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 SnO2 precursor. The introduction of TC can efficiently inhibit the agglomeration of SnO2 nanoparticle in precursor. This also eliminates the oxygen vacancy defects and reduces the work function of the SnO2 film surface. This synergistic effect remarkably improves the quality of ETL. Meanwhile, TC can passivate the undercoordinated Pb2+ 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. Incorporating trisodium citrate (TC) into SnO2 precursor efficiently inhibits SnO2 nanoparticle agglomeration, eliminating defects and reducing surface work function of electron-transport layer. Additionally, enhanced interface interaction improves the stability of perovskite layer, resulting in a reduction in lead leakage. Finally, the modification with TC enhances the performance and stability of the fully air-processed perovskite solar cells.image (c) 2024 WILEY-VCH GmbH