Hopscotching perovskites: DFT leveraged tight-binding insights into inorganic lead halide perovskites

Delocalization insights into inorganic lead halide perovskites of the form CsPbBr_xI_3-x (x = 0, 1, 2, 3), obtained via a DFT based tight-binding method, are presented. Compared to first principles studies like DFT (physically accurate and computationally expensive), the tight-binding approach allows the disentanglement of the region of interest, namely, the Fermi level. Further adjustment of the hopping norm and maximum distance leads to a simplified, highly interpretable but chemically grounded, reduced model which regenerates the broad features of the band structure with a fraction of the parameters. We observe that due to the delocalized nature of its orbitals, CsPbBrI₂ follows a many-small hopping scheme, markedly different in character from the few-big strategy taken by the other members of the set. Finally we leverage the tight-binding model to study the electronic and thermal transport properties of these materials. These insights enable the identification of optimal doping strategies that could enhance the thermoelectric performance of these materials.