Hydrostatic pressure-tuning of thermoelectric properties of CsSnI₃ perovskite by first-principles calculations

Pressure engineering is a conventional approach to modify the material's interatomic bond length, density, forces as well as other intrinsic properties. The effects of hydrostatic pressure on the electronic and thermoelectric properties of n-type halide perovskite CsSnI₃ have been investigated using first-principles approach with spin–orbit coupling included. Electronic structure analysis illustrates that the material is a direct gap semiconductor. The partial charge density calculation suggested that electrons from Cs atoms do not contribute to the valence bonding instead assist in balancing the overall charge distribution. The material's bandgap decreases with applied pressure up to 1.7 Gpa, where band inversion was observed, after which further compression widened the energy gap. Accompanying with Boltzmann's theory, it was shown that CsSnI₃ is a potential candidate for thermoelectric energy harvesting. Hence, materials modification through pressure application is an effective approach to tune the electronic structure and thermoelectric properties of CsSnI₃. We achieved the optimum ZT of 1.26 at 1 Gpa pressure and 600 K temperature, close the band inversion region.