Touted as a promising alternative energy source for decades, solar panels crown rooftops and roadside signs, and help keep spacecraft powered. But how do solar panels work? Simply put, a solar panel works by allowing photons, or particles of light, to knock electrons free from atoms, generating a flow of electricity. Solar panels actually comprise many, smaller units called photovoltaic cells. (Photovoltaic simply means they convert sunlight into electricity.) Many cells linked together make up a solar panel. Each photovoltaic cell is basically a sandwich made up of two slices of semi-conducting material, usually silicon — the same stuff used in microelectronics. To work, photovoltaic cells need to establish an electric field.