Interfacial defect mitigation in HJT bottom cells for improved efficiency of monolithic perovskite/Si tandem solar cells

Monolithic perovskite/silicon tandem solar cells (PSTSCs) offer a promising path to surpass the efficiency limits of single-junction photovoltaics at low production costs. However, interface defects and current mismatch between subcells continue to limit their full performance potential, particularly in the silicon heterojunction (HJT) bottom cell. To address this issue, we propose a Nafion-based edge isolation treatment followed by thermal curing to suppress interfacial recombination and improve carrier selectivity in the HJT structure. In this study, we demonstrate that this approach enhances the bottom cell efficiency to 23.53 %, with a short-circuit current density (J sc ) of 39.75 mA/cm 2 , an increase in open-circuit voltage (V oc ) from 709 to 728 mV, and an improvement in fill factor (FF) from 72.81 % to 81.28 %. Incorporating this optimized HJT bottom cell into a 2-terminal perovskite/HJT tandem configuration, we achieved a power conversion efficiency of 28.84 % over a 1 cm 2 active area. These results highlight the importance of interface engineering in boosting tandem performance and optimizing the fabrication process for PSTSCs toward industrial integration.