China’s SPIC offering copper-based heterojunction solar modules

The Chinese module maker is preparing to bring to the market 25.97%-efficient heterojunction solar cells based on copper metallization. The new products are based on ultra-narrow 9-micron busbars, vacuum-deposited copper interconnects and proprietary interface engineering.

Last week, State Power Investment Corporation (SPIC) broke ground on a 10 GW high-efficiency heterojunction (HJT) solar cell and module manufacturing project in Suining, Sichuan province.

The factory will be owned and operated by the company's unit SPIC New Energy, which developed a proprietary copper busbar heterojunction (C-HJT) cell technology that replaces silver with copper in the metallization process. This breakthrough could significantly cut key manufacturing process costs compared with conventional silver-based processes, the company claims.

Chief scientist Wang Wei explained to China state media that the technology integrates three innovations: ultra-narrow 9-micron busbars measuring a third the width of silver lines, vacuum-deposited copper interconnects, and proprietary interface engineering.

Lab tests showed the proposed solar cell configuration can achieve a 25.97% power conversion efficiency, with modules hitting 710 W output.

“By solving copper's adhesion challenges through surface treatment, we've greatly increased pull-off strength which is critical for durable rooftop and utility-scale installations,” Wang said. The process reportedly maintains conductivity even with microcracks, addressing a key industry reliability concern.

SPIC's vertical integration strategy combines in-house R&D with equipment partnerships. Its 300 MW pilot line in Wenzhou has already deployed China's first fully domestic copper busbar production tools, with a 600 MW expansion under development. Though pandemic-era supply chains delayed the 5 GW Zhejiang factory, 600 MW became operational last June ahead of full commissioning this year.

The Sichuan expansion positions SPIC to leverage its 30 GW annual renewable energy deployments as a captive buyer.

With silver accounting for around 10% of solar panel costs, SPIC's copper shift comes as manufacturers scramble for alternatives amid volatile precious metal markets.