Charge recombination electroluminescence in organic thin-film devices without charge injection from external electrodes

Organic thin-film electroluminescent (EL) devices with a double-insulated structure, Al electrode/polymer insulator layer/ambipolar EL layer/ITO nanoparticles layer/ambipolar EL layer/polymer insulator layer/ITO electrode, were fabricated. The ambipolar EL layer was the composition of poly (N-vinylcarbazole) as a hole transport material and 2,5-bis(4-naphthyl)-1,3,4-oxadiazole as an electron transport material in 65/35 molar ratio with added 0.6 mole % coumarin-6 for emissive centers. When the devices were driven with ac voltage, bright surface emission (81 cd/m(2) at 250 V and 300 kHz) was observed. Emission is due to the recombination of holes and electrons that are generated from ITO nanoparticles embedded in organic layers. Charge recombination EL is observed without charge injection from external electrodes in double-insulated organic EL devices. (C) 2004 American Institute of Physics.