制造高对比度光栅的频谱分割色散元件的聚光光伏系统
Summary
The fabrication of high contrast gratings as the parallel spectrum splitting dispersive element in a concentrated photovoltaic system is demonstrated. Fabrication processes including nanoimprint lithography, TiO2 sputtering and reactive ion etching are described. Reflectance measurement results are used to characterize the optical performance.
Abstract
High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve the solar conversion efficiency of a concentrated photovoltaic system. The proposed system will also lower the solar cell cost in the concentrated photovoltaic system by replacing the expensive tandem solar cells with the cost-effective single junction solar cells. The structures and the parameters of high contrast gratings for the dispersive elements were numerically optimized. The large-area fabrication of high contrast gratings was experimentally demonstrated using nanoimprint lithography and dry etching. The quality of grating material and the performance of the fabricated device were both experimentally characterized. By analyzing the measurement results, the possible side effects from the fabrication processes are discussed and several methods that have the potential to improve the fabrication processes are proposed, which can help to increase the optical efficiency of the fabricated devices.
Introduction
无需移动能量消耗的显著一部分可再生能源现代社会将无法生存。要做到这一点，我们必须找到一种方式的成本比在不久的将来，石油为主的能源更低的收获可再生能源。太阳能是地球上最丰富的可再生能源。尽管很多进展的已在太阳能收集，它仍然是非常具有挑战性的，用石油为基础的能源竞争。提高太阳能电池的效率是最有效的方法来降低的太阳能收集系统的成本之一。
光学透镜和盘的反射器通常用在最浓的光伏（CPV）系统1，实现了高浓度对小面积的太阳能电池的太阳能发电率，所以它是经济上可行的利用昂贵串联多结太阳能电池2中CPV系统，并保持合理的成本的同时。然而，对于大多数非集中光伏系统，其通常需要的太阳能电池的大面积装置，高成本叠层太阳电池不能掺入，尽管它们通常具有更广阔的太阳光谱响应和比更高的总转换效率单结太阳能电池3。
最近，与并行光谱分裂光学器件的帮助下（ 即色散元件），平行光谱分裂光伏技术4使得有可能，类似的或更好的频谱覆盖范围和转换效率，而无需使用昂贵的串联型太阳能电池来实现。太阳光谱可以被分成不同的频带，每个频带可以被吸收并转换为电的专门的单结太阳能电池。以这种方式，昂贵的串联型太阳能电池中CPV系统可通过单结太阳能电池的并行分布来代替•不用对性能的任何折衷。
这是设计本报告中的色散元件可以在反射的CPV系统（它是基于盘反射器），以实现平行的频谱分割为改进太阳能电转换效率和降低的成本施用。多层高对比度光栅（HCG）5用作色散元件通过设计的HCG各层工作作为光学带反射器。的结构和色散元件的参数进行数值优化。此外，高对比度的光栅的制造通过使用电介质色散元件（ 二氧化钛）溅射，纳米压印光刻6和反应离子蚀刻进行了研究和论证。
Protocol
Representative Results
Discussion
首先，在TiO 2膜的质量对于HCG的性能非常关键。反射率峰值将更高，如果在TiO 2膜具有较少损耗和表面粗糙度。在TiO 2膜具有更高的折射率也是有利的，因为该光学模式限制将通过在指数更高的对比度，从而可以产生更平坦和更广泛的反射带中的HCG来增强。
第二，在制造误差会对HCG显著影响，应加以避免。在制造中引入的粗糙度会导致更多的光被散射?…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
这项研究得到为中心的能源纳米，由能源，科学办公室根据奖号DE-SC0001013美国能源部资助的能源前沿研究中心的一部分。我们还要感谢张兆旭博士和杨建华惠普实验室的博士它们对二氧化钛薄膜溅射和折射率测量帮助。
Materials
| 184 SILICONE ELASTOMER KIT | SYLGARD | Polydimethylsiloxane (PDMS) | |
| 4-inch silicon wafer | Universitywafer | ||
| 4-inch fused silica wafer | Universitywafer | ||
| Poly(methyl methacrylate) | SIGMA-ALDRICH | 182265 | |
| UV-curable resist | Nor available on market | ||
| PlasmaLab System 100 | Oxford Instruments | ICP IRE machine | |
| UV curing system for nanoimprint fabrication | Not available on market | ||
| Ocean Optics HR-4000 | Ocean Optics | HR-4000 | Spectrometer with normal detector |
| Lambda 950 UV / VIS | PerkinElmer | spectrometer with hemisphere intergration detector | |
| JSM-7001F-LV | JEOL | Field emission SEM | |
| DC magnetron sputtering machine | Equipment is in HP labs, who helped us to sputter the TiO2 | ||
| Metal e-beam evaporator | Temescal | BJD-1800 |
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