Triple‐Functional Hydrazide‐Based Modifier for Self‐Assembled Monolayers/Perovskite to Obtain 26.29%‐Efficiency Inverted MA‐Free Perovskite Solar Cells

Abstract Inverted perovskite solar cells (PSCs) face challenges in hole‐transport layer (HTL) uniformity and buried interface defect passivation. To address these issues, we introduce 4‐(methylthio)benzhydrazide (MTBH) as a triple‐functional modifier for self‐assembled monolayers (SAMs)/perovskite to enhance the performance of inverted PSCs. MTBH simultaneously optimizes the [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) SAMs and passivates perovskite defects through ternary synergistic interactions: (1) P═O→S‐C coordination between Me‐4PACz and MTBH improves SAMs ordering and energy‐level alignment; (2) N─H⋯I − hydrogen bonding passivates iodine vacancies; (3) C═O→Pb 2+ coordination repairs undercoordinated lead defects. These interactions regulate perovskite crystallization kinetics, inducing a “fast nucleation‐slow growth” mode that yields high‐quality films with reduced residual stress (18.0 MPa versus Control's 60.1 MPa) and suppressed grain‐boundary defects. Consequently, MTBH‐incorporated devices achieve a champion power conversion efficiency (PCE) of 26.29% (versus 23.62% for control) with a high fill factor (FF: 84.94%) and open‐circuit voltage ( V OC : 1.19 V). The devices also exhibit exceptional stability, retaining 93.76% PCE after 2000 h in ambient air and 98.0% after 470 h of maximum power point tracking.