Chem Explorers

Cadmium Telluride: A Powerful Material with Health Risks and Sustainability Concerns

Cadmium Telluride: The Material That Powers Solar Cells and More

Cadmium Telluride (CdTe) is a compound of cadmium and tellurium, characterized by high absorbance in the visible region and low absorbance in the infra-red region of the electromagnetic spectrum. The unique properties of CdTe have made this material valuable in various fields, including solar cell technology, infrared optics, radiation detection, and electro-optic modulators.

In this article, we will explore the preparation, properties, and applications of CdTe in detail.

Preparation and Properties

CdTe can be prepared by reacting cadmium and tellurium in stoichiometric proportions in a Vycor tube. The resulting black crystalline powder is almost insoluble in water and has a melting point of 1092C and a boiling point of 1090C.

The material has a high density of 6.2 g/cm3, a wide band gap of 1.44 eV, and a thermal conductivity of 6.2 W/mK. Its specific heat capacity is 0.41 J/gK, and the lattice constant is 6.482 .

The Young’s modulus is 52.6 GPa, the Poisson ratio is 0.40, and the refractive index is 2.6.

Applications of CdTe

Solar Cells

CdTe is one of the most promising materials for low-cost, efficient solar cells. In recent years, it has become a popular choice due to its abundance, high conversion efficiency, and low fabrication cost.

CdTe-based solar cells have an n-i-p structure, where ‘n’ is n-doped CdS (cadmium sulphide), ‘i’ is intrinsic CdTe, and ‘p’ is p-doped CdTe. CdTe solar cells have a high absorption coefficient at wavelengths around 500 nm, enabling efficient conversion of sunlight to electricity. With a band gap of 1.44 eV, CdTe solar cells can convert sunlight into electrical energy at a higher percentage than other common solar cell materials like silicon.

Infrared Detectors

CdTe is also a solid-state material capable of detecting infrared radiation. When a photon collides with the CdTe semiconductor, it produces a signal indicating the presence of radiation.

CdTe is alloyed with mercury, which decreases the fraction of free holes in the material and leads to better detection capabilities. CdTe-based infrared detectors are commonly used in gamma and X-ray detection applications due to their high sensitivity and fast response time.

Optical Windows and Lenses

CdTe has a limited use as an infrared optical window due to its small bandgap and high index of refraction. The material is normally used for wavelengths greater than 2.5 m, and is typically coated with a thin, transparent protective layer to prevent oxidation.

CdTe lenses are occasionally used for infrared imaging applications, but generally are not the best choice for this application. Irtran-6, another infrared-transmitting material, is often used instead of CdTe.

Electro-Optic Modulators

CdTe’s electro-optic properties have led to its use in electro-optic modulators. The linear electro-optic effect is used in this application, with an applied electric field changing the refractive index of CdTe. CdTe provides the greatest electro-optic coefficient when compared to other available materials.

An applied voltage to a CdTe device causes a change in the measured phase of light passing through the material, which enables the modulation of an optical signal.

Radiation Detectors

CdTe is doped with chlorine to produce a material that can be used in radiation detection, specifically alpha and beta particles, X-rays, and gamma rays. This doped material is often used for nuclear spectroscopy applications.

Chlorine doping makes it possible for CdTe to detect high-energy radiation, such as X-rays and gamma rays, by creating electron-hole pairs in the semiconductor material. These pairs can be detected and measured.

Conclusion

CdTe is a versatile semiconductor material that has numerous applications in solar cells, infrared optics, radiation detection, and electro-optic modulators. Its unique properties make it an attractive material for use in various applications.

As technology continues to advance, it is possible that additional CdTe applications will be discovered. Advantages and Disadvantages of Cadmium Telluride: A Comprehensive Look

Cadmium Telluride (CdTe) is a semiconductor material that has been widely considered in the field of solar technology, as well as radiation detection and electro-optic modulation due to its properties.

Despite its usefulness and abundance, there are also some disadvantages associated with this material. In this article, we will take a look at the advantages and disadvantages of CdTe in detail.

Advantages of CdTe

1. Simple manufacturing process: CdTe solar cells are much simpler to produce than conventional silicon-based cells.

Unlike silicon cells, CdTe cells can be grown on a glass substrate, eliminating the need for high-temperature processing, which also eliminates the risk of cell distortion and cracking. 2.

Ideal wavelength absorption: CdTe cells have an ideal wavelength absorption range of 800 to 900 nm, i.e., almost coming from the sunlight. Photons with energy levels equivalent to 1.45 eV (850 nm wavelength) are fully absorbed, thanks to the material’s bandgap of 1.4 eV.

3. Abundance of Cadmium: Cadmium is a common element present in the earths crust.

It is primarily a byproduct of zinc refining, with the recycling of cadmium contributing to its abundance.

Disadvantages of CdTe

1. Low efficiency: Although CdTe solar cells are cheaper to produce, they have lower efficiency when compared to traditional silicon-based cells.

CdTe cells have an efficiency range of 9% to 11%, whereas silicon cells have efficiencies of up to 25%. 2.

Tellurium Scarcity: Tellurium is crucial to the production of CdTe solar cells, with the material offering a critical role in the production process. The scarcity of this mineral can increase the cost of production and limit the scaling up of CdTe solar panel production.

3. Toxicity: CdTe cells contain cadmium, which is a toxic heavy metal.

During the production process, it is crucial to put in place measures to ensure that emissions of the toxic compound are kept to a minimum to protect the workers. CdTe cells require proper handling to ensure that they do not pose a risk to the environment and public health.

Safety Measures for Cadmium Telluride

Toxicity and Health Effects

Cadmium is a poisonous metal and has proven to cause various health-related problems, including cancer. It is crucial to minimize exposure to cadmium by keeping various safety measures in place.

The production process of CdTe requires that workers wear suitable protective gear like gloves and masks to prevent inhalation or skin contact. Additionally, the CdTe films can re-crystallize and cause damage to the respiratory system.

CdTe also requires handling once the material is formed as a film to prevent its reactivity with oxygen, which produces cadmium oxide that can be harmful.

First Aid Procedures

In case there is exposure to cadmium or CdTe, immediate medical intervention is necessary to prevent any further health complications. Eye irritation requires that the eyes are flushed with clean water for 20 minutes.

Skin contact requires that the affected area is washed immediately with soap and water. Inhalation symptoms include coughing, dizziness, or nausea, which requires urgent medical attention.

Ingestion may cause abdominal pain, muscle cramps, nausea, vomiting, and diarrhea that may also necessitate hospitalization.

Personal Safety Measures

CdTe handling requires the workers to have Personal Protective Equipment (PPE) that includes gloves, respirators, safety goggles, dust masks, and coveralls, among others. The National Institute for Occupational Safety and Health (NIOSH) provides recommendations for appropriate equipment, and it is crucial that workers follow these guidelines.

A proper storage instruction is also necessary, with the material stored in a non-reactive container to minimize the risk of decomposition, which can produce toxic fumes.

Fire Fighting Measures

In case of fire, CdTe is known to decompose and emit toxic fumes, which require the use of protective gear. It is crucial that firefighters are aware of CdTe’s toxic properties and take the necessary precautions.

Firefighters must use self-contained breathing equipment when fighting a CdTe fire.

Availability

CdTes main component, tellurium, is relatively scarce despite being readily available in nature. According to the U.S. Geological Survey (USGS), the global tellurium reserves may be insufficient to meet the increasing demand for CdTe solar cells in the future.

This shortcoming may contribute to the rise of solar cell costs or even make the cells unavailable, which may hamper the growth of the solar cell industry in the future.

Conclusion

Cadmium Telluride is an important material with numerous potential applications, including solar power production and radiation detection. However, it is essential to put measures in place to decrease the toxicity effects of tellurium and cadmium on workers, the environment and potential customers.

Adequate safety measures should, therefore, be followed to minimize the exposure of cadmium and tellurium to humans. It is also crucial that future research prioritizes ways to lessen the impact of CdTe on human and environmental health in the material’s lifespan.

In this article, we have explored the preparation, properties, and applications of cadmium telluride in detail. The material has great potential for use in fields such as solar cell technology, infrared optics, radiation detection, and electro-optic modulation.

However, it is essential to consider the potential health risks associated with exposure to cadmium and tellurium and take measures to minimize these risks. The scarcity of tellurium may also present a challenge for the production of CdTe cells in the future.

By understanding these advantages and disadvantages and prioritizing safety measures, we can harness the potential of CdTe while minimizing any negative impacts. FAQs:

1.

What is cadmium telluride used for? Cadmium Telluride is a versatile semiconductor material used in solar cells, infrared optics, radiation detection, and electro-optic modulators.

2. Is cadmium telluride toxic?

Yes, cadmium is a toxic heavy metal that poses health risks to workers and the environment if exposed. 3.

Is cadmium telluride efficient for solar panels? CdTe has a lower efficiency rate compared to traditional silicon-based solar cells but is cheaper to produce.

4. What are the safety measures for handling CdTe?

Proper personal protective gear, storage, handling in a non-reactive container, and suitable waste disposal. 5.

Is tellurium scarce? Yes, tellurium is scarce and may become a challenge for the scaling up of CdTe solar panel production in the future.

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