A solar cell of the present invention comprises a p-type semiconductor layer, an n-type semiconductor layer, and a superlattice semiconductor layer interposed between the p-type semiconductor layer and the n-type semiconductor layer, wherein the superlattice semiconductor layer has a superlattice structure in which barrier layers and quantum dot layers comprising quantum dots are stacked alternately and repeatedly, and is formed so that the bandgaps of the quantum dots are gradually widened with increasing distance from a side of the p-type semiconductor layer and decreasing distance to a side of the n-type semiconductor layer.