Very efficient high-luminance electrophosphorescent emission in polymer light-emitting diodes

The electrophosphorescent emission properties were investigated in polymer light-emitting diodes (PLEDs) based on a poly(9-vinylcarbazole) (PVK) doped with a green phosphorescent dye of fac-tris(2-phenylpyridine) iridium (III) [Ir(ppy)/sub 3/]. A green light peaked at 516 nm was emitted from devices with a configuration of ITO/PEDOT:PSS/PVK:Ir(ppy)/sub 3//BCP/Alq/sub 3//LiF/Al. The optimal doping concentration of Ir(ppy)/sub 3/ in PVK was found at 2% by weight, under which maximum current efficiency of 24.3 cd/A and peak external quantum efficiency of 6.8% were achieved at the high luminance of 4240 cd/m/sup 2/. The external quantum efficiency of 5% and current efficiency of 18 cd/A can be sustained even at the very high luminance of 35000 cd/m/sup 2/.