Organic electroluminescent devices having metal complexes as cathode interface layer

We developed novel cathode systems, composed of metal complexes, for organic electroluminescent (EL) devices. Alkaline metal complexes, such as mono(8-quinolinolato) lithium (Liq), were used as a cathode interface layer in combination with metallic Al as a cathode material. Similarly, doping the organic electron-tran sporting layer with alkaline metal complexes was also effective in facilitating the electron injection from the cathode to the organic layer, which results in reducing the drive voltage. In,both cases, we assume that alkaline metal ions in the complexes are reduced to free metal by thermally activated Al. Then, the free alkaline metal reacts with electron-transporting materials, forming the radical anions, which facilitate electron injection from the Al cathode.