To further improve the efficacy of hybrid WOLEDs, light extraction is very necessary because a large number of generated photons (70–80%) are trapped inside the device [71], [72] and [73]. It should be pointed out that the light extraction for white emission should give consideration to the optical performances as CIE and CRI. Reineke and co-workers have reported a good light out-coupling structure based on a hemisphere for WOLEDs [9]. Using this technique, a hybrid WOLED with 63.6 lm/W at 1967 cd/m2 was achieved by Loebl et al. [74], and another one with the efficacy up to 90.5 lm/W (improved by a factor of 2.9) at 1000 cd/m2 was achieved by Rosenow et al. [75].