Palliating the efficiency loss due to shunting in perovskite/silicon tandem solar cells through modifying the resistive properties of the recombination junction

As the efficiency of commercial crystalline silicon solar cells approaches its maximum theoretical value, tandem architectures are becoming increasingly popular to continue the push to higher photovoltaic performances. Thin-film materials are particularly interesting partners for silicon wafers due to their potential cost effectiveness and ease of fabrication. However, in large scale thin-film coatings, particularly for perovskite materials, avoiding the formation of point shunts is a challenge. This study investigates the sensitivity of perovskite/silicon tandems to such shunts and whether or not optimising the lateral and transverse resistances of the recombination junction can reduce the negative effects of these defects. To do so, the inhomogeneous characteristic of shunts is reproduced by modelling tandem cells with an array of scaled equivalent circuit elements connected in parallel. It is shown that by optimising the resistive properties of the interconnection, there can be an important quenching effect on shunts present in the top cell, resulting in a significant increase in the overall cell efficiency at STC and under low light conditions. These findings give a clear pathway on how to bridge the efficiency gap between small laboratory cells, which can be selected shunt free, and industry scale devices, which are more prone to localised shunting. As more focus is brought to scaling up perovskite/silicon tandem solar cell technologies, it has been found that optimising the transverse resistance of the interconnection leads to significant quenching of shunt defects in the perovskite sub-cell.