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27.9% Efficient Monolithic Perovskite/Silicon Tandem Solar Cells on Industry Compatible Bottom Cells

Köhnen, Eike; Wagner, Philipp; Lang, Felix; Cruz, Alexandros; Li, Bor; Roß, Marcel; Jošt, Marko; Morales-Vilches, Anna B.; Topič, Marko; Stolterfoht, Martin; Neher, Dieter; Korte, Lars; Rech, Bernd; Schlatmann, Rutger; Stannowski, Bernd; Albrecht, Steve

Monolithic perovskite/silicon tandem solar cells recently surpass the efficiency of silicon single‐junction solar cells. Most tandem cells utilize >250 μm thick, planarized float‐zone (FZ) silicon, which is not compatible with commercial production using <200 μm thick Czochralski (CZ) silicon. The perovskite/silicon tandem cells based on industrially relevant 100 μm thick CZ‐silicon without mechanical planarization are demonstrated. The best power conversion efficiency (PCE) of 27.9% is only marginally below the 28.2% reference value obtained on the commonly used front‐side polished FZ‐Si, which are about three times thicker. With both wafer types showing the same median PCE of 27.8%, the thin CZ‐Si‐based devices are preferred for economic reasons. To investigate perspectives for improved current matching and, therefore, further efficiency improvement, optical simulations with planar and textured silicon have been conducted: the perovskite's bandgap needs to be increased by ≈0.02 eV when reducing the silicon thickness from 280 to 100 μm. The need for bandgap enlargement has a strong impact on future tandem developments ensuring photostable compositions with lossless interfaces at bandgaps around or above 1.7 eV.
Published in: Solar RRL, 10.1002/solr.202100244, Wiley