Fully-Textured Perovskite/Silicon Tandem Solar Cells Exceeding 30% Efficiency on Both Side Tunnel Oxide Passivating Contacted Bottom Cells

The bottom solar cell (BSC) plays a pivotal role in perovskite/silicon tandem solar cells (TSC), not only contributing to the total energy output but also influencing the perovskite formation with its surface properties when used as a substrate. A promising BSC is the TOPCon2 cell concept, featuring two full area tunnel oxide passivating contacts (TOPCon). In this study we explore their application in a fully textured tandem device, using the hybrid deposition method for the perovskite top cell processing tailored for compatibility with the industry-standard texture. We systematically investigate different TOPCon2 BSC designs, including p- and n-type base material, as well as planar and textured p-TOPCon rear side morphologies. Comparable implied open-circuit voltages (iVOC) were achieved with both TOPCon2 and silicon heterojunction (SHJ) reference BSCs. With their integration into TSCs, efficiencies up to 30.6% are demonstrated for the first time on TOPCon2 bottom cells with an industrial sized random pyramid front side texture. An in-depth loss analysis of this newly developed TOPCon- and the well-established baseline SHJ-based TSC demonstrates no fundamental difference in perovskite top cell formation and performance, which paves the way for the application of TOPCon BSCs for perovskite/silicon tandem solar cells that are more established in the industry.