Coordination modulated crystallization and defect passivation in high quality perovskite film for efficient solar cells

Hybrid perovskite solar cells (PSCs) have come into prominence as a potential alternative to crystalline silicon solar cells due to their outstanding photovoltaic performance and the simple manufacturing process. Over the past few years, the performance has greatly benefited from the emergence of advanced fabrication technologies capable of producing high quality perovskite films. The transforming process from precursor to perovskite film directly influences the film quality by controlling the nucleation and crystal growth. In particular, the coordination of electron-rich atoms in solvent or additives with Pb ions in perovskite precursor has been widely used to modulate the crystal growth to obtain compact and dense perovskite film with fewer defects. Here, a systematic review is presented to describe the effect of coordination interaction on perovskite crystallization process, defects passivation, hysteresis behavior and long-term stability for efficient perovskite thin film and related photovoltaics. Functional additives with carbonyl-, acyl- and cyano- group bearing lone electron pairs have been widely adopted to coordinate with PbI₂ to retard crystallization and obtain a high-quality perovskite film. Meanwhile, these additives can modify the surface or grain boundary of as-formed perovskite film to passivate defects, mitigate hysteresis and prevent the moisture permeation to prolong the device lifetime. The coordination interaction provides a feasible strategy to improve the perovskite film quality, which is crucial to increase the efficiency and longevity of PSCs and other related optoelectronic devices towards future upscaling and commercialization.