Design of Superhydrophobic Surfaces for Stable Perovskite Solar Cells with Reducing Lead Leakage

Abstract Environment‐related degradation and lead leakage in perovskite solar cells have posed a big challenge for their commercialization. Here, design of superhydrophobic surfaces is demonstrated as an effective strategy toward these issues, in which thiol‐functionalized perfluoroalkyl molecules are employed to chemically modify the lead halide perovskite film and metal electrode via a vapor‐assisted self‐assembly process. Due to the van der Waals forces, the generation of self‐assembly monolayer prefers to pack in a dense way, resulting in the formation of a closest‐packed, crystalline‐like molecular array. This dense array is endowed with a low‐surface‐energy chemistry that can not only enhance the water and oxygen resistance of the completed device but also reduce the defect density on the perovskite surfaces. These merits eventually boost the efficiency of inverted perovskite solar cells up to 21.79% along with a substantially improved long‐term stability. More importantly, the thiol‐functionalized superhydrophobic array can immobilize most of the undercoordinated lead ions on the perovskite surfaces by metal‐thiol coordination effect, which results in suppressing the lead leakage from the water‐soluble lead halide perovskites. Therefore, an avenue is pointed out here to fabricate stable perovskite solar cells with reducing lead leakage, representing a substantial step toward practical applications.