Toward silver-free back contact silicon solar cells: Dual-polarity screen-printed aluminum contacts on poly-Si/SiOX passivated contacts

Tunnel oxide passivated back contact (TBC) silicon solar cells, featuring excellent passivation, high carrier selectivity, and superior optical performance, have emerged as a leading architecture for next-generation high-efficiency photovoltaics. However, the high silver consumption required for metallisation presents increasing challenges for cost reduction and terawatt-scale manufacturing. Here, we report a dual-polarity aluminum contact engineering strategy for silver-free back contact silicon solar cells, enabled by polarity-dependent control of Al/poly-Si interfacial reactions. Using specialised aluminum pastes and optimised firing conditions, low contact resistivity of ∼0.1–0.3 mΩ·cm 2 and competitive contact recombination current densities are demonstrated on both n-type and p-type poly-Si. Interfacial characterisation reveals strongly polarity-dependent Al/poly-Si reactions, with restrained local interaction on n-type poly-Si but more pronounced etching and Al-p + formation on p-type poly-Si, providing insight into aluminum metallisation physics on passivated contacts. Device simulations based on experimentally extracted parameters indicate an efficiency potential approaching 26% for silver-free BC solar cells with local aluminum contacts. Efficiency roadmap analysis further defines contact selectivity targets (especially J 0,metal ) required to narrow the performance gap with state-of-the-art silver-metallised BC devices. These results establish screen-printed aluminum metallisation as a scalable pathway toward silver-free BC technology.