A photovoltaic system converts sunlight into electrical energy using solar cells. The solar cell consists of two silicon layers, each with a positive (p-doped) and a negative (n-doped) excess of charge carriers. An electric field builds up in the boundary layer (space charge zone) between them. When light (photons) strikes the boundary layer, an electron is released. The released electron is drawn into the n-region. At the top of the solar cell, a front contact picks up the free electrons. If an electrical load is now connected, the direct current flows to the rear contact on the p-layer.