Bifacially Reinforced Self‐Assembled Monolayer Interfaces for Minimized Recombination Loss and Enhanced Stability in Perovskite/Silicon Tandem Solar Cells

Abstract Perovskite/silicon tandem solar cells have shown higher power conversion efficiencies (PCEs) than single‐junction cells. However, their record PCE still falls short of the theoretical maximum, and their stability is significantly lower than that of crystalline silicon solar cells. These challenges stem from the substantial losses in open‐circuit voltage ( V OC ) and the instability of wide‐bandgap perovskite devices, which are mainly caused by nonradiative recombination and degradation at the heterojunction interfaces, respectively. Specifically, the weak adhesion between indium tin oxide (ITO) and self‐assembled monolayers (SAMs), along with inadequate interactions between the SAMs and the perovskite, contributes to this instability. Herein, a novel SAM material, 4‐(11H‐benzo[a]carbazol‐11‐yl)butyl (4‐PhCz), has been developed to bifacially reinforce interfaces by enhancing SAM coverage on ITO and strengthening the interactions between SAM and perovskites. The resulting 1.67 eV perovskite solar cell (PSCs) achieves a V OC of 1.273 V with a low voltage loss of 0.397 V relative to the bandgap and a PCE of 22.53%. The 4‐PhCz‐based perovskite/silicon tandem cell achieves a V OC of 1.96 V and a PCE of 31.26%, retaining 92% of its initial efficiency after 1000 h of maximum power point tracking (MPPT) under 1‐sun illumination in a nitrogen atmosphere at 25 °C.