Tris(8-hydroxyquinoline) aluminum (Alq(3)) Used as light-emitting layer in electroluminescent (EL) devices, has been synthesized. The thin films have been deposited by thermal evaporation on quartz and silicon substrates. The optical constants of Alq3 films have been determined using, spectroscopic ellipsometry (SE) over a wide spectral range. The influence of light exposure on the optical properties of Alq3 films has been studied using ellipsometry, photoluminescence and infrared spectroscopies. We find the structural modification in Alq3 films as indicated by the refractive index and absorption coefficients after exposure to light in air ambient. (c) 2004 Elsevier B.V. All rights reserved.