Efficient, low operating voltage polymer light-emitting diodes with aluminum as the cathode material

Efficient polymer electroluminescent (EL) devices have been fabricated using stable metals such as aluminum (Al) as the cathode material. These light-emitting diodes are fabricated with ITO as the anode, a soluble dialkoxy-PPV containing an appropriate surfactant additive as the EL polymer and Al as the cathode. The external quantum efficiency (QE) is above 2%, comparable with control devices (without the additive) with calcium as the cathode material. These Al cathode devices show promising stress life. Enhancements in the QE are also found for other EL polymers which emit blue, green, yellow and red light.