Top-emitting polymer light-emitting diodes with environmentally stable cathodes

We report the demonstration of polymer-based top-emitting diodes that employed environmentally stable cathode materials. The device employed an emissive polymer blend that we reported previously [Deng Appl. Phys. Lett. 84, 3522 (2004)]. By constructing a semitransparent cathode using the stable metals Al and Ag, bright light emission through the top cathode was achieved. An index-matching overlayer deposited by spin coating was shown to enhance the transmission efficiency through the top electrode. Microcavity effects were observed for the device by replacing the indium tin oxide anode with Au, resulting in wavelength tunability of the device.