Аннотация
ABSTRACT Facet engineering of lead‐free halide double perovskites is pivotal for regulating their microscopic physicochemical properties but remains highly challenging. Here, we synthesize Cs 2 AgBiBr 6 single‐crystalline microsheets with exposed (100) and (111) facets via an additive‐free, intermediate state‐dependent spatially confined anti‐solvent crystallization method. The (111) facet of Cs 2 AgBiBr 6 is thermodynamically preferred, possessing the lowest intrinsic surface energy, while our synthetic strategy effectively stabilizes the energetically unfavorable (100) facet. We demonstrate remarkable optoelectronic differences in different exposed facets of Cs 2 AgBiBr 6 . Specifically, the (100)‑faceted Cs 2 AgBiBr 6 possesses a higher surface defect‑state density, which directly results in a dark current one order of magnitude lower than that of its (111)‑faceted counterpart, while the (111)‑faceted crystals yield a higher photocurrent. This work not only provides a synthetic strategy for the facet engineering of lead‐free halide perovskites, but it also offers key insights into the directed optimization of their optoelectronic properties.