High-Efficiency White Organic Light-Emitting Diodes Using Codoped Blue-Light-Emitting Layers with Different Functional Materials

Abstract

We have demonstrated high-efficiency white organic light-emitting diodes (WOLEDs) using codoped blue-emitting layers with three light emitters, 4 ''-(2,2-diphenylvinyl)-1-[4-(N,N-diphenylamino)-styryl]-terphenyl, fac-tris(2-phenypyridine) iridium(III), and bis(5-benzoyl-2-phenylpyridinato-C,N)iridium(III) (acetylacetonate). Blue-emitting layers (BEMLs) were codoped with the different functional materials, N,N'-bis(1-naphyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine and 4,7-diphenyl-1,10-phenanthroline, which are used as charge-transporting materials in OLEDs. An optimized device with centralized carriers in emitting layers showed a maximum luminance of 19710 cd/m(2) at 12V, a maximum luminous efficiency of 23.20 cd/A at 0.14 mA/cm(2), and an external quantum efficiency of 10.20% at 32.19 cd/m(2). (C) 2009 The Japan Society of Applied Physics