A Color Stable Blue Light-Emitting Device Using a Pyrazolo[3,4-b]Quinoline Derivative as an Emitter

A color stable and pure blue multilayered light-emitting device is obtained via suppressing voltage-dependent color change. Photophysical properties of a blue fluorescent organic compound 1-phenyl-3,4-dimethyl-1H-pyrazolo[3,4-b]-quinoline (PAQ5) are investigated; its highest occupied and lowest unoccupied molecular orbital levels are also measured. A multilayer electroluminescent device is fabricated using PAQ5 as an emitter dopant in a polymer matrix. The dopant has several functions in balancing injection and transport as well as bright blue light emission. The multilayered device using PAQ5 dopant substantially reduces voltage-dependent color changes, enhances the brightness of the device, and stabilizes general performance of the device. A color stable and pure blue electroluminescence with Commission Internationale de L´Eclairage (CIE) color coordinates of (x,y)=(0.168,0.100) is achieved.