Fabrication and Investigation of Optimal Refractive Index Profile of Silicon Nanowires to Improve the Efficiency of Solar Cells

In the structure of the solar cell, thin silicon layers are located in the main bilayer in the form of a nanowire structure. These nanostructures enhance light absorption and convert it into electrical energy. The effective refractive index profile of silicon nanowires is used as an important property in solar cells, which can be significantly changed. These changes may be due to the change in the structure of the nanostructure, size, shape, as well as the change in the concentration of silicon nanowire particles, which leads to the improvement or reduction of light absorption and solar cell performance. In this research, the size, shape and concentration of silicon nanowires were synthesized and controlled at different times using gold catalyst and chemical vapor deposition and vapor-liquid-solid (VLS) techniques. The structural properties of the synthesized silicon nanowires were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The optimal effective refractive index was found to be dependent on the length and density of the nanowires. The results show that the maximum efficiency and absorption of the solar cell occurs in the length of 2 mμ and the density ratio of 36% of silicon nanowires. The efficiency of the solar cell in this condition is equal to 9.6%, the filling factor is 66.4%, the short circuit current density in this sample is 28.253 mA.cm-2 and the voltage is 520 mV.