在硅薄膜太阳电池中，灵活的光学设计可以实现表层的零反射损耗，增大吸收层中光的透射率，从而提高薄膜太阳电池的光收集能力。在薄膜太阳电池吸收层表面设计了矩形介质光栅。利用严格耦合波理论和模态传输理论研究了光栅结构参数对反射率的影响。考虑到AM1.5G太阳能光谱和a-Si的吸收光谱，光栅参数进一步优化。由于微加工的误差，使得矩形光栅变成梯形光栅，必然会影响硅薄膜太阳电池表面反射率。研究结果表明，长周期光栅同样可以实现低反射率，在工艺上也容易实现。采用梯形光栅可进一步降低表面反射率，并且在太阳光入射角为-40°~+40°的范围内保持在6%以下。

In thin-film silicon solar cells, a flexible optical design for light collection can lead to zero reflection loss and enhance the optical path length in absorber layer. In this paper, rectangular dielectric gratings were demonstrated on the top of solar cells. The influence of the structural parameters on the reflectivity of solar cells was investigated by means of Rigorous Coupled Wave Analysis and Modal Transmission Line theory, respectively. AM 1.5G solar energy spectrum and a-Si absorption spectrum were discussed to optimize the grating parameters. Because of the processing error, the rectangular gratings become trapezoid gratings which could affect the surface reflectivity of the thin-film silicon solar cells. The results show that long-period gratings which are easy to implement in the process can be achieved with low reflectivity. The surface reflectivity is further reduced with trapezoidal gratings, and the reflectivity can be maintained within 6% in the incident angle of -40°～+40°.