U.S. Scientists Build Copper-Contacted TOPCon Solar Cell with 24.3% Efficiency

Why It Matters

Replacing expensive silver with copper cuts material costs while preserving high efficiency, accelerating the economic case for large‑scale TOPCon deployment. The plug‑and‑play nature means manufacturers can adopt the method without major capital investment.

Key Takeaways

• Copper paste replaces costly silver in TOPCon cells
• LECO laser treatment cuts contact resistivity to ~10 mΩ·cm²
• Optimized firing at 530 °C yields 24.3% efficiency
• Cu‑contacted cells show 1000‑hour thermal stability at 200 °C
• Process uses existing PV line equipment, enabling plug‑and‑play adoption

Pulse Analysis

The TOPCon (Tunnel Oxide Passivated Contact) architecture has become a cornerstone of high‑efficiency silicon photovoltaics, but its commercial rollout has been hampered by the high price of silver metallization. By introducing a screen‑printable copper paste that can be fire‑through printed on the rear side, researchers have opened a cost‑effective pathway that retains the low‑loss characteristics essential for TOPCon cells. Copper’s intrinsic conductivity and the ability to form a thin oxide barrier around particles mitigate diffusion risks, making it a viable substitute for silver in mass production.

A critical enabler of this breakthrough is the Laser‑Enhanced Contact Optimization (LECO) technique. Applying a high‑intensity laser pulse while reverse‑biasing the cell dramatically lowers the metal‑semiconductor contact resistivity—from roughly 300 mΩ·cm² down to about 10 mΩ·cm²—without damaging the delicate tunnel‑oxide layer. Coupled with a carefully calibrated firing window of 530 °C to 535 °C, the process yields a 24.3% cell efficiency, essentially matching silver‑contacted benchmarks. The researchers also demonstrated that copper‑contacted cells maintain open‑circuit voltage and fill factor after 1,000 hours at 200 °C, underscoring the reliability needed for field deployment.

From a market perspective, the ability to swap silver paste for copper using existing screen‑printing and firing equipment removes a major barrier to scaling TOPCon technology. Material cost savings could be substantial, given that silver accounts for a significant portion of module bill‑of‑materials. Moreover, the plug‑and‑play nature of the process means manufacturers can integrate the copper approach with minimal line re‑tooling, accelerating time‑to‑market. As the PV industry seeks to lower Levelized Cost of Energy (LCOE) while pushing efficiencies above 24%, this copper‑based TOPCon solution positions itself as a pragmatic, high‑performance alternative that could reshape the economics of next‑generation solar modules.