A structure of photovoltaic cell for improving conversion efficiency has been disclosed, including a first bandgap layer, a second bandgap layer, a third bandgap layer, a back electrode and a finger electrode, wherein the first bandgap layer is a wafer while the second bandgap layer is a semiconductor film with a thickness of 1˜100 Å and a greater bandgap than one of the first bandgap layer, and the third bandgap layer comprises wide bandgap materials and a greater bandgap than one of the second bandgap layer. Thereby, the lattice mismatch of heterostructures between the first bandgap layer and the third bandgap layer may be solved by the second bandgap layer. Also, the carrier recombination within devices may be decreased and the output photocurrent may thus be enhanced to improve energy conversion efficiency.