High operational stability of electrophosphorescent devices

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Abstract
Electrophosphorescent devices with fac-tris(2-phenylpyridine)iridium as the green emitting dopant have been fabricated with a variety of hole and exciton blocking materials. A device with aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolate (BAlq) demonstrates an efficiency of 19 cd/A with a projected operational lifetime of 10 000 h, operated at an initial brightness of 500 cd/m2; or 50 000 h normalized to 100 cd/m2. An orange-red electrophosphorescent device with iridium(III) bis(2-phenylquinolyl-N,C2′)acetylacetonate as the dopant emitter and BAlq as the hole blocker demonstrates a maximum efficiency of 17.6 cd/A with a projected operational lifetime of 5000 h at an initial brightness of 300 cd/m2; or 15 000 h normalized to 100 cd/m2. The average voltage increase for both devices is <0.3 mV/h. The device operational lifetime is found to be inversely proportional to the initial brightness, typical of fluorescent organic light emitting devices.