Enhancement of light absorption from randomizing and geometric textures

Abstract

Surface textures are widely used to enhance absorption in an optical sheet by scattering weakly absorbed light into totally internally reflected modes. This study, which is based on ray-tracing studies of crystalline silicon solar cells with periodic geometric textures, investigates how the distribution of scatter influences absorption enhancement. The distribution of scatter is found to depend on the topology of texture facets as well as on the direction of incident light. Examples of the scatter characteristics in sheets textured with inverted pyramids, grooves, and perpendicular grooves are given. Broadly scattering textures are found to develop random scatter consistently only when exposed to isotropically incident band-gap wavelengths. Although broadband absorption enhancement from a geometric texture is affected by whether scatter is two or three dimensional, the fraction of rays blocked by the texture at early scatter stages is more important. Reasons are given as to why there may be geometric textures that enhance broadband absorption more than the randomizing texture under isotropic incidence.