Current-voltage characteristics in donor-acceptor systems: Implications of a spatially varying electric field

TL;DR

This study models the current-voltage behavior of donor-acceptor molecular devices, revealing asymmetric NDR effects caused by bias-induced electronic phase transitions, and offers a simple explanation for experimental observations.

Contribution

It introduces a one-dimensional model with spatially varying electric fields to explain NDR in molecular devices, highlighting the role of electronic phase changes.

Findings

Asymmetric I-V characteristics with NDR at a critical bias

Electronic structure transitions cause NDR phenomena

Model aligns with experimental molecular device data

Abstract

We have studied the transport properties of a molecular device composed of donor and acceptor moieties between two electrodes on either side. The device is considered to be one-dimensional with different on-site energies and the non-equilibrium properties are calculated using Landauer's formalism. The current-voltage characteristics is found to be asymmetric with a sharp Negative Differential Resistance at a critical bias on one side and very small current on the other side. The NDR arises primarily due to the bias driven electronic structure change from one kind of insulating phase to another through a highly delocalized conducting phase. Our model can be considered to be the simplest to explain the experimental current-voltage characteristics observed in many molecular devices.