Towards understanding the doping mechanism of organic semiconductors by Lewis acids

Brett Yurash, David Xi Cao, Viktor V. Brus, Dirk Leifert, Ming Wang, Alana Dixon, Martin Seifrid, Ahmed E. Mansour, Dominique Lungwitz, Tuo Liu, Peter J. Santiago, Kenneth R. Graham, Norbert Koch, Guillermo C. Bazan, Thuc Quyen Nguyen

Research output: Contribution to journalArticlepeer-review

94 Scopus citations

Abstract

Precise doping of organic semiconductors allows control over the conductivity of these materials, an essential parameter in electronic applications. Although Lewis acids have recently shown promise as dopants for solution-processed polymers, their doping mechanism is not yet fully understood. In this study, we found that B(C6F5)3 is a superior dopant to the other Lewis acids investigated (BF3, BBr3 and AlCl3). Experiments indicate that Lewis acid–base adduct formation with polymers inhibits the doping process. Electron–nuclear double-resonance and nuclear magnetic resonance experiments, together with density functional theory, show that p-type doping occurs by generation of a water–Lewis acid complex with substantial Brønsted acidity, followed by protonation of the polymer backbone and electron transfer from a neutral chain segment to a positively charged, protonated one. This study provides insight into a potential path for protonic acid doping and shows how trace levels of water can transform Lewis acids into powerful Brønsted acids.

Original languageEnglish
Pages (from-to)1327-1334
Number of pages8
JournalNature Materials
Volume18
Issue number12
DOIs
StatePublished - Dec 1 2019

Bibliographical note

Funding Information:
This work was supported by the Department of Energy under Award No. DESC0017659. D.X.C. was supported by the National Science Foundation Graduate Research Fellowship Program under grant no. 1650114. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. D. Leifert was supported by the Alexander von Humboldt Foundation (Feodor Lynen Return Fellowship). XPS, UPS and EPR were obtained at a facility supported by the MRSEC programme of the NSF foundation (no. DMR-1121053). We acknowledge support from the Center for Scientific Computing from the CNSI for the DFT calculations (no. NSF CNS-1725797). This research used beamline 7.3.3 of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. T.L. and K.R.G. contributed the UPS and IPES measurements under work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences and the EPSCoR programme, under award no. DE-SC0018208. A.E.M. and N.K. acknowledge support by the DFG (FoMEDOS—Projektnummer 286798544). V.V.B. would like to thank J. Vollbrecht for help in processing data, and A. Lill for preparation of substrates with interdigitated contacts.

Publisher Copyright:
© 2019, The Author(s), under exclusive licence to Springer Nature Limited.

ASJC Scopus subject areas

  • Chemistry (all)
  • Materials Science (all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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