Directed crystallization of poly(3-hexylthiophene) in micrometre channels under confinement and in electric fields.

We present two methods for controlling the in-plane alignment of polymer chains in poly(3-hexylthiophene) (P3HT) films within the channel of a field effect transistor device. Solvent-induced dewetting into the transistor channels of a prepatterned, bottom-gate bottom-contact transistor channel followed by controlled, low nucleation density recrystallization under confinement resulted in a preferential orientation of the π-stacked nanocrystalline lamellae parallel to the resulting P3HT micrometre-sized lines. The contrasting alignment, of perpendicular lamellae, was induced by application of an electric field during recrystallization. Preliminary measurements of the dependence of charge transport mobility on the global orientation of the polymer chain direction are consistent with faster charge transport perpendicular to the π-stacked lamellae (direction parallel to the polymer chains) compared to along the π-stacking direction in the common edge-on oriented morphology. This journal is © The Royal Society of Chemistry 2012