Charge transport in polymer light-emitting diodes at high current density

We present measured and calculated current-voltage (I-V) characteristics of diodes fabricated using a soluble poly(p-phenylene vinylene) derivative. S teady-state and pulsed electrical excitation were used to acquire the I-V c haracteristics for current densities from 1x10(-3) to 1.3x10(3) A/cm(2). Ho le current is predominant in the diode. The I-V characteristics were fit us ing a device model that assumes an electric field-dependent hole mobility o f the Poole-Frenkel form that is independent of the charge carrier density. The measured and calculated I-V characteristics are in good agreement over the full range of current density. The maximum electric field and carrier density is about 4x10(6) V/cm and 1x10(18) cm(-3), respectively. These resu lts demonstrate that an electric field-dependent mobility, without carrier density dependence, provides an accurate description of hole transport in t his polymer over this range of field and carrier density. (C) 1999 American Institute of Physics. [S0003-6951(99)04532-5].