A solar cell module comprises a transparent substrate, e.g., a glass substrate. On top of the glass substrate a layer system is deposited. The layer system comprises a front electrode which may be a transparent conductive oxide (TCO) layer. Furthermore, the layer system comprises a thin film semiconductor layer deposited on the front electrode layer. A back electrode is formed on the thin film semiconductor layer which includes a very thin metal layer having a thickness d smaller than 50 nm. A Lambertian reflective layer is deposited on the thin metal layer in order to reflect light transmitted through the metal layer.