Crystalline engineering of FAPbI pyrrolidinium ionic liquid for stable perovskite solar cells with 21.72% efficiency.

Improving the crystallinity of formamidinium triiodide (FAPbI) perovskite layer is one of the most effective approaches to increase the photovoltaic performance and stability of FAPbI-based solar cells (FSCs). In the current study, FAPbI layers were fabricated through a sequential deposition method. The morphology and crystalline properties of the FAPbI layers were modified by controlling the lead iodide (PbI) precursor by adding pyrrolidinium (Pyr) material into the PbI layer and modulating the FAPbI crystallization.