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The toxicity of cadmium telluride in the environment: what makes it so concerning?
Cadmium telluride (CdTe) is a stable crystalline compound formed from cadmium and tellurium. It is mainly used as a semiconductor material in cadmium telluride photovoltaic (PV) cells and has applications in infrared optical windows. CdTe is often interlayered with cadmium sulfide to form p-n junction solar cells. Due to its widespread use in solar technology, CdTe has raised concerns about its toxicity and environmental impact. This article will provide an in-depth look at the physicochemical properties, applications, and toxicity assessment of cadmium telluride.
Applications and requirements of CdTe
Cadmium telluride is widely used in thin-film solar cells and was estimated to account for approximately 8% of all installed solar cells in 2011. CdTe thin-film solar cells are one of the lowest-cost types, although installation cost comparisons depend on installation size and multiple other factors, and can vary dramatically from year to year.
In 2011, approximately 2 GWp of CdTe solar cells were produced globally, with the market dominated by First Solar.
In addition, CdTe can be alloyed with mercury to create a multifunctional infrared detection material HgCdTe, while alloying CdTe with a small amount of zinc forms an excellent solid-state X-ray and gamma ray detector CdZnTe. CdTe is also used as an optical material, in optical windows and lenses, and has been proven to provide good performance over a wide temperature range.
Physical and chemical properties of cadmium telluride
The physical properties of cadmium telluride include its low thermal expansion coefficient (5.9×10−6/K) and high melting point (up to 1041°C). CdTe is insoluble in water and has good stability, thanks to its high melting point and insolubility. It can be used as an optical material, especially in the infrared region.
The vapor pressure of CdTe under atmospheric conditions is zero, which makes it more stable in practical applications.
Toxicity assessment
While cadmium itself is a toxic substance, the toxic properties of CdTe are completely different from those of its constituent elements. CdTe shows low risk for acute inhalation, oral and aquatic toxicity. Its toxicity rating has been reduced for either contact with skin or ingestion. According to the European Chemicals Agency (ECHA), cadmium telluride is no longer classified as a hazardous substance.
As a 2003 National Institutes of Health document noted, CdTe has the potential to be widely used in photovoltaic energy production, and a thorough toxicological study of long-term exposure is urgently needed.
Despite this, the European Chemicals Agency still lists CdTe as a substance that is persistently toxic to aquatic life. This raises major concerns about the environmental and human health impacts of cadmium telluride. What everyone at CAB needs to realize is that the potential consequences of long-term use of such materials cannot be ignored.
Market and Future Outlook
Currently, the cost of cadmium and tellurium, the raw materials for manufacturing CdTe solar cells, accounts for only a small fraction of the cost of production. However, tellurium is a relatively rare element, found in only 1-5 ppm in the Earth's crust. According to predictions, with the improvement of material utilization and the development of recycling systems, by 2038, the CdTe photovoltaic industry is expected to completely rely on tellurium resources in recycled modules.
By 2050, CdTe photovoltaic recycling will add significant secondary resources, which will in turn support the continued growth of renewable energy.
Overall, the application and market prospects of cadmium telluride are full of potential, but its long-term toxic effects still require further study. Therefore, when we explore the wide range of applications of cadmium telluride, we should think about: How can we better balance the relationship between technological development and environmental protection while pursuing renewable energy?
