A cross-linked molecular contact for stable operation of perovskite/silicon tandem solar cells

Monolithic perovskite/silicon tandem solar cells surpass the power-conversion efficiency limits of single-junction solar cells but face challenges in operational stability. We identified fill factor diminution as a key performance-loss mode in the state-of-the-art tandem architecture. We reveal that widely used hole-selective molecular contacts, which enhance tandem cell performance, undergo thermal degradation that undermines charge transport. At elevated temperatures, the resistance of conventional monomeric contacts increases by about sixfold because of thermal-induced disorder. To stabilize interfacial structures, we introduce in situ synthesized cross-linked molecular contacts based on Schiff base linkages. One-square-centimeter perovskite/silicon tandem solar cells achieved power-conversion efficiencies exceeding 34% (33.61% certified), and three independent devices retained 96.2 ± 1.7% of their initial performance after about 1200-hour maximum power point operation under AM1.5G illumination at 65°C.