Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Cadmium telluride
open-in-new
<h2 id="applications">Applications</h2> <p class="note">See also: <a href="/facts/Cadmium_telluride_photovoltaics/fntm90oN">Cadmium telluride photovoltaics</a></p> <p>CdTe is used to make <a href="/facts/Thin_film_solar_cell/54UK9nKn">thin film solar cells</a>, accounting for about 8% of all solar cells installed in 2011.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> They are among the lowest-cost types of solar cell,<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> although a comparison of total installed cost depends on installation size and many other factors, and has changed rapidly from year to year. The CdTe solar cell market is dominated by <a href="/facts/First_Solar/7dAPFyH9">First Solar</a>. In 2011, around 2 <a href="/facts/Watt-peak/tFTC5jCa">GWp</a> of CdTe solar cells were produced;<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> For more details and discussion see <a href="/facts/Cadmium_telluride_photovoltaics/fntm90oN">cadmium telluride photovoltaics</a>. </p><p>CdTe can be <a href="/facts/Alloy/I7w7WQWR">alloyed</a> with <a href="/facts/Mercury_(element)/WlxfoHva">mercury</a> to make a versatile <a href="/facts/Infrared_detector/pK7SfsEv">infrared detector</a> material (<a href="/facts/Mercury_cadmium_telluride/kzgN6aJn">HgCdTe</a>). CdTe alloyed with a small amount of <a href="/facts/Zinc/80b1qgk3">zinc</a> makes an excellent solid-state <a href="/facts/X-ray/wseP79cN">X-ray</a> and <a href="/facts/Gamma_ray/5Drf913J">gamma ray</a> detector (<a href="/facts/Cadmium_zinc_telluride/yqG0NEUa">CdZnTe</a>). </p><p>CdTe is used as an <a href="/facts/Infrared/44XdJNcc">infrared</a> optical material for <a href="/facts/Optical_window/ur52Kl8b">optical windows</a> and <a href="/facts/Lens_(optics)/ejlH6n5c">lenses</a> and is proven to provide a good performance across a wide range of temperatures.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> An early form of CdTe for IR use was marketed under the trademarked name of <i>Irtran-6</i>, but this is obsolete. </p><p>CdTe is also applied for <a href="/facts/Electro-optic_modulator/0qFT00Lf">electro-optic modulators</a>. It has the greatest electro-optic coefficient of the linear <a href="/facts/Electro-optic_effect/FNXrlPS2">electro-optic effect</a> among II-VI compound crystals (r41=r52=r63=6.8×10−12 m/V). </p><p>CdTe doped with <a href="/facts/Chlorine/y27UwYBM">chlorine</a> is used as a radiation detector for x-rays, gamma rays, <a href="/facts/Beta_particle/x8b3ttLn">beta particles</a> and <a href="/facts/Alpha_particle/dzNMs9WP">alpha particles</a>. CdTe can operate at room temperature allowing the construction of compact detectors for a wide variety of applications in nuclear spectroscopy.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> 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.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Due to the poor charge transport properties of holes, ~100 cm2/V·s, single-carrier-sensing detector geometries are used to produce high resolution spectroscopy; these include coplanar grids, Frisch-collar detectors and <a href="/facts/HEXITEC/Jlr8wE60">small pixel</a> detectors. </p> <h2 id="physical-properties">Physical properties</h2> <ul><li><a href="/facts/Thermal_expansion_coefficient/BP2vjX0N">Thermal expansion coefficient</a>: 5.9×10−6/K at 293 K<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a></li> <li><a href="/facts/Young%27s_modulus/MV5JMCIM">Young's modulus</a>: 52 GPa</li> <li><a href="/facts/Poisson_ratio/ppIsaujA">Poisson ratio</a>: 0.41</li></ul> <h3>Optical and electronic properties</h3> <p>Bulk CdTe is <a href="/facts/Transparency_(optics)/PRryNNW6">transparent</a> in the <a href="/facts/Infrared/44XdJNcc">infrared</a>, from close to its band gap energy (1.5 eV at 300 K,<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> which corresponds to infrared wavelength of about 830 nm) out to <a href="/facts/Wavelength/kcJU0ymz">wavelengths</a> greater than 20 μm; correspondingly, CdTe is <a href="/facts/Fluorescence/qsJVT2qP">fluorescent</a> at 790 nm. As the size of CdTe crystals are reduced to a few nanometers or less, thus making them CdTe <a href="/facts/Quantum_dot/K5Ytv8Yw">quantum dots</a>, the fluorescence peak shifts through the visible range into the ultraviolet. </p> <h2 id="chemical-properties">Chemical properties</h2> <p>CdTe is <a href="/facts/Insoluble/kLE9h3Jb">insoluble</a> in water.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> CdTe has a high melting point of 1,041 °C (1,906 °F) with evaporation starting at 1,050 °C (1,920 °F).<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> CdTe has a vapor pressure of zero at ambient temperatures. CdTe is more stable than its parent compounds cadmium and tellurium and most other Cd compounds, due to its high melting point and insolubility.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>Cadmium telluride is commercially available as a powder, or as crystals. It can be made into nanocrystals. </p> <h2 id="toxicology-assessment">Toxicology assessment</h2> <p>The compound CdTe has different qualities than the two elements, cadmium and tellurium, taken separately. CdTe has low acute inhalation, oral, and aquatic toxicity, and is negative in the Ames mutagenicity test. Based on notification of these results to the <a href="/facts/European_Chemicals_Agency/5UVljucv">European Chemicals Agency</a> (ECHA), CdTe is no longer classified as harmful if ingested nor harmful in contact with skin, and the toxicity classification to aquatic life has been reduced.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Once properly and securely captured and encapsulated, CdTe used in manufacturing processes may be rendered harmless. Current CdTe modules pass the U.S. EPA's Toxicity Characteristic Leaching Procedure (TCLP) test, designed to assess the potential for long-term leaching of products disposed in landfills.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>A document hosted by the U.S. National Institutes of Health<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> dated 2003 discloses the following: </p> <p>Brookhaven National Laboratory (BNL) and the <a href="/facts/U.S._Department_of_Energy/PRp6Cz8g">U.S. Department of Energy</a> (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 <a href="/facts/First_Solar/7dAPFyH9">First Solar</a> 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.</p> <p>According to the classification provided by companies to the European Chemicals Agency (ECHA) in REACH registrations, it is still harmful to aquatic life with long lasting effects. </p><p>Additionally, the classification provided by companies to ECHA notifications classifies it as very toxic to aquatic life with long lasting effects, very toxic to aquatic life, harmful if inhaled or swallowed and is harmful in contact with skin.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> </p> <h2 id="availability">Availability</h2> <p>At the present time, the prices of the raw materials <a href="/facts/Cadmium/wXkV2eIX">cadmium</a> and <a href="/facts/Tellurium/v7QvfIvS">tellurium</a> are a negligible proportion of the cost of CdTe solar cells and other CdTe devices. However, tellurium is a relatively rare element (1–5 parts per billion in the Earth's crust; see <a href="/facts/Abundances_of_the_elements_(data_page)/TdvtPnKV">Abundances of the elements (data page)</a>). Through improved <a href="/facts/Material_efficiency/GjsSSNoE">material efficiency</a> and increased PV recycling systems, the CdTe PV industry has the potential to fully rely on tellurium from recycled end-of-life modules by 2038.<a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> See <a href="/facts/Cadmium_telluride_photovoltaics/fntm90oN">Cadmium telluride photovoltaics</a> for more information. Another study shows that CdTe PV recycling will add a significant secondary resource of Te which, in conjunction with improved material utilization, will enable a cumulative capacity of about 2 TW by 2050 and 10 TW by the end of the century.<a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Cadmium_selenide/A7Xyr215">Cadmium selenide</a></li> <li><a href="/facts/Cadmium_telluride_photovoltaics/fntm90oN">Cadmium telluride photovoltaics</a></li> <li><a href="/facts/Cadmium_zinc_telluride/yqG0NEUa">Cadmium zinc telluride</a></li> <li><a href="/facts/First_Solar/7dAPFyH9">First Solar</a></li> <li><a href="/facts/Mercury_telluride/dv6H5QYU">Mercury telluride</a></li> <li><a href="/facts/Mercury(II)_cadmium(II)_telluride/kzgN6aJn">Mercury(II) cadmium(II) telluride</a></li> <li><a href="/facts/Zinc_telluride/09dzJv8U">Zinc telluride</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="https://web.archive.org/web/20070125125715/http://www.sttic.com.ru/lpcbc/DANDP/cdte_adv.html">CdTe page on the web-site of the Institute of Solid State Physics of the Russian Academy of Sciences (html)</a></li> <li><a href="http://www.reading.ac.uk/infrared/library/infraredmaterials/ir-infraredmaterials-cdte.asp">Optical properties</a> University of Reading, Infrared Multilayer Laboratory</li> <li><a href="https://web.archive.org/web/20070125125715/http://www.sttic.com.ru/lpcbc/DANDP/cdte_adv.html">CdTe: single crystals, grown by HPVB and HPVZM techniques; windows, substrates, electrooptical modulators. Infrared transmittance spectrum. MSDS.</a></li> <li><a href="https://web.archive.org/web/20061210213049/http://www.npi.gov.au/database/substance-info/profiles/17.html">National Pollutant Inventory – Cadmium and compounds</a></li> <li><a href="https://web.archive.org/web/20150602085154/http://www.ispoptics.com/new_webpage/MSDS%20CdTe.doc">MSDS at ISP optics.com</a> (doc)</li> <li><a href="https://web.archive.org/web/20080309103941/http://www.espimetals.com/msds's/cadmiumtelluride.pdf">MDSD at espimetals.com</a> (pdf)</li> <li><a href="https://web.archive.org/web/20150602085154/http://www.ispoptics.com/new_webpage/MSDS%20CdTe.doc">Material Safety data Sheet</a> on isp optics web site (MS Word doc)</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Photovoltaics report" (PDF). Archived from the original (PDF) on 2012-11-05. <a href="https://web.archive.org/web/20121105154721/http://www.ise.fraunhofer.de/de/downloads/pdf-files/aktuelles/photovoltaics-report.pdf" target="_blank">https://web.archive.org/web/20121105154721/http://www.ise.fraunhofer.de/de/downloads/pdf-files/aktuelles/photovoltaics-report.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Introduction". Chalcogenide Photovoltaics. 2011. pp. 1–8. doi:10.1002/9783527633708.ch1. ISBN 9783527633708. <a href="9783527633708" target="_blank">9783527633708</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Photovoltaics report" (PDF). Archived from the original (PDF) on 2012-11-05. <a href="https://web.archive.org/web/20121105154721/http://www.ise.fraunhofer.de/de/downloads/pdf-files/aktuelles/photovoltaics-report.pdf" target="_blank">https://web.archive.org/web/20121105154721/http://www.ise.fraunhofer.de/de/downloads/pdf-files/aktuelles/photovoltaics-report.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Cadmium Telluride". <a href="http://www.reading.ac.uk/infrared/library/infraredmaterials" target="_blank">http://www.reading.ac.uk/infrared/library/infraredmaterials</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>P. Capper (1994). Properties of Narrow-Gap Cadmium-Based Compounds. London, UK: INSPEC, IEE. ISBN 978-0-85296-880-2. <a href="978-0-85296-880-2" target="_blank">978-0-85296-880-2</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Veale, M. C.; Kalliopuska, J.; Pohjonen, H.; Andersson, H.; Nenonen, S.; Seller, P.; Wilson, M. D. (2012). "Characterization of M-π-n CdTe pixel detectors coupled to HEXITEC readout chip". Journal of Instrumentation. 7 (1): C01035. Bibcode:2012JInst...7C1035V. doi:10.1088/1748-0221/7/01/C01035. <a href="https://doi.org/10.1088%2F1748-0221%2F7%2F01%2FC01035" target="_blank">https://doi.org/10.1088%2F1748-0221%2F7%2F01%2FC01035</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Palmer, D W (March 2008). "Properties of II-VI Compound Semiconductors". Semiconductors-Information. <a href="http://www.semiconductors.co.uk/propiivi5410.htm" target="_blank">http://www.semiconductors.co.uk/propiivi5410.htm</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Fonthal, G.; et al. (2000). "Temperature dependence of the band gap energy of crystalline CdTe". J. Phys. Chem. Solids. 61 (4): 579–583. Bibcode:2000JPCS...61..579F. doi:10.1016/s0022-3697(99)00254-1. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Solubility is below 0.1mg/L which equals a classification as insoluble- reference, "ECHA Substance Registration"[1] Archived 2013-12-13 at archive.today <a href="http://apps.echa.europa.eu/registered/data/dossiers/DISS-dffb4072-e283-47ae-e044-00144f67d031/DISS-dffb4072-e283-47ae-e044-00144f67d031_DISS-dffb4072-e283-47ae-e044-00144f67d031.html" target="_blank">http://apps.echa.europa.eu/registered/data/dossiers/DISS-dffb4072-e283-47ae-e044-00144f67d031/DISS-dffb4072-e283-47ae-e044-00144f67d031_DISS-dffb4072-e283-47ae-e044-00144f67d031.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"Cadmium Telluride". Archived from the original on 2013-12-13. Retrieved 2013-12-13. <a href="https://archive.today/20131213155005/http://apps.echa.europa.eu/registered/data/dossiers/DISS-dffb4072-e283-47ae-e044-00144f67d031/DISS-dffb4072-e283-47ae-e044-00144f67d031_DISS-dffb4072-e283-47ae-e044-00144f67d031.html" target="_blank">https://archive.today/20131213155005/http://apps.echa.europa.eu/registered/data/dossiers/DISS-dffb4072-e283-47ae-e044-00144f67d031/DISS-dffb4072-e283-47ae-e044-00144f67d031_DISS-dffb4072-e283-47ae-e044-00144f67d031.html</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>S. Kaczmar (2011). "Evaluating the read-across approach on CdTe toxicity for CdTe photovoltaics" (PDF).[permanent dead link] <a href="ftp://ftp.co.imperial.ca.us/icpds/eir/campo-verde-solar/final/evaluating-toxicity.pdf" target="_blank">ftp://ftp.co.imperial.ca.us/icpds/eir/campo-verde-solar/final/evaluating-toxicity.pdf</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>"Scientific Comment of Fraunhofer to Life Cycle Assessement [sic] of CdTe Photovoltaics". Fraunhofer Center for Silicon Photovoltaics CSP. Archived from the original on 2013-12-13. <a href="https://web.archive.org/web/20131213174834/http://www.csp.fraunhofer.de/presse-und-veranstaltungen/details/id/47/" target="_blank">https://web.archive.org/web/20131213174834/http://www.csp.fraunhofer.de/presse-und-veranstaltungen/details/id/47/</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>V. Fthenakis; K. Zweibel (2003). "CdTe PV: Real and Perceived EHS Risks" (PDF). National Renewable Energy Laboratory. <a href="http://www.nrel.gov/docs/fy03osti/33561.pdf" target="_blank">http://www.nrel.gov/docs/fy03osti/33561.pdf</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Nomination of Cadmium Telluride to the National Toxicology Program (PDF) (Report). United States Department of Health and Human Services. 2003-04-11. <a href="https://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/cdte_508.pdf" target="_blank">https://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/cdte_508.pdf</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>"Cadmium telluride - Brief Profile - ECHA". European Chemicals Agency. 2020. <a href="https://echa.europa.eu/brief-profile/-/briefprofile/100.013.773" target="_blank">https://echa.europa.eu/brief-profile/-/briefprofile/100.013.773</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>M. Marwede; A. Reller (2012). "Future recycling flows of tellurium from cadmium telluride photovoltaic waste" (PDF). Resources, Conservation and Recycling. 69: 35–49. doi:10.1016/j.resconrec.2012.09.003. <a href="https://depositonce.tu-berlin.de/bitstream/11303/7375/3/2012_marwede_et-al.pdf" target="_blank">https://depositonce.tu-berlin.de/bitstream/11303/7375/3/2012_marwede_et-al.pdf</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Fthenakis, V.M. (2012). "Sustainability metrics for extending thin-film photovoltaics to terawatt levels". MRS Bulletin. 37 (4): 425–430. doi:10.1557/mrs.2012.50. <a href="https://doi.org/10.1557%2Fmrs.2012.50" target="_blank">https://doi.org/10.1557%2Fmrs.2012.50</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> </ol>