Spectrometric Determination of Current Matching in Perovskite/Silicon Tandem Solar Cells

In two-terminal monolithic perovskite/silicon tandem solar cells, top and bottom cells are interconnected in series. To maximize the current of the entire tandem solar cell, current matching of the two sub-cells is needed. Thus, it is necessary to get access to the individual current of each sub-cell. As it is difficult to measure the absolute external quantum efficiency (EQE) for multijunction solar cells in general and especially if perovskite is involved, in this work, the spectrometric characterization technique enables important insight in the sub-cells’ current limitation. In this method, which has already been applied for III-V multijunction solar cells, current-voltage curves are recorded while the spectrum is systematically varied from a blue-rich to a red-rich spectrum. We apply this technique to perovskite/silicon tandem devices consisting of a silicon heterojunction bottom solar cell and top solar cell in the p-i-n architecture with different perovskite absorbers. In our example, a perovskite absorber with a bandgap of 1.68 eV the top solar cell limits the current, whereas current matching could be reached when using an absorber with a lower bandgap of 1.64 eV. Results from spectrometric characterization are then used to scale the EQEs. We show how optimization strategies for both sub-cells can be systematically derived from these results.