Three-step approach for computing band offsets and its application to inorganic A B X3 halide perovskites

Band offsets between different semiconductors are important parameters that determine the electronic transport properties near the interface in the heterostructure devices. The computation of the natural band offset is a well-known challenge. In this paper, we propose a new method, which is called the three-step method, to accurately predict the natural band offset. Compared to previous methods, the present method is more direct and can be easily applied to systems with larger lattice mismatch and to systems with lower symmetry. Using the present method, we successfully calculate the natural band offset between the inorganic halide perovskites ABX(3) (A = Cs; B = Sn, Pb; X = Cl, B, I) in the cubic and orthorhombic phase. We show that the valence band maximum shifts down as the atomic number of the X site ion increases, while the valence band maximum shifts up as B site ion varies from Sn to Pb or as the compound transforms from the cubic phase to the orthorhombic phase. It is found that the band gap differences between these compounds can be attributed primarily to the valence band offsets, with a much smaller contribution from the conduction band offsets.