[en] In this thesis thin layers of the system Cu-In-S were studied for the photovoltaic application by means of structural and electro-optical procedures. The effect of small quantities of group II elements on the absorber and component properties could be explained by a widely appointed study. The motivation to insert extraneous elements into CuInS₂ absorber layers results from the too low zero-current voltage of CuInS₂ based solar cells. It could be shown that by addition of small quantities of Zn and/or Mg (<1 at.%) the zero-current voltage can be increased by 90 mV. The best doped CuInS₂ solar cells aimed efficiencies, which were also determined for the reference system. As limiting factor in the doped system the zero-current has been proved. The intensive analysis of the absorber properties showed the the extraneous atoms effect in the bulk and on the surface different modifications