The rise of cadmium telluride (CdTe) solar panels

In the world of renewable energy, solar panels have become a key player, with silicon-based panels dominating the market for decades. However, another type of solar panel technology is quietly making waves: cadmium telluride (CdTe) solar panels. Although not as well known, CdTe panels offer unique advantages that could soon challenge the monopoly of solar silicon. In this article, we will explore why CdTe panels could be the future of solar energy, how they work, and the challenges they face.

What are cadmium telluride (CdTe) solar panels?

CdTe solar panels are made of cadmium and tellurium, both of which are toxic in isolation, but safe when combined in a semiconductor. This combination results in a material that is highly effective at converting sunlight into electricity, making CdTe panels a strong contender in the solar industry.

Although silicon still dominates most of the market, CdTe technology is not new. In fact, CdTe panels are the second most common photovoltaic (PV) technology, used primarily in the U.S. market. These panels offer distinct advantages over traditional silicon panels, such as higher efficiency in specific situations and a thinner, more cost-effective design.

Key advantages of CdTe solar panels

1. Higher energy efficiency
2. One of the most attractive features of CdTe is its energy efficiency. The material has a bandgap of 1.5 electron volts (eV), which is ideal for solar energy absorption. While silicon has a bandgap of 1.1 eV, CdTe’s slightly higher value allows it to absorb high-energy photons more efficiently without overheating. This translates into better performance at higher temperatures, making CdTe panels particularly suitable for hot, sunny climates.

In addition, CdTe is a “direct bandgap” semiconductor, which means that it absorbs sunlight more efficiently than silicon. As a result, CdTe panels can be much thinner and still generate comparable power levels, reducing production costs and material usage.

1. Better thin-film technologyCdTe panels shine in the thin-film solar panel category, where they outperform silicon in efficiency. While traditional silicon panels see a drop in efficiency as they get thinner (sometimes as low as 6%), CdTe panels maintain their efficiency even as they shrink. This makes CdTe panels a fantastic choice for projects where weight and material costs are critical factors.
2. Durability and longevityCdTe panels are also known for their durability. First Solar, a leading manufacturer of CdTe panels, claims that its panels maintain 89% of their efficiency after 30 years. This is crucial for long-term solar installations where durability and low maintenance are key priorities.

Challenges facing CdTe solar panels

Despite these advantages, CdTe panels are not without their challenges. These challenges have limited their market share, which globally stands at only 4%.

Shortage of tellurium

One of the main obstacles facing CdTe technology is the shortage of tellurium, a key element in its production. Tellurium is rare, as common as platinum, and is mainly a by-product of copper mining. While this has not made CdTe panels prohibitively expensive, it does raise concerns about scalability, especially as demand for solar energy grows.

Toxicity and recycling concerns

Both cadmium and tellurium are toxic, making recycling and end-of-life management of CdTe panels a significant issue. Fortunately, companies such as First Solar have developed closed-loop recycling systems that recover more than 90% of the materials used in their panels. However, large-scale recycling remains a challenge, and the environmental impact of mass production of CdTe panels could limit their widespread adoption if not properly managed.

Copper doping and degradation

The efficiency of CdTe is often improved by doping with copper or arsenic. However, over time, copper can degrade the lattice structure of the material, reducing the efficiency of the panel. This problem has been addressed in part with a process called copper reduction, but remains a key area of research to ensure long-term stability.

Competing technologies: silicon and perovskites

While CdTe panels have clear advantages, they are not without competition. Silicon panels remain the gold standard, with a well-established production infrastructure and efficiencies between 20% and 24%. In addition, perovskite solar cells, although still in the research phase, offer potential efficiencies of 26.7%. However, perovskites are prone to degradation and are not yet commercially viable, leaving CdTe as a promising alternative in the short to medium term.

First Solar’s role and future prospects

First Solar, the leading manufacturer of CdTe panels, has played a crucial role in the advancement of CdTe technology. With commercial panel efficiencies of 19.3% and laboratory efficiencies reaching 23.1%, First Solar continues to push the boundaries of CdTe performance. The company seeks to reach 25% efficiency by 2025 and is working on innovations to further increase CdTe’s competitiveness.

First Solar is also addressing environmental concerns by reducing the carbon and water footprint of its panels, making CdTe panels some of the fastest in terms of energy payback time: the period required for panels to “pay for themselves” in energy savings.

The future of CdTe solar technology

Solar CdTe technology has the potential to disrupt the solar industry, particularly in large-scale solar farms and projects where material costs and durability are critical. Although it still takes a back seat to silicon, with ongoing research and improvements, CdTe could become a more prominent player, especially as companies such as Advanced Solar Power in China ramp up production.

The path forward for CdTe includes increasing efficiency, solving degradation issues and expanding recycling efforts. With a theoretical efficiency ceiling of 35.79%, there is still much untapped potential in CdTe technology. If these advances are realized, CdTe could challenge the dominance of silicon and become the technology of choice for specific applications.

Conclusion

Although silicon remains the dominant force in the solar panel industry, CdTe is rapidly emerging as a viable alternative, particularly for large-scale solar projects. Its durability, thin film technology and efficiency make it an attractive option. However, challenges such as tellurium shortages and toxicity concerns must be addressed before CdTe can surpass silicon on a broader scale.

In the meantime, as researchers continue to push the efficiency limits of CdTe and companies expand production, this “underrated indie band” of solar technology is poised to become a key player in the global shift to renewable energy.