International Research Fellowship Program: Fabrication and Characterization of Inexpensive Solar Cells Based on Dye-Sensitized TiO2 Nanoparticles

[402129]农业农业国际研究奖学金计划使美国科学家和工程师能够在国外进行三到二十四个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Alexander G. Agrios博士与瑞士洛桑联邦理工学院的Michael Graetzel博士以及瑞典乌普萨拉大学的Anders Hagfeldt博士进行为期22个月的研究。化石燃料燃烧产生的能源释放出二氧化碳、氮氧化物、硫氧化物、汞等污染物，造成全球气候变化、酸雨、光化学烟雾等问题。硅基太阳能技术已经存在了几十年，但成本太高，无法与化石燃料竞争。显然，如果太阳能生产的成本能够降低到用太阳能转换取代化石燃料消耗的水平，环境效益将是巨大的。1991年，瑞士洛桑联邦理工学院（EPFL）的Michael Gratzel博士的实验室发明了一种新型太阳能电池。与硅太阳能电池不同，所谓的染料敏化太阳能电池（DSSC），或Gratzel电池，使用一种不同的半导体，二氧化钛（TiO2），其小（10纳米）颗粒被一种吸收光的分子（染料）所覆盖，在吸收光时向TiO2注入电子。在硅电池中，硅晶体中的任何杂质或缺陷都会削弱太阳能转换的效率，需要高材料加工成本才能达到必要的硅纯度。相比之下，Gratzel电池的基本机制不同，对TiO2纳米晶体的要求要低得多，因此技术成本要低得多。Agrios博士正在与EPFL的Gratzel博士一起研究新一代染料敏化太阳能电池的制造。在过去十年中发展起来的一种静电逐层薄膜生产技术，正被用于生产两种新型的DSSC。这种新型电池有望更好地收集全光谱的太阳能，并提高能量转换效率。瑞典乌普萨拉大学（Uppsala University）的安德斯·哈格菲尔德（Anders Hagfeldt）博士与格拉策尔博士密切合作了十年。他的实验室小组开发了一套先进的染料敏化太阳能电池表征技术，被称为“工具箱”。该项目的第二阶段将在Hagfeldt博士的实验室进行，使用他的技术来了解在EPFL生产的层状TiO2薄膜中发生的电子过程。此外，Hagfeldt博士还开发了一种无需高温步骤就能生产DSSCs的工艺，这使得这些细胞可以在廉价、柔性的塑料衬底上连续制造。该工艺将应用于逐层Gratzel电池，以确定逐层薄膜沉积方法是否与低温生产技术兼容。

0402129AgriosThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-two-month research fellowship by Dr. Alexander G. Agrios to work with Dr. Michael Graetzel at Ecole Polytechnique Federale de Lausanne in Switzerland and with Dr. Anders Hagfeldt at Uppsala University of Sweden.Energy production from the combustion of fossil fuels releases carbon dioxide, nitrogen and sulfur oxides, mercury, and other pollutants, resulting in global climate change, acid rain, and photochemical smog, among other problems. Silicon-based solar energy technology has existed for decades but has been too costly to compete with fossil fuel use. Clearly, if the cost of solar energy production can be reduced to a level at which the displacement of fossil fuel consumption by solar energy conversion becomes practical, the environmental benefit would be enormous. In 1991, a novel type of solar cell was invented in the laboratory of Dr. Michael Gratzel at Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland. Unlike silicon solar cells, the so-called dye-sensitized solar cell (DSSC), or Gratzel cell, uses a different semiconductor, titanium dioxide (TiO2), small (10 nm) particles of which are coated with a light-absorbing molecule (dye), which injects electrons into the TiO2 upon light absorption. In a silicon cell, any impurities or defects in the silicon crystals cripple the efficiency of solar energy conversion, requiring high materials processing costs to achieve the necessary silicon purity. In contrast, the fundamentally different mechanism of the Gratzel cell places much less stringent requirements on the TiO2 nanocrystals, resulting in a far less expensive technology. Dr. Agrios is working on the fabrication of a new generation of dye-sensitized solar cells with Dr. Gratzel at EPFL. An electrostatic layer-by-layer technique for film production, developed in the past decade, is being used to produce two new types of DSSC. The new cells are expected to exhibit better harvesting of the full spectrum of solar light and improved energy conversion efficiency. Dr. Anders Hagfeldt, at Uppsala University in Sweden, has been in close collaboration with Dr. Gratzel for a decade. His laboratory group has developed a suite of advanced characterization techniques for dye-sensitized solar cells known as the "toolbox". The second phase of the project will be spent at Dr. Hagfeldt's laboratory, using his techniques to understand electronic processes occurring in the layered TiO2 films produced at EPFL. In addition, Dr. Hagfeldt has developed a process for producing DSSCs without a high-temperature step, which allows the cells to be continuously fabricated on cheap, flexible plastic substrates. This process will be applied to the layer-by-layer Gratzel cells to determine whether the method of layer-by-layer film deposition is compatible with a low-temperature production technique.