Effect of the Charge Balance on High-Efficiency Blue-Phosphorescent Organic Light-Emitting Diodes

The charge balance in blue-phosphorescent devices was studied using single-carrier devices, and the results show that the transport is highly hole dominant. The effect of the charge balance on the device performance was further demonstrated using different electron-transport materials with different electron mobilities. By optimization of the charge balance, a maximum current efficiency of 60 Cd A(-1) at a luminance of 500 cd m(-2) was achieved.