Photoinduced Mn doping in cesium lead halide perovskite nanocrystals.

We report the photoinduced post-synthesis method of Mn doping in colloidal perovskite nanocrystals, which can produce Mn-doped CsPbX3 (X = Cl, Br) nanocrystals with preserved size and anisotropic morphology. Photoinduced Mn doping occurs through cation exchange driven by the facile photoinduced halide exchange in dihalomethane (CH2X2, X = Cl, Br) solvent taking advantage of in situ photogeneration of halide ions from the solvent molecules. In the presence of a small amount of Mn acetate dissolved in solvent at sub-micromolar concentration, photoexcitation of the nanocrystals above the bandgap initiates the simultaneous anion and cation exchange. Under the condition of self-anion exchange, the resulting product is only the cation (Mn) doping in the nanocrystal host without changing halide composition, where the extent of doping can be controlled by excitation light intensity. The mild nature of the photoinduced doping also preserves the anisotropic morphology of the nanocrystals. The photoinduced Mn-doping method could be further expanded to other cations providing a versatile means of creating various cation-doped perovskite nanocrystals that are difficult to produce by other means.