Hydroxyl Interfacial Engineering for Self‐Assemble Monolayers Anchoring on NiO x Enables Efficient and Stable Perovskite Solar Cells

ABSTRACT The performance of inverted perovskite solar cells (PSCs) is critically constrained by interfacial losses arising from the insufficient coverage and weak adhesion of self‐assembled monolayers (SAM). Herein, we report a SAM regulation strategy by mixing hydroxylated V 2 CT x MXene (V 2 C‐OH) with nickel oxide (NiO x ), which can provide abundant hydroxyl sites for SAM anchoring, thereby forming a uniform and dense SAM layer. First‐principles calculations further reveal that the binding energy between SAM and hydroxyl groups on V 2 C‐OH is stronger than that on pristine NiO x , explaining the enhanced thermal stability of SAM on the hybrid substrate. Meanwhile, the highly ordered and tightly packed SAM layer promotes vertical growth and 001‐preferred orientation of perovskite grains. Therefore, the introduction of V 2 C‐OH enables a top‐down modulation of the NiO x , SAM, and perovskite layers, improving their morphology and interfacial properties. The resulting PSCs achieve a champion power conversion efficiency of 26.6% (certified at 26.2%) for a 0.0524 cm 2 device and 24.7% for a 1 cm 2 device, along with outstanding long‐term operational stability.