Cadmium telluride

Irtran -6

Odorless black solid

Fixed

5.85 g · cm -3

1092 ° C

1121 ° C

Insoluble in water

Attention

0.1 mg · m-3 (based on Te)

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Cadmium telluride (CdTe ) is a crystalline compound from the group of Telluride, which is formed from cadmium and tellurium with a ( cubic ) zinc blende crystal structure (space group F43m ). In its crystalline form, there is a direct band gap II-VI semiconductors. CdTe is also a good solar cell material. It is usually used as a layer structure with cadmium sulfide, to form a pn junction, for example a solar cell or a photodiode.

Use

CdTe is an absorber material for solar cells. It is cheaper than silicon, particularly as thin-film solar cell, but not as powerful. CdTe as a solid solution with mercury telluride HgTe is a versatile infrared detector material (Hg, Cd) Te. CdTe as a solid solution with zinc telluride ZnTe forms an excellent X-ray and gamma-ray detector material (Cd, Zn) Te.

CdTe is used as a material for optical lenses, windows, and in the infrared region, but it only has a small scope. Its use is limited by its adverse health classification, so that only a few optics manufacturers are working with CdTe. An early form of CdTe for IR use was marketed under the trade name Irtran -6, but this is obsolete.

CdTe is used as an electro-optic modulator. It has the same electro-optic coefficient of the linear electro-optical effect of all the II-VI composite crystals.

Properties

Physical Properties

• Lattice constant: 0.648 nm at 300 K
• Modulus of elasticity: 52 GPa
• Poisson's ratio: 0.41

Thermal Properties

• Thermal conductivity: 6.2 W / (m K) at 293 K
• Specific heat capacity: 210 J / ( kg K) at 293 K
• Coefficient of thermal expansion: 5.9 × 10-6 / K at 293 K

Electronic Properties

• The direct band gap is 1.56 eV at 300 K.
• Effective mass of the electron me 0.11
• Effective mass of the hole 0.4 me

Optical Properties

CdTe is in the infrared range (from close to its band gap energy ( = 795 nm) up to wavelengths greater than 20 microns ) transparent. The refractive index is 2.649 at 10 microns.

Chemical Properties

CdTe is very slightly soluble in water. It is decomposed by many acids, including hydrochloric acid and hydrobromic acid to form ( toxic ) Tellurwasserstoffgas.

Safety

Cadmium is harmful. The greatest danger - with up to 90 % absorption rate - in the absorption of particulate matter through the respiratory tract; the rate of uptake from the gastrointestinal tract, however, is only about 5%.

Related compounds

• Mercury telluride ( HgTe, CAS: 12068-90-5 )
• Zinc telluride ( ZnTe, CAS: 1315-11-3 )
• Cadmium selenide ( CdSe, CAS: 1306-24-7 )