Synthesis and Photoluminescence Modulation of Cs₄Cd_1-MnBi₂Cl₁₂-Based Two-Dimensional Layered Double Perovskites

Two-dimensional (2D) layered double perovskites have attracted much attention because of their excellent photoelectric properties. However, few reports have been published on the synthesis of 2D layered double perovskites from halide perovskites as precursors. Here, we report that CsCdCl₃ and Cs₃Bi₂Cl₉ were synthesized by the coprecipitation method, and a two-dimensional layered double perovskite Cs₄CdBi₂Cl₁₂ was readily synthesized by mixing the two halide perovskites. We doped different amounts of Mn²⁺ into CsCdCl₃ to form CsCd_1-MnCl₃, which introduced impurity states into the energy level and exhibited an orange-red light emission that is characteristic of Mn²⁺. A series of 2D layered double perovskites Cs₄Cd_1-MnBi₂Cl₁₂ were synthesized from CsCd_1-MnCl₃ and Cs₃Bi₂Cl₉, which showed a bright orange-yellow luminescence under ultraviolet excitation. The presence of high concentrations of Cd²⁺ in the two-dimensional layered double perovskites weakened the strong Mn-Mn coupling and suppressed the energy transfer to defects, thus minimizing nonradiative decay and promoting efficient energy transfer. Our work provides a new concept for the synthesis of low-dimensional metal halide perovskites with unique optical properties.