Department of Physics, University of California, Davis, California 95616, United States.
Nano Lett. 2015 May 13;15(5):3541-6. doi: 10.1021/acs.nanolett.5b01008. Epub 2015 Apr 30.
Light trapping in subwavelength semiconductor nanowires (NWs) offers a promising approach to simultaneously reducing material consumption and enhancing photovoltaic performance. Nevertheless, the absorption efficiency of a NW, defined by the ratio of optical absorption cross section to the NW diameter, lingers around 1 in existing NW photonic devices, and the absorption enhancement suffers from a narrow spectral width. Here, we show that the absorption efficiency can be significantly improved in NWs with higher refractive indices, by an experimental observation of up to 350% apparent external quantum efficiency in lead sulfide NW resonators, a 3-fold increase compared to Si NWs. Furthermore, broadband absorption enhancement is achieved in single tapered NWs, where light of various wavelengths is absorbed at segments with different diameters. Overall, the single NW Schottky junction solar cells benefit from optical resonance, near bandgap open circuit voltage, and long minority carrier diffusion length, demonstrating power conversion efficiency comparable to Si and III-V single NW coaxial p-n junction cells but with much simpler fabrication processes.
亚波长半导体纳米线（NWs）中的光捕获为同时减少材料消耗和提高光伏性能提供了一种很有前途的方法。然而，在现有的 NW 光子器件中，NW 的吸收效率（定义为光吸收截面与 NW 直径的比值）徘徊在 1 左右，并且吸收增强受到光谱宽度较窄的限制。在这里，我们通过实验观察到，在具有更高折射率的 NW 中，吸收效率可以显著提高，在 PbS NW 谐振器中观察到高达 350%的明显外量子效率，与 Si NW 相比增加了 3 倍。此外，在单个锥形 NW 中实现了宽带吸收增强，其中不同波长的光在不同直径的段中被吸收。总的来说，单个 NW 肖特基结太阳能电池得益于光学共振、近带隙开路电压和长少数载流子扩散长度，展示了与 Si 和 III-V 单 NW 同轴 p-n 结电池相当的功率转换效率，但制造工艺要简单得多。
