White-Light-Emitting Organic Electroluminescent Devices

在本研究项目中，我们首次研究了聚合物单层电致发光器件。研究了共聚物体系、聚合物共混体系和染料分散体系。n-乙烯基咔唑和1,3,4-恶二唑衍生物分别作为空穴传递单元和电子传递单元。在染料分散体系中，聚n -乙烯基咔唑（PVK）以低分子量的恶二唑衍生物分子分散。在适当的恶二唑浓度（约30wt%）下，单层器件显示出明亮的发光。同样，该共聚物体系是n -乙烯基咔唑和乙烯基恶二唑的无规共聚物，也显示出相当高的装置效率。相比之下，含有n -乙烯基咔唑和乙烯基二唑均聚物的聚合物共混体系的成膜性能较差。我们还研究了聚苯胺作为ITO电极空穴注入到空穴传输层的缓冲层。当空穴传输层为PVK时，旋铸后PVK层的退火处理提高了器件效率。这是由于聚苯胺层与PVK层之间的接触表面积增加所致。上述结果对开发高效白光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.