Degradation and failure of organic light-emitting devices

The degradation and failure of organic light-emitting device are observed via optical microscopy. The "degraded area" has been identified to be made up of three regions: (1) a dark spot at the center, (2) a nonemitting area forming the core, and (3) a weakly emitting area surrounding the core. It is found that due to metal migration, as evidenced from the secondary ion mass spectrometry profiles, the indium tin oxide/polymer interface roughens during operation. The intense local current at sharp points degrades the polymer causing the formation of the dark center. Further current stress caused the central core to carbonize which may lead to short and/or open circuits accompanied by fluctuations in the device current. (C) 2002 American Institute of Physics.