Structural and optical characteristics of silicon nanowires prepared by the Ag-assisted chemical etching method

In order to improve photovoltaic efficiency, researches have been carried out on silicon nanowires (SiNWs). In this article, we report a comparative study between silicon substrate (Si) and SiNWs developed by a metal-assisted chemical etching (Ag) method at different etching times (25, 10 and 5 min). Scanning electron microscopy (SEM), transmission electron microscopy and X-ray diffraction were used to collect the morphological and structural information on the SiNWs. Raman spectroscopy shows that the intensity of the nanowires is 4 to 10 times higher than that of the substrate, and increases with increase in etching time. The total reflectance of SiNWs reduced to less than 5% over the entire visible range. The low reflectance and zero transmittance of SiNWs lead to higher absorbance in the visible wavelength range. The SiNW-etched nanowire structure (25 min) works best for capturing light, we believe that having longer nanowires improves the optical working of the nanostructures and may be a potential candidate for high efficiency photovoltaic solar cells and other optic devices. (author)