  Density functional theory (DFT) based calculations have been conducted 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 pressure applied, distinct band structure behaviors including magnitude
change of band gap, direct-indirect/indirect-direct band gap transitions and
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 orbitals
coupling transformations; direct-indirect mutual transitions were explained
based on structural symmetry evolution; different VBM/CBM shifts behaviors
between organic and inorganic perovskites were analyzed focusing on orientation
and polarity of molecules/atoms outside the octahedrals. These results provide
a comprehensive guidance for further experimental investigations on pressure
engineering of perovskite materials.

Materials Science