Experimental Observation of Ultrahigh Mobility Anisotropy of Organic Semiconductors in the Two-Dimensional Limit

Charge transport properties near the interface of organic material are one of the most fundamental research fronts of organic transistors. Although carrier mobility has been well studied in bulk single crystal organic semiconductors based on field effect transistors, the experimental result of mobility anisotropy is far from the theoretical one because of crystal cracks, step edge states, and other surface state issues. Here, highly ordered and molecularly thin N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) is adopted to study the anisotropic transport property. We find that the PTCDI-C13 film with monomolecular thickness exhibits a high mobility anisotropy ratio up to ∼28 at room temperature, which is highly consistent with the theoretical result and is 10 times higher than previously reported results of bulk single-crystal organic semiconductors. The carrier transport behavior in the single layer is attributed to the hopping mechanism with an activation energy kBT0 ≈ 33.6 meV. Our results corroborate the intrinsic charge transport properties of electroactive organic layered materials at the interfaces.