AZUR's new 5C46 CPV cell: Final design for optimized outdoor performance

With the 5C46 AZUR SPACE is introducing its new CPV cell into the market. This upright metamorphic AlInGaP/InGaP/AlInGaAs/InGaAs/Ge 5-junction cell uses sub-cell materials comparable to AZUR's 4G32 space solar cell but has an additional InGaP junction. The cell design is laid out for optimum module performance at operating conditions. As reported earlier, the bandgaps of the sub-cells have been selected to avoid the dips in the AM1.5d spectrum for cell temperatures up to 90°C. The optimization of the 5C46 has been monitored by the manufacture of 5C46-based commercial CPV modules equipped with secondary lenses and rating of these modules at Fraunhofer ISE. A very good efficiency of 31.7% at Concentrator Standard Operating Conditions (CSOC, lens array aperture) has been reached corresponding to a power boost of 17.5% compared to reference modules equipped with 3C44 cells. In the last optimization step, the thicknesses of the sub-cells have been adjusted to achieve current matching under operating conditions on module level. The paper describes the method used for modelling and the calculation of the optimum thicknesses. It involves the determination of the absolute quantum efficiency of the bare cell and accounts for the thermal band-gap shifts as well as the optical effects due to mounting of the secondary and the transmission of the primary lens. First outdoor results of modules equipped with the final 5C46 design confirm that the current-matching for operating condition on module level was successfully achieved by the described method.