A solar cell includes a substrate, an emitter region positioned at a first surface of the substrate, a first electrode positioned on the first surface of the substrate, a back passivation layer positioned on a second surface opposite the first surface of the substrate, and a second electrode which is positioned on the back passivation layer and is electrically connected to the substrate through holes of the back passivation layer. The second electrode includes connection electrodes positioned inside the holes of the back passivation layer and a back electrode layer positioned on the connection electrodes and the back passivation layer. An adhesion enhanced layer is positioned between the back electrode layer and the back passivation layer and contains at least one of intrinsic amorphous silicon and intrinsic microcrystalline silicon.