Thickness Optimization of Front and Recombination ITO in Monolithic Perovskite/Silicon Tandem Solar Cells

Optical losses of perovskite/silicon tandem solar cells can be effectively reduced by optimizing the thin-film layer thicknesses. Herein, the thicknesses of DC sputtered indium tin oxide (ITO) films, which serve as the front electrode and the recombination layer connecting the subcells, are optimized to reach high transparency and good lateral charge transport simultaneously. Optical simulations of the full perovskite/silicon tandem solar cell stacks are performed to find the optimum recombination and front electrode ITO thicknesses for solar cells as well as modules. Implementation of the optimized 25 nm front electrode ITO thickness in semitransparent single-junction perovskite solar cells increases the short-circuit density by 1.5 mA cm⁻² compared to the former reference thickness of 75 nm. Combined with an optimized 20 nm recombination ITO layer, high short-circuit density of 20.3 mA cm⁻² is reached in perovskite/silicon tandem solar cell devices, which is the highest reported value for planar front perovskite/silicon tandem solar cells to the best of knowledge. Further interface passivation enables 28.8% power conversion efficiency.