ANALYSIS OF CURRENT-VOLTAGE CHARACTERISTICS OF ORGANIC ELECTROLUMINESCENT DEVICES ON THE BASIS OF SCHOTTKY EMISSION MECHANISM

The mechanism of hole injection from the indium-tin-oxide (ITO) electr ode into the hole-transporting layer of the organic electroluminescent (EL) device was concluded to be Schottky emission. The barrier height at the ITO/hole-transporting layer interface was determined to be abo ut 0.39 eV and the field-free current density to be 7.1 x 10(-2) Am-2 at room temperature. From the analysis of the current-voltage (I-V) ch aracteristics of the organic EL devices on the basis of the carrier in jection mechanisms, we found that the currents of the organic EL devic es having the organic bilayer structure are governed by the properties of carrier injection from the electrodes. Important information on th e potential distribution in the organic layers and the effective diele ctric constant for the carrier injection processes were also acquired from the comparison of the I-V curves with the theoretical calculation s.