Extending Shelf‐Life of Two‐Step Method Precursor Solutions through Targeted Regulation for Highly Efficient and Reproducible Perovskite Solar Cells

Abstract Precursor solution aging process can cause significant influence on the photovoltaic performance of perovskite solar cells (PVSCs). Notably, we first observe that the aging phenomenon is more severe in the precursor of two‐step sequential method compared to that in one‐step method due to that the protic solvent isopropanol facilitates amine‐cation side reaction and iodide ions oxidation. Herein, we report a novel approach for selectively stabilizing both organic amine salt and lead iodide (PbI 2 ) precursor solutions in two‐step method. The introduction of benzene‐1,3‐dithiol into organic amine salt solution can mitigate amine‐cation side reactions due to the formation of an acidic and reducing environment. Simultaneously, decamethylferrocene (FcMe 10 /FcMe + 10 ) pair can act as a redox shuttle in PbI 2 solution to concurrently oxidize Pb 0 and reduce I 2 in cyclic manner. Consequently, the PVSCs device fabricated from ameliorative precursor solutions demonstrates superior power conversion efficiency of 25.31 %, retaining 95 % of its efficiency after 21 days of solution aging. Moreover, the unencapsulated devices maintain 85 % of primitive efficiency for 1500 h at maximum power point tracking under continuous illumination. This work establishes a fundamental guidance and scientific direction for the stabilization of two‐step perovskite precursor solutions.