Locking the Morphology: A Photo-Cross-Linking Strategy for Thermally and Mechanically Robust Organic Solar Cells

Despite remarkable advances in power conversion efficiency (>20%), the operational stability of organic solar cells (OSCs) remains a primary obstacle to their commercialization. We report a universal photo-cross-linking strategy using an azide-functionalized cross-linker, AZSIL. Upon mild UV irradiation, it selectively targets alkyl side chains to form a robust network within the bulk-heterojunction, effectively “locking” the morphology without damaging the optoelectronic cores. This approach fundamentally suppresses molecular diffusion, as evidenced by AFM-IR and nanoindentation, which confirm arrested phase separation and enhanced mechanical robustness. In the PM6:L8-BO system, devices with only 0.5% AZSIL retain 85.1% of their initial efficiency after 1200 h at 85 °C. The strategy demonstrates remarkable universality, offering a simple and scalable path to high-performance, durable OSCs.