Interfacial Modification by Low‐Temperature Anchoring Surface Uncoordinated Pb for Efficient FAPbI₃ Perovskite Solar Cells

Abstract Surface modification of perovskite film plays an important role on the suppression of surface defects for the fabrication of high‐efficiency perovskite solar cells. Here, 1H‐Pyrazole‐1‐carboxamidine hydrochloride (PAH) as a multifunctional heterocyclic ring‐based organic ionic salt to modify the surface of FAPbI₃ film at room temperature is demonstrated. XPS and FTIR results demonstrate that the sufficient active sites contribute to the interaction between PAH and surface Pb ions of the perovskite, which is helpful to reduce the trap states on the perovskite film so as to increase the device performance. The modification is beneficial to the suppression of charge recombination and the promotion of charge transfer by anchoring to the uncoordinated Pb ions on the surface both at the interface of stacking layers and the grain boundary. With prolonged charge carrier lifetime and elevated charge transfer, an improved PCE of 20.9% is obtained for the as‐prepared planar devices based on FAPbI₃, along with simultaneous enhancement of open circuit voltage and fill factor. The findings further pave the way for utilizing novel organic salts for surface modification, which presents a promising route for the fabrication of efficient photovoltaic devices.