Intrinsic Self-Trapped Emission in 0D Lead-Free (C₄ H₁₄ N₂ )₂ In₂ Br₁₀ Single Crystal

Low-dimensional lead halide perovskite materials recently have drawn much attention owing to the intriguing broadband emissions; however, the toxicity of lead will hinder their future development. Now, a lead-free (C₄ H₁₄ N₂ )₂ In₂ Br₁₀ single crystal with a unique zero-dimensional (0D) structure constituted by [InBr₆ ]^3- octahedral and [InBr₄ ]^- tetrahedral units is described. The single crystal exhibits broadband photoluminescence (PL) that spans almost the whole visible spectrum with a lifetime of 3.2 μs. Computational and experimental studies unveil that an excited-state structural distortion in [InBr₆ ]^3- octahedral units enables the formation of intrinsic self-trapped excitons (STEs) and thus contributing the broad emission. Furthermore, femtosecond transient absorption (fs-TA) measurement reveals that the ultrafast STEs formation together with an efficient intersystem crossing has made a significant contribution to the long-lived and broad STE-based emission behavior.