This research activity is aimed to research of thin-film technologies for production of anorganic and organic solar cells and development of diagnostic methods aimed at improving the structure of photovoltaic solar cells and enhancement of their properties. The research is partly focused on thermovoltaics where absorber and radiators transform light solar radiation from a wideband to narrow band spectrum to increase the total conversion efficiency. The diagnostic studies are focused on utilization of luminescence methods for analysis of cells and panels. New technologies and diagnostic methods should help to achieve a higher total conversion efficiency of solar energy conversion into electrical energy.