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Electron transport along molecular stacks in discotic liquid crystals

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Abstract

We have previously shown that a new class of quasi-one-dimensional p-type semiconductors can be created by dissolving small amounts of oxidising agents into the hydrocarbon chain matrix of discotic liquid crystals. This paper reports the elucidation of the mechanism of conduction in these new materials. In particular, the ac conductivity of 2,3,6,7,10,11 -hexahexyloxytriphenylene (HAT6) doped with the Lewis acid AlCl3, has been measured as a function of frequency (10−3–107 Hz), and temperature in its crystalline solid (K), hexagonal discotic liquid crystal (Dho) and isotropic liquid (I) phases. In macroscopically aligned K and Dho phases, the conductivity measured along the column axes is approximately 103 greater than that in the perpendicular direction. Both components of the conductivity are found to be independent of frequency at low frequencies, but show a power law dependence on frequency (Σ(Ω)∼Ωs, s∼0.8) at higher frequencies. This behaviour is characteristic of charge carrier transport by a hopping mechanism. The conductivity data have been analysed in terms of the Scher and Lax theory of hopping transport to obtain the parameters describing this process. The conduction along the columns is identified with a single charge transport process in which the carriers hop between localized states (radical cations) associated with counterions (perceived as AlCl4 −) linearly distributed off-axis along the columns.

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References

  1. I. A.Howard Semiconductors and Semimetals Vol. 27, Highly Conducting Quasi-One-Dimensional Organic Crystals, E. Conwell (ed), (Academic Press, London, 1988).

    Google Scholar 

  2. H.Schultz, H.Lehmann, M.Rein, and M.Hanack, Structure and Bonding, 74 (1991) 41; T. J. Marks, Angew. Chem. Int. Ed. Engl. 29 (1990) 857; A.-M. Giroudgodquin and P. M. Maitlis, ibid. Structure and Bonding 30 (1991) 375.

    Google Scholar 

  3. Handbook of Conducting polymers, edited by t. A. Skotheim, (Marcel Dekker, New York, 1986), volumes I and II.

  4. N.Boden, R. J.Bushby, J.Clements, M. V.Jesudason, P. F.Knowles, and G. Williams, Chem. Phys. Lett. 152 (1988) 94; ibid. 154 (1989) 613.

    Google Scholar 

  5. n. boden, r. j. bushby, and j. clements, J. Chem. Phys. in press.

  6. L. Y.Chiang, J. P.Stokes, C. R.Safinya, and A. N.Bloch, Mol. Cryst. Liq. Cryst. 125 (1985) 279.

    Google Scholar 

  7. J.vanKeulen, T. W.Warmerdam, R. J. M.Nolte, and W.Drenth, Recl. Trav. Chim. Pays-Bas. 106 (1987) 534.

    Google Scholar 

  8. G. B. M.Vaughan, P. A.Heiney, J. P.McCauley Jr., and A. B.Smith III. Phys. Rev. B46 (1992) 2787.

    Google Scholar 

  9. S.Chandrasekhar and G. S.Ranganath, Rep. Prog. Phys. 53 (1990) 57.

    Google Scholar 

  10. J.Simon and C.Sirlin, Pure Appl. Chem. 61, 1625 (1989); c. piechocki, j. simon, a. skoulios, d. guillon, and p. weber, J. Am. Chem. Soc. 104 (1982) 5245.

    Google Scholar 

  11. B. A.Gregg, M. A.Fox, and A. J.Bard, ibid.Pure Appl. Chem. 111 (1989) 3024; p. g. schouten, j. m. warman, m. p. de haas, m. a. fox, and h.-l. pan, Nature, 353 (1991) 736; s. gaspard, p. maillard, and j. billard, Mol. Cryst. Liq. Cryst. 123 (1985) 369.

    Google Scholar 

  12. V.Gionis, H.Strzelecka, M.Veber, R.Kormann and L.Zuppiroli, ibid.Pure Appl. Chem. 137 (1986) 365.

    Google Scholar 

  13. J. F.van DerPol, E.Neelman, J. W.Zwicker, R. J. M.Nolte, W.Drenth, J. Aerts, R.Visser, and S. J.Picken, Liq. Cryst. 6 (1989) 577.

    Google Scholar 

  14. Z.Belarbi, C.Sirlin, J.Simon, and J. J.Andre, J. Phys. Chem. 93 (1989) 8105.

    Google Scholar 

  15. N.Boden, R. C.Borner, D. R.Brown, R. J.Bushby, J.Clements, Liq. Cryst. 11 (1992) 325.

    Google Scholar 

  16. N.Boden, R. J.Bushby, L.Ferris, C.Hardy, and F.Sixl, ibidLiq. Cryst. 1 (1986) 109.

    Google Scholar 

  17. d. e. martire in The Molecular Physics of Liquid Crystals, g. r. luckhurst and g. w. gray (eds). (Academic Press, New York, 1987) p. 239.

  18. R. C.Borner, Ph. D. Thesis, Leeds University, Leeds. U. k. 1992.

    Google Scholar 

  19. D.Goldfarb, Z.Luz, and H.Zimmerman, J. Phys., 42 (1981) 1303.

    CAS  PubMed  Google Scholar 

  20. H.Bottger and V. V.Bryskin, Hopping Conduction in Solids (VCH, Berlin, 1985).

    Google Scholar 

  21. N. F.Mott and E. A.Davies, Electronic Processes in Non-Crystalline Materials (Clarendon Press, Oxford, 1979).

    Google Scholar 

  22. M.Pollak and T. H.Geballe, Phys. Rev. 122, (1961) 1742; m. abkowitz, d. f. blossey and a. i.lakatos ibid. Phys. Rev. B12 (1975) 3400.

    Google Scholar 

  23. A. J.Epstein, H.Rommelman, M.Abkowitz and H. W.Gibson, Mol. Cryst. Liq. Cryst. 77 (1981) 81.

    Google Scholar 

  24. J.Simon and J.-j.Andre, Molecular Semiconductors (Springer Verlag, Berlin, 1985).

    Google Scholar 

  25. N.Scher and M.Lax Phys. Rev. 7(1973) 4491; ibid 7 (1973) 4502.

    Google Scholar 

  26. M. A.Abkowitz, A.Lakatos, and H.Scher, ibid.Phys. Rev. B9 (1974) 1813; a. r. long Adv. Phys. 31 (1982) 553.

    Google Scholar 

  27. H.Kahnt and F.Schirrmeister, J. Non-Cryst. Solids, 90 (1987) 421.

    Google Scholar 

  28. D.Adam, F.Closs, T.Frey, D.Funhoff, D.Haarer, H.Ringsdorf, P. Schuhmacher, and K.Siemensmeyer, Phys. Rev. Lett. 70 (1993) 457.

    Google Scholar 

  29. L. B.Schein and D. W.Brown, Mol. Cryst. Liq. Cryst. 87 (1982) 1.

    Google Scholar 

  30. J. H.Sluyters, A.Baars, J. F.van DerPol, and W.Drenth, J. Electroanal. Chem. 271 (1989) 41.

    Google Scholar 

  31. n. boden, r. c. borner, r. j. bushby, and j. clements, in preparation.

  32. R.Kariotis and M. J.Stephen, Phys. Lett., 93A (1983) 349.

    Google Scholar 

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Authors and Affiliations

  1. The Centre for Self-Organising Molecular Systems, The University of Leeds, LS2 9JT, Leeds, UK

    N. Boden, R. J. Bushby & J. Clements

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  1. N. Boden
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  2. R. J. Bushby
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  3. J. Clements
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Boden, N., Bushby, R.J. & Clements, J. Electron transport along molecular stacks in discotic liquid crystals. J Mater Sci: Mater Electron 5, 83–88 (1994). https://doi.org/10.1007/BF00187117

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