NOVELTY - A thin film solar cell comprises cells positioned on substrate (110), where each of the cells includes first electrode positioned on one surface of substrate; photoelectric conversion unit (130) positioned on the electrode; back reflection layer (140) including first reflection layer contacting the conversion unit and second reflection layer having opening exposing a portion of the first layer, the second layer contacting the first layer; and second electrode positioned on the back reflection layer, the second electrode is electrically connected to the first layer through the opening.    USE - As thin film solar cell (claimed).    ADVANTAGE - The thin film solar cell includes back reflection layer for increasing light absorption of the intrinsic semiconductor layer, thereby increasing the current density.    DETAILED DESCRIPTION - A thin film solar cell comprises cells positioned on substrate (110), where each of the cells includes first electrode positioned on one surface of the substrate; at least one photoelectric conversion unit (130) positioned on the electrode; back reflection layer (140) including first reflection layer contacting the photoelectric conversion unit and second reflection layer having opening exposing a portion of the first reflection layer, the second reflection layer contacting the first reflection layer; and second electrode positioned on the back reflection layer, the second electrode is electrically connected to the first reflection layer through the opening. An INDEPENDENT CLAIM is included for manufacturing thin film solar cell involving forming first electrode on substrate; forming at least one photoelectric conversion unit on the first electrode; forming first reflection layer having conductivity on the photoelectric conversion unit and forming second reflection layer having opening exposing a portion of the first reflection layer on the first reflection layer thereby form back reflection layer; and forming second electrode, that is electrically connected to the first reflection layer through the opening, on the second reflection layer.    DESCRIPTION OF DRAWING(S) - The figure shows partial cross-sectional view of thin film solar cell.    Substrate (110)    Transparent conductive oxide electrode (120)    Photoelectric conversion unit (130)    Back reflection layer (140)    Back electrode (150)