Role of redox centre in charge transport investigated by novel self-assembled conjugated polymer molecular junctions.

Zongrui Wang,Xiaolong Fu,Bo W Laursen,Yonggang Zhen,Erjing Wang,Zhongming Wei,Wenping Hu,Tao Li,Huanli Dong,Ye Zou,Kasper Nørgaard,Rune Hviid

doi:10.1038/ncomms8478

Abstract

Molecular electronics describes a field that seeks to implement electronic components made of molecular building blocks. To date, few studies have used conjugated polymers in molecular junctions despite the fact that they potentially transport charge more efficiently than the extensively investigated small-molecular systems. Here we report a novel type of molecular tunnelling junction exploring the use of conjugated polymers, which are self-assembled into ultrathin films in a distinguishable ‘planar' manner from the traditional vertically oriented small-molecule monolayers. Electrical measurements on the junctions reveal molecular-specific characteristics of the polymeric molecules in comparison with less conjugated small molecules. More significantly, we decorate redox-active functionality into polymeric backbones, demonstrating a key role of redox centre in the modulation of charge transport behaviour via energy level engineering and external stimuli, and implying the potential of employing tailor-made polymeric components as alternatives to small molecules for future molecular-scale electronics.

Highlights

Molecular electronics describes a field that seeks to implement electronic components made of molecular building blocks
Experimental evidence indicates that conjugated polymers (CPs) are self-assembled into ultrathin films (2–3 nm) in a distinguishable ‘planar’ manner from the vertically oriented self-assembled monolayers (SAMs), they can still implement their molecular-specific characteristics in tunnelling junctions in comparison with the less conjugated small molecules
Devices based on SAMs of small molecules (for example, 1-dodecanethiol (C12) and oligo(phenylene ethynylene)s (OPE3)) for control experiments are prepared in the same process

Summary

Introduction

Molecular electronics describes a field that seeks to implement electronic components made of molecular building blocks. We decorate redox-active functionality into polymeric backbones, demonstrating a key role of redox centre in the modulation of charge transport behaviour via energy level engineering and external stimuli, and implying the potential of employing tailor-made polymeric components as alternatives to small molecules for future molecular-scale electronics. Conjugated molecules are better candidates for circuit elements, often termed ‘molecular wires’ To date, both individual and self-assembled monolayers (SAMs) of conjugated small molecules have been extensively studied as the active components in tunnelling junctions[16,17]. Experimental evidence indicates that CPs are self-assembled into ultrathin films (2–3 nm) in a distinguishable ‘planar’ manner from the vertically oriented SAMs, they can still implement their molecular-specific characteristics in tunnelling junctions in comparison with the less conjugated small molecules. This work innovatively proposes the potential of employing CPs as alternatives to typical small-molecule assemblies for device construction in the field of molecular electronics, as well as their tailorability on device performance via synthetic methods for desirable functionalities

Methods

Results

Conclusion