非晶硅PV电池一维金属光栅陷光效率的极限
Limits of light-trapping efficiency of prototypical lamellar 1-d metal gratings for amorphous silicon PV cells
摘要：
一维层状光栅允许通过在亥姆霍兹方程的精确本征模的基础上扩展电磁场来求解麦克斯韦方程的特别有效的方式。然后，解可以解析地表示为这些本征模的叠加，并且精度仅取决于所包括的模式的数目$N$。在此基础上，我们计算的光捕获性能的理想极限为原型的层状金属表面浮雕光栅在非晶硅（a-Si）光伏电池假设在金属和前表面反射的光吸收可以被抑制。我们发现，几何不对称性可以增加吸收。对于足够大的$N$，E偏振的吸收光谱的收敛。对于H偏振，波长为$λ<$ 680-700 nm时达到该值，而积分AM 1.5加权吸收在大的$N$处变化小于1%。对于高度为200 nm且垂直入射的a-Si层，我们获得了具有非对称的E偏振和具有正弦状层状光栅反射器的H偏振的79\%和90\%的总吸收的上限，而平面反射器产生62\%的限制，其中100\%代表$350<λ<$ 770 nm的完全吸收。
英文摘要：
One-dimensional lamellar gratings allow a particularly efficient way for solving Maxwell's equations by expanding the electromagnetic field in the basis of exact eigenmodes of the Helmholtz equation. Then, the solution can be expressed analytically as a superposition of these eigenmodes and the accuracy depends only on the number of modes $N$ included. On this basis, we compute ideal limits of light-trapping performance for prototypical lamellar metal surface relief gratings in amorphous silicon (a-Si) PV cells assuming that light absorption in the metal and front surface reflection can be suppressed. We show that geometric asymmetry can increase absorption. For large enough $N$, convergence of absorption spectra for E polarisation is reached. For H polarisation it is reached for wavelengths $λ<$680-700 nm, while the integrated AM1.5-weighted absorption varies by less than 1\% at large $N$. For an a-Si layer with height 200 nm and normal incidence, we obtain upper limits of the total absorption of 79\% for E-polarisation with asymmetric- and 90\% for H-polarisation with sine-like lamellar grating reflectors, whereas a planar reflector yields a limit of 62\%, where 100\% stands for complete absorption for $350<λ<$770 nm.
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