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

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.