Structure-property relationship study of substitution effects on isoindigo-based model compounds as electron donors in organic solar cells

Yi Ren, Anna M. Hiszpanski, Luisa Whittaker-Brooks, Yueh Lin Loo

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

We designed and synthesized a series of isoindigo-based derivatives to investigate how chemical structure modification at both the 6,6′- and 5,5′-positions of the core with electron-rich and electron-poor moieties affect photophysical and redox properties as well as their solid-state organization. Our studies reveal that 6,6′-substitution on the isoindigo core results in a stronger intramolecular charge transfer band due to strong electronic coupling between the 6,6′-substituent and the core, whereas 5,5′-substitution induces a weaker CT band that is more sensitive to the electronic nature of the substituents. In the solid state, 6,6′- derivatives generally form J-aggregates, whereas 5,5′-derivatives form H-aggregates. With only two branched ethylhexyl side chains, the 6,6′-derivatives form organized lamellar structures in the solid state. The incorporation of electron-rich benzothiophene, BT, substituents further enhances ordering, likely because of strong intermolecular donor-acceptor interactions between the BT substituent and the electron-poor isoindigo core on neighboring compounds. Collectively, the enhanced photophysical properties and solid-state organization of the 6,6′-benzothiophene substituted isoindigo derivative compared to the other isoindigo derivatives examined in this study resulted in solar cells with higher power conversion efficiencies when blended with a fullerene derivative.

Original languageEnglish (US)
Pages (from-to)14533-14542
Number of pages10
JournalACS Applied Materials and Interfaces
Volume6
Issue number16
DOIs
StatePublished - 2014

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Keywords

  • Isoindigo
  • J -aggregation
  • organic solar cells
  • photophysics
  • solid-state organization

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