The author will present the results of investigation the influence of ion irradiation on structural, chemical, and optical properties of TiO₂/SiO₂ system, which formed the basis of his dissertation work. The work is devoted to the study of processes that cause degradation of semiconductor solar cells during operation. Using noble gases ion irradiation at different energies the author has established, that the cascade mixing process is responsible for the extension of the transition layer between TiO₂ and SiO₂ contact materials that occurs dominantly toward the substrate. It was found that the mixing is not proportional to the damage amount, whereas the ion energy transfers to the target atoms create deeper damage plays a crucial role in broadening the TiO₂/SiO₂ mixed area. It was found that the concentration of TiO₂ increase after irradiation, which leads to the growth of deposited energy level in transition layers, is reflected in the enhancement of mixing amount. The nonlinear extreme behaviour of the optical properties of the TiO₂/SiO₂ contact after irradiation has been established. In particular, it was shown that the refractive index and the extinction coefficient of TiO₂/SiO₂ contact increase at the energy of implanted ions below 250 keV and decrease at the energy of implanted ions higher than 250 keV.