DL‐Serine Hydrazide Hydrochloride Multiple‐site Synergy Induced Effective and Stable Formamidine‐Rich Perovskite Solar Cells

Abstract The efficiency and stability of solar cells are two key indicators that determine for the commercial feasibility of photovoltaic devices. Formamidine‐cesium perovskite has been extensively investigated since its excellent thermal stability and has great potential in achieving high power conversion efficiency. However, during the aging process, especially under light conditions, formamidine‐rich perovskites are prone to produce iodine, and the escape of iodine is one of the important factors leading to device degradation. Here, DL‐Serine Hydrazide Hydrochloride containing the reducing group is introduced into the precursor solution of formamidine‐cesium perovskite, which achieves multiple‐site passivation. Hydrazine reacts with iodine to reduce it to iodine ions, inhibiting the escape of iodine. In addition, carbonyl groups and uncoordinated lead ions form coordination bonds to reduce defects. In the end, the perovskite solar cell with DL‐Serine Hydrazide Hydrochloride added achieves a champion efficiency of 22.22%, and maintains 85.88% of the initial efficiency after continuous exposure under 1 sun for 7000 s at a relative humidity of ≈40%. Additionally, DL‐Serine Hydrazide Hydrochloride added device shows good stability in air environments with relative humidity of 50%–60%. DL‐Serine Hydrazide Hydrochloride improves the stability of formamidine‐rich perovskite solar cells and provides a low‐cost strategy for commercial development.