Enhancing the Stability of Perovskite Solar Cells Through an Iodine Confinement Strategy in Covalent Organic Frameworks

Abstract Perovskite solar cells (PSCs) have shown high power conversion efficiency in solar‐to‐electricity conversion applications. However, the commercialization of this emerging technology is limited due to its low stability under realistic operating conditions. A major reason for this degradation is the formation and escape of iodine species upon exposure to light, polarization and thermal stress. Here, a new method is proposed to confine iodine species in the perovskite layer using a multifunctional nitrogen‐rich covalent organic framework (TAPT‐BP‐COF). The ordered pore structure and surface binding groups of TAPT‐BP‐COF not only facilitate the formation of charge transfer complexes with iodine molecules, but also enable multisite chelation with undercoordinated lead ions, thereby improving the quality of the perovskite film. This iodine confinement strategy enables the resulting Cs 0.05 MA 0.05 FA 0.9 PbI 3 PSC devices (n‐i‐p) to achieve an outstanding power conversion efficiency of 25.58% (0.06 cm −2 ) under one sun illumination. The unencapsulated devices maintained over 96% of their initial efficiency after continuous maximum power point tracking for 1200 h in an N 2 atmosphere. Importantly, the PSCs with TAPT‐BP‐COF demonstrated excellent stability even under the high temperature of the ISOS‐L‐2 protocol, maintaining over 90% of peak efficiency at 85 °C for 800 h.