BRIGHT BLUE ELECTROLUMINESCENT DEVICES UTILIZING POLY (N-VINYLCARBAZOLE) DOPED WITH FLUORESCENT DYE

Bright blue electroluminescent devices have been fabricated using poly (N-vinylcarbazole) (PVK) doped with perylene as the emissive layer, p oly(p-phenylenevinylene) (PPV) as the hole-transporting layer, iphenyl yl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), tris(8-hydroxyquino line)aluminum (Alq(3)) as the electron-transporting layer, and Al as t he cathode. A luminance of 700 cd/m(2) and a luminescent efficiency of 0.8% are achieved at a drive voltage of 36 V. In the experiment, it i s found that the introduction of electron-transporting layer PBD has a great effect on the emissive color of the electroluminescent devices prepared by PVK doped with perylene. Yellow-green emission is observed from the device structure of glass substrate/indium-tin-oxide/PVK:per ylene/Al. The possible emissive mechanisms are given. The effect of th e transporting layer on the electroluminescence is also discussed. (C) 1997 Elsevier Science S.A.