Theory of electrical rectification in a molecular monolayer

TL;DR

This paper develops a theoretical model for electrical rectification in molecular monolayers, showing how molecular energy levels and electrostatic potential profiles influence current direction and magnitude.

Contribution

It introduces a combined ab initio and tight-binding approach to analyze rectification, highlighting the impact of electrostatic potential profiles on device behavior.

Findings

Rectification depends on LUMO and HOMO positions relative to electrode Fermi levels.

Electrostatic potential profile significantly influences rectification direction.

Rectification can occur opposite to traditional Aviram-Ratner predictions.

Abstract

The current-voltage characteristics in Langmuir-Blodgett monolayers of \gamma-hexadecylquinolinium tricyanoquinodimethanide (C16H33Q-3CNQ) sandwiched between Al or Au electrodes is calculated, combining ab initio and self-consistent tight binding techniques. The rectification current depends on the position of the LUMO and HOMO relative to the Fermi levels of the electrodes as in the Aviram-Ratner mechanism, but also on the profile of the electrostatic potential which is extremely sensitive to where the electroactive part of the molecule lies in the monolayer. This second effect can produce rectification in the direction opposite to the Aviram-Ratner prediction.