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-C-8) 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-C-8 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-C-5 nanowire was mostly determined by thermally activated behavior. The observation of band like transport in the PTCDI-C-8 nanowire was attributed to the small number of charge traps in the constituent molecules. Meanwhile, band like transport was hardly attainable in the PTCDI-C-5 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-C-8 nanowire, thin films of polycrystalline PTCDI-C-8 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.