Robust reproducible large-area molecular rectifier junctions

Abstract

Stable rectifying molecular junctions have been obtained by sandwiching self-assembled monolayer films containing “push-pull” donor-π-acceptor (D-π-A) moieties between Au and poly(3,4-ethylenedioxythiophene) electrodes. These D-π-A moieties possess moderate molecular dipoles, but assemble into films with nearly zero dipole moment due to adoption of high average tilt angles. Nevertheless reproducible and well-behaved rectifications (ratio up to 3.3) in the expected polarity were obtained. At low biases, the current-voltage characteristics follow Simmon’s tunneling theory with reasonable barrier heights and an effective tunnel mass of ∼0.5me. This suggests that asymmetric tunneling, and not carrier injection, is the origin of the rectification.