ACT/SGER: Metastable Titania-Germanium (Ti02-Ge) Nanocomposites for Photovoltaic Applications

ACT/SGER：用于光伏应用的亚稳态二氧化钛-锗 (Ti02-Ge) 纳米复合材料

• 批准号: 0441619
• 负责人: S. Ismat Shah
• 金额: --
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0441619&HistoricalAwards=false
• 关键词: ACT; SGER; Metastable; Titania; Germanium

Nanostructured titania (TiO2) is a promising semiconductor for photovoltaic applications due to its stability, chemical inertness, cost, etc. The optical gap of titania is 3.2 eV that lies in the ultraviolet region of the solar spectrum. However, the peak of the solar spectrum is in the visible region. Therefore, to increase the efficiency of the photovoltaic processes, titania nanoparticles are customized by various methods in order to make them useful in the visible light. We propose to study a new nanostructured material, titania-germanium which will be a stable alternative to dye sensitized titania. We will use already mature deposition techniques, e.g. sputtering and metallorganic chemical vapor deposition, to synthesize the samples. Preliminary experiments of composite samples using selected area diffraction analyses in a transmission electron microscope showed uniform distribution of germanium nanoclusters (quantum dots) in the titania matrix. The formation of elemental germanium nanodots is facilitated by the relatively higher heat of formation of germanium oxide, compared to that of titania. The size of the germanium nanodots will be modulated across the thickness of the thin films by controlled annealing techniques. Such size variation will allow the possibility to use quantum dot size related change in the bandgap of germanium nanodots to sensitize titania and improve its photovoltaic properties. The Approaches to Combat Terrorism Program in the Directorate for Mathematics and Physical Sciences supports new concepts in basic research and workforce development with the potential to contribute to national security. To combat diffused and hidden terrorist activities, there is an obvious need for self-powered portable devices. For this purpose, solar electric power is an ideal renewable energy source. Currently, crystalline or amorphous silicon solar cells with efficiency to convert solar power to usable electricity as high as 20-30% are possible and even commercially produce. Crystalline silicon suffers from the complexity of the fabrication process where as relatively inexpensive amorphous silicon (a-Si) photovoltaics have a fundamental drawback of light induced degradation of photovoltaic properties. We propose to study a new stable material titania-germanium for photovoltaic applications. Titania absorbs only high-energy ultraviolet component of solar energy. Several schemes have been devised to overcome this limitation since the majority of the solar light is in the visible range. Forming titania-germanium nanocomposite is a new method of inducing visible light absorption in titania. Germanium serves as the light absorber. Ge, in the bulk form, absorbs only the infrared component of the solar energy. By forming nanometer size germanium clusters, also known as nanodots, the absorption properties of Ge can be varied from infrared to visible, thereby improving the solar light absorption efficiency of the titania-germanium nanocomposite. Fabrication of such materials will require the use of techniques that are already developed. The proposed study includes the fabrication of TiO2-Ge nanocomposite, its complete structural and electronic characterization, and investigation of its photovoltaic properties.

纳米二氧化钛(TiO2)具有稳定性好、化学惰性好、成本低廉等优点，是一种很有前途的光伏半导体材料，其光学禁带为3.2 eV，位于太阳光谱的紫外区。然而，太阳光谱的峰值在可见光区域。因此，为了提高光伏过程的效率，人们通过各种方法对二氧化钛纳米颗粒进行定制，以使其在可见光下有用。我们建议研究一种新的纳米结构材料--二氧化钛-锗，它将成为染料敏化二氧化钛的稳定替代品。我们将使用已经成熟的沉积技术，例如溅射和金属有机化学气相沉积来合成样品。利用透射电子显微镜的选区衍射分析对复合样品进行的初步实验表明，锗纳米团簇(量子点)均匀分布在二氧化钛基质中。与二氧化钛相比，氧化锗的生成热相对较高，有利于元素锗纳米点的形成。锗纳米点的尺寸将通过控制退火技术在薄膜厚度上进行调节。这样的尺寸变化将使人们有可能利用与量子点尺寸相关的Ge纳米点带隙变化来敏化二氧化钛，并改善其光伏性能。数学和物理科学局的反恐方法方案支持基础研究和劳动力发展方面的新概念，有可能对国家安全作出贡献。为了打击扩散和隐藏的恐怖活动，显然需要自给自足的便携式设备。为此，太阳能发电是一种理想的可再生能源。目前，晶体或非晶硅太阳能电池将太阳能转化为可用电能的效率高达20%-30%是可能的，甚至可以商业化生产。晶硅存在制造工艺的复杂性，其中作为相对便宜的非晶硅(a-Si)光伏具有光致光伏性能退化的根本缺点。我们建议研究一种用于光伏应用的新型稳定材料二氧化钛-锗。二氧化钛只吸收太阳能中的高能紫外线成分。由于大多数太阳光都在可见光范围内，因此已经设计了几种方案来克服这一限制。形成二氧化钛-锗纳米复合材料是一种在二氧化钛中诱导可见光吸收的新方法。锗起到光吸收的作用。GE以散装形式只吸收太阳能的红外成分。通过形成纳米尺寸的锗团簇，也称为纳米点，Ge的吸收性能可以从红外到可见光变化，从而提高二氧化钛-锗纳米复合材料的太阳光吸收效率。这种材料的制造将需要使用已经开发的技术。本论文的研究内容包括：二氧化钛-锗纳米复合材料的制备，其完整的结构和电子表征，以及对其光伏性能的研究。