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

ABSTRACT 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.