Blue emitting dlode using polyvenylcarbazole(PVCz) doped with perylene(PRL)and trlphenylamlne(TPA) as a hole transporting layer

2-(4'-tert-butyphenyl)-5-(4"-biphenyl)-1

3

4-oxadiazole(PBD)as a hole blocking layer and 8-hydroxyquinolinealumlrlum(Alq) as an electron injection layer has been constructed.By the dopingofTPA the performence of the device was impvoved.A luminance as high as 6100cd/m

2

with quantum efficiency 0.75% has been obtained.Energy diagram of the device was obtained bymeasured HOMO levels and band gaps of the materials used.Based on the energy diagram the balance of electrons and holes for diffirent devices was analyzed and the effect of TPA doping on diffirent devices was discussed.