NOVELTY - The photovoltaic device comprises a substrate (102) having a first surface and a second surface, a barrier layer disposed on the first surface of the substrate, a first transparent conductive oxide layer disposed on the barrier layer, a conductive contact layer disposed on the first transparent conductive oxide layer, a first p-i-n junction formed on the conductive contact layer, a second transparent conductive oxide layer formed over the first p-i-n junction, an antireflection coating layer disposed on the second surface of the substrate, and a heavily doped p-type amorphous silicon.    USE - Used as a photovoltaic device such as a thin film solar cell.    ADVANTAGE - The photovoltaic device can be economically manufactured with high conversion efficiency, fill factor and open circuit voltage, increased short circuit current and improved light absorption properties and performance.    DETAILED DESCRIPTION - The photovoltaic device comprises a substrate (102) having a first surface and a second surface, a barrier layer disposed on the first surface of the substrate, a first transparent conductive oxide layer disposed on the barrier layer, a conductive contact layer disposed on the first transparent conductive oxide layer, a first p-i-n junction formed on the conductive contact layer, a second transparent conductive oxide layer formed over the first p-i-n junction, an antireflection coating layer disposed on the second surface of the substrate, a heavily doped p-type amorphous silicon, an interface barrier layer, a second p-i-n junction formed between the first p-i-n junction and the second transparent conductive oxide layer, a conductive index matching layer disposed between the second p-i-n junction and the second transparent conductive oxide layer, and a metal back electrode formed on the second transparent conductive oxide layer. The conductive contact layer comprises a tin oxide layer, a titanium oxide layer, a tantalum layer, a tantalum oxide layer, a niobium doped tin oxide layer or a niobium doped titanium oxide layer. The antireflection coating layer is fabricated from a silicon containing material having carbon dopants and/or fluorine dopants, and includes a film stack having a silicon oxide layer and a titanium oxide layer. The first p-i-n junction comprises: a p-type amorphous silicon layer (110); an intrinsic type amorphous silicon layer; and a n-type microcrystalline silicon carbide layer. The heavily doped p-type amorphous silicon is formed on the conductive contact layer prior to the formation of the p-type amorphous silicon layer. The interface barrier layer is disposed between the p-type amorphous silicon layer and the intrinsic type amorphous silicon layer. An index of refraction of the material in the conductive contact layer is between an index of refraction of the material in the first transparent conductive oxide layer and an index of refraction of the material in the p-type amorphous silicon layer. The second p-i-n junction comprises: a p-type microcrystalline silicon layer; an intrinsic type microcrystalline silicon layer; and an n-type amorphous silicon layer. An index of refraction of the material in the conductive index matching layer is less than an index of refraction of the material in the second transparent conductive oxide layer. The conductive index matching layer has a refractive index of 1.4-1.8. The metal back electrode is a composite film stack having a silicon or palladium doped silver layer disposed on the second transparent conductive oxide layer and a nickel vanadium alloy layer formed on the silicon doped silver layer. The barrier layer is a tin oxide layer, an iron doped tin oxide layer, a titanium oxide layer, or an iron doped titanium oxide layer. The substrate comprises a glass substrate having an iron element that has a concentration of 0.01-0.03 wt.%. An electrical sheet resistance of the combination of the formed first transparent conductive oxide layer and the formed conductive contact layer is less than 10 Ohms per square.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic side-view of a single junction thin film solar cell.    Thin film solar cell (100)    Substrate (102)    Anti-reflective coating layer (103)    Optional barrier layer (104)    P-type amorphous silicon layer. (110)