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.

  • Letter
  • Published:

A window to trap-free charge transport in organic semiconducting thin films

Nature Materials volume 18, pages 1182–1186 (2019)Cite this article

Subjects

Abstract

Organic semiconductors, which serve as the active component in devices, such as solar cells, light-emitting diodes and field-effect transistors1, often exhibit highly unipolar charge transport, meaning that they predominantly conduct either electrons or holes. Here, we identify an energy window inside which organic semiconductors do not experience charge trapping for device-relevant thicknesses in the range of 100 to 300 nm, leading to trap-free charge transport of both carriers. When the ionization energy of a material surpasses 6 eV, hole trapping will limit the hole transport, whereas an electron affinity lower than 3.6 eV will give rise to trap-limited electron transport. When both energy levels are within this window, trap-free bipolar charge transport occurs. Based on simulations, water clusters are proposed to be the source of hole trapping. Organic semiconductors with energy levels situated within this energy window may lead to optoelectronic devices with enhanced performance. However, for blue-emitting light-emitting diodes, which require an energy gap of 3 eV, removing or disabling charge traps will remain a challenge.

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

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

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

Fig. 1: Energy window for trap-free charge transport.
Fig. 2: Hole transport in C60, PCBM and ICBA.
Fig. 3: Close-up view of a water-filled pocket in a simulated C60 morphology.
Fig. 4: Calculated densities of states of water clusters in four organic films.

Similar content being viewed by others

Data availability

Experimental data are available from the corresponding author upon reasonable request.

References

  1. Coropceanu, V. et al. Charge transport in organic semiconductors. Chem. Rev. 107, 926–952 (2007).

    Article  CAS  Google Scholar 

  2. Tang, M. L., Reichardt, A. D., Wei, P. & Bao, Z. Correlating carrier type with frontier molecular orbital energy levels in organic thin film transistors of functionalized acene derivatives. J. Am. Chem. Soc. 131, 5264–5273 (2009).

    Article  CAS  Google Scholar 

  3. 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 

  4. Nicolai, H. T. et al. Unification of trap-limited electron transport in semiconducting polymers. Nat. Mater. 11, 882–887 (2012).

    Article  CAS  Google Scholar 

  5. Kotadiya, N. B. et al. Universal strategy for ohmic hole injection into organic semiconductors with high ionization energies. Nat. Mater. 17, 329–334 (2018).

    Article  CAS  Google Scholar 

  6. Mott, S. N. F. & Gurney, R. W. Electronic Processes in Ionic Crystals 2nd edn (Clarendon Press, 1948).

  7. Mark, P. & Helfrich, W. Space‐charge‐limited currents in organic crystals. J. Appl. Phys. 33, 205–215 (1962).

    Article  CAS  Google Scholar 

  8. Kotadiya, N. B., Blom, P. W. M. & Wetzelaer, G. A. H. Trap-free space-charge-limited hole transport in a fullerene derivative. Phys. Rev. Appl. 11, 024069 (2019).

    Article  CAS  Google Scholar 

  9. Wetzelaer, G.-J. A. H. et al. Asymmetric electron and hole transport in a high-mobility n-type conjugated polymer. Phys. Rev. B 86, 165203 (2012).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  11. Wetzelaer, G. A. H. & Blom, P. W. M. Ohmic current in organic metal-insulator-metal diodes revisited. Phys. Rev. B 89, 241201 (2014).

    Article  CAS  Google Scholar 

  12. 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 

  13. Rohloff, R., Kotadiya, N. B., Crăciun, N. I., Blom, P. W. M. & Wetzelaer, G. A. H. Electron and hole transport in the organic small molecule α-NPD. Appl. Phys. Lett. 110, 073301 (2017).

    Article  CAS  Google Scholar 

  14. Kotadiya, N. B. et al. Rigorous characterization and predictive modeling of hole transport in amorphous organic semiconductors. Adv. Electron. Mater. 4, 1800366 (2018).

    Article  CAS  Google Scholar 

  15. Karki, A. et al. Unifying energetic disorder from charge transport and band bending in organic semiconductors. Adv. Funct. Mater. 29, 1901109 (2019).

    Article  CAS  Google Scholar 

  16. Vissenberg, M. C. J. M. & Blom, P. W. M. Transient hole transport in poly(-p-phenylene vinylene) LEDs. Synth. Met. 102, 1053–1054 (1999).

    Article  CAS  Google Scholar 

  17. Torabi, S. et al. Strategy for enhancing the dielectric constant of organic semiconductors without sacrificing charge carrier mobility and solubility. Adv. Funct. Mater. 25, 150–157 (2015).

    Article  CAS  Google Scholar 

  18. Seemann, A. et al. Reversible and irreversible degradation of organic solar cell performance by oxygen. Solar Energy 85, 1238–1249 (2011).

    Article  CAS  Google Scholar 

  19. Nayak, P. K., Rosenberg, R., Barnea-Nehoshtan, L. & Cahen, D. O2 and organic semiconductors: electronic effects. Org. Electron. 14, 966–972 (2013).

    Article  CAS  Google Scholar 

  20. Zhuo, J.-M. 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 

  21. Nikolka, M. et al. High operational and environmental stability of high-mobility conjugated polymer field-effect transistors through the use of molecular additives. Nat. Mater. 16, 356–362 (2017).

    Article  CAS  Google Scholar 

  22. Zuo, G., Linares, M., Upreti, T. & Kemerink, M. General rule for the energy of water-induced traps in organic semiconductors. Nat. Mater. 18, 588–593 (2019).

  23. Page, R. H., Larkin, R. J., Shen, Y. R. & Lee, Y. T. High‐resolution photoionization spectrum of water molecules in a supersonic beam. J. Chem. Phys. 88, 2249–2263 (1988).

    Article  CAS  Google Scholar 

  24. Tonkyn, R. G., Winniczek, J. W. & White, M. G. Rotationally resolved photoionization of O2+ near threshold. Chem. Phys. Lett. 164, 137–142 (1989).

    Article  CAS  Google Scholar 

  25. 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  Google Scholar 

  26. 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 

  27. Uoyama, H., Goushi, K., Shizu, K., Nomura, H. & Adachi, C. Highly efficient organic light-emitting diodes from delayed fluorescence. Nature 492, 234–238 (2012).

    Article  CAS  Google Scholar 

  28. Jorgensen, W. L. & Tirado-Rives, J. The OPLS [optimized potentials for liquid simulations] potential functions for proteins, energy minimizations for crystals of cyclic peptides and crambin. J. Am. Chem. Soc. 110, 1657–1666 (1988).

    Article  CAS  Google Scholar 

  29. Jorgensen, W. L., Maxwell, D. S. & Tirado-Rives, J. Development and testing of the OPLS all-atom force field on conformational energetics and properties of organic liquids. J. Am. Chem. Soc. 118, 11225–11236 (1996).

    Article  CAS  Google Scholar 

  30. Jorgensen, W. L. & Tirado-Rives, J. Potential energy functions for atomic-level simulations of water and organic and biomolecular systems. Proc. Natl Acad. Sci. USA 102, 6665–6670 (2005).

    Article  CAS  Google Scholar 

  31. McDonald, N. A. & Jorgensen, W. L. Development of an all-atom force field for heterocycles. Properties of liquid pyrrole, furan, diazoles, and oxazoles. J. Phys. Chem. B 102, 8049–8059 (1998).

    Article  CAS  Google Scholar 

  32. Poelking, C. et al. Characterization of charge-carrier transport in semicrystalline polymers: electronic couplings, site energies, and charge-carrier dynamics in poly(bithiophene-alt-thienothiophene) [PBTTT]. J. Phys. Chem. C 117, 1633–1640 (2013).

    Article  CAS  Google Scholar 

  33. Poelking, C. & Andrienko, D. Effect of polymorphism, regioregularity and paracrystallinity on charge transport in poly(3-hexyl-thiophene) [P3HT] nanofibers. Macromolecules 46, 8941–8956 (2013).

    Article  CAS  Google Scholar 

  34. Breneman, C. M. & Wiberg, K. B. Determining atom-centered monopoles from molecular electrostatic potentials. The need for high sampling density in formamide conformational analysis. J. Comput. Chem. 11, 361–373 (1990).

    Article  CAS  Google Scholar 

  35. Berendsen, H. J. C., Grigera, J. R. & Straatsma, T. P. The missing term in effective pair potentials. J. Phys. Chem. 91, 6269–6271 (1987).

    Article  CAS  Google Scholar 

  36. Bussi, G., Donadio, D. & Parrinello, M. Canonical sampling through velocity rescaling. J. Chem. Phys. 126, 014101 (2007).

    Article  CAS  Google Scholar 

  37. Berendsen, H. J. C., Postma, J. P. M., Gunsteren, W. F., van; DiNola, A. & Haak, J. R. Molecular dynamics with coupling to an external bath. J. Chem. Phys. 81, 3684–3690 (1984).

    Article  CAS  Google Scholar 

  38. Pronk, S. et al. GROMACS 4.5: a high-throughput and highly parallel open source molecular simulation toolkit. Bioinformatics 29, 845–854 (2013).

    Article  CAS  Google Scholar 

  39. Van Der Spoel, D. et al. GROMACS: fast, flexible, and free. J. Comput. Chem. 26, 1701–1718 (2005).

    Article  CAS  Google Scholar 

  40. Poelking, C. & Andrienko, D. Long-range embedding of molecular ions and excitations in a polarizable molecular environment. J. Chem. Theory Comput. 12, 4516–4523 (2016).

    Article  CAS  Google Scholar 

  41. Poelking, C. & Andrienko, D. Design rules for organic donor-acceptor heterojunctions: pathway for charge splitting and detrapping. J. Am. Chem. Soc. 2015, 6320–6326.

  42. Poelking, C. et al. Impact of mesoscale order on open-circuit voltage in organic solar cells. Nat. Mater. 14, 434–439 (2015).

    Article  CAS  Google Scholar 

  43. D’Avino, G. et al. Electrostatic phenomena in organic semiconductors: fundamentals and implications for photovoltaics. J. Phys.: Condens. Matter 28, 433002 (2016).

    Google Scholar 

  44. Frisch, M. J. et al. Gaussian 16 Revision B.01 (Gaussian, Inc., 2016).

  45. Thole, B. T. Molecular polarizabilities calculated with a modified dipole interaction. Chem. Phys. 59, 341–350 (1981).

    Article  CAS  Google Scholar 

  46. Van Duijnen, P. Th & Swart, M. Molecular and atomic polarizabilities: Thole’s model revisited. J. Phys. Chem. A 102, 2399–2407 (1998).

    Article  Google Scholar 

  47. Stone, A. J. Distributed multipole analysis—stability for large basis sets. J. Chem. Theory Comput. 1, 1128–1132 (2005).

    Article  CAS  Google Scholar 

  48. Ruehle, V. et al. Microscopic simulations of charge transport in disordered organic semiconductors. J. Chem. Theory Comput. 7, 3335–3345 (2011).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

The authors thank C. Bauer, M. Beuchel, Hs-J. Guttmann, F. Keller and V. Maus for technical support and Y. Ie for the synthesis of 4CzIPN. This project has received funding from the European Union Horizon 2020 research and innovation programme under grant agreement no. 646176 (EXTMOS) and no. 646259 (MOSTOPHOS). D.A. thanks the BMBF grant InterPhase (grant no. FKZ 13N13661).

Author information

Authors and Affiliations

  1. Max Planck Institute for Polymer Research, Mainz, Germany

    Naresh B. Kotadiya, Anirban Mondal, Paul W. M. Blom, Denis Andrienko & Gert-Jan A. H. Wetzelaer

Authors
  1. Naresh B. Kotadiya
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Anirban Mondal
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Paul W. M. Blom
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Denis Andrienko
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Gert-Jan A. H. Wetzelaer
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

G.A.H.W. proposed the project. N.B.K. carried out sample preparation and electrical measurements. G.A.H.W. and N.B.K. analysed the experimental data. A.M. and D.A. devised and performed molecular-dynamics simulations. G.A.H.W., P.W.M.B. and D.A. supervised the project and wrote the manuscript, with input from N.B.K. and A.M.

Corresponding author

Correspondence to Gert-Jan A. H. Wetzelaer.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary materials, Supplementary Figs. 1–15, Supplementary Refs. 1–29

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Kotadiya, N.B., Mondal, A., Blom, P.W.M. et al. A window to trap-free charge transport in organic semiconducting thin films. Nat. Mater. 18, 1182–1186 (2019). https://doi.org/10.1038/s41563-019-0473-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41563-019-0473-6

This article is cited by

Search

Advanced 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