High-efficiency and high-contrast phosphorescent top-emitting organic light-emitting devices with p-type Si anodes

We report high-efficiency and high-contrast phosphorescent topemitting organic light-emitting devices (OLEDs) by employing the low reflectance p-type Si bottom anodes and the high transmittance Cs(2)CO(3)/Ag top cathodes for effective hole and electron injection. With the green electrophosphorescent material fac tris (2-phenylpyridine) iridium [Ir(ppy)(3)] doped emitting layer, the devices exhibit peak external quantum and power efficiencies of 3.5% (12 cd/A) and 4.5 lm/W, which are the highest values reported for OLEDs using Si wafers as electrodes. Moreover, these devices exhibit significantly higher contrast compared to the conventional bottom-emitting and top-emitting OLEDs with the highly reflective back electrodes.