Highly efficient organic light-emitting devices

For organic light-emitting devices (OLEDs), improving efficiency is very important. Many scientists are interested in it. In this paper, we report some of our results. The optical and electrical characteristics of organic red light-emitting devices are improved through utilizing the two-step energy transfer, the maximum efficiency is 2.9 cd/A. The efficiency of white organic light-emitting devices has been improved dramatically by the introduction of phosphorescent material fac tris (2-phenylpyridine) indium [Ir(ppy)3] as sensitizer. The maximum efficiency is 6.0 cd/A. Two kinds of new phosphorescent materials (s-phen)Re(CO)₃Cl (s-phen = 3,9-dimethyl-1,10-phenanthroline) and (s-bpy) Re(CO)₃Cl (s-bpy = 4,4´dimethyl formate-2,2´-bipyridine) are employed to fabricate the organic electrophosphorescence devices. The maximum efficiencies and the light colors of the devices based on (s-phen)Re(CO)₃Cl and (s-bpy) Re(CO)₃Cl are 7.15 cd/A, yellow and 1.28 cd/A, orange-red, respectively. The devices with two rubrene sub-monolayers are fabricated. The maximum electroluminescent efficiency of the device was 6.61 cd /A at 7 V. It was higher than the common dope-type device, and besides, the efficiency is relatively independent on the drive voltage in the range from 5 to 13 V. The brightness can reach 18610 cd/m² at 13 V.