Organic soluble indigoids derived from 3-hydroxybenzaldehyde for N-type organic field-effect transistor (OFET) applications

Jenner H.L. Ngai, Louis M L LEUNG*, Shu Kong SO, Harrison K.H. Lee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Two new series of organic soluble indigoids 7-7′-dialkoxyindigoids (2a, 2b) and 4,4′-dibromo-7,7′-dialkoxyindigoids (3a, 3b) (alkoxy = n-butoxy and n-octyloxy) were synthesized starting from the inexpensive 3-hydroxybenzaldehyde. The indigoids were soluble in common organic solvents including chloroform, dichloromethane, toluene, ethyl acetate and ethers. The enhanced solubility was suggested to be a lack of intermolecular hydrogen-bonds as confirmed by single crystal X-ray diffraction analyses. It was found that intramolecular hydrogen-bonds in indigoids are crucial to the exhibition of field-effect in OFETs, while intermolecular hydrogen-bonds only caused insolubility of the indigoids. Compared to the pristine insoluble indigo (LUMO = -3.55 eV and Eg = 1.91 eV), the soluble indigoids containing electron donating alkoxy side chains at the indigoid 7 and 7′ positions were shown to have their LUMO decreased by -0.13 to -0.26 eV. Among the indigoid studied, the soluble indigoid 3a containing electron donating alkoxy side chains at the indigoid 7 and 7′ positions and bromine groups at the indigoid 4 and 4′ positions exihibited a narrowest bandgap energy with Eg = 1.66 eV. Employing the same fabrication technique and a bottom-gate-top-contact OFET configuration, the soluble indigoids were found to have electron mobility similar to and within an order of magnitude of the pristine indigo.

Original languageEnglish
Pages (from-to)258-266
Number of pages9
JournalOrganic Electronics
Volume32
DOIs
Publication statusPublished - May 2016

Scopus Subject Areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering

User-Defined Keywords

  • 3-Hydroxybenzaldehyde
  • Baeyer Drewson indigo synthesis
  • OFET
  • Organic semiconductors
  • Organic soluble indigoids

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