Longi Swaps Silver for Copper, Cutting Solar Costs

• Longi dumps costly silver for base metals, kicking off mass production in Q2 as rivals follow. Expect cheaper modules, reliability questions—and a BNEF-forecast decline in solar’s silver demand.

Longi Green Energy will begin substituting base metals for silver in its solar cells, with mass production starting in Q2, to cut module costs amid overcapacity and fierce competition. Silver prices, which tripled last year on safe-haven demand and tight supply, pushed silver’s share of per-watt module costs to 17% in October; prices topped $84/oz late last month.

Peers are following: Jinko plans large-scale copper-based panels this year, and Aiko has launched silver-free cells with 6.5 GW initial capacity. Longi’s back-contact cells ease substitution, but reliability and assembly costs remain hurdles, especially for TOPCon. BNEF sees solar’s silver use falling 7% in 2025 despite 15% growth in installations.

What technical and supply-chain risks accompany copper-based solar cell metallization shift?

• Copper diffusion into silicon causing junction shunts; need robust barrier/seed stacks (e.g., Ni, Co), adding complexity and failure points.
  
• Higher contact resistivity and adhesion challenges versus Ag; fine-line formation without widening fingers can raise series resistance and lower efficiency.
  
• Corrosion, oxidation, and electromigration risks under damp-heat, salt-mist, and thermal cycling; long-term reliability data still limited.
  
• Solderability and interconnect compatibility shifts (ribbons, multi-busbar/wire); altered thermal profiles can crack cells or delaminate contacts.
  
• Process overhauls from screen-printed Ag to plating/CLL/LDSE flows; capex for plating lines, lasers, chem-handling, and inline metrology.
  
• Yield loss risks from voids, over/under-plating, mask misalignment, and wafer breakage in wet benches; tighter bath control and cleanliness needed.
  
• Barrier metal supply dependence (Ni/Co) introduces new critical-material exposures, ESG concerns, and price volatility beyond copper itself.
  
• Chemicals and additives (complexing agents, brighteners) require stable supply, proprietary recipes, and strict waste-treatment compliance.
  
• Increased water and energy use for plating and rinsing; environmental permits and effluent limits may constrain siting and ramp speed.
  
• Equipment vendor bottlenecks for high-throughput plating, drying, and inspection; lead times can delay mass production.
  
• Integration challenges differ by cell tech (TOPCon, HJT, back-contact); some stacks more sensitive to Cu contamination and thermal budgets.
  
• Encapsulant and backsheet compatibility with Cu; potential acceleration of PID/corrosion if packaging isn’t tuned.
  
• Field-certification cycles (IEC, UL) need requalification; bankability and warranties hinge on extended reliability datasets.
  
• IP/licensing around Cu metallization and barrier stacks can add cost or restrict process windows.
  
• Recycling and end-of-life processes must adapt; current Ag recovery streams don’t translate directly to Cu/barrier mixes.
  
• Workforce safety and fire risk managing acids, cyanide-free chemistries, and hydrogen in certain metallization flows.
  
• Geographic regulatory risks (REACH, wastewater discharge rules) can fragment processes and supply chains across regions.
  
• Transition risk for paste suppliers and existing SMT lines; interim hybrid Ag/Cu flows may add complexity rather than reduce it quickly.
  
• Throughput matching across steps (texturing, diffusion, plating, firing/anneal) to avoid new bottlenecks.
• Market perception and financing risk if insurers and lenders discount Cu-based modules until multi-year field data accumulates.