The present invention relates to a method for preparing a CIS- or CIGS-based light-absorbing layer which is to be included in thin-film solar cells. More particularly, the present invention relates to a method for preparing a CIS- or CIGS-based light-absorbing layer, which can ultimately improve the efficiency of solar cells, characterized by comprising the steps of: preparing a light-absorbing ink including a precursor of copper, indium, or gallium as an organic metal precursor, and a solvent, wherein a ligand in the organic metal precursor has a keto-enol tautomeric property; and coating a substrate with the light-absorbing ink and performing a heat treatment, thereby minimizing the remaining carbon impurities of the light-absorbing layer.
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