Synthesis of Highly-Oriented Black CsPbI₃Microstructures for High-Performance Solar Cells

Synthesis of a thin layer of perovskite with less pinholes and defects is vital for the construction of a high-performance perovskite solar cell (PSC). We report on an oriented attachment strategy to fabricate a black phase CsPbI3 highly oriented quasi-single-crystalline microstructure film for constructing a mesoporous PSC device with enhanced power conversion efficiency, from 13.4% to 16.0%. The theoretical calculations and detailed in/ex situ characterizations demonstrate that the oriented attachment is driven by the predominant adsorption of dimethyl sulfoxide (DMSO) on the {212} facets of the yellow phase δ-CsPbI3 crystals which initially form a relatively oriented structure followed by phase transition to α-CsPbI3 crystals and merging into a large highly oriented quasi-single-crystalline microstructure film with {200} planes exposed under annealing. Our work demonstrates that the oriented attachment strategy enables the formation of highly oriented quasi-single-crystalline perovskite microstructure films which are essential for realizing high-efficiency and stable thin film PSCs.