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

Abstract

White organic light-emitting devices based on an orange phosphorescent iridium complex, bis(2-(2-fluorphenyl)-1,3-benzothiozolato-N,C2′) iridium (acetylacetonate) [(F-BT)2Ir(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)2Ir(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 40960cd∕m2 were obtained. The maximum current efficiency and the color rendering index of the device are 13.4cd∕A and 71, respectively.