Comparison of Electroluminescence and Photoluminescence Efficiencies of Organic Electroluminescent Devices Having a Bilayer Structure

The recombination processes of electrons and holes injected into the tris(8-hydroxyquinolino)aluminum (ALQ) layer of organic electroluminescent (EL) devices having the ALQ/diamine biller structure were studied. From the comparison of the EL and PL (photoluminescence) emissions, the quantum efficiency of EL under the normal operational conditions was estimated to be about 0.12 times that of PL. Experimental results suggested the occurrence of nonemissive electron-hole recombination processes at the ALQ/diamine interface.