A dual-functional surface passivator enables ETL-free perovskite solar cells to exhibit 23.71% efficiency.

ETL-free perovskite solar cells (PSCs) draw attention due to their simple structure and low cost, yet suffer from severe interfacial-defect-induced performance and stability degradation. Herein, 2-aminobenzimidazole (2-ABD) is employed as a bifunctional perovskite-surface passivator. It passivates lead defects via Pb-N coordination and immobilizes iodide ions through N-H⋯I- hydrogen-bond networks, synergistically optimizing interfacial energetics and carrier transport. The modified device delivers a champion efficiency of 23.71% and maintains 94.53% of its initial performance after 1200 h of MPP tracking. This work provides a new strategy for interfacial passivation of ETL-free perovskite photovoltaics.