In(OH)(x)S-y buffer layers have been deposited on glass/Mo/CIGS substrates. Composition, reflectance and morphology of those heterojunctions have been studied. The XPS results have shown that the CIGS substrate does not influence the buffer layer composition, which only depends on deposition conditions. Nevertheless, strong variations of CIGS total reflectance take place after the deposition of this buffer layer. It has been also observed that the In(OH)(x)S-y layer shapes the CIGS substrate and totally covers its surface.