Modulating Adsorption Orientation of Multi‐Site Ligand Enables Perovskite/Silicon Tandem Solar Cells with Voltage Exceeding 2 V

Abstract Rational molecular design at the perovskite/charge transport layer interface offers an effective approach for suppressing non‐radiative recombination in perovskite/silicon tandem solar cells (TSC). However, the design involves a tradeoff between defect passivation and charge transport, as multi‐site passivation molecules always introduce a resistive barrier. Herein, we employ a triple‐site planar molecule, 3‐amino‐4‐chlorobenzenesulfonic acid (3A4Cl‐BZS), as a multifunctional modifier that can concurrently suppress non‐radiative recombination and enhance electron transfer. Specifically, functionalizing the benzene ring with sulfonic acid (‐SO 3 H) and amino (‐NH 2 ) groups enhances the passivation of undercoordinated Pb 2+ and I − defects via coordination and hydrogen bonding, respectively, and incorporating a chlorine group promotes the parallel adsorption on the perovskite surface. The parallel configuration, rather than vertical orientation, minimizes the distance between the active site and the perovskite defects, significantly boosting passivation efficacy and mitigating the resistive barrier. Consequently, 1.67 eV bandgap perovskite solar cells achieve a power conversion efficiency (PCE) of 23.55%. Furthermore, integrating this cell into perovskite/silicon TSC yields a high voltage of over 2 volts and a PCE of 31.42% adopting a planar silicon sub‐cell. Remarkably, encapsulated tandem devices retain over 80% of their initial PCE after 1960 h of maximum power point tracking under 1‐sun illumination at 25 °C.