White-Light-Emitting Organic Electroluminescent Devices

在本研究计画中，我们首先研究聚合物单层电激发光元件。研究了三种体系，包括共聚物、聚合物共混物和染料分散体。N-乙烯基咔唑和1，3，4-恶二唑衍生物分别用作空穴传输单元和电子传输单元。在染料分散体系中，聚（N-乙烯基咔唑）（PVK）与低分子量恶二唑衍生物分子分散。在适当的恶二唑浓度（约30wt%）下，单层器件表现出明亮的发射。类似地，共聚物系统，其是N-乙烯基咔唑和乙烯基恶二唑的无规共聚物，显示出相当高的器件效率。而含有N-乙烯基咔唑和乙烯基恶二唑均聚物的聚合物共混体系成膜性能较差。我们还研究了聚苯胺作为缓冲层从ITO电极向空穴传输层的空穴注入。当空穴传输层是PVK时，在旋铸之后PVK层的退火提高了器件效率。这是由于聚苯胺层与PVK层之间的接触表面积增加所致，上述结果对研制高效白光电致发光器件具有重要意义。

In this research project, we have first investigated polymer single layr EL devices. Three systems, including copolymer, polymer blend, and dye-dispersion were investigated. N-vinylcarbazole and 1,3,4-oxadiazole derivative were used as a holetransporting unit and electron-transporting unit, respectively. In the dye-dispersion system, poly (N-vinylcarbazole) (PVK) was molecularly dispersed with a low molecular weight oxadiazole derivative. With an appropriate concentration of the oxadiazole (approximately 30wt%), the single layr device exhibited bright emission. Similarly, the copolymer system, which is a random copolymer of N-vinylcarbazole and vinyloxadiazole, showed reasonably high device efficiency. In contrast, the polymer blend system, containing the homopolymers of N-vinylcarbazole and vinyloxadiazole, resulted in the poor film-forming property.We also investigated polyaniline as a buffer layr for the hole injection from ITO electrode to the hole transport layr. When the hole-transport layr is PVK,the annealing of the PVK layr after spincast improved device efficiency. This is attributed to the increase in the contact surface area between polyaniline layr and the PVK layr.The above results are quite useful for the development of efficient white-light-emitting EL devices.