OXADIAZOLE DERIVATIVES FOR EMITTER AND CARRIER TRANSPORT MATERIALS IN ORGANIC ELECTROLUMINESCENT DEVICES

Ten oxadiazole derivatives which were newly synthesized were examined as an emitter in organic electroluminescence (EL) cells. The new oxadiazole derivatives exhibited the photoluminescence (PL) peaks at the wavelength region between 374 and 527 nm. Vacuum-deposited thin films of these compounds had excellent thermal stability, because they have high melting temperature ranging from 240 to 365-degrees-C. The organic EL cells with 4,4'-bis[5-(p-dimethylaminophenyl)-1,3,4-oxadiazol-2-yl]biphenyl, 1,3-bis[5-(p-dimethylaminophenyl)-1,3,4-oxadiazol-2-yl]benzene and 1,4-bis[5-(p-dimethylaminophenyl)-1,3,4-oxadiazol-2-yl]benzene as an emitter showed bright emission whose intensities were 1000 approximately 2000 cd/m2. The emission colors were green, blue, and green, respectively. These three oxadiazole derivatives were found to exhibit specific electronic characteristics that they transport both holes and electrons. Utilization of these materials for both emitter and electron transport materials were demonstrated.