Synergistic interfacial molecular design for high‐performance and eco‐friendly perovskite solar cells

The commercialization of perovskite solar cells (PSCs) is significantly hindered by intrinsic defects in solution‐processed polycrystalline films, which promote nonradiative recombination and accelerate material degradation, coupled with environmental issues arising from the potential leaching of toxic lead (Pb) species upon device failure. This work presents a multifunctional molecular interfacial engineering strategy by incorporating 4‐chlorophenyl dichlorophosphate (4‐CP) to optimize the SnO 2 electron transport layer/perovskite interface. The triple functionality of 4‐CP enables synergistic defect passivation, crystallization modulation, and Pb immobilization. Owing to electronegativity differences, the phosphate groups in 4‐CP effectively passivate SnO 2 surface oxygen vacancies via strong coordination, while the expelled hydrophobic phenyl rings and C–Cl bonds regulate perovskite grain growth and anchor Pb 2 + . The optimized device achieves a power conversion efficiency (PCE) of 25.25% with increased stability. Remarkably, 4‐CP modification reduces Pb leakage by 89%; the Pb 2+ leaching concentration from 4‐CP‐modified devices lower than 30 ppb which is far below the safety threshold (50 ppb) of China's Environmental Quality Standards for Surface Water (GB 3838–2002). Moreover, the 4‐CP‐modified devices retained 92% of its initial PCE after rigorous aging (25 °C, 85% RH, 1000 h), demonstrating exceptional operational stability. This multifunctional interface engineering approach provides a groundbreaking pathway toward high‐performance, eco‐conscious PSCs.