High external quantum efficiency red phosphorescent light-emitting devices

We report the fabrication of high-efficiency organic light-emitting diodes employing a novel red phosphor by managing charge transport properties of every functional layer. Doped hole transport layer and stepwise carrier transport system were utilized to enlarge charge injection, improve transportation and reduce drive voltage. The devices turned on at quiet low voltages of about 3∼4 V. A high power efficiency of 10.63 lm/W and a stable red emission at 616 nm (chromaticity coordinate: x=0.63, y=0.35) was obtained. Especially, the maximal external quantum efficiency reached 15.5% at 18.62 cd/m 2 .