Lead-Free Antimony Halide Perovskite with Heterovalent Mn²⁺ Doping

Lead toxicity is hindering the applications of conventional lead halide perovskites (PVKs), and antimony (Sb) is a promising nontoxic Pb alternative, showing huge potential in optoelectronic devices. Herein, pure and Mn-doped Cs₃Sb₂Cl₉ crystals are synthesized in a facile route and studied both experimentally and theoretically. All the pure and Mn-doped Cs₃Sb₂Cl₉ crystals show good crystallinity and similar crystal structures, exhibiting visible photoluminescence (PL) characteristics with emission peaks at 422 and 613 nm, respectively. Combined density functional theory (DFT) calculations and experimental analyses reveal that the structure of the host PVK compound Cs₃Sb₂Cl₉ is not influenced by the formation of [MnCl₆]^4- octahedra and that Mn 3d orbitals generate impurity states in the forbidden energy gap of Cs₃Sb₂Cl₉. Therefore, energy transfer from Cs₃Sb₂Cl₉ to Mn 3d states is observed, resulting in the d-d transition and bright red luminescence. Mn-doped Sb-based PVK can be utilized as a new platform for optoelectronic applications.