Effect of atomic configuration on band gap behaviour in CH3NH3SnxPb1−xI3 perovskites

• Published in: Physics letters. A Vol. 384; no. 8
• Main Authors: Guan, Li, Xu, Xiaofang, Liang, Yanan, Han, Shichuang, Guo, Jianxin, Wang, Jianglong, Li, Xu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.03.2020
• Subjects: Atomic configuration; Band gap; First-principles; Organometal halide perovskites; Atomic configuration; Band gap; Organometal halide perovskites; First-principles
• ISSN: 0375-9601; 1873-2429
• DOI: 10.1016/j.physleta.2019.126173

The atomic structure and electronic properties of Sn/Pb mixed organometal halide perovskites were investigated by using first-principles method. The structure-dependent band gap behaviour of tetragonal and pseudocubic MASnxPb1−xI3 (0⩽x⩽1) was emphasized. The configurations with two or more adjacent Sn octahedra in the same layer inducing less tilting of neighbouring octahedra have the lower formation energy. For tetragonal or pseudocubic MASn0.5Pb0.5I3, the configuration of Sn octahedra layer alternating with Pb octahedra layer leads to elongated octahedra along the stacking direction, which stimulates the remarkable band splitting due to anomalous hybridization of Pb or Sn orbitals and I orbitals. This arrangement mode of Sn octahedra produces the narrowest band gap of Sn/Pb binary perovskite, whereas the separated and dispersed Sn octahedra significantly broaden the band gap. The results are helpful to understand the abnormal band gap behaviour in Sn/Pb binary perovskite experiments. •Structure-dependent band gap behaviour of tetragonal and pseudocubic MASnxPb1−xI3.•Sn octahedra layer alternating with Pb octahedra layer leads to the narrowest band gap.•Distortion of octahedra induces the splitting and shift of band edges.•Pseudocubic phase exhibits a more tunable band gap than in low-symmetry tetragonal phase.•PBE and PBE0 methods give the similar tendency of band gap with composition.