In-Situ Cross-Linked Multianchoring Fullerene Interlayer for Tin-Based Perovskite Solar Cells

Interface defects and poor adhesion at the perovskite/electron transporting layers (ETL) interfaces severely limit the performance of tin-based perovskite solar cells (TPSCs). However, conventional ammonium salt interlayers require alcoholic solvents that damage tin perovskites. Here, we designed a series of cross-linkable, multianchoring fullerene derivatives (FB4–FB6) for interfaces modifications. These molecules can be processed in nondisruptive solvents and undergo in situ cross-linking to form robust, solvent-resistant networks (CFB4–CFB6), which remain intact during subsequent device fabrication. The multiple anchoring groups establish strong chemical interactions with the perovskite surface, effectively passivating interfacial defects, suppressing nonradiative recombination, and facilitating charge extraction. As a result, CFB5-based devices achieve a champion efficiency of 15.69%, attributed to optimized interfacial interactions, significantly surpassing the control device (13.13%). Moreover, the CFB5-modified devices exhibit remarkable operational stability, retaining over 95% of their initial efficiency after 800 h under the ISOS-L-1 protocol, along with improved thermal and ambient stability.