60.3: Two‐Stacked White Organic Light‐Emitting Diodes Consisting of Fluorescent and Phosphorescent Hybrid Structure with High Efficiency and Good Color Characteristics

We report an improved bottom‐emission two‐stacked white OLED structure consisting of one unit emitting fluorescent blue light and the other unit emitting phosphorescent yellow in one‐host and two‐dopant (R+G) system. By searching EL condition optimizing both phosphorescent green and red dopants within just one light‐emitting layer, we can get WOLEDs suitable for a display application with very high current and power efficiencies, and excellent color characteristics. Our device exhibits high external quantum efficiency of 28.8%, current efficiency of 56.5 cd/A, and power efficiency of 30 lm/W at 5.9 V and 1000 nit where color point is (0.368, 0.385) in x‐y color space (CIE 1931). Half‐lifetime (LT 50 ) of the device at 1000 nit is estimated more than 31,000 hrs and color variation by aging is suppressed within less than 0.02 in u'‐v'color space (CIE 1976). Color filter developed for our WOLED enables color gamut to become wider than the 100% NTSC in uniform color space (u', v').