Device characteristics of polymer light-emitting diodes

A model describing the device characteristics of polymer light-emitting diodes (PLEDs) is presented. The recent observation that in poly(p-phenylene vinylene) (PPV) the hole current is space-charge-limited whereas the electron current is strongly reduced by traps is taken into account. It is calculated that such an unbalanced electron and hole transport gives rise to a bias dependent efficiency. By comparison with experiment it is found that the recombination process in PPV is mainly non-radiative. Only 5% of the total number of recombinations contributes to the light-output of the PLED.