NOVEL STRUCTURE OF ORGANIC ELECTROLUMINESCENCE CELLS WITH CONJUGATED OLIGOMERS

Organic electroluminescence (EL) cells with a novel structure, ITO/semiconducting oligothiophene layer/oligophenylene layer/emitting layer/Mg:Ag, were studied. The oligothiophene layer enhanced hole injection and hole transport into the emitting layer (EML), while the oligophenylene layer achieved electron confinement in EML by electron blocking. In addition, we found that the oligophenylene layer inhibited energy transfer from EML to the oligothiophene layer and played an important role in increasing the luminous efficiency. For our fabricated EL cell with tris(8-hydroxyquinoline)aluminum as an emitting molecule, we succeeded in obtaining bright emission over 2000 cd/m2 at a voltage of about 10 V.