Wellenzohn Markus, Hainberger Rainer
AIT Austrian Institute of Technology GmbH, Health & Environment Department, Nano Systems, Vienna, Austria.
Opt Express. 2012 Jan 2;20(1):A20-7. doi: 10.1364/oe.20.000a20.
This numerical study investigates the influence of rectangular backside diffraction gratings on the efficiency of silicon solar cells. Backside gratings are used to diffract incident light to large propagation angles beyond the angle of total internal reflection, which can significantly increase the interaction length of long wavelength photons inside the silicon layer and thus enhance the efficiency. We investigate the influence of the silicon thickness on the optimum grating period and modulation depth by a simulation method which combines a 2D ray tracing algorithm with rigorous coupled wave analysis (RCWA) for calculating the grating diffraction efficiencies. The optimization was performed for gratings with period lengths ranging from 0.25 µm to 1.5 µm and modulation depths ranging from 25 nm to 400 nm under the assumption of normal light incidence. This study shows that the achievable efficiency improvement of silicon solar cells by means of backside diffraction gratings strongly depends on the proper choice of the grating parameters for a given silicon thickness. The relationship between the optimized grating parameters resulting in maximum photocurrent densities and the silicon thickness is determined. Moreover, the thicknesses of silicon solar cells with and without optimized backside diffraction gratings providing the same photocurrent densities are compared.
这项数值研究探讨了矩形背侧衍射光栅对硅太阳能电池效率的影响。背侧光栅用于将入射光衍射到全内反射角之外的大传播角，这可以显著增加长波长光子在硅层内的相互作用长度，从而提高效率。我们通过一种模拟方法研究硅厚度对最佳光栅周期和调制深度的影响，该方法将二维光线追踪算法与严格耦合波分析（RCWA）相结合来计算光栅衍射效率。在垂直光入射的假设下，对周期长度从0.25 µm到1.5 µm、调制深度从25 nm到400 nm的光栅进行了优化。这项研究表明，通过背侧衍射光栅提高硅太阳能电池效率的程度在很大程度上取决于对于给定硅厚度，光栅参数的恰当选择。确定了导致最大光电流密度的优化光栅参数与硅厚度之间的关系。此外，还比较了具有相同光电流密度的有无优化背侧衍射光栅的硅太阳能电池的厚度。
