Rectification effect in organic junctions based on aryl thin films covalently attached to a multilayer graphene electrode

TL;DR

This study investigates the electronic transport and rectification effects in organic junctions using covalently attached aryl thin films on multilayer graphene electrodes, revealing similar electronic responses to gold electrodes despite different interfacial properties.

Contribution

It introduces the use of atomically thin multilayer graphene as an electrode in organic junctions and compares its interfacial electronic structure with traditional gold electrodes.

Findings

Similar electronic responses in junctions with graphene and gold electrodes.

Strong orbital coupling and orbital pinning at the interface.

Interfacial properties can be tuned without significantly altering transport behavior.

Abstract

The quantum interaction between molecules and electrode s material at molecules-electrode interfaces is a major ingredient in the electronic transport properties of organic junctions. Driven by the coupling strength between the two materials, it results mainly in a broadening and an energy shift of the interacting molecular orbitals. Using new electrodes materials, such as the recent semi-conducting two-dimensional nanomaterials, has become a recent challenge in the field of molecular-organic electronics that opens new possibilities for controlling the interfacial electronic properties and thus the charge injection properties. In this article, we report the use of atomically thin two-dimensional multilayer graphene films as base electrode in organic junctions with a vertical architecture. The interfacial electronic structure dominated by the covalent bonding between bis-thienyl benzene diazonium-based molecules and the multilayer graphene electrode has been probed by ultraviolet photoelectron spectroscopy and the results compared with those obtained on junctions with standard Au electrodes. Room temperature injection properties of such interfaces have been also explored by electronic transport measurements. We find that, despite strong variations of the density of states, the Fermi energy and the injection barriers, both organic junctions with Au base electrodes and multilayer graphene base electrodes show similar electronic responses. We explain this observation by the strong orbital coupling occurring at the bottom electrode-bis(thienyl) benzene molecules interface and by the pinning of the hybridized molecular orbitals.