Ultrasound‐Assisted Zwitterion Grafting on NiO x for Suppressing Self‐Assembled Monolayer Migration in Perovskite Solar Cells

Self‐assembled monolayers (SAMs) are widely used as hole‐selective materials in inverted perovskite solar cells (PSCs), yet their performance and stability are often limited by poor molecular ordering and interfacial incompatibility. Here, we present a novel ultrasonic chemical strategy to functionalize NiO x nanoparticles via anchoring the piperazine‐1,4‐bisethanesulfonic acid (PIPES) zwitterionic molecule. Ultrasonic cavitation generates hydroxyl radicals that oxidize Ni 2 + to Ni 3 + , enhancing the electrical conductivity and hole mobility of NiO x . The exposed sulfonate groups of PIPES further promote the uniform assembly and hydrogen bonding anchoring of the subsequent SAM layer [(4‐(9'‐phenyl‐9H,9'H‐[3,3'‐bicarbazole]‐9‐yl)butyl)phosphonic acid, 4PABCz]. This integrated NiO x +PIPES/4PABCz hole transport layer fosters stronger dipole formation and interfacial polarization, facilitating charge separation and transport. Consequently, the optimized devices achieve a champion power conversion efficiency (PCE) of 27.03% (with a certified steady‐state efficiency of 26.47%). Remarkably, the devices exhibit exceptional operational and thermal stability, retaining 88.2% of their initial PCE after 1000 h of continuous illumination at 85°C and 91.0% after 1200 h of thermal aging at 85°C. This work introduces a robust and effective NiO x modification strategy, providing profound insights into interfacial design for high‐performance, stable inverted PSCs.