White-light-emitting diodes using miscible polymer blend doped with phosphorescent dye

Abstract

We demonstrate that voltage-independent and highly efficient white light-emitting diodes (WLED) can be obtained based on phosphorescent dye-doped conjugated polymer blend films. Conjugated polymers are used as the blue and green emitters, as well as the energy host, and a phosphorescent dye is used as the red emitter and guest material. The phase-separation between the conjugated polymers is suppressed by blending miscible polymer and copolymer having the same moiety. Therefore, we expect that efficient Forster-type energy transfer occurs through this homogeneous morphology. By introducing the copolymer into the emissive layer to enhance its miscibility, we obtained a voltage-invariant white emission from the polymeric LEDs. The luminous efficiency of the WLED with the single active layer is increased dramatically by introducing the phosphorescent dopant as a red emitter. (C) 2011 Elsevier B.V. All rights reserved.