Determination of the optical band gap of Alq3 and its derivatives for the use in two-layer OLEDs

Mart Mari Duvenhage, Martin Ntwaeaborwa, Hendrik G. Visser, Pieter J. Swarts, Jannie C. Swarts, Hendrik C. Swart

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


Tris-(8-hydroxyquinolinato)aluminium (Alq3) was used as both the emission and electron transporting layer in organic light emitting diodes. One way to tune the emissive color of Alq3 is to introduce substituents onto the hydroxyquinoline ligands. These substituents will have an effect on the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. In this study, Alq3 powders were synthesized with -CH3 substituted at position 5 and 7 (tris-(5,7-dimethyl-8-hydroxyquinolinato)aluminium) and -Cl at position 5 (tris-(5-chloro-8-hydroxyquinolinato) aluminium). Optical absorption and cyclic voltammetry measurements were performed on the samples. The optical band gap was determined from these measurements. The band gap did not vary with more than 0.2 eV from the theoretical value of Alq3.

Original languageEnglish
Pages (from-to)193-198
Number of pages6
JournalOptical Materials
Publication statusPublished - 1 Apr 2015
Externally publishedYes


  • Absorption
  • Cyclic voltammetry
  • OLEDs
  • Optical band gap
  • Tauc's relation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Computer Science
  • Atomic and Molecular Physics, and Optics
  • Spectroscopy
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Electrical and Electronic Engineering


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