POLYQUINOXALINE AS AN ELECTRON INJECTING MATERIAL FOR ELECTROLUMINESCENT DEVICE

A series of 2,3-disubstituted poly(quinoxaline-5,8-diyl) (PQx) was cla rified to be an excellent electron injecting material for electrolumin escent (EL) devices, since these have many advantageous properties suc h as high electron affinity ( Ea : 3.3 similar to 3.4 eV), good therma l stability, good processability and sufficiently low refractive index . On the other hand, since poly( p-phenylenevinylene) (PPV) was known as a good hole injecting material (ionization potential, Ip : 5.1eV), an EL device with ITO/PPV/PQx/Metal type structure was suggested. It w as shown that the quantum efficiency of the cell was about twice as hi gh as that of ITO/PPV/Metal cell. Related physical and optical propert ies of PQx derivatives are also investigated.