Nat Mater. 2010 Mar;9(3):239-44. doi: 10.1038/nmat2635. Epub 2010 Feb 14.
Si wire arrays are a promising architecture for solar-energy-harvesting applications, and may offer a mechanically flexible alternative to Si wafers for photovoltaics. To achieve competitive conversion efficiencies, the wires must absorb sunlight over a broad range of wavelengths and incidence angles, despite occupying only a modest fraction of the array's volume. Here, we show that arrays having less than 5% areal fraction of wires can achieve up to 96% peak absorption, and that they can absorb up to 85% of day-integrated, above-bandgap direct sunlight. In fact, these arrays show enhanced near-infrared absorption, which allows their overall sunlight absorption to exceed the ray-optics light-trapping absorption limit for an equivalent volume of randomly textured planar Si, over a broad range of incidence angles. We furthermore demonstrate that the light absorbed by Si wire arrays can be collected with a peak external quantum efficiency of 0.89, and that they show broadband, near-unity internal quantum efficiency for carrier collection through a radial semiconductor/liquid junction at the surface of each wire. The observed absorption enhancement and collection efficiency enable a cell geometry that not only uses 1/100th the material of traditional wafer-based devices, but also may offer increased photovoltaic efficiency owing to an effective optical concentration of up to 20 times.
硅线阵列是一种很有前途的太阳能收集架构，对于光伏应用而言，它可能是硅片的一种机械柔性替代方案。为了实现有竞争力的转换效率，尽管只占据阵列体积的一小部分，这些线必须在广泛的波长和入射角范围内吸收阳光。在这里，我们表明，线占阵列面积小于 5%的阵列可以实现高达 96%的峰值吸收，并且可以吸收高达 85%的全日、带隙以上的直接阳光。事实上，这些阵列表现出增强的近红外吸收，这使得它们的整体阳光吸收超过了等效体积随机纹理平面硅的射线光学光捕获吸收极限，在广泛的入射角范围内。我们还证明，硅线阵列吸收的光可以用 0.89 的峰值外量子效率收集，并且它们在每个线的表面通过径向半导体/液体结表现出宽带、近全内部量子效率，用于载流子收集。观察到的吸收增强和收集效率使电池几何形状不仅使用传统基于晶圆器件材料的 1/100，而且由于有效光学浓度高达 20 倍，还可能提高光伏效率。
