Patent ID: 8222517

Claim:
A solar cell comprising: a substrate; a first electrode on a surface of the substrate; a second electrode; and a plurality of photoelectric transformation units between the first electrode and the second electrode, the plurality of photoelectric transformation units including: a first photoelectric transformation unit including a first intrinsic (an i-type) semiconductor layer formed of amorphous silicon doped with at least one of carbon (C) and oxygen (O) as impurities; a second photoelectric transformation unit including a second i-type semiconductor layer formed of germanium (Ge)-doped amorphous silicon; a third photoelectric transformation unit including a third i-type semiconductor layer formed of Ge-doped microcrystalline silicon; a first interlayer between the first photoelectric transformation unit and the second photoelectric transformation unit; and a second interlayer between the second photoelectric transformation unit and the third photoelectric transformation unit, wherein the first i-type semiconductor layer, the second i-type semiconductor layer and the third i-type semiconductor layer are positioned on the surface of the substrate in the order named, and a Ge content of the third i-type semiconductor layer is less than a Ge content of the second i-type semiconductor layer, wherein the Ge content of the third i-type semiconductor layer is about 3 atom % to 20 atom % and the Ge content of the second i-type semiconductor layer is about 5 atom % to 30 atom %, and a content of the at least one content of carbon (C) and oxygen (O) doped in the first i-type semiconductor layer is about 10 atom % to 50 atom %, and a thickness of the second interlayer is greater than a thickness of the first interlayer.