New semiconductors based on 2,2′-ethyne-1,2-diylbis[3-(alk-1-yn-1-yl) thiophene] for organic opto-electronics

Pierre Luc T Boudreault, Jonathan W. Hennek, Stephen Loser, Rocio Ponce Ortiz, Brian J. Eckstein, Antonio Facchetti, Tobin J Marks

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Abstract

We report the synthesis and properties of three novel acetylenic materials based on the new electron-rich building block, 2,2′-ethyne-1,2-diylbis[3- (alk-1-yn-1-yl)thiophene] (EBT). The synthesis of this new nonacene core is efficient and straightforward, and variation among n-hexyl, n-tetradecyl, and 2-ethylhexyl substituents substantially impacts the materials properties. Appending 2-ethylhexyl substituted diketopyrrolopyrrole (DPP) units to either terminus of the EBT core yields a series of low band gap molecules that are characterized in detail by a range of experimental microstructure and electronic structure probes and by density functional theory (DFT) computation. Detailed morphology/microstructure characterization of spin-cast films by X-ray diffraction and AFM reveals instructive microstructure and electronic/ photovoltaic response relationships in both organic field-effect transistors and bulk-heterojunction organic photovoltaic cells. Thus, the former devices exhibit hole mobilities (μ h) as large as ∼0.2 cm 2/(V s) which fall as thermal annealing increases long-range order. The latter devices using PC 61BM as the electron acceptor exhibit power conversion efficiencies as high as ∼2%, which appear to fall as the materials become less ordered. These results are in accord with a model where evolving grain boundaries and crystallinity impedes hole transport and excitonic charge generation.

Original languageEnglish
Pages (from-to)2929-2942
Number of pages14
JournalChemistry of Materials
Volume24
Issue number15
DOIs
Publication statusPublished - Aug 14 2012

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Keywords

  • arylacetylene
  • EBT
  • OPVs
  • OTFTs
  • small molecules

ASJC Scopus subject areas

  • Materials Chemistry
  • Chemical Engineering(all)
  • Chemistry(all)

Cite this

Boudreault, P. L. T., Hennek, J. W., Loser, S., Ortiz, R. P., Eckstein, B. J., Facchetti, A., & Marks, T. J. (2012). New semiconductors based on 2,2′-ethyne-1,2-diylbis[3-(alk-1-yn-1-yl) thiophene] for organic opto-electronics. Chemistry of Materials, 24(15), 2929-2942. https://doi.org/10.1021/cm301095x