Asymmetric currents in a donor (D)-bridge (B)-acceptor (A) single molecule - revisit of the Aviram-Ratner diode

TL;DR

This study investigates quantum transport in a D-B-A single molecule, revealing asymmetric current response and rectification due to molecular dipole effects, revisiting the classic Aviram-Ratner diode concept.

Contribution

It demonstrates how intrinsic molecular dipoles influence rectification behavior in D-B-A molecules using DFT and Landauer-Büttiker formalism, providing new insights into molecular diode mechanisms.

Findings

Significant current rectification observed under opposite biases.

Molecular dipoles modulate charge distribution and electronic current.

Energy gap dynamics between D and A orbitals explain asymmetric conduction.

Abstract

The quantum transport via a donor (D)-bridge (B)-acceptor (A) single molecule is studied using density functional theory in conjunction with the Landauer-B\"{u}ttiker formalism. Asymmetric electrical response for opposite biases is observed resulting in significant rectification in current. The intrinsic dipole moment induced by substituent side groups in the molecule leads to enhanced/reduced polarization of the system under a forward/reverse applied potential, thus asymmetry in the charge distribution and the electronic current under bias. Under a forward bias, the energy gap between the D and A frontier orbitals closes and the current increases rapidly; whereas under a reverse bias, the D-A gap widens and the current remains small.