Blue emission dye doped polymer-based electroluminescent devices for display

Low operating voltage organic molecule dye doped polymers blue electroluminescent (EL) devices were constructed by using air stable aluminum as cathode 1,1,4,4,-tetraphenyl- 1,3-butadiene (TPB) doped poly (N-Vinylcarbazole) (PVK) was used as the light emitting layer, and a layer of tris(8- quinolinolate)-Aluminum(Alq3) film worked as an electron-transporting layer. A device with two layer structure of indium-tin-oxide(ITO)/TPB:PVK/Alq3/Al was obtained. Blue emission began at DC bias voltage of 3.5 V, and blue electroluminescence of 500 cd/m2 was observed at about 10 V, the EL peak was at 449 nm. By using Al as cathode, 2-(4-biphenylyl)-5-(4-terbutypheny)-1-3,4- oxadiazole(PBD) as hole-blocking layer, the device with the structure of ITO/TPB:PVK/PBD/Alq3/Al was also fabricated. Blue emission began at 4 V, more than 1000 cd/m2 was observed at 14 V. These are among the lowest known operating voltage for polymeric EL devices using air stable electrodes. The characteristics of these two kinds of structure devices have also been investigated.