First-principles investigations on the physical properties of the double perovskite Cs2OsI6

Abstract

The double perovskites, as a novel material with promising applications in solar cells, have garnered significant research interest. The mechanical, electrical, optical, and thermodynamic characteristics of Cs2OsI6 are systematically studied using first-principles calculations. The material's mechanical stability satisfies the Born criteria, and it exhibits commendable elasticity and anisotropy. The application of the HSE06 hybrid functional reveals that Cs2OsI6 has a direct band gap of 1.14 eV at the Γ-point, with electronic states primarily originating from the I-p orbitals and Os-d orbitals. The optical properties, including the dielectric function, refractive index, and absorption coefficient, indicate that it has a strong UV absorption capacity. The thermodynamic properties, including the Debye temperature, heat capacity, enthalpy, entropy, and free energy, conform to the laws of thermodynamics. The results indicate that Cs2OsI6 exhibits good stability with changes in temperature. In addition, it has a suitable band gap and a strong light absorption coefficient, making it suitable for photovoltaic applications. It has great potential to be a candidate for perovskite solar cell materials.