NOVELTY - Producing silver-copper-indium-gallium-selenium-based thin film, comprises (a) mixing nanoparticles having selenium core (10) and silver selenide shell (20), multicomponent nanoparticles containing copper-indium-gallium-selenium-based component, precursor solution containing copper-indium-gallium-selenium-based component, alcohol solvent and binder to prepare slurry, (b) performing non-vacuum coating of the prepared slurry on film to form silver-copper-indium-gallium-selenium-based thin film, and (c) heat treating selenide on the formed silver-copper-indium-gallium-selenium-based thin film.    USE - The method is useful for producing silver-copper-indium-gallium-selenium-based thin film for light absorbing layer of tandem solar cells in top cell (all claimed).    ADVANTAGE - The method produces silver-copper-indium-gallium-selenium-based thin film at low temperature in cost-efficient manner.    DETAILED DESCRIPTION - Producing silver-copper-indium-gallium-selenium-based thin film, comprises (a) mixing nanoparticles having selenium core (10) and silver selenide shell (20), multicomponent nanoparticles containing copper-indium-gallium-selenium-based component, precursor solution containing copper-indium-gallium-selenium-based component, alcohol solvent and binder to prepare slurry, (b) performing non-vacuum coating of the prepared slurry on film to form silver-copper-indium-gallium-selenium-based thin film, and (c) heat treating selenide on the formed silver-copper-indium-gallium-selenium-based thin film, or coating slurry comprising precursor solution containing copper-indium-gallium-selenium-based component, multicomponent nanoparticles containing copper-indium-gallium-selenium-based component and nanoparticles having selenium core and silver selenide shell, alcohol solvent and binder on the film. The multicomponent nanoparticles are two, three or four component nanoparticles. The binder comprises chelating agent and non-chelating agent. An INDEPENDENT CLAIM is also included for the thin film prepared by the above method.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the nanoparticles having selenium core and silver selenide shell.    Selenium core (10)    Silver selenide shell (20)