Fabrication of organic superlattices structures and organic multiple quantum well electroluminescent devices

Superlattices consisting of alternating layers of organic materials have been fabricated from tris (8-hydroxyquinoline) aluminum (Alq₃) and 2-(4-biphenylyl)-5-(4-tertbutylphenyl)-1, 3, 3-oxadiazole (PBD) by a high-vacuum multisource-type organic molecular deposition. From the small-angle X-ray diffraction patterns of Alq₃/PBD superlattices, a periodically layered structure is confirmed through the entire stack. From the photoluminescence and electroluminescence measurements, it is found that the exciton energy shifts to higher energy with the decreasing Alq₃ layer thickness. The changes of the exciton energy could be interpreted as the confinement effects of exciton in the Alq₃ thin layers. Narrowing of the emission spectrum has also been observed for the electroluminescent devices with the organic multiple quantum well structure at room temperature.