Enhancement of reflectance reduction of solar cells by a silicon nanoparticle layer on a textured silicon substrate

Abstract

To reduce the surface reflectance of Si solar cells, a structure has been developed in which a silicon nanoparticle (SiNP) layer is formed on a pyramid-like structure to simultaneously exploit multiple reflections and refractive index changes. The high refractive index of Si leads to the high reflectance of polished Si wafers. A conventional pyramid-like structure is formed on the surface of the Si wafer to reduce reflections using multiple reflections; however, the resultant sample reflectance is high because of the refractive index difference between air and Si. Nevertheless, although the reflectance of a SiNP layer on a polished Si wafer is high, the short-wavelength reflectance is <10 %. Our SiNP layer was then formed on a textured Si wafer by spin coating with a succession of changes to the spin-coating speed. In this manner, the reflectance after each speed change drastically decreased to <10 %, while the short-circuit current increased from 25.2 to 34.1 mA cm−2. The extremely thin SiNP layer and pyramid-like structure are promising as antireflective layers for solar cells.