Development of Organic Thin-Film Electroluminescent Devices

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Novel thin-film electroluminescent (EL) devices which consisted of organic fluorescent dye (emitter) layer and charge transporting layers have been proposed through this research project. When the emitter materials have the electron (or hole) transporting tendency, the emitter layer should be stacked on the hole (or electron) transporting layer. If an emitter material has the bipoler carrier transporting tendency, the device should have a sandwich structure which consists of a hole transporting layer, an emitter layer and an electron transporting layer. We clarified that the most important factors for bright electroluminescence are the efficient injection of electrons and holes into the emitter layer, the efficient recombination of the injected carriers and confinement of the generated excitons within the emitter layer.Concerning the durability of the proposed EL devices, we showed that the most important factors were to avoid the crystallization of dye films and to avoid peeling of organic dye layers from the metallic electrode.The performance of our organic EL devices are as follows ; drive voltage is less than dc 10 V, input current is about 100 mA/cm^2, brightness is about 1000 cd/m^2, emission color is from blue to red and durability is approximately 500 hr.