Red Electroluminescence from an Organic Europium Complex with a Triphenylphosphine Oxide Ligand

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Abstract
An Eu-complex, europium tris(dibenzoylmethide) (triphenylphosphine oxide), was newly synthesized and utilized as a light-emitting material in electroluminescent devices. The complex was easily deposited as transparent and homogeneous thin films by vacuum sublimation,and was successfully applied to electroluminescent devices with a stacked structure of indium-tin-oxide (ITO)/hole transporting layer/Eu-complex layer/hole blocking layer/electron transporting layer/cathode. The devices with this structure gave off pure red light with luminance as high as 320 cd/m2. The hole-blocking layer was essential to obtain pure red light from this Eu-complex. Without the hole-blocking layer, holes passed through the Eu-complex layer and entered into the electron transporting layer, leading to yellow emission.