Reduced reflectance cathode for organic light-emitting devices using metalorganic mixtures

Conductive light-absorbing layers made of mixtures of metals and organic materials are used as cathodes in organic light-emitting devices (OLEDs). Devices utilizing the reduced reflectance cathode, named Black Cathode™ OLEDs, demonstrate enhanced contrast even in high ambient illumination. OLEDs with a cathode made of a mixture of tris(8-hydroxyquinoline)aluminum (Alq3), Mg and Ag, or a mixture of Alq3 and Ag are addressed. Optical reflectance and absorption measurements as well as OLED electrical characterization tests are performed on various Black Cathode OLEDs and also on reference device with standard Mg:Ag cathode. The studied Black Cathode OLEDs demonstrate ∼9%–12% sun/eye-integrated reflectance (SEIR), ∼8× lower than that of the reference device, while device turn-on voltage and stability are comparable. In modified Black Cathode OLEDs, ∼1.8% SEIR has been recently realized.