The Multisite Interactions Based on the Long-Chain Functionalized Ionic Liquids for Efficient Regulation of High-Quality Perovskite Films and Solar Cells in Air

Perovskite solar cells (PSCs) have become a highly promising photovoltaic technology, which can be attributed to their distinctive advantages. The quality of the perovskite thin films plays a crucial role in determining the photovoltaic performance of PSCs. Ionic liquids (ILs) have demonstrated efficacy in passivating defects within perovskite thin films. However, certain aspects remain inadequately addressed, particularly the microscopic interaction mechanisms between ILs and perovskites. In this study, a long-chain functionalized IL (VC₁₂ImBr) was developed as an effective regulatory material for preparation of high-performance perovskite films and devices in air. The mechanism by which VC₁₂ImBr affects the optoelectronic properties of perovskite films and devices has been elucidated through an integration of theoretical simulations and a range of in situ experimental characterization techniques. In situ characterization revealed that VC₁₂ImBr precisely regulates the crystallization process of perovskite, effectively passivating the film defects and achieving high-quality perovskite films. Ultimately, the power conversion efficiency (PCE) of the device modified with VC₁₂ImBr prepared in air was effectively improved by about 15% with superior long-term stability.