Thermodynamic analysis of heterogeneous chemical reaction in (CuxIn1−xSeYO1−y)(solid)-InCl3(aqueous solution)-system has been carried out. Enrichment of thin films with indium up to 7.6 atomic % in Cu2Se-In2Se3-system has been carried out by the method of ion-exchange substitution. The obtained layers have been investigated by the methods of X-ray analysis and raster electronic microscopy. The dependence of a composition and morphology of the films from duration of a contact of CuxIn1−xSeYO1−y film with indium salt solution has been established.