Disclosed is a thin film solar cell including a substrate, a first electrode, a light absorbing layer, a buffer layer, a window layer, and a second electrode, wherein a compound layer of MxSy or MxSey (here, M is metal, and x and y each are a natural number) is present in an interface between the first electrode and the light absorbing layer, the thickness of the compound layer of MxSy or MxSey being 150 nm or less.
