Precursor Solvation in 2-Methoxyethanol/DMI Binary Solvents and Anti-Solvent-Free Film Formation of FA–MA Perovskites

The state of a perovskite precursor ink is set by how its solvents coordinate the precursors, yet the roles of individual solvents in green mixtures remain poorly understood. We examine how 2-methoxyethanol (2Me) and 1,3-dimethyl-2-imidazolidinone (DMI) share the solvation of the four precursors of a formamidinium–methylammonium (FA–MA) lead iodide–bromide ink: PbI2, PbBr2, FAI and MABr. Cluster–continuum DFT calculations (r2SCAN-3c/SMD) of the exchange of 2Me for DMI in the first solvation shell show that PbI2 prefers DMI, whereas PbBr2 and MABr prefer 2Me (+4.9 and +6.3 kJ mol−1 per DMI) and FAI has no clear preference (+2.0 kJ mol−1); in FAI and MABr, 2Me donates O–H···X− hydrogen bonds. A thermodynamic model built on these energies is consistent with 2Me-rich mixtures (about 10–20 vol% DMI) as a tentative compromise. All 2Me/DMI mixtures wet PTAA, with the contact angle falling from 24.7° (2Me) to 13.3° (DMI). Without an anti-solvent (gas quenching only), the 2Me:DMI ink gives on PTAA a film with larger grains in the imaged areas than the DMF:DMSO ink, with the same absorption onset (776 nm) and a similar photoluminescence band. With literature data on blade-coated films, these results support testing 2Me/DMI for anti-solvent-free, large-area processing of FA–MA perovskites.