Unraveling the Impact of Bromine Incorporation on the Hybrid Perovskite Film Phase Evolution Mechanism by In Situ Characterization

Abstract Hybrid organic‐inorganic perovskite materials have substantially boosted solar cell efficiency, but such multiple components complicate the crystallization kinetics and phase evolution process. In particular, the mechanisms underlying the film formation where small halide Br − is involved in, from precursor to solid‐state thin films as well as the process‐structure relationship, still need to be determined. In this study, the role of Br − ion in altering the crystallization kinetics and phase‐transition mechanism, is recognized using in situ characterization and density functional analysis method based on first principles. High‐quality perovskite film can be fabricated based on these results through precise compositional engineering. These results provide basic insight into the crystallization of hybrid perovskite materials with direct implications for fabricating high‐quality perovskite film and high‐performance perovskite solar cells.