Bifunctional Ligand-Mediated Dual-Site Passivation Enables High-Performance Perovskite Solar Cells with Efficiency Exceeding 26%

The characteristics of perovskite solution processing inherently led to the formation of lattice defects during fabrication, such as lead and iodine vacancies. These defects significantly hinder the efficiency and stability of perovskite solar cells (PSCs), posing a major obstacle to their commercialization. Herein, a bifunctional ligand, N-hydroxymethyl succinimide (NHMS), containing both Lewis base groups (C═O) and proton donor groups (─OH), is introduced to improve the crystal quality of perovskite films and enhance photovoltaic performance. Theoretical calculations and experimental results reveal that NHMS effectively passivates bulk and interfacial defects by coordinating with uncoordinated lead ions (Pb²⁺) and forming hydrogen bonds with iodide or formamidinium ions (I⁻/FA⁺). This dual-site passivation effect effectively reduces trap-assisted recombination. Moreover, the incorporation of NHMS promotes the oriented crystallization of the perovskite, leading to a notable increase in grain size. Consequently, NHMS-treated PSCs achieved a champion power conversion efficiency (PCE) of 26.51% (certified 26.35%), while centimeter-sized PSCs exhibit an impressive PCE of 25.15%. Furthermore, the NHMS-treated device exhibits a remarkable stability for maintaining 95% of its initial efficiency after 1100 h of maximum power point voltage tracking. This work provides comprehensive insights into the application of dual-site passivation to achieve high-performance PSCs.