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 (TCTA), and electron transport, 1, 3, 5-tris(N-phenylbenzimidazole-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/m² in this device, which is very high compared to values reported earlier for any solution-processed triplet devices.