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Solution-based electrical doping of semiconducting polymer films over a limited depth

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Abstract

Solution-based electrical doping protocols may allow more versatility in the design of organic electronic devices; yet, controlling the diffusion of dopants in organic semiconductors and their stability has proven challenging. Here we present a solution-based approach for electrical p-doping of films of donor conjugated organic semiconductors and their blends with acceptors over a limited depth with a decay constant of 10–20 nm by post-process immersion into a polyoxometalate solution (phosphomolybdic acid, PMA) in nitromethane. PMA-doped films show increased electrical conductivity and work function, reduced solubility in the processing solvent, and improved photo-oxidative stability in air. This approach is applicable to a variety of organic semiconductors used in photovoltaics and field-effect transistors. PMA doping over a limited depth of bulk heterojunction polymeric films, in which amine-containing polymers were mixed in the solution used for film formation, enables single-layer organic photovoltaic devices, processed at room temperature, with power conversion efficiencies up to 5.9 ± 0.2% and stable performance on shelf-lifetime studies at 60 °C for at least 280 h.

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Figure 1: Optical properties of P3HT films immersed in a solution of PMA.
Figure 2: Properties and interactions of doped P3HT films.
Figure 3: Photo-oxidation and electrical properties of doped P3HT films.
Figure 4: PMA-doped OPV devices.
Figure 5: Single-layer OPV devices.

Change history

  • 10 January 2017

    In the original version published, the S(2s) peak in Fig. 2a was not clearly labelled. This has now been corrected.

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Acknowledgements

This work was funded in part by the Department of the Navy, Office of Naval Research Award No. N00014-14-1-0580 and N00014-16-1-2520, through the MURI Center CAOP, Office of Naval Research Award N00014-04-1-0313 and by the Department of Energy through the Bay Area Photovoltaic Consortium under Award Number DE-EE0004946. The authors would also like to thank J. Anthony and S. Barlow for helpful discussions. B.K. acknowledges a Visiting Professorship from the University of Cologne, Germany.

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V.A.K., C.F.-H., N.A., S.R.M., W.-F.C., F.A.L. and B.K. conceived and developed the ideas. V.A.K. and F.A.L. designed the experiments and performed device fabrication, electrical characterization. A.P., C.F.-H. and S.G. performed shelf lifetime and thermal stress experiments. C.F.-H. and W.-F.C. performed photo-oxidation and spectroscopic ellipsometry experiments. C.F.-H. modelled spectroscopic ellipsometry data. S.C. and W.-F.C. performed XPS measurements. M.W., G.C.B. and T.-Q.N. synthesized the donor polymer PIPCP used in this study. C.F.-H., S.R.M. and B.K. coordinated and directed the study. All authors contributed to the manuscript preparation.

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Correspondence to Bernard Kippelen.

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Kolesov, V., Fuentes-Hernandez, C., Chou, WF. et al. Solution-based electrical doping of semiconducting polymer films over a limited depth. Nature Mater 16, 474–480 (2017). https://doi.org/10.1038/nmat4818

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