HEIGHT OF THE ENERGY BARRIER EXISTING BETWEEN CATHODES AND HYDROXYQUINOLINE-ALUMINUM COMPLEX OF ORGANIC ELECTROLUMINESCENCE DEVICES

The properties of organic electroluminescence devices are largely affe cted by the kind of metals used as the cathode, because the barrier he ight formed at the interface depends on the electronic and chemical pr operties of the metals. On the basis of the temperature dependence of currents flowing through the interface between tris(8-hydroxyquinolino )aluminum and a magnesium cathode, the carrier injection mechanism at the interface was ascribed to the thermionic emission with the barrier height of about 0.58+/-0.03 eV at zero electric field. The barrier he ight became larger when metals with larger work functions were used as the cathode. The current density was also found to be dependent on th e chemical structure of the interfaces. (C) 1996 American Institute of Physics.