Influence of the Energy Level Matching on the Performances of Organic/Polymeric Electroluminescent Devices

The performances such as the operating-voltage and the brightness of three types of devices: single-layer device, double-layer device and three-layer device, were examined. It is demonstrated that the I-V characteristics of single-layer device depends not on the applied voltage but instead on the electric-field strength, and the brightness increased by a factor of 50 and the operating-voltage decreased when introducing one electron transporting layer or an electron transporting layer and one hole blocking layer between the light emitting layer and the negative electrode. In fact, it is imperative to match the energy level of each layer in the electroluminescent device in order to improve its comprehensive performances.