Light degradation and voltage drift in polymer light-emitting diodes

It is shown that the voltage drift and light degradation in polymer light-emitting diodes are related and can be explained by the formation of traps and the modification of the space charge in the bulk of the polymer. The energy released by nonradiative carrier recombination is believed to be the driving force for the generation of traps in poly(p-phenylene vinylene) conjugated polymers. A first-approximation model is derived for the voltage drift and the light decrease during operation, which is in good agreement with experimental observations for time and current density dependencies. (C) 2001 American Institute of Physics.