Knoevenagel Condensation Enables a High‐Dipole Interfacial Molecule for Efficient Wide‐Bandgap Perovskite and Tandem Photovoltaics

⁺ group forms stable bonds with perovskite lattice, modulating crystal growth kinetics, and improving interfacial contact. The Br atom ensures intrinsic compatibility with bromine-rich wide-bandgap perovskites. Notably, the rigid, planar structure of BCPA facilitates ordered SAM packing via π-π interactions, enhancing interfacial charge extraction. BCPA-modified hole transport layers significantly improve the buried perovskite/substrate interface by reducing trap densities, enhancing crystallinity, and aligning energy levels. As a result, modified WBG PSCs realized a champion efficiency of 19.08% with reinforced durability. Furthermore, when applied in perovskite-organic tandem configurations, the devices reach a remarkable PCE of 26.10%, highlighting the importance of interfacial modifier for next-generation high-efficiency photovoltaics.