Low-cost Cu-plated metallization on TCOs for SHJ Solar Cells - Optimization of PVD Contacting-layer

Our novel metallization approach for silicon heterojunction (SHJ) solar cells takes advantage of a PVD metal-stack covered with a structured self-passivated Al layer as mask for electroplating a Cu grid. This plating metallization route enables a very low cost of ownership (COO) for SHJ solar cell back-end processing for busbars interconnection. Encouraging efficiencies of 22.1% are reached with FF > 81% and R _s down to 0.39 Ω·cm ² on large area. A variation of the contact layer to ITO shows that of the investigated materials, TiW reached a sufficiently low contact resistivity down to 0.7 ± 0.3 mΩ·cm ² while for pure Ti it was too low to be measured (0.1 ± 0.3 mΩ-cm ² ). High busbar peel-off forces above 3 N/mm (Ti) are demonstrated.. Furthermore, a carefully adjusted etch-back procedure proves that AZO can be combined with our plated metallization to manufacture Ag- and In-free SHJ solar cells.