Towards Color Stable Blue Primary for Displays: Suppress Field-Dependent Color Change in a Multilayered Electroluminescent Device

A blue fluorescent organic compound, 1-phenyl-3,4- dimethyl-1H-pyrazolo[3,4-b]quinoline (PAQ5), is a suitable emitter to enable a color stable blue emission from multilayered light emitting devices. The dopant PAQ5 functioned as an energy trap and an emitter having its HOMO/LUMO levels lying inside the band gap of the host to secure an efficient energy transfer; it also reduced barrier height for electron injection and improved electron transporting of the emitting layer. It lowered the turn-on electric field and enhanced luminance gradually as the dopant concentrations increased. A bright and color stable blue emission having CIE (x,y) = (0.168, 0.100) was obtained. Field-dependent color change of such multilayered devices within a wide range of driving electric fields was suppressed by PAQ5 dopant. A color purity of 0.815 was achieved.