Flexible Perovskite/Silicon Tandem Solar Cells Exceeding 30% Efficiency at Scale

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.