Detailed-balance efficiency limits of two-terminal perovskite/silicon tandem solar cells with planar and Lambertian spectral splitters

We derive the photovoltaic conversion efficiency limit for two-terminal tandem solar cells with a perovskite top cell and silicon bottom cell with an embedded spectrum splitter. For large-bandgap top-cells, a spectrum splitter strongly enhances the efficiency because of enhanced light absorption and trapping. A Lambertian spectral splitter shows a significantly improved effect compared with a planar splitter. We find an ideal efficiency enhancement for a 500-nm thick top cell of 6% absolute for bandgaps above 1.75 eV. Vice versa, the use of a spectral splitter geometry enables the use of a thinner top cell. Using experimental parameters for perovskite cells, we show that for a top-cell bandgap of 1.77 eV a 2.7% absolute efficiency enhancement can be achieved. The calculations in this work show that integration of a spectral splitter into perovskite/silicon tandem cells for which the top cell is limiting the overall current can lead to a large increase in efficiency, even with realistic experimental losses and nonunity reflection of the spectral splitter. (C) The Authors.

Automated summary

This study investigates the efficiency limit enhancement of perovskite/silicon tandem solar cells using a spectrum splitter. The results show that the spectrum splitter technique can significantly improve the efficiency, especially for large bandgap top cells. Lambertian spectral splitter exhibits better performance compared to planar splitter. With the consideration of experimental losses and nonunity reflection, the integration of a spectral splitter into the tandem cells can lead to a large increase in efficiency.