Three-Terminal Perovskite/Silicon Tandem Solar Cells with Top and Interdigitated Rear Contacts

We present a three-terminal (3T) tandem approach for the interconnection of a perovskite top cell with an interdigitated back-contact (IBC) silicon heterojunction (SHJ) bottom cell. The general viability of our cell design is verified with drift-diffusion simulations indicating efficient charge carrier transport throughout the whole device and an efficiency potential of ≈27% by using readily available absorber and contact materials. Our experimental proof-of-concept device reaches a combined PCE of 17.1% when both subcells are operating at their individual maximum power point. To emulate different operation conditions, the current–voltage characteristics of both cells were obtained by measuring one subcell while the other cell was set to a fixed bias voltage. Only a slight mutual dependence of both subcells was found. As determined by electrical simulations, this dependence likely stems from the resistance of the electron contact on the cell's rear side, which is shared by both subcells. The optimization of this contact turns out to be a major design criterion for IBC 3T tandems. We demonstrate that our current proof-of-concept cells are limited by this series resistance as well as by optical losses, and we discuss pathways to approach the simulated efficiency potential by an optimized device design.