A dipolar bidentate molecule for efficient and stable all-inorganic perovskite solar cells

All-inorganic perovskite solar cells (PSCs), typically composed of cesium-lead halides, have emerged as promising next‑generation photovoltaics owing to their superior thermal and environmental stability. Yet, interfacial defects in the titanium dioxide (TiO ₂ ) electron transport layer severely limit charge extraction and operational durability. Conventional self‑assembled monolayers (SAMs) can mitigate such defects but offer limited control over interfacial energetics. Herein, we present a series of benzoic acid-derived SAMs with bidentate functional groups and gradient dipole moments that enable simultaneous chemical passivation and electronic coupling at the TiO ₂ /perovskite interface. Systematic molecular tuning reveals a transition from simple anchoring to synergistic dipole-passivation interactions that govern interfacial energetics. Notably, 3-amino-4-methoxybenzoic acid (AMBA) combines –COOH group for coordinating oxygen vacancy in TiO ₂ , –NH ₂ group for passivating undercoordinated Pb ²⁺ sites in perovskites, and –OCH ₃ group that enhances molecular dipole polarization. This configuration establishes a polarized interfacial field that aligns the energy levels, accelerates electron extraction, and directs perovskite crystallization toward large, low‑defect grains. As a result, AMBA‑modified PSCs achieve a power conversion efficiency of 21.4% (vs. 18.4% for control) and maintain 93.8% of their initial efficiency under UVC (254 nm) irradiation (vs. 67.5% for control)—representing the highest photostability reported for all-inorganic PSCs to date. These findings underscore the power of dipolar bidentate SAM engineering in tailoring interfacial energetics for efficient and durable perovskite photovoltaics.