Preparation and Characterization of High Efficient Blue-Light Emitting Materials with a Secondary Ligand for Organic Electroluminescence

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Abstract
In this paper, a blue-light emitting material, bis(2-methyl-quinolinolato)(phenolato) aluminum(III) (Alq2 ′OPh), was synthesized. Organic electroluminescent (EL) devices have been fabricated with the homemade organometallic compound as the emitting layer and N,N′-diphenyl-N,N′-di(m-tolyl)benzidinev (TPD) as the hole transport layer, blue light emission with a high efficiency was obtained. Compared with tris (8-hydroxyquinoline) aluminum (Alq3), the presence of the phenolato ligand shifts the light emission to the blue region of the spectrum. The maximum wavelength of the EL is at around 495 nm and the brightness is up to 4000 cd/m2 with the maximum efficiency up to 1.4 lm/W. Two new compounds have also been prepared in order to investigate the effect of the secondary ligand. The comparison study indicates that the organometallic compound with a secondary ligand, not only the sterical effect but also some other effect would be responsible for the change of the emission wavelength.