Binary solvent mixtures were routinely used to induce the hierarchical assembly of poly(3-hexylthiophene) (P3HT) in the liquid phase. This technique has garnered a lot of interest as a route to well-organized films and composites, but, to date, the impact that the attributes of the liquid-phase aggregates and solvent mixtures have on the organization of the films have only been partially scrutinized. The molecular weight and concentration dependence of P3HT assembly in three binary solvent mixtures containing chloroform and acetonitrile, n-hexane, or dichloromethane were studied using ultraviolet/visible absorbance spectroscopy and dynamic light scattering techniques. Films drop cast under slow and rapid evaporation conditions were observed using optical and atomic force microscopy. In general, there is no evidence that the characteristics of the liquid phase P3HT aggregates impact the structures of the films, but films cast from these solvent mixtures under rapid evaporation conditions exhibit an array of disparate morphologies and mesoscale patterning. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 624-638