Pressure-Induced Band Structure Evolution of Halide Perovskites: A First-Principles Atomic and Electronic Structure Study

Density functional theory-based calculations have been carried out to draw a broad picture of pressure induced band structure evolution in various phases of organic and inorganic halide perovskite materials. Under a wide range of applied pressures, distinct band structure behaviors, including the magnitude change of band gaps, direct-indirect/indirect-direct band-gap transitions, and conduction band minimum/valence band maximum (CBM/VBM) shifts, have been observed between organic and inorganic perovskites among different phases. Through atomic and electronic structure calculations, band-gap narrowing/widening has been rationalized through crystal orbital coupling transformations; direct-indirect mutual transitions were explained on the basis of structural symmetry evolution; different VBM/CBM shift behaviors between organic and inorganic perovskites were analyzed focusing on orientation and polarity of molecules/atoms outside the octahedrals. These results provide comprehensive guidance for further experimental investigations on pressure engineering of perovskite materials.