Space-charge-limited electron currents in 8-hydroxyquinoline aluminum

We investigate electron injection and transport in single-layer devices of 8-hydroxyquinoline aluminum sandwiched between two electrodes. Electrodes c omprising a thin lithium fluoride layer are compared with co-evaporated mag nesium-silver cathodes and with pure aluminum cathodes. By employing both t ransient and quasistatic current measurements, the impact of the LiF-layer thickness on electron injection is investigated. It is demonstrated that co ntacts comprising 0.1-0.2 nm LiF and an aluminum capping layer are able to sustain space-charge-limited currents in 8-hydroxyquinoline aluminum. Furth er, steady-state current-voltage measurements as a function of temperature are discussed with respect to trap distributions in 8-hydroxyquinoline alum inum. (C) 2000 American Institute of Physics. [S0003-6951(00)00101-7].