Mechanochemically Reinforced Dual‐Dynamic Covalent Seeding Enables High‐Performance and Operationally Stable Perovskite Solar Cells

The long-term instability of perovskite solar cells (PSCs), primarily governed by defect-mediated ion migration, poses a critical barrier to their commercialization. Herein, we introduce a synergistic dual-dynamic scaffold (DDS) strategy, constructed in situ via orthogonal Diels-Alder and oxime-carbamate reactions within the perovskite precursor. This intelligently designed network functions as a molecular template for heterogeneous nucleation, directing the formation of dense, large-grained, and preferentially oriented films. Concurrently, the DDS consolidates into an interpenetrating covalent mesh at grain boundaries (GBs), delivering multi-modal passivation through Lewis-base coordination and hydrogen bonding, inducing a benign compressive strain, and serving as a robust physicochemical barrier against ion and moisture ingress. These concerted actions effectively minimize interfacial losses, mitigate energetic disorder, and suppress trap-assisted recombination. Remarkably, the covalently anchored network underpins exceptional operational stability under thermal, environmental, and electrical stress. Consequently, this integrated strategy yields a champion power conversion efficiency (PCE) of 26.95% (certified 26.69%), along with excellent long-term stability, retaining 97.8% of its initial efficiency after 1000 h of continuous operation under the ISOS-L-2I protocol, underscoring the transformative potential of in situ dual-dynamic covalent bonding for high-performance and operationally stable photovoltaics.