Antimony doping to enhance luminescence of tin(iv)-based hybrid metal halides

Lead-based organic-inorganic metal halides (OIMHs) have recently attracted special attention due to their efficient broadband photoluminescence. However, the toxicity of lead poses a challenge for their further development. Here, we selected Sn(iv) as the metal center to synthesize the environmentally friendly and stable luminescent OIMHs (C₉H₁₅N₃)₂SnCl₈ and (C₉H₁₅N₃)₂SnBr₈ (C₉H₁₃N₃ is 1-(2-pyridyl)piperazine). Both compounds possess zero-dimensional structures, crystallizing in the monoclinic space group P2₁/c, and their optical band gaps were experimentally determined to be 3.19 and 2.60 eV, respectively. Under UV excitation at room temperature, (C₉H₁₅N₃)₂SnCl₈ exhibited double-peak emissions centered at 405 and 688 nm, which were attributed to the organic cation and inorganic octahedra, respectively. Upon introducing 5s²-lone-pair-containing Sb³⁺ in (C₉H₁₅N₃)₂SnCl₈, self-trapped emission was promoted, and the photoluminescence quantum yield increased from ∼1% to ∼17.84%. This work suggests effective strategies for finding environmentally friendly stable OIMHs and for further enhancing the luminescence properties through lone-pair-containing cation doping.