Tockhorn, P.; Wagner, P.; Kegelmann, L.; Stang, J.-C.; Mews, M.; Albrecht, S.; Korte, L.: Three-Terminal Perovskite/Silicon Tandem Solar Cells with Top and Interdigitated Rear Contacts. ACS Applied Energy Materials 3 (2020), p. 1381-1392
10.1021/acsaem.9b01800

Abstract:
We present a three-terminal (3T) tandem approachfor the interconnection of a perovskite top cell with aninterdigitated back-contact (IBC) silicon heterojunction (SHJ)bottom cell. The general viability of our cell design is verified withdrift-diffusion simulations indicating efficient charge carriertransport throughout the whole device and an efficiency potentialof≈27% by using readily available absorber and contact materials.Our experimental proof-of-concept device reaches a combinedPCE of 17.1% when both subcells are operating at their individualmaximum power point. To emulate different operation conditions,the current−voltage characteristics of both cells were obtained bymeasuring one subcell while the other cell was set to afixed biasvoltage. Only a slight mutual dependence of both subcells wasfound. As determined by electrical simulations, this dependence likely stems from the resistance of the electron contact on the cell’srear side, which is shared by both subcells. The optimization of this contact turns out to be a major design criterion for IBC 3Ttandems. We demonstrate that our current proof-of-concept cells are limited by this series resistance as well as by optical losses, andwe discuss pathways to approach the simulated efficiency potential by an optimized device design.