Intermolecular Interaction Induced Synergistic Passivation toward Efficient and Stable 1.68 eV Bandgap Perovskite Solar Cells

Abstract The performance and stability of wide‐band‐gap (1.68 eV) perovskite solar cells (PSCs) are critically constrained by two main challenges: i) nonradiative recombination and ii) insufficient environmental stability. In this study, a chemical synergistic passivation strategy is presented, which combines oleic acid (OA) with phenylethylammonium iodide (PEAI). The neutralization reaction between OA and PEAI forms amide groups (─CONH), giving the new passivator (O‐PEAI) a high acid dissociation constant (pK_a). This effectively suppresses the deprotonation of PEA⁺ and prevents the formation of PEA₂PbI₄. The amide groups (─CONH) from O‐PEAI and the carboxyl groups (─COOH) from OA exert a chemical synergistic passivation effect on surface defects and modulate the surface potential. In comparison with the perovskite films treated by PEAI alone, the carrier lifetime of O‐PEAI treated samples increased from 0.179 to 0.270 µs, and the carrier transfer rate between perovskite/PCBM increased sevenfold. The resulting PSCs achieved a champion power conversion efficiency as high as 22.46%. Moreover, due to the hydrophobic alkyl chain of OA, the unencapsulated devices retain 90.4% of their initial efficiency after 1000 h of storage in ambient conditions (40% relative humidity). This study offers a promising pathway for improving the efficiency and durability of wide‐band‐gap PSCs.