Stable Efficiency Roll-off in Solution-processed Phosphorescent Green Organic Light-emitting Diodes

Using a mixed host system of hole transport, 4,4',4 ''-tris(N-carbazolyl)triphenylamine (TCFA), and electron transport, 1,3,5-tris(N-phenlybenzimidazole-2-yl)benzene (TPBI), materials, we report; stable efficiency roll-off in solution-processed phosphorescent. green organic light-emitting diodes. Maximum current and power efficiencies of 28.2 cd/A and 13.2 lm/W, respectively, were achieved. The current efficiency was over 90% of the maximum value at a luminance of 20,000 cd/m(2) in this device, which is very high compared to values reported earlier for an,), solution-processed triplet devices.