Mixed side-chain geometries for aggregation control of poly(fluorene-alt-bithiophene) and their effects on photophysics and charge transport

Olivia Kettner, Andreas Pein, Gregor Trimmel, Paul Christian, Christian Werner Röthel, Ingo Salzmann, Roland Resel, Girish Lakhwani, Florian Lombeck, Michael Sommer, Bettina Friedel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In organic optoelectronics, order of conjugated molecules is required for good charge transport, but strong aggregation behavior may generate grain boundaries and trapping, opposing those benefits. Side chains on a polymer's backbone are major reason for and also tool to modify its morphological characteristics. In this report, we show on the example poly(9,9-dioctylfluorenyl-co-bithiophene) (F8T2) that by a combination of two types of side-chains on the backbone of equal number of carbons, one promoting crystallization, another hindering it, organization of the main chains can be controlled, without changing its major properties. We compare the traditional F8T2 derivative with octyl substituent with two modified species, one containing solely 2-ethylhexyl side-chains and another with both types randomly distributed. Thermal characteristics, photophysics and morphology are compared and effects on film formation and charge transport in bulk-heterojunction blends demonstrated on photovoltaic devices utilizing F8T2s as donor and the fullerene derivative ICBA as acceptor material.

Original languageEnglish
Pages (from-to)162-173
Number of pages12
JournalSynthetic Metals
Publication statusPublished - 1 Oct 2016


  • Aggregation
  • Charge transport
  • Organic electronics
  • Photophysics
  • Polymer
  • Side-chain engineering

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this