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

Abstract

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 1.5nm 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 0.55cd∕A and a power efficiency of 0.07lm∕W have been reached.