A top-emission organic light-emitting diode with a silicon anode and an Sm/Au cathode

A top-emission organic light-emitting diode (TEOLED) with a p-type silicon anode and a semitransparent samarium/gold cathode has been constructed and studied. With a structure of Al/p-Si/SiOx/N,N-'-bis-(1-naphthl)-diphenyl-1,1'-biphenyl-4,4'-diamine(NPB)/Tris-(8-hydroxyquinoline)aluminum(Alq)/LiF/Al, we have found that compared to indium-tin-oxide, the p-Si anode enhances the unbalance between electron- and hole-injection, which is a disadvantage factor for the light-emitting efficiency of the TEOLED. Selecting p-Si wafers with suitable electric resistivities and inserting an ultrathin low temperature grown SiOx layer of about 1.5 nm between the anode and NPB can effectively restrict hole-injection. Moreover, a low work function Sm/Au cathode was used to enhance electron-injection. The electroluminescence efficiency of the TEOLED depends on the thickness of the Sm layer in the cathode. A current efficiency of 0.55 cd/A and a power efficiency of 0.07 lm/W have been reached. (C) 2004 American Institute of Physics.