Bismuth Rudorffites: Promising New Materials for the Top Cell in Solution Processed Tandem PV

非技术描述：降低太阳能发电总成本的有效方法是提高太阳能电池的电力转换效率，特别是如果能在制造成本增加最小的情况下实现这一点。这一目标可以通过在硅太阳能电池上增加一个低成本的高带隙太阳能电池来实现。到目前为止，这种顶层电池最有希望的材料是杂化钙钛矿。这些新材料具有非常高的性能，但它们含有有毒的铅，并引起环境问题。该项目的重点是开发新的低毒的铋基高禁带半导体，这些半导体有可能被替代。该团队正在探索一种最近发现的名为rudorffite的铋材料，并正在建立对这些无毒半导体的材料结构、性能和加工之间的关键关系的理解。这项基础研究能够从无毒元素开发出低成本的串联太阳能电池，从而产生重大的社会影响。此外，该项目还培训了一名研究生、一名博士后学者和几名本科生，并通过西雅图的太平洋科学中心和清洁能源研究所的清洁能源大使计划吸引了公众。技术说明：铋基半导体是有趣的无毒光电材料，因为Bi3+与6s2孤对的部分氧化有望导致与铅基混合钙钛矿材料类似的缺陷容忍度。最近发现的铋榴辉石特别令人感兴趣，因为它们表现出适合串联太阳能电池的高禁带。来自铋矿的太阳能电池的效率只有几个百分点，但它们有可能实现更高的效率。在这个项目中，研究人员正在进行一系列的基础研究，以探索溶液生长的铋红宝石在光电应用中的潜力，了解导致潜在性能限制的基本工艺，并开发克服这些限制的策略。初步研究表明，纳米层的形貌和掺杂/合金化对这些材料的光电性能有很大影响。该项目利用组合喷涂层方法来合成大量的合金/掺杂成分，绝对强度光致发光来评估准费米能级分裂，以及基于光电导的方法来评估载流子扩散长度。其目标是将光伏材料的结构和加工与最重要的材料性能指标联系起来。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical Description: An effective way to decrease the overall cost of electricity from solar energy is to increase the power conversion efficiency of solar cells, particularly if it can be accomplished with minimal increase in manufacturing cost. This goal can be achieved by adding a low-cost high-bandgap solar cell on top of a silicon solar cell. To date, the most promising materials for this top-cell are hybrid perovskites. These new materials have extraordinarily high performance, but they contain lead, which is toxic and raises environmental concerns. This project focuses on developing new low-toxicity bismuth-based high bandgap semiconductors that can potentially be used instead. The team is exploring a recently discovered class of bismuth materials called rudorffites and is building an understanding of the critical relationships between material structure, properties, and processing for these non-toxic semiconductors. This basic research could have significant societal impact by enabling the development of low-cost tandem solar cells from non-toxic elements. Furthermore, the project provides training of a graduate student, a postdoctoral scholar, and several undergraduates, as well as engage the public though the Pacific Science Center in Seattle and the Clean Energy Institute's Clean Energy Ambassadors program.Technical Description: Bismuth-based semiconductors are interesting non-toxic optoelectronic materials since the partial oxidation of Bi3+ with the 6s2 lone pair is expected to lead to similar defect tolerance as the lead-based hybrid perovskites. The recently discovered bismuth rudorffites are of particular interest since they exhibit high bandgaps suitable for tandem solar cells. Solar cells from bismuth rudorffites have a few-percentage efficiency, but they have the potential for much higher efficiency. In this project, investigators are conducting a body of fundamental research to explore the potential of solution grown bismuth rudorffites for optoelectronic applications, to understand the fundamental processes responsible for potential performance limitations and to develop strategies to overcome them. Preliminary research shows that nanoscale layer morphology and doping/alloying have a tremendous effect on the optoelectronic quality of these materials. The project utilizes combinatorial spray coating methods to synthesize a large number of alloy/doping compositions, absolute intensity photoluminescence to assess quasi-Fermi level splitting, and photoconductivity-based methods to assess the carrier diffusion length. The goal is to connect structure and processing with the most important material performance metrics for photovoltaic materials.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.