First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions

Here we present a theoretical study of the thermoelectric transport through [2,2]paracyclophane-based single-molecule junctions. Combining electronic and vibrational structures, obtained from density functional theory (DFT), with nonequilibrium Green's function techniques allows us to treat both electronic and phononic transport properties at a first-principles level. For the electronic part, we include an approximate self-energy correction, based on the DFT+Σ approach. This enables us to make a reliable prediction of all linear response transport coefficients entering the thermoelectric figure of merit ZT. Paracyclophane derivatives offer a great flexibility in tuning their chemical properties by attaching different functional groups. We show that, for the specific molecule, the functional groups mainly influence the thermopower, allowing us to tune its sign and absolute value. We predict that the functionalization of the bare paracyclophane leads to a largely enhanced electronic contribution Z_elT to the figure of merit. Nevertheless, the high phononic contribution to the thermal conductance strongly suppresses ZT. Our work demonstrates the importance to include the phonon thermal conductance for any realistic estimate of the ZT for off-resonant molecular transport junctions. In addition, it shows the possibility of a chemical tuning of the thermoelectric properties for a series of available molecules, leading to equally performing hole- and electron-conducting junctions based on the same molecular framework.

Subject (DDC)

530 Physics

Cite This

ISO 690

BÜRKLE, Marius, Thomas J. HELLMUTH, Fabian PAULY, Yoshihiro ASAI, 2015. First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions. In: Physical Review B. 91(16), 165419. ISSN 0163-1829. eISSN 1095-3795. Available under: doi: 10.1103/PhysRevB.91.165419

BibTex

@article{Burkle2015First-30975,
  year={2015},
  doi={10.1103/PhysRevB.91.165419},
  title={First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions},
  number={16},
  volume={91},
  issn={0163-1829},
  journal={Physical Review B},
  author={Bürkle, Marius and Hellmuth, Thomas J. and Pauly, Fabian and Asai, Yoshihiro},
  note={Article Number: 165419}
}

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    <dcterms:abstract xml:lang="eng">Here we present a theoretical study of the thermoelectric transport through [2,2]paracyclophane-based single-molecule junctions. Combining electronic and vibrational structures, obtained from density functional theory (DFT), with nonequilibrium Green's function techniques allows us to treat both electronic and phononic transport properties at a first-principles level. For the electronic part, we include an approximate self-energy correction, based on the DFT+Σ approach. This enables us to make a reliable prediction of all linear response transport coefficients entering the thermoelectric figure of merit ZT. Paracyclophane derivatives offer a great flexibility in tuning their chemical properties by attaching different functional groups. We show that, for the specific molecule, the functional groups mainly influence the thermopower, allowing us to tune its sign and absolute value. We predict that the functionalization of the bare paracyclophane leads to a largely enhanced electronic contribution Z&lt;sub&gt;el&lt;/sub&gt;T to the figure of merit. Nevertheless, the high phononic contribution to the thermal conductance strongly suppresses ZT. Our work demonstrates the importance to include the phonon thermal conductance for any realistic estimate of the ZT for off-resonant molecular transport junctions. In addition, it shows the possibility of a chemical tuning of the thermoelectric properties for a series of available molecules, leading to equally performing hole- and electron-conducting junctions based on the same molecular framework.</dcterms:abstract>
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Bibliography of Konstanz

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