<Original Papers>Improvement in degradation of organic electroluminescent devices by pre-operation

The organic light-emitting diodes (OLEDs) with multi-layers structure were operated at the constant driving voltage in pre-operation mode. The life-time of the OLED in pre-operation driving mode was seven times longer than that in standard operation mode. The degradation characteristics of OLEDs were less dependent on the reduction of the emission area by the generation of dark spot. The improvement in the degradation would be relation to the changes of the carrier injection and/or transportation in the organic layers，which were caused by the heat-generation under the pre-operation driving