Editing Phosphor (section)

===White LEDs===
White [[light-emitting diode]]s are usually blue [[InGaN]] LEDs with a coating of a suitable material. [[Cerium]](III)-doped [[Yttrium aluminium garnet|YAG]] ('''YAG:Ce<sup>3+</sup>''', or '''Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup>''') is often used; it absorbs the light from the blue LED and emits in a broad range from greenish to reddish, with most of its output in yellow. This yellow emission combined with the remaining blue emission gives the "white" light, which can be adjusted to color temperature as warm (yellowish) or cold (bluish) white. The pale yellow emission of the Ce<sup>3+</sup>:YAG can be tuned by substituting the cerium with other rare-earth elements such as [[terbium]] and [[gadolinium]] and can even be further adjusted by substituting some or all of the aluminium in the YAG with gallium. However, this process is not one of phosphorescence. The yellow light is produced by a process known as [[scintillation (physics)|scintillation]], the complete absence of an afterglow being one of the characteristics of the process.

Some [[rare-earth]]-[[dopant|doped]] [[Sialon]]s are [[photoluminescent]] and can serve as phosphors. [[Europium]](II)-doped β-SiAlON absorbs in [[ultraviolet]] and [[visible light]] spectrum and emits intense broadband visible emission. Its luminance and color does not change significantly with temperature, due to the temperature-stable crystal structure. It has a great potential as a green down-conversion phosphor for white [[LED]]s; a yellow variant also exists (α-SiAlON<ref>{{Cite web|url=https://tech.nikkeibp.co.jp/dm/english/NEWS_EN/20090915/175305/|title=Sharp to Employ White LED Using Sialon|last=XTECH|first=NIKKEI|website=NIKKEI XTECH|language=en|access-date=2019-01-10}}</ref>). For white LEDs, a blue LED is used with a yellow phosphor, or with a green and yellow SiAlON phosphor and a red CaAlSiN<sub>3</sub>-based (CASN) phosphor.<ref>{{cite journal|url=http://www.science24.com/paper/15977|title=Luminescence and temperature dependency of β-SiAlON phosphor|author=Youn-Gon Park|journal=Samsung Electro Mechanics Co|display-authors=etal|url-status=dead|archive-url=https://web.archive.org/web/20100412152349/http://www.science24.com/paper/15977|archive-date=2010-04-12|access-date=2009-09-24}}</ref><ref>{{cite news|url=http://techon.nikkeibp.co.jp/english/NEWS_EN/20090915/175305/|title=Sharp to Employ White LED Using Sialon|date=Sep 15, 2009|author=Hideyoshi Kume, Nikkei Electronics|url-status=live|archive-url=https://web.archive.org/web/20120223124648/http://techon.nikkeibp.co.jp/english/NEWS_EN/20090915/175305/|archive-date=2012-02-23}}</ref><ref>{{cite journal|url=http://sciencelinks.jp/j-east/article/200602/000020060205A1031052.php|title=New sialon phosphors and white LEDs|author=Naoto, Hirosaki|journal=Oyo Butsuri|volume=74|issue=11|page=1449|year=2005|display-authors=etal|url-status=dead|archive-url=https://web.archive.org/web/20100404151444/http://sciencelinks.jp/j-east/article/200602/000020060205A1031052.php|archive-date=2010-04-04}}</ref>

White LEDs can also be made by coating near-ultraviolet-emitting LEDs with a mixture of high-efficiency europium-based red- and blue-emitting phosphors plus green-emitting copper- and aluminium-doped zinc sulfide {{chem2|(ZnS:Cu,Al)}}. This is a method analogous to the way [[fluorescent lamp]]s work.

Some newer white LEDs use a yellow and blue emitter in series, to approximate white; this technology is used in some Motorola phones such as the Blackberry as well as LED lighting and the original-version stacked emitters by using GaN on SiC on InGaP but was later found to fracture at higher drive currents.

Many white LEDs used in general lighting systems can be used for data transfer, as, for example, in systems that modulate the LED to act as a [[beacon]].<ref>{{cite journal|url=http://ntv.ifmo.ru/en/article/11192/chastotnye_harakteristiki_sovremennyh_svetodiodnyh_lyuminofornyh_materialov.htm|title=Frequency characteristics of modern LED phosphor materials|author=Fudin, M.S.|journal=Scientific and Technical Journal of Information Technologies, Mechanics and Optics|volume=14|issue=6|page=71|year=2014|display-authors=etal|url-status=live|archive-url=https://web.archive.org/web/20150626162616/http://ntv.ifmo.ru/en/article/11192/chastotnye_harakteristiki_sovremennyh_svetodiodnyh_lyuminofornyh_materialov.htm|archive-date=2015-06-26}}</ref>

It is also common for white LEDs to use phosphors other than Ce:YAG, or to use two or three phosphors to achieve a higher CRI, often at the cost of efficiency. Examples of additional phosphors are R9, which produces a saturated red, nitrides which produce red, and aluminates such as lutetium aluminum garnet that produce green. Silicate phosphors are brighter but fade more quickly, and are used in LCD LED backlights in mobile devices. LED phosphors can be placed directly over the die or made into a dome and placed above the LED: this approach is known as a remote phosphor.<ref>{{Cite web|url=https://www.electronicsweekly.com/news/products/led/discussing-led-lighting-phosphors-2014-03/|title=Discussing LED lighting phosphors|first=Steve|last=Bush|date=March 14, 2014}}</ref> Some colored LEDs, instead of using a colored LED, use a blue LED with a colored phosphor because such an arrangement is more efficient than a colored LED. Oxynitride phosphors can also be used in LEDs. The precursors used to make the phosphors may degrade when exposed to air.<ref>{{cite journal |last1=Setlur |first1=Anant A. |title=Phosphors for LED-based Solid-State Lighting |journal=The Electrochemical Society Interface |date=1 December 2009 |volume=18 |issue=4 |pages=32–36 |doi=10.1149/2.F04094IF |url=https://www.electrochem.org/dl/interface/wtr/wtr09/wtr09_p032-036.pdf |access-date=5 December 2022 |language=en}}</ref>