Organic Light-Emitting Devices Using Common Uneven Aluminum-Foil as the Electrode

Here, we report the fabrication of organic light-emitting devices (OLEDs) using common uneven aluminum-foil as the electrode substrates, which show surface roughness of several hundred nanometers. In general, the use of such uneven electrodes causes serious electric leakage due to the application of ununiform electric field, resulting in improper operation of OLEDs. In this work, extraordinary thick phosphotungstic acid (H₃PW₁₂O₄₀) (PWA) buffer layer of several hundred nanometers was used for the mitigation of the ununiform electric field. PWA showed the property of negative differential resistance (NDR), and the property contributed to the realization of both of the low driving voltage and the suppression of the leakage currents. The origin of the NDR was also investigated by various analytical methods. We applied PWA to the OLEDs using aluminum-foil electrode substrates, and obtained leak-free OLEDs with uniform luminance images. Large area OLEDs with a light-emitting area of 64 cm² were fabricated. Even in crumpled and torn states, they emitted steady luminescence.