A photovoltaic device includes: a back electrode; a transparent front electrode; a p-type semiconductor layer disposed between the transparent front electrode and the back electrode and made from a first semiconductor compound including M1, M2, and A1, the p-type semiconductor layer having a M1/M2 atomic ratio; and an n-type layered structure disposed between the p-type semiconductor layer and the transparent front electrode and cooperating with the p-type semiconductor layer to form a p-n junction therebetween. The n-type layered structure includes an n-type semiconductor layer made from a second semiconductor compound including M3, M4, and A2 and having a M3/M4 atomic ratio less than the M1/M2 atomic ratio and greater than 0.1 and less than 0.9.