Electroplated nickel/tin solder pads for rear metallization of solar cells

In this study, we report on the feasibility of formation of nickel/tin solder pads and bus bars directly electroplated onto the aluminum screen-printed rear metallization layer of silicon-based solar cells. A localized wet processing technique via dynamic liquid drop/meniscus is used to perform the electrodeposition procedure. Excellent mechanical and electrical parameters of electroplated contacts are measured, thus proving the reliability of the proposed approach suitable for industrial application. Adhesion of electroplated nickel/tin solder pads is ensured through a two-step electrochemical pretreatment procedure, resulting in mean peel force values ranging from 2.5 to 3.8 N/mm. Electroplating of solder pads directly onto the screen-printed aluminum layer allows us to obtain a full homogeneous back surface field on the solar cell, resulting in an efficiency gain in 0.31-0.48%abs range. Furthermore, the proposed method completely removes the need for silver in the rear-side metallization layer of silicon-based solar cells.