Highly branched green phosphorescent tris-cyclometalated iridium(III) complexes for solution-processed organic light-emitting diodes

Wei Sheng Huang, Chia Wei Lin, Jiann T. Lin*, Jen Hsien Huang, Chih Wei Chu, Ying Hsien Wu, Hong-Cheu Lin

*Corresponding author for this work

Research output: Contribution to journalArticle

25 Scopus citations

Abstract

A series benzoimidazole-based dendritric complexes of iridium dendrimers containing Fréchet-type dendrons with peripheral fluorenyl surface groups have been synthesized. These iridium dendrimers are green-emitting with high phosphorescence quantum yield, and can be spin-coated as films of good quality. From cyclic voltammograms (CV), high onset potentials at 1.42-1.58 V due to the peripheral fluorene group were observed. Device from a second generation dendrimer 17 with structure of ITO/PEDOT:PSS/CBP: 20 wt% 17/TPBI/LiF/Al (PEDOT:PSS = poly(ethylene dioxythiophene): polystyrenesulfonate and CBP = bis(N-carbazolyl)biphenyl) has the best performance: maximum external quantum efficiency of 13.58% and maximum current efficiency of 45.7 cd/A. Space-charge-limited current (SCLC) flow technique was used to measure the mobility of charge carriers in the blend films of the compounds in CBP. Blend films of higher generation dendrimers have lower hole mobility, albeit with higher device efficiencies.

Original languageEnglish
Pages (from-to)594-606
Number of pages13
JournalOrganic Electronics
Volume10
Issue number4
DOIs
StatePublished - 1 Jan 2009

Keywords

  • Dendrimers
  • Iridium complexes
  • Organic light-emitting diodes
  • Phosphorescence

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