Rectifying effect in polar conjugated molecular junctions: a first-principles study.

The electronic transport properties of polar conjugated molecules with different molecular lengths sandwiched between two gold electrodes are investigated using a fully self-consistent non-equilibrium Green's function method combined with density functional theory. The calculated current-voltage curve shows obvious asymmetric feature with the increasing of the molecular length. The observed asymmetric characteristic results from the dissimilar shift of the perturbed molecular energy levels and the spatial asymmetry of tunneling wave functions under external bias voltage. The rectifying effect can be further enhanced by introducing an asymmetric coupling.