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 TOPCon ² 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 TOPCon ² 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 (i V _OC ) were achieved with both TOPCon ² and silicon heterojunction (SHJ) reference BSCs. With their integration into TSCs, efficiencies up to 30.6% are demonstrated for the first time on TOPCon ² 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.