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Unification of trap-limited electron transport in semiconducting polymers

Nature Materials volume 11, pages 882–887 (2012)Cite this article

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Abstract

Electron transport in semiconducting polymers is usually inferior to hole transport, which is ascribed to charge trapping on isolated defect sites situated within the energy bandgap. However, a general understanding of the origin of these omnipresent charge traps, as well as their energetic position, distribution and concentration, is lacking. Here we investigate electron transport in a wide range of semiconducting polymers by current–voltage measurements of single-carrier devices. We observe for this materials class that electron transport is limited by traps that exhibit a Gaussian energy distribution in the bandgap. Remarkably, the electron-trap distribution is identical for all polymers considered: the number of traps amounts to 3 × 1023 traps per m3 centred at an energy of ~3.6 eV below the vacuum level, with a typical distribution width of ~0.1 eV. This indicates that the electron traps have a common origin that, we suggest, is most likely related to hydrated oxygen complexes. A consequence of this finding is that the trap-limited electron current can be predicted for any polymer.

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Figure 1: Comparison of electron and hole current.
Figure 2: Electron transport in different polymers.
Figure 3: Schematic representation of the energies of the LUMO and the centre of the trap distribution.
Figure 4: The influence of water complexation on the electron affinity of PPV was studied for three oligomer conformations.
Figure 5

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References

  1. Friend, R. H. et al. Electroluminescence in conjugated polymers. Nature 397, 121–128 (1999).

    Article  CAS  Google Scholar 

  2. Brabec, C. J., Sariciftci, N. S. & Hummelen, J. C. Plastic solar cells. Adv. Funct. Mater. 11, 15–26 (2001).

    Article  CAS  Google Scholar 

  3. Blom, P. W. M. & Vissenberg, M. C. J. M. Charge transport in poly(p-phenylene vinylene) light-emitting diodes. Mater. Sci. Eng.: R 27, 53–94 (2000).

    Article  Google Scholar 

  4. Tanase, C., Meijer, E. J., Blom, P. W. M. & de Leeuw, D. M. Unification of the hole transport in polymeric field-effect transistors and light-emitting diodes. Phys. Rev. Lett. 91, 216601 (2003).

    Article  CAS  Google Scholar 

  5. Pasveer, W. F. et al. Unified description of charge-carrier mobilities in disordered semiconducting polymers. Phys. Rev. Lett. 94, 206601 (2005).

    Article  CAS  Google Scholar 

  6. Brédas, J. L., Calbert, J. P., Da Silva Filho, D. A. & Cornil, J. Organic semiconductors: A theoretical characterization of the basic parameters governing charge transport. Proc. Natl Acad. Sci. USA 99, 5804–5809 (2002).

    Article  Google Scholar 

  7. Blom, P. W. M., de Jong, M. J. M & Vleggaar, J. J. M. Electron and hole transport in poly(p-phenylene vinylene) devices. Appl. Phys. Lett. 68, 3308–3310 (1996).

    Article  CAS  Google Scholar 

  8. Mandoc, M. M., de Boer, B., Paasch, G. & Blom, P. W. M. Trap-limited electron transport in disordered semiconducting polymers. Phys. Rev. B 75, 193202 (2007).

    Article  Google Scholar 

  9. Graupner, W., Leditzky, G., Leising, G. & Scherf, U. Shallow and deep traps in conjugated polymers of high intrachain order. Phys. Rev. B 54, 7610–7613 (1996).

    Article  CAS  Google Scholar 

  10. Meier, M., Karg, S., Zuleeg, K., Brütting, W. & Schwoerer, M. Determination of trapping parameters in poly(p-phenylenevinylene) light-emitting devices using thermally stimulated currents. J. Appl. Phys. 84, 87–92 (1998).

    Article  CAS  Google Scholar 

  11. Kuik, M. et al. Determination of the trap-assisted recombination strength in polymer light emitting diodes. Appl. Phys. Lett. 98, 093301 (2011).

    Article  Google Scholar 

  12. Wetzelaer, G. A. H., Kuik, M., Nicolai, H. T. & Blom, P. W. M. Trap-assisted and Langevin-type recombination in organic light-emitting diodes. Phys. Rev. B 83, 165204 (2011).

    Article  Google Scholar 

  13. Kuik, M., Koster, L. J. A., Wetzelaer, G. A. H. & Blom, P. W. M. Trap-assisted recombination in disordered organic semiconductors. Phys. Rev. Lett. 107, 256805 (2011).

    Article  CAS  Google Scholar 

  14. Nicolai, H. T., Mandoc, M. M. & Blom, P. W. M. Electron traps in semiconducting polymers: Exponential versus Gaussian trap distribution. Phys. Rev. B 83, 195204 (2011).

    Article  Google Scholar 

  15. Zhang, Y., de Boer, B. & Blom, P. W. M. Trap-free electron transport in poly(p -phenylene vinylene) by deactivation of traps with n-type doping. Phys. Rev. B 81, 085201 (2010).

    Article  Google Scholar 

  16. Chua, L-L. et al. General observation of n-type field-effect behaviour in organic semiconductors. Nature 434, 194–199 (2005).

    Article  CAS  Google Scholar 

  17. Nicolai, H. T. et al. Space-charge-limited hole current in poly(9,9-dioctylfluorene) diodes. Appl. Phys. Lett. 96, 172107 (2010).

    Article  Google Scholar 

  18. Tanase, C., Blom, P. W. M., de Leeuw, D. M. & Meijer, E. J. Charge carrier density dependence of the hole mobility in poly(p-phenylene vinylene). Phys. Status Solidi A 201, 1236–1245 (2004).

    Article  CAS  Google Scholar 

  19. Kuik, M. et al. Optical detection of deep electron traps in poly(p-phenylene vinylene) light-emitting diodes. Appl. Phys. Lett. 99, 183305 (2011).

    Article  Google Scholar 

  20. Fung, M. K. et al. Role of ytterbium and ytterbium/cesium fluoride on the chemistry of poly(9,9-dioctylfluorene-co-benzothiadiazole) as investigated by photoemission spectroscopy. J. Appl. Phys. 94, 2686–2694 (2003).

    Article  CAS  Google Scholar 

  21. Gwinner, M. C. et al. Solution-processed zinc oxide as high-performance air-stable electron injector in organic ambipolar light-emitting field-effect transistors. Adv. Funct. Mater. 20, 3457–3465 (2010).

    Article  CAS  Google Scholar 

  22. Mühlbacher, D. et al. High photovoltaic performance of a low-bandgap polymer. Adv. Mater. 18, 2884–2889 (2006).

    Article  Google Scholar 

  23. Aygül, U. et al. Electronic properties of interfaces between PCPDTBT and prototypical electrodes studied by photoemission spectroscopy. ChemPhysChem 12, 2345–2351 (2011).

    Article  Google Scholar 

  24. Al-Ibrahim, M. et al. Phenylene-ethynylene/phenylene-vinylene hybrid polymers: Optical and electrochemical characterization, comparison with poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene] and application in flexible polymer solar cells. Thin Solid Films 474, 201–210 (2005).

    Article  CAS  Google Scholar 

  25. Guan, Z-L. et al. Direct determination of the electronic structure of the poly(3-hexylthiophene):phenyl-[6,6]-C61 butyric acid methyl ester blend. Org. Electron. 11, 1779–1785 (2010).

    Article  CAS  Google Scholar 

  26. Thakur, A. K., Mukherjee, A. K., Preethichandra, D. M. G., Takashima, W. & Kaneto, K. Charge injection mechanism across the Au-poly(3-hexylthiophene-2,5-diyl) interface. J. Appl. Phys. 101, 104508 (2007).

    Article  Google Scholar 

  27. Lee, J. U., Kim, Y. D., Jo, J. W., Kim, J. P. & Jo, W. H. Efficiency enhancement of P3HT/PCBM bulk heterojunction solar cells by attaching zinc phthalocyanine to the chain-end of P3HT. J. Mater. Chem. 21, 17209–17218.

  28. Sirringhaus, H. et al. Two-dimensional charge transport in self-organized, high-mobility conjugated polymers. Nature 401, 685–688 (1999).

    Article  CAS  Google Scholar 

  29. Tseng, H-E., Peng, K-Y. & Chen, S-A. Molecular oxygen and moisture as traps in poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]: Locations and detrapping by chain relaxation. Appl. Phys. Lett. 82, 4086–4088 (2003).

    Article  CAS  Google Scholar 

  30. Kažukauskas, V. Investigation of carrier transport and trapping by oxygen-related defects in MEH–PPV diodes. Semicond. Sci. Technol. 19, 1373–1380 (2004).

    Article  Google Scholar 

  31. De Leeuw, D. M., Simenon, M. M. J., Brown, A. R. & Einerhand, R. E. F. Stability of n-type doped conducting polymers and consequences for polymeric microelectronic devices. Synth. Met. 87, 53–59 (1997).

    Article  CAS  Google Scholar 

  32. Anthopoulos, T. D., Anyfantis, G. C., Papavassiliou, G. C. & de Leeuw, D. M. Air-stable ambipolar organic transistors. Appl. Phys. Lett. 90, 122105 (2007).

    Article  Google Scholar 

  33. Simmons, J. G. & Taylor, G. W. High-field isothermal currents and thermally stimulated currents in insulators having discrete trapping levels. Phys. Rev. B 5, 1619–1629 (1972).

    Article  Google Scholar 

  34. Lang, D. V. Deep-level transient spectroscopy: A new method to characterize traps in semiconductors. J. Appl. Phys. 45, 3023–3032 (1974).

    Article  CAS  Google Scholar 

  35. Werner, A. G., Blochwitz, J., Pfeiffer, M. & Leo, K. Field dependence of thermally stimulated currents in Alq3 . J. Appl. Phys. 90, 123–125 (2001).

    Article  CAS  Google Scholar 

  36. Steiger, J., Schmechel, R. & von Seggern, H. Energetic trap distributions in organic semiconductors. Synth. Met. 129, 1–7 (2002).

    Article  CAS  Google Scholar 

  37. Xing, K. et al. The interaction of poly (p-phenylenevinylene) with air. Adv. Mater. 8, 971–974 (1996).

    Article  CAS  Google Scholar 

  38. Sutherland, D. G. J. et al. Photo-oxidation of electroluminescent polymers studied by core-level photoabsorption spectroscopy. Appl. Phys. Lett. 68, 2046–2048 (1996).

    Article  CAS  Google Scholar 

  39. Xing, K. Z. et al. Photo-oxidation of poly(p-phenylenevinylene). Adv. Mater. 9, 1027–1031 (2004).

    Article  Google Scholar 

  40. Zhuo, J. et al. 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, 4747–4752 (2009).

    CAS  Google Scholar 

  41. Haynes, W. M. CRC Handbook of Chemistry and Physics (CRC, 2011).

    Google Scholar 

  42. Bell, A. J. & Wright, T. G. Structures and binding energies of O2–·H2O and O2·H2O. Phys. Chem. Chem. Phys. 6, 4385–4390 (2004).

    Article  CAS  Google Scholar 

  43. Gomes, J. A. G. et al. Experimental and theoretical study of the atmospherically important O2H2O complex. Spectrochim. Acta A 61, 3082–3086 (2005).

    Article  Google Scholar 

  44. Grimme, S. Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem. 27, 1787–1799 (2006).

    Article  CAS  Google Scholar 

  45. Klamt, A. & Schüürmann, G. COSMO: A new approach to dielectric screening in solvents with explicit expressions for the screening energy and its gradient. J. Chem. Soc. Perkin Trans. 2, 799–805 (1993).

    Article  Google Scholar 

  46. Andzelm, J., Kölmel, C. & Klamt, A. Incorporation of solvent effects into density functional calculations of molecular energies and geometries. J. Chem. Phys. 103, 9312–9320 (1995).

    Article  CAS  Google Scholar 

  47. Barone, V. & Cossi, M. Quantum calculation of molecular energies and energy gradients in solution by a conductor solvent model. J. Phys. Chem. A 102, 1995–2001 (1998).

    Article  CAS  Google Scholar 

  48. Cossi, M., Rega, N., Scalmani, G. & Barone, V. Energies, structures, and electronic properties of molecules in solution with the C-PCM solvation model. J. Comput. Chem. 24, 669–681 (2003).

    Article  CAS  Google Scholar 

  49. Frisch, M. J. et al. Gaussian 09, Revision A.02 (Gaussian, 2009).

    Google Scholar 

  50. Moet, D. J. D., de Bruyn, P. & Blom, P. W. M. High work function transparent middle electrode for organic tandem solar cells. Appl. Phys. Lett. 96, 153504 (2010).

    Article  Google Scholar 

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Acknowledgements

The authors thank M. Lenes, Y. Zhang, M. Mandoc and M. Lu for their contributions to this work and J. Harkema for technical support. The work at the University of Groningen was supported by the European Commission under contract FP7-13708 (AEVIOM). The work at Georgia Tech was supported by the MRSEC Program of the National Science Foundation under Award Number DMR-0819885.

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Authors and Affiliations

  1. Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands

    H. T. Nicolai, M. Kuik, G. A. H. Wetzelaer, B. de Boer & P. W. M. Blom

  2. School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA

    C. Campbell, C. Risko & J. L. Brédas

  3. TNO/Holst Centre, High Tech Campus 31, 5605 KN Eindhoven, The Netherlands

    P. W. M. Blom

  4. Department of Chemistry, King Abdulaziz University, Jeddah 21589, Saudi Arabia

    J. L. Brédas

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Contributions

P.W.M.B. and B.d.B. proposed and supervised the project. H.T.N., M.K. and G.A.H.W. carried out experiments. H.T.N. and M.K. analysed the electron transport data. J.L.B. supervised the quantum-chemical calculations. C.C. and C.R. carried out the quantum-chemical calculations and C.R. analysed the data. H.T.N., C.R. and J.L.B. wrote the manuscript.

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Correspondence to P. W. M. Blom.

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Nicolai, H., Kuik, M., Wetzelaer, G. et al. Unification of trap-limited electron transport in semiconducting polymers. Nature Mater 11, 882–887 (2012). https://doi.org/10.1038/nmat3384

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