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Drift-diffusion simulation of leakage currents in unintentionally doped organic semiconductors with non-uniform interfaces

  • Vilany Santana Pereira
  • Stefan Blawid
Article
  • 36 Downloads

Abstract

Organic electronic devices frequently employ intrinsic semiconductors as active layer. The choice of different materials for the charge injecting and extracting interfaces gives rise to a finite contact potential. Injection of holes against the built-in electrical field results in a diffusion-limited exponential current–voltage characteristic at low bias. Leakage currents, however, seek paths with preferable negative built-in voltages arising from non-uniform interface properties. Along such paths holes are spilled into the intrinsic layer from the charge extracting contact whose Fermi energy is pinned in the lower half of the semiconductor’s band gap. We show here that the drift movement of holes opposed by diffusion can lead to a sublinear increase in the injected current with voltage. Charge injection is assisted by a built-in electrical field, depending mainly on the dopant density and the potential barrier at the injecting contact. Variability of these important properties can arise unintentionally, e.g., due to ambient processing, and low bias currents can serve as simple monitor. As a model system, measured current voltage characteristics of ambient processed poly(3-hexylthiophene-2,5-diyl) (P3HT) films are compared to numeric simulations solving the coupled nonlinear Poisson and drift-diffusion differential equations illustrating the basic principle.

Keywords

Organic electronics Drift-diffusion simulation Parameter extraction Conducting polymers Ambient processing Variability Interfaces 

Notes

Acknowledgements

V.S. Pereira acknowledges the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). F.L. de Melo and C.M. Moraes are acknowledged for their help in sample and data preparation as part of their scientific initiation project.

References

  1. 1.
    Krebs, F.C.: Air stable polymer photovoltaics based on a process free from vacuum steps and fullerenes. Sol. Energy Mater. Sol. Cells 92(7), 715 (2008)CrossRefGoogle Scholar
  2. 2.
    Jørgensen, M., Norrman, K., Krebs, F.C.: Stability/degradation of polymer solar cells. Sol. Energy Mater. Sol. Cells 92(7), 686 (2008)CrossRefGoogle Scholar
  3. 3.
    Tanenbaum, D.M., Hermenau, M., Voroshazi, E., Lloyd, M.T., Galagan, Y., Zimmermann, B., Hösel, M., Dam, H.F., Jørgensen, M., Gevorgyan, S.A., Kudret, S., Maes, W., Lutsen, L., Vanderzande, D., Würfel, U., Andriessen, R., Rösch, R., Hoppe, H., Teran-Escobar, G., Lira-Cantu, M., Rivaton, A., Uzunoğlu, G.Y., Germack, D., Andreasen, B., Madsen, M.V., Norrman, K., Krebs, F.C.: The ISOS-3 inter-laboratory collaboration focused on the stability of a variety of organic photovoltaic devices. RSC Adv. 2(3), 882 (2012)CrossRefGoogle Scholar
  4. 4.
    Grossiord, N., Kroon, J.M., Andriessen, R., Blom, P.W.M.: Degradation mechanisms in organic photovoltaic devices. Org. Electron. 13(3), 432 (2012)CrossRefGoogle Scholar
  5. 5.
    Rösch, R., Tanenbaum, D.M., Jørgensen, M., Seeland, M., Bärenklau, M., Hermenau, M., Voroshazi, E., Lloyd, M.T., Galagan, Y., Zimmermann, B., Würfel, U., Hösel, M., Dam, H.F., Gevorgyan, S.A., Kudret, S., Maes, W., Lutsen, L., Vanderzande, D., Andriessen, R., Teran-Escobar, G., Lira-Cantu, M., Rivaton, A., Uzunoğlu, G.Y., Germack, D., Andreasen, B., Madsen, M.V., Norrman, K., Hoppe, H., Krebs, F.C.: Investigation of the degradation mechanisms of a variety of organic photovoltaic devices by combination of imaging techniques—the ISOS-3 inter-laboratory collaboration. Energy Environ. Sci. 5(4), 6521 (2012)CrossRefGoogle Scholar
  6. 6.
    Abdou, M., Orfino, F.P., Son, Y.: Interaction of oxygen with conjugated polymers: charge transfer complex formation with poly(3-alkylthiophenes). J. Am. Chem. Soc. 119(19), 4518 (1997)CrossRefGoogle Scholar
  7. 7.
    Guillaud, G., Simon, J., Germain, J.P.: Metallophthalocyanines: gas sensors, resistors and field effect transistors. Coord. Chem. Rev. 178–180, 1433 (1998)CrossRefGoogle Scholar
  8. 8.
    Hoshino, S., Yoshida, M., Uemura, S., Kodzasa, T., Takada, N., Kamata, T., Yase, K.: Influence of moisture on device characteristics of polythiophene-based field-effect transistors. J. Appl. Phys. 95(9), 5088 (2004)CrossRefGoogle Scholar
  9. 9.
    Nishi, T., Kanai, K., Ouchi, Y., Willis, M.R., Seki, K.: Oxygen effects on the interfacial electronic structure of titanyl phthalocyanine film: \(p\)-Type doping, band bending and Fermi level alignment. Chem. Phys. 325(1), 121 (2006)CrossRefGoogle Scholar
  10. 10.
    Seemann, A., Sauermann, T., Lungenschmied, C., Armbruster, O., Bauer, S., Egelhaaf, H.J., Hauch, J.: Reversible and irreversible degradation of organic solar cell performance by oxygen. Sol. Energy 85(6), 1238 (2011)CrossRefGoogle Scholar
  11. 11.
    Zhuo, J.M., Zhao, L.H., Png, R.Q., Wong, L.Y., Chia, P.J., Tang, J.C., Sivaramakrishnan, S., Zhou, M., Ou, E.C.W., Chua, S.J., Sim, W.S., Chua, L.L., Ho, P.K.H.: Direct spectroscopic evidence for a photodoping mechanism in polythiophene and poly(bithiophene-alt-thienothiophene) organic semiconductor thin films involving oxygen and sorbed moisture. Adv. Mater. 21(46), 4747 (2009)Google Scholar
  12. 12.
    Ficker, J., von Seggern, H., Rost, H., Fix, W., Clemens, W., McCulloch, I.: Influence of intensive light exposure on polymer field-effect transistors. Appl. Phys. Lett. 85(8), 1377 (2004)CrossRefGoogle Scholar
  13. 13.
    Yu, C.Y., Jen, T.H., Chen, S.A.: Traps in Regioregular Poly(3-hexylthiophene) and its Blend with [6,6]-Phenyl-C61-Butyric Acid Methyl Ester for Polymer Solar Cells. ACS Appl. Mater. Interfaces 5, 4086–4092 (2013)CrossRefGoogle Scholar
  14. 14.
    Kalb, W.L., Mattenberger, K., Batlogg, B.: Oxygen-related traps in pentacene thin films: energetic position and implications for transistor performance. Phys. Rev. B 78(3), 035334 (2008)CrossRefGoogle Scholar
  15. 15.
    Lüssem, B., Riede, M., Leo, K.: Doping of organic semiconductors. Phys. Status Sol. A 210(1), 9 (2012)CrossRefGoogle Scholar
  16. 16.
    Hwang, J., Amy, F., Kahn, A.: Spectroscopic study on sputtered PEDOT-PSS: role of surface PSS layer. Org. Electron. 7(5), 387 (2006)CrossRefGoogle Scholar
  17. 17.
    Nardes, A.M., Kemerink, M., de Kok, M.M., Vinken, E., Maturova, K., Janssen, R.A.J.: Conductivity, work function, and environmental stability of PEDOT:PSS thin films treated with sorbitol. Org. Electron. 9(5), 727 (2008)CrossRefGoogle Scholar
  18. 18.
    Moulé, A.J., Jung, M.C., Rochester, C.W., Tress, W., LaGrange, D., Jacobs, I.E., Li, J., Mauger, S.A., Rail, M.D., Lin, O., Bilsky, D.J., Qi, Y., Stroeve, P., Berben, L.A., Riede, M.: Mixed interlayers at the interface between PEDOT:PSS and conjugated polymers provide charge transport control. J. Mater. Chem. C 3(11), 2664 (2015)CrossRefGoogle Scholar
  19. 19.
    Fischer, J., Tress, W., Kleemann, H., Widmer, J., Leo, K., Riede, M.: Exploiting diffusion currents at Ohmic contacts for trap characterization in organic semiconductors. Org. Electron. 15(10), 2428 (2014)CrossRefGoogle Scholar
  20. 20.
    Wetzelaer, G.J.A.H., Blom, P.W.M.: Diffusion-driven currents in organic-semiconductor diodes. NPG Asia Mater. 6(7), e110 (2014)CrossRefGoogle Scholar
  21. 21.
  22. 22.
    Scheinert, S., Paasch, G.: Fabrication and analysis of polymer field-effect transistors. Phys. Status Sol. A 201(6), 1263 (2004)CrossRefGoogle Scholar
  23. 23.
    Schneider, M., Wagenpfahl, A., Deibel, C., Dyakonov, V., Schöll, A., Reinert, F.: Band bending at the P3HT/ITO interface studied by photoelectron spectroscopy. Org. Electron. 15(7), 1552 (2014)CrossRefGoogle Scholar
  24. 24.
    Röhr, J.A., Kirchartz, T., Nelson, J.: On the correct interpretation of the low voltage regime in intrinsic single-carrier devices. J. Phys. Condens. Matter 29(20), 205901 (2017)CrossRefGoogle Scholar
  25. 25.
    Lee, S., Paine, D.C., Gleason, K.K.: Heavily doped poly(3,4-ethylenedioxythiophene) thin films with high carrier mobility deposited using oxidative CVD: conductivity stability and carrier transport. Adv. Funct. Mater. 24(45), 7187 (2014)Google Scholar
  26. 26.
    Mark, P., Helfrich, W.: Space-charge-limited currents in organic crystals. J. Appl. Phys. 33(1), 205 (1962)CrossRefGoogle Scholar
  27. 27.
    de Bruyn, P., van Rest, A.H.P., Wetzelaer, G.A.H., de Leeuw, D.M., Blom, P.W.M.: Diffusion-limited current in organic metal-insulator-metal diodes. Phys. Rev. Lett. 111(18), 186801 (2013)CrossRefGoogle Scholar
  28. 28.
    Baldo, M.A., Forrest, S.R.: Interface-limited injection in amorphous organic semiconductors. Phys. Rev. B 64(8), 7507 (2001)CrossRefGoogle Scholar
  29. 29.
    Jain, S.C., Geens, W., Mehra, A., Kumar, V., Aernouts, T., Poortmans, J., Mertens, R., Willander, M.: Injection- and space charge limited-currents in doped conducting organic materials. J. Appl. Phys. 89(7), 3804 (2001)CrossRefGoogle Scholar
  30. 30.
    Liang, Z., Nardes, A., Wang, D., Berry, J.J., Gregg, B.A.: Defect engineering in \(\pi \)-conjugated polymers. Chem. Mater. 21(20), 4914 (2009)CrossRefGoogle Scholar
  31. 31.
    Wang, P., Tanaka, D., Ryuzaki, S., Araki, S., Okamoto, K., Tamada, K.: Silver nanoparticles with tunable work functions. Appl. Phys. Lett. 107(15), 151601 (2015)CrossRefGoogle Scholar
  32. 32.
    Helander, M.G., Greiner, M.T., Wang, Z.B., Tang, W.M., Lu, Z.H.: Work function of fluorine doped tin oxide. J. Vac. Sci. Technol. A 29(1), 011019 (2011)CrossRefGoogle Scholar
  33. 33.
    Chiguvare, Z., Parisi, J., Dyakonov, V.: Influence of thermal annealing on the electrical properties of poly(3-hexylthiophene)-based thin film diodes. Z. für Naturforschung A 62(10–11), 609 (2007)Google Scholar
  34. 34.
    Kang, B., Lee, W.H., Cho, K.: Recent advances in organic transistor printing processes. ACS Appl. Mater. Interfaces 5(7), 2302 (2013)CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Electrical EngineeringUniversidade de BrasíliaBrasíliaBrazil

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