Tuning NiO _x /Perovskite Heterointerface via Synergistic Molecular Design Strategy of Carbazole Phosphonic Acid for High‐Performance Inverted Perovskite Solar Cells

Abstract Mitigating non‐radiative recombination at the NiO _x /perovskite heterointerface is critical for boosting the device performance of inverted perovskite solar cells (IPSCs). Although carbazole phosphonic acid molecules (CPAMs) are widely utilized to modify the heterointerface for enhancing IPSCs performance, they face a fundamental trade‐off between hole extraction capability and surface wettability. Here, a synergistic molecular design of CPAM is reported to fine‐tune the NiO _x /perovskite heterointerface. The synthesized [4‐(3,6‐methoxyphenyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (MeOPh‐4PACz) demonstrates a superior wettability compared to the commercial CPAMs, along with a higher dipole moment and exceptional hole extraction capability. These features collectively contribute to favorable band alignment between NiO _x and perovskite and suppress interfacial charge recombination. Furthermore, MeOPh‐4PACz promotes perovskite crystal growth, enhancing the film quality and optoelectronic properties of the perovskite active layer, which results in a remarkable power conversion efficiency of 26.3% (25.8% certified) for the champion device. Under accelerated aging conditions, the device exhibits a T ₉₅ lifetime of 1052 h based on the ISOS‐D‐3 protocol. This study underscores the effectiveness of molecular design strategy for fine‐tuning heterointerface to enable efficient and stable IPSCs.