Quinoid-Aromatic Resonance for Very Small Optical Energy Gaps in Small-Molecule Organic Semiconductors: A Naphthodithiophenedione-oligothiophene Triad System

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Abstract

Organic semiconductors with very small optical energy gaps have attracted a lot of attention for near-infrared-active optoelectronic applications. Herein, we present a series of donor-acceptor-donor (D−A−D) organic semiconductors consisting of a highly electron-deficient naphtho[1,2-b:5,6-b′]dithiophene-2,7-dione quinoidal acceptor and oligothiophene donors that show very small optical energy gaps of down to 0.72 eV in the solid state. Investigation of the physicochemical properties of the D−A−D molecules as well as theoretical calculations of their electronic structures revealed an efficient intramolecular interaction between the quinoidal acceptor and the aromatic oligothiophene donors in the D−A−D molecules; this significantly enhances the backbone resonance and thus reduces the bond length alternation along the π-conjugated backbones. Despite the very small optical energy gaps, the D−A−D molecules have low-lying frontier orbital energy levels that give rise to air-stable ambipolar carrier transport properties with hole and electron mobilities of up to 0.026 and 0.043 cm2 V−1 s−1, respectively, in field-effect transistors.

Original languageEnglish
Pages (from-to)15660-15670
Number of pages11
JournalChemistry - A European Journal
Volume27
Issue number63
DOIs
Publication statusPublished - 2021 Nov 11

Keywords

  • ambipolar carrier transport
  • donor-acceptor
  • near-infrared absorption
  • quinoid-aromatic resonance
  • small-bandgap organic semiconductors

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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