Solid-state light-emitting devices based on the tris-chelated ruthenium (II) complex. 2. Tris (bipyridyl) ruthenium (II) as a high-brightness emitter

Abstract

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)₃²⁺-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.