Editing Selenium (section)

==Applications==

===Manganese electrolysis===
During the [[electrowinning]] of manganese, the addition of [[selenium dioxide]] decreases the power necessary to operate the [[electrolytic cell|electrolysis cells]]. China is the largest consumer of selenium dioxide for this purpose. For every tonne of manganese, an average 2&nbsp;kg selenium oxide is used.<ref name="usgs">{{cite web|title= Selenium and Tellurium: Statistics and Information|url= http://minerals.usgs.gov/minerals/pubs/commodity/selenium/|publisher= United States Geological Survey|access-date= 2012-05-30|archive-date= 2012-05-08|archive-url= https://web.archive.org/web/20120508085217/http://minerals.usgs.gov/minerals/pubs/commodity/selenium/|url-status= dead}}</ref><ref>{{cite journal|doi= 10.1016/j.electacta.2011.06.111|title= Studies of the reduction mechanism of selenium dioxide and its impact on the microstructure of manganese electrodeposit|date= 2011|last1= Sun|first1= Yan|last2= Tian|first2= Xike|last3= He|first3= Binbin|last4= Yang|first4= Chao|last5= Pi|first5= Zhenbang|last6= Wang|first6= Yanxin|last7= Zhang|first7= Suxin|journal= Electrochimica Acta|volume= 56|issue= 24|pages= 8305–8310 |display-authors=3}}</ref> <!--http://www.asianmetal.com/report/en/2008mn_en.pdf-->

===Glass production===
The largest commercial use of selenium, accounting for about 50% of consumption, is for the production of glass. Selenium compounds confer a red color to glass. This color cancels out the green or yellow tints that arise from iron impurities typical for most glass. For this purpose, various selenite and selenate salts are added. For other applications, a red color may be desired, produced by mixtures of CdSe and CdS.<ref name="Ullmann">Bernd E. Langner (2005), "Selenium and Selenium Compounds", ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. {{doi|10.1002/14356007.a23_525}}.</ref>

===Alloys===
Selenium is used with [[bismuth]] in [[brass]]es to replace more toxic [[lead]]. The regulation of lead in drinking water applications such as in the US with the [[Safe Drinking Water Act]] of 1974, made a reduction of lead in brass necessary. The new brass is marketed under the name EnviroBrass.<ref>{{cite book|url= https://books.google.com/books?id=sxkPJzmkhnUC&pg=PA91|page= 91|title= Copper and Copper Alloys|isbn= 978-0-87170-726-0|last1= Davis|first1=Joseph R.|date= 2001 |publisher= ASM Int. }}</ref><!--https://books.google.com/books?id=SZ1RAAAAMAAJ&pg=PA378--> Like lead and sulfur, selenium improves the machinability of steel at concentrations around 0.15%.<ref>{{cite book|url= https://books.google.com/books?id=QahG1Ou1cyEC&pg=PA67|page= 67|title= Cutting Data for Turning of Steel|isbn= 978-0-8311-3314-6|last1= Isakov|first1= Edmund|date= 2008-10-31|publisher= Industrial Press}}</ref><ref>{{cite journal|doi= 10.1007/BF00708374|title= Effect of selenium on the structure and properties of structural steel|date= 1979|last1= Gol'Dshtein|first1=Ya. E.|last2= Mushtakova|first2=T. L.|last3= Komissarova|first3=T. A.|journal= Metal Science and Heat Treatment|volume= 21|issue= 10|pages= 741–746|bibcode= 1979MSHT...21..741G|s2cid= 135853965}}</ref> Selenium produces the same machinability improvement in copper alloys.<ref>{{cite book|url= https://books.google.com/books?id=sxkPJzmkhnUC&pg=PA278 |page=278 |title= Copper and Copper Alloys|isbn= 978-0-87170-726-0|last= Davis |first=Joseph R.|publisher=[[ASM International (society)|ASM International]]|date= 2001}}</ref>

===Lithium–selenium batteries===
The lithium–selenium (Li–Se) battery was considered for energy storage in the family of lithium batteries in the 2010s.<ref>{{cite journal|doi= 10.1039/C6SE00094K|title= The rise of lithium–selenium batteries|date= 2017|last1= Eftekhari|first1=Ali|journal= Sustainable Energy & Fuels|volume= 1|pages= 14–29}}</ref>

===Solar cells===
Selenium was used as the photoabsorbing layer in the first solid-state solar cell, which was demonstrated by the English physicist [[William Grylls Adams]] and his student Richard Evans Day in 1876.<ref>{{cite journal |last1=Adams |first1=William Grylls |last2=Day |first2=Richard Evans |title=The Action of Light on Selenium |journal=Philosophical Transactions of the Royal Society of London |date=1877 |volume=167 |pages=313–349|bibcode=1877RSPT..167..313A }}</ref> Only a few years later, [[Charles Fritts]] fabricated the first thin-film solar cell, also using selenium as the photoabsorber. However, with the emergence of silicon solar cells in the 1950s, research on selenium thin-film solar cells declined. As a result, the record efficiency of 5.0% demonstrated by Tokio Nakada and Akio Kunioka in 1985 remained unchanged for more than 30 years.<ref>{{cite journal |last1=Nakada |first1=Tokio |last2=Kunioka |first2=Akio |title=Polycrystalline Thin-Film TiO 2 /Se Solar Cells |journal=Japanese Journal of Applied Physics |date=1 July 1985 |volume=24 |issue=7A |pages=L536 |doi=10.1143/JJAP.24.L536|bibcode=1985JaJAP..24L.536N |s2cid=118838432 }}</ref> In 2017, researchers from [[IBM]] achieved a new record efficiency of 6.5% by redesigning the device structure.<ref>{{cite journal |last1=Todorov |first1=Teodor K. |last2=Singh |first2=Saurabh |last3=Bishop |first3=Douglas M. |last4=Gunawan |first4=Oki |last5=Lee |first5=Yun Seog |last6=Gershon |first6=Talia S. |last7=Brew |first7=Kevin W. |last8=Antunez |first8=Priscilla D. |last9=Haight |first9=Richard |title=Ultrathin high band gap solar cells with improved efficiencies from the world's oldest photovoltaic material |journal=Nature Communications |date=25 September 2017 |volume=8 |issue=1 |page=682 |doi=10.1038/s41467-017-00582-9|pmid=28947765 |pmc=5613033 |bibcode=2017NatCo...8..682T }}</ref> Following this achievement, selenium has gained renewed interest as a wide bandgap photoabsorber with the potential of being integrated in [[Multi-junction solar cell|tandem]] with lower bandgap photoabsorbers.<ref>{{cite journal |last1=Youngman |first1=Tomas H. |last2=Nielsen |first2=Rasmus |last3=Crovetto |first3=Andrea |last4=Seger |first4=Brian |last5=Hansen |first5=Ole |last6=Chorkendorff |first6=Ib |last7=Vesborg |first7=Peter C. K. |title=Semitransparent Selenium Solar Cells as a Top Cell for Tandem Photovoltaics |journal=Solar RRL |date=July 2021 |volume=5 |issue=7 |doi=10.1002/solr.202100111|s2cid=235575161 }}</ref> In 2024, the first selenium-based tandem solar cell was demonstrated, showcasing a selenium top cell monolithically integrated with a silicon bottom cell.<ref>{{cite journal |last1=Nielsen |first1=Rasmus |last2=Crovetto |first2=Andrea |last3=Assar |first3=Alireza |last4=Hansen |first4=Ole |last5=Chorkendorff |first5=Ib |last6=Vesborg |first6=Peter C.K. |title=Monolithic Selenium/Silicon Tandem Solar Cells |journal=PRX Energy |date=12 March 2024 |volume=3 |issue=1 |page=013013 |doi=10.1103/PRXEnergy.3.013013|arxiv=2307.05996 |bibcode=2024PRXE....3a3013N }}</ref> However, a significant deficit in the [[open-circuit voltage]] is currently the main limiting factor to further improve the efficiency, necessitating defect-engineering strategies for selenium thin-films to enhance the [[carrier lifetime]].<ref>{{cite journal |last1=Nielsen |first1=Rasmus |last2=Youngman |first2=Tomas H. |last3=Moustafa |first3=Hadeel |last4=Levcenco |first4=Sergiu |last5=Hempel |first5=Hannes |last6=Crovetto |first6=Andrea |last7=Olsen |first7=Thomas |last8=Hansen |first8=Ole |last9=Chorkendorff |first9=Ib |last10=Unold |first10=Thomas |last11=Vesborg |first11=Peter C. K. |title=Origin of photovoltaic losses in selenium solar cells with open-circuit voltages approaching 1 V |journal=Journal of Materials Chemistry A |date=2022 |volume=10 |issue=45 |pages=24199–24207 |doi=10.1039/D2TA07729A|s2cid=253315416 }}</ref><ref>{{Cite journal |last1=Nielsen |first1=Rasmus S. |last2=Gunawan |first2=Oki |last3=Todorov |first3=Teodor |last4=Møller |first4=Clara B. |last5=Hansen |first5=Ole |last6=Vesborg |first6=Peter C. K. |date=3 April 2025 |title=Variable-temperature and carrier-resolved photo-Hall measurements of high-performance selenium thin-film solar cells |journal=Physical Review B |volume=111 |issue=16 |pages=165202 |doi=10.1103/PhysRevB.111.165202 |arxiv=2409.12804 |bibcode=2025PhRvB.111p5202N |issn=2469-9950}}</ref> As of now, the only defect-engineering strategy that has been investigated for selenium thin-film solar cells involves [[Laser-heated pedestal growth|crystallizing selenium using a laser]].<ref>{{cite journal |last1=Nielsen |first1=Rasmus |last2=Hemmingsen |first2=Tobias H. |last3=Bonczyk |first3=Tobias G. |last4=Hansen |first4=Ole |last5=Chorkendorff |first5=Ib |last6=Vesborg |first6=Peter C. K. |title=Laser-Annealing and Solid-Phase Epitaxy of Selenium Thin-Film Solar Cells |journal=ACS Applied Energy Materials |date=11 September 2023 |volume=6 |issue=17 |pages=8849–8856 |doi=10.1021/acsaem.3c01464|arxiv=2306.11311 |s2cid=259203956 }}</ref>

===Photoconductors===
Amorphous selenium (α-Se) thin films have found application as photoconductors in [[flat-panel detector|flat-panel X-ray detectors]]. These detectors use amorphous selenium to capture and convert incident X-ray photons directly into electric charge. Selenium has been chosen for this application among other semiconductors owing to a combination of its favorable technological and physical properties:<ref name=r1>{{cite journal|doi=10.1109/JSEN.2019.2950319|title=Recent Developments of Amorphous Selenium-Based X-Ray Detectors: A Review |year=2020 |last1=Huang |first1=Heyuan |last2=Abbaszadeh |first2=Shiva |journal=IEEE Sensors Journal |volume=20 |issue=4 |pages=1694–1704 |bibcode=2020ISenJ..20.1694H |s2cid=208833373 |doi-access=free }}</ref><ref name=r2>{{cite journal|doi=10.1002/pssb.200982007|title=Amorphous selenium and its alloys from early xeroradiography to high resolution X-ray image detectors and ultrasensitive imaging tubes |year=2009 |last1=Kasap |first1=Safa |last2=Frey |first2=Joel B. |last3=Belev |first3=George |last4=Tousignant |first4=Olivier |last5=Mani |first5=Habib |last6=Laperriere |first6=Luc |last7=Reznik |first7=Alla|author7-link=Alla Reznik |last8=Rowlands |first8=John A. |journal=Physica Status Solidi B |volume=246 |issue=8 |pages=1794–1805 |bibcode=2009PSSBR.246.1794K |s2cid=122848842 }}</ref>
# Amorphous selenium has a low melting point, high vapor pressure, and uniform structure. These three properties allow quick and easy deposition of large-area uniform films with a thickness up to 1&nbsp;mm at a rate of 1–5&nbsp;μm/min. Their uniformity and lack of grain boundaries, which are intrinsic to polycrystalline materials, improve the X-ray image quality. Meanwhile the large area is essential for scanning the human body or luggage items. 
# Selenium is less toxic than many compound semiconductors that contain arsenic or heavy metals such as mercury or lead.
# The mobility in applied electric field is sufficiently high both for electrons and holes, so that in a typical 0.2&nbsp;mm thick device, c. 98% of electrons and holes produced by X-rays are collected at the electrodes without being trapped by various defects. Consequently, device sensitivity is high, and its behavior is easy to describe by simple transport equations.

===Rectifiers===
[[Selenium rectifier]]s were first used in 1933. They have mostly been replaced by silicon-based devices. One notable exception is in power DC [[surge protection]], where the superior energy capabilities of selenium suppressors make them more desirable than [[metal-oxide varistor]]s.{{citation needed|date=July 2023}}

===Other uses===
The demand for selenium by the electronics industry is declining.<ref name="usgs" /> Its [[photovoltaics|photovoltaic]] and [[photoconductivity|photoconductive]] properties are still useful in [[photocopying]],<ref>{{cite journal|doi =10.1080/03086648808079729|title =Application of Selenium-Tellurium Photoconductors to the Xerographic Copying and Printing Processes|date =1988|last1 =Springett|first1 = B. E.|journal =Phosphorus and Sulfur and the Related Elements|volume =38|issue =3–4|pages =341–350}}</ref><ref>{{cite book|url =https://books.google.com/books?id=y1BuoXpPX3kC&pg=PA547| pages =547–548|title =Computer Systems Architecture: A Networking Approach|isbn =978-0-321-34079-5|last=Williams |first=Rob|date =2006| publisher= Prentice Hall}}</ref><ref>{{cite book|chapter-url =https://books.google.com/books?id=y8U4HGZP_O0C&pg=PA81| pages= 81–83| chapter= The Laser Printer|publisher =Wiley-VCH|title =Lasers|isbn =978-3-527-64005-8|last1=Diels |first1=Jean-Claude|last2=Arissian |first2=Ladan|date =2011}}</ref><ref>{{cite book|url =https://books.google.com/books?id=BiOxDxNMeyoC&pg=PA3| pages=3–5| publisher = Springer|title =Organic Electronics|isbn =978-3-642-04537-0|author =Meller, Gregor|author2 =Grasser, Tibor|name-list-style =amp|date =2009}}</ref><!--The use of tellurium-doped selenium was first displaced by amorphous silicon and now organic photosensitive polymers took over making the selenium drums obsolete technology.--> [[photocell]]s, [[light meter]]s and [[solar cell]]s. Its use as a photoconductor in plain-paper copiers once was a leading application, but in the 1980s, the photoconductor application declined (although it was still a large end-use) as more and more copiers switched to organic photoconductors.{{Citation needed|date=June 2024}}

[[Zinc selenide]] was the first material for blue [[LED]]s, but [[gallium nitride]] dominates that market.<ref>{{cite book |last=Normile |first=Dennis |title=Popular Science |date=2000 |page=57 |chapter=The birth of the Blues |chapter-url=https://books.google.com/books?id=D2zyNlMu7kkC&pg=PA57}}</ref> [[Cadmium selenide]] can be used to make [[quantum dot]]s.<ref>{{cite journal|doi=10.1021/ed300568e |title=Simple Syntheses of CdSe Quantum Dots |date=2014 |last1=Landry |first1=Matthew L. |last2=Morrell |first2=Thomas E. |last3=Karagounis |first3=Theodora K. |last4=Hsia |first4=Chih-Hao |last5=Wang |first5=Chia-Ying |journal=Journal of Chemical Education |volume=91 |issue=2 |pages=274–279 |bibcode=2014JChEd..91..274L }}</ref> Sheets of amorphous selenium convert [[X-ray]] images to patterns of charge in [[xeroradiography]] and in solid-state, flat-panel X-ray cameras.<ref>{{cite journal |last1=Kasap |first1=Safa |last2=Frey |first2=Joel B. |last3=Belev |first3=George |last4=Tousignant |first4=Olivier |last5=Mani |first5=Habib |last6=Laperriere |first6=Luc |last7=Reznik |first7=Alla |last8=Rowlands |first8=John A. |display-authors=3 |date=2009 |title=Amorphous selenium and its alloys from early xeroradiography to high resolution X-ray image detectors and ultrasensitive imaging tubes |journal=Physica Status Solidi B |volume=246 |issue=8 |pages=1794–1805 |bibcode=2009PSSBR.246.1794K |doi=10.1002/pssb.200982007 |s2cid=122848842}}</ref> Ionized selenium (Se+24, where 24 of the outer D, S and P orbitals are stripped away due to high input energies{{clarify|date=April 2023}}) is one of the active mediums used in X-ray lasers.<ref>{{Cite book |last=Svelto |first=Orazio |title=Principles of LASERs fourth ed |publisher=Plenum |year=1998 |isbn=978-0-306-45748-7 |pages=457}}</ref> <sup>75</sup>Se is used as a gamma source in industrial radiography.<ref>{{cite news |last1=Hayward |first1=Peter |last2=Currie |first2=Dean |title=Radiography of Welds Using Selenium 75, Ir 192 and X-rays |url=http://www.ndt.net/article/apcndt2006/papers/12.pdf}}</ref>

Selenium catalyzes some chemical reactions, but it is not widely used because of issues with toxicity.<ref>{{Cite journal|url=https://pubs.rsc.org/en/content/articlehtml/2019/cy/c8cy02274g|doi = 10.1039/C8CY02274G|title = Selenium reagents as catalysts|year = 2019|last1 = Singh|first1 = Fateh V.|last2 = Wirth|first2 = Thomas|journal = Catalysis Science & Technology|volume = 9|issue = 5|pages = 1073–1091|s2cid = 104468775}}</ref> In [[X-ray crystallography]], incorporation of one or more selenium atoms in place of sulfur helps with multiple-wavelength anomalous dispersion and [[single wavelength anomalous dispersion]] phasing.<ref>{{cite journal|doi= 10.1098/rspa.1993.0087|title= New Techniques of Applying Multi-Wavelength Anomalous Scattering Data|date= 1993|last1= Hai-Fu|first1= F.|last2= Woolfson|first2=M. M.|last3= Jia-Xing|first3= Y.|journal= Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume= 442|issue= 1914|pages= 13–32|bibcode= 1993RSPSA.442...13H |s2cid= 122722520}}</ref>

Selenium is used in the [[photographic print toning|toning of photographic prints]], and it is sold as a toner by numerous photographic manufacturers. Selenium intensifies and extends the tonal range of black-and-white photographic images and improves the permanence of prints.<ref>{{cite journal |last=MacLean |first=Marion E. |date=1937 |title=A project for general chemistry students: Color toning of photographic prints |journal=Journal of Chemical Education |volume=14 |issue=1 |page=31 |bibcode=1937JChEd..14...31M |doi=10.1021/ed014p31}}</ref><ref>{{cite journal |last=Penichon |first=Sylvie |date=1999 |title=Differences in Image Tonality Produced by Different Toning Protocols for Matte Collodion Photographs |journal=Journal of the American Institute for Conservation |volume=38 |issue=2 |pages=124–143 |doi=10.2307/3180042 |jstor=3180042}}</ref><ref>{{cite book |last=McKenzie |first=Joy |url=https://archive.org/details/exploringbasicbl0000mcke |title=Exploring Basic Black & White Photography |date=2003 |publisher=Delmar |isbn=978-1-4018-1556-1 |page=[https://archive.org/details/exploringbasicbl0000mcke/page/176 176] |url-access=registration}}</ref> Small amounts of organoselenium compounds have been used to modify the catalysts used for the [[sulfur vulcanization|vulcanization]] for the production of rubber.<ref name="Naumov" /> Selenium is used in some anti-dandruff shampoos in the form of [[selenium disulfide]] such as Selsun and Vichy Dereos<ref>{{Cite web |title=What is Dandruff? |url=https://www.vichy.co.uk/on/demandware.static/-/Sites-vic-master-catalog/default/dw41dcc5e7/VIC/ProductImages/Blog-Imagery-Vichy/Vichy_Customer_Leaflet_Dandruff.pdf |access-date=3 October 2023 |website=Vichy UK}}</ref> brands.