Bisphosphonate‐Embedded a π‐Conjugated Passivator Enable Efficient and Stable n‐i‐p Perovskite Solar Cells with Low‐Polarity Solvent Processing

Abstract Interface passivators play a critical role in improving the efficiency of perovskite solar cells (PSCs). However, the conventional passivators often require processing in high‐polarity solvents that can cause additional surface defects on the perovskite film, thereby reducing the efficiency and stability of n‐i‐p PSCs. Herein, a bisphosphate molecule (named DCTP) is designed and synthesized to simultaneously address solvent compatibility, defect passivation, and hole extraction. DCTP has good solubility in low‐polarity solvents such as toluene, chlorobenzene, and chloroform without damaging the perovskite surface. The chlorobenzene‐processed DCTP interlayer can sufficiently passivate the defects on the perovskite surface and improve the energy level arrangement at the perovskite/hole transporting layer interface. Meanwhile, the DCTP layer effectively inhibits interlayer diffusion of formamidine (FA + ), iodide (I − ), and lithium (Li + ) and ions under thermal stress. As a result, the DCTP‐controlled device produces a champion power conversion efficiency (PCE) of 26.07% with excellent reproducibility, compared to 24.28% for the reference device. More importantly, the operational stability of the device is significantly improved. The DCTP‐treated device retains 90.1% of its initial PCE after 900 h of maximum power point tracking (MPPT) at 65 °C under the ISOS‐L‐2I protocol.