Highly passivated TOPCon bottom cells for perovskite/silicon tandem solar cells

Tunnel oxide passivated contact (TOPCon) silicon solar cells are rising as a competitive photovoltaic technology, seamlessly blending high efficiency with cost-effectiveness and mass production capabilities. However, the numerous defects from the fragile silicon oxide/c-Si interface and the low field-effect passivation due to the inadequate boron in-diffusion in p-type polycrystalline silicon (poly-Si) passivated contact reduce their open-circuit voltages (V_OCs), impeding their widespread application in the promising perovskite/silicon tandem solar cells (TSCs) that hold a potential to break 30% module efficiency. To address this, we have developed a highly passivated p-type TOPCon structure by optimizing the oxidation conditions, boron in-diffusion, and aluminium oxide hydrogenation, thus pronouncedly improving the implied V_OC (iV_OC) of symmetric samples with p-type TOPCon structures on both sides to 715 mV and the V_OC of completed double-sided TOPCon bottom cells to 710 mV. Consequently, integrating with perovskite top cells, our proof of concept of 1 cm² n-i-p perovskite/silicon TSCs exhibit V_OCs exceeding 1.9 V and a high efficiency of 28.20% (certified 27.3%), which paves a way for TOPCon cells in the commercialization of future tandems.