An on-sun comparison of GaInP2/GaAs tandem cells with top cell thickness varied

This study compares the on-sun performance of a set of GaInP₂/GaAs tandem cells with different GaInP₂ top-cell thicknesses. Because high-efficiency III-V cells are best suited to concentrating photovoltaic (CPV) applications, the cells were mounted on a two-axis tracker with the incident sunlight collimated to exclude all except the direct beam. Current-voltage (I-V) curves were taken throughout the course of several days, along with measurements of the direct solar spectrum. Our two major conclusions are: (1) GaInP₂/GaAs tandem cells designed for an "air mass 1.5 global" (AM 1.5G) or a "low aerosol optical depth" (Low AOD) spectrum perform the best, and (2) cells can be characterized indoors and modeled using outdoor spectra to predict the correct result. These results are equally valid for GaInP₂/GaAs/Ge triple-junction cells.