Effects of intra- And interchain interactions on exciton dynamics of PTB7 revealed by model oligomers

Thomas J. Fauvell, Zhengxu Cai, Matthew S. Kirschner, Waleed Helweh, Pyosang Kim, Tianyue Zheng, Richard D. Schaller, Luping Yu, Lin X. Chen

Research output: Contribution to journalArticle

Abstract

Recent studies have shown that molecular aggregation structures in precursor solutions of organic photovoltaic (OPV) polymers have substantial influence on polymer film morphology, exciton and charge carrier transport dynamics, and hence, the resultant device performance. To distinguish photophysical impacts due to increasing π-conjugation from chain lengthening and π-π stacking from single/multi chain aggregation in solution and film, we used oligomers of a well-studied charge transfer polymer PTB7 with different lengths as models to reveal intrinsic photophysical properties of a conjugated segment in the absence of inter-segment aggregation. In comparison with previously studied photophysical properties in polymeric PTB7, we found that oligomer dynamics are dominated by a process of planarization of the conjugated backbone into a quinoidal structure that resembles the self-folded polymer and that, when its emission is isolated, this quinoidal excited state resembling the planar polymer chain exhibits substantial charge transfer character via solvent-dependent emission shifts. Furthermore, the oligomers distinctly lack the long-lived charge separated species characteristic of PTB7, suggesting that the progression from charge transfer character in isolated chains to exciton splitting in neat polymer solution is modulated by the interchain interactions enabled by self-folding.

Original languageEnglish
Article number2441
JournalMolecules
Volume25
Issue number10
DOIs
Publication statusPublished - May 2020

Keywords

  • Electronic processes
  • Excited state
  • OPV
  • Oligomer
  • PTB7
  • Structural dynamics

ASJC Scopus subject areas

  • Analytical Chemistry
  • Chemistry (miscellaneous)
  • Molecular Medicine
  • Pharmaceutical Science
  • Drug Discovery
  • Physical and Theoretical Chemistry
  • Organic Chemistry

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  • Cite this

    Fauvell, T. J., Cai, Z., Kirschner, M. S., Helweh, W., Kim, P., Zheng, T., Schaller, R. D., Yu, L., & Chen, L. X. (2020). Effects of intra- And interchain interactions on exciton dynamics of PTB7 revealed by model oligomers. Molecules, 25(10), [2441]. https://doi.org/10.3390/molecules25102441