Chemical trends of absolute volume deformation potentials of all-inorganic ABX₃ halide perovskites

The absolute volume deformation potential (AVDP) is an important physical quantity that describes the energy level shift under pressure, which, however, has not been investigated for halide perovskites. We systematically calculate the valence band maximum (VBM) and conduction band minimum (CBM) AVDPs of all-inorganic ABX₃-type perovskites (where A = K, Rb, Cs; B = Ge, Sn, Pb; X = Cl, Br, I) in cubic structure using ab-initio calculation methods. Although it was shown that spin-orbit coupling played an important role in the band structure calculation of ABX₃ perovskite, we prove that it has negligible effect on AVDP calculation. We show that the AVDPs of VBM are all negative and large, indicating the energy level will shift down when the volume increases, while AVDPs of CBM are mostly positive and small. There are clear trends in the calculated AVDPs of both VBM and CBM which will be discussed. Our results suggest that strain is an effective way to adjust the energy level of valence band edge in ABX₃, which may be of great significance to design optoelectronic devices.