Investigating Bromine Vacancy Coordination in CsPb(1-x)SnxBr2.875

Halide perovskites are an important new class of materials for photovoltaic applications, providing high energy efficiency along with cheap solution-based synthesis methods. Initial research hypothesized that halide perovskites are ‘defect tolerant’, but more recent reports have revealed that low defect densities are the most likely cause for the surprisingly high energy efficiency of halide perovskites [Zhang et al., J. Appl. Phys. (2022) 131, 090901]. Therefore, optimizing the performance of halide perovskites requires minimizing recombination rates through control over defect energy levels. We investigate the interplay between Br vacancies and B cation mixing in CsPb(1-x)Sn(x)Br2.875. We use first principles density functional theory calculations to identify trends in the electronic structure and propose design rules for optimizing the ratio of B-site cations in halide perovskites.