BLUE LUMINESCENT DEVICE UTILIZING 2-(4-BIPHENYLYL)-5-(4-T-BUTYLPHENYL)-1-3,4-OXADIAZOLE AS HOLE BLOCKING LAYER

By placing an hole blocking layer between the polymer and the metallic electrode, we have improved efficiencies for blue light-emitting diodes fabricated with 1,1,4,4-tetraphenyl-1,3-butadiene doped poly(N-vinyl carbazole) as the emitting layer and with aluminum and ITO as the electron and hole injecting electrodes. The bilayer device yields bright blue emission having intensity of 300 cd/m(2) in the same case the device without hole limiting layer have luminance only 44 cd/m(2).