Hydrostatic pressure-tuning of photoelectric properties of perovskite Cs2SeI6 through first-principles investigation

Pressure engineering can produce a inner change and atoms redistribution for perovskite Cs 2 SeI 6 . As a result, the photoelectric properties of perovskite Cs 2 SeI 6 would be varied under different pressure conditions. Base on the density functional theory (DFT), the photoelectric properties of perovskite Cs 2 SeI 6 under different hydrostatic pressure have been investigated by using the first-principles. The lattice constant, unit cell volume and bond length of perovskite Cs 2 SeI 6 are significantly reduced with the increase hydrostatic pressure. Moreover, perovskite Cs 2 SeI 6 has the optimal optical bandgap value of 1.34 eV under a pressure of 1.5 GPa. Therefore, we only study the photoelectric properties of Cs 2 SeI 6 when the hydrostatic pressure is 0 and 1.5 GPa in this paper. The calculated results show that Cs 2 SeI 6 is stable under the pressure of 0 GPa and 1.5 GPa according to the calculations of Born-Huang stability criterion and phonon dispersion spectrum. It can be found that perovskite Cs 2 SeI 6 are all soft, ductile and anisotropic before and after pressure. In addition, when the hydrostatic pressure is 1.5 GPa, perovskite Cs 2 SeI 6 has larger values of dielectric functions, absorption coefficient and optical conductivity. This study indicates that perovskite Cs 2 SeI 6 is an excellent photovoltaic material after applied hydrostatic pressure, which has great potential in application of perovskite solar cells. Crystal structure of perovskite Cs 2 SeI 6 .