Design of Light Trapping Structures for Ultrathin Solar Cells

Abstract

The conversion efficiency of thin film silicon solar cell is still much below that of wafer silicon solar cell due to low optical absorption. Light trapping techniques can enhance the optical absorption in solar cells. Here, we design light trapping structures of double-side grating for ultrathin silicon solar cells based on a rigorous coupled-wave analysis method. The role of each grating was identified by analyzing the absorption spectra of ultrathin solar cell from 350 nm to 1100 nm wavelength at normal incidence, which shows use of top and bottom light trapping structures can achieve large optical absorption in different wave regimes. Inspired by this observation, the dual dielectric/dielectric and dielectric/ metallic grating structures were proposed and optimized to obtain broadband optical absorption close to the theoretic limit.