Phenylazomethine dendrimer complexes as novel hole-transporting materials of organic light-emitting diodes

The EL (electroluminescence) performances of a double-layer organic light-emitting diodes (OLED) that used metal complexable phenylazomethine dendrimers (PAM-Gn, n = 1-5) as novel hole-transporting materials and tris-(8-hydroxyquinoline) aluminum (Alq3) as an emitter with electron-transport material, have been demonstrated. The device that used PAM-G3 showed the highest EL performance compared to that of the other generations. Moreover, by using the metal ion (SnCl2) complexed PAM dendrimers as a hole-transporting layer, the luminance and the EL efficiency of the devices were drastically increased over those of the dendrimers. These results suggested a lower energy gap of the hole-transporting layer and/or increased the ohmic conductivity of the layers by metal complexation. In particular, we found that the optimum metal ion equivalent for the highest EL performance was dependent on the dendrimer generation.