Selective crystallization of conjugated polymer nanowires from graphene-coated surfaces*

Solution-based crystallization of conjugated polymers is a promising route to develop hierarchical structures for organic electronic devices, especially solar cells. Well-defined nucleation sites in supersaturated solutions can regulate the crystallization behavior to control the morphology of the material. We have developed an approach to tune the hysteresis between melting and crystallization of poly(3-hexylthiophene) in a marginal solvent, using temperature controlled fractionation. This process produces supersaturated solutions in a metastable state at room temperature, suppressing homogenous nucleation of crystals but allowing for heterogeneous crystallization on nucleation sites. We show that in these metastable solutions, crystalline nanowires are selectively grown on graphene-coated surfaces and highly orientated pyrolytic graphite.