Role of oxygen within end group substituents on film morphology and charge carrier transport in thiophene/phenylene small-molecule semiconductors

Witold Waliszewski, Zachary S. Parr, Agnieszka Michalska, Roman Halaksa, Hanna Zajaczkowska, Piotr Sleczkowski, Marios Neophytou, Beata Luszczynska, Paul W.M. Blom, C. B. Nielsen, Tomasz Marszalek, Wojciech Pisula

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2 Scopus citations


In this study, the end group polarity of (5,5′)-biphenyl-(2,2’)-bithiophenes (PTTPs) was systematically varied from alkyl (1) to alkoxy (2) with one oxygen atom to glycol (3) with two oxygen atoms while the overall length of the end groups is kept constant. Thin films of the three compounds were sublimated at different substrate temperatures and their morphology, crystallinity and charge carrier transport in field-effect transistors was investigated to draw structure-property relationships for the PTTP derivatives. For all three compounds, the effective charge carrier mobility is improved with higher substrate temperatures at which films with higher crystallinity and larger grains are formed. The effective mobility decreases with higher polarity of the end groups from alkyl to alkoxy and glycol. The reliability factor of the alkyl (1) and alkoxy (2) substituted PTTPs decreases with higher substrate temperature, but at the same time this value is enhanced for the glycol substituted molecules (3). The transistors of 3 prepared at higher substrate temperatures also show a reduced threshold voltage and smaller hysteresis in the transfer characteristics. These insights are important for the understanding of the impact of oxygen incorporation into side chain/end group substituents of organic semiconductors and their implementation in organic electrochemical transistors, thermoelectrics and photovoltaics.
Original languageEnglish (US)
Pages (from-to)106608
JournalOrganic Electronics
StatePublished - Aug 10 2022

Bibliographical note

KAUST Repository Item: Exported on 2022-09-14
Acknowledgements: W. Waliszewski and W. Pisula acknowledge the National Science Centre, Poland through the grant UMO-2019/33/B/ST3/1550. A Michalska, H. Zajaczkowska, P. Sleczkowski, B. Luszczynska, T. Marszalek and W. Pisula acknowledge the Foundation for Polish Science financed by the European Union under the European Regional Development Fund (POIR.04.04.00-00-3ED8/17). Z. S. Parr and C. B. Nielsen acknowledge support from the Academy of Medical Sciences & Wellcome Trust (SBF002/1158). The authors also acknowledge Beamline 9 of the DELTA electron storage ring in Dortmund for providing synchrotron radiation and technical support for GIWAXS measurements.

ASJC Scopus subject areas

  • Materials Chemistry
  • Biomaterials
  • General Chemistry
  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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