Electrostatic Cation Intercalation Into Polymeric Self‐Assembled Monolayers Enables Ambient‐Air Fabrication of 32.73% Efficient Monolithic Perovskite/Silicon Tandem Solar Cells

ABSTRACT Polymeric self‐assembled monolayers (SAMs) enable stable, efficient, and scalable perovskite/silicon tandem solar cells (TSCs) based on silicon heterojunction (HJT) bottom cells. However, severe steric hindrance within the polymer matrix disrupts the directional anchoring of phosphonate groups, thereby limiting macroscopic work‐function regulation and sustaining a persistent hole‐extraction barrier. Herein, we report a targeted molecular reconstruction of the buried interface via the electrostatic intercalation of phenethylammonium iodide (PEAI). Templated by the polymer backbone, the intercalated PEA + cations adopt a highly directional vertical arrangement. This oriented molecular scaffold provides a strong intrinsic dipole while driving the electronegative iodide (I − ) counterions to enrich at the uppermost interface. This synergistic spatial decoupling maximizes the net upward dipole, triggering a favorable energy level realignment that effectively overcomes the hole extraction barrier. Concurrently, the halide‐enriched SAM dictates crystallization kinetics during ambient‐air slot‐die coating, inducing rapid “burst nucleation” to minimize solvate intermediates and suppress basal voids. Consequently, our 1 cm 2 TSC achieves an independently certified power conversion efficiency (PCE) of 32.73%. Benefiting from monolithic crystallographic integrity, the unencapsulated device maintains an enhanced T 80 lifetime of 2182 h under continuous maximum power point tracking.