Enhancing Stability of Inverted Perovskite Solar Cells via Buried Interface Modification Using In‐Situ Crosslinked Thiol‐Ene Polymer

In inverted (p‐i‐n) perovskite solar cells (PSCs), the buried interface of perovskite has been a thorny issue due to the difficulty of forming a good interfacial contact between hole‐transporting layer (HTL) and perovskite. Here, a cross‐linkable interfacial layer is induced in p‐i‐n PSCs to modify the buried interface of perovskite. The cross‐linkable layer is copolymerized with pentaerythritol tetrakis(3‐mercaptopropionate) (PETMP) and triallyl isocyanato (TAIC) to form cross‐linked‐PETMP‐TAIC. After thermal treatment at 100 °C, the vinyl group in TAIC can react with the thiol group in PETMP to form a cross‐linked network. It is found that the cross‐linked interfacial layer could not only improve the energy level arrangement between HTL and perovskite, thus promoting the extraction of hole but also significantly enhance the crystalline quality of buried interface of perovskite and inhibit the perovskite phase transition during aging. Devices employing this cross‐linkable interfacial layer exhibited a power conversion efficiency of 22.20%, maintaining 86% of its initial efficiency after thermal aging at 85 °C for 500 h.