Role of Halogen Atoms on High-Efficiency Mn2+ Emission in Two-Dimensional Hybrid Perovskites

Doped halide pervoskites as highly efficient light emitters have recently fascinated the research community, while the influence of halogen atoms X (X = Cl, Br, I) on the hybrid energy levels and photoluminescence properties remains a challenge. Here, the role of X compositions in the two-dimensional hybrid perovskite BA₂PbX₄ (BA = C₄H₉NH₃) on the doped Mn²⁺ emission is identified, wherein Mn²⁺ reveals a strong luminescence dependence on the nature of the halogen, and optimum Mn²⁺ emission with a record quantum yield of 60.1% has been achieved in BA₂PbBr₄. Density functional theory calculations show that BA₂PbBr₄ holds low Br vacancy concentration and unique coupled states of the Mn-3d level and Pb-6p level at the conduction band minimum, leading to efficient energy transfer from the host to Mn²⁺. Our work sheds new light on the methods to realize strong exciton–dopant exchange coupling for achieving high-efficiency dopant luminescence.