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

TL;DR

This paper derives efficiency limits for two-terminal perovskite/silicon tandem solar cells with spectral splitters, showing significant potential for efficiency improvements especially with Lambertian splitters and high-bandgap top cells.

Contribution

It introduces a detailed theoretical analysis of spectral splitters in tandem cells, quantifying efficiency gains and optimal configurations for different spectral splitter geometries.

Findings

Lambertian splitters significantly improve efficiency over planar ones.

Efficiency gains up to 6% absolute for high-bandgap top cells.

Experimental parameters suggest a 2.8% absolute efficiency increase at 1.77 eV bandgap.

Abstract

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 to a planar splitter: we find an ideal efficiency enhancement in the thermodynamic limit 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 2.8% absolute efficiency can be gained. The calculations in this work show that integration of a spectral splitter into perovskite/silicon tandem cells with a top bandgap above 1.7 eV can lead to a large increase in efficiency, even with realistic experimental losses and non-unity reflection of the spectral splitter.