Chlorofullerene C60Cl6 Enables Efficient and Stable Tin‐Based Perovskite Solar Cells

Tin‐based perovskite solar cells (TPSCs) have received great attention due to their eco‐friendly properties and high theoretical efficiencies. However, the fast crystallization feature of tin‐based perovskites leads to poor film quality and limits the corresponding device performance. Herein, a chlorofullerene, C 60 Cl 6 , with six chlorine attached to the C 60 cage, is applied to modulate the crystallization process and passivate grain boundary defects of the perovskite film. The chemical interactions between C 60 Cl 6 and perovskite components retard the transforming process of precursors to perovskite crystals and obtain a high‐quality tin‐based perovskite film. It is also revealed that the C 60 Cl 6 located at the surfaces and grain boundaries can not only passivate the defects but also offer a role in suturing grain boundaries to suppress the detrimental effects of water and oxygen on perovskite films, especially the oxidation of Sn 2+ to Sn 4+ . As a result, the C 60 Cl 6 ‐based device yields a remarkably improved device efficiency from 10.03% to 13.30% with enhanced stability. This work provides a new strategy to regulate the film quality and stability of TPSCs using functional fullerene materials.