Blue phosphorescent dye as sensitizer and emitter for white organic light-emitting diodes

We demonstrate high-efficiency white organic light-emitting diodes with blue electrophosphorescent and red phosphor-sensitized electrofluorescent emission. The phosphorescent dye, bis[(4,6-difluorophenyl)-pyridinato-N,C2] (picolinato) Ir(III) (FIrpic) and the fluorescent dye, 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl) (DCJTB) are co-doped into host material, N,N′-dicarbazolyl-1, 4-dimethene-benzene (DCB). The device with 8% (weight ratio) FIrpic and 0.4% (weight ratio) DCJTB exhibits white emission and the maximum current efficiency and luminance are 9.2cd∕A and 18 200cd∕m2, respectively. For comparison, a device without FIrpic is fabricated which has poor performance. These results indicate that the blue phosphorescent dye acts not only as emitter but also as phosphorescent sensitizer for fluorescent dye.