New host copolymers containing pendant triphenylamine and carbazole for efficient green phosphorescent OLEDs

Chih Cheng Lee, Kun Ming Yeh, Yun Chen

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

A series of vinyl copolymers (P1-P6) containing pendant hole-transporting triphenylamine (11-88 mol%) and carbazole chromophores were synthesized by radical copolymerization to investigate the influence of triphenylamine groups upon optoelectronic properties. The copolymers were readily soluble in common organic solvents and their weight-average molecular weights (Mws) were between 1.41 × 104 and 2.24 × 104. They exhibited moderate thermal stability with Td = 402-432 °C at 5% weight loss. The emission spectra (both PL and EL) of the blends [P1-P6 with 4 wt% Ir(ppy)3] showed dominant green emission (517 nm) attributed to Ir(ppy)3 due to efficient energy transfer from P1-P6 to Ir(ppy)3. The HOMO levels of P1-P6, estimated from onset oxidation potentials in cyclic voltammeter, were -5.42 to -5.18 eV, which are much higher than -5.8 eV of conventional poly(9-vinylcarbazole) (PVK) host owing to high hole-affinity of the triphenylamine groups. The optoelectronic performances of phosphorescent EL devices, using P1-P6 as hosts and Ir(ppy)3 as dopant (ITO/PEDOT:PSS/P1-P6:Ir(ppy)3 (4 wt%):PBD (40 wt%)/BCP/Ca/Al), were greatly improved relative to that of PVK. The best performance was obtained with P4 device, in which the maximum luminance and luminance efficiency were 11 501 cd/m2 and 10.6 cd/A, respectively.

Original languageEnglish
Pages (from-to)4211-4217
Number of pages7
Journalpolymer
Volume49
Issue number19
DOIs
Publication statusPublished - 2008 Sep 9

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Materials Chemistry

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