ORGANIC ELECTROLUMINESCENT DEVICES HAVING DERIVATIVES OF ALUMINUM-HYDROXYQUINOLINE COMPLEX AS LIGHT-EMITTING MATERIALS

Derivatives of aluminum-hydroxyquinoline complex were synthesized and used as light emitting materials for electroluminescent devices. The a bsorption and photo-luminescence spectra, and also the energy levels o f the derivatives were shifted from those of the mother compound by el ectron-withdrawing and electron-releasing groups introduced into the h ydroxyquinoline ligands. Using these compounds, the relationship betwe en the electroluminescence efficiency and the energy levels was analyz ed. The results strongly suggest that part of the injected electrons a nd holes recombine across the interface of the stacked organic layers, the process being non-emissive. It was also observed that the current -voltage curves shift toward the lower voltages as the electron accept ing energy level of the light emitting material becomes lower.