Improved efficiency for white organic light-emitting devices based on phosphor sensitized fluorescence

Efficiency of white organic light-emitting devices (WOLEDs) based on phosphor sensitized fluorescence is improved by using an unusual device structure, in which an undoped blue emissive layer is sandwiched between two phosphorescent doped ones. This blue emissive layer blocks a triplet-triplet energy transfer between the two phosphorescent emissive layers, leading to balanced emissions of blue, green, yellow, and red. Thus, an efficient WOLED with a maximum luminous efficiency of 13.8cd∕A, a maximum power efficiency of 8.0lm∕W, a color rendering index of 79, and Commission Internationale de L’Eclairage coordinates of (0.33, 0.35) is achieved.