Calibration of metastable tandem solar cells

The measurement of metastable (perovskite based) solar cells is a focus of the calibration lab of Fraunhofer ISE (CalLab PV Cells) to realize reliable measurements on emerging PV devices since several years. Rather than the certification of industrial grade stable solar cells, the aim here is to show the performance potential of new cell types in an early stage of development. Perovskite based tandems are promising devices for highest efficiencies, as they are able to overcome the physical limit efficiency of single junction solar cells. However, the correct measurement of tandem solar cells needs certain efforts in the spectral adjustments of the sun simulator. Procedures are therefore needed to take the spectral properties of both subcells into account. Spectral adaptions to the standard spectrum according to IEC60904-9 as it is adapted for single junction cells are not sufficient for the measurement of tandem devices. The presentation will illuminate the measurement of perovskite based tandem cells with special regard to spectral irradiance issues.