White light-emitting electroluminescent devices were fabricated using poly(N-vinylcarbazole) (PVK) as a hole-transporting emitter layer and a double layer of 1,2,4-triazole derivative (TAZ) and tris(8-quinolinolato)aluminum(III) complex (Alq) as an electron transport layer. The PVK layer was doped with fluorescent dyes such as blue-emitting 1,1,4,4-tetraphenyl-1,3-butadiene, green-emitting coumarin 6, and orange-emitting DCM 1. A cell structure of glass substrate/indium-tin-oxide/doped PVK/TAZ/Alq/Mg:Ag was employed. White emission covering a wide range of the visible region and a high luminance of 3400 cd/m2 were obtained at a drive voltage of 14 V.

Organic electroluminescent (EL) devices with a trivalent europium (Eu) complex as an emitter were fabricated. Triple-layer-type cells with a structure of glass substrate/indium-tin oxide/ triphenyldiamine derivative (TPD)/Eu complex: 1,3,4-oxadiazole derivative (PBD)/aluminum complex (Alq)/Mg:Ag exhibit bright red luminescence upon applying dc voltage. The EL spectrum consists of extremely sharp emission bands, which is a typical luminescence spectrum of the Eu complex. Luminance of 460 cd/m2 with an emission peak at 614 nm is achieved at a drive voltage of 16 V. This is the highest luminance so far obtained for the EL cells having a Eu complex as an emitter.

Electroluminescent devices were fabricated using poly(N-vinylcarbazole) (PVK) as a hole-transporting emitter layer and a double layer of 1,2,4-triazole derivative (TAZ) and tris(8-quinolinolato)aluminum(III) complex (Alq) as an electron transport layer. A cell structure of glass substrate/indium-tin-oxide/PVK/TAZ/Alq/Mg:Ag was employed. In this cell structure, carrier injection from the electrodes to the PVK layer and concomitant electroluminescence from PVK were observed. Blue emission peaking at 410 nm and a luminance of 700 cd/m2 were achieved at a drive voltage of 14 V.

Organic electroluminescent devices with multilayer structures were fabricated using a 1,2,4-triazole derivative as the carrier transport layer. 3-(4-Biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ) was found to be electron-transporting, and a cell with a structure of glass substrate/indium-tin oxide/triphenylamine derivative (TPD)/TAZ/Alq/Mg:Ag exhibited bright blue electroluminescence from the TPD layer. A luminance of 3700 cd/m2 with an emission peak at 464 nm was achieved at a drive voltage of 16 V.

Triple‐layer‐type organic electroluminescent devices were fabricated using charge‐transporting poly(N‐vinylcarbazole) (PVK) as a hole‐transporting emitter layer. Electron‐transporting layers consisting of a triazole derivative (TAZ) and an aluminum complex (Alq) layer were used to maximize the carrier recombination efficiency. The EL device with a structure of glass substrate/indium‐tinoxide/PVK/TAZ/AIq/Mg:Ag showed bright blue emission from the PVK layer with a luminance of over 700 cd/m2. The emission color was tuned to a desirable color in the visible region through doping the PVK layer with fluorescent dyes. Bright white emission, in particular, was obtained for the first time at a high luminance level of over 3000 cd/m2 by using three kinds of fluorescent dyes each emitting red, green or blue.