(a) Sketch of the resonant tunneling system used to model the donor-bridge-acceptor system shown in (b). Three levels are coupled to a left (l) and to a right (r) electron reservoir via asymmetric tunneling barriers. In the presence of a bias voltage the left and the right Fermi energies, and , respectively, differ from each other, thus generating a current when resonances are matched.
(Left) HOMO (top panel) and LUMO (bottom panel) energies for the molecular structures with bridges and (right) charge distribution of FMO for (I), (II), and (III).
(a) In and , negative external electric field when the A group is in a potential of reverse polarization. Positive external electric field when the A group is in a potential of forward polarization. For the same applied potential the charge accumulation is greater than the negative one exhibiting a typical rectifier signature. In and prominent rectifications of and with resonance in the region; (b) negative external electric field when the A group is in a potential of reverse polarization. Positive external electric field when the A group is in a potential of forward polarization followed by resonances with intense saturation values. (c) Decrease in the rectification potential generated with a weak coupling because of the noninteracting DA groups.
Two selected curves comparing the charge distribution (dots) in the acceptor group for (a) and (b) and the current (solid full line).
Numerical parameters used in the transport model to better fit the ab initio calculations.
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