PROGRESS IN SINGLE CRYSTALLINE SILICON NANOWIRE SOLAR CELLS

Silicon nanowire carpets were grown from gold nano-templates by the Vapor Liquid Solid (VLS) process. As substrates silicon wafers, laser crystallized silicon thin films on glass, or TCO on glass were used. The Au nano-templates act, in a thermal CVD process, as a catalyst to decompose silane at about 500 degrees C. The result is a carpet formed of perfect single crystalline nanowires several 10 to 200 nm in diameter and several pm in length. The reflectivity of the silicon nanowire carpet is much lower than that of a silicon wafer. Moreover, strong internal light scattering leads to a high absorption so that the wires act as a perfect light trapping structure. The nanowires were nominally doped oppositely to the substrate. On a silicon substrate a p-n-junction forms at the base of the wires. I-V-curves demonstrate that the nanowire carpet acts as a diode and, under illumination, as solar cell with an open circuit voltage of 280 mV.