The sulfurization behaviour of co-evaporated Cu-In precursor films in diluted H2S atmosphere is investigated as a function of process temperature, time, post-deposition annealing and sulfur activity. The structural analysis is performed using X-ray diffraction including Rietveld's algorithm. Photoluminescence spectroscopy indicates a high electronic quality for precursors sulfurized at 400 degreesC. Lower temperatures lead to non-equilibrium effects and too high process temperatures (600 degreesC) to an electronic degradation. At medium process temperature, a prolonged sulfurization time (6 instead of 3 h) leads to a drastic increase of near-band-gap states. The use of H-2 instead of Ar as a carrier gas removes unidentified electronic states below 1.51 eV transition energy.