Graphene assisting magnetic alignment of a high-performance semiconducting polymer for improved carrier transport

We report the fabrication of large-area highly aligned films of a naphthalene dicarboximide-based copolymer P(NDI2OD-T2) via solvent vapor annealing of as-spun films under a high magnetic field. Structural characterization reveals that the incorporation of a small amount of graphene nanosheets via solution mixing remarkably improves the degree of chain alignment and ordering of the semiconducting polymers. Field-effect transistors based on the magnetically aligned polymer/graphene composites exhibit a dramatic enhancement of electron mobility as well as extraordinarily high mobility anisotropy of 81, compared to pristine P(NDI2OD-T2)-based devices. We further proposed a mechanism to explain the enhancement of molecular orientation and charge transport, which is based on the assembling of polymer aggregates on the π-plane of graphene to facilitate magnetic alignment.