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

该小型企业创新研究第一阶段项目旨在展示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的创新概念的可行性，其目标是取代高真空处理技术。传统的背反射器由溅射金属膜组成，这对于大规模系统需要高的资本成本，并且由于维护、清洁和更换溅射靶而需要频繁的停机时间。此外，溅射金属背反射器可能对太阳能电池器件产生不利影响。具有银背反射器的太阳能电池可以实现记录效率，但是银迁移到吸收体材料中并使性能和可靠性劣化。此外，银不能很好地粘附到太阳能电池制造中使用的基板上，并且容易氧化，降低其反射率。相反，溅射铝背反射器通常用于薄膜太阳能行业，但铝吸收太阳光谱的关键部分中的光，从而导致适度的性能增益。本计画将使用较低成本的电泳沉积法来成长介电奈米粒子薄膜。预期的结果是可制造的纳米颗粒背反射器，其反射率与银相同，用于高效和可靠的太阳能电池。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薄膜太阳能电池。所提出的基于纳米颗粒的背反射器可以使用大气电泳沉积方法来制造，并取代使用金属的高真空溅射的常规方法，该方法可能是昂贵的、耗时的、能量密集的，并且具有差的材料利用率。基于纳米颗粒的工程薄膜是获得非常高的光散射和反射表面的理想方式，这是高效太阳能电池中背反射器所需的特性。高太阳能电池性能和低成本制造方法的结合意味着所提出的基于纳米颗粒的背反射器将在竞争激烈的太阳能市场中取得成功，该市场2010年的销售额为820亿美元。除了太阳能之外，高度工程化的基于纳米颗粒的膜的其他应用包括用于高效平板显示器的背光反射器、用于自清洁和水脱落应用的超疏水表面、用于电子器件的纹理化/多孔结构以及用于电光器件的光子结构。该项目将促进上中西部以技术为基础的经济发展。与南达科他州州立大学的合作将培养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.