Graphitic substrates with different curvatures (i.e. carbon nanotubes, carbon nanofibers and graphene) are used to induce the crystallization of poly(3-hexylthiophene) (P3HT) on the surfaces. The effect of P3HT molecular weight (Me) and the surface curvature on P3HT crystal structures is investigated. P3HTs with an M-n above the chain folding threshold M-n value form nanowires from all graphitic surfaces. P3HTs with an M-n below the chain folding threshold M-n value form nanowires from graphitic surfaces with a large curvature (e.g. SWCNTs) but produce nanoribbons from graphitic surfaces with smaller curvatures (e.g. MWCNTs, CFs, and graphene). The kinetic study of P3HT crystallizations on graphitic surfaces reveals that intermolecular interactions, specific surface area and curvature have major effects on P3HT crystallization rate on graphitic surfaces. (C) 2018 Elsevier Ltd. All rights reserved.