Decoupling Photoinduced Lattice Evolution via Grain Spatial Isolation for Perovskite Solar Cells

The long-term operational stability of perovskite solar cells (PSCs) remains a major challenge, particularly due to photomechanical instability caused by light-induced lattice dynamics. In this study, an in situ polymerization strategy is developed using the monomer 2-acrylamido-2-methylpropanesulfonate (AMPS), which polymerizes during the annealing process of perovskite films to form a soft, cross-linked polymer (P-AMPS). The polymer acts as a grain boundary spacer, enabling physical spatial isolation between perovskite grains. This structure effectively mitigates light-induced lattice expansion and stress/strain accumulation, while suppressing ion migration and strain-induced defect evolution. Systematic experimental and theoretical investigations demonstrate that P-AMPS enhances film quality and lattice integrity, while significantly improving the photomechanical stability of perovskite film. Methylamine-free PSC fabricated using this approach achieved a power conversion efficiency of 25.78%. Following the ISOS-L-1 protocol, the P-AMPS-based device retained 83.52% of its initial maximum power point efficiency after 1500 h of continuous illumination. The grain spatial isolation strategy based on in situ polymerization offers a novel design concept for the commercialization of PSCs.