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Molecular design and control of fullerene-based bi-thermoelectric materials

Nature Materials volume 15, pages 289–293 (2016)Cite this article

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Abstract

Molecular junctions are a versatile test bed for investigating nanoscale thermoelectricity1,2,3,4,5,6,7,8,9,10 and contribute to the design of new cost-effective environmentally friendly organic thermoelectric materials11. It was suggested that transport resonances associated with discrete molecular levels could play a key role in thermoelectric performance12,13, but no direct experimental evidence has been reported. Here we study single-molecule junctions of the endohedral fullerene Sc3N@C80 connected to gold electrodes using a scanning tunnelling microscope. We find that the magnitude and sign of the thermopower depend strongly on the orientation of the molecule and on applied pressure. Our calculations show that Sc3N inside the fullerene cage creates a sharp resonance near the Fermi level, whose energetic location, and hence the thermopower, can be tuned by applying pressure. These results reveal that Sc3N@C80 is a bi-thermoelectric material, exhibiting both positive and negative thermopower, and provide an unambiguous demonstration of the importance of transport resonances in molecular junctions.

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Figure 1: Scanning tunnelling microscope images and tunnelling spectroscopy.
Figure 2: Thermopower and conductance simultaneous measurements.
Figure 3: Effect of pressure on Sc3N@C80 molecular junctions.
Figure 4: Effect of pressure on C60 molecular junctions and comparison with Sc3N@C80 junctions.

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Acknowledgements

This work was supported by the Swiss National Science Foundation (No. 200021-147143) as well as by the European Commission (EC) FP7 ITN ‘MOLESCO’ project no. 606728, UK EPSRC (grant nos. EP/K001507/1, EP/J014753/1, EP/H035818/1), Spanish MINECO (grant nos. MAT2011-25046 and MAT2014-57915-R), Comunidad de Madrid NANOFRONTMAG-CM (S2013/MIT-2850), MAD2D-CM (S2013/MIT-3007) and the Iraqi Ministry of Higher Education, Tikrit University (SL-20). L.R.-G. acknowledges financial support from UAM, IMDEA-Nanoscience and Spanish MECD (grant no. FPU014/03368). A.K.I. acknowledges financial support from Tikrit University.

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Authors and Affiliations

  1. Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain

    Laura Rincón-García, Charalambos Evangeli, Gabino Rubio-Bollinger & Nicolás Agraït

  2. Instituto Madrileño de Estudios Avanzados en Nanociencia IMDEA-Nanociencia, E-28049 Madrid, Spain

    Laura Rincón-García & Nicolás Agraït

  3. Department of Physics, Lancaster University, Lancaster LA1 4YW, UK

    Ali K. Ismael, Iain Grace & Colin J. Lambert

  4. Department of Physics, College of Education for Pure Science, Tikrit University, Tikreet 34001, Iraq

    Ali K. Ismael

  5. Instituto Universitario de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, E-28049 Madrid, Spain

    Gabino Rubio-Bollinger & Nicolás Agraït

  6. Department of Materials, University of Oxford, Oxford OX1 3PH, UK

    Kyriakos Porfyrakis

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  1. Laura Rincón-García
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  7. Nicolás Agraït
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  8. Colin J. Lambert
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Contributions

L.R.-G. performed the experiments and analysed the experimental data. A.K.I. and I.G. carried out the theoretical calculations. K.P. purified and provided the endohedral molecules. C.E. contributed to the experiments and to the experimental set-up and G.R.-B. contributed to the experimental set-up. N.A. and C.J.L. conceived and supervised the experiment and wrote the manuscript with contributions from all the authors.

Corresponding authors

Correspondence to Nicolás Agraït or Colin J. Lambert.

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The authors declare no competing financial interests.

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Rincón-García, L., Ismael, A., Evangeli, C. et al. Molecular design and control of fullerene-based bi-thermoelectric materials. Nature Mater 15, 289–293 (2016). https://doi.org/10.1038/nmat4487

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