Structural and optical properties of In-rich Cu-In-Se polycrystalline thin films (0.54 < In/ (Cu + In) < 0.78) prepared by chemical spray pyrolysis (CSP) on glass substrate have been systematically studied in terms of In/(Cu + In) ratio. Lattice constants a and c of the films decrease with increase of In/(Cu+In) ratio. The films exhibit a characteristic Raman peak shifting higher frequencies as the In/(Cu + In) ratio increases. Optical bandgap energy is approximately 1.22 eV for 0.54 < In/(Cu + In) < 0.67, but increases from 1.22 to 1.36 eV when the In/(Cu+In) ratio increases from 0.67 to 0.78. Photoacoustic measurements reveal the existence of high concentration of nonradiative centers introduced by the deviation from the stoichiometric composition. (c) 2005 Elsevier B.V. All rights reserved.