Functional organic cation induced 3D-to-0D phase transformation and surface reconstruction of CsPbI3 inorganic perovskite

Efficiency and stability are the main research focuses for perovskite solar cells. Inorganic perovskites like CsPbI3 possess higher chemical stability than those with organic A-site cations, while they also exhibit higher defect density. Nonetheless, it is highly challenging to induce orderly secondary arrangement or reconstruction of inorganic perovskites with reduced defects because of their unique chemical properties. In this work, in-situ three-dimension-to-zero-dimension (3D-to-0D) phase transformation and surface reconstruction on CsPbI3 film is achieved as induced by a functional organic cation, benzyldodecyldimethylammonium (BDA), a process of which that is similar to phase-transfer catalysis. With the help of BDABr salt treatment, 0D Cs4PbI6 perovskites are secondarily formed along CsPbI3 grain boundaries with Cs-related cationic defects passivated, yielding structures of higher stability. The BDA-CsPbI3 films exhibit reduced non-radiative recombination and promoted charge transfer, leading to inorganic perovskite solar cells with a high power conversion efficiency of 20.63% and good operational stability.