Advanced front side metallization for crystalline silicon solar cells based on a fully plated contact
Nickel-Silicon contact systems have been studied intensively on shallow industrial emitters, with special focus on the contact formation step. Two different means of antireflexion-coating (ARC) ablation, dry laser ablation and inkjet-masking and etching have been used. Nickel layers have been applied by electroless and lightinduced plating (LIP) processes, and have been reinforced with LIP silver or copper. The plating process and the thermal silicide formation step have been varied for the electroless deposition process, making a statistical evaluation of the results. The nickel layer deposited by LIP has been found to form a good contact to silicon easier than the electroless nickel. This is contrary to earlier findings, and attributed to the use of a new electrolyte. Longer nickel plating durations have led to better results for subsequent silver plating. The best solar cells (Cz, 5x5 cm²) created reach efficiencies above 17%. The adhesion has generally been found to be higher for laser-ablated cells. The impact of the nickel contact formation on the junction has been studied by measuring the pseudo fill-factor (pFF). For relatively mild thermal steps, moderate losses in pFF have been found, yielding the best results.