Electronic properties of CsSnBr3: studies by experiment and theory

In this paper, the band structure of cubic and tetragonal phases of CsSnBr3 has been investigated by temperature-dependent UPS and XPS in conjunction with ab initio calculations. The calculated results show that when CsSnBr3 changes from a cubic phase to a tetragonal phase, the conduction and valence bands show slight changes accordingly. The density of states of Br (4s and 4p) in the valence band increases with the phase transition from cubic to tetragonal, whereas those of Cs and Sn show almost no changes. Both cubic and tetragonal phases of CsSnBr3 show semiconductor character with bandgaps near the Fermi levels. The bandgap of the cubic phase at R k-point is calculated to be 0.42 eV, whereas those of the tetragonal phase at the A k-point are 0.41, 0.40 and 0.35 eV for c/a = 1.01, c/a = 1.02 and c/a = 1.04, respectively. The calculated results are in agreement with UPS and XPS measurements, and indicate direct correlation between the electronic structure and structural phase transitions.