OLEDs with enhanced high temperature operational stability

Temperature dependence of electroluminescence degradation is studied in organic light emitting devices containing an emitting layer composed of a mixture of different hole transport molecules and tris(8-hydroxyquinoline)aluminum (AlQ(3)) electron transport and emitter molecule. The emitting layer is sandwiched between hole and electron transport layers. Devices containing the hole transport molecule N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB), doped with quinacridone (DMQ) green emitter showed remarkable temperature stability. For these devices, a half-life of about 78,500 hours, 18,700 hours, and 8,600 hours can be projected for operating temperatures of 22degreesC, 700degreesC and 100degreesC, respectively, at an initial device luminance of 100 cd/m(2). Activation energies for device degradation were determined for devices with different hole transport molecules and it was found that devices with higher activation energy show better high temperature stability. These results are consistent with the recently proposed degradation mechanism based on the unstable cationic AlQ(3) species