Synthesis, characterization, and photophysics of electroluminescent fluorene/dibenzothiophene- and fluorene/dibenzothiophene-S,S-dioxide-based main-chain copolymers bearing benzimidazole-based iridium complexes as backbones or dopants

Wei Sheng Huang, Ying Hsien Wu, Ying Chan Hsu, Hong-Cheu Lin*, Jiann T. Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

A series of electroluminescent copolymers containing fluorene-2,8-disubstituted dibenzothiophene (PFD), fluorene-2,8-disubstituted dibenzothiophene-S,S-dioxide (PFDo) and phosphorescent benzimidazole-based iridium (Ir) complexes in the backbones were synthesized by the Suzuki coupling reaction. The thermal stabilities, HOMO/LUMO levels and triplet energy gap (ET) values were enhanced with increasing contents of dibenzothiophene (D) or dibenzothiophene-S,S-dioxide (Do) segments in the copolymers. The relative intensities of phosphorescence and fluorescence were affected by the energy transfer and back transfer efficiencies between the polymer backbones and iridium units as evidenced by solid state PL and EL spectra. PLED devices with a configuration of ITO/PEDOT:PSS (50 nm)/metal-free copolymers (P1-P5), Ir-copolymers (P7-P13) and Ir-doped copolymers (P3 doped with Ir-complexes 6 and 8) (60-80 nm)/TPBI (40 nm)/LiF (1 nm)/Al (120 nm) were fabricated, and the electroluminescence (EL) efficiencies depended on the chemical constituents and triplet energies of the copolymers. The space-charge-limited current (SCLC) flow technique was used to measure the charge carrier mobilities of these copolymers, where both hole and electron mobilities were in the following order: the metal-free copolymers (P2, P3 and P5) > Ir-doped copolymers (P3 + 3 or 10 mol% Ir-complex 6) > Ir-copolymers (P7, P8, P12 and P13).

Original languageEnglish
Pages (from-to)5945-5958
Number of pages14
JournalPolymer
Volume50
Issue number25
DOIs
StatePublished - 27 Nov 2009

Keywords

  • Charge carrier mobilities
  • Iridium complex
  • Phosphorescence

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