Molecular Engineering of a Bidentate Thiol−Carboxylate Ligand for High Performance Wide-Bandgap Perovskite Solar Cells

Nonradiative recombination at the buried interface critically limits the performance of inverted wide-bandgap perovskite solar cells. To address this, we introduce 3-mercaptobenzoic acid (3-MBA) as a bifunctional cross-linker at the hole-transport-layer/perovskite interface. 3-MBA uniquely combines electron-donating carboxyl and electron-withdrawing thiol groups within a single molecular framework, enabling a dual-site coordination that enhances both defect passivation and energy-level alignment. Theoretical and spectroscopic evidence confirms that 3-MBA chelates undercoordinated Pb 2+ via S and O coordination, effectively passivating interface defects. This multifunctional interlayer reduces defect density, improves energy alignment and crystallinity, collectively suppressing recombination and accelerating hole extraction. Consequently, the modified devices achieve an efficiency of 21.3% with a high open-circuit voltage of 1.24 V. The prepared WBG PSCs retain 90.5% of their initial efficiency after 1400 h of aging at a relative humidity of ≈30% in air, indicating excellent humidity stability. This work establishes a rational design paradigm for chemically cross-linked interfaces to simultaneously boost efficiency and stability in perovskite photovoltaics.