Effect of pressure-induced structural phase transition on electronic and optical properties of perovskite CH3NH3PbI3

摘要

Perovskite structure CH3NH3PbI3 has been receiving considerable attention due to its promising applications in many optoelectronic fields such as photovoltaics, photodiodes, sensors and catalysts. As studying the structural and optoelectronic properties of CH3NH3PbI3 under pressure can be beneficial to explore unusual lattice structures, new chemical and physical properties of this material, first-principles calculations based on density functional theory have been performed in this work to investigate the electronic and optical properties of CH3NH3PbI3 under pressure. Moreover, the standard deviation sigma of Pb-I bonds in [PbI6](4-) octahedrons were used for the first time to characterize the distortion degree of octahedrons. It is found that both the decrease of Pb-I bond lengths and the distortion of [PbI6](4-) octahedrons in CH3NH3PbI3 under pressure have significant effects on the band gap changes of tetragonal, cubic and orthorhombic structures of CH3NH3PbI3. The interactions between Pb and I atoms in three structures have mixed covalent and ionic bonding characters, the covalent character of Pb-I bonds is quite weak in comparison with the classical C-N covalent bonds. The optical properties including the complex dielectric function, refractive index, extinction coefficient, reflectivity and absorption coefficient for three CH3NH3PbI3 structures under pressure were also determined.