Solution-processed perovskite-kesterite reflective tandem solar cells

Solution-processed solar cells are promising as low-cost alternatives to the first-generation solar cells. Combining two solution-processed devices in a tandem structure can potentially achieve a high efficiency while maintaining a relatively low fabrication cost. Here we present a tandem combining solution-processed perovskite and CZTSSe solar cells in a reflective configuration. The perovskite cell with a large bandgap acts as a spectral filter reflecting the sub-bandgap photons to a low bandgap CZTSSe cell. A total efficiency of 16.1% has been obtained in a four-terminal measurement, higher than each of the sub-cells. These results show the potential of solution-processed tandem solar cell with perovskite and kesterite in achieving a high efficiency with a low fabrication cost.