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Abstract: The influence of the presence of a double emitting layer (DEL) consisting of 4,4′-Bis(carbazol-9-yl)biphenyl (CBP) and 4,4′-Bis(2,2-diphenyl-ethen-1-yl)diphenyl (DPVBi) acting as electron and hole trapping layers in the organic light-emitting devices (OLEDs) was studied. While the luminance efficiency of the OLEDs with a DEL was very stable, regardless of variations in the applied voltage, that of the OLEDs with a CBP or a DPVBi emitting layer varied with the applied voltage. The rate of decrease is smaller than the single emitting layer, about 30%. The dominant peak corresponding to the CBP layer, in the electroluminescence spectrum for the OLEDs with a DEL appeared at 451 nm, which is in the deep-blue region. The Commission Internationale de l''Eclairage chromaticity coordinates of the OLEDs with a DEL at 11 V were (0.150, 0.137), indicative of a deep, stabilized blue color. These results indicate that luminance efficiency-stabilized blue OLEDs can be fabricated using a CBP/DPVBi DEL acting as electron and hole trapping layers. [Copyright &y& Elsevier]

Abstract: The degradation behaviors of the electrical and the optical properties of organic light-emitting devices (OLEDs) fabricated with an emitting layer (EML) doped with or without a wide-bandgap-impurity were investigated. The OLEDs with a wide-bandgap-doped Alq3 EML were more stable than those with an undoped Alq3 EML. The existence of the doped wide-bandgap-impurity in the EML decreased the trap-charge density in the EML, resulting in an increase in the number of electrons in the Alq3 EML. That increases in the number of electron in the Alq3 EML for the OLEDs with a wide-bandgap-impurity decreased the staying time of the holes in the Alq3 EML, resulting in an enhanced lifetime for the OLEDs. These results indicate that OLEDs with a wide-bandgap-impurity-doped EML hold promise for potential applications in long-lifetime OLED displays. [Copyright &y& Elsevier]