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arXiv 1502.05418cond-mat.mes-hallcond-mat.mtrl-sciphysics.optics
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高折射率纳米线谐振器中的宽带量子效率增强

Broadband Quantum Efficiency Enhancement in High Index Nanowires Resonators

Yiming Yang, Xingyue Peng, Steven Hyatt, Dong Yu

AI总结:

该研究利用高折射率PbS纳米线谐振器和锥形结构实现最高350% EQE及宽带吸收增强,并以简单工艺制备出性能媲美Si同轴p-n结器件的单纳米线肖特基太阳能电池。

摘要:

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升光伏性能提供了一种有前景的方法。然而,在现有纳米线光子器件中,由光吸收截面与纳米线直径之比定义的纳米线吸收效率始终徘徊在1左右,而且吸收增强的光谱宽度较窄。在此,我们表明,在具有更高折射率的纳米线中,吸收效率可以得到显著提升:实验在硫化铅(PbS)纳米线谐振器中观察到高达350%的外量子效率(EQE),与Si纳米线相比提高了3倍。此外,在单根锥形纳米线中实现了宽带吸收增强,其中不同波长的光在直径不同的区段被吸收,类似于叠层太阳能电池。总体而言,单根纳米线肖特基结太阳能电池受益于光学共振、接近带隙的开路电压以及较长的少数载流子扩散长度,展现出与单根Si纳米线同轴p-n结电池相当的功率转换效率(PCE),但其制造工艺要简单得多。

英文摘要:

Light trapping in sub-wavelength 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% external quantum efficiency (EQE) in lead sulfide (PbS) 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 analogous to a tandem solar cell. 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 (PCE) comparable to single Si NW coaxial p-n junction cells11, but with much simpler fabrication processes.

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