CAREER: Transparent, passivating, and carrier-selective heterojunction contacts for silicon and cadmium telluride solar cells

非技术性：这个CAREER项目旨在提高太阳能电池将阳光转化为电能的效率。该项目将探索太阳能电池电接触的材料科学和物理学。通过这样做，它将促进对这些接触如何限制电池操作的理解。每个太阳能电池都必须执行两个过程：将光转换为激发的电子，并以电流的形式提取这些电子。前一个过程由半导体吸收材料执行;后一个过程由两个电触点执行，吸收体夹在两个电触点之间。虽然太阳能电池是大规模生产的，现在产生的电力占美国消费的1%，仍有一些根本性的问题没有得到解答。研究界还不了解哪些特性决定了材料是否会产生良好的电接触，以及如何快速找到并制造具有所需特性的材料。该项目将通过将测量和模拟应用于现有模型系统，以及使用由此产生的理解来开发新联系的实验来回答这些问题。该项目的成功将为太阳能电池奠定基础，太阳能电池的效率比现在的电池高10-15%，将太阳能发电成本降低到每千瓦时3美分以下。反过来，预计这将加速太阳能的部署，导致到2030年美国17%的电力由太阳能产生，而不是照常营业情况下预计的5%。除了这些科学、环境和社会影响之外，该项目还将通过为期一周的“太阳能电池101”实践课程，培训社区学院、本科生和研究生，以适应目前美国26万个太阳能工作岗位。许多光伏（PV）技术已经达到了具有低非线性的吸收体材料。辐射复合率，因此可以支持接近详细平衡极限的电池电压，但是没有技术开发出相对理想的电接触，其是透明的、钝化吸收体表面并且从吸收体选择性地提取电子或空穴。该项目针对阻碍异质结接触理解和技术快速进步的关键问题，使用（1）将载流子选择性层、包含这些层的接触和包含这些接触的PV电池的特性联系在一起的表征套件，以及（2）使用干簇喷涂的新沉积技术，能够在不造成溅射损伤的情况下密切控制接触层的化学计量。这两个平台将应用于晶体硅和碲化镉光伏电池作为模型系统，因为这些技术有现成的高质量吸收剂（这使得对接触的功能的解释更加明显），可获得用于这些材料的先前开发的接触的集合以用于分析，但是理想的接触尚未被发现，而该项目在理解和技术上的任何进步都将产生巨大的研究和商业影响。在研究了最先进的现有接触的基础物理学之后，该项目将进展到沉积和测试迄今为止未开发的载流子选择性层，包括宽带隙、重掺杂、非晶或多晶III-V材料。该研究将解决实现27%效率的硅光伏电池和25%效率的碲化镉电池的关键障碍--良好的接触。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical:This CAREER project aims to increase the efficiency of conversion of sunlight into electricity by solar cells. The project will explore the materials science and physics of electrical contacts to solar cells. In so doing, it will advance the understanding of how these contacts limit the operation of the cells. Every solar cell must perform two processes: convert light into excited electrons and extract those electrons in the form of current. The former process is performed by a semiconductor absorber material; the latter by two electrical contacts between which the absorber is sandwiched. Although solar cells are mass manufactured and now generate 1% of the electricity consumed in the U.S., there are still fundamental questions that are unanswered. The research community does not yet understand which properties determine if a material will make an excellent electrical contact and how to quickly find and make materials with the desired properties. This project will provide answers to these questions with a combination of measurements and simulations applied to existing model systems, as well as experiments to use the resulting understanding to develop new contacts. Success in the project will lay the groundwork for solar cells that are 10-15% more efficient than today's cells, reducing the cost of solar electricity generation to below 3 cents per kilowatt-hour. This, in turn, is predicted to accelerate the deployment of solar energy, resulting in 17% of U.S. electricity being generated by solar in 2030 instead of the 5% projected in a business-as-usual scenario. In addition to these scientific, environmental, and societal impacts, this project will also train community college, undergraduate, and graduate students for the 260,000 solar jobs presently in the US through a week-long, hands-on "Solar Cell 101" course in which they make cells and modules from start to finish.Technical:Many photovoltaic (PV) technologies have arrived at absorber materials that have low non-radiative recombination rates and thus could support cell voltages approaching the detailed-balance limit, but no technology has developed comparatively ideal electrical contacts that are transparent, that passivate the absorber surface, and that selectively extract electrons or holes from the absorber. This project targets key questions that inhibit rapid progress in heterojunction contact understanding and technology using (1) a characterization suite that links together the properties of carrier-selective layers, contacts containing those layers, and PV cells containing those contacts, and (2) a new deposition technique using dry-cluster spraying to enable intimate control of the stoichiometry of contact layers without sputter damage. These two platforms will be applied to crystalline silicon and cadmium telluride PV cells as model systems, as these technologies have readily available high-quality absorbers (which makes interpretation of the function of the contacts more apparent), a collection of previously developed contacts for these materials is available for analysis but ideal contacts have yet to be discovered, and any advances in understanding and technology resulting from the project will have large research and commercial impact. After studying the underlying physics of state-of-the-art existing contacts, the project will progress to depositing and testing heretofore unexplored carrier-selective layers, including wide-bandgap, heavily doped, amorphous or polycrystalline III-V materials. This research will address the critical impediment--excellent contacts--to 27%-efficient silicon PV cells and 25%-efficient cadmium telluride cells.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.