Stable Metal-Halide Perovskite Colloids in Protic Ionic Liquid

Obtaining long-term stable and robust perovskite colloids solution remains an important scientific challenge due to the limited interaction between solvent and perovskite solutes. Here, we unveil the formation mechanism of chemically robust perovskite precursor solutions under ambient conditions using methylammonium acetate (CH₃NH₃•CH₃COO, MAAc) protic ionic liquid (PIL) solvent. Tens of nanometers colloids are assembled on the molecular level via regular oriented gel-like lamellae with a mean thickness of 34.69 nm, width of 56.81 nm, and distance of 91.05 nm. Stable colloids could be realized in the MAAc precursor solution with uniform distribution through N-H•••O=C-O⁻ intermolecular hydrogen bonds and the O=C-O⁻ (Ac⁻) and Pb²⁺ coordination interactions, in which the coordination number of Pb²⁺ ions increased slightly from 1.6 ± 0.2 to 1.7 ± 0.4 as the MAAc precursor concentration increased, leading to the Pb-O scattering distance of only 1.7 Å in the R space. Moreover, first-principles molecular dynamics simulations also demonstrate that the Ac⁻ anions can promote the formation and stabilization of precursor solutions. These interactions yielded more stable perovskite colloids precursors solutions compared to traditional N, N-dimethylformamide and dimethyl sulfoxide solution under heat stress, air aging, and electrolytic dissociation. The abundant varieties of robust PIL solvents could potentially facilitate the success of many perovskite-based optoelectronic devices.