Novel Cells and Systems for Intermediate Concentration Photovoltaics

在过去的几年里，太阳能光伏(PV)的成本已经大幅下降，以至于它现在是许多司法管辖区最便宜、增长最快的公用事业规模电力供应形式。大部分光伏能源由硅组件提供，其中电池成本现在只占系统总成本的一小部分，使电池效率成为推动能源成本进一步降低的首要因素。虽然全球部署的所有光伏电池的平均效率只有~18%，但商业规模的电池效率已被证明达到26.7%，预计未来5-10年，部署的光伏电池效率将继续提高，通过Auger重组从根本上限制在29.4%。在另一种被称为聚光器光伏(CPV)的方法中，太阳光通过精确跟踪太阳的光学系统聚焦到太阳能电池上约1000倍。在这种方法中，可以使用效率达到创纪录的47.1%的非常高效率的多结太阳能电池，因为它们的高成本被高水平的光学集中减轻了。尽管有这些好处，但与大规模部署的简单得多的太阳能组件相比，CPV系统仍然很昂贵。为了加速全球光伏的部署，需要在电池/系统层面采取新的战略，以进一步提高电池效率和降低系统成本。一种尚未充分探索的途径是考虑在5-200倍的范围内的中间光学浓度，在这种情况下，浓缩的主要好处--使用成本更高、效率更高的电池--仍然可以积累，但集中器系统的成本和复杂性可以大大降低。在系统层面，对光学元件和跟踪系统的要求变得不那么严格，我们将开发适合商业屋顶应用的新型低调无源跟踪系统。在最低浓度(5-10倍)下，无跟踪设计是可能的，我们将开发高光通量聚光器系统。在电池层面，中等浓度使引入更复杂的制造工艺成为可能，如光刻、CVD生长和离子注入，这些工艺目前对于单太阳应用来说过于昂贵。作为一个例子，我们已经从理论上证明，使用重复的硅电池作为串联电池的基极，为顶部电池开辟了新的材料选择，同时仍然实现了高效率。我们将进一步发展这一概念，并设计/制造/测试用于高效率中等浓度应用的新电池设计。这一研究计划的预期成果是对中浓度光伏的科技机遇有了深刻而全面的了解，为未来的工作提供了长期的概念路线图。我们将与加拿大业界合作，开发新的高效率、低成本的光伏电池和系统，在加拿大部署并出口到全球市场。

In the last few years, there have been dramatic decreases in the cost of solar photovoltaics (PV) such that it is now the least expensive and most rapidly growing form of utility-scale electricity supply in many jurisdictions. Most PV energy is provided by silicon modules, where the cell cost is now only a small fraction of the overall system cost, making cell efficiency paramount in driving further reduction in energy cost. While the average efficiency of all PV cells deployed globally is only ~18%, commercial size cells have been demonstrated with an efficiency of 26.7% and deployed cell efficiencies are expected to continue to rise for the next 5-10 years, fundamentally limited to 29.4% by Auger recombination. In an alternate approach called concentrator photovoltaics (CPV), sunlight is focussed ~1000X onto a solar cell by an optical system that accurately tracks the sun. In this approach, very high efficiency multijunction solar cells which have reached a record 47.1% efficiency can be used because their high cost is mitigated by the high level of optical concentration. Despite these benefits, CPV systems remain costly as compared to the much simpler solar modules deployed at scale. In order to accelerate global PV deployment, new strategies at the cell/system level are required to further increase cell efficiency and lower system costs. One avenue that has not been fully explored is consideration of intermediate optical concentrations, in the range of 5-200X, where the main benefit of concentration - the use of higher-cost higher-efficiency cells - can still be accrued, but the cost and complexity of the concentrator system can be greatly reduced. At the system level, requirements for optical components and tracking systems become less stringent and we will develop novel low profile passive tracking systems, suitable for commercial rooftop applications. At the lowest concentrations (5-10X), non-tracking designs are possible and we will develop high optical-throughput concentrator systems. At the cell level, intermediate concentration makes it feasible to introduce more complex fabrication processes such as photolithography, CVD growth and ion implantation that are currently too costly for 1-sun applications. As one example, we have shown theoretically that use of repeated silicon cells for the base of a tandem cell opens up new material choices for the top cell, while still achieving high efficiency. We will further develop this concept and design/fabricate/test new cell designs for high-efficiency intermediate concentration applications. The anticipated outcome of this research program is a deep and comprehensive understanding of the scientific and technological opportunities of intermediate concentration photovoltaics, providing a long-term conceptual roadmap for future work. Working with Canadian industry, we will develop new high-efficiency and low-cost PV cells and systems for deployment in Canada and for export to the global market.