Highly efficient blue phosphorescent and electroluminescent Ir( iii ) compounds

Three new Ir(iii) compounds with deep-blue phosphorescence have been synthesized. These molecules have the general formula of Ir(C super([and])N) sub(2)(L super([and])X), where C super([and])N = 2',6'-difluoro-2,3'-bipyridine (dfpypy) and L super([and])X = ancillary ligand such as 2-p...

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Published in:Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2013-01, Vol.1 (3), p.441-450
Main Authors: Kang, Youngjin, Chang, Yi-Lu, Lu, Jia-Sheng, Ko, Soo-Byung, Rao, Yingli, Varlan, Maria, Lu, Zheng-Hong, Wang, Suning
Format: Article
Language:English
Subjects:
Colour
Current efficiency
Devices
Electroluminescence
Ligands
Molecular orbitals
Phosphorescence
Transporting
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Summary:Three new Ir(iii) compounds with deep-blue phosphorescence have been synthesized. These molecules have the general formula of Ir(C super([and])N) sub(2)(L super([and])X), where C super([and])N = 2',6'-difluoro-2,3'-bipyridine (dfpypy) and L super([and])X = ancillary ligand such as 2-picolinate, pic (1), acetylacetonate, acac (2), or dipivaloylmethanoate, dpm (3). The ancillary ligands have been found to significantly destabilize both HOMO and LUMO levels of the Ir(iii) complexes, compared to Ir(dfpypy) sub(3), without significantly changing the phosphorescence energy. Compounds 1-3 emit bright blue phosphorescence with lambda sub(max) = 440-460 nm and quantum efficiencies of 0.60-0.95 in solution and the solid state. Double-layer electroluminescent devices using compounds 1-3 as the dopant, CDBP (4,4'-bis(9-carbazolyl)-2,2'-dimethylbiphenyl) as the host/hole transporting layer, and TPBi (1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene) as the electron transport layer have been fabricated. These EL devices show pure blue colour with high efficiency. The EL device of compound 3 at the doping level of 20 wt% shows the best performance with EQE of 10-15% at the brightness of 10-1000 cd m super(-2) and the maximum current efficiency of 22 cd A super(-1).
ISSN:2050-7526
2050-7534
DOI:10.1039/C2TC00270A