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Charge Transport in Reactive Mesogens and Liquid Crystal Polymer Networks

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Book cover Liquid Crystalline Semiconductors

Part of the book series: Springer Series in Materials Science ((SSMATERIALS,volume 169))

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Abstract

Understanding the mechanisms of charge transport in organic semiconductor electronic devices is paramount to optimising performance. This chapter aims to provide an insight into methods of measuring and analysing charge transport with specific focus on cross-linkable systems, i.e., reactive mesogens (RMs) and liquid crystalline (LC) polymer networks. When cross-linked in a mesophase, RMs form solid layers which preserve the mesophase charge transport properties over extended temperature ranges. In contrast, liquid crystalline polymer networks form solid layers but continue to undergo thermotropic transitions as in the original system and carrier mobilities can be enhanced compared to the liquid crystal. Here we examine how the versatility of these compounds brings about such complex behaviour. We see that chemical factors such as reactive end groups and method of cross-linking affect the hole and electron transport characteristics separately and that physical changes in morphology and phase also significantly change the charge transport properties.

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Notes

  1. 1.

    Depending on the system and especially in liquid crystalline materials the dimensionality of the carrier motion can be suppressed. For instance charge carriers travelling within an individual smectic layer can be viewed as travelling in two dimensions only because of the anisotropy of transport within a layer as opposed to between layers [35]. Similarly one may model carriers moving in columnar mesophases as moving in one dimension only.

  2. 2.

    This is in contrast to inorganic FETs where the type of mobile carrier is determined by the dopant.

References

  1. Adam, D., et al.: Fast photoconduction in the highly ordered columnar phase of a discotic liquid crystal. Nature 371, 141–143 (1994)

    Article  ADS  Google Scholar 

  2. Funahashi, M., Hanna, J.: High ambipolar carrier mobility in self-organizing terthiophene derivative. Appl. Phys. Lett. 76, 2574 (2000)

    Article  ADS  Google Scholar 

  3. Bushby, R.J., Lozman, O.R.: Photoconducting liquid crystals. Curr. Opin. Solid State Mater. Sci. 6(6), 569–578 (2002)

    Article  ADS  Google Scholar 

  4. Takayashiki, Y., et al.: Ambipolar carrier transport in terphenyl derivative. Mol. Cryst. Liq. Cryst. 480, 295–301 (2008)

    Article  Google Scholar 

  5. Funahashi, M., Hanna, J.I.: High carrier mobility up to 0.1 cm(2)V(−1)s(−1) at ambient temperatures in thiophene-based smectic liquid crystals. Adv. Mater. 17(5), 594 (2005)

    Article  Google Scholar 

  6. Maeda, H., Funahashi, M., Hanna, J.I.: Electrical properties of domain boundary in photoconductive smectic mesophases and their crystal phases. Mol. Cryst. Liq. Cryst. 366, 2221–2228 (2001)

    Google Scholar 

  7. Donovan, K.J., Kreouzis, T., Boden, N., Clements, J.: One dimensional carrier trapping in the crystalline phase of a columnar liquid crystal. J. Chem. Phys. 109(23), 10400–10408 (1998)

    Article  ADS  Google Scholar 

  8. Grell, M., Redecker, M., Whitehead, K.S., Bradley, D.D.C., Inbasekaran, M., Woo, E.P., Wu, W.: Monodomain alignment of thermotropic fluorene copolymers. Liq. Cryst. 26(9), 1403–1407 (1999)

    Article  Google Scholar 

  9. Cho, S., Seo, J.H., Park, S.H., Beaupre´, S., Leclerc, M., Heeger, A.J.: A thermally stable semiconducting polymer. Adv. Mater. 22, 1253–1257 (2010)

    Article  Google Scholar 

  10. Kreouzis, T., Scott, K., Donovan, K.J., Boden, N., Bushby, R.J., Lozman, O.R., Liu, Q.: Enhanced electronic transport properties in complementary binary discotic liquid crystal systems. Chem. Phys. 262(2–3), 489–497 (2000)

    Article  Google Scholar 

  11. Vlachos, P., et al.: Charge-transport in crystalline organic semiconductors with liquid crystalline order. Chem. Commun. 23, 2921–2923 (2005)

    Article  MathSciNet  Google Scholar 

  12. Bacher, A., et al.: Synthesis and characterisation of a conjugated reactive mesogen. J. Mater. Chem. 9(12), 2985–2989 (1999)

    Article  Google Scholar 

  13. Bacher, A., et al.: Conjugated reactive mesogens. Synth. Met. 111, 413–415 (2000)

    Article  Google Scholar 

  14. Bleyl, I., et al.: Photopolymerization and transport properties of liquid crystalline triphenylenes. Mol. Cryst. Liq. Cryst. Sci. Technol. Section A Mol. Cryst. Liq. Cryst. 299, 149–155 (1997)

    Article  Google Scholar 

  15. Kastler, M., et al.: Nanostructuring with a crosslinkable discotic material. Small 3(8), 1438–1444 (2007)

    Article  Google Scholar 

  16. Broer, D.J., Lub, J., Mol, G.N.: Wide-band reflective polarisers from cholesteric polymer networks with a pitch gradient. Nature 378, 467–469 (1995)

    Article  ADS  Google Scholar 

  17. Kreouzis, T., et al.: High mobility ambipolar charge transport in a cross-linked reactive mesogen at room temperature. Appl. Phys. Lett. 87(17), 172110 (2005)

    Article  ADS  Google Scholar 

  18. Wilderbeek, H.T.A., et al.: Photoinitiated bulk polymerization of liquid crystalline thiolene monomers. Macromolecules 35(24), 8962–8968 (2002)

    Article  ADS  Google Scholar 

  19. Thiem, H., et al.: Photopolymerization of reactive mesogens. Macromol. Chem. Phys. 206(21), 2153–2159 (2005)

    Article  Google Scholar 

  20. O’Neill, M., Kelly, S.M.: Liquid crystals for charge transport, luminescence, and photonics. Adv. Mater. 15(14), 1135–1146 (2003)

    Article  Google Scholar 

  21. Yoshimoto, N., Hanna, J.: A novel charge transport material fabricated using a liquid crystalline semiconductor and crosslinked polymer. Adv. Mater. 14(13–14), 988–991 (2002)

    Google Scholar 

  22. Yoshimoto, N., Funahashi, M., Hanna, J.: Charge transport in liquid crystalline semiconductor and crosslinked polymer composite. Mol. Cryst. Liq. Cryst. 409, 493–504 (2004)

    Article  Google Scholar 

  23. Prasad, S.K., et al.: Polymer network as a template for control of photoconductivity of a liquid crystal semiconductor. Liq. Cryst. 31(9), 1265–1270 (2004)

    Article  Google Scholar 

  24. Mizoshita, N., et al.: Smectic liquid-crystalline physical gels. Anisotropic self-aggregation of hydrogen-bonded molecules in layered structures. Chem. Commun. 9, 781–782 (1999)

    Article  Google Scholar 

  25. Mizoshita, N., et al.: The positive effect on hole transport behaviour in anisotropic gels consisting of discotic liquid crystals and hydrogen-bonded fibres. Chem. Commun. 5, 428–429 (2002)

    Article  Google Scholar 

  26. Hirai, Y., et al.: Enhanced hole-transporting behavior of discotic liquid-crystalline physical gels. Adv. Funct. Mater. 18(11), 1668–1675 (2008)

    Article  Google Scholar 

  27. Bässler, H.: Charge transport in disordered organic photoconductors, a Monte Carlo simulation study. Phys. Status Solidi (b) 175(1), 15–56 (1993)

    Article  ADS  Google Scholar 

  28. Novikov, S., Dunlap, D., Kenkre, V., Parris, P., Vannikov, A.: Essential role of correlations in governing charge transport in disordered organic materials. Phys. Rev. Lett. 81, 4472–4475 (1998)

    Article  ADS  Google Scholar 

  29. Goto, M., Takezoe, H., Ishikawa, K.: Carrier transport simulation of anomalous temperature dependence in nematic liquid crystals. Phys. Rev. E 76(4), 200710 (2007)

    Article  Google Scholar 

  30. Holstein, T.: Studies of polaron motion, parts I, II, III. Mol. Cryst. Model Ann. Phys. 8(3), 325–342 (November 1959)

    ADS  MATH  Google Scholar 

  31. Kreouzis, T., et al.: Temperature-independent hole mobility in discotic liquid crystals. J. Chem. Phys. 114(4), 1797–1802 (2001)

    Article  ADS  Google Scholar 

  32. Parris, P.E., Kenkre, V.M., Dunlap, D.H.: Nature of charge carriers in disordered molecular solids: are polarons compatible with observations? Phys. Rev. Lett. 87(12), 126601 (2001)

    Google Scholar 

  33. Lever, L.J., Kelsall, R.W., Bushby, R.J.: Band transport model for discotic liquid crystals. Phys. Rev. B 72(3), 35130 (2005)

    Article  ADS  Google Scholar 

  34. Farrar, S.R., et al.: Nondispersive hole transport of liquid crystalline glasses and a cross-linked network for organic electroluminescence. Phys. Rev. B 66(12), 5 (2002)

    Article  Google Scholar 

  35. Ohno, A., Hanna, J.: Simulated carrier transport in smectic mesophase and its comparison with experimental result. Appl. Phys. Lett. 82(5), 751–753 (2003)

    Article  ADS  Google Scholar 

  36. Kawamoto, M., et al.: Charge carrier transport properties in polymer liquid crystals containing oxadiazole and amine moieties in the same side chain. J. Phys. Chem. B 109(19), 9226–9230 (2005)

    Article  Google Scholar 

  37. Iino, H., et al.: Hopping conduction in the columnar liquid crystal phase of a dipolar discogen. J. Appl. Phys. 100(4), 043716 (2006)

    Article  ADS  Google Scholar 

  38. Ohno, A., et al.: Charge-carrier transport in smectic mesophases of biphenyls. J. Appl. Phys. 102(8), 83711 (2007)

    Article  Google Scholar 

  39. Baldwin, R.J., et al.: A comprehensive study of the effect of reactive end groups on the charge carrier transport within polymerized and nonpolymerized liquid crystals. J. Appl. Phys. 101(2), 023713 (2007)

    Article  ADS  Google Scholar 

  40. Kepler, R.G.: Phys. Rev. 119(4), 1226 (1960)

    Article  ADS  Google Scholar 

  41. Sze, S.M.: Physics of Semiconductor Devices, 2nd edn. Wiley, New York (1981). ISBN ISBN-10, 0471056618

    Google Scholar 

  42. Many, A., Rakavi, G.: Theory of transient space-charge-limited currents in solids in the presence of trapping. Phys. Rev. 126, 1980–1988 (1962)

    Article  ADS  Google Scholar 

  43. Dicker, G., et al.: Electrodeless time-resolved microwave conductivity study of charge-carrier photogeneration in regioregular poly(3-hexylthiophene) thin films. Phys. Rev. B 70, 045203 (2004)

    Article  ADS  Google Scholar 

  44. Juška, G., et al.: Charge transport in π-conjugated polymers from extraction current transients. Phys. Rev. B 62, 016235 (2000)

    Article  Google Scholar 

  45. Lampert, M.A., Mark, P.: Current Injection in Solids. Academic, New York (1970)

    Google Scholar 

  46. Hertel, D., Bässler, H.: ChemPhysChem 9, 666–688 (2008)

    Article  Google Scholar 

  47. Bayerl, M.S., et al.: Crosslinkable hole-transport materials for preparation of multilayer organic light emitting devices by spin-coating. Macromol. Rapid Commun. 20(4), 224–228 (1999)

    Article  Google Scholar 

  48. Contoret, A.E.A., et al.: Photopolymerisable nematic liquid crystals for electroluminescent devices. Synth. Met. 14(4), 1629–1630 (2001)

    Article  Google Scholar 

  49. Contoret, A.E.A., et al.: The photopolymerization and cross-linking of electroluminescent liquid crystals containing methacrylate and diene photopolymerizable end groups for multilayer organic light-emitting diodes. Chem. Mater. 14(4), 1477–1487 (2002)

    Article  Google Scholar 

  50. Aldred, M.P., et al.: Light-emitting fluorene photoreactive liquid crystals for organic electroluminescence. Chem. Mater. 16(24), 4928–4936 (2004)

    Article  Google Scholar 

  51. Aldred, M.P., et al.: Linearly polarised organic light-emitting diodes (OLEDs), synthesis and characterisation of a novel hole-transporting photoalignment copolymer. J. Mater. Chem. 15(31), 3208–3213 (2005)

    Article  Google Scholar 

  52. Aldred, M.P., et al.: Organic electroluminescence using polymer networks from smectic liquid crystals. Liq. Cryst. 33(4), 459–467 (2006)

    Article  Google Scholar 

  53. Zacharias, P., et al.: New crosslinkable hole conductors for blue-phosphorescent organic light-emitting diodes. Angew. Chem. Int. Ed. 46(23), 4388–4392 (2007)

    Article  Google Scholar 

  54. Rehmann, N., et al.: Advanced device architecture for highly efficient organic light-emitting diodes with an orange-emitting crosslinkable iridium(III) complex. Adv. Mater. 20(1), 129 (2008)

    Article  Google Scholar 

  55. Liedtke, A., et al.: White-light OLEDs using liquid crystal polymer networks. Chem. Mater. 20(11), 3579–3586 (2008)

    Article  Google Scholar 

  56. Carrasco-Orozco, M., et al.: New photovoltaic concept, liquid-crystal solar cells using a nematic gel template. Adv. Mater. 18(13), 1754–1758 (2006)

    Article  Google Scholar 

  57. Carrasco-Orozco, M.A., et al.: Superlattices of organic/inorganic semiconductor nanostructures from liquid-crystal templates. Phys. Rev. B 75(3), 5 (2007)

    Article  Google Scholar 

  58. Tsoi, W.C., et al.: Distributed bilayer photovoltaics based on nematic liquid crystal polymer networks. Chem. Mater. 19(23), 5475–5484 (2007)

    Article  Google Scholar 

  59. Vlachos, P., et al.: Electron-transporting and photopolymerisable liquid crystals. Chem. Commun. 8, 874–875 (2002)

    Article  Google Scholar 

  60. Woon, K.L., et al.: Electronic charge transport in extended nematic liquid crystals. Chem. Mater. 18(9), 2311–2317 (2006)

    Article  Google Scholar 

  61. McCulloch, I., et al.: Designing solution-processable air-stable liquid crystalline crosslinkable semiconductors. Philos. Trans. R. Soc. Math. Phys. Eng. Sci. 364(1847), 2779–2787 (2006)

    Article  ADS  Google Scholar 

  62. McCulloch, I., et al.: Electrical properties of reactive liquid crystal semiconductors. Jpn. J. Appl. Phys. 47(1), 488–491 (2008)

    Article  ADS  Google Scholar 

  63. McCulloch, I., et al.: Polymerisable liquid crystalline organic semiconductors and their fabrication in organic field effect transistors. J. Mater. Chem. 13(10), 2436–2444 (2003)

    Article  Google Scholar 

  64. Yoshimoto, N., Hanna, J.I.: Preparation of a novel organic semiconductor composite consisting of a liquid crystalline semiconductor and crosslinked polymer and characterization of its charge carrier transport properties. J. Mater. Chem. 13(5), 1004–1010 (2003)

    Article  Google Scholar 

  65. Ahn, H., Ohno, A., Hanna, J.I.: Impurity effects on charge transport in various mesophases of smectic liquid crystals. J. Appl. Phys. 102, 093718 (2007)

    Article  ADS  Google Scholar 

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Authors and Affiliations

  1. School of Physics and Astronomy, Queen Mary University of London, C14 NS, London, UK

    T. Kreouzis & K. S. Whitehead

  2. New York University in London, 6 Bedford Square, WC1B 3RA, London, UK

    K. S. Whitehead

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  1. T. Kreouzis
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  2. K. S. Whitehead
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Correspondence to T. Kreouzis .

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Editors and Affiliations

  1. , Faculty of Mathematics and Physical Scie, University of Leeds, University Campus, Leeds, LS2 9JT, United Kingdom

    Richard J. Bushby

  2. , Chemistry, University of Hull, Cottingham Road, Hull, HU6 7RX, United Kingdom

    Stephen M. Kelly

  3. , Physics and Mathematics, University Hull, University Campus, Hull, HU6 7RX, United Kingdom

    Mary O'Neill

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Kreouzis, T., Whitehead, K.S. (2013). Charge Transport in Reactive Mesogens and Liquid Crystal Polymer Networks. In: Bushby, R., Kelly, S., O'Neill, M. (eds) Liquid Crystalline Semiconductors. Springer Series in Materials Science, vol 169. Springer, Dordrecht. https://doi.org/10.1007/978-90-481-2873-0_5

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