Spontaneous and reverse-bias induced recovery behavior in organic electroluminescent diodes

Double-layer organic electroluminescent diodes composed of a spin-coated polyvinylcarvbazole layer and a vacuum-sublimed tris-(8-hydroxyquinoline)aluminum layer were prepared. The diodes were driven at constant voltage and were also kept under short-circuit or reverse-bias conditions. Observations of luminance-current density-voltage relations at constant voltage driving were repeated. The decrease of both luminance and current density during constant voltage driving was observed. Both spontaneous and reverse-bias assisted recoveries of device performances were observed, and these degradation and recovery phenomena were discussed in terms of the movement of ionic impurities in organic layers.