²⁺ NCs can be used to obtain high Br^- content Cs(Pb_{1- x- z}Zn _z)(Cl _yBr_{1- y})₃: xMn²⁺ perovskite NCs with strong Mn²⁺ emission, and the Mn²⁺ substitution ratio can reach about 22%. More specifically, the fast anion exchange could be realized by the soluble halide precursors, leading to anion exchange within a few seconds as observed from the strong BE emission evolution, whereas the cation exchange instead generally required at least a few hours; moreover, their exchange mechanism and dynamics process have been evaluated. The Mn²⁺ emission intensity could be further varied by controlling the replacement of Mn²⁺ by Zn²⁺ with prolonged ion exchange reaction time. White light emission of the doped perovskite NCs via this cation/anion synergistic exchange strategy has been realized, which was also successfully demonstrated in a prototype white light-emitting diode (LED) device based on a commercially available 365 nm LED chip.