Electroluminescence in Organic Films with Three-Layer Structure

We have succeeded in the fabrication of a stable organic electroluminescent (EL) device with a three-layer structure; hole transport layer/emitting layer/electron transport layer. The EL device was prepared by vacuum evaporation. Efficient carrier double injection into the emitting layer was realized by the use of separate hole and electron transport layers. Bright EL emission was observed in a darkened room at the dc bias voltage of 50 V. Stable emission lasted for more than five hours at this condition. The emission spectrum could be changed with variation of the organic material for the emitting layer.