where N A is the number of atoms in the supercell, and p i is the local density of states for each atom i, calculated using the HSE06 functional. An IPR of 1 indicates that an electronic state is fully delocalized, while a value of 1024 (= N A ) corresponds to localization on a single atom. To compare the IPR of different cation configurations, the energies were aligned using the core states. Figure shows that as temperature increases, the valence band maxima (VBM) and the conduction band maxima (CBM) both shift, decreasing the bandgap, with a maximum IPR of 40 obtained at the VBM at T = 700 K. This increase in localization at the VBM can hamper carrier transport. From the charge densities, the VBM goes from being composed of Sn s -I p interactions in the metal-halide polyhedras to being localized around the longest grouping of Sn along the M 2 S 2 chains at 700 K (Sn s, S p and I p). The decrease in the CBM energy is less gradual, with a large reduction at 400 K coinciding with the order-disorder phase transition. The charge densities show a slight increase in localization on Sb sites; however, this is significantly reduced in comparison to the VBM, with a max IPR of 3 at 700 K. The increase in localisation can also be seen in flat VBM of the unfolded band structure of a 600 K disordered supercell (Figure ). It is of note that no defect states are formed in the bandgap, in contrast to other cation-disordered chalcogenides and pnictides, indicating the disorder in this system may not accelerate non-radiative charge-carrier recombination -a promising sign for photovoltaic operation.