Room-temperature synthesis of Mn²⁺-doped cesium lead halide perovskite nanocrystals via a transformation doping method

Currently, Mn²⁺-doped cesium lead halide perovskite nanocrystals have attracted research interests. Here, we report a novel room-temperature transformation doping method for the synthesis of Mn²⁺-doped CsPbCl₃ and CsPb(Br/Cl)₃ nanocrystals. Innovatively, the transformation of Cs₄PbX₆ (X=Cl, Br) phase which has no excitation emission to CsPbX₃ phase which has strong luminescence was used in this mechanism. Simply injecting MnCl₂ precursor into Cs₄PbX₆ solution could result in the full transformation of Cs₄PbX₆ phase to CsPbX₃ phase and Mn²⁺-doped CsPbCl₃ or CsPb(Br/Cl)₃ were obtained. The basic idea for the transformation doping method is that MnCl₂ can not only drive the transformation of the two structures but also Mn²⁺ can substitute Pb²⁺. In this reaction, the concentration of Mn precursor is a key influence factor. Moreover, instead of the ligand of OA, the acetic acid was used in our method. Through the adjustment of the ligand in precursor, not just the photoluminescence quantum yields of as-prepared Mn²⁺-doped CsPbCl₃ nanocrystals were improved from 7.8 to 32.6% (Mn²⁺-doped CsPb(Br/Cl)₃ nanocrystals even could reach to 42.7%), the nanocrystals also retained outstanding stability. We propose a combination of structure transformation and ion doping as a perovskite doping mechanism. Our doping method is a novel strategy for lead halide perovskite nanocrystals doping project and it could provide more possibilities in the future.