Editing Light-emitting diode (section)

== Applications ==
[[File:Genesis G90 RS4 Bariloche Brown (11).jpg|thumb| LED-[[Headlight]]s of an automobile]]

LED uses fall into five major categories:

* Visual signals where light goes more or less directly from the source to the human eye, to convey a message or meaning
* [[Lighting|Illumination]] where light is reflected from objects to give visual response of these objects
* Measuring and interacting with processes involving no human vision<ref>[[European Photonics Industry Consortium]] (EPIC). This includes use in data communications over [[Optical fiber|fiber optics]] as well as "broadcast" data or signaling.</ref>
* Narrow band light sensors where [[LEDs as light sensors|LEDs operate in a reverse-bias mode]] and respond to incident light, instead of emitting light<ref>
Mims, Forrest M. III. [http://www.instesre.org/papers/Snowmass/MimsSnowmass.htm "An Inexpensive and Accurate Student Sun Photometer with Light-Emitting Diodes as Spectrally Selective Detectors"].</ref><ref>[https://www.cs.drexel.edu/~dbrooks/globe/special_measurements/water_vapor.htm "Water Vapor Measurements with LED Detectors"]. cs.drexel.edu (2002).</ref><ref>Dziekan, Mike (February 6, 2009) [http://www.soamsci.org/tcs/weeklyIssues_2009/2009-02-06/feature1/index.html "Using Light-Emitting Diodes as Sensors"]. soamsci.or. {{webarchive |url=https://web.archive.org/web/20130531090631/http://www.soamsci.org/tcs/weeklyIssues_2009/2009-02-06/feature1/index.html |date=May 31, 2013 }}</ref><ref>{{Cite book|doi=10.1109/CVPR.2008.4587766|chapter=An LED-only BRDF measurement device|title=2008 IEEE Conference on Computer Vision and Pattern Recognition|pages=1–8|year=2008|last1=Ben-Ezra|first1=Moshe|last2=Wang|first2=Jiaping|last3=Wilburn|first3=Bennett|last4=Xiaoyang Li|last5=Le Ma|isbn=978-1-4244-2242-5|citeseerx=10.1.1.165.484|s2cid=206591080}}</ref>
* Indoor cultivation, including cannabis.<ref>Bantis, Filippos, Sonia Smirnakou, Theoharis Ouzounis, Athanasios Koukounaras, Nikolaos Ntagkas, and Kalliopi Radoglou. "[https://www.plantgrower.org/uploads/6/5/5/4/65545169/1-s2.0-s0304423818301420-main.pdf Current status and recent achievements in the field of horticulture with the use of light-emitting diodes (LEDs).]" Scientia horticulturae 235 (2018): 437-451.</ref>

The application of LEDs in horticulture has revolutionized plant cultivation by providing energy-efficient, customizable lighting solutions that optimize plant growth and development.<ref>Miler N., Kulus D., Woźny A., Rymarz D., Hajzer M., Wierzbowski K., Nelke R., Szeffs L., 2019. Application of wide-spectrum light-emitting diodes in micropropagation of popular ornamental plant species: A study on plant quality and cost reduction. In Vitro Cellular and Developmental Biology – Plant 55: 99-108. https://doi.org/10.1007/s11627-018-9939-5</ref> LEDs offer precise control over light spectra, intensity, and photoperiods, enabling growers to tailor lighting conditions to the specific needs of different plant species and growth stages. This technology enhances photosynthesis, improves crop yields, and reduces energy costs compared to traditional lighting systems. Additionally, LEDs generate less heat, allowing closer placement to plants without risking thermal damage, and contribute to sustainable farming practices by lowering carbon footprints and extending growing seasons in controlled environments.<ref>Tymoszuk A., Kulus D., Błażejewska A., Nadolan K., Kulpińska A., Pietrzykowski K., 2023. Application of wide-spectrum light-emitting diodes in the indoor production of cucumber and tomato seedlings. Acta Agrobotanica 76: 762. https://doi.org/10.5586/aa.762</ref> Light spectrum affects growth, metabolite profile, and resistance against fungal phytopathogens of ''[[Tomato|Solanum lycopersicum]]'' seedlings.<ref>Tymoszuk A., Kulus D., Kowalska J., Kulpińska A., Pańka D., Jeske M., Antkowiak M. 2024. Light spectrum affects growth, metabolite profile, and resistance against fungal phytopathogens of Solanum lycopersicum L. seedlings. Journal of Plant Protection Research 64(2). https://doi.org/10.24425/jppr.2024.150247</ref> LEDs can also be used in [[micropropagation]].<ref>Kulus D., Woźny A., 2020. Influence of light conditions on the morphogenetic and biochemical response of selected ornamental plant species under in vitro conditions: A mini-review. BioTechnologia 101(1): 75-83. http://doi.org/10.5114/bta.2020.92930</ref>

===Indicators and signs===
{{unreferenced section|date=October 2020}}
The [[energy conservation|low energy consumption]], low maintenance and small size of LEDs has led to uses as status indicators and displays on a variety of equipment and installations. Large-area [[LED display]]s are used as stadium displays, dynamic decorative displays, and [[dynamic message sign]]s on freeways. Thin, lightweight message displays are used at airports and railway stations, and as [[Destination sign|destination displays]] for trains, buses, trams, and ferries.

[[File:Red and green traffic signals, Stamford Road, Singapore - 20111210.jpg|thumb|upright|Red and green LED traffic signals]]

One-color light is well suited for [[traffic light]]s and signals, [[exit sign]]s, [[emergency vehicle lighting]], ships' navigation lights, and [[Christmas lighting technology#LEDs|LED-based Christmas lights]]

Because of their long life, fast switching times, and visibility in broad daylight due to their high output and focus, LEDs have been used in automotive brake lights and turn signals. The use in brakes improves safety, due to a great reduction in the time needed to light fully, or faster rise time, about 0.1 second faster{{citation needed|date=April 2016}} than an incandescent bulb. This gives drivers behind more time to react. In a dual intensity circuit (rear markers and brakes) if the LEDs are not pulsed at a fast enough frequency, they can create a [[flicker fusion threshold#Visual phenomena|phantom array]], where ghost images of the LED appear if the eyes quickly scan across the array. White LED headlamps are beginning to appear. Using LEDs has styling advantages because LEDs can form much thinner lights than incandescent lamps with [[parabolic reflector]]s.

Due to the relative cheapness of low output LEDs, they are also used in many temporary uses such as [[glowstick]]s and throwies. Artists have also used LEDs for [[LED art]].

===Lighting===
{{main|LED lamp}}
With the development of high-efficiency and high-power LEDs, it has become possible to use LEDs in lighting and illumination. To encourage the shift to [[LED lamp]]s and other high-efficiency lighting, in 2008 the [[US Department of Energy]] created the [[L Prize]] competition. The [[Philips]] Lighting North America LED bulb won the first competition on August 3, 2011, after successfully completing 18 months of intensive field, lab, and product testing.<ref>{{usurped|1=[https://web.archive.org/web/20080926010013/http://www.lightingprize.org/ "L-Prize U.S. Department of Energy"]}}, L-Prize Website, August 3, 2011</ref>

Efficient lighting is needed for [[sustainable architecture]]. As of 2011, some LED bulbs provide up to 150&nbsp;lm/W and even inexpensive low-end models typically exceed 50&nbsp;lm/W, so that a 6-watt LED could achieve the same results as a standard 40-watt incandescent bulb. The lower heat output of LEDs also reduces demand on [[air conditioning]] systems. Worldwide, LEDs are rapidly adopted to displace less effective sources such as [[incandescent light bulb|incandescent lamps]] and [[compact fluorescent lamp|CFLs]] and reduce electrical energy consumption and its associated emissions. Solar powered LEDs are used as [[street light]]s and in [[Architectural lighting design|architectural lighting]].

The mechanical robustness and long lifetime are used in [[automotive lighting]] on cars, motorcycles, and [[Bicycle lighting#LEDs|bicycle lights]]. [[LED street light]]s are employed on poles and in parking garages. In 2007, the Italian village of [[Torraca]] was the first place to convert its street lighting to LEDs.<ref>[http://www.scientificamerican.com/article.cfm?id=led-there-be-light LED There Be Light], Scientific American, March 18, 2009</ref>

Cabin lighting on recent{{when|date=October 2022}} [[Airbus]] and [[Boeing]] jetliners uses LED lighting. LEDs are also being used in airport and heliport lighting. LED airport fixtures currently include medium-intensity runway lights, runway centerline lights, taxiway centerline and edge lights, guidance signs, and obstruction lighting.

LEDs are also used as a light source for [[Digital Light Processing|DLP]] projectors, and to [[backlight]] newer [[Liquid crystal display|LCD]] television (referred to as [[LED-backlit LCD display|LED TV]]), computer monitor (including [[laptop]]) and handheld device LCDs, succeeding older [[CCFL]]-backlit LCDs although being superseded by [[OLED]] screens. RGB LEDs raise the color gamut by as much as 45%. Screens for TV and computer displays can be made thinner using LEDs for backlighting.<ref>{{cite news|url=https://www.nytimes.com/2007/06/24/business/yourmoney/24novel.html |url-access=subscription |newspaper=New York Times|title=In Pursuit of Perfect TV Color, With L.E.D.'s and Lasers|date=June 24, 2007|first=Anne|last=Eisenberg|access-date=April 4, 2010}}</ref>

LEDs are small, durable and need little power, so they are used in handheld devices such as [[flashlight]]s. LED [[strobe light]]s or [[camera flash]]es operate at a safe, low voltage, instead of the 250+ volts commonly found in [[xenon]] flashlamp-based lighting. This is especially useful in cameras on [[mobile phone]]s, where space is at a premium and bulky voltage-raising circuitry is undesirable.

LEDs are used for infrared illumination in [[night vision]] uses including [[security camera]]s. A ring of LEDs around a [[video camera]], aimed forward into a [[retroreflective]] [[Projection screen|background]], allows [[chroma keying]] in [[video production]]s.

[[File:LED for mines.jpg|thumb|LED for miners, to increase visibility inside mines]]

[[File:Los Angeles Bridge.jpg|thumb|Los Angeles [[Vincent Thomas Bridge]] illuminated with blue LEDs]]

LEDs are used in [[mining]] operations, as [[cap lamp]]s to provide light for miners. Research has been done to improve LEDs for mining, to reduce glare and to increase illumination, reducing risk of injury to the miners.<ref>{{Cite journal | url = https://www.cdc.gov/niosh/docs/2011-192/ | title = CDC – NIOSH Publications and Products – Impact: NIOSH Light-Emitting Diode (LED) Cap Lamp Improves Illumination and Decreases Injury Risk for Underground Miners | publisher = cdc.gov | access-date=May 3, 2013| doi = 10.26616/NIOSHPUB2011192 | year = 2011 | doi-access = free }}</ref>

LEDs are increasingly finding uses in medical and educational applications, for example as mood enhancement.<ref>{{cite news |last=Janeway |first=Kimberly |url=https://www.consumerreports.org/cro/news/2014/12/led-lightbulbs-that-promise-to-help-you-sleep/index.htm |title=LED lightbulbs that promise to help you sleep |work=Consumer Reports |date=2014-12-12 |access-date=2018-05-10}}</ref> [[NASA]] has even sponsored research for the use of LEDs to promote health for astronauts.<ref>{{cite press release | url=http://www.sti.nasa.gov/tto/Spinoff2008/hm_3.html | archive-url=https://web.archive.org/web/20081013083802/http://www.sti.nasa.gov/tto/Spinoff2008/hm_3.html | url-status=dead | archive-date=October 13, 2008 | title=LED Device Illuminates New Path to Healing | publisher=nasa.gov | access-date=January 30, 2012}}</ref>

===Data communication and other signalling===
{{See also|Li-Fi|fibre optics|Visible light communication|Optical disc}}
Light can be used to transmit data and analog signals. For example, lighting white LEDs can be used in systems assisting people to navigate in closed spaces while searching necessary rooms or objects.<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 |author1=Fudin, M. S. |author2=Mynbaev, K. D. |author3=Aifantis, K. E. |author4=Lipsanen H. |author5=Bougrov, V. E. |author6=Romanov, A. E. |journal=Scientific and Technical Journal of Information Technologies, Mechanics and Optics|volume=14|issue=6|year=2014}}</ref>

[[Assistive listening device]]s in many theaters and similar spaces use arrays of infrared LEDs to send sound to listeners' receivers. Light-emitting diodes (as well as semiconductor lasers) are used to send data over many types of [[Optical fiber|fiber optic]] cable, from digital audio over [[TOSLINK]] cables to the very high bandwidth fiber links that form the Internet backbone. For some time, computers were commonly equipped with [[IrDA]] interfaces, which allowed them to send and receive data to nearby machines via infrared.

Because LEDs can [[frequency|cycle on and off]] millions of times per second, very high data bandwidth can be achieved.<ref>{{Cite news|first=Hank |last=Green |url=http://www.ecogeek.org/content/view/2194/74/ |title=Transmitting Data Through LED Light Bulbs |publisher=EcoGeek |date=October 9, 2008 |access-date=February 15, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20081212050729/http://www.ecogeek.org/content/view/2194/74/ |archive-date=December 12, 2008 }}</ref> For that reason, [[visible light communication]] (VLC) has been proposed as an alternative to the increasingly competitive radio bandwidth.<ref name=":4">{{Cite book|last1=Dimitrov|first1=Svilen|url=https://www.cambridge.org/core/books/principles-of-led-light-communications/0528063BAA6863F6B6D61F6FF69F37CB|title=Principles of LED Light Communications: Towards Networked Li-Fi|last2=Haas|first2=Harald|date=2015|publisher=Cambridge University Press|isbn=978-1-107-04942-0|location=Cambridge|doi=10.1017/cbo9781107278929}}</ref> VLC operates in the visible part of the electromagnetic spectrum, so data can be transmitted without occupying the frequencies of radio communications.

=== Machine vision systems ===
{{main|Machine vision}}
[[Machine vision]] systems often require bright and homogeneous illumination, so features of interest are easier to process. LEDs are often used.

[[Barcode scanner]]s are the most common example of machine vision applications, and many of those scanners use red LEDs instead of lasers. Optical computer mice use LEDs as a light source for the miniature camera within the mouse.

LEDs are useful for machine vision because they provide a compact, reliable source of light. LED lamps can be turned on and off to suit the needs of the vision system, and the shape of the beam produced can be tailored to match the system's requirements.

=== Biological detection ===
The discovery of radiative recombination in aluminum gallium nitride (AlGaN) alloys by [[United States Army Research Laboratory|U.S. Army Research Laboratory]] (ARL) led to the conceptualization of UV light-emitting diodes (LEDs) to be incorporated in light-induced [[fluorescence]] sensors used for biological agent detection.<ref>{{Citation |last1=Sampath |first1=A. V. |title=The effects of increasing AlN mole fraction on the performance of AlGaN active regions containing nanometer scale compositionally imhomogeneities |date=2009-12-01 |work=Advanced High Speed Devices |volume=51 |pages=69–76 |series=Selected Topics in Electronics and Systems |publisher=World Scientific |doi=10.1142/9789814287876_0007 |isbn=9789814287869 |last2=Reed |first2=M. L. |last3=Moe |first3=C. |last4=Garrett |first4=G. A. |last5=Readinger |first5=E. D. |last6=Sarney |first6=W. L. |last7=Shen |first7=H. |last8=Wraback |first8=M. |last9=Chua |first9=C.}}</ref><ref name=":1">{{Cite journal |last1=Liao |first1=Yitao |last2=Thomidis |first2=Christos |last3=Kao |first3=Chen-kai |last4=Moustakas |first4=Theodore D. |date=2011-02-21 |title=AlGaN based deep ultraviolet light emitting diodes with high internal quantum efficiency grown by molecular beam epitaxy |journal=Applied Physics Letters |volume=98 |issue=8 |pages=081110 |doi=10.1063/1.3559842 |issn=0003-6951 |bibcode=2011ApPhL..98h1110L |doi-access=free}}</ref><ref name=":2">{{Cite journal |last1=Cabalo |first1=Jerry |last2=DeLucia |first2=Marla |last3=Goad |first3=Aime |last4=Lacis |first4=John |last5=Narayanan |first5=Fiona |last6=Sickenberger |first6=David |date=2008-10-02 |title=Overview of the TAC-BIO detector |journal=Optically Based Biological and Chemical Detection for Defence IV |publisher=International Society for Optics and Photonics |volume=7116 |pages=71160D |doi=10.1117/12.799843 |editor1-last=Carrano |editor1-first=John C. |editor2-last=Zukauskas |editor2-first=Arturas |bibcode=2008SPIE.7116E..0DC |s2cid=108562187}}</ref> In 2004, the [[Edgewood Chemical Biological Center|Edgewood Chemical Biological Center (ECBC)]] initiated the effort to create a biological detector named TAC-BIO. The program capitalized on semiconductor UV optical sources (SUVOS) developed by the [[DARPA|Defense Advanced Research Projects Agency (DARPA)]].<ref name=":2" />

UV-induced fluorescence is one of the most robust techniques used for rapid real-time detection of biological aerosols.<ref name=":2" /> The first UV sensors were lasers lacking in-field-use practicality. In order to address this, DARPA incorporated SUVOS technology to create a low-cost, small, lightweight, low-power device. The TAC-BIO detector's response time was one minute from when it sensed a biological agent. It was also demonstrated that the detector could be operated unattended indoors and outdoors for weeks at a time.<ref name=":2" />

Aerosolized biological particles fluoresce and scatter light under a UV light beam. Observed fluorescence is dependent on the applied wavelength and the biochemical fluorophores within the biological agent. UV induced fluorescence offers a rapid, accurate, efficient and logistically practical way for biological agent detection. This is because the use of UV fluorescence is reagentless, or a process that does not require an added chemical to produce a reaction, with no consumables, or produces no chemical byproducts.<ref name=":2" />

Additionally, TAC-BIO can reliably discriminate between threat and non-threat aerosols. It was claimed to be sensitive enough to detect low concentrations, but not so sensitive that it would cause false positives. The particle-counting algorithm used in the device converted raw data into information by counting the photon pulses per unit of time from the fluorescence and scattering detectors, and comparing the value to a set threshold.<ref>{{Cite journal |last1=Poldmae |first1=Aime |last2=Cabalo |first2=Jerry |last3=De Lucia |first3=Marla |last4=Narayanan |first4=Fiona |last5=Strauch III |first5=Lester |last6=Sickenberger |first6=David |date=2006-09-28 |title=Biological aerosol detection with the tactical biological (TAC-BIO) detector |journal=Optically Based Biological and Chemical Detection for Defence III |volume=6398 |pages=63980E |publisher=SPIE |doi=10.1117/12.687944 |s2cid=136864366 |editor1-last=Carrano |editor1-first=John C. |editor2-last=Zukauskas |editor2-first=Arturas}}</ref>

The original TAC-BIO was introduced in 2010, while the second-generation TAC-BIO GEN&nbsp;II, was designed in 2015 to be more cost-efficient, as plastic parts were used. Its small, light-weight design allows it to be mounted to vehicles, robots, and unmanned aerial vehicles. The second-generation device could also be utilized as an environmental detector to monitor air quality in hospitals, airplanes, or even in households to detect fungus and mold.<ref>{{Cite web |url=https://www.army.mil/article/141363/army_advances_bio_threat_detector |title=Army advances bio-threat detector |website=www.army.mil |date=January 22, 2015 |access-date=2019-10-10}}</ref><ref>{{Cite journal |last1=Kesavan |first1=Jana |last2=Kilper |first2=Gary |last3=Williamson |first3=Mike |last4=Alstadt |first4=Valerie |last5=Dimmock |first5=Anne |last6=Bascom |first6=Rebecca |date=2019-02-01 |title=Laboratory validation and initial field testing of an unobtrusive bioaerosol detector for health care settings |journal=Aerosol and Air Quality Research |volume=19 |issue=2 |pages=331–344 |doi=10.4209/aaqr.2017.10.0371 |issn=1680-8584 |doi-access=free}}</ref>

=== Other applications ===
[[file:LED Costume by Beo Beyond.jpg|thumb|LED costume for stage performers]]
[[file:Digitally printed LED wallpaper Dolomites.jpg |thumb|LED wallpaper by Meystyle]]
[[file:LED screen behind Tsach Zimroni in Tel Aviv Israel.jpg|thumb|A large LED display behind a [[disc jockey]]]]
[[file:LED Digital Display.jpg|thumb|[[Seven-segment display]] that can display four digits and points]]
[[file:LED panel and plants.jpg|thumb|LED panel light source used in an early experiment on [[potato]] growth during Shuttle mission [[STS-73]] to investigate the potential for growing food on future long duration missions]]

The light from LEDs can be modulated very quickly so they are used extensively in [[optical fiber]] and [[free space optics]] communications. This includes [[remote control]]s, such as for television sets, where infrared LEDs are often used. [[Opto-isolator]]s use an LED combined with a [[photodiode]] or [[phototransistor]] to provide a signal path with electrical isolation between two circuits. This is especially useful in medical equipment where the signals from a low-voltage [[sensor]] circuit (usually battery-powered) in contact with a living organism must be electrically isolated from any possible electrical failure in a recording or monitoring device operating at potentially dangerous voltages. An optoisolator also lets information be transferred between circuits that do not share a common ground potential.

Many sensor systems rely on light as the signal source. LEDs are often ideal as a light source due to the requirements of the sensors. The Nintendo [[Wii]]'s sensor bar uses infrared LEDs. [[Pulse oximeter]]s use them for measuring [[oxygen saturation]]. Some flatbed scanners use arrays of RGB LEDs rather than the typical [[cold-cathode fluorescent lamp]] as the light source. Having independent control of three illuminated colors allows the scanner to calibrate itself for more accurate color balance, and there is no need for warm-up. Further, its sensors only need be monochromatic, since at any one time the page being scanned is only lit by one color of light.

Since LEDs can also be used as photodiodes, they can be used for both photo emission and detection. This could be used, for example, in a [[touchscreen]] that registers reflected light from a finger or [[stylus]].<ref>{{cite journal |author1=Dietz, P. H. |author2=Yerazunis, W. S. |author3=Leigh, D. L. |title=Very Low-Cost Sensing and Communication Using Bidirectional LEDs |year=2004 |url=http://www.merl.com/publications/TR2003-035/}}</ref> Many materials and biological systems are sensitive to, or dependent on, light. [[Grow lights]] use LEDs to increase [[photosynthesis]] in [[plant]]s,<ref>{{cite journal |author1=Goins, G. D. |author2=Yorio, N. C. |author3=Sanwo, M. M. |author4=Brown, C. S. |title=Photomorphogenesis, photosynthesis, and seed yield of wheat plants grown under red light-emitting diodes (LEDs) with and without supplemental blue lighting |journal=Journal of Experimental Botany |year=1997 |volume=48 |issue=7 |pages=1407–1413 |doi=10.1093/jxb/48.7.1407 |pmid=11541074|doi-access=free }}</ref> and bacteria and viruses can be removed from water and other substances using UV LEDs for [[Sterilization (microbiology)|sterilization]].<ref name="water sterilization" /> LEDs of certain wavelengths have also been used for [[light therapy]] treatment of [[neonatal jaundice]] and [[acne]].<ref>{{cite book |last1=Li |first1=Jinmin |last2=Wang |first2=Junxi |last3=Yi |first3=Xiaoyan |last4=Liu |first4=Zhiqiang |last5=Wei |first5=Tongbo |last6=Yan |first6=Jianchang |last7=Xue |first7=Bin |title=III-Nitrides Light Emitting Diodes: Technology and Applications |date=31 August 2020 |publisher=Springer Nature |isbn=978-981-15-7949-3 |page=248 |url=https://books.google.com/books?id=Smn6DwAAQBAJ&pg=PA248 |language=en}}</ref>

UV LEDs, with spectra range of 220&nbsp;nm to 395&nbsp;nm, have other applications, such as [[water purification|water]]/[[air purification|air]] purification, surface disinfection, glue curing, free-space [[non-line-of-sight communication]], high performance liquid chromatography, UV curing dye printing, [[phototherapy]] (295nm [[Vitamin D]], 308nm [[Excimer lamp]] or laser replacement), medical/ analytical instrumentation, and DNA absorption.<ref name=":1" /><ref>{{Cite book|last1=Gaska|first1=R.|last2=Shur|first2=M. S.|last3=Zhang|first3=J.|title=2006 8th International Conference on Solid-State and Integrated Circuit Technology Proceedings |chapter=Physics and Applications of Deep UV LEDs |date=October 2006|pages=842–844|doi=10.1109/ICSICT.2006.306525|isbn=1-4244-0160-7|s2cid=17258357}}</ref>

LEDs have also been used as a medium-quality [[voltage reference]] in electronic circuits. The forward voltage drop (about 1.7&nbsp;V for a red LED or 1.2V for an infrared) can be used instead of a [[Zener diode]] in low-voltage regulators. Red LEDs have the flattest I/V curve above the knee. Nitride-based LEDs have a fairly steep I/V curve and are useless for this purpose. Although LED forward voltage is far more current-dependent than a Zener diode, Zener diodes with breakdown voltages below 3&nbsp;V are not widely available.

The progressive miniaturization of low-voltage lighting technology, such as LEDs and OLEDs, suitable to incorporate into low-thickness materials has fostered experimentation in combining light sources and wall covering surfaces for interior walls in the form of [[LED wallpaper]].