Bis-tridentate IrIII Phosphors Bearing Two Fused Five-Six-Membered Metallacycles : A Strategy to Improved Photostability of Blue Emitters

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

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Author(s)

  • Ling-Yang Hsu
  • Qiumin Liang
  • Zhiheng Wang
  • Hsin-Hung Kuo
  • Wun-Shan Tai
  • Shi-Jian Su
  • Xiuwen Zhou
  • Yi Yuan

Detail(s)

Original languageEnglish
Pages (from-to)15375-15386
Journal / PublicationChemistry - A European Journal
Volume25
Issue number67
Online published1 Oct 2019
Publication statusPublished - 2 Dec 2019

Abstract

Iridium complexes bearing chelating cyclometalates are popular choices as dopant emitters in the fabrication of organic light-emitting diodes (OLEDs). In this contribution, we report a series of blue-emitting, bis-tridentate IrIII complexes bearing chelates with two fused five-six-membered metallacycles, which are in sharp contrast to the traditional designs of tridentate chelates that form the alternative, fused five-five metallacycles. Five IrIII complexes, Px-21-23, Cz-4, and Cz-5, have been synthesized that contain a coordinated dicarbene pincer chelate incorporating a methylene spacer and a dianionic chromophoric chelate possessing either a phenoxy or carbazolyl appendage to tune the coordination arrangement. All these tridentate chelates afford peripheral ligand-metal-ligand bite angles of 166-170°, which are larger than the typical bite angle of 153-155° observed for their five-five-coordinated tridentate counterparts, thereby leading to reduced geometrical distortion in the octahedral frameworks. Photophysical measurements and TD-DFT studies verified the inherent transition characteristics that give rise to high emission efficiency, and photodegradation experiments confirmed the improved stability in comparison with the benchmark fac-[Ir(ppy)3] in degassed toluene at room temperature. Phosphorescent OLED devices were also fabricated, among which the carbazolyl-functionalized emitter Cz-5 exhibited the best performance among all the studied bis-tridentate phosphors, showing a maximum external quantum efficiency (EQEmax) of 18.7 % and CIEx,y coordinates of (0.145, 0.218), with a slightly reduced EQE of 13.7 % at 100 cd m-2 due to efficiency roll-off.

Research Area(s)

  • chelates, iridium, organic light-emitting diodes, ligand design, luminescence, EXTERNAL QUANTUM EFFICIENCY, LIGHT-EMITTING-DIODES, PLATINUM(II) COMPLEXES, IRIDIUM COMPLEXES, METAL-COMPLEXES, LIGANDS SYNTHESIS, MOLECULAR DESIGN, NHC, CONTINUUM, POTENTIALS

Citation Format(s)

Bis-tridentate IrIII Phosphors Bearing Two Fused Five-Six-Membered Metallacycles : A Strategy to Improved Photostability of Blue Emitters. / Hsu, Ling-Yang; Liang, Qiumin; Wang, Zhiheng; Kuo, Hsin-Hung; Tai, Wun-Shan; Su, Shi-Jian; Zhou, Xiuwen; Yuan, Yi; Chi, Yun.

In: Chemistry - A European Journal, Vol. 25, No. 67, 02.12.2019, p. 15375-15386.

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