A pin junction photovoltaic device comprising a substrate and a pin junction semiconductor active layer region disposed on said substrate, said pin junction semiconductor active layer region comprising a p-type semiconductor layer composed of a p-type non-single crystalline semiconductor material, an i-type semiconductor layer composed of an i-type non-single crystalline semiconductor material, and an n-type semiconductor layer composed of an n-type non-single crystalline semiconductor material, characterized in that (a) a buffer layer comprising a non-single crystalline silicon semiconductor material substantially free of germanium atoms is interposed between said p-type semiconductor layer and said i-type semiconductor layer, (b) a buffer layer comprising a non-single crystalline silicon semiconductor material substantially free of germanium atoms is interposed between said i-type semiconductor layer and said n-type semiconductor layer, and said i-type semiconductor layer is formed of an amorphous silicon germanium semiconductor material containing the germanium atoms in an amount of 20 to 70 atomic % in the entire region in which the concentration distribution of the germanium atoms in the thickness direction is varied while providing a maximum concentration point.