Development of Organic Thin-Film Electroluminescent Devices

本研究提出了一种由有机荧光染料层和电荷传输层组成的新型薄膜电致发光器件。当发射体材料具有电子（或空穴）传输倾向时，发射体层应堆叠在空穴（或电子）传输层上。如果发射极材料具有双极载流子输运倾向，则器件应该具有由空穴输运层、发射极层和电子输运层组成的三明治结构。我们阐明了明亮电致发光的最重要因素是电子和空穴有效注入发射极层，注入载流子的有效复合和发射极层内产生的激子的限制。关于所提出的EL器件的耐久性，我们发现，最重要的因素是避免染料膜的结晶和避免有机染料层从金属电极上剥离。我们的有机EL器件的如下：驱动电压小于直流10 V，输入电流约为100 mA/cm ^2，亮度约为1000 cd/m^2，发射颜色从蓝色到红色，耐久性约为500 hr。

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.