Process challenges of high-performance silicon heterojunction solar cells with copper electrodes

Substitution of expensive silver paste becomes essential for mass production of silicon heterojunction (SHJ) solar cell, which calls for high efficiency and low-cost metallization techniques. Copper metallization together with multi-busbar cell interconnection is considered as effective way to low shading loss and electrode ohmic loss. While, the electrode adhesion and parasitic plating are the key process challenges limiting the copper metallization of SHJ solar cells. In this research, the copper plated SHJ solar cells with high electrode aspect ratio and an efficiency of 23.35% have been achieved on M2 wafers. The SEM images show the holes in the plated layers will deteriorate the adhesion between plated copper and seed-layer. The glass/back sheet structure (GBS) modules have been laminated to evaluate the influence of parasitic plating on damp-heat (DH) performance. The degradation in output power (Pmax) is up to 4.90%, which is primarily due to a decreased open-circuit voltage (Voc) and fill factor (FF). It can be ascribed to the deteriorated surface recombination and interconnection. Although the parasitic plating on the wafer edge has ignorable influence on damp heat test after etch-back process, it is still necessary to protect the cell edge to avoid parasitic plating. The research evaluates the process challenges of copper metallization of SHJ solar cells, which offers a refer for achieving high reliability and low levelized cost of energy (LCOE) of photovoltaic power generation.