Del Mar Photonics
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CdTe (110), 10 X 8 X 3 mm, 2 sides polished 60/40, high resistivity (>/= 10^6
Ohm*cm), n-type, 1 pc.
CdTe, 5 X 5 X 1.3 mm, (110) at 45deg to 5 X 5 mm, 2 sides polished 60/40, high
resistivity (>/= 10^6 Ohm*cm), 7 pcs.
CdTe, 6 X 4 X 2 mm, 6 X 4 // (111), all sides polished 60/40, high resistivity
(>/= 10^6 Ohm*cm), 8 pcs.
CdTe, Dia: 6 X 8 mm, Dia: 6 //(111), high resistivity (>/= 10^6 Ohm*cm), 2
CdTe, Dia: 15 X 2 mm, (110), 2 sides polished 60/40, high resistivity (>/=
10^6 Ohm*cm), 3 pcs.
CdTe, 10 X 10 X 1 mm, random oriented, 2 sides inspection polished, high
resistivity (>/= 10^6 Ohm*cm), 4 pcs.
CdTe, 7 X 5 X 0.5 mm, (110), 3 sides polished 60/40, high resistivity(>/= 10^6
Ohm*cm), 5 pcs.
CdTe, 30 X 2 X 1 mm, 30 X 2 // (110), 2 sides polished 60/40, high resistivity
(>/= 10^6 Ohm*cm), 3 pcs.
CdTe, Dia: 27 X 1.5 mm, (111), 2 sides polished 60/40, high resistivity (>/=
10^6 Ohm*cm),1 pc.
CdTe, 30 X 3 X 3 mm, 30 X 3 // (111), 3 X 3 // (110), all sp 60/40, high
resistivity (>/= 10^6 Ohm*cm), 2 pcs.
CdTe, 10 X 10 X 0.5 mm, (110), 1 side polished 60/40, 1 side fine grinded,
low resistivity, p-type, 2 pcs.
CdTe, 10 X 10 X 0.2 mm, (110), 2 sides polished 60/40, high resistivity (>/=
10^6 Ohm*cm), 1 pc.
CdTe, 10 X 5 X 1 mm, (110), 2 sides polished 60/40, high resistivity(>/= 10^6
Ohm*cm), 1 pc.
CdTe, 5 X 5 X 2 mm, (110), 2 sides polished 60/40, high resistivity (>/= 10^6
Ohm*cm), 1 pc.
CdTe, 10 X 10 X 2 mm, (110)/(110)/(100), 2 sides polished 60/40, high
resistivity (>/= 10^6 Ohm*cm), 1 pcs.
CdTe, 10 X 10 X 0.5 mm, (100), 1 side polished 60/40, 1 side fine grinded,
p-type, 3 pcs.
CdTe, 10 X 10 X 0.5 mm, random oriented, 1 side polished 60/40, 1 side fine
grinded, p-type, 7 pcs.
CdTe, 10 X 10 X 0.5 mm, (100), 2 sides polished 60/40, p-type, 2 pcs.
CdTe, 10 X 10 X 0.5 mm, (110), 2 sides polished 60/40, high resistivity (>/=
10^6 Ohm*cm), 1 pc.
CdTe, 10 X 10 X 0.5 mm, (111), 2 sides polished 60/40, high resistivity (>/=
10^6 Ohm*cm), 1 pc.
CdTe, 10 X 10 X 1 mm, (100), 2 sides polished 60/40, high resistivity (>/=
10^6 Ohm*cm), 4 pcs.
22 CdTe, 20 X 20 X 1 mm, (110), 2 sides polished 40/20, high resistivity (>/=
10^6 Ohm*cm), 1 pc.
Cadmium telluride (CdTe) is a crystalline compound formed from cadmium and
tellurium. It is used as an infrared optical window and a solar cell material.
It is usually sandwiched with cadmium sulfide to form a p-n junction
photovoltaic solar cell. Typically, CdTe cells use a n-i-p structure.
CdTe is a highly useful material in the making of thin film solar cells.
Thin-film CdTe provides a cost-effective solar cell design, but is less
efficient than polysilicon.
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 but
it has small application and is limited by its toxicity such that few optical
houses will consider working with it. An early form of CdTe for IR use was
marketed under the trademarked name of Irtran-6 but this is obsolete.
CdTe is also applied for electro-optic modulators. It has the greatest
electro-optic coefficient of the linear electro-optic effect among II-VI
compound crystals (r41=r52=r63=6.8×10−12 m/V).
CdTe doped with chlorine is used as a radiation detector for x-rays, gamma rays,
beta particles and alpha particles. CdTe can operate at room temperature
allowing the construction of compact detectors for a wide variety of
applications in nuclear spectroscopy. The properties that make CdTe superior
for the realization of high performance gamma- and x-ray detectors are high
atomic number, large bandgap and high electron mobility ~1100 cm2/V·s, which
result in high intrinsic μτ (mobility-lifetime) product and therefore high
degree of charge collection and excellent spectral resolution.
Lattice constant: 0.648 nm at 300K
Young's modulus: 52 GPa
Poisson ratio: 0.41
Thermal conductivity: 6.2 W·m/m2·K at 293 K
Specific heat capacity: 210 J/kg·K at 293 K
Thermal expansion coefficient: 5.9×10−6/K at 293 K
Optical and electronic properties
Fluorescence spectra of colloidal CdTe quantum dots of various sizes, increasing
approximately from 2 to 20 nm from left to right. The red shift of fluorescence
is due to quantum confinement.
Bulk CdTe is transparent in the infrared, from close to its band gap energy
(1.44 eV at 300 K, which corresponds to infrared wavelength of about 860 nm)
out to wavelengths greater than 20 µm; correspondingly, CdTe is fluorescent at
790 nm. When the size of CdTe crystal is being reduced to a few nanometers and
below, thus making a CdTe quantum dot, the fluorescence peak shifts towards
through the visible range to the ultraviolet.
CdTe has very low solubility in water. It is etched by many acids including
hydrochloric, and hydrobromic acid, forming (toxic) hydrogen telluride gas and
toxic cadmium salts. It is a reducing agent and is unstable in air at high
Cadmium telluride is commercially available as a powder, or as crystals. It can
be made into nanocrystals.
Cadmium telluride is toxic if ingested, if its dust is inhaled, or if it is
handled improperly (i.e. without appropriate gloves and other safety
precautions). Once properly and securely captured and encapsulated, CdTe used in
manufacturing processes may be rendered harmless. CdTe appears to be less toxic
than elemental cadmium, at least in terms of acute exposure.
The toxicity is not solely due to the cadmium content. One study found that the
highly reactive surface of cadmium telluride quantum dots triggers extensive
reactive oxygen damage to the cell membrane, mitochondria, and cell nucleus..
In addition, the cadmium telluride films are typically recrystallized in a toxic
solution of cadmium chloride.
The disposal and long term safety of cadmium telluride is a known issue in the
large scale commercialization of cadmium telluride solar panels. Serious efforts
have been made to understand and overcome these issues. A document hosted by the
U.S. National Institutes of Health dated 2003 discloses that:
Brookhaven National Laboratory (BNL) and the U.S. Department of Energy (DOE) are
nominating Cadmium Telluride (CdTe) for inclusion in the National Toxicology
Program (NTP). This nomination is strongly supported by the National Renewable
Energy Laboratory (NREL) and First Solar Inc. The material has the potential for
widespread applications in photovoltaic energy generation that will involve
extensive human interfaces. Hence, we consider that a definitive toxicological
study of the effects of long-term exposure to CdTe is a necessity.
Researchers from the U.S. Department of Energy's Brookhaven National Laboratory
have found that large-scale use of CdTe PV modules does not present any risks to
health and the environment, and recycling the modules at the end of their useful
life completely resolves any environmental concerns. During their operation,
these modules do not produce any pollutants, and furthermore, by displacing
fossil fuels, they offer great environmental benefits. CdTe PV modules appear to
be more environmentally friendly than all other current uses of Cd.
The approach to CdTe safety in the European Union and China is much more
cautious: cadmium and cadmium compounds are considered as toxic carcinogens in
EU whereas China regulations allow Cd products for export only.
P. Capper (1994). Properties of Narrow-Gap Cadmium-Based Compounds. London, UK:
INSPEC, IEE. ISBN 0-85296-880-9.
Palmer, D W (March 2008). "Properties of II-VI Compound Semiconductors".
Bube, R. H. (1955). "Temperature dependence of the width of the band gap in
several photoconductors". Physical Review 98: 431–3.
(PDF) Acute Oral and Inhalation Toxicities in Rats With Cadmium Telluride.
International Journal of Toxicology. 2009-08.
"Unmodified Cadmium Telluride Quantum Dots Prove Toxic". Nano News (National
Cancer Institute). 2005-12-12.
(PDF) Nomination of Cadmium Telluride to the National Toxicology Program. United
States Department of Health and Human Services. 2003-04-11.
Fthenakis, V M (2004). "Life Cycle Impact Analysis of Cadmium in CdTe PV
Production". Renewable & Sustainable Energy Reviews 8: 303–334.
Sinha, Parikhit; Kriegner, Christopher J.; Schew, William A.; Kaczmar,
Swiatoslav W.; Traister, Matthew; Wilson, David J. (2008). "Regulatory policy
governing cadmium-telluride photovoltaics: A case study contrasting life cycle
management with the precautionary principle". Energy Policy 36: 381.
Cadmium Telluride Casts Shadow of Death on First Solar