Liu Wenfu, Guo Xiaolei, Xing Shule, Yao Haizi, Wang Yinling, Bai Liuyang, Wang Qi, Zhang Liang, Wu Dachuan, Zhang Yuxiao, Wang Xiao, Yi Yasha
School of Mechanical and Energy Engineering, Huanghuai University, Zhumadian 463000, Henan, China.
Integrated Nano Optoelectronics Laboratory, University of Michigan, Dearborn, MI 48128, USA.
Nanomaterials (Basel). 2020 Sep 2;10(9):1740. doi: 10.3390/nano10091740.
Single nanowires (NWs) are of great importance for optoelectronic applications, especially solar cells serving as powering nanoscale devices. However, weak off-resonant absorption can limit its light-harvesting capability. Here, we propose a single NW coated with the graded-index dual shells (DSNW). We demonstrate that, with appropriate thickness and refractive index of the inner shell, the DSNW exhibits significantly enhanced light trapping compared with the bare NW (BNW) and the NW only coated with the outer shell (OSNW) and the inner shell (ISNW), which can be attributed to the optimal off-resonant absorption mode profiles due to the improved coupling between the reemitted light of the transition modes of the leak mode resonances of the Si core and the nanofocusing light from the dual shells with the graded refractive index. We found that the light absorption can be engineered via tuning the thickness and the refractive index of the inner shell, the photocurrent density is significantly enhanced by 134% (56%, 12%) in comparison with that of the BNW (OSNW, ISNW). This work advances our understanding of how to improve off-resonant absorption by applying graded dual-shell design and provides a new choice for designing high-efficiency single NW photovoltaic devices.
单根纳米线（NWs）对于光电子应用至关重要，特别是对于为纳米级器件供电的太阳能电池。然而，较弱的非共振吸收会限制其光捕获能力。在此，我们提出一种涂覆有梯度折射率双壳层的单根NW（DSNW）。我们证明，通过内壳层适当的厚度和折射率，与裸NW（BNW）、仅涂覆外壳层的NW（OSNW）和仅涂覆内壳层的NW（ISNW）相比，DSNW表现出显著增强的光捕获能力，这可归因于由于硅芯泄漏模共振的跃迁模式的再发射光与具有梯度折射率的双壳层的纳米聚焦光之间耦合的改善而产生的最佳非共振吸收模式分布。我们发现，可以通过调整内壳层的厚度和折射率来设计光吸收，与BNW（OSNW，ISNW）相比，光电流密度显著提高了134%（56%，12%）。这项工作推进了我们对如何通过应用梯度双壳层设计来改善非共振吸收的理解，并为设计高效单根NW光电器件提供了新的选择。
