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

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/C₆₀ 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 C₆₀ growth, preventing fullerene aggregation and reinforcing interfacial adhesion. This unified molecular design enables us to reach a power conversion efficiency of 31.51% (1 cm²) and a 30.31% for large-area (17.64 cm²) FTSCs, surpassing 30% PCE for the first time in FTSCs exceeding 10 cm² 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.