Liu Wenfu, Wang Yinling, Guo Xiaolei, Song Jun, Wang Xiao, Yi Yasha
School of Mechanical and Energy Engineering, Huanghuai University, Zhumadian, Henan 463000, China.
Integrated Nano Optoelectronics Laboratory, University of Michigan, Dearborn, MI 48128, USA.
Nanomaterials (Basel). 2020 Oct 25;10(11):2121. doi: 10.3390/nano10112121.
Light trapping in single nanowires (NWs) is of vital importance for photovoltaic applications. However, circular NWs (CNWs) can limit their light-trapping ability due to high geometrical symmetry. In this work, we present a detailed study of light trapping in single silicon NWs with an elliptical cross-section (ENWs). We demonstrate that the ENWs exhibit significantly enhanced light trapping compared with the CNWs, which can be ascribed to the symmetry-broken structure that can orthogonalize the direction of light illumination and the leaky mode resonances (LMRs). That is, the elliptical cross-section can simultaneously increase the light path length by increasing the vertical axis and reshape the LMR modes by decreasing the horizontal axis. We found that the light absorption can be engineered via tuning the horizontal and vertical axes, the photocurrent is significantly enhanced by 374.0% (150.3%, 74.1%) or 146.1% (61.0%, 35.3%) in comparison with that of the CNWs with the same diameter as the horizontal axis of 100 (200, 400) nm or the vertical axis of 1000 nm, respectively. This work advances our understanding of how to improve light trapping based on the symmetry breaking from the CNWs to ENWs and provides a rational way for designing high-efficiency single NW photovoltaic devices.
单根纳米线中的光捕获对于光伏应用至关重要。然而，由于高度的几何对称性，圆形纳米线（CNWs）会限制其光捕获能力。在这项工作中，我们对具有椭圆形横截面的单根硅纳米线（ENWs）中的光捕获进行了详细研究。我们证明，与CNWs相比，ENWs表现出显著增强的光捕获能力，这可归因于能够使光照射方向与泄漏模式共振（LMRs）正交的对称破缺结构。也就是说，椭圆形横截面可以通过增加垂直轴同时增加光程长度，并通过减小水平轴重塑LMR模式。我们发现，可以通过调整水平轴和垂直轴来设计光吸收，与水平轴直径为100（200，400）nm或垂直轴为1000nm的相同直径的CNWs相比，光电流分别显著增强了374.0%（150.3%，74.1%）或146.1%（61.0%，35.3%）。这项工作推进了我们对如何基于从CNWs到ENWs的对称破缺来改善光捕获的理解，并为设计高效单根纳米线光伏器件提供了一种合理的方法。
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