Bipolar cyano-substituted pyridine derivatives for applications in organic light-emitting devices

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Juanjuan You
  • Shiu-Lun Lai
  • Weimin Liu
  • Tsz-Wai Ng
  • Pengfei Wang

Detail(s)

Original languageEnglish
Pages (from-to)8922-8929
Journal / PublicationJournal of Materials Chemistry
Volume22
Issue number18
Publication statusPublished - 14 May 2012

Abstract

A novel series of cyano-substituted pyridine derivatives have been synthesized and characterized. Besides the expected electron-transporting (ET) properties stemming from the pyridine structure, the cyanopyridines also show light-emitting (EM) as well as bipolar transporting properties upon incorporation of larger π-conjugated groups, such as N,N-dimethylbenzenamine and triphenylamine groups. With these multifunctional cyanopyridines, device structures can be simplified to use only two layers or even a single layer. Low turn-on and driving voltages, relatively high power efficiency η p and mild efficiency roll-off were demonstrated by the devices based on the compounds with better bipolar properties. The compound 2,6-bis(4-(diphenylamino) phenyl)-4-phenylpyridine-3,5-dicarbonitrile (PPPD) containing triphenylamine groups has relatively better hole-transporting (HT) ability. A device with a configuration of ITO/NPB (10nm)/PPPD (60nm)/BPhen (30nm)/LiF (0.5nm)/Mg: Ag (100nm) (where NPB is α-napthylphenylbiphenyl diamine, and BPhen is 7-diphenyl-1,10-phenanthroline), using PPPD as HT and EM layer, yields high efficiencies of 8.5 cd A -1 and 6.9 lm W -1 due to the balanced charge transporting. It is also found that substituting larger π-conjugated groups at the 4-position of the pyridine ring has a weak effect on the molecular properties because of the steric hindrance of the two cyano groups, suggesting a good linkage type for joining the cyano-substituted pyridine moiety with other HT moieties for further bipolar molecular design strategies. © 2012 The Royal Society of Chemistry.

Citation Format(s)

Bipolar cyano-substituted pyridine derivatives for applications in organic light-emitting devices. / You, Juanjuan; Lai, Shiu-Lun; Liu, Weimin; Ng, Tsz-Wai; Wang, Pengfei; Lee, Chun-Sing.

In: Journal of Materials Chemistry, Vol. 22, No. 18, 14.05.2012, p. 8922-8929.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review