NOVELTY - A photovoltaic device comprises a first transparent conductive oxide layer (110); and a photoelectric conversion unit having a p-type amorphous silicon bi-layer. The p-type amorphous silicon bi-layer comprises a heavily doped p-type amorphous silicon layer and a p-type amorphous silicon layer (122). The heavily doped p-type amorphous layer is in contact with the first transparent conductive oxide layer.    USE - A photovoltaic device, particularly a solar cell.    ADVANTAGE - The photovoltaic device has improved efficiency and reduced cost; and is more efficient since the photovoltaic device captures a larger portion of the solar radiation spectrum.    DETAILED DESCRIPTION - The photoelectric conversion unit further comprises an intrinsic type amorphous silicon layer (124) over the p-type amorphous silicon bi-layer; and an n-type amorphous silicon layer (136) or an n-type microcrystalline silicon layer (126) over the intrinsic type amorphous silicon layer. The photovoltaic device further comprises a heavily doped n-type amorphous silicon layer disposed in contact with a second transparent conductive oxide layer and the n-type amorphous silicon layer; and an n-type amorphous silicon buffer layer formed between the intrinsic type amorphous silicon layer and the n-type microcrystalline silicon layer. The heavily doped p-type amorphous silicon layer has a dopant concentration of 1020-1021 atom/cm3. The p-type amorphous silicon layer is a silicon carbon layer. A p-type microcrystalline silicon layer (132) is in contact with the first transparent conductive oxide layer. An intrinsic type microcrystalline silicon layer is formed over the p-type microcrystalline silicon layer. An INDEPENDENT CLAIM is included for a method of forming a thin film solar cell (100) over a substrate (102).    DESCRIPTION OF DRAWING(S) - The drawing is a schematic diagram of a thin film multi-junction solar cell oriented toward the light or solar radiation.    Thin film solar cell (100)    Substrate (102)    First transparent conductive oxide layer (110)    P-type amorphous silicon layer (122)    Intrinsic type amorphous silicon layer (124)    N-type microcrystalline silicon layer (126)    P-type microcrystalline silicon layer (132)    Intrinsic type microcrystalline silicon layer (134)    N-type amorphous silicon layer (136)