Highly transparent cathodes comprised of rare earth and Au stacked layers for top-emission organic light emitting diodes

We report the transparent cathodes comprised of a low work function rare earth element (RE) and a Au capping layer for top-emission organic light emitting diodes (TOLEDs). The Sm/Au, Yb/Au, Gd/Au, and Dy/Au cathodes possess a transmittance up to similar to 60% when the RE/Au thickness is 5/10 nm. The light extraction efficiencies for the TOLEDs with a silicon anode and a RE/Au cathode are computed to be 9%-13%, markedly higher than that for a similar device but with an Al/Au cathode. The surface plasmon polaritons at the Yb(or Sm)/Au cathode are found to be much weaker than those at the Al/Au cathode. (c) 2006 American Institute of Physics.