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. Steady-state and pulsed electrical excitation were used to acquire the I–V characteristics for current densities from 1×10−3 to 1.3×103 A/cm2. Hole current is predominant in the diode. The I–V characteristics were fit using a device model that assumes an electric field-dependent hole mobility of 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 4×106 V/cm and 1×1018 cm−3, respectively. These results demonstrate that an electric field-dependent mobility, without carrier density dependence, provides an accurate description of hole transport in this polymer over this range of field and carrier density.