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

Monolithic perovskite/silicon tandem solar cells recently surpass the efficiency of silicon single-junction solar cells. Most tandem cells utilize >250 mu m thick, planarized float-zone (FZ) silicon, which is not compatible with commercial production using <200 mu m thick Czochralski (CZ) silicon. The perovskite/silicon tandem cells based on industrially relevant 100 mu m 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 approximate to 0.02 eV when reducing the silicon thickness from 280 to 100 mu m. 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.