Enhancing Interface Interaction through Multifunctional Trisodium Citrate Modification of Electron‐Transport Layer in Fully Air‐Processed Perovskite Solar Cells

Electron‐transport layer (ETL) is integral in conventional perovskite solar cells (PSCs), serving as an essential role in both the growth of perovskite and the extraction of charge carriers. This dual functionality poses a challenge, especially in the context of the ETL in all‐air‐processed PSCs. Herein, a multifunctional modification strategy is proposed, where trisodium citrate (TC) is incorporated into SnO 2 precursor. The introduction of TC can efficiently inhibit the agglomeration of SnO 2 nanoparticle in precursor. This also eliminates the oxygen vacancy defects and reduces the work function of the SnO 2 film surface. This synergistic effect remarkably improves the quality of ETL. Meanwhile, TC can passivate the undercoordinated Pb 2+ at the buried interface, thus suppressing nonradiative recombination and reducing lead leakage. Furthermore, Na ions in the TC molecule facilitate the perovskite crystallization by migrating into the perovskite layer, resulting in formation of a high‐quality perovskite film. Consequently, the efficiency of the TC‐treated device made in fully ambient‐air conditions reaches 21.17% with suppressing hysteresis. In particular, the unencapsulated device maintains about 81% of the original efficiency after 2500 h under air exposure. In this study, a straightforward and effective method is presented for achieving efficient and stable air‐processed PSCs.