Tailoring of Photoluminescence Properties in All‐Vacuum Deposited Perovskite via Ruddlesden–Popper Faults

Abstract Ruddlesden–Popper (RP) faults are well known in oxide perovskites, and are also observed in promising metal halide perovskites. However, the effect of RP faults on optical properties of perovskite has not been systematically investigated. In this study, it is found that RP faults are common planar faults in all‐vacuum deposited CsPbBr 3 ‐based perovskite polycrystal thin films, and the density of RP planar faults can be greatly increased by non‐stoichiometric composition (Cs‐rich) as well as reduced dimensionality (quasi‐2D) strategies. The photoluminescence (PL) measurement reveals monotonically increasing peak intensities with higher densities of RP planar faults from Cs‐rich, quasi‐2D to Cs‐rich & quasi‐2D samples. The corresponding atomic‐scale differential phase contrast maps indicate strongly confined charges within the RP planar fault network, which explains well the relationship between PL enhancement and the density of RP planar faults, and offers an alternative pathway for tailoring the optoelectronic properties of perovskite.