Issue 19, 2015

Mechanical tuning of conductance and thermopower in helicene molecular junctions

Abstract

Helicenes are inherently chiral polyaromatic molecules composed of all-ortho fused benzene rings possessing a spring-like structure. Here, using a combination of density functional theory and tight-binding calculations, it is demonstrated that controlling the length of the helicene molecule by mechanically stretching or compressing the molecular junction can dramatically change the electronic properties of the helicene, leading to a tunable switching behavior of the conductance and thermopower of the junction with on/off ratios of several orders of magnitude. Furthermore, control over the helicene length and number of rings is shown to lead to more than an order of magnitude increase in the thermopower and thermoelectric figure-of-merit over typical molecular junctions, presenting new possibilities of making efficient thermoelectric molecular devices. The physical origin of the strong dependence of the transport properties of the junction is investigated, and found to be related to a shift in the position of the molecular orbitals.

Graphical abstract: Mechanical tuning of conductance and thermopower in helicene molecular junctions

Article information

Article type
Paper
Submitted
26 Feb 2015
Accepted
07 Apr 2015
First published
14 Apr 2015
This article is Open Access
Creative Commons BY-NC license

Nanoscale, 2015,7, 8793-8802

Author version available

Mechanical tuning of conductance and thermopower in helicene molecular junctions

J. Vacek, J. V. Chocholoušová, I. G. Stará, I. Starý and Y. Dubi, Nanoscale, 2015, 7, 8793 DOI: 10.1039/C5NR01297J

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