Buried-interface homogenization by asymmetric polymeric self-assembled layers powers efficient, durable flexible perovskite photovoltaics

Flexible perovskite solar cells and modules are limited by buried-interface nonuniformity and the thickness-sensitive, aggregation-prone nature of conventional small-molecule self-assembled monolayers, which create local recombination hot spots and crack-initiated degradation during large-area coating and bending. Here we introduce asymmetric polymeric self-assembled layers based on poly(4-(3-phenyl-9H-carbazol-9-yl)butyl phosphate) (Poly-3Ph-4PACz), a polycarbazole phosphonic acid featuring rigid phenyl-carbazole units and multiple anchoring sites. The polymeric architecture yields a dense, highly wetting and electrically homogeneous hole-selective contact with enhanced interfacial dipole and strong perovskite binding, enabling uniform crystallization, reduced non-radiative losses and effective stress buffering. Flexible devices reach 26.13% champion power conversion efficiency, while 57.6 cm 2 flexible modules deliver 22.22%. Encapsulated modules retain 97.23% after 3000 bending cycles and show damp-heat resilience with T 95  > 1000 h at 85 °C/85% RH. Beyond flexibility, Poly-3Ph-4PACz enables 27.18% rigid inverted perovskite solar cells (certified mean steady-state 27.12%) and a certified 32.95% perovskite/Si tandem efficiency. These results establish polymeric self-assembly as a scalable route to high-efficiency, durable flexible photovoltaics.