Full‐Cycle Humidity‐Tolerant Perovskite Solar Cells Enabled by Air‐Processed In Situ Shielding via Synergistic Dynamic Bonds and Self‐Crosslinking

Perovskite solar cells (PSCs) emerge as a research hotspot in photovoltaics due to their exceptional power conversion efficiency. However, their fabrication processes and operational stability remain vulnerable to moisture interference. Enhancing humidity tolerance during both manufacturing and service phases thus constitutes a critical pathway for accelerating perovskite photovoltaic commercialization. Herein, a thermal self‐crosslinking monomer (TMTBAEM) featuring dynamic urea bonds are designed to reinforce perovskite moisture resistance throughout the fabrication‐operation lifecycle. The dynamic urea bonds chemically intercept molecular water, preventing water‐induced perovskite damage at the molecular level. Simultaneously, TMTBAEM interacts with lead iodide to enhance perovskite crystallinity. During thermal annealing, TMTBAEM forms a cross‐linked network that encapsulates perovskite crystals at the grain level. This integration enables exceptional fabrication humidity tolerance, achieving 25.57% efficiency at 40% RH. Remarkably, grain‐encapsulated devices maintain >80% initial efficiency after 1,500+ h under high humidity (60 ± 5% RH). This thermally cross‐linked dynamic bonding strategy establishes a novel approach to boost water resistance throughout perovskite devices' entire lifecycle, opening new perspectives for moisture‐resistant perovskite optoelectronics.