Electroluminescence from polyurethanes with emissive and charge-transporting chromophores and their blends

Polyurethanes with a diphenylamino-substituted 1,4-bisstyrylbenzene unit for an emissive and charge-transport chromophore were prepared. Single-layer electroluminescent (EL) diodes were made of spin-coated polyurethane films. An indium-tin-oxide (ITO) anode and a magnesium-silver alloy cathode were used. The EL diode made of the polyurethane exhibited the maximum luminance of 35 cd/m2 at 570 mA/cm2 at applied voltage of 26 V. When cyano groups were attached to the 1,4-bisstyrylbenzene unit, the maximum luminance of 1000 cd/m2 for 870 mA/cm2 at voltage of 26 V was attained. The external quantum efficiency of the latter device was calculated to be 0.035%. The emission peaks of these two devices were 505 and 590 nm. Two polyurethanes were found to be mixed homogeneously and EL diodes were fabricated using blend films.