Current injection from a metal to a disordered hopping system. III. Comparison between experiment and Monte Carlo simulation

We have performed electric-field and temperature-dependent electron injecti on studies in an aluminum/tris(8-hydroxy-quinolinolato) aluminum/magnesium: silver single-layer organic light-emitting diode. Analysis of the observed injection currents in terms of the classic Fowler-Nordheim (FN) tunneling o r Richardson-Schottky (RS) thermionic emission proved to be inadequate. Whe reas, the FN-type behavior at high-electric fields must be considered accid ental, the injection currents qualitatively resemble those of the RS concep t. However, quantitative differences are observed concerning the RS coeffic ient, the prefactor current, and the temperature dependence. On the other h and, the experimental data are in excellent agreement with a recently prese nted Monte Carlo simulation [U. Wolf et al., Phys. Rev. B 59, 7507 (1999)] of carrier injection from a metal to an organic dielectric with random hopp ing sites.