Alleviation of Precursor Degradation Induced by DMF/DMSO Mixture for Enhanced Performance of Perovskite Solar Cells

Abstract The precursor quality critically determines the morphology, grain size, crystallinity, and trap state density of the perovskite films. A long shelf life of the perovskite precursor could greatly benefit the reliable upscaling of perovskite solar cells (PSCs). Herein, we suggest that the most commonly used N, N‐Dimethylformamide/Dimethyl sulfoxide (DMF/DMSO) mixed solvent exhibits more severe degradation compared to its corresponding single solvents, due to the complex interplay of reactions, including hydrolysis, oxidation, and deprotonation of precursor species in the solution. 2‐thiouracil (Th) was thus introduced into the precursor to inhibit these side reaction chains and effectively alleviate the detrimental degradation of cations and iodide ions (I⁻). The synergistic effects of Th allow it to bind with undercoordinated Pb 2+ , modulating the crystallization process and thereby achieving high‐quality films with a low defect density. Consequently, Th‐based precursor demonstrates enhanced shelf life, retaining 94.78% of the initial efficiency (25.13%) of the device prepared from fresh solution after 30 days of aging, compared to 64.22% for the control sample. The target device also exhibits remarkable stability, maintaining 87.8% of its initial efficiency after 1000 h of maximum power point tracking.