Internal and external pressure in cubic perovskites: electronic structure effects and systematic accuracy from first principles

Abstract

Pressure is an invaluable tool to manipulate properties of materials. Here, we present an in-depth theoretical study of the effect of structural variation on the electronic properties of cubic ABX3 perovskites where A = Cs, CH3NH3, B = Pb, Sn and X = Cl, Br, I. Cubic ABX3 perovskites with structural and constituent variations are modeled using hybrid DFT, with comparison to experimental results. Our results demonstrate that while the direction of electronic change can be predicted for a set of perovskites where two variables are kept fixed, magnitude of change between a set, and relative electronic properties of different perovskites are much more complicated to predict. We attribute this effect to structural variation among perovskites. The valence band maximum position lowers dramatically with an increase in external pressure, and with a decrease in internal pressure. This study also demonstrates strong band gap changes which arise from isotropic structural change due to pressure, showing the potential for lattice strain to be employed in future solar cell materials design, but also cautions against reliance upon first principles calculations in prediction of relative electronic properties across perovskite sets with different constituents.