Internal Capsulation Via Self‐Cross‐linking and π‐Effects Achieves Highly Stable Perovskite Solar Cells

Abstract Pursuing high stability becomes the core challenge in realizing the widespread application of perovskite solar cells (PerSCs). Here, a practical internal‐capsulation strategy is proposed by introducing cross‐linkable methacrylate analogs upon the perovskite layer, hindering ion migration and preventing lead leakage to achieve stable PerSCs. Butyl methacrylate (UMA) and benzyl methacrylate (BMA) can chemically interact with the perovskite layer, especially for the BMA dimer with significant π‐interactions among the hanging benzene rings. Such configuration facilitated more compact coordination, thereby restoring the Fermi level of perovskite to a defect‐free state and reducing carrier recombination losses. Moreover, by integrating the self‐cross‐linking and intermolecular π‐effect, the application of BMA upgraded the internal capsulation from linear protection to a compact mesh‐like scale. Consequently, the application of BMA not only boosted the efficiency to 25.31% but also greatly enhanced the stability of the perovskite layer, especially for water resistance and preventing lead linkage. The internal capsulation strategy upgrading from linear to mesh‐like marked an innovative direction in protecting the perovskite layer, paving the way for more sustainable PerSCs in further application.