A light outcoupling substrate and high performance white OLEDs were investigated. The light outcoupilng substrate achieved high light coupling efficiency of 42.8 % in a white OLED. A fluorescent / phosphorescent hybrid two-unit device achieved high luminous efficacy of 56 lm/W, high CRI of 91 and long lifetime of 150,000 h at 1,000 cd/m2 . An optically and electrically optimized two-unit of all phosphorescent white OLED realized quite high luminous efficacy of 83 lm/W and was estimated to be half decay lifetime of over 100,000 h.