Yongbin Jin, Boxin Jiao, Jin Huang, Huiping Feng, Chengtang Den, Ningyu Ren, Li M, Ruihao Su, Di Qian, 丁墨翰, Jérôme Gabathuler, Yiran Ye, Wenbao Yang, Ruizhi Wang, Haifeng Shi, Delia A. Haynes, Liqiang Xie, Zhanhua Wei, Chenyi Yi
ABSTRACT Flexible perovskite/silicon tandem solar cells (FTSCs) represent a frontier for high‐power‐density, conformable electronics, yet their commercial viability is hindered by the dual challenges of interfacial carrier recombination and mechanical delamination at the perovskite/C 60 interface. Here, we demonstrate a bimolecular piperazine‐derived interface engineering strategy that simultaneously optimizes interfacial photophysics and structural integrity. By applying a synergistic combination of piperazine dihydrochloride (PDCl) and 1‐(4‐chlorophenyl) piperazine hydrochloride ( p ‐ClPh‐PCl), we achieve complementary field‐effect passivation and in situ formation of a stabilizing low‐dimensional template. While PDCl effectively suppresses interfacial trap states and modulates band alignment for accelerated electron extraction, the p ‐ClPh‐PCl facilitates uniform C 60 growth, preventing fullerene aggregation and reinforcing interfacial adhesion. This unified molecular design enables us to reach a power conversion efficiency of 31.51% (1 cm 2 ) and a 30.31% for large‐area (17.64 cm 2 ) FTSCs, surpassing 30% PCE for the first time in FTSCs exceeding 10 cm 2 in device area. Furthermore, these devices exhibit exceptional durability, retaining 95% of their initial efficiency after 20,000 bending cycles and 650 h of continuous illumination.