Perovskite/Silicon Tandem Solar Cells with Front Side Metallization Applied Prior to Top Cell Fabrication Enabling High Curing Temperatures

For the industrialization of large area perovskite silicon tandem solar cells a low-resistance and low-cost contact metallization needs to be established. On the one hand, curing or even firing temperatures as applied for screen-printing metallization of Si single junction cells are too high for perovskites. On the other hand, screen-printing pastes with very low curing temperatures have a reduced specific conductivity. Thus, they require wide Ag consuming contacts for a sufficiently low resistance. We present a concept which comprises screen-printing the front contacts onto an isolating layer located on the uppermost layer of the bottom cell before the perovskite top cell is applied. This allows higher curing temperatures and thus lower finger resistivities than in a low curing temperature screen-printing process on a perovskite solar cell. Furthermore, this concept avoids mechanical pressure on the soft perovskite material during cell interconnection. We expect that the latter aspect is beneficial to prevent shunting issues. The concept is shown for perovskite single junction solar cells in a proof-of-concept state. Furthermore, the advantage of higher curing temperatures regarding the Ag finger line resistance and the Ag/ITO contact resistivity is verified by an improvement due to additional sintering to $T\geq 330$ °C and $T\geq 260$ °C after curing, respectively.