Abstract
Perovskite-based tandem solar cells are of increasing interest as they approach commercialization. Here we use experimental parameters from optical spectroscopy measurements to calculate the limiting efficiency of perovskite–silicon and all-perovskite two-terminal tandems, employing currently available bandgap materials, as 42.0% and 40.8%, respectively. We show luminescence coupling between subcells (the optical transfer of photons from the high-bandgap to low-bandgap subcell) relaxes current matching when the high-bandgap subcell is a luminescent perovskite. We calculate that luminescence coupling becomes important at charge trapping rates (≤106 s–1) already being achieved in relevant halide perovskites. Luminescence coupling increases flexibility in subcell thicknesses and tolerance to different spectral conditions. For maximal benefit, the high-bandgap subcell should have the higher short-circuit current under average spectral conditions. This can be achieved by reducing the bandgap of the high-bandgap subcell, allowing wider, unstable bandgap compositions to be avoided. Lastly, we visualize luminescence coupling in an all-perovskite tandem through cross-section luminescence imaging.
Highlights
Perovskite-based tandem solar cells are of increasing interest as they approach commercialization
While there are several reports estimating all-perovskite and perovskite−silicon tandem efficiency limits and optimal optical designs, a majority focus on what can be achieved with current technologies and, critically, do not include all intrinsic recombination and luminescence coupling processes.[7−13] This means that tandem device optimization is currently being guided by incomplete models that do not capture all effects
We demonstrate that consideration of luminescence coupling between subcells, i.e., the emission of light from the high-bandgap subcell and its subsequent reabsorption in the low-bandgap subcell, relaxes the need for current matching compared to previous calculations that do not include the effect
Summary
Perovskite-based tandem solar cells are of increasing interest as they approach commercialization.
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