Tellurium

Tellurium is a brittle metalloid recovered almost entirely as a by-product during copper smelting, prized for its role in next-generation solar cells and thermoelectric coolers. Its supply is tightly constrained and divorced from deliberate mining; prices are volatile because demand from photovoltaics swings with renewable energy policy and silicon solar’s economics.

Why tellurium matters to clean energy

Tellurium occupies a cramped but crucial niche in the global energy transition. While the overwhelming majority of solar panels use silicon photovoltaics, thin-film solar cells—particularly cadmium telluride (CdTe) modules—capture a persistent 5–7% of the solar market and attract disproportionate investment because they are cheaper to manufacture, require less material per watt, and perform better in low-light and high-temperature conditions.

A single CdTe panel requires roughly 150 grams of tellurium per square metre. Solar firms like First Solar, the largest CdTe manufacturer, consume thousands of tonnes annually. At global solar panel installation rates now exceeding 200 gigawatts per year, even a modest shift toward thin-film technology can explode demand.

Thermoelectric coolers, which use the Peltier effect to transfer heat when current flows through dissimilar materials, rely on tellurium compounds for their efficiency. These devices are niche—used in scientific instruments, medical cooling, portable refrigeration—but are growing as heat-sensitive electronics (from 5G base stations to electric vehicle batteries) require precision temperature control.

The tension is stark: tellurium supply is almost wholly constrained by copper refining, which moves to the beat of industrial demand and copper price cycles, not solar energy policy. When copper mining slows, tellurium dries up regardless of solar panel orders. This mismatch creates recurring supply crunches and price spikes.

Recovery and bottlenecked supply

Tellurium is extracted from copper anode slimes—the residue left at the bottom of the electrolytic copper refining furnace. These slimes contain selenium, tellurium, gold, silver, and other precious elements. The slimes are roasted, leached, and then separated through a sequence of chemical steps. Tellurium recovery is economical only because it shares recovery infrastructure with more valuable elements like gold and silver; treating tellurium alone would be cost-prohibitive.

The world produces roughly 350–450 tonnes of tellurium annually, though exact figures are opaque because many producers treat it as a confidential by-product credit. Canada, Peru, Japan, and Russia are the primary recovery zones. However, there are no tellurium mines—every tonne is incidental to copper refining. This structural constraint is profound: even if solar demand spiked 50%, tellurium output could not surge until copper refining capacity expanded, a multi-year undertaking.

Strategic reserves are minimal. Tellurium cannot be easily stockpiled because it oxidizes and degrades; users prefer fresh supply. During the 2008–2009 solar boom, when CdTe manufacturers rushed to scale, tellurium prices spiked to $300+ per kilogram because supply could not keep pace with three-month lead times for refinery processing. The boom deflated when silicon solar costs plummeted, but the episode exposed how fragile supply truly is.

Cadmium telluride and the solar ecosystem

CdTe modules, pioneered by First Solar and now manufactured by competitors including Avanell (Sunpower subsidiary) and others, convert sunlight to electricity with an efficiency of 19–22% in commercial modules, competitive with multicrystalline silicon. The advantage lies in manufacturing: CdTe is deposited as a thin film in a sequence of vacuum or chemical deposition steps, requiring far less material than the silicon wafer stacks used in conventional panels. This translates to lower material costs and energy payback (the time required to generate as much energy as was consumed in manufacturing).

Cadmium, however, is toxic and heavily regulated. Environmental agencies, particularly in the EU, have scrutinised CdTe modules for decades. First Solar counters this with rigorous recycling: they collect and process used panels to recover cadmium and tellurium, both of which are valuable enough to refurbish. A closed-loop recycling facility can recover 95%+ of both metals, and tellurium reclaimed from recycled panels now supplies 10–15% of the CdTe market’s needs.

This recycling creates a secondary supply stream independent of copper refining. As CdTe penetration has grown, recycling has become material. A 25-year-old CdTe panel installed in 2000 is now yielding tellurium to be reused in 2026 modules. Over time, this loop could decouple tellurium demand from copper production cycles—a structural shift that would stabilize prices.

Silicon solar, however, remains the incumbent. Manufacturing margins for silicon have compressed relentlessly, pushing efficiency improvements and falling costs. CdTe’s advantage is narrowing, and some analysts worry that CdTe will remain a niche, preventing tellurium demand from growing substantially. Others counter that the diversity of technologies is healthy for resilience and that CdTe will hold its 5–7% market share indefinitely.

Optoelectronics and other applications

Beyond solar, tellurium compounds power infrared detectors, laser diodes, and high-speed electronics. Bismuth telluride is the most common thermoelectric material, used in coolers for scientific instruments and speciality refrigeration. Tellurium is also alloyed with metals like iron and copper to improve machinability and reduce brittleness, though these applications consume only tens of tonnes annually.

These uses are steady but small compared to CdTe demand. Even if optoelectronics doubled, the total would not exceed 100 tonnes per year—a fraction of solar’s draw.

Pricing, volatility, and futures risk

Tellurium is not traded on any major commodity exchange. Pricing is set bilaterally between producers and end-users, with published quotes from a handful of brokers. This opacity creates opportunities for information asymmetry: a user who knows copper refining throughput will fall can negotiate lower long-term contracts; a user caught unaware pays spot prices that can triple in weeks.

Historical prices have ranged from $50 per kilogram (2016) to $300+ per kilogram (2008, 2011). Recent range is $100–200 per kilogram, still highly volatile relative to established metals. The lack of a futures contract means there is no easy hedge, and no price discovery mechanism that functions across the globe.

A futures contract on a major exchange would solve this immediately, but trading volume is too low to attract exchange operators, and producers have little incentive to standardize when bilateral arrangements let them capture volatility premiums. The result is a prisoner’s dilemma: the market remains illiquid and opaque because it is small, and it remains small partly because volatility discourages long-term investment.

Regulatory and demand risks

Cadmium’s toxicity classification poses a latent regulatory risk. If the EU or other major jurisdictions ban cadmium entirely—even with exemptions for CdTe—the industry would face a jump-cut. First Solar and others have prepared arguments that closed-loop recycling renders CdTe safe, and that banning it would eliminate a competitive low-cost solar option. However, political risk is real.

On the demand side, continued silicon solar cost declines could squeeze CdTe into obsolescence. If silicon efficiency approaches 25% and costs fall further, and if silicon recycling becomes as rigorous as CdTe recycling, the case for CdTe weakens on every axis: cost, efficiency, environmental profile. Conversely, if silicon hits a hard ceiling at 25% efficiency and heat-dissipation limits, CdTe’s high-temperature tolerance becomes attractive.

The wildcard is perovskite solar, an emerging technology that is cheaper to manufacture than either silicon or CdTe but still in early commercialisation. Perovskite requires neither tellurium nor cadmium. If perovskite scales in the 2030s, tellurium demand from solar could collapse, leaving the small optoelectronics and thermoelectric markets as the sole demand drivers.

See also