First principles investigations to study the impact of hydrostatic pressure on optoelectronic properties and stability of Rb2PdBr6

In this article, the effect of hydrostatic pressure upon the optoelectronic performances of the perovskite Rb2PdBr6 was investigated by using first principles calculations. The calculated results imply that the band gap of the perovskite Rb2PdBr6 can change with hydrostatic pressure. The energy band gap of Rb2PdBr6 can be decreased to 1.341 eV when 1.2 GPa hydrostatic pressure is applied. This band gap value greatly approaches the optimal band gap value (1.34 eV) of PSCs. After finding the optimal band gap value of perovskite Rb2PdBr6, we compare the optical properties of perovskite Rb2PdBr6 under the hydrostatic pressure of 0 GPa, 1 GPa, 1.2 GPa, 1.5 GPa, respectively. The results show that the band gap reduction of Rb2PdBr6 under hydrostatic pressure leads to some superior optical properties such as improved light-absorbing ability, superior dielectric capability, and preferable charge transportation performance. The calculated lattice parameters show that the perovskite Rb2PdBr6 maintains a stable cubic spatial structure under hydrostatic pressure, and the elastic modulus complies with the criterion of mechanical stability. Meanwhile, there is no negative frequency component in the computed phonon dispersion spectra. The superior optoelectronic performance along with beneficial stability under hydrostatic pressure make Rb2PdBr6 more suitable for PSCs.