Novel Cells and Systems for Intermediate Concentration Photovoltaics

在过去的几年中，太阳能光伏（PV）的成本急剧下降，因此它现在是许多司法管辖区中最便宜且增长最快的公用事业规模电力供应形式。大多数光伏能源由硅模块提供，其中电池成本现在仅占整个系统成本的一小部分，使得电池效率在推动进一步降低能源成本方面至关重要。虽然全球部署的所有光伏电池的平均效率仅为~18%，但商业规模的电池已被证明具有26.7%的效率，并且部署的电池效率预计将在未来5 - 10年内继续上升，基本上限于29.4%。在另一种称为聚光器光电转换（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。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聚集所缓解。尽管有这些好处，但与大规模部署的简单得多的太阳能模块相比，CPV系统仍然昂贵。 为了加速全球光伏部署，需要在电池/系统层面制定新的战略，以进一步提高电池效率并降低系统成本。尚未充分探索的一个途径是考虑在5 - 200倍范围内的中间光学聚集，其中聚集的主要益处-使用更高成本更高效率的电池-仍然可以累积，但是聚集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剖面被动跟踪系统。在最低浓度（5 - 10倍），非跟踪设计是可能的，我们将开发高光通量浓缩器系统。在电池层面，中间浓度使得引入更复杂的制造工艺（例如光刻、CVD生长和离子注入）成为可能，这些工艺目前对于1个太阳的应用来说过于昂贵。作为一个例子，我们已经从理论上表明，使用重复的硅电池作为串联电池的底部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/测试用于高效中间浓度应用的新电池设计。 该研究计划的预期成果是对中等浓度光化学的科学和技术机会的深入和全面的了解，为未来的工作提供长期的概念路线图。我们将与加拿大工业界合作，开发新的高效、低成本光伏电池和系统，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.