The quantum efficiency and lifetime of fluorescence of an aluminum-hydroxyquinoline (Alq 3 ) complex in solution increased with decreasing polarity of the solvent. Similarly, the fluorescence quantum efficiency and lifetime of Alq 3 films were increased by mixing the complex with a compound with a low dielectric constant. These results suggested that the nonradiative decay process of Alq 3 is retarded in less polar media. The quantum efficiency and lifetime of fluorescence of Alq 3 films were 20 AE 2% and 17 ns, respectively. When Alq 3 was mixed with a less polar substance in the film state, the quantum efficiency and lifetime were increased to 25 AE 2% and 20 ns, respectively. These results indicate that the nonradiative decay process in the film state is also retarded as the polarity decreases. Using a film consisting of Alq 3 and a compound with a low dielectric constant as the light emitting layer of organic electroluminescence devices, the luminance efficiency was increased by about 20%.
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