High-purity white light from a simple single dopant host-guest white organic light-emitting diode architecture

White light with good color properties (color rendering index=82–87) is generated in a simple organic light-emitting diode comprising an emissive layer, composed of an undoped tris(4-methyl-8-quinolinato)aluminum (Almq3) sublayer and region doped with an orange-red phosphorescent dopant, bis(2-phenyl-1-quinoline)iridium acetylacetonate (Ir(pq)2acac). Electron-hole recombination in a thin spacing Almq3 layer results in blue-green fluorescence, while the formed triplet excitons diffuse to the doped region and are harvested by the dopant to emit orange-red phosphorescence. The combination of blue-green and orange lights results in warm white light. This approach takes advantage of efficient migration of triplet excitons while being less demanding in terms of fabrication and color matching.