Polymer Light-Emitting Diodes with Single- and Double-Layer Structures Using Poly(2,3-diphenylquinoxaline-5,8-diyl)

A light-emitting diode (LED) using poly(2,3-diphenylquinoxaline-5,8-diyl) (PdPhQx) as the light-emitting material, ITO/PdPhQx/MgAg, emits blue-green (490 nm) light. Introduction of hole transporting layers such as vacuum-deposited or spin-coated thin layers of poly(thiophene-2,5-diyl), poly( p-phenylene), and poly(N-vinylcarbazole) between ITO and PdPhQx in the LED enhances electroluminescence efficiency by about two orders of magnitude. Addition of a diaryldiamine (TPD) in the PdPhQx layer causes a red shift of the emitted light to 565 nm due to formation of an exciplex between PdPhQx and TPD.