Perovskite Solution Aging: What Happened and How to Inhibit?

The studies of perovskite film in the perovskite solar cells (PSCs) mainly focus on their crystallization and growth, but the reactions that happen in the precursor solutions are still not very clear, which is leading to the bad reproducibility for high-efficient devices. We demonstrated that, in the methylammonium- and formamidinium-mixed organic cation perovskite solution, the methylamine molecule could be first generated from the deprotonation of methylammonium iodide, and then condensate with formamidinium iodide to form N-methyl formamidinium iodide and N, N′-dimethyl formamidinium iodide. The triethyl borate was carried out as a stabilizer to restrain the deprotonation of methylammonium iodide in the precursor solutions, resulting in the elimination of the impurity phase in perovskite films. We think that the introduction of stabilizer in the perovskite precursor solution will become a common strategy for mixed-organic-cation PSCs in the future to improve the reproducibility and efficiency.