Synthesis, characterization and electroluminescence properties of new iridium complexes based on cyclic phenylvinylpyridine derivatives: Tuning of emission colour and efficiency by structural control

Shin Ya Takizawa, Yuka Sasaki, Md Akhtaruzzaman, Hidenori Echizen, Jun Ichi Nishida, Takeshi Iwata, Shizuo Tokito, Yoshiro Yamashita

研究成果: Article査読

18 被引用数 (Scopus)

抄録

A series of phosphorescent cyclometalated iridium(iii) complexes 4-6 with new ligands of bicyclic phenylvinylpyridines have been synthesized and systematically examined for their photophysical, electrochemical and electroluminescence (EL) properties. All of the bis- and tris-cyclometalated complexes could be characterized by 1H-NMR, elemental analysis and X-ray crystal structure analysis. The phosphorescence colour of the complexes in solution, the solid state and polymer film is unusually changed depending on the structure of the ligand. EL devices using the complexes exhibited external quantum efficiencies (EQE) of 1.2-8.1% at 100 cd m-2, and EL colour tuning in the range of 571-635 nm was achieved analogous to PL properties of the phosphors. X-Ray analyses of complexes 4a-c demonstrated that the degree of steric hindrance increases with an increase of the cycloalkane ring size, leading to hypsochromic shifts of emission by the distortion of the phenyl groups. X-Ray analyses also suggested that long iridium-carbon bonds are unfavorable for efficient electroluminescence. In addition, we have found a unique and important aspect for the study of EL devices: the EL devices based on complexes 4c, 6a show moderate EL efficiencies (EQE = 4.0 and 6.1%) although these complexes have no emission in solution at room temperature, indicating that the PL properties of the complexes in solution are not directly related to the EL efficiencies.

本文言語English
ページ(範囲)841-849
ページ数9
ジャーナルJournal of Materials Chemistry
17
9
DOI
出版ステータスPublished - 2007 2 28

ASJC Scopus subject areas

  • 化学 (全般)
  • 材料化学

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