Silicon nanowire arrays based “black silicon” solar cells

Recently, great attention has been put on the possible applications of nanotechnology in photovoltaics. Here, we report room temperature growth of large area black silicon surface consisting of silicon nanowires (SiNWs) array with reflectivity reduced to < 4% in the entire spectral range (300-1000 nm) of interest for solar cells and fabrication of solar cell (n⁺pp⁺ structure) on such "black silicon" substrates. Growth of SiNW arrays was carried out on p-type (1-5 Ω-cm) crystalline silicon wafers by a silver induced wet chemical etching process in aqueous HF+AgNO₃ etching solution. For solar cell fabrication, SiNW arrays were grown selectively on the active device area (on the front) by protecting the regions where front contacts are to be made. The n⁺pp⁺ structure based solar cells were fabricated by conventional cell fabrication protocol. The present process overcomes the front electrode contact problem addressed before in case of SiNWs based silicon solar cells.