High Br- Content CsPb(Cl yBr1- y)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 CsPb1- xCl3: xMn2+ NCs can be used to obtain high Br- content Cs(Pb1- x- zZn z)(Cl yBr1- 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.