Buried Interface Reconstruction Strategy Realizes Efficient and Stable Perovskite Solar Cells

Abstract The buried interface in n‐i‐p structured perovskite solar cells (PSCs), typically rich in defects, is a critical target for functional molecule passivation strategies to enhance device performance. In this study, three functional molecules bearing different electron‐withdrawing groups are investigated to modify the perovskite/electron transport layer (ETL) interface. Remarkably, all three molecules exhibit a dual‐anchoring behavior: simultaneously binding to the SnO 2 ETL surface using both head and tail functional groups, a binding mode not previously reported. Three passivation molecules bearing distinct electron‐withdrawing groups are designed and evaluated: sodium trifluoroacetate (NaTFA), sodium trifluoromethanesulfinate (NaTTSA), and sodium trifluoromethanesulfonate (NaTSA), collectively referred to as NaTXA. Among them, NaTSA containing a sulfonic acid (─SO 3 ) group, exhibits strongest interfacial binding and most effective passivation, outperforming NaTTSA (─SO 2 ) and NaTFA (─COOH). This enhancement is attributed to the stronger electron‐withdrawing nature of the ─SO 3 group and its favorable energy‐level alignment at the buried interface, which minimizes defects at the interface and ensures high‐speed carrier transport. As a result, the optimized device achieves a power conversion efficiency (PCE) of 25.60% with substantially improved operational stability. This work provides critical insights into functional group selection for interface engineering and deepens the mechanistic understanding of molecule‐mediated passivation strategies in PSCs.