Development of dual junction GaInP/GaAs solar cells for high-performance concentrator photovoltaic quad-junction III-V/IV

The use of III-V and group IV compounds in the same heterostructure is of great interest for high performances solar cells under concentration. In fact, the combination of these III-V and group IV compounds can lead to interesting strategic bandgap choices and engineering to better match the absorption of the solar spectrum, and therefore better solar cell performance. The series-connected quad-junctions (4J) solar cell strategies have the potential to improve solar cells performance and therefore enable low-cost concentrator photovoltaic (CPV) systems, allowing lower levelized cost of electricity (LCOE) from a CPV system. This work presents the investigation of the performance of dual junction (2J) GaInP/GaAs that might be implemented as upper cells with group IV (SiGeSn) cells as bottom cells. The aim of this study is to validate the epitaxial structure and the fabrication process for future 4J cells development. Pitch is varied from 125 μm to 400 μm for two different size of cells, in order to optimize solar cells performance under concentration (X) In the range of 100X to 1000X. Solar cells demonstrated high fill factor (FF) values and ideality factors (n) approaching unity per subcell have been obtained in the range of 100X to 500X. A FF of 85% and 88% are obtained at a concentration of 1000X for the bigger and smaller cells respectively, for the narrowest pitch. These results close to the state-of-the-art are encouraging for the implementation of this 2J with IV bottom subcell for the purpose of high performance 4J.