Electrical transport through single nanowires of dialkyl perylene diimide

Abstract

We investigated electrical charge transport through individual strands of single-crystalline dipentyl perylene tetracarboxylic diimide (PTCDI-C 5) and dioctyl perylene tetracarboxylic diimide (PTCDI-C8) nanowires prepared by a solution-phase self-assembly method. Temperature-dependent mobility measurements (100-280 K) revealed distinct electrical transport characteristics in the two types of nanowires. The PTCDI-C8 nanowire having shorter intermolecular distances exhibited a transition in the electrical transport mechanism from a thermally activated process (the multiple-trap-and-release model) to a band-like transport (the signature of excellent electrical conduction) with increasing temperature. In contrast, the transport through the PTCDI-C5 nanowire was mostly determined by thermally activated behavior. The observation of band-like transport in the PTCDI-C8 nanowire was attributed to the small number of charge traps in the constituent molecules. Meanwhile, band-like transport was hardly attainable in the PTCDI-C5 nanowire due to the presence of a large number of charge traps, which followed an exponential energy distribution. Unlike the case of the single-crystal PTCDI-C8 nanowire, thin films of polycrystalline PTCDI-C8 contained significant numbers of exponentially distributed charge traps. Consequently, band-like transport was not observed. Overall, our results presented here demonstrate the importance of attaining good molecular ordering and orientation within the electrically active molecular layer with a high electronic purity for achieving superior electrical transport, i.e., band-like transport.