Copper electroplating is an electrochemical process that deposits a thin metal, alloy, or composite coating onto a conductive substrate. In the photovoltaic sector, copper electroplating is an advanced technology designed to fully replace costly silver with low-cost copper for solar cell electrodes. Beyond significantly reducing manufacturing costs, the technology also enhances photoelectric conversion efficiency and is considered a key pathway toward achieving full “silver-free” solar cells.

Basic Principle

Copper electroplating forms high-conductivity copper grid electrodes by reducing copper ions into copper atoms on a conductive solar cell substrate through electrochemical reactions in an electrolyte. This process eliminates dependence on silver paste entirely.

Detailed Process Flow

A complete copper electroplating line typically includes four main stages:

1. Seed Layer Deposition
A very thin metal seed layer (e.g., ~100 nm) is deposited onto the transparent conductive oxide (TCO) of the solar cell. This seed layer improves adhesion for the subsequent copper grid.

2. Patterning
This is the key step for defining precise electrode geometries. A photoresist layer is applied to the seed layer, and techniques such as laser direct imaging (LDI) are used for exposure and development. Electroplating occurs only in the patterned grid areas.

3. Electroplating Metallization
The patterned solar cell serves as the cathode inside the electroplating equipment. Copper ions deposit onto the exposed seed layer to form copper gridlines. Current equipment solutions include vertical electroplating and horizontal electroplating systems.

4. Post-Treatment
After electroplating, the photoresist is removed and the non-grid seed layer is etched away, leaving clean and robust copper electrodes.

Technical Advantages of Copper Electroplating

Copper electroplating replaces silver paste entirely for grid electrodes and offers low cost, high conductivity, and high efficiency. Its advantages vary across mainstream solar cell technologies:

1. HJT + Copper Electroplating: Cost Reduction and Efficiency Boost

Early heterojunction (HJT) cells consumed large amounts of silver paste, making copper electroplating attractive for cost reduction. Today, with copper-plated silver widely adopted, electroplating’s main role for HJT is to further enhance conversion efficiency.

2. TOPCon + Copper Electroplating: Improving Voc

Copper electroplating helps TOPCon cells achieve low contact resistance and improved open-circuit voltage (Voc).
Dual-sided TOPCon structures using Ni/Cu/Ag metallization are realized through laser contact opening (LCO) combined with inline Ni/Cu/Ag electroplating.

Advantages of LCO + Ni/Cu/Ag include:

·         Low contact resistance on the n-type TOPCon layer and lightly boron-doped emitter

·         Lower contact recombination

·         Improved Voc due to the boron emitter

·         Narrow contact widths (<25 μm) with low line resistivity

3. Back-Contact (BC) Cells + Copper Electroplating: Cost and Process Matching

Compared with silver-paste screen printing, copper electroplating offers a 0.3%–0.5% efficiency boost.
For BC cells—where processes are complex and equipment, labor, and material costs are high—copper electroplating shows strong long-term potential in cost and process alignment.

Challenges and Outlook

Despite its advantages, copper electroplating still faces three major hurdles:

1.    Environmental Challenges:
The process generates heavy-metal effluent, nitrogen-containing waste liquids, and dry-film waste, which complicate environmental assessments and increase operating costs. With tightening environmental regulations in China, these issues have become key barriers to large-scale adoption.

2.    Throughput Limitations:
Horizontal electroplating currently offers lower output efficiency. Given the massive production scale of the solar industry, this results in significantly higher equipment investment per GW of capacity.

3.    Higher Process Complexity:
Compared with traditional screen printing, copper electroplating involves more complex steps and tighter equipment precision requirements, increasing process costs and yield-control difficulty.

Whether copper electroplating can achieve mass-production adoption within the next two years remains to be seen.

Source：SOHU