Cadmium Telluride, 1306-25-8

Cadmium Telluride, 1306-25-8

CADMIUM TELLURIDE (CdTe)

1. PRODUCT DEFINITION AND CHEMICAL IDENTITY

Note: Cadmium telluride is a II-VI direct bandgap compound semiconductor with exceptional photovoltaic properties. Its ideal bandgap of approximately 1.45 eV is perfectly matched to the solar spectrum, making it about 100 times more effective at absorbing sunlight than silicon (requiring only ~1 µm thickness versus >100 µm for silicon). This property has made it the dominant material for thin-film solar cells. It is also used in infrared optical windows and electro-optic modulators. Due to the toxicity of cadmium, safe handling and disposal require special attention.

2. PHYSICAL AND CHEMICAL PROPERTIES

3. FUNCTIONAL PROPERTIES AND MODE OF ACTION

• Photovoltaic Conversion (Solar Cells – Most Important Use): CdTe's direct bandgap of ~1.45 eV provides an optimum match to the solar spectrum. It is about 100 times more effective at absorbing sunlight than silicon, meaning a CdTe film just a few micrometers thick can absorb over 90% of incident light. Commercial CdTe modules offer low production costs and high efficiency.

• Infrared Optical Window: CdTe exhibits excellent transparency across a wide infrared range (from about 0.9 µm to 16 µm). This makes it an ideal material for IR windows and lenses in CO₂ laser systems, thermal imaging, and night vision devices.

• Electro-Optic Modulation: It is a crystal that exhibits the Pockels effect, changing its refractive index under an applied electric field. This property is exploited for modulating laser light and in optical communication applications.

• X-Ray and Gamma-Ray Detectors: Due to its high atomic number and density, it absorbs X-ray and gamma radiation very efficiently, making it useful in detectors for medical imaging and security screening.

4. COMMERCIAL FORMS AND TYPES

5. SECTORAL APPLICATIONS AND USAGE AREAS

6. ALTERNATIVE NAMES AND SYNONYMS

7. ALTERNATIVES AND COMPARISON

8. SAFETY, STORAGE, AND REGULATORY INFORMATION

• GHS Classification (CLP Regulation):

  • Signal Word: Danger

  • Hazard Statements: H302+H312+H332 (Harmful if swallowed, in contact with skin, or inhaled), H350 (May cause cancer – as a cadmium compound), H361 (Suspected of damaging the unborn child), H373 (May cause damage to organs through prolonged or repeated exposure), H410 (Very toxic to aquatic life with long lasting effects).

  • Precautionary Statements: P201, P202, P260, P264, P270, P273, P280, P301+P312, P302+P352, P304+P340, P308+P313, P312, P314, P330, P391, P405, P501.

• Cadmium Toxicity: Cadmium compounds are carcinogenic, mutagenic, and toxic for reproduction. They have serious chronic effects on the kidneys, bones, and respiratory system. Exposure to dust and fumes must be strictly avoided when working with CdTe.

• Environmental Impact: Cadmium and its compounds are very toxic to aquatic life and bioaccumulate in the food chain. Waste management must strictly comply with legal regulations.

• RoHS Directive: Cadmium is restricted under the RoHS (Restriction of Hazardous Substances) directive; however, exemptions exist for solar panels and certain optical applications.

• Storage:

  • Store in a locked, dry, and well-ventilated area in tightly sealed, clearly labelled containers.

  • Keep away from acids, oxidizing agents, and foodstuffs.

  • In case of spills, collect mechanically without generating dust and dispose of as hazardous waste.

• Personal Protective Equipment (PPE): Use a full-face respirator (P3 particulate filter), nitrile or neoprene gloves, safety goggles, and a lab coat. Adequate ventilation and regular air monitoring in the work area are mandatory.

9. FREQUENTLY ASKED QUESTIONS

Q1: Are CdTe solar panels safe?
Yes, they are safe during use. CdTe is a stable compound tightly encapsulated between two sheets of glass and does not release into the environment during normal operation. The toxicity risk is primarily associated with the manufacturing and disposal stages. Major manufacturers implement closed-loop recycling programs.

Q2: Why is CdTe a better solar cell material than silicon?
CdTe is a direct bandgap semiconductor, meaning it is far more efficient at absorbing sunlight than silicon (an indirect bandgap semiconductor). A CdTe film just ~1 µm thick can absorb the same amount of light as a >100 µm thick silicon wafer. This translates to significantly lower material and manufacturing costs.

Q3: What is the advantage of CdTe in IR optics?
It offers excellent transparency across a wide infrared range (up to 16 µm) and a high refractive index. This makes it an excellent window and lens material, particularly for CO₂ lasers operating at 10.6 µm.

10. QUICK REFERENCE TABLE