White organic light-emitting devices with a bipolar transport layer between blue fluorescent and orange phosphorescent emitting layers

White organic light-emitting devices based on an orange phosphorescent iridium complex, bis(2-(2-fluorphenyl)-1,3-benzothiozolato-N,C-2') iridium (acetylacetonate) [(F-BT)(2)Ir(acac)] and blue fluorescent 4,4(')-bis(2,2(')-diphenylvinyl)-1,1(')-biphenyl are reported. By introducing a bipolar transport 4,4(')N,N-'-dicarbazole-biphenyl layer between the fluorescent and the phosphorescent emission layers, additional light emission from (F-BT)(2)Ir(acac) is observed. The authors attributed it to the elimination of the Dexter energy transfer between the two emitters. Pure white emission with Commission Internationale de I'Eclairage coordinates of (0.33, 0.34) and a maximum luminance of 40960 cd/m(2) were obtained. The maximum current efficiency and the color rendering index of the device are 13.4 cd/A and 71, respectively. (C) 2007 American Institute of Physics.