120-Day perovskite solution stability via deprotonation and iodine reduction by a pyrazolone-based additive

Perovskite precursor solution undergoes degradation pathways such as deprotonation and iodide oxidation overtimes, which result in short shelf life. Such issue might not be significant for research labs where fresh solutions can be made every time, yet high solution stability improves workflow and reproducibility while reduces cost for actual manufacturing process. In this work, we identify the suitable and low-cost additive, 1-(4-sulfophenyl)-3-methyl-5-pyrazolone (SMP), to suppress undesirable reactions and prolong solution efficacy. To accelerate solution aging study, we carefully probed aging by-product quantities under room temperature over 120 days via nuclear magnetic resonance spectroscopy (NMR), establishing a standard heat protocol (60 °C) and collecting the database to assess acceleration factors by comparing by-product quantities with respect to starting organic cations. The aged perovskite solution with the SMP stabilizer exhibits 40-time-less by-products in comparison to the control solution that was aged under the same conditions. Perovskite solar cells (PSCs) from such solution with the SMP additive realize similar power conversion efficiencies (PCEs) to those from the fresh solution. Both the accelerated protocol and the long-term 1 H NMR tracking reveal over 120-day stability, marking SMP potential for PSC production. • A pyrazolone-based additive can suppress deprotonation and iodide oxidation. • Aging by-product quantities under room temperature over 120 days are illustrated. • An accelerated degradation protocol and its acceleration factor are obtained. • Insights into degradation mechanism and its prevention are explored. • Stable perovskite solution beyond 120 days can be achieved with a low-cost method.