Solar traceability lets a buyer confirm where a module's materials were sourced

European procurement now turns on documentation, not assurance. Public tenders, large EPCs and corporate buyers with net-zero commitments have to record the origin and the sourcing conditions of what they install, and European supply chain due diligence and sustainability reporting rules require that record across environmental and social practices. A supplier's statement that its materials are responsibly sourced is not that record. The system that produces the record is traceability.

Most of a solar module's footprint is bought in, not made in final assembly. Scope 3 accounted for 90.4 percent of LONGi's total value chain footprint in 2025, and those same upstream stages hold the conflict-mineral and labour exposure that a supply chain audit examines first. A buyer scored on supply chain transparency has to follow a specific module back to the specific sources of its silicon and its metals, which a policy document cannot do.

Supply chain transparency in solar rests on traceability that an outside body can check, not on the manufacturer's word. LONGi's traceability system reached 100 percent coverage from raw materials in 2025 and connects each item's key raw-material data to third-party certificates.

Traceability begins by controlling which suppliers enter the chain

LONGi runs a staged admission process for its silicon-chain suppliers. A supplier signs a compliance-path commitment before it can be considered. Its compliance systems and production traceability records are then checked through on-site inspection and document tracing. Only a supplier that passes enters the traceability resource pool, after which tiered management applies and the results feed into performance reviews.

Inside the pool, every item is tracked to a single code. The Traceability Service System was upgraded to version 2.0 in 2025, assigning each item an SN code for one-item-one-code tracking and linking key raw-material data to the third-party certificates that stand behind it. The same year, the system reached the Tier 1 suppliers of the non-silicon primary materials used in modules, with further upstream extension planned.

The system follows the Solar Stewardship Initiative Supply Chain Traceability Standard and the SEIA 101 Standard, so a European buyer reading its output is reading against references the sector already uses. The Supplier Code of Conduct was updated in 2025 to align with the SSI ESG standard.

A traceability record counts because an outside body checks it, not the seller

The value of a traceability record is that someone other than the supplier stands behind it. LONGi's key polysilicon suppliers obtained the AA-rated full-chain traceability management system certification from TÜV Rheinland and passed the supply chain traceability audit of the IFC, part of the World Bank Group, in 2025. Its Chuzhou base became the first in the global PV industry to receive the Solar Stewardship Initiative ESG Gold certification, and its Jiaxing Phase I base received SSI ESG Silver.

The checks recur rather than settling a supplier once. In 2025 LONGi ran on-site ESG and traceability audits at 24 key suppliers and third-party ESG and traceability audits at 12 silicon-chain suppliers. Sedex recognised the programme with its 2025 Supply Chain Social Contribution Award.

Traceability is what answers a conflict-mineral or forced-labour question

The point where traceability earns its place is a due-diligence question a buyer cannot answer with a policy. LONGi reports a 100 percent due-diligence completion rate and a 100 percent commitment rate across its responsible-mineral scope for 2025, which covers tungsten, tin, tantalum, gold, cobalt, mica, copper, aluminium and silicon. It reports zero conflict minerals used and zero revenue from products that contain them.

Its tin-containing materials come from 12 suppliers drawing on 6 RMAP-certified Chinese smelters, none in conflict-affected or high-risk areas. The reporting sits on the OECD Due Diligence Guidance, the Responsible Minerals Assurance Process, the SSI standard and the Chinese Due Diligence Guidelines, so a buyer can map the output onto the reference its own auditor works from.

Without a traceable chain, the buyer inherits the risk the record would have removed

A supply chain ESG requirement is met with a record for a specific product, not with a statement of intent. When an auditor or a tender asks where a module's silicon came from and under what conditions it was produced, the answer is either a chain an outside body has already checked or an assurance that cannot be tested. A buyer who accepts the assurance keeps the audit exposure the missing record leaves in place, and meets it late, in a due-diligence review or a tender that scores supply chain transparency. The module that arrives with the checked chain is the one that clears the review.