Issue 56, 2016

Novel bis- and tris-cyclometalated iridium(iii) complexes bearing a benzoyl group on each fluorinated 2-phenylpyridinate ligand aimed at development of blue phosphorescent materials for OLED

Abstract

Novel bis- and tris-cyclometalated iridium(III) complexes bearing a benzoyl group on each fluorinated 2-phenylpyridinate ligand were developed, aimed at the development of blue phosphorescent materials for organic light-emitting diodes (OLED). When acetylacetonate (acac) was employed as an ancillary ligand, the emission wavelength (λPL) of the 5′-benzoylated bis-cyclometalated complex was blue-shifted up to 479 nm (in dichloromethane at rt, emitting bluish green) in combination with fluorine substituents. Ancillary ligand replacement in the 2-(5-benzoyl-4,6-difluorophenyl)pyridinate-based bis-cyclometalated complex from acac to picolinate gave rise to a further blue shift of λPL to 464 nm, and sky-blue emission was observed. The 2-(5-benzoyl-4,6-difluorophenyl)pyridinate-based homoleptic tris-cyclometalated complex exhibited a more blue-shifted λPL at 463 nm than any other bis- and tris-cyclometalated complexes developed here, emitting sky blue with a photoluminescence quantum yield of 0.90 (in dichloromethane at rt). Using this sky-blue phosphorescent tris-cyclometalated complex as an emitting dopant, a poly(9-vinylcarbazole)-based OLED was fabricated, and excellent blue emission with a Commission Internationale de L'éclairage (CIE) chromaticity coordinate of (0.16, 0.28) was observed, where an external quantum efficiency (ηext) of 1.81% was obtained. The OLED performance was drastically improved by using a solution-processed double-emitting layer device structure, and ηexts of 8.55 and 7.46% were achieved for the present sky-blue phosphorescent bis- and tris-cyclometalated iridium(III) complexes, respectively (CIE chromaticity coordinates: (0.17, 0.33) and (0.17, 0.29), respectively).

Graphical abstract: Novel bis- and tris-cyclometalated iridium(iii) complexes bearing a benzoyl group on each fluorinated 2-phenylpyridinate ligand aimed at development of blue phosphorescent materials for OLED

Supplementary files

Article information

Article type
Paper
Submitted
12 4 2016
Accepted
10 5 2016
First published
11 5 2016
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2016,6, 51435-51445

Novel bis- and tris-cyclometalated iridium(III) complexes bearing a benzoyl group on each fluorinated 2-phenylpyridinate ligand aimed at development of blue phosphorescent materials for OLED

N. Okamura, T. Nakamura, S. Yagi, T. Maeda, H. Nakazumi, H. Fujiwara and S. Koseki, RSC Adv., 2016, 6, 51435 DOI: 10.1039/C6RA09385J

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