Mixing effect of chelate complex and metal in organic light-emitting diodes

Organic light-emitting diodes using thin film dispersing a hole transport material into a soluble polyimide as a hole transport layer and the sublimed molecular film of a chelate complex as an emissive layer were fabricated. In order to improve the injection of electrons into the emissive layer as well as the durability of devices, we have attempted mixing the chelate complex and metal between the emissive layer and the cathodic electrode. The charge injection of the device with the mixed layer was initialized at an applied voltage of 4.19 V, It was observed from the electroluminescent spectra that the oscillator strength was dramatically enhanced with the applied voltage. (C) 1998 American Institute of Physics. [S0003-6951(98)04214-4].