Precursor Stabilization Strategies via Vapor–Solid Reaction for Reproducible and High-Efficiency Vapor-Deposited Perovskite Solar Cells

The stability of perovskite precursors significantly impacts the performance of perovskite solar cell (PSCs). Notably, in the vapor-solid reaction perovskite fabrication process, both organic amine salt precursors and inorganic lead halide precursors are involved. Consequently, the long-term stability of these precursor materials plays a critical role in enabling the industrial-scale production of PSCs. Our observations revealed that the inherent instability of iodide ions (I^-) in formamidinium iodide (FAI) precursor solutions accelerates solution aging. Additionally, the photoinstability of lead iodide (PbI₂) promotes I^- loss, generating iodine vacancies in the material. To address these issues, we introduced l-ascorbic acid (LAA) into the organic amine salt precursor solution to create an acidic and reducing environment, thereby reducing side reactions of the amine salt. Additionally, we effectively enhanced the stability of the PbI₂ film by performing a surface dimensional regulation strategy on the PbI₂ precursor film with 2-thiophenethylammonium iodide (2-ThEAI) vapor, inhibiting the formation of Pb⁰. As a result, PSCs fabricated by the optimized precursors achieve a power conversion efficiency (PCE) of 22.51% (@0.16 cm²) and 20.02% (@10 cm²). Remarkably, the four-terminal tandem photovoltaic device integrated with silicon solar cells achieves a PCE of 29.39%, demonstrating exceptional performance potential for next-generation solar technologies.