Unraveling the Advantages of 3-Terminal Perovskite/Silicon Tandem Solar Cells

Perovskite/silicon tandem solar cells are of increasing interest due to their high power conversion efficiencies (PCE) of over 30% and low fabrication costs. However, the stability of the perovskite cells cannot compete with the superior lifetime of silicon (Si) photovoltaics (&gt; 20 years), which threatens their commercialization. So far, most record perovskite/silicon tandem cells have been monolithically integrated and feature 2-terminal (2T) configuration. Hence the sub-cells are connected in series and the highest efficiencies can only be achieved if the perovskite top and Si bottom cells generate the same photocurrent. While the current matching can be well controlled by optimizing the bandgap of the top cell, a faster degradation of the perovskite top cell compared to the silicon bottom cell may cause a severe current mismatch during ageing. This current mismatch dramatically deteriorated the tandem efficiency to values lower than single-junction devices. To pinpoint this stability disparity and its consequences we have performed a thermal degradation study in a dry atmosphere. To overcome this limitation of 2T perovskite/Si tandem cells, we employ a 3-terminal (3T) tandem architecture which does not require current matching. Consequently, the long-term performance of 3T perovskite/Si cells will surpass the one of 2T devices.<br/>Here we show the first implementations of 3T tandem cells with <i>nip</i> and <i>pin </i>triple-cation perovskite top cells deposited on laser processed Interdigitated Back Contacted Silicon solar cells (Si IBC) with 1 cm² cell area. Our studies include current-voltage (I-V) and External Quantum Efficiency (EQE) analysis of the 3T tandem cells before and after ageing. Furthermore, Scanning Electron Microscope (SEM) imaging is used to check the conformal coating of the textured Si solar cells.