Effect of the heteroatom-separation on the electron transport behavior of heteroacene-junctions

Abstract The electron transport behavior through a series of symmetric and asymmetric dithiapentacenes (DPA) dithiolate junctions are theoretically investigated on the basis of density functional theory together with non-equilibrium Green’s function methods. The current-voltage characteristics of a series of DPAs with different separation of the heteroatoms have been calculated. The results indicate that the current correlates with the energy levels, the spatial distribution of molecular orbitals, and the transmission probability within the bias window. The separation of the two heteroatoms leads to an extension of the central quinoid structure, which forms the effective electron transport pathway. It can also lower the energy levels of the molecular orbitals and shift the transmission peaks towards the Fermi level, leading to a dramatic increase in the junction conductance. In particular, the current through 6,13-DPA is almost one hundred times greater than that through 5,12-DPA. Upon increasing the heteroatom separation, the junction current then tends towards a specific limit.