Corrosion resistance improvement of transparent conductive oxide films to the acidic etching during the electroplating preparation of copper electrodes on silicon heterojunction solar cells

Replacing silver with copper for the electrodes is a potential path to reduce the cost of silicon heterojunction (SHJ) solar cells. During the usually used electroplating process for the copper electrode preparation, an acidic etching solution is required for the removal of the excessive copper seed layer on the transparent conductive oxide (TCO) layers after the plating completion. Thus, it becomes necessary to reduce the impact of the acidic etching solution on the TCO films. Here, the resistance to the acidic etching of different In2O3-based TCO films with different doping concentration were compared. The results showed that highly Sn doped In2O3-based TCO (ITO) film exhibited better resistance to the acidic etching. Additionally, it was found that annealing treatment before the electroplating can increase the crystallinity of ITO, enhancing its resistance to the acidic corrosion, and thereby improving the conversion efficiency of SHJ solar cells. Comparing to the solar cell with the as-deposited ITO films, the annealing treated solar cell could obtain a relative conversion efficiency increase of 1.33 %. •The optical-electrical properties of In2O3-based TCO films are degraded under exposure to sulfuric acid solutions.•Highly Sn doped In2O3-based TCO (ITO) film exhibited better resistance to the acidic etching.•Annealing ITO films before copper electroplating enhances crystallinity, reduces corrosion, and optimizes the process.•The annealed solar cell achieved a 1.33 % increase in conversion efficiency compared to the one with as-deposited ITOs.