Characteristics of organic electroluminescent devices using polypyrrole conducting layer

We observed EL properties based on PVK, poly(3,6-N-2-ethylhexyl carbazolyl cyanoterephthalidene) (PECCP) and Alq3 emitting material devices with doped PPy conducting layer (>5 S/cm) and undoped polyacetylene derivative layer (PEPB, 10−10–10−11 S/cm) on top of rough ITO (surface resistance: less than 7 Ω/□). PPy conducting layer improved an EL efficiency of ITO/TPD/Alq3/Al device, which has a rough ITO surface of more than 1000 Å peak to peak level. In PVK, PECCP EML device, when PPy is layered on top of ITO, the turn-on voltage is lowered from 13 to 10 V and from 15 to 9 V, respectively. The conductivity of undoped PEPB film is too low to improve EL property though it has good smoothness.