Solution-processed spherical surface textures on amorphous silicon solar cells

Solution-processed spherical surface textures are demonstrated as a cost-effective antireflection coating on commercial amorphous Si solar cells. The spherical textures are 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 reflectance of the cells in a broad wavelength range of 400 - 1,200 nm. More importantly, the spherical texture improves the efficiency of the cells at various incident angles from surface normal to at least 60°. The efficiency improves with incident angle to as high as 120/0 relative improvement, demonstrating its omni-directionality. I-V characterization reveals that the efficiency improvement is due to increased light coupling into the cells. A monolayer of silica microspheres alone reduces the efficiency by reducing the short-circuit current, and the spin-on-glass film alone reduces the efficiency by reducing the fill factor. This omni-directional surface texture represents a cost-effective antireflection approach for fixed-orientation solar panels and can be applied to both polycrystalline Si and thin-film solar cells.