We report high-brightness, high-efficiency, solid-state light-emitting devices based on small-molecule
Ru(bpy)3(PF6)2 and its derivatives. These devices operate at low voltage (as low as 2.5 V), suggesting a close
parallel with well-documented liquid electrogenerated chemiluminescence cells. We have realized luminance
levels as high as 1000 cd/m2 at only 5 V with spin-cast films and 200 cd/m2 at 3 V. Emitted light is red or
red-orange in color. At low voltage, external quantum efficiencies on the order of 1% are attainable. Luminance
levels and efficiencies of these magnitudes are unprecedented in solid-state Ru(bpy)3
2+-based devices. A
significant time delay is observed between voltage application and device response, as previously reported.
We find that the low-voltage time delay can be circumvented using an initial high-voltage pulse, affording
nearly instantaneous high brightness.
A ruthenium polypyridyl complex has been synthesized and examined as an emitter material in thin film electroluminescent devices. This material exhibits photoluminescent and electroluminescent effects as well as several reversible one-electron oxidation and reduction processes. Electroluminescent devices fabricated from this ruthenium complex either via spin coating methods or self-assembly techniques exhibit relatively high electroluminescent efficiencies and luminance levels in some cases as high as 100 cd/m2.
Fig. 4. SEM images showing carbon nanotube electrode surface with a deposit of polyaniline. The polymer has completely coated the nanotubes in (A) and partially in (B) where bare nanotubes are also visible. The morphology of the polyaniline deposit is found to be granular with nanosize domains. The scale bars indicated on the images correspond to 100 nm.
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