Blue emission from light-emitting diodes based on lithium complex

We report the optical and electroluminescent properties of the lithium complex of (2,3-dimethyl-8-hydroxyquinoline) lithium (LiMMq), exhibiting intense photoluminescence (PL), peaked at about 458 nm. As the result of electron-donating methyl groups in 8-hydroxyquinoline, the PL spectrum is blue-shifted relative to (8-hydroxyquinoline) lithium (Liq). The double-layer electroluminescent devices with a novel polymer poly(N,N'-diphenyl-N,N'-bis(4-methylphenyl)-1,4-phenylenediamine-1,3 -diisopropenylbenzene) as hole transporting layer and the LiMMq as emitting layer, sandwiched between cathode of Mg:Ag alloy and anode of indium-tin oxide, were fabricated, and the bright blue electroluminescence with luminance of more than 8000 cd m-2 was obtained. The properties indicate that the LiMMq is a potential blue emitting material for the application in light-emitting diodes. (author)