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.

Adduct-based p-doping of organic semiconductors

Abstract

Electronic doping of organic semiconductors is essential for their usage in highly efficient optoelectronic devices. Although molecular and metal complex-based dopants have already enabled significant progress of devices based on organic semiconductors, there remains a need for clean, efficient and low-cost dopants if a widespread transition towards larger-area organic electronic devices is to occur. Here we report dimethyl sulfoxide adducts as p-dopants that fulfil these conditions for a range of organic semiconductors. These adduct-based dopants are compatible with both solution and vapour-phase processing. We explore the doping mechanism and use the knowledge we gain to ‘decouple’ the dopants from the choice of counterion. We demonstrate that asymmetric p-doping is possible using solution processing routes, and demonstrate its use in metal halide perovskite solar cells, organic thin-film transistors and organic light-emitting diodes, which showcases the versatility of this doping approach.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Doping ability of the DMSO–HBr adduct for various HTMs.
Fig. 2: Mechanism of doping by the DMSO–HBr adduct.
Fig. 3: Thermal stability of the doped MeO-TPD films.
Fig. 4: Asymmetric doping in hole-only devices.
Fig. 5: Usage of adduct-based dopants in optoelectronic devices.

Data availability

The datasets used in this work are available in the Oxford University Research Archive repository48.

References

  1. 1.

    Granström, M. et al. Laminated fabrication of polymeric photovoltaic diodes. Nature 395, 257–260 (1998).

    Article  Google Scholar 

  2. 2.

    Halls, J. J. M. et al. Efficient photodiodes from interpenetrating polymer networks. Nature 376, 498–500 (1995).

    CAS  Article  Google Scholar 

  3. 3.

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

    CAS  Article  Google Scholar 

  4. 4.

    Tang, C. W. & Vanslyke, S. A. Organic electroluminescent diodes. Appl. Phys. Lett. 51, 913–915 (1987).

    CAS  Article  Google Scholar 

  5. 5.

    Yu, G., Gao, J., Hummelen, J. C., Wudl, F. & Heeger, A. J. Polymer photovoltaic cells: enhanced efficiencies via a network of internal donor–acceptor heterojunctions. Science 270, 1789–1791 (1995).

    CAS  Article  Google Scholar 

  6. 6.

    Blochwitz, J., Pfeiffer, M., Fritz, T. & Leo, K. Low voltage organic light emitting diodes featuring doped phthalocyanine as hole transport material. Appl. Phys. Lett. 73, 729–731 (1998).

    CAS  Article  Google Scholar 

  7. 7.

    Maennig, B. et al. Controlled p-type doping of polycrystalline and amorphous organic layers: self-consistent description of conductivity and field-effect mobility by a microscopic percolation mode. Phys. Rev. B 64, 195208 (2001).

    Article  CAS  Google Scholar 

  8. 8.

    Godet, C. Variable range hopping revisited: the case of an exponential distribution of localized states. J. Non-Cryst. Solids 302, 333–338 (2002).

    Article  Google Scholar 

  9. 9.

    Rubel, O., Baranovskii, S. D., Thomas, P. & Yamasaki, S. Concentration dependence of the hopping mobility in disordered organic solids. Phys. Stat. Sol. 171, 168–171 (2004).

    Google Scholar 

  10. 10.

    Blochwitz, J. et al. Interface electronic structure of organic semiconductors with controlled doping levels. Org. Electron. 2, 97–104 (2001).

    CAS  Article  Google Scholar 

  11. 11.

    Gao, W. & Kahn, A. Controlled p-doping of zinc phthalocyanine by coevaporation with tetrafluorotetracyanoquinodimethane: a direct and inverse photoemission study. Appl. Phys. Lett. 79, 4040–4042 (2001).

    CAS  Article  Google Scholar 

  12. 12.

    Harada, K. et al. Organic homojunction diodes with a high built-in potential: interpretation of the current–voltage characteristics by a generalized Einstein relation. Phys. Rev. Lett. 94, 36601 (2005).

    CAS  Article  Google Scholar 

  13. 13.

    Chan, C. K., Zhao, W., Barlow, S., Marder, S. & Kahn, A. Decamethylcobaltocene as an efficient n-dopant in organic electronic materials and devices. Org. Electron. 9, 575–581 (2008).

    CAS  Article  Google Scholar 

  14. 14.

    Lin, X. et al. Beating the thermodynamic limit with photo-activation of n-doping in organic semiconductors. Nat. Mater. 16, 1209–1215 (2017).

    CAS  Article  Google Scholar 

  15. 15.

    Tietze, M. L. et al. Elementary steps in electrical doping of organic semiconductors. Nat. Commun. 9, 1182 (2018).

    Article  CAS  Google Scholar 

  16. 16.

    Tietze, M. L., Burtone, L., Riede, M., Lüssem, B. & Leo, K. Fermi level shift and doping efficiency in p-doped small molecule organic semiconductors: a photoelectron spectroscopy and theoretical study. Phys. Rev. B 035320, 1–12 (2012).

    Google Scholar 

  17. 17.

    Li, J. et al. Measurement of small molecular dopant F4TCNQ and C60F36 diffusion in organic bilayer architectures. ACS Appl. Mater. Interfaces 7, 28420–28428 (2015).

    CAS  Article  Google Scholar 

  18. 18.

    Kolesov, V. A. et al. Solution-based electrical doping of semiconducting polymer films over a limited depth. Nat. Mater. 16, 474–481 (2017).

    CAS  Article  Google Scholar 

  19. 19.

    Yusubov, M. S., Filimonov, V. D. & Ogorodnikov, V. D. Dimethyl sulfoxide–hydrobromic acid as a novel reagent for convenient oxidation on a preparative scale of stilbenes and some derivatives of diphenylethane to benzils. Bull. Acad. Sci. USSR Div. Chem. Sci. 40, 766–770 (1991).

    Article  Google Scholar 

  20. 20.

    Lee, T. V. Oxidation adjacent to oxygen of alcohols by activated DMSO methods. Compr. Org. Synth. 7, 291–303 (1991).

    Article  Google Scholar 

  21. 21.

    Floyd, M. B., Du, M. T., Fabio, P. F., Jacob, L. A. & Johnson, B. D. The oxidation of acetophenones to arylglyoxals with aqueous hydrobromic acid in dimethyl sulfoxide. J. Org. Chem. 50, 5022–5027 (1985).

    CAS  Article  Google Scholar 

  22. 22.

    Sakai, N. et al. Solution-processed cesium hexabromopalladate(iv), Cs2PdBr6, for optoelectronic applications. J. Am. Chem. Soc. 139, 6030–6033 (2017).

    CAS  Article  Google Scholar 

  23. 23.

    Cappel, U. B., Daeneke, T. & Bach, U. Oxygen-induced doping of spiro-MeOTAD in solid-state dye-sensitized solar cells and its impact on device performance. Nano Lett. 12, 4925–4931 (2012).

    CAS  Article  Google Scholar 

  24. 24.

    Burschka, J. et al. Tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(iii) as p-type dopant for organic semiconductors and Its application in highly efficient solid-state dye-sensitized solar cells. J. Am. Chem. Soc. 133, 18042–18045 (2011).

    CAS  Article  Google Scholar 

  25. 25.

    Planells, M. et al. Diacetylene bridged triphenylamines as hole transport materials for solid state dye sensitized solar cells. J. Mater. Chem. A 1, 6949–6960 (2013).

    CAS  Article  Google Scholar 

  26. 26.

    Abate, A. et al. Protic ionic liquids as p-dopant for organic hole transporting materials and their application in high efficiency hybrid solar cells. J. Am. Chem. Soc. 135, 13538–13548 (2013).

    CAS  Article  Google Scholar 

  27. 27.

    Pellaroque, A. et al. Efficient and stable perovskite solar cells using molybdenum tris(dithiolene)s as p-dopants for spiro-OMeTAD. ACS Energy Lett. 2, 2044–2050 (2017).

    CAS  Article  Google Scholar 

  28. 28.

    Nguyen, W. H., Bailie, C. D., Unger, E. L. & McGehee, M. D. Enhancing the hole-conductivity of spiro-OMeTAD without oxygen or lithium salts by using spiro(TFSI)2 in perovskite and dye-sensitized solar cells. J. Am. Chem. Soc. 136, 10996–11001 (2014).

    CAS  Article  Google Scholar 

  29. 29.

    Chen, C. et al. Cu(ii) complexes as p-type dopants in efficient perovskite solar cells. ACS Energy Lett. 2, 497–503 (2017).

    CAS  Article  Google Scholar 

  30. 30.

    Ono, L. K. et al. Air-exposure-induced gas-molecule incorporation into spiro-MeOTAD films. J. Phys. Chem. Lett. 5, 1374–1379 (2014).

    CAS  Article  Google Scholar 

  31. 31.

    Fawcett, W. R. & Kloss, A. A. Solvent-induced frequency shifts in the infrared spectrum of dimethyl sulfoxide in organic solvents. J. Phys. Chem. 100, 2019–2024 (1996).

    CAS  Article  Google Scholar 

  32. 32.

    Wallace, V. M., Dhumal, N. R., Zehentbauer, F. M., Kim, H. J. & Kiefer, J. Revisiting the aqueous solutions of dimethyl sulfoxide by spectroscopy in the mid- and near-infrared: experiments and Car–Parrinello simulations. J. Phys. Chem. B 119, 14780–14789 (2015).

    CAS  Article  Google Scholar 

  33. 33.

    Zhao, Y. H., Abraham, M. H. & Zissimos, A. M. Fast calculation of van der Waals volume as a sum of atomic and bond contributions and its application to drug compounds. J. Org. Chem. 68, 7368–7373 (2003).

    CAS  Article  Google Scholar 

  34. 34.

    Kang, K. et al. 2D coherent charge transport in highly ordered conducting polymers doped by solid state diffusion. Nat. Mater. 15, 896–902 (2016).

    CAS  Article  Google Scholar 

  35. 35.

    Ávila, J. et al. High voltage vacuum-deposited CH3NH3PbI3–CH3NH3PbI3 tandem solar cells. Energy Environ. Sci. 11, 3292–3297 (2018).

    Article  Google Scholar 

  36. 36.

    Abdi-Jalebi, M. et al. Charge extraction via graded doping of hole transport layers gives highly luminescent and stable metal halide perovskite devices. Sci. Adv. 5, eaav2012 (2019).

    CAS  Article  Google Scholar 

  37. 37.

    Wanlass, M. Systems and methods for advanced ultra-high-performance InP solar cells. US patent 9590131B2 (2017).

  38. 38.

    Walzer, K., Maennig, B., Pfeiffer, M. & Leo, K. Highly efficient organic devices based on electrically doped transport layers. Chem. Rev. 107, 1233–1271 (2007).

    CAS  Article  Google Scholar 

  39. 39.

    Pfeiffer, M., Beyer, A., Fritz, T. & Leo, K. Controlled doping of phthalocyanine layers by cosublimation with acceptor molecules: a systematic Seebeck and conductivity study. Appl. Phys. Lett. 73, 3202–3204 (1998).

    CAS  Article  Google Scholar 

  40. 40.

    Nollau, A., Pfeiffer, M., Fritz, T. & Leo, K. Controlled n-type doping of a molecular organic semiconductor: naphthalenetetracarboxylic dianhydride (NTCDA) doped with bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF). J. Appl. Phys. 87, 4340–4343 (2000).

    CAS  Article  Google Scholar 

  41. 41.

    Kirchartz, T. et al. Sensitivity of the Mott–Schottky analysis in organic solar cells. J. Phys. Chem. C. 116, 7672–7680 (2012).

    CAS  Article  Google Scholar 

  42. 42.

    Deledalle, F. et al. Understanding the effect of unintentional doping on transport optimization and analysis in efficient organic bulk-heterojunction solar cells. Phys. Rev. X 5, 11032 (2015).

    Google Scholar 

  43. 43.

    Zonno, I., Martinez-Otero, A., Hebig, J. & Kirchartz, T. Understanding Mott–Schottky measurements under illumination in organic bulk heterojunction solar cells. Phys. Rev. Appl. 7, 034018 (2017).

    Article  Google Scholar 

  44. 44.

    Lin, Y.-H. et al. Deciphering photocarrier dynamics for tuneable high-performance perovskite–organic semiconductor heterojunction phototransistors. Nat. Commun. 10, 4475 (2019).

    CAS  Article  Google Scholar 

  45. 45.

    Lin, Y.-H. et al. Hybrid organic–metal oxide multilayer channel transistors with high operational stability. Nat. Electron. 2, 587–595 (2019).

    CAS  Article  Google Scholar 

  46. 46.

    Anaraki, E. H. et al. Highly efficient and stable planar perovskite solar cells by solution-processed tin oxide. Energy Environ. Sci. 9, 3128–3134 (2016).

    CAS  Article  Google Scholar 

  47. 47.

    Huang, Q. et al. Highly efficient top emitting organic light-emitting diodes with organic outcoupling enhancement layers. Appl. Phys. Lett. 88, 113515 (2006).

    Article  CAS  Google Scholar 

  48. 48.

    Sakai, N. et al. Adduct-Based p-Doping of Organic Semiconductors (Oxford University Research Archive, 2021); https://doi.org/10.5287/bodleian:zrMDxRzzB

Download references

Acknowledgements

This research has mainly received funding from the European Commission (PERTPV- agreement no. 763977) and EPSRC (EP/M005143/1 and EP/S004947/1). M.R. has received funding from the EC FP 7 MSCA—Career Integration Grant (630864) and M.R. and S.V.K. acknowledge funding from the EPSRC WAFT project (EP/M015173/1). R.W. is supported by EPSRC CDT Plastic Electronics (EP/L016702/1). P.K.N. acknowledges support from the Department of Atomic Energy, Government of India, under Project Identification no. RTI 4007 and SERB India core research grant (CRG/2020/003877). F.Z., X.L. and A.K. acknowledge funding from National Science Foundation under grants DMR-1506097 and DMR-1807797. S.N. acknowledges Marie Skłodowska-Curie Actions individual fellowships (grant agreement no. 659306) and a start-up grant from CSIR-IMMT, India. T.M. and V.G. acknowledge funding from European Regional Development Fund (project no. 01.2.2-LMT-K-718-03-0040) under a grant agreement with the Research Council of Lithuania (LMTLT). T.D.A. and A.B. are grateful to King Abdullah University of Science and Technology (KAUST), KAUST Solar Centre and KAUST Office for Sponsored Research (OSR) for the financial support under award no: OSR-2019-CRG8-4095, no. OSR-2018-CARF/CCF-3079. J.L. and C.G. are grateful for support for the NanoSIMS facility from EPSRC under grant EP/M018237/1. We thank I. McPherson for his help in mass spectrometry measurements and M. Heeney for providing the C16IDT-BT polymer.

Author information

Affiliations

Authors

Contributions

N.S. and P.K.N. conceived and executed the initial proof-of-concept experiments and unravelled the mechanism of doping. P.K.N. proposed the dopant system. H.J.S. proposed the asymmetric doping and N.S. designed and performed the experiments. N.S. and R.W. performed the conductivity measurements. N.S. and R.W. performed the doping stability test under the supervision of M.R. S.V.K. performed the ellipsometry measurements, analyses and simulation under the supervision of M.R. R.W. fabricated the OLEDs under the supervision of M.R. and N.S. fabricated all the other the devices used in this work. S.N. and P.K.N. performed the attenuated total reflection FTIR measurements. F.Z. and X.L. did the UPS, XPS and Kelvin probe measurements under the supervision of A.K. F.Z. did the AFM measurements. J.L. did the nanosecondary ion mass spectrometry measurements with inputs from P.K.N. and N.S. C.G. planned and helped interpret the nanosecondary ion mass spectrometry measurements. N.S. and Y.-H.L. performed the capacitance–voltage measurements. H.S.B. performed the quantum chemical calculations. T.M. conducted the synthesis of the HTM V886 and V.G. supervised the synthesis. A.B. fabricated the OTFTs and performed the electrical characterization under the supervision of T.D.A. T.D.A., Y.-H.L. and A.B. interpreted the results and provided the analysis of the OTFTs. N.S. and P.K.N. wrote the first draft. All the authors contributed to the analysis of the results, discussion of the content and revisions of the manuscript. P.K.N. and H.J.S. supervised the project.

Corresponding authors

Correspondence to Pabitra K. Nayak or Henry J. Snaith.

Ethics declarations

Competing interests

A patent based on this work has been filed (international application number PCT/GB2018/053014) by the University of Oxford. H.J.S. is a co-founder of Oxford PV Ltd and Helio Display Materials. The remaining authors declare no competing interests.

Additional information

Peer review information Nature Materials thanks Adam Moule and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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

Supplementary information

Supplementary Information

Characterization, Supplementary Figs. 1–42, Notes 1–9 and Tables 1–6.

Reporting Summary

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Sakai, N., Warren, R., Zhang, F. et al. Adduct-based p-doping of organic semiconductors. Nat. Mater. (2021). https://doi.org/10.1038/s41563-021-00980-x

Download citation

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