Multi-scale model for the structure of hybrid perovskites: Analysis of charge migration in disordered MAPbI₃ structures

We have developed a multi-scale model for organic-inorganic hybrid perovskites (HPs) that applies quantum mechanical (QM) calculations of small HP supercell models to large coarse-grained structures. With a mixed quantum-classical hopping model, we have studied the effects of cation disorder on charge mobilities in HPs, which is a key feature to optimize their photovoltaic performance. Our multi-scale model parametrizes the interaction between neighboring methylammonium cations (MA⁺) in the prototypical HP material, methylammonium lead triiodide (CH₃NH₃PbI₃, or MAPbI₃). For the charge mobility analysis with our hopping model, we solved the QM site-to-site hopping probabilities analytically and computed the nearest-neighbor electronic coupling energies from the band structure of MAPbI₃ with density-functional theory. We investigated the charge mobility in various MAPbI₃ supercell models of ordered and disordered MA⁺ cations. Our results indicate a structure-dependent mobility, in the range of 50-66 cm² V^-1 s^-1, with the highest observed in the ordered tetragonal phase.