Origin of the enhanced space-charge-limited current in poly( p -phenylene vinylene)

It is demonstrated that the enhancement of the space-charge-limited (SCL) hole current of poly($p$-phenylene vinylene) (PPV) derivatives at high bias at room temperature is due to the carrier density dependence of the hole mobility. Contrary to numerous reports the dependence of the mobility on the electric field is only observed at low temperatures. Analysis of the hole transport without taking into account the charge carrier density dependence of the mobility leads to an incorrect charge carrier and electric field distributions in organic light-emitting diodes.