Pressure induced structural, electronic and optical properties of CsPbI3 perovskite†

Abstract

All inorganic CsPbI₃ perovskites have emerged as a potential candidate for next-generation photovoltaics (PVs) and optoelectronics. In this article, the influence of hydrostatic pressure on the structural, electronic, and optical properties of CsPbI₃ perovskites was investigated using first-principles calculations within the framework of density functional theory (DFT). At 0 GPa, the orthorhombic δ-phase was found to be the most stable phase, while the α-phase is the most unstable phase. Within the applied pressure range of 0–2 GPa, δ-CsPbI₃ was found to be thermodynamically stable; however, β- and γ-CsPbI₃ exhibited thermodynamic stability up to 0.8 and 1.6 GPa. On the contrary, the cubic phase was thermodynamically stable only at 0 GPa. Phonon dispersion relations revealed that α- and β-phases are dynamically unstable, whereas γ-CsPbI₃ is dynamically stable within the applied pressure range. Electronic structure results revealed that the band gap of α- and β-CsPbI₃ decreases with increasing pressure, whereas γ-CsPbI₃ showed a non-monotonic band gap variation as a function of pressure. In addition, all the three phases exhibited strong optical absorption in the visible region, and the absorption peak was radically red-shifted with applied pressure. These findings would be beneficial for experimental study and imply that pressure plays an important role in determining the properties of the CsPbI₃ perovskite.