Continuous synthesis of all-inorganic low-dimensional bismuth-based metal halides Cs4MnBi2Cl12 from reversible precursors Cs3BiCl6 and Cs3Bi2Cl9 under phase engineering

Abstract

Lead-free bismuth metal halide perovskites and their analogues have attracted much research interest for their excellent photoelectric properties. However, the synthesis of low-dimensional bismuth-based metal halide perovskites from bismuth-based perovskite-based precursors has rarely been reported. In this work, we report the synthesis of Cs₃BiCl₆ and Cs₃Bi₂Cl₉ using an improved room temperature, supersaturated recrystallization method, whereby the two precursors can be interconverted by addition of raw material post-synthetically, and both can be used as precursors together with suitable Mn²⁺ and other cations (Cs⁺, Bi³⁺), to synthesize fully inorganic, layered double perovskites, such as Cs₄MnBi₂Cl₁₂, which exhibit the bright orange-yellow light that is characteristic of Mn²⁺. We further demonstrate that partial replacement of Mn²⁺ by Cd²⁺ in Cs₄MnBi₂Cl₁₂ can weaken the strong coupling effect between Mn²⁺ and Mn²⁺, which inhibits the energy transfer to defects where non-radiative decay is likely to occur, and so achieves an effective energy transfer and thus improves the photoluminescence efficiency (PLQY). In the partially Cd²⁺-substituted, layered double perovskites, Cs₄Mn_1−xCd_xBi₂Cl₁₂, when x = 0.7 the PLQY reaches a maximum value of 57.2%. Our study provides a new approach for the design and synthesis of low-dimensional bismuth-based metal halides with flexibility in adjusting their optical properties.