Xi Wu, Xin Li, Haitao Zhang, Yu Liu, Yige Peng, Y. Y. Ji, Yong Zhang, Z Feng, Chenghao Ge, Yanbo Wang, Yansen Guo, Hailong Huang, Shuilong Kang, Yuan Fang, Jing Chen, Weichang Zhou, Dongsheng Tang, Yu Zeng, Chaopeng Huang, Zhongyao Jiang, Haifeng Gao, Qiang Zhang, Jingsong Sun, Youyong Li, Xiao‐Hong Zhang, Jun Peng
ABSTRACT The rapid development of self‐assembled monolayers (SAMs) has been instrumental in advancing the power conversion efficiency (PCE) of inverted perovskite solar cells (PSCs) to exceed 26%. However, benchmark SAMs are limited by stochastic assembly kinetics and weak interfacial coupling with the perovskite, which induce severe interfacial recombination and compromise device stability. Here, we developed an amino acid hydrochloride (AAH)‐mediated SAM to construct high‐performance PSCs. By systematically modulating the AAH alkyl spacer length, we elucidate an optimal steric profile that balances thermodynamic anchoring with kinetic intermolecular organization. This optimized AAH‐mediated SAM exhibits enhanced coverage, uniformity, and molecular packing density, stabilizing the interface via reduced defect density and refined energy level alignment. Moreover, the AAH terminal ammonium (–NH 3 + Cl − ) moieties establish a chemical bridge with the perovskite, effectively passivating interfacial defects and promoting stress‐free crystallization. Consequently, the devices based on AAH‐mediated SAMs delivered a champion PCE of 26.87% (certified at 26.33%) on a 0.058 cm 2 area and 25.90% on a 1‐cm 2 area. Encapsulated device exhibited excellent operational stability, retaining over 97.3% of its initial efficiency after 1100 h of continuous operation at the maximum power point in air.