Solution-processed omnidirectional antireflection coatings on amorphous silicon solar cells

Abstract

Solution-processed spherical surface textures are demonstrated on commercial amorphous silicon solar cells. The texture is formed with a monolayer of silica microspheres by convective coating, followed by a spin-on-glass film. It is found that the spherical texture reduces the reflectivity of the cells in the wavelength regime of 400–1200 nm, thus broad spectrum. It is also found that the spherical texture improves the efficiency of the cells at various incident angles from surface normal to at least 60°. The improvement in efficiency increases at larger incident angles to as high as 12% relative improvement, demonstrating its omnidirectionality. Current-voltage characteristics show that the efficiency improvement with coating is largely due to the increased short circuit current, while the open-circuit voltage remains the same. Therefore the efficiency improvement is attributed to more light coupled into the cells. This omnidirectional surface texture offers an attractive solution for antireflection in both polycrystalline silicon and thin-film solar cells.