Oscillating Seebeck coefficients in π-stacked molecular junctions

Al-Khaykanee, Mohsin K. and Ismael, Ali K. and Grace, Iain and Lambert, Colin J. (2018) Oscillating Seebeck coefficients in π-stacked molecular junctions. RSC Advances, 8 (44). pp. 24711-24715. ISSN 2046-2069

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When a linear aromatic molecule within a nanogap is bound only to a source electrode, and an adjacent molecule is bound only to a drain electrode, the two molecules can interact via pi-pi stacking, which allows electrons to flow from the source to the drain, via pi-pi bonds. Here we investigate the thermoelectric properties of such junctions, using mono-thiol oligo-phenylene ethynylene (OPE3)-based molecules as a model system. For molecules which are para-connected to the electrodes, we show that the Seebeck coefficient is an oscillatory function of the length L of the pi-pi overlap region and exhibits large positive and negative values. This bi-thermoelectric behavior is a result of quantum interference within the junction, which behaves like a molecular-scale Mach-Zehnder interferometer. For junctions formed from molecular monolayers sandwiched between planar electrodes, this allows both hole-like and electron-like Seebeck coefficients to be realized, by careful control of electrode separation On the other hand for meta-connected molecules, the Seebeck coefficient is insensitive to L, which may be helpful in designing resilient junctions with more stable and predictable thermoelectric properties.

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Journal Article
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RSC Advances
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09 Oct 2019 09:10
Last Modified:
18 Sep 2023 01:40