Electrode versus space-charge-limited conduction in organic light-emittingdiodes

A criterion is established to distinguish electrode limited charge injectio n from a metal into a random organic dielectric from space charge limited c urrent flow. The crucial material parameters are the charge carrier mobilit y and the zero field injection barrier. It rests upon parametrizing the inj ection current as a function of electric field, temperature, and injection barrier by mutual adjustment of the electron current injected across a Mg:A g\Alq(3) electrode on the one hand and Monte Carlo simulation of the inject ion yield for a hopping system on the other hand. (C) 1999 American Institu te of Physics. [S0003-6951(99)00340-X].