Bifunctional Interfacial Regulation with 4‐(Trifluoromethyl) Benzoic Acid to Reduce the Photovoltage Deficit of MAPbI₃‐Based Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs), which have recently achieved more than 25% efficiency, are highly promising candidates for renewable energy generation. However, the interface of these solar cells is not yet fully understood. Herein, we used self‐assembled monolayers (SAMs) to regulate the interface of a SnO₂ electron transport layer (ETL) and a common MAPbI₃ perovskite absorber. Three different monolayers indicate that the contiguous terminal groups and charge distribution of their molecules influence interfacial properties and photovoltaic performance. Aligned energy levels, lower surface tension, and higher quality perovskite crystallization were obtained after SAM regulation. Consequently, applying a 4‐(trifluoromethyl) benzoic acid (BA‐CF₃) SAM improved the power conversion efficiency (PCE) of the resulting PSC from 16.84% to 18.67%. Moreover, a high open‐circuit voltage (V_OC) of 1.160 V was achieved with significantly reduced defects and non‐radiative recombination. This work highlights the regulation of these interfaces by a molecule for achieving high‐performance PSCs.