Triisocyanate Derived Interlayer and High‐Melting‐Point Doping Promoter Boost Operational Stability of Perovskite Solar Cells

Abstract Formamidinium lead triiodide serves as the optimal light‐absorbing layer in single‐junction perovskite solar cells. However, achieving operational stability of high‐efficiency n‐i‐p type devices at elevated temperatures remains challenging. In this work, we implemented effective surface modifications on microcrystalline perovskite films. This involved the nucleophilic addition of formamidinium cations and coordination of residual PbI 2 with triphenylmethane triisocyanate as well as subsequent polymerization. The in situ growth of a cross‐linking network chemically anchored on the perovskite film in this approach effectively reduced trap densities, favorably altered surface work function, suppressing interface charge recombination and thus enhancing cell efficiency. Coupled with a high‐melting‐point air‐doping promoter, we fabricated n‐i‐p type perovskite solar cells surpassing 25 % efficiency, demonstrating excellent operational stability at 65 °C.