SBIR Phase I: Low-cost highly-reflective and light scattering dielectric nanoparticle based thin films for solar cells

这个小型企业创新研究第一阶段项目旨在证明一种创新概念的可行性，即使用高反射和光散射纳米颗粒薄膜作为太阳能电池背反射器，目标是取代高真空加工技术。传统的背反射器由溅射的金属薄膜组成，这对大规模系统来说需要很高的资本成本，而且由于溅射目标的维护、清洁和更换而频繁停机。此外，溅射的金属背反射器可能会对太阳能电池设备产生不利影响。带有银背反射器的太阳能电池可以达到创纪录的效率，但银会迁移到吸收材料中，降低性能和可靠性。此外，银不能很好地附着在太阳能电池制造所用的衬底上，很容易被氧化，从而降低其反射率。相反，溅射的铝背反射器通常用于薄膜太阳能行业，但铝吸收太阳光光谱的关键部分的光，从而实现适度的性能提升。本项目将使用成本较低的电泳沉积方法来生长介电纳米颗粒薄膜。预期的结果是一种可制造的纳米颗粒背反射器，对于高效和可靠的太阳能电池来说，它与银一样具有反射性。该项目的更广泛的影响/商业潜力是使用基于纳米颗粒的背反射器生产高效率的薄膜太阳能电池。所提出的基于纳米颗粒的背反射器可以用大气电泳沉积的方法来制备，取代了传统的高真空溅射金属的方法，这种方法昂贵、耗时、耗能，并且材料利用率低。基于纳米颗粒的工程化薄膜是获得非常高的光散射和反射表面的理想方法，这是高效太阳能电池背反射器所必需的特性。高太阳能电池性能和低成本制造方法的结合意味着，拟议的基于纳米颗粒的背反射器将处于有利地位，能够在竞争激烈的太阳能市场取得成功。2010年，太阳能市场的销售额为820亿美元。除了太阳能，基于高度工程的纳米颗粒薄膜的其他应用还包括用于高效平板显示器的背光反射器、用于自清洁和渗水应用的超疏水表面、用于电子设备的织构/多孔结构以及用于电光设备的光子结构。该项目将促进中西部上段以技术为基础的经济发展。与南达科他州立大学的合作将培训纳米材料科学和工程方面的研究生和本科生，以提高未来劳动力的能力。

This Small Business Innovation Research Phase I project aims to demonstrate the feasibility of an innovative concept in using highly reflective and light scattering nanoparticle thin films as solar cell back reflectors with the goal to replace high-vacuum processing techniques. Conventional back reflectors consist of a sputtered metal film, which requires high capital cost for large scale systems and frequent downtime due to maintenance, cleaning, and replacing of the sputtering targets. In addition, sputtered metal back reflectors can have adverse effects on the solar cell device. Solar cells with silver back reflectors can achieve record efficiencies, but silver migrates into the absorber material and deteriorates the performance and reliability. Further, silver does not adhere well to substrates used in solar cell manufacturing and readily oxidizes reducing its reflectivity. Instead, sputtered aluminum back reflectors are typically used in thin film solar industry, but aluminum absorbs light in a crucial portion of the sunlight spectrum resulting in moderate performance gains. This project will use the lower-cost electrophoretic deposition method to grow dielectric nanoparticle thin films. The anticipated result is a manufacturable nanoparticle back reflector that is equally as reflective as silver for high efficiency and reliable solar cells.The broader impact/commercial potential of this project is to produce high efficiency thin film solar cells using nanoparticle-based back reflectors. The proposed nanoparticle-based back reflector can be fabricated using the atmospheric electrophoretic deposition method and replaces the conventional approach of using high vacuum sputtering of metals, which can be expensive, time consuming, energy intensive, and have poor material utilization. Engineered nanoparticle-based films are an ideal way to obtain very high light scattering and reflective surfaces, which are required properties of back reflectors in high efficiency solar cells. A combination of high solar cell performance and low-cost manufacturing methods means that the proposed nanoparticle-based back reflector will be well positioned to succeed in a highly competitive solar market, which had sales of $82 billion in 2010. Beyond solar, additional applications for highly engineered nanoparticle-based films include backlight reflectors for high efficiency flat panel displays, superhydrophobic surfaces for self-cleaning and water shedding applications, textured/porous structures for electronic devices, and photonic structures for electro-optical devices. This project will promote technology-based economic development in the upper Midwest. Collaboration with South Dakota State University will train graduate and undergraduate students in nanomaterial science and engineering to advance the capabilities of the future workforce.