The Effect of α-Branched Side Chains on the Structural and Opto-Electronic Properties of Poly(Diketopyrrolopyrrole-alt-Terthiophene)

Bart W.H. Saes, Martijn M. Wienk, René A.J. Janssen (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

6 Citations (Scopus)


Introducing solubilizing α-branched alkyl chains on a poly(diketopyrrolopyrrole-alt-terthiophene) results in a dramatic change of the structural, optical, and electronic properties compared to the isomeric polymer carrying β-branched alkyl side chains. When branched at the α-position the alkyl substituent creates a steric hindrance that reduces the tendency of the polymer to π–π stack and endows the material with a much higher solubility in common organic solvents. The wider π–π stacking and reduced tendency to crystallize, evidenced from grazing-incidence wide-angle X-ray scattering, result in a wider optical band gap in the solid state. In solar cells with a fullerene acceptor, the α-branched isomer affords a higher open-circuit voltage, but an overall lower power conversion efficiency as a result of a too well-mixed nanomorphology. Due its reduced π–π stacking, the α-branched isomer fluoresces and affords near-infrared light-emitting diodes emitting at 820 nm.

Original languageEnglish
Pages (from-to)14221-14228
Number of pages8
JournalChemistry - A European Journal
Issue number62
Publication statusPublished - 6 Nov 2020


  • aggregation
  • light-emitting diodes
  • organic solar cells
  • polymer semiconductors
  • thin film


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