Abstract
Polymers are lightweight, flexible, solution-processable materials that are promising for low-cost printed electronics as well as for mass-produced and large-area applications. Previous studies demonstrated that they can possess insulating, semiconducting or metallic properties; here we report that polymers can also be semi-metallic. Semi-metals, exemplified by bismuth, graphite and telluride alloys, have no energy bandgap and a very low density of states at the Fermi level. Furthermore, they typically have a higher Seebeck coefficient and lower thermal conductivities compared with metals, thus being suitable for thermoelectric applications. We measure the thermoelectric properties of various poly(3,4-ethylenedioxythiophene) samples, and observe a marked increase in the Seebeck coefficient when the electrical conductivity is enhanced through molecular organization. This initiates the transition from a Fermi glass to a semi-metal. The high Seebeck value, the metallic conductivity at room temperature and the absence of unpaired electron spins makes polymer semi-metals attractive for thermoelectrics and spintronics.
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Change history
16 April 2014
In the version of this Article originally published, the grazing incidence wide-angle X-ray scattering (GIWAXS) pattern shown in Fig. 2c was obtained for a contaminated thin-film sample, this has now been replaced by the correct scattering pattern; the related caption should read "c, PEDOT–Tos, being qualitatively different from the PEDOT–PSS samples, exhibits higher-order lamellae-related peaks, and also significant in-plane ordering." In relation, the sentence beginning "However, the experimental scattering pattern shows pronounced off-axis scattering..." pertains to the contaminated sample and should not have been included. Furthermore, the sentence beginning "The PEDOT–Tos sample (Fig. 2c) exhibits several sharp refraction peaks..." should have begun "The PEDOT–Tos sample (Fig. 2c) exhibits several sharper peaks, and significant in-plane scattering..." In the sentence beginning "The orthorhombic unit cell suggested for..." the value of the full-width at half-maximum should have been '<35°'. These errors do not affect the results and conclusions, and have been corrected in the online versions of the Article.
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Acknowledgements
The authors acknowledge the European Research Council (ERC-starting-grant 307596), the Swedish foundation for strategic research (project: ‘Nano-material and Scalable TE materials’), the Knut and Alice Wallenberg foundation (project ‘Power paper’), The Swedish Energy Agency and the Advanced Functional Materials Center at Linköping University. Research in Mons is supported by the European Commission and Région Wallonne (FEDER ‘Revêtements Fonctionnels’ programme), BELSPO (IAP 7/05), the OPTI2MAT Excellence program of Région Wallonne, and FNRS-FRFC. Research at the University of South Australia is supported by ITEK, the commercialization company for UniSA. Research at NTNU is supported by the Norwegian Research Council.
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O.B., Z.U.K. and H.W.—fabrication of the various PEDOT–PSS samples and some PEDOT–Tos samples; thermoelectric and optical characterization of PEDOT–PSS and PEDOT–Tos samples. S.B. and M.F.—photoelectron spectroscopy characterization. D.R.E., M.F., P.H-T. and P.J.M.—fabrication of the various VPP PEDOT–Tos samples. D.D. and W.M.C.—characterization with electron paramagnetic resonance spectroscopy. J-B.A., Y.H.G., D.W.B. and J.W.A.—polarized microscopy, X-ray diffraction and GIWAXS structure analysis. S.D. and R.L.—atomic force microscopy characterization I.Z., M.B. and X.C.—theoretical insight, interpretation and project leading. All authors have been involved in the redaction of the manuscript.
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Bubnova, O., Khan, Z., Wang, H. et al. Semi-metallic polymers. Nature Mater 13, 190–194 (2014). https://doi.org/10.1038/nmat3824
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DOI: https://doi.org/10.1038/nmat3824
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