Molecular Doping of Self‐Assembled Monolayers for Interface Engineering in Inverted Perovskite Solar Cells and Large‐area Bifacial Modules: Enhancing Uniformity, Crystallization, and Stability

Abstract Interface engineering remains a critical bottleneck in advancing the performance and operational stability of inverted perovskite solar cells (PSCs). Here, a molecular doping strategy is presented by incorporating methyl 3‐chlorosulfonyl‐2‐thiophenecarboxylate (MCC) into 4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butylphosphonic acid (Me‐4PACz) self‐assembled monolayers (SAMs). This approach significantly enhances molecular packing, film uniformity, and interfacial passivation. The multifunctional MCC molecule, with its π‐conjugated thiophene, sulfonyl chloride, and ester groups, enables dipolar alignment, chemical coordination with Pb 2+ , and improved wettability—collectively promoting superior perovskite crystallization and suppressed non‐radiative recombination. Devices based on MCC‐doped SAMs achieve outstanding power conversion efficiencies of 26.78% (certified 300s steady‐state 26.65%) and 23.78% for PSCs based on 1.53 and 1.67 eV perovskite absorbers, respectively, with remarkable operational stability exceeding 2000 h. Notably, the strategy is successfully extended to large‐area, bifacial semi‐transparent PSC modules, demonstrating the double‐sided efficiencies of 15.51% and 14.64%, respectively, which exhibit strong potential for application in building‐integrated photovoltaics (BIPV) in the future. This work establishes a scalable and generalizable strategy for buried interface regulation, offering a compelling pathway toward highly efficient, stable, and manufacturable inverted PSCs.