Broad-band anti-reflection coupler for a : Si thin-film solar cell

This work numerically demonstrates a new anti-reflection coupler (ARC) with high coupling efficiency in a Si substrate solar cell. The ARC in which the grating is integrated on a glass encapsulation and a three-layer impedance match layer is proposed. A coupling efficiency of 90% is obtained at wavelengths between 350 and 1200 nm in the TE and TM modes when the incident angle is less than 30 degrees. In comparison with a 1 mu m absorber layer, the integrated absorption of an a-Si thin-film solar cell without a new ARC is doubled, at long wavelengths (750 nm <= lambda <= 1200 nm), as calculated by FDTD method.