Monolithic multi-junction III-V solar cells with optimal 1 eV subcell

对III-V多结太阳能电池的兴趣目前是由空间应用驱动的，但这些电池的最大潜在市场肯定是陆地。在这方面，利用高效III-V多结太阳能电池的陆地聚光器系统越来越多地被考虑用于大规模发电。然而，这种长期寻求的III-V多结太阳能电池在大规模消费应用中的集成取决于建立具有更高效率和显著材料成本节省的新的可扩展技术的能力。最先进的多结太阳能电池生长在块状砷化镓（GaAs）或锗（Ge）衬底上，这些衬底非常昂贵。为了克服这些技术瓶颈，本项目旨在设计、开发和优化一种新型单片III-V多结太阳能电池，其最佳子电池为1 eV。这里的关键策略是在III-V太阳能电池的制造中引入硅锗薄（SiGeSn）半导体。所提出的设计包括InGaP/InGaAs/SiGeSn/Ge结。SiGeSn带隙可以在1 eV左右调整，同时与Ge晶格匹配，这一事实将实现太阳光谱的最佳吸收，这对于进一步提高转换效率至关重要。此外，高结晶质量的SiGeSn和Ge层可以在硅晶片上生长的事实也将消除对体Ge的需要，并且使得能够将所提出的太阳能电池集成到机械坚固且廉价的Si处理基板上。这是实现开发III-V族太阳能电池技术大规模地面应用所需的成本效益的关键。

The interest in III-V multi-junction solar cells is currently driven by space applications, but the largest potential market for these cells is certainly terrestrial. In this regard, terrestrial concentrator systems utilizing high-efficiency III-V multi-junction solar cells have been increasingly considered for large-scale generation of electrical power. However, this long-sought for integration of III-V multi-junction solar cells in large-scale consumer applications depends on the ability to establish new scalable technologies with higher efficiencies and significant material cost saving. The state-of-the-art multi-junction solar cells are grown on bulk gallium arsenide (GaAs) or germanium (Ge) substrates, which are prohibitively expensive. To circumvent these technological bottlenecks, this project aims at designing, developing, and optimizing a novel monolithic III-V multi-junction solar cells with an optimal 1eV subcell. The key strategy here is to introduce silicon-germanium-thin (SiGeSn) semiconductor in the fabrication of III-V solar cells. The proposed design consists of InGaP/InGaAs/SiGeSn/Ge junctions. The fact that SiGeSn bandgap can be tuned around 1eV while being lattice-matched to Ge will enable an optimal absorption of solar spectrum, which is central to further enhance the conversion efficiency. Moreover, the fact that high-crystalline quality SiGeSn and Ge layers can be grown on silicon wafers will also eliminate the need for bulk Ge and enable the integration of the proposed solar cells onto mechanically robust and inexpensive Si handle substrates. This is key to achieve the cost-effectiveness necessary for the development of large-scale, terrestrial applications of III-V solar cell technologies.