Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Semi-metallic polymers

A Corrigendum to this article was published on 21 May 2014

This article has been updated

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.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Electronic structure of conducting polymers.
Figure 2: Structure of various PEDOT thin films.
Figure 3: Electronic valence levels and nature of the charge carriers.
Figure 4: Thermopower and electrical conductivity of PEDOT derivatives.

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X-ray scattering (GIWAXS) pattern shown in Fig. 2c was obtained for a contaminated thin-film sample, this has now been replaced by the correct scattering pattern; the related caption should read "c, PEDOT–Tos, being qualitatively different from the PEDOT–PSS samples, exhibits higher-order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.

References

  1. Chiang, C. K. et al. Electrical conductivity in doped polyacetylene. Phys. Rev. Lett. 39, 1098–1101 (1977).

    Article  CAS  Google Scholar 

  2. Lee, K. et al. Metallic transport in polyaniline. Nature 441, 65–68 (2006).

    Article  CAS  Google Scholar 

  3. Cao, Y., Treacy, G. M., Smith, P. & Heeger, A. J. Solution-cast films of polyaniline: Optical-quality transparent electrodes. Appl. Phys. Lett. 60, 2711–2713 (1992).

    Article  CAS  Google Scholar 

  4. Fleishman, L., Licciardello, D. C. & Anderson, P. W. Elementary excitations in the Fermi glass. Phys. Rev. Lett. 40, 1340–1343 (1978).

    Article  Google Scholar 

  5. Wang, S., Ha, M., Manno, M., Daniel Frisbie, C. & Leighton, C. Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors. Nature Commun. 3, 1210 (2012).

    Article  Google Scholar 

  6. Pomfret, S. J., Adams, P. N., Comfort, N. P. & Monkman, A. P. Inherently electrically conductive fibers wet spun from a sulfonic acid–doped polyaniline solution. Adv. Mater. 10, 1351–1353 (1998).

    Article  CAS  Google Scholar 

  7. Yamaura, M., Hagiwara, T. & Iwata, K. Enhancement of electrical conductivity of polypyrrole film by stretching: Counter ion effect. Synth. Met. 26, 209–225 (1988).

    Article  CAS  Google Scholar 

  8. Fabretto, M. et al. High conductivity PEDOT resulting from glycol/oxidant complex and glycol/polymer intercalation during vacuum vapour phase polymerisation. Polymer 52, 1725–1730 (2011).

    Article  CAS  Google Scholar 

  9. Badre, C., Marquant, L., Alsayed, A. M. & Hough, L. A. Highly conductive poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) films using 1-ethyl-3-methylimidazolium tetracyanoborate ionic liquid. Adv. Funct. Mater. 22, 2723–2727 (2012).

    Article  CAS  Google Scholar 

  10. Xia, Y., Sun, K. & Ouyang, J. Solution–processed metallic conducting polymer films as transparent electrode of optoelectronic devices. Adv. Mater. 24, 2436–2440 (2012).

    Article  CAS  Google Scholar 

  11. Fabretto, M. V. et al. Polymeric material with metal-like conductivity for next generation organic electronic devices. Chem. Mater. 24, 3998–4003 (2012).

    Article  CAS  Google Scholar 

  12. Bubnova, O. et al. Optimization of the thermoelectric figure of merit in the conducting polymer poly(3,4-ethylenedioxythiophene). Nature Mater. 10, 429–433 (2011).

    Article  CAS  Google Scholar 

  13. Kim, G. H., Shao, L., Zhang, K. & Pipe, K. P. Engineered doping of organic semiconductors for enhanced thermoelectric efficiency. Nature Mater. 12, 719–723 (2013).

    Article  CAS  Google Scholar 

  14. Park, T., Park, C., Kim, B., Shin, H. & Kim, E. Flexible PEDOT electrodes with large thermoelectric power factors to generate electricity by the touch of fingertips. Energy Environ. Sci. 6, 788–792 (2013).

    Article  CAS  Google Scholar 

  15. Bed Poudel, Q. H. et al. High-thermoelectric performance of nanostructured bismuth antimony telluride bulk alloys. Science 320, 634–638 (2008).

    Article  Google Scholar 

  16. Ando, K., Watanabe, S., Mooser, S., Saitoh, E. & Sirringhaus, H. Solution–processed organic spin–charge converter. Nature Mater. 12, 622–627 (2013).

    Article  CAS  Google Scholar 

  17. Jeuris, K., Groenendaal, L., Verheyen, H., Louwet, F. & De Schryver, F. C. Light stability of 3,4-ethylenedioxythiophene-based derivatives. Synth. Met. 132, 289–295 (2003).

    Article  CAS  Google Scholar 

  18. Cornil, J., Beljonne, D. & Bredas, J. L. Nature of optical transitions in conjugated oligomers. I. Theoretical characterization of neutral and doped oligo(phenylenevinylene)s. J. Chem. Phys. 103, 834 (1995).

    Article  CAS  Google Scholar 

  19. Brédas, J. L., Wudl, F. & Heeger, A. J. Polarons and bipolarons in doped polythiophene: A theoretical investigation. Solid State Commun. 63, 577–580 (1987).

    Article  Google Scholar 

  20. Devreux, F., Genoud, F., Nechtschein, M. & Villeret, B. ESR investigation of polarons and bipolarons in conducting polymers: The case of polypyrrole. Synth. Met. 18, 89–94 (1987).

    Article  CAS  Google Scholar 

  21. Martin, D. C. et al. The morphology of poly(3,4-ethylenedioxythiophene). Polym. Rev. 50, 340–384 (2010).

    Article  CAS  Google Scholar 

  22. Stafström, S. & Brédas, J. L. Evolution of the electronic structure of polyacetylene and polythiophene as a function of doping level and lattice conformation. Phys. Rev. B 38, 4180–4191 (1988).

    Article  Google Scholar 

  23. Prigodin, V. N. & Efetov, K. B. Localization transition in a random network of metallic wires: A model for highly conducting polymers. Phys. Rev. Lett. 70, 2932–2935 (1993).

    Article  CAS  Google Scholar 

  24. Lavarda, F. C., dos Santos, M. C., Galvão, D. S. & Laks, B. Insulator-to-metal transition in polythiophene. Phys. Rev. B 49, 979–983 (1994).

    Article  CAS  Google Scholar 

  25. Sariciftci, N. S., Heeger, A. J. & Cao, Y. Paramagnetic susceptibility of highly conducting polyaniline: Disordered metal with weak electron-electron interactions (Fermi glass). Phys. Rev. B 49, 5988–5992 (1994).

    Article  CAS  Google Scholar 

  26. Heeger, A. J. Semiconducting and metallic polymers: The fourth generation of polymeric materials (nobel lecture). Angew. Chem. Int. Ed. 40, 2591–2611 (2001).

    Article  CAS  Google Scholar 

  27. Koller, G. et al. Intra- and intermolecular band dispersion in an organic crystal. Science 317, 351–355 (2007).

    Article  CAS  Google Scholar 

  28. Beljonne, D. et al. Optical signature of delocalized polarons in conjugated polymers. Adv. Funct. Mater. 11, 229–234 (2001).

    Article  CAS  Google Scholar 

  29. Stafström, S. et al. Polaron lattice in highly conducting polyaniline: Theoretical and optical studies. Phys. Rev. Lett. 59, 1464–1467 (1987).

    Article  Google Scholar 

  30. Snyder, G. J. & Toberer, E. S. Complex thermoelectric materials. Nature Mater. 7, 105–114 (2008).

    Article  CAS  Google Scholar 

  31. Mateeva, N., Niculescu, H., Schlenoff, J. & Testardi, L. R. Correlation of Seebeck coefficient and electric conductivity in polyaniline and polypyrrole. J. Appl. Phys. 83, 3111–3117 (1998).

    Article  CAS  Google Scholar 

  32. Yoon, C. O. et al. Hopping transport in doped conducting polymers in the insulating regime near the metal-insulator boundary: Polypyrrole, polyaniline and polyalkylthiophenes. Synth. Met. 75, 229–239 (1995).

    Article  CAS  Google Scholar 

  33. Zykwinska, A., Domagala, W., Czardybon, A., Pilawa, B. & Lapkowski, M. In situ EPR spectroelectrochemical studies of paramagnetic centres in poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-butylenedioxythiophene) (PBuDOT) films. Chem. Phys. 292, 31–45 (2003).

    Article  CAS  Google Scholar 

  34. Zotti, G. et al. Electrochemical and XPS studies toward the role of monomeric and polymeric sulfonate counterions in the synthesis, composition, and properties of poly(3,4-ethylenedioxythiophene). Macromolecules 36, 3337–3344 (2003).

    Article  CAS  Google Scholar 

  35. Geskin, V. M. & Brédas, J-L. Polaron pair versus bipolaron on oligothiophene chains: A theoretical study of the singlet and triplet states. ChemPhysChem 4, 498–505 (2003).

    Article  CAS  Google Scholar 

  36. Crispin, X. et al. The origin of the high conductivity of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT–PSS) plastic electrodes. Chem. Mater. 18, 4354–4360 (2006).

    Article  CAS  Google Scholar 

  37. Jonsson, S. K. M. et al. The effects of solvents on the morphology and sheet resistance in poly (3,4-ethylenedioxythiophene)–polystyrenesulfonic acid (PEDOT–PSS) films. Synth. Met. 139, 1–10 (2003).

    Article  CAS  Google Scholar 

  38. Nardes, A. M., Janssen, R. A. J. & Kemerink, M. A morphological model for the solvent-enhanced conductivity of PEDOT:PSS thin films. Adv. Funct. Mater. 18, 865–871 (2008).

    Article  CAS  Google Scholar 

  39. Kim, B. H. L. N. et al. Role of interchain coupling in the metallic state of conducting polymers. Phys. Rev. Lett. 109, 106405 (2012).

    Article  Google Scholar 

  40. Winther-Jensen, B. & West, K. Vapor-phase polymerization of 3,4-ethylenedioxythiophene: A route to highly conducting polymer surface layers. Macromolecules 37, 4538–4543 (2004).

    Article  CAS  Google Scholar 

  41. Evans, D. et al. Structure-directed growth of high conductivity PEDOT from liquid-like oxidant layers during vacuum vapor phase polymerization. J. Mater. Chem. 22, 14889–14895 (2012).

    Article  CAS  Google Scholar 

  42. Winther-Jensen, B. et al. Order–disorder transitions in poly(3,4-ethylenedioxythiophene). Polymer 49, 481–497 (2008).

    Article  CAS  Google Scholar 

  43. Winther-Jensen, B. et al. High current density and drift velocity in templated conducting polymers. Org. Electron. 8, 796–800 (2007).

    Article  CAS  Google Scholar 

  44. Breiby, D. W., Samuelsen, E. J., Groenendaal, L. B. & Struth, B. Smectic structures in electrochemically prepared poly(3,4-ethylenedioxythiophene) films. J. Polym. Sci. B 41, 945–952 (2003).

    Article  CAS  Google Scholar 

  45. Aasmundtveit, K. E. et al. Structure of thin films of poly(3,4-ethylenedioxythiophene). Synth. Met. 101, 561–564 (1999).

    Article  CAS  Google Scholar 

  46. Domagala, W., Pilawa, B. & Lapkowski, M. Quantitative in-situ EPR spectroelectrochemical studies of doping processes in poly(3,4-alkylenedioxythiophene)s: Part 1: PEDOT. Electrochim. Acta 53, 4580–4590 (2008).

    Article  CAS  Google Scholar 

  47. Crispin, X. et al. Conductivity, morphology, interfacial chemistry, and stability of poly(3,4-ethylene dioxythiophene)–poly(styrene sulfonate): A photoelectron spectroscopy study. J. Polym. Sci. B 41, 2561–2583 (2003).

    Article  CAS  Google Scholar 

  48. Bubnova, O., Berggren, M. & Crispin, X. Tuning the thermoelectric properties of conducting polymers in an electrochemical transistor. J. Am. Chem. Soc. 134, 16456–16459 (2012).

    Article  CAS  Google Scholar 

  49. Cutler, M. & Mott, N. F. Observation of Anderson localization in an electron gas. Phys. Rev. 181, 1336–1340 (1969).

    Article  CAS  Google Scholar 

Download references

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.

Author information

Authors and Affiliations

Authors

Contributions

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.

Corresponding author

Correspondence to Xavier Crispin.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 932 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Bubnova, O., Khan, Z., Wang, H. et al. Semi-metallic polymers. Nature Mater 13, 190–194 (2014). https://doi.org/10.1038/nmat3824

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nmat3824

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing