Influence of the simulator spectrum on the calibration of multi-junction solar cells under concentration

The calibration of monolithic multi-junction (MJ) solar cells places high demands on the measurement setup. There exists a strong dependence of the I-V parameters on the incident spectrum. In this paper the influence of the high intensity simulator spectrum on the calibration of MJ concentrator cells is investigated taking a Ga_0.35In_0.65P/Ga_0.83In_0.17As dual-junction cell as example. It is shown that an unmatched simulator spectrum leads to an overestimation of the efficiency for the investigated dual-junction cell. Furthermore we observed different fill factor versus concentration behavior depending on which subcell is current limiting, probably caused by distributed series resistance effects. Finally, it is shown that the measured fill factor can serve as an indicator to identify whether an appropriate spectrum was used for the calibration under high illumination intensity.