A degradation study of poly(p-phenylene vinylene) based light emitting diodes

The degradation of poly(p-phenylene vinylene) (PPV) based light emitting di odes (LEDs) was examined by electrical measurements and by scanning electro n microscopy (SEM) performed on the devices after several working cycles up to their complete destruction. It is demonstrated that the stability of th e samples depends greatly on their thickness and the conduction mechanism i n the polymer film is not affected by the degradation of the diodes. In the degraded samples, dark spots are formed on the surface of the electrode in circular configuration and seem to be linked to the presence of oxygen. Th e results are compared to those obtained in organic diodes and discussed in relation with the failure mechanism. (C) 1999 Elsevier Science S.A. All ri ghts reserved.