White polymer light-emitting devices from ternary-polymer blend with concentration gradient

We have fabricated a white polymer light-emitting-diode bilayer structure that contains a ternary polymer blend. The first layer of poly(9-vinylcarbazole) acts as an energy donor and electron blocker, and the second layer comprising an immiscible polymer blend of two light-emitting polymers, poly(9,9'-dihexylfluorene-2,7-divinylene-m-phenylenevinylene-stat-p-phenylenevinylene) and poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene), emits light. The emissive white color of the device was observed to be practically independent of the driving voltage (near CIE coordinate; 0.33, 0.33). In addition, it shows greatly enhanced luminous efficiency compared to a ternary blended white light-emitting-diode. (C) 2005 Elsevier B.V. All rights reserved.