交互積層型有機発光素子の発光機構の検討と発光モデルの提案

抄録

The authors prepared organic light-emitting-diodes (organic LEDs) alternately deposited with diamine derivative (TPD) and aluminum quinoline (Alq3) and studied electroluminescence (EL) and photoluminescence (PL) properties using the dye-doping method. The actual emitting region of the specimen was found to be in some, not all, of the emission layers near the cathode. It shifted from the emission layer beside the cathode to one beside the anode depending on applied current, and it extended over several emission layers with the increase of current. EL spectra of the specimens with dyedoped emission layers did not have the effect of alternate deposition: the narrower FWHM of EL spectrum and the shorter emission peak than conventional organic LED with double layer. Considering the electron injection dependence of the emitting region and the contribution of the region beside the anode of narrower emission layer, the carrier recombination in TPD layer was concluded to play an important role of EL mechanism. The measurement of fluorescence lifetime directly proved the energy transfer from TPD to Alq3. The authors proposed the new model of EL mechanism incorporated the idea above.