NOVELTY - A copper-indium-gallium-selenide thin film solar cell includes light absorption layer containing copper, indium, gallium, selenium, or sulfur. It is formed by coating or printing an ink (101) that contains copper-selenium-sulfur nanoparticles and (indium, gallium)(selenium-sulfur) nanoparticles on a rear electrode (103) of the cell.    USE - Copper-indium-gallium-selenide (CIGS) thin film solar cell as main power source for electronic clock, radio set, unmanned light house, satellite, or rocket.    ADVANTAGE - The CIGS thin film solar cell includes CIGS thin film formed by only a printing process on an ink containing nanoparticles without requirement of alternative vacuum processing or complex equipment.    DETAILED DESCRIPTION - A copper (Cu)-indium (In)-gallium (Ga)-selenide (Se) (CIGS) thin film solar cell comprises light absorption layer containing Cu, In, Ga, Se or sulfur (S). It is formed by coating or printing an ink that contains Cu2(Se1-xSx) nanoparticles and (In, Ga)2(Se1-ySy)3 nanoparticles on a rear electrode of the cell.    x, y=0-1.    INDEPENDENT CLAIMS are included for:    (1) an ink for forming thin film for solar cell prepared by mixing Cu2(Se1-xSx) nanoparticles, (In, Ga)2(Se1-ySy)3 nanoparticles or In2(Se1-zSz)3 nanoparticles in an organic solvent;    (2) a method of making an ink for forming thin film for solar cell, comprising mixing Cu2(Se1-xSx) nanoparticles, (In, Ga)2(Se1-ySy)3 nanoparticles or In2(Se1-zSz)3 nanoparticles in the organic solvent, and heating the mixture while adding a dispersant; and    (3) a method for manufacturing CIGS thin film solar cell, comprising coating or printing an ink that contains Cu2(Se1-xSx) nanoparticles, (In, Ga)2(Se1-ySy)3 nanoparticles or In2(Se1-zSz)3 nanoparticles on a rear electrode formed on a substrate; and heating the ink to form a light absorption layer.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a CIGS thin films.    Ink (101)    Substrate (102)    Rear electrode (103)