Highly enhanced electron injection in organic light-emitting diodes with an n-type semiconducting MnO2 layer

Highly enhanced electron injection is demonstrated with a thin manganese dioxide (MnO2) electron injection layer (EIL) in Alq(3)-based organic light-emitting diodes. Insertion of the MnO2 EIL between the Al cathode and Alq(3) results in highly improved device characteristics. In situ photoelectron spectroscopy shows remarkable reduction of the electron injection barrier without significant chemical reactions between Alq(3) and MnO2, which could induce Alq(3) destruction. The reduction of the electron injection barrier is due to the n-type doping effect, and the lack of strong interfacial reaction is advantageous with regards to more efficient electron injection than a conventional LiF EIL. These properties render the MnO2, a potential EIL. (C) 2012 Elsevier B. V. All rights reserved.