Synthesis and characteristics of bis(2,4-dimethyl-8-quinolinolato)(triphenylsilanolato)aluminum (III): A potential hole-blocking material for the organic light-emitting diodes

• Published in: Journal of organometallic chemistry Vol. 691; no. 12; pp. 2701 - 2707
• Main Authors: Lim, J.T., Jeong, C.H., Lee, J.H., Yeom, G.Y., Jeong, H.K., Chai, S.Y., Lee, I.M., Lee, W.I.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2006
• Subjects: 24MeSAlq; 8-Hydroxy-quinoline; HBL; Hole-blocking material; OLED; OLED; 8-Hydroxy-quinoline; HBL; Hole-blocking material; 24MeSAlq
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2006.02.002

The 5-coordinated bis(2,4-dimethyl-8-quinolinolato)aluminum (III) (24MeSAlq) was synthesized and characterized by various analyses. The high hole-blocking property of 24MeSAlq in the organic light-emitting devices (OLEDs) was enhanced by the high HOMO (highest Occupied Molecular Orbital) energy level. Its HOMO level was proved by cyclic voltammogram.
A new five-coordinated bis(2,4-dimethyl-8-quinolinolato)(triphenylsilanolato)aluminum (III) (24MeSAlq) material, having bulky substituents, was prepared in one-step reaction and was characterized. The photoluminescent (PL) spectrum of 24MeSAlq shows the largest hypsochromic shift exhibiting the maximum wavelength at the peak of 461
nm among the blue-emitting q
2AlOR-type complexes (q
=
8-quinolinolato ligand and OR
=
aryloxy or alkoxy ligand) reported. The deep blue device composed of ITO/2-TNATA (60
nm)/NPB (15
nm)/24MeSAlq (20
nm)/Alq
3 (45
nm)/LiF (1
nm)/Al (100
nm), which uses 24MeSAlq as a hole-blocking layer and applies a principle efficiently confining an exciton recombination zone into a hole transporting layer, shows the maximum electroluminescent (EL) at the peak of 446
nm originating from the NPB emissive layer. This is attributed to an excellent hole-blocking property due to the high HOMO (highest occupied molecular orbital) energy level (6.14
eV).