Reverse synthesis of CsPbxMn1−x(Cl/Br)3 perovskite quantum dots from CsMnCl3 precursors through cation exchange

Abstract

Successful development of all-inorganic CsPbX₃ (X = Cl, Br, or I) perovskite quantum dots (PQDs) has been witnessed due to their unique optical and electrical properties. However, the heavy usage of Pb element in PQDs has limited the commercial application of these PQDs, and the preparation of low-Pb or Pb-free PQDs is imperative. In this study, we report room-temperature reverse synthesis of CsPb_xMn_1−xCl₃ PDQs from CsMnCl₃ precursor nanocrystals through cation exchange. Interestingly, two-step phase transformation processes from hexagonal CsMnCl₃ to rhombohedral Cs₄Pb_xMn_1−xCl₆ and finally to cubic CsPb_xMn_1−xCl₃ are evidenced. With an increase in the reaction time, Mn²⁺ ions in the PQD lattice are gradually replaced by Pb²⁺ ions. Notably, Mn²⁺ d → d broadband luminescence is not detected for the Cs₄Pb_xMn_1−xCl₆ product, but it is intense for the CsPb_xMn_1−xCl₃ sample owing to efficient energy transfer from CsPbCl₃ to Mn²⁺. Moreover, it is found that the introduction of Br⁻ into the reaction system will prohibit the complete phase transformation from rhombohedral Cs₄Pb_xMn_1−x(Cl/Br)₆ to cubic CsPb_xMn_1−x(Cl/Br)₃. By controlling the ratio between the CsMnCl₃ precursor and PbBr₂, tunable luminescence is easily achieved due to the combined emissions from both CsPb(Cl/Br)₃ PQDs and Mn²⁺-emitting centers.