The fabrication of silicon nanowire-based solar cells on silicon wafers and on ulticrystalline silicon thin films on glass is described. The nanowires show a strong broadband optical absorption, which makes them an interesting candidate to serve as an absorber in solar cells. The operation of a solar cell is demonstrated with n-doped nanowires grown on a p-doped silicon wafer. From a partially illuminated area of 0.6 cm2 open-circuit voltages in the range of 230–280 mV and a short-circuit current density of 2 mA cm−2 were obtained.