Diethylselenide [(C2H5)(2)Se: DESe] was shown to be a promising less-hazardous alternative source for the preparation of CuInSe2 films for solar cell applications by the selenization of Cu-In and Cu-In-O precursors. Approximately 1.5 mum thick, single-phase, polycrystalline CuInSe2 films having grain size of approximately 1-2 mum were formed on Mo-coated soda-lime glass substrates at temperatures between 450degrees and 550degreesC. Slightly In-rich films exhibited a distinct contribution by excitonic absorption in the absorption spectra at 90 K. Photoluminescence spectra at low temperatures were dominated by characteristic bands at 0.97 and 0.90 eV, showing that the films are a suitable material for the photo-absorbing layer of CuInSe2-based solar cells. (C) 2002 Elsevier Science B.V. All rights reserved.