Primary and Secondary Material Flows for the Future Global Deployment of Silicon-based Photovoltaic Systems

Abstract

The expected rapid expansion of global photovoltaic (PV) capacity will substantially increase demand for the raw materials required to manufacture and deploy solar PV systems. Since silicon-based PV currently accounts for approximately 98% of global PV production, this study focuses on silicon-based technologies. Several materials used in these systems are considered critical raw materials because of their economic importance and potential supply risks. At large deployment scales, PV could account for a significant share of global production of materials such as silicon, silver and copper, potentially creating constraints on future PV expansion.

To assess these challenges, the study develops a dynamic material flow analysis (dMFA) model to estimate future raw material demand, secondary material supply and in-use material stocks for global silicon-based PV systems. Deployment scenarios range from 29 TWp to 75 TWp of installed capacity by 2050. The model considers expected changes in PV technologies, including PERC, TOPCon, silicon heterojunction (SHJ), interdigitated back contact (IBC) and perovskite-silicon tandem technologies. It also incorporates reductions in material intensity resulting from improved manufacturing processes, technological development, material substitution and the phase-out of certain materials. Nine key elements are analysed: aluminum, copper, indium, lead, silicon, silver, gold, tin and zinc.

The results indicate that copper could become the most significant potential material bottleneck for the future PV sector. Between 2025 and 2050, cumulative copper demand is projected to reach 145–280 million metric tons, mainly driven by cables and inverters. Annual copper demand could peak in the mid-2040s at 7–15 million metric tons, equivalent to approximately 30–65% of current global copper mine production. Aluminum demand is even larger in absolute terms, ranging from 510 to 1,100 million metric tons cumulatively, with mounting structures representing the largest share. Silicon demand is estimated at 60–120 million metric tons, while more than 20% of the silicon input may be lost during wafer slicing.

Cumulative silver demand is projected to reach 100,000–200,000 metric tons and depends strongly on future copper metallization and reductions in silver paste use. Indium demand could reach 60,000–160,000 metric tons and is projected to exceed current global reserve and resource estimates by the mid-2040s. This highlights the importance of reducing or replacing indium in transparent conductive oxide layers. Tin demand is estimated at approximately 1–3 million metric tons.

Recycling can partially reduce primary material requirements, but materials from decommissioned PV systems are expected to represent only 15–20% of total material demand between 2025 and 2050. This is mainly due to the long lifetime of PV systems and limitations in recovering materials at sufficient purity. Silver is an exception, with future PV waste potentially supplying 30–45% of cumulative demand over the study period.

The resource impact assessment identifies gold, mainly used in inverters, as the largest contributor to resource depletion, followed by copper and silver. Indium is the dominant contributor to resource criticality because of limited reserves and concentrated refining capacity. Even hypothetical 100% closed-loop recycling would only partially reduce these impacts.

Overall, the study demonstrates that material availability could become an important constraint on large-scale PV deployment. Improving material efficiency, developing substitutes—particularly for copper and indium—and increasing recycling should therefore complement policies supporting domestic PV manufacturing and processing.