Abstract
We demonstrate herein the design and fabrication of a highly efficient yellow organic light-emitting diode (OLED) with a balanced carrier injection device architecture having a zero electron-injection-barrier host blended with a hole-injection aiding co-host. The resultant yellow OLED showed, at 1,000 cd m-2 for example, an efficacy of 59 lm W-1, current efficiency of 71 cd A-1 and external quantum efficiency (EQE) of 23%, while 42 lm W-1, 47 cd A-1 and 15% EQE without co-host. The co-host effect that resulted in a much balanced carrier injection was also valid for other yellow OLED devices and their efficiency improvement was also very marked. With the use of a micro-lens, the device efficiency is further improved to 79 lm W-1, 96 cd A-1 and 30% EQE.