This work was supported by a CERG Grant from the Hong Kong Research Grants Council (HKBU2022/03P) and a Faculty Research Grant from the Hong Kong Baptist University (FRG/04-05/II-59).
Amorphous Diphenylaminofluorene-Functionalized Iridium Complexes for High-Efficiency Electrophosphorescent Light-Emitting Diodes†
Article first published online: 6 MAR 2006
Copyright © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Advanced Functional Materials
Volume 16, Issue 6, pages 838–846, April, 2006
How to Cite
Wong, W.-Y., Zhou, G.-J., Yu, X.-M., Kwok, H.-S. and Tang, B.-Z. (2006), Amorphous Diphenylaminofluorene-Functionalized Iridium Complexes for High-Efficiency Electrophosphorescent Light-Emitting Diodes. Adv. Funct. Mater., 16: 838–846. doi: 10.1002/adfm.200500523
- Issue published online: 30 MAR 2006
- Article first published online: 6 MAR 2006
- Manuscript Accepted: 17 NOV 2005
- Manuscript Received: 8 AUG 2005
- Iridium complexes;
- Light-emitting diodes, organic;
Two new phosphorescent iridium(III) cyclometalated complexes, [Ir(DPA-Flpy)3] (1) and [Ir(DPA-Flpy)2(acac)] (2) ((DPA-Flpy)H = (9,9-diethyl-7-pyridinylfluoren-2-yl)diphenylamine, Hacac = acetylacetone), have been synthesized and characterized. The incorporation of electron-donating diphenylamino groups to the fluorene skeleton is found to increase the highest occupied molecular orbital (HOMO) levels and add hole-transporting ability to the phosphorescent center. Both complexes are highly amorphous and morphologically stable solids and undergo glass transitions at 160 and 153 °C, respectively. These iridium phosphors emit bright yellow to orange light at room temperature with relatively short lifetimes (< 1 μs) in both solution and the solid state. Organic light-emitting diodes (OLEDs) fabricated using 1 and 2 as phosphorescent dopant emitters constructed with a multilayer configuration show very high efficiencies. The homoleptic iridium complex 1 is shown to be a more efficient electrophosphor than the heteroleptic congener 2. Efficient electrophosphorescence with a maximum external quantum efficiency close to 10 % ph/el (photons per electron), corresponding to a luminance efficiency of ∼ 30 cd A–1 and a power efficiency of ∼ 21 lm W–1, is obtained by using 5 wt.-% 1 as the guest dopant.