Dual-Interface Passivation of Wide-Bandgap Perovskite Films for Efficient Four-Terminal Perovskite–Organic Tandem Solar Cells

Interface defects in perovskite solar cells (PSCs) can significantly impair device efficiency by promoting nonradiative recombination, hindering charge transport, and facilitating ion migration. In this work, we introduce a dual-interface passivation strategy utilizing 2-(N-morpholino)­ethanesulfonic acid potassium (MESK) and octylammonium iodide (OAI), targeting both the electron transport layer (ETL)/perovskite and perovskite/hole transport layer (HTL) interfaces to enhance the efficiency of wide-bandgap PSCs based on FA_0.8Cs_0.2Pb­(I_0.6Br_0.4)₃ with a bandgap of 1.77 eV. The sulfonic group in MESK passivates bottom interface defects through coordination with Pb ions, while the amine group in OAI interacts with Pb and halide ions to effectively passivate top interface defects. The dual-interface passivation strategy improves perovskite crystallinity, enlarges grain size, and reduces nonradiative recombination. As a result, the performance of PSCs is significantly enhanced, achieving a power conversion efficiency (PCE) of 23.69% in a four-terminal (4T) perovskite–organic tandem solar cell (TSC), which provides a promising and sustainable solution for the commercialization of TSCs.