Theoretical investigation on electron transport properties of a single molecular diode

The nonequilibrium Green's function (NEGF) approach in combination with density functional theory (DFT) was used to investigate the electron transport properties of a single diode molecule that consists of two weakly coupled electron donating π-system and electron withdrawing π-system, resembling the conventional p-n junctions. The results demonstrate rectification behavior of the diode molecule and the maximum rectification ratio is up to 7.7. The mechanism of the rectification behavior was analyzed in terms of the evolution of molecular energy levels, the change of spatial distribution of molecular orbitals, and the electron transmission spectra. The asymmetric evolutions of the energy levels and the alignment of the states localized on the electro donating and electron withdrawing segments with the applied voltage were found to be essential in generating this rectification behavior for the molecular system.