NOVELTY - A back face electrode layer (2) is formed on the principal plane side of a light incident side glass substrate (1) and formed at the side of a polycrystalline silicon bottom cell layer (7) opposite to the side in which outside light is incident on bottom cell layer. A second transparent conductive film (8) and a refractive index adjustment layer (9) are formed between bottom cell layer and back face electrode and at which the side closer to back face electrode layer has smaller refractive index than the side distant from the back face electrode layer.    USE - For photovoltaic conversion module (claimed).    ADVANTAGE - Increases photovoltaic conversion efficiency due to reduction in the amount of electromagnetic waves that penetrate and are absorbed by the back face electrode layer in thin film silicon solar battery. Reduces photoreceptive area of the photovoltaic conversion module necessary for obtaining the same amount of electrical energy and decreases production cost of the photovoltaic conversion module if photovoltaic conversion efficiency is improved, thus installation area of photovoltaic conversion module is made smaller.    DETAILED DESCRIPTION - The second transparent conductive film contains at least one of zinc oxide, indium tin oxide, and tin oxide. The zinc oxide is doped with at least one of gallium, silicon, aluminum, and boron. The refractive index adjustment layer contains at least one of silicon oxide, magnesium fluoride, magnesium oxide, glass, aluminum oxide, yttrium oxide, calcium fluoride, lithium fluoride, and cavities. The back face electrode layer contains at least one of silver, aluminum, copper, and gold. INDEPENDENT CLAIMS are the following:    (1) a photovoltaic conversion module;    (2) a photovoltaic conversion panel; and    (3) a photovoltaic conversion system.    DESCRIPTION OF DRAWING(S) - The figure shows the cross-sectional view of a photovoltaic conversion cell.    Light incident side glass substrate (1)    Back face electrode layer (2)    Bottom cell layer (7)    Second transparent conductive film (8)    Refractive index adjustment layer (9)