Omnibearing Molecular‐Locking of Perovskite Lattice Enables High‐Performance Perovskite Solar Cells with Efficiency over 26%

Abstract Solution‐processed polycrystalline perovskite films are favorable for low‐cost manufacturing of perovskite solar cells (PSCs). However, multiple‐energy‐level trap states in perovskites can trigger ionic migration and degrade device efficiency. Herein, a multidentate‐anchoring strategy by introducing 6‐thioguanine as an additive is employed to enable omnibearing molecular locking of the perovskite lattice. Theoretical calculations indicate that the molecular locking can increase the formation energy of multiple‐energy‐level defects including I vacancy, Pb vacancy, Pb interstitial, and Pb‐I antisite, which can enhance the stability of PSCs. The additive can not only retard crystal growth that initiates the construction of high‐crystallinity film with fewer trap states, but also up‐shift energy level of perovskite that favors interfacial hole extraction. Owing to these merits, present work achieves a formamidinium lead iodide PSC that delivers a champion efficiency of 26.02%, setting a new benchmark for TiO 2 ‐based planar PSCs, along with pronounced operational stability with almost no efficiency degradation over 400 h. This work paves a way for exploring constructive molecular configurations to simultaneously eliminate multiple‐energy‐level defects in perovskite for advanced photovoltaics.