Fabrication of innovative diffraction gratings for light absorption enhancement in silicon thin films for solar cell application

Light trapping structures are necessary for optimal light absorption in thin-film solar cells for improving its efficiency. Absorption in thin-film solar cells can be improved by revising the geometry of solar cell structure. The diffraction phenomenon is at the heart of spectral research of light. In this article, absorption enhancement in silicon thin-film absorber layer is investigated via optical grating structure. Fabrication of an effective light-trapping through engineering metallic grating structures realized to enlarge the optical path length of light within the absorber layer. Grating fabrication technology was employed by using a laser beam to write patterns on bare metallic chromium films. Circular patterns were written using polar coordinate laser writer. These particular efforts showed increased absorption of light in the ultraviolet (UV) and near infrared (NIR) part of the solar spectrum and that is effective in achieving performance close to 98% absorption at shorter wavelengths, i.e., from 400 to 500 nm with a 2-μm grating period. Thus, these fabricated grating structures can be used as efficient backside reflector in thin-film solar cells.