Enhanced adhesion strength of copper metallization on silicon heterojunction solar cell due to improved electrochemical reduction uniformity of ITO

Copper electroplating is an ideal technique for the metallization of highly efficient silicon heterojunction (SHJ) solar cells due to the unique advantage in the low cost, strong adhesion, and low contact resistance. Achieving these characteristics depends strongly on the seed layer before Cu electroplating. This work reports a potential economical and effective route for electrochemically reducing ITO to assist electroplating of Ni seed layer and increase the adhesion of the metallization grids. Good wettability of electrolyte solution to ITO and the low temperature account for the reduction uniformity. A uniform In,Sn/SnO mixed metal layer is formed on ITO surface after electrochemical reduction. With the assistance of the uniform reduction the adhesion strength of the metallization grid reaches to 9.9 N mm⁻1. Although it is conducted on a small-size ITO-coating Si plate, the present plating is convenient and low-cost for the metallization, which is expected to be suitable for the large-scale commercialization of SHJ solar cells.