Molecular Doping Directed by a Neutral Radical

Jian Liu, Bas van der Zee, Diego R. Villava, Gang Ye, Simon Kahmann, Max Kamperman, Jingjin Dong, Li Qiu, Giuseppe Portale, Maria A. Loi, Jan C. Hummelen, Ryan C. Chiechi, Derya Baran, L. Jan Anton Koster

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Molecular doping makes possible tunable electronic properties of organic semiconductors, yet a lack of control of the doping process narrows its scope for advancing organic electronics. Here, we demonstrate that the molecular doping process can be improved by introducing a neutral radical molecule, namely nitroxyl radical (2,2,6,6-teramethylpiperidin-i-yl) oxyl (TEMPO). Fullerene derivatives are used as the host and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazoles (DMBI-H) as the n-type dopant. TEMPO can abstract a hydrogen atom from DMBI-H and transform the latter into a much stronger reducing agent DMBI•, which efficiently dopes the fullerene derivative to yield an electrical conductivity of 4.4 S cm–1. However, without TEMPO, the fullerene derivative is only weakly doped likely by a hydride transfer following by an inefficient electron transfer. This work unambiguously identifies the doping pathway in fullerene derivative/DMBI-H systems in the presence of TEMPO as the transfer of a hydrogen atom accompanied by electron transfer. In the absence of TEMPO, the doping process inevitably leads to the formation of less symmetrical hydrogenated fullerene derivative anions or radicals, which adversely affect the molecular packing. By adding TEMPO we can exclude the formation of such species and, thus, improve charge transport. In addition, a lower temperature is sufficient to meet an efficient doping process in the presence of TEMPO. Thereby, we provide an extra control of the doping process, enabling enhanced thermoelectric performance at a low processing temperature.
Original languageEnglish (US)
JournalACS Applied Materials & Interfaces
StatePublished - Jun 16 2021

Bibliographical note

KAUST Repository Item: Exported on 2021-06-18
Acknowledged KAUST grant number(s): OSRCRG2018-3737
Acknowledgements: This study was supported by a grant from STW/NWO (VIDI 13476). This study is part of the research program of the Foundation of Fundamental Research on Matter (FOM), which is part of The Netherlands Organization for Scientific Research (NWO). This is a publication by the FOM Focus Group “Next Generation Organic Photovoltaics”, participating in the Dutch Institute for Fundamental Energy Research (DIFFER). J.D. acknowledge financial support from the China Scholarship Council. S.K. acknowledges the Deutsche
Forschungsgemeinschaft (DFG) for a postdoctoral research fellowship (grant no. 408012143). L.Q. thanks National Natural Science Foundation of China (Grant No. 51962036) for financial support. G.Y. acknowledges the China Postdoctoral Science Foundation Funded Project (grant 2020M672771). D.B. and D.R. acknowledge King Abdullah University of Science and Technology (KAUST) Office of
Sponsored Research (OSR) under award no. OSRCRG2018-3737 for the completion of this work. J.L. thanks Xuwen Yang for the help in preparing PL samples.

ASJC Scopus subject areas

  • General Materials Science


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