Aho Timo, Guina Mircea, Elsehrawy Farid, Cappelluti Federica, Raappana Marianna, Tukiainen Antti, Alam A B M Khairul, Vartiainen Ismo, Kuittinen Markku, Niemi Tapio
Opt Express. 2018 Mar 19;26(6):A331-A340. doi: 10.1364/OE.26.00A331.
We report on the fabrication of diffraction gratings for application as back contact reflectors. The gratings are designed for thin-film solar cells incorporating absorbers with bandgap slightly lower than GaAs, i.e. InAs quantum dot or GaInNAs solar cells. Light trapping in the solar cells enables the increase of the absorption leading to higher short circuit current densities and higher efficiencies. We study metal/polymer back reflectors with half-sphere, blazed, and pyramid gratings, which were fabricated either by photolithography or by nanoimprint lithography. The gratings are compared in terms of the total and the specular reflectance, which determine their diffraction capabilities, i.e. the feature responsible for increasing the absorption. The pyramid grating showed the highest diffuse reflection of light compared to the half-sphere structure and the blazed grating. The diffraction efficiency measurements were in agreement with the numerical simulations. The validated model enables designing such metal/polymer back reflectors for other type of solar cells by refining the optimal dimensions of the gratings for different wavelength ranges.
我们报告了用于作为背接触反射器的衍射光栅的制造。这些光栅是为薄膜太阳能电池设计的，该薄膜太阳能电池包含带隙略低于砷化镓的吸收体，即铟砷量子点或镓铟氮砷太阳能电池。太阳能电池中的光捕获能够增加吸收，从而导致更高的短路电流密度和更高的效率。我们研究了具有半球形、闪耀和金字塔形光栅的金属/聚合物背反射器，这些光栅是通过光刻或纳米压印光刻制造的。根据总反射率和镜面反射率对这些光栅进行比较，这两者决定了它们的衍射能力，即负责增加吸收的特性。与半球形结构和闪耀光栅相比，金字塔形光栅显示出最高的光漫反射。衍射效率测量结果与数值模拟结果一致。经过验证的模型能够通过为不同波长范围优化光栅的最佳尺寸，为其他类型的太阳能电池设计此类金属/聚合物背反射器。
