Thermoelectric property analysis of CsSnX3 materials (X = I, Br, Cl)

The thermoelectric properties of CsSnI₃ are analysed with the ab initio first-principle density functional theory (DFT). Seebeck coefficient, electrical and thermal conductivities are calculated in order to determine the dimensionless figure of merit ZT. Knowing that CsSnI₃ is one of the perovskite series of materials that undergo complex phase transitions with temperature, the calculations are performed for different common phases. Several phases of CsSnBr₃ and CsSnCl₃ are also analysed as comparisons. For the same material, comparison of band structures showed that the band gap increases with phase transition from phase - α to phase - β then to phase - γ. And the ZT values show the same trend as the band gaps. CsSnCl₃ exhibits a higher ZT value than CsSnBr₃ and CsSnI₃ at phase-α.