Damp-Stable Perovskite/Silicon Tandem Solar Cells with Internal Encapsulating Sulfonium-Based Molecules

Industrially textured perovskite/silicon tandem solar cells are among the most promising candidates for future low-cost photovoltaic deployment. Air-annealing is an inevitable process to fabricate high-quality perovskite films during the hybrid two-step deposition method. However, this process often leads to severe perovskite decomposition on the surface because of moisture exposure and high-temperature. To address this issue, a stabilizing additive─dimethylphenethylsulfonium iodide (DMPESI)─is introduced into the organic salt solution, forming a hydrophobic internal encapsulation layer. As a result, the perovskite surface decomposition is effectively suppressed during the air-annealing process and the resulting perovskite films exhibit significantly enhanced film stability and quality. Consequently, the industrially textured perovskite/silicon tandem solar cells delivered an impressive efficiency of 30.49% (1.21 cm²). Moreover, encapsulated tandem devices retained 84% of their initial efficiency after nearly 1800 h of maximum power point tracking (MPPT) (ISOS-L-1) and 80% after 723 h of damp heat test (ISOS-D-3).