An Emerging All-Inorganic CsSnxPb1–xBr3 (0 ≤ x ≤ 1) Perovskite Single Crystal: Insight on Structural Phase Transition and Electronic Properties

Owing to the high toxicity of Pb-based hybrid perovskites, a hypotoxic element, e.g., Sn, was employed to partially or completely replace Pb with the aim of gaining environmentally friendly lead-free photoelectronic device. Herein, for the first time we hydrothermally grow a series of all-inorganic CsSnxPb1–xBr3 (0 ≤ x ≤ 1) perovskite single crystals and carefully study their crystallographic structure and electronic structure that are subject to the varied x value. The phase transition and narrowed band gap from CsPbBr3 to CsSnBr3 are observed, which is similar to the evolution of MASnxPb1–xBr3 perovskites while varying the ratio of Sn/Pb. Likewise, the incremental concentration of Sn atoms in the lattice tend to cause the energy level splitting that likely derives from the orbital overlapping between Sn and/or Pb atoms, which thereby gives rise to the narrowed band gap. Equally important is that the incorporation of Sn atoms is demonstrated to be capable of tightening the electron orbital coupling between Sn and/or Pb atoms, which thereafter enables advantageous balancing of the orbital overlap in the crystal structure with balanced and highly ordered arrangement of [SnBr6]4– and/or [PbBr6]4– octahedra and thus allows us to improve carrier transport and to benefit the real ecofriendly application of photoelectronic devices.