NOVELTY - The method comprises forming a copper-indium-gallium alloy layer on a first electrode layer (14) by direct current sputtering using a copper-indium-gallium alloy target, forming an alkali layer containing sodium on the copper-indium-gallium alloy layer, and subjecting the copper-indium-gallium alloy layer to a selenization treatment for converting the copper-indium-gallium alloy to the chalcopyrite-type compound to obtain the light absorbing layer. The light absorbing layer is interposed between first and second electrode layers, which are formed on an upper side of a surface of a substrate.    USE - The method is useful for producing a chalcopyrite-type solar cell.    ADVANTAGE - The method prevents the separation of light absorbing layer thus efficiently, economically and rapidly producing the chalcopyrite-type solar cell with fewer interface defects, excellent current-voltage characteristics and quantum efficiency and a higher conversion efficiency and without the replacement process.    DETAILED DESCRIPTION - The method comprises forming a copper-indium-gallium alloy layer on a first electrode layer (14) by direct current sputtering using a copper-indium-gallium alloy target, forming an alkali layer containing sodium on the copper-indium-gallium alloy layer, and subjecting the copper-indium-gallium alloy layer to a selenization treatment for converting the copper-indium-gallium alloy to the chalcopyrite-type compound to obtain the light absorbing layer. The light absorbing layer is interposed between first and second electrode layers, which are formed on an upper side of a surface of a substrate. The copper-indium-gallium alloy target has a copper-indium-gallium composition satisfying the inequalities of 0.7 less than or equal to Cu/(In+Ga) less than or equal to 0.99 and 0.4 less than or equal to Ga/(In+Ga) less than or equal to 0.7. The alkali layer is formed by applying an aqueous solution containing alkali metals onto the copper-indium-gallium alloy layer and the then drying the applied solution, and by immersing a partially-processed product having the copper-indium-gallium alloy layer in the aqueous solution containing alkali metals and then drying the applied solution.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic side view of a chalcopyrite-type solar cell.    Chalcopyrite-type solar cell (10)    Glass substrate (12)    First electrode layer (14)    Light absorbing layer (16)    Buffer layer (18)    Transparent second electrode layer. (20)