Polycrystalline silicon tunnelling recombination layers for high-efficiency perovskite/tunnel oxide passivating contact tandem solar cells

Perovskite/silicon tandem solar cells have rapidly advanced. Whereas efforts to enhance the device efficiency have mainly focused on top sub-cell improvements, the recombination layer connecting top and bottom sub-cells is critical for further progress. Here we present a perovskite/tunnel oxide passivating contact silicon tandem cell incorporating a tunnelling recombination layer composed of a boron- and phosphorus-doped polycrystalline silicon (poly-Si) stack. The poly-Si stack shows minimal interdiffusion of dopants. The strong adsorption ability of (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl) phosphonic acid on poly-Si substrate enables efficient charge-carrier transport and extraction, particularly for the top perovskite sub-cells. The device achieves an efficiency of 29.2% (28.76% certified) and retains 85% of its initial efficiency after 500 hours of continuous maximum power point tracking. Additionally, we provide insights into the carrier transport and tunnelling mechanisms, offering guidance for the design of intermediate layers in the pursuit of high-efficiency tandem solar cells. Silicon solar cells based on tunnel oxide passivating contact have industrial potential yet they are less investigated for tandem applications. Now Zheng et al. show a 28.67% certified efficiency for a perovskite/silicon tandem cell using a boron- and phosphorus-doped polycrystalline silicon connecting layer.