Phosphorescence color tuning by ligand, and substituent effects of multifunctional iridium(III) cyclometalates with 9-arylcarbazole moieties

Cheuk Lam Ho, Qi Wang, Ching Shan Lam, Wai Yeung Wong, Dongge Ma, Lixiang Wang, Zhi Qiang Gao, Chin Hsin Chen, Kok Wai Cheah, Zhenyang Lin

Research output: Journal article publicationJournal articleAcademic researchpeer-review

130 Citations (Scopus)

Abstract

The synthesis, isomeric studies, and photophysical characterization of a series of multifunctional cyclometalated iridium(III) complexes containing a fluoro- or methyl-substituted 2-[3-(N-phenylcarbazolyl)]pyridine molecular framework are presented. All of the complexes are thermally stable solids and highly efficient electrophosphors. The optical, electrochemical, photo-, and electrophosphorescence traits of these iridium phosphors have been studied in terms of the electronic nature and coordinating site of the aryl or pyridyl ring substituents. The correlation between the functional properties of these phosphors and the results of density functional theory calculations was made. Arising from the pro-pensity of the electron-rich carbazolyl group to facilitate hole injection/transport, the presence of such a moiety can increase the highest-occupied molecular orbital levels and improve the charge balance in the resulting complexes relative to the parent phosphor with 2-phenylpyridine ligands. Remarkably, the excited-state properties can be manipulated through ligand and substituent effects that allow the tuning of phosphorescence energies from bluish green to deep red. Electrophosphorescent organic light-emitting diodes (OLEDs) with outstanding device performance can be fabricated based on these materials, which show a maximum current efficiency of approximately 43.4 cd A-1, corresponding to an external quantum efficiency of approximately 12.9% ph/el (photons per electron) and a power efficiency of approximately 33.4 Lm W-1for the best device. The present work provides a new avenue for the rational design of multifunctional iridium-carbazolyl electrophosphors, by synthetically tailoring the carbazolyl pyridine ring that can reveal a superior device performance coupled with good color-tuning versatility, suitable for multicolor-display technology. KGaA.
Original languageEnglish
Pages (from-to)89-103
Number of pages15
JournalChemistry - An Asian Journal
Volume4
Issue number1
DOIs
Publication statusPublished - 5 Jan 2009
Externally publishedYes

Keywords

  • Carbazole
  • Color tuning
  • Iridium complexes
  • Organic light-emitting diodes
  • Phosphorescence

ASJC Scopus subject areas

  • Chemistry(all)

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