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Cadmium telluride
Image:Cadmium telluride.jpg
Systematic name	Cadmium telluride
Other names	xxx, xxx
Molecular formula	XxXxXx
Molar mass	xx.xx g/mol
Density	x.xxx g/cm3
Solubility (water)	x.xx g/l
Melting point	xx.x °C
Boiling point	xx.x °C
CAS number	[xx-xx-xx]
Disclaimer and references

Cadmium telluride (CdTe) is a crystalline compound formed from cadmium and tellurium with a zinc blende (cubic) crystal structure (space group F43m). In the bulk crystalline form it is a direct bandgap semiconductor. The CAS registry number is [1306-25-8] [1].CdTe is also a strong Thin Film Solar Cell material. It is usually sandwich with CdS to form a pn junction photovoltaic solar cell. However the mechanism of its operation has been under review in the recent years. A group of reserchers based in the United Kingdom led by Prof. I.M. Dharmadasa proposed a New theoretical model for CdTe to explain the mechanism, challenging the theory that has been considered by the research world over 20 odd years.

Contents 1 Applications 2 Physical properties 3 Electronic properties 3.1 Thermal Properties 3.2 Optical Properties 4 Chemical properties 5 Toxicity 6 See also 6.1 Related materials 7 References 8 External links

[edit] Applications

CdTe is a useful material for solar cells (photovoltaics). It is cheaper than silicon, especially in thin-film solar cell technology, but not as efficient. CdTe can be alloyed with mercury to make a versatile infrared detector material (HgCdTe). CdTe alloyed with a small amount of zinc makes an excellent solid-state x-ray and gamma ray detector (CdZnTe).

CdTe is used as an infrared optical material for optical windows and lenses. In this application it is sometimes referred to by the trademarked name Irtran-6.

[edit] Physical properties

• Molecular weight: 240.02
• Density: 5850 kg/m³.
• Lattice constant: 0.648 nm at 300K
• Young's modulus: 52 GPa
• Poisson ratio: 0.41

[edit] Electronic properties

• The direct band gap is 1.56 eV at 300 K.
• Electron effective mass 0.11 m_e
• Hole effective mass 0.4 m_e

[edit] Thermal Properties

• Melting Point: 1314 K
• Thermal conductivity: 6.2 W.m^-1.K^-1 at 293 K
• Specific heat capacity: 210 J.kg^-1.K^-1 at 293 K
• Thermal expansion coefficient: 5.9x10^-6 K^-1 at 293 K

[edit] Optical Properties

CdTe is transparent from close to its band gap energy out to infrared wavelengths greater than 20 µm. The refractive index is 2.649 at 10µm.

[edit] Chemical properties

CdTe has very low solubility in water. It is etched by many acids including hydrochloric, and hydrobromic acid, forming (toxic) hydrogen telluride gas.

Cadmium telluride is commercially available as a powder, or as crystals. It can be made into nanocrystals.

[edit] Toxicity

Cadmium telluride is toxic. It should not be ingested, nor its dust inhaled, and it should not be handled without appropriate gloves. Please refer to materials safety data sheets for details.

[edit] See also

• Semiconductor
• Cadmium
• Tellurium

[edit] Related materials

• Mercury telluride
• Mercury(II) cadmium(II) telluride
• Zinc telluride
• Cadmium selenide
• Cadmium zinc telluride

[edit] References

• Properties of Narrow-Gap Cadmium-Based Compounds Ed. P. Capper (INSPEC, IEE, London, UK, 1994) ISBN 0-85296-880-9
• D W Palmer, www.semiconductors.co.uk, 2002.06.
• II-VI Infrared
• Optical properties University of Reading
• Material Safety data Sheet on isp optics web site (MS Word doc)
• Material Safety data Sheet on the web-site of an institute of the Russian Academy of Sciences (html)

[edit] External links

• National Pollutant Inventory - Cadmium and compounds
• National Renewable Energy Laboratory - Cadmium use in Photovoltaics
• MSDS at ISP optics.com (doc)
• MDSD at espimetals.com (pdf)

• Link page to external chemical sources.