Blaze gratings as light trapping structures for enhancing cell efficiency of thin-film crystalline silicon solar cells

The authors studied the influence of blaze gratings on the enhancement of effective optical absorption in thin-film crystalline silicon (TF-cSi) solar cells. Polarization dependent two-dimensional (2D) numerical simulations based on rigorous coupled wave analysis (RCWA) and finite element method (FEM) are implemented for the optimization of optical absorption of the solar cell structure. We found a rather large tolerance in design parameters of the optimized blaze grating structure. The optimized blaze grating structures help in improving the cell efficiency, especially for weak absorption thin cell structures. The enhancement of equivalent optical path length reveals the efficient light trapping effect caused by the diffractions of the blaze grating structures, especially in the long wavelength range. Incorporated with the optimized antireflection coating and blaze-grating structure, the 2-μm cell shows an enhancement of cell efficiency up to 40.5%, 43.5%, and 42.0% for S-polarization, P-polarization, and non-polarized cases, respectively. Such a simple blaze-grating thin-film solar cell structure is promising for low-cost and high-efficient solar cell applications.