Ionization‐State‐Directed Sulfonate‐Rich Buried Interfaces Enable Durable High‐Efficiency Perovskite Solar Cells and Modules

Proton‐triggered degradation at the buried interface severely undermines the operational stability of inverted perovskite solar cells (PSCs). To address this issue, this work develops an ionization‐state‐directed sulfonate approach using sodium 2,2'‐disulfanediyldiethanesulfonate (DDANA). The pre‐deprotonated sulfonate terminals grant DDANA strong coordination with lead sites and drive its spontaneous aggregation at the perovskite and self‐assembled monolayer interface, forming robust multisite binding with the perovskite lattice. The enriched sulfonate groups build favorable interfacial dipoles to optimize energy level alignment and facilitate hole transport. The immobilized sulfonate groups act as conjugate‐based sites to competitively capture protons, while the disulfide skeleton enables reversible iodine‐redox to scavenge corrosive iodine species under operational stress. Dissociated sodium (Na + ) ions embed into lattice interstices and release residual tensile strain. As a result, DDANA‐modified inverted PSCs achieve a champion efficiency of 27.38% (certified 27.13%). The strategy extends seamlessly to flexible devices and rigid large‐area modules, delivering efficiencies of 25.88% and 23.33%, respectively. Moreover, the DDANA‐modified devices retain 98.9% of their initial efficiency after 1000 h of maximum power point tracking and 97.4% after cycling diurnals. This work establishes sulfonate ionization‐state engineering as a versatile molecular design platform for constructing chemically robust buried interfaces toward efficient, stable, and scalable perovskite photovoltaics.