Large-Area Nanosphere Gratings for Light Trapping and Reduced Surface Losses in Thin Solar Cells
Large-Area Nanosphere Gratings for Light Trapping and Reduced Surface Losses in Thin Solar Cells
复制标题
DOI：
10.1109/jphotov.2019.2918183
复制
发表时间：
2019-06
影响因子：
3
通讯作者：
Yuan-Chih Chang;M. Pollard;D. Payne;A. Sprafke;S. Pillai;D. Bagnall
中科院分区：
文献类型：
--
作者：
Yuan-Chih Chang;M. Pollard;D. Payne;A. Sprafke;S. Pillai;D. Bagnall
薄硅太阳能电池中的光捕获需要与标准商业电池完全不同的制造方法。较弱的光吸收和对表面复合的灵敏度增加需要在更宽的光谱范围内实现光捕获，并且理想情况下，无需对吸收体本身进行纹理化。纳米级光捕获结构允许最强的散射被调谐到最需要倾斜散射到吸收体中的波长。此外，“外部地”应用这些结构，即，在良好钝化的平面硅表面上，减小了表面积并允许保持最佳的电子条件。尽管有这些优点，但平衡效率增益、成本和光刻保真度的挑战已经阻止了纳米级光捕获方案的商业使用。在这里，我们展示了使用纳米球光刻生产高品质和成本效益的纳米级光捕获结构，适用于纳入薄太阳能电池。我们成功地在30 μm厚的c-Si赝电池上制备了大面积、均匀的金属纳米球结构，并测量了它们的光捕获效率。模拟和制造的伪电池特性之间的比较突出了制造均匀结构的关键挑战，包括非保形涂层内的气隙的影响和几何形状的微小变化。通过吸收光谱以及光谱和空间分辨光致发光的光学表征表明，与平面30 μm厚的器件相比，短路电流密度明显增强，高达4.33 mA/cm 2，并且在接近Si的带隙处吸收率增强3.7倍。
Light trapping in thin silicon solar cells demands radically different fabrication approaches to standard commercial cells. Weaker optical absorption and increased sensitivity to surface recombination requires light trapping to be achieved over a broader spectral range and, ideally, without texturing the absorber itself. Nano-scale light trapping structures allow the strongest scattering to be tuned to wavelengths, where oblique scattering into the absorber is needed most. Furthermore, applying these structures “externally,” i.e., on a well-passivated planar silicon surface, reduces the surface area and permits optimal electronic conditions to be maintained. Despite these advantages, the challenges of balancing efficiency gain, cost, and lithographic fidelity have prevented the commercial use of nano-scale light trapping schemes. Here, we demonstrate the use of nanosphere lithography for producing high-quality and cost-effective nano-scale light trapping structures suitable for incorporation in thin solar cells. We have successfully fabricated large-area and uniform metal nanospheregrating structures, with embedded dielectric nanospheres, on 30 μm thick c-Si pseudo cells and measured their effectiveness for light trapping. Comparison between simulations and the fabricated pseudo cells’ characteristics highlighted key challenges in fabricating uniform structures, including the impact of air gaps within non-conformal coatings and minor changes in the geometry. Optical characterization via absorption spectroscopy and both spectral and spatially resolved photoluminescence showed a clear enhancement in the short-circuit current density of up to 4.33 mA/cm2 in comparison with a planar 30 μm thick device and a 3.7 times absorptance enhancement close to the bandgap of Si.