View source for Physics:Quantum dot display

{{Short description|Quantum physics topic}}

{{Quantum book backlink|Condensed matter and solid-state physics}}

<div style="display:flex; gap:24px; align-items:flex-start; max-width:1200px;">

<div style="width:280px;">
__TOC__
</div>

<div style="flex:1; line-height:1.45; color:#006b45; column-count:2; column-gap:32px; column-rule:1px solid #b8d8c8;">
{{short description|Type of display device}}

A '''quantum dot display''' is a display device that uses quantum dots (QDs), semiconductor nanocrystals which can produce pure monochromatic{{efn|Up to the specified bandwidth, which is in turn a function of the dispersity of the quantum dots}} red, green, and blue light. 

QDs are either ''photo-emissive'' (photoluminescent) or ''electro-emissive'' (electroluminescent) allowing them to be readily incorporated into new emissive display architectures.<ref name="Nanoco Technologies sub">{{cite web|url=http://www.nanocotechnologies.com/content/CommercialApplications/QDDisplays.aspx|title=Display – Nanoco Technologies|website=www.nanocotechnologies.com|access-date=3 April 2018|archive-url=https://web.archive.org/web/20140323201908/http://www.nanocotechnologies.com/content/CommercialApplications/QDDisplays.aspx|archive-date=23 March 2014}}</ref> Quantum dots naturally produce monochromatic light, so they are more efficient than white light sources when color filtered and allow more saturated colors that reach nearly 100% of Rec. 2020 color gamut.<ref name=creol_rec2020>[https://lcd.creol.ucf.edu/Publications/2015/oe-23-18-23680.pdf Ruidong Zhu, Zhenyue Luo, Haiwei Chen, Yajie Dong, and Shin-Tson Wu. Realizing Rec. 2020 color gamut with quantum dot displays]. Optics Express, Vol. 23, No. 18 (2015).  DOI:10.1364/OE.23.023680</ref><ref name=bul3/><ref name=SID2019tp>{{cite journal|title=Next-Generation Display Technology: Quantum-Dot LEDs|journal=Society for Information Display, Digest of Technical Papers|date=2015-07-29|doi=10.1002/sdtp.10276 |volume=46 |number=1 |pages=73–75 |last1=Manders |first1=J. R. |display-authors=0}}</ref>

As of June 2025, all commercial products, such as LCD TVs branded as ''QLED'', employ quantum dots as ''photo-emissive'' particles; ''electro-emissive'' QD-LED TVs exist in laboratories only.<ref>{{cite web|url=https://english.etnews.com/20161018200003|title=Next Samsung Electronics' QLED TV's Name to Be SUHD QLED TV|last=www.etnews.com|date=2016-10-18|website=etnews.com|access-date=3 April 2018|archive-date=25 June 2018|archive-url=https://web.archive.org/web/20180625185257/http://english.etnews.com/20161018200003|url-status=dead}}</ref><ref>{{cite web|url=https://www.cnet.com/news/how-qled-tv-could-help-samsung-finally-beat-lgs-oleds/|title=How QLED TV could help Samsung finally beat LG's OLEDs|date=30 June 2016|website=cnet.com|access-date=3 April 2018}}</ref> 

LED-backlit LCDs are the main application of photo-emissive quantum dots, though it is applicable to other display technologies that use color filters, such as blue/UV organic light-emitting diode (OLED), MicroLED, or QNED display panels.<ref>{{Cite web|url=https://www.zdnet.com/article/samsung-researching-quantum-dot-on-microled-tvs/|title=Samsung researching quantum dot on MicroLED TVs|first=Cho|last=Mu-Hyun|website=ZDNet}}</ref><ref>{{Cite web|url=https://www.laserfocusworld.com/detectors-imaging/article/16566879/quantum-dots-shrink-microled-pixels-by-87|title=StackPath|website=www.laserfocusworld.com|date=8 January 2019 }}</ref><ref>{{Cite web|url=https://www.eetimes.com/quantum-dots-to-shrink-microled-display-pixels/|title=Quantum Dots to Shrink MicroLED Display Pixels|date=11 January 2019|website=EETimes}}</ref> QD-OLED displays, which use blue OLED panels with QD color filters, started coming to market in 2023.<ref>{{cite web | url=https://www.tomsguide.com/reviews/sony-bravia-xr-a95l-qd-oled-tv | title=Sony Bravia XR A95L QD-OLED TV review | date=9 November 2023 }}</ref> QD-OLED and QD-LED displays can achieve the same contrast as OLED and MicroLED displays with "perfect" black levels in the off state, unlike LED-backlit LCDs.
</div>

<div style="width:300px;">
[[File:QD S.jpg|thumb|280px|Colloidal quantum dots irradiated with an Ultraviolet light. Different sized quantum dots emit different color light due to quantum confinement.]]
</div>

</div>

==Working principle==

The idea of using quantum dots as a light source emerged in the 1990s. Early applications included imaging using QD infrared photodetectors, light emitting diodes and single-color light emitting devices.<ref>{{Cite book|doi=10.1117/12.382121|date=2000|author=R. Victor|author2=K. Irina|chapter=Electron and photon effects in imaging devices utilizing quantum dot infrared photodetectors and light-emitting diodes |editor2-first=Manijeh|editor2-last=Razeghi|editor1-first=Gail J|editor1-last=Brown|title=Photodetectors: Materials and Devices V|volume=3948|pages=206–219|series=Proceedings of SPIE|bibcode=2000SPIE.3948..206R|s2cid=119708221}}</ref> Starting in the early 2000s, scientists started to realize the potential of developing quantum dots for light sources and displays.<ref name=bul>{{Cite journal|date=2009|author=P. Anikeeva|author2=J. Halpert|author3=M. Bawendi|author4=V. Bulovic|title=Quantum dot light-emitting deices with electroluminescence tunable over the entire visible spectrum|volume=9|pmid=19514711|issue=7|pages=2532–2536|journal=Nano Letters|doi=10.1021/nl9002969|bibcode=2009NanoL...9.2532A}}</ref>

''Photo-emissive'' quantum dot particles are used in LCD backlights or display color filters. Quantum dots are excited by the blue light from the display panel to emit pure basic colors, which reduces light losses and color crosstalk in color filters, improving display brightness and color gamut. Light travels through QD layer film and traditional RGB filters made from color pigments or through QD filters with red/green QD color converters and blue passthrough.  

''Electro-emissive'' or ''electroluminescent'' quantum dot displays are an experimental type of display based on quantum-dot light-emitting diodes (QD-LED; also EL-QLED, ELQD, QDEL). These displays are similar to AMOLED and MicroLED screens because each pixel produces its own light when an electric current is applied to tiny inorganic particles. Manufacturers asserted that QD-LED displays could support large, flexible displays and would not degrade as readily as OLEDs, making them good candidates for flat-panel TV screens, digital cameras, mobile phones, and handheld game consoles.<ref name="New_Scientist">[https://www.newscientist.com/article/dn13023-quantumdot-displays-could-outshine-their-rivals/ Quantum-dot displays could outshine their rivals], ''New Scientist'', 10 December 2007</ref><ref name="Evident Technologies sub">{{cite web|url=http://www.evidenttech.com/applications/displays.html|title=Quantum Dot Electroluminescence|website=evidenttech.com|access-date=3 April 2018|archive-url=https://web.archive.org/web/20091216060417/http://www.evidenttech.com/applications/displays.html|archive-date=16 December 2009}}</ref><ref>{{cite web|url=https://www.technologyreview.com/s/405755/nanocrystal-displays/|title=Nanocrystal Displays|first=Kevin|last=Bullis|date=1 May 2006|website=MIT Technology Review|access-date=3 April 2018}}</ref>

==Technology==

[[File:Samsung QLED TV 8K - 75 inches - 2018-11-02.jpg|thumb|Samsung QLED TV 8K - 75 inches]]

===Quantum dot enhancement film===
{{anchor|QDEF|Quantum dot enhancement layer}}
A widespread practical application is using quantum dot enhancement film (QDEF) layer to improve the LED backlighting in LCD TVs. Light from a blue LED backlight is converted by QDs to relatively pure red and green, so that this combination of blue, green and red light incurs less blue-green crosstalk and light absorption in the color filters after the LCD screen, thereby increasing useful light throughput and providing a better color gamut.

The first manufacturer shipping TVs of this kind was Sony in 2013 as ''Triluminos'', Sony's trademark for the technology.<ref>{{Cite web|url=https://blog.sony.com/press/sony-announces-2013-bravia-tvs/|archive-url=https://web.archive.org/web/20130308100416/https://blog.sony.com/press/sony-announces-2013-bravia-tvs/|archive-date=8 March 2013|title=SONY ANNOUNCES 2013 BRAVIA TVS {{pipe}} Sony|date=8 March 2013}}</ref> At the Consumer Electronics Show 2015, Samsung Electronics, TCL Corporation and Sony showed QD-enhanced LED-backlighting of LCD TVs.<ref>{{Cite web|url=https://spectrum.ieee.org/ces-2015-placing-bets-on-the-new-tv-technologies|title=Full Page Reload|website=IEEE Spectrum: Technology, Engineering, and Science News|date=7 January 2015}}</ref><ref>{{cite web|url=http://www.cnet.com/news/lg-leaps-quantum-dot-rivals-with-new-tv/|title=LG leaps quantum dot rivals with new TV|date=16 December 2014|website=cnet.com|access-date=3 April 2018}}</ref><ref>{{cite web|url=https://www.oled-info.com/ultra-slim-lcds-and-quantum-dots-enhanced-leds-enter-market|title=Ultra-slim LCDs and quantum-dots enhanced LEDs enter the market – OLED-Info|website=www.oled-info.com|access-date=3 April 2018}}</ref> At the CES 2017, Samsung rebranded their 'SUHD' TVs as 'QLED'; later in April 2017, Samsung formed the QLED Alliance with Hisense and TCL to produce and market QD-enhanced TVs.<ref name=qled_alliance>{{cite web|url=http://www.flatpanelshd.com/news.php?subaction=showfull&id=1493202792|title=Samsung, Hisense & TCL form 'QLED Alliance' to take on OLED – FlatpanelsHD|website=www.flatpanelshd.com|date=2 April 2017 |access-date=3 April 2018}}</ref><ref>{{cite web|url=http://www.nanosysinc.com/dot-color-archive/2017/4/18/welcome-to-the-qled-era|title=QLED Alliance Kicks Off in Beijing|website=nanosysinc.com|date=18 April 2017|access-date=3 April 2018|archive-date=22 July 2018|archive-url=https://web.archive.org/web/20180722155407/http://www.nanosysinc.com/dot-color-archive/2017/4/18/welcome-to-the-qled-era}}</ref>

Quantum dot on glass (QDOG) replaces QD film with a thin QD layer coated on top of the light-guide plate (LGP), reducing costs and improving efficiency.<ref name="Nanosys_TFUG">{{Cite web |last=Hartlove |first=Jason |title=Quantum Dots Moving to the Mainstream |url=https://nccavs-usergroups.avs.org/wp-content/uploads/TFUG2017/TFUG917-1-Hartlove-Rev1.pdf |archive-url=https://web.archive.org/web/20171223052605/https://nccavs-usergroups.avs.org/wp-content/uploads/TFUG2017/TFUG917-1-Hartlove-Rev1.pdf |archive-date=2017-12-23}}</ref><ref name=DSCC_QDOG>{{cite web|url=https://www.displaysupplychain.com/blog/is-qdog-the-future-of-lcd-tv|title=Is QDOG the Future of LCD TV?|website=Display Supply Chain Consultants|access-date=3 April 2018}}</ref>

Traditional white LED backlights that use blue LEDs with on-chip or on-rail red-green QD structures are being researched since 2010s, though high operating temperatures negatively affect their lifespan.<ref name=pid_samsungdisplay/><ref name=hdtvmagazine_2017>{{cite web|url=http://hdtvmagazine.com/columns/2017/05/hdtv-expert-three-premium-2017-lcdtvs-plot-different-paths-to-enhanced-performance.php|title=HDTV Expert – Three Premium 2017 LCD-TVs Plot Different Paths to Enhanced Performance|first=Shane|last=Sturgeon|website=hdtvmagazine.com|access-date=3 April 2018|archive-date=30 June 2018|archive-url=https://web.archive.org/web/20180630183510/http://www.hdtvmagazine.com/columns/2017/05/hdtv-expert-three-premium-2017-lcdtvs-plot-different-paths-to-enhanced-performance.php}}</ref>

=== Quantum dot color converter ===
{{anchor|Photo-emissive color filters|Quantum dot color converter|QDCF|QDCC|QD-OLED|QNED}}
====LCD====
QD color converter (QDCC) LED-backlit LCDs would use QD film or ink-printed QD layer with red/green sub-pixel patterned (i.e. aligned to precisely match the red and green subpixels) quantum dots to produce pure red/green light; blue subpixels can be transparent to pass through the pure blue LED backlight, or can be made with blue patterned quantum dots in case of UV-LED backlight. This configuration effectively replaces passive color filters, which incur substantial losses by filtering out 2/3 of passing light, with photo-emissive QD structures, improving power efficiency and/or peak brightness, and enhancing color purity.<ref name=pid_samsungdisplay>{{cite web|url=https://pid.samsungdisplay.com/en/learning-center/white-papers/quantum-dot-technology|title=Quantum Dots: Solution for a Wider Color Gamut|website=samsungdisplay.com|access-date=3 April 2018|archive-date=20 September 2018|archive-url=https://web.archive.org/web/20180920111753/https://pid.samsungdisplay.com/en/learning-center/white-papers/quantum-dot-technology}}</ref><ref name=creol_qd_2017/><ref>{{cite web|url=https://www.displaydaily.com/index.php?option=com_content&view=article&id=51888:the-next-step-for-quantum-dots&catid=152:display-daily|title=DisplayDaily|first=Ken|last=Werner|date=2017-05-25|website=www.displaydaily.com|access-date=3 April 2018}}</ref>

Because quantum dots depolarize the light, output polarizer (the analyzer) needs to be moved behind the color converter and embedded in-cell of the LCD glass; this would improve viewing angles as well. In-cell arrangement of the analyzer and/or the polarizer would also reduce depolarization effects in the LC layer, increasing contrast ratio. To reduce self-excitement of QD film and to improve efficiency, the ambient light can be blocked using traditional color filters, and reflective polarizers can direct light from the QDCC towards the viewer. As only blue or UV light passes through the liquid crystal layer, it can be made thinner, resulting in faster pixel response times.<ref name=creol_qd_2017>[https://lcd.creol.ucf.edu/Publications/2017/IEEE%20jstqe-1900611.pdf Haiwei Chen, Juan He, and Shin-Tson Wu. Recent advances on quantum-dot-enhanced liquid crystal displays]. IEEE Journal of Selected Topics in Quantum Electronics Vol. 23, No. 5 (2017). DOI 10.1109/JSTQE.2017.2649466</ref><ref name=creol_depol_2017>[https://lcd.creol.ucf.edu/Publications/2017/oe-25-10-11315.pdf H. Chen, G. Tan, M. C. Li, S. L. Lee, and S. T. Wu. Depolarization effect in liquid crystal displays]. Optics Express 25 (10), 11315-11328 (2017). DOI 10.1364/OE.25.011315</ref>

Nanosys made presentations of their photo-emissive color converter technology during 2017; commercial products were expected by 2019, though in-cell polarizer remained a major challenge.<ref>{{cite web|url=http://www.avsforum.com/nanosys-quantum-dots-at-ces-2017/|title=Nanosys Quantum Dots at CES 2017 - AVSForum.com|date=12 January 2017|website=avsforum.com|access-date=3 April 2018}}</ref><ref name=qled_alliance/><ref>{{cite web|url=https://www.insightmedia.info/nanosys-details-the-future-of-quantum-dots/|title=Nanosys Details the Future of Quantum Dots|website=www.insightmedia.info|date=19 June 2017 |access-date=3 April 2018}}</ref><ref>{{cite web|url=http://www.nanosysinc.com/dot-color-archive/2017/6/14/sid-display-week-2017-overlook|title=SID Display Week 2017 – Thank You!|website=nanosysinc.com|access-date=3 April 2018|archive-date=20 September 2018|archive-url=https://web.archive.org/web/20180920114548/http://www.nanosysinc.com/dot-color-archive/2017/6/14/sid-display-week-2017-overlook}}</ref><ref>{{cite web|url=https://www.printedelectronicsnow.com/contents/view_online-exclusives/2017-06-14/nanosys-honored-for-hyperion-quantum-dot-technology-at-display-week/|title=Nanosys Honored for Hyperion Quantum Dot Technology at Display Week|website=printedelectronicsnow.com|access-date=3 April 2018|archive-date=25 June 2018|archive-url=https://web.archive.org/web/20180625161022/https://www.printedelectronicsnow.com/contents/view_online-exclusives/2017-06-14/nanosys-honored-for-hyperion-quantum-dot-technology-at-display-week/}}</ref><ref name=nanosys_inkjet_2017>{{cite web|url=https://www.displaydaily.com/article/display-daily/beginning-of-the-end-for-the-color-matrix-filter|title=Beginning of the End for the Color Matrix Filter?|first=Ken|last=Werner|date=2017-12-07|website=www.displaydaily.com|access-date=3 April 2018}}</ref><ref name=qd_forum_2018>{{cite web|url=https://www.displaydaily.com/article/display-daily/what-s-next-for-quantum-dots|title=What's Next for Quantum Dots?|first=Peter|last=Palomaki|date=2018-04-05|website=www.displaydaily.com}}</ref><ref name=qd_future_2018>{{cite web|url=https://www.displaydaily.com/article/display-daily/future-of-quantum-dot-display-niche-or-mainstream|title=Future of Quantum Dot Display: Niche or Mainstream?|first=Sweta|last=Dash|date=2018-05-07|website=www.displaydaily.com}}</ref><ref name=nanosys_ces2018/> As of December 2019, issues with in-cell polarizer remained unresolved and no LCDs with QD color converter appeared on the market since then.<ref>{{Cite web | url=https://www.displaydaily.com/article/display-daily/top-trends-in-quantum-dots-at-sid-display-week-2019-part-1 |title = Top Trends in Quantum Dots at SID Display Week 2019 – Part 1|date = 17 June 2019}}</ref>

====QD-OLED====

QD color converters can be used with OLED or micro-LED panels, improving their efficiency and color gamut.<ref name=Nanosys_TFUG/><ref name=nanosys_ces2018/><ref name=Samsung_QD-OLED>{{Cite web | url=https://www.displaysupplychain.com/blog/oled-materials-report-brings-new-insight-on-qd-oleds | title=OLED Materials Report Brings New Insight on QD OLEDs}}</ref><ref name=etnews-QD-OLED>{{Cite web | url=https://www.oled-info.com/etnews-sdc-building-qd-oled-tv-pilot-production-line | title=ETNews: SDC is building a QD-OLED TV pilot production line {{pipe}} OLED-Info}}</ref> QD-OLED panels with blue emitters and red-green color converters have been researched by Samsung and TCL.<ref name=Samsung_IMID2018>{{Cite web | url=https://www.flatpanelshd.com/news.php?subaction=showfull&id=1540893960 | title=Samsung: We are developing QD-OLED displays – FlatpanelsHD| date=2 October 2018}}</ref><ref>{{Cite web | url=https://www.displaydaily.com/article/display-daily/samsung-display-accelerating-plans-to-shift-to-qd-oled | title=Samsung Display Accelerating Plans to Shift to QD OLED| date=November 2018}}</ref><ref>{{Cite web | url=https://www.oled-info.com/more-details-emerge-samsungs-qd-oled-tv-plans | title=More details emerge on Samsung's QD-OLED TV Plans {{pipe}} OLED-Info}}</ref><ref>{{Cite web |url=http://informationdisplay.org/id-archive/2018/november-december/frontlinetechnologyanewfrontier/elq_mid/32390/elq_cid/10298534 |title=InformationDisplay > ID Archive > 2018 > November/December > FrontlineTechnologyANewFrontier |access-date=1 January 2019 |archive-date=2 January 2019 |archive-url=https://web.archive.org/web/20190102094512/http://informationdisplay.org/id-archive/2018/november-december/frontlinetechnologyanewfrontier/elq_mid/32390/elq_cid/10298534 }}</ref><ref>{{Cite web | url=https://www.oled-info.com/tcl-developing-hybrid-qd-oled-display-technology |title = TCL is developing hybrid QD-OLED display technology {{pipe}} OLED-Info}}</ref><ref>{{Cite web|url=https://www.koreaherald.com/view.php?ud=20190818000183|title=Samsung Display CEO affirms QD-OLED efforts|first=The Korea|last=Herald|date=18 August 2019|website=www.koreaherald.com}}</ref> In October 2019, Samsung Display announced an investment of $10.8 billion in both research and production, with the aim to convert all their 8G panel factories to QD-OLED production during 2019–2025.<ref>{{Cite web | url=https://www.oled-info.com/samsung-display-formally-announces-its-108-billion-investment-qd-oled-tv |title = Samsung Display formally announces its $10.8 billion investment in QD-OLED TV production {{pipe}} OLED-Info}}</ref><ref>{{Cite web|url=https://www.electronicsweekly.com/news/business/samsung-put-11bn-qd-oled-2019-10/|title=Samsung to put $11bn into QD-OLED|first=David|last=Manners|date=11 October 2019}}</ref><ref>{{Cite web | url=https://www.displaydaily.com/article/display-daily/top-trends-in-quantum-dots-at-sid-display-week-2019-part-2 |title = Top Trends in Quantum Dots at SID Display Week 2019 – Part 2|date = 26 June 2019}}</ref><ref name=beyond_qd-oled>{{Cite web | url=https://displaydaily.com/article/display-daily/samsung-looking-beyond-qd-oled |title = Samsung Looking Beyond QD OLED|date = 28 November 2019}}</ref> Samsung Display presented 55" and 65" QD-OLED panels at CES 2022, with TVs from Samsung Electronics and Sony to be released later in 2022.<ref>{{cite web | url=https://www.cnet.com/tech/home-entertainment/samsung-qd-oled-tv-tech-explained-welcome-quantum-dot-era/ | title=Samsung says its new quantum dot TV tech boosts image quality over regular OLED displays }}</ref>

QD-OLED displays show better color volume, covering 90% of Rec.2020 color gamut with peak brightness of 1500 nits, while current OLED and LCD TVs cover 70–75% of Rec.2020 (95–100% of DCI-P3).<ref name=TheVerge_QD-OLED_gamut>{{cite web | url=https://www.theverge.com/2022/1/10/22876061/samsung-qd-oled-quantum-dot-tv-panels-sgs-certification-brightness-color-viewing-angles | title=Samsung Display's new QD-OLED panel can hit 1,000 nits brightness for improved HDR | date=10 January 2022 }}</ref><ref name=SGS_QD-Display>{{cite web | url=https://www.samsungdisplay.com/eng/media/news/detail/ssdsNews-220110.jsp | title=[Press Release] Samsung QD-Display Globally Certified by SGS for Outstanding Picture Quality }}</ref><ref name=RTings_Rec2020_gamut>{{cite web | url=https://www.rtings.com/tv/tests/picture-quality/wide-color-gamut-rec-709-dci-p3-rec-2020 | title=Our TV Picture Quality Tests: Color Gamut }}</ref>

==== QNED ====

A further development of QD-OLED displays is quantum dot nanorod emitting diode (QNED) display<ref name=sammobile-qned2021/> which replaces blue OLED layer with InGaN/GaN blue nanorod LEDs. Nanorods have a larger emitting surface compared to planar LED, allowing increased efficiency and higher light emission. Nanorod solution is ink-printed on the substrate, then subpixels are aligned in-place by electric current, and QD color converters are placed on top of red/green subpixels.<ref>{{Cite web|url=https://www.displaydaily.com/article/display-daily/are-quantum-nano-emitting-diodes-qneds-the-next-big-thing|title=Are Quantum Nano Emitting Diodes (QNEDs) the Next Big Thing?|date=8 April 2020}}</ref><ref>{{Cite web|url=https://www.displaysupplychain.com/blog/are-quantum-nano-emitting-diodes-qneds-the-next-big-thing|title = Are Quantum Nano Emitting Diodes (QNEDs) the Next Big Thing? - Display Supply Chain Consultants}}</ref> Samsung Display was expected to begin test production of QNED panels in 2021,<ref name=sammobils-qned>{{Cite web|url=https://www.sammobile.com/news/samsung-revolutionary-qned-tech-mass-production-ready-report|title = Samsung's revolutionary QNED tech ready for mass production: Report| date=16 November 2020 }}</ref>
<ref name=sammobile-qned2021>{{cite web | url=https://www.sammobile.com/news/samsung-quantum-dot-successor-qned-production-2021/ | title=Samsung's Quantum Dot successor, QNED, could enter production in 2021 | date=16 July 2020 }}</ref> with mass production in 2024–2025, but test production has been postponed as of May 2022.<ref>{{cite web | url=https://www.thelec.net/news/articleView.html?idxno=4032 | title=Samsung Display delays installment of pilot line for QNED | date=12 May 2022 }}</ref><ref>{{cite web | url=https://www.channelnews.com.au/new-samsung-lg-premium-display-war-nanorod-qled-tipped-to-be-superior-to-oled/ | title=Channelnews: New Samsung LG Premium Display War, Nanorod QLED Tipped to be Superior to OLED }}</ref>

====microLED====
{{anchor|QD-OLED/microLED}}
An QD chip-on-board (QD-COB) color conversion layer can be applied to microLED microdisplays commonly used in near-eye devices such as augmented reality (AR) glasses and micro projectors. Two main color conversion technologies have been developed: one embeds quantum dots in nanoporous GaN on blue LEDs (e.g., Nanopore Quantum Dot, or NPQD), and the other uses patterned quantum dot photoresist layers over the microLED array. These approaches enable extremely high pixel densities and sufficient brightness for compact full-color displays.<ref>{{Cite journal | last1 = Song | first1 = Jie | last2 = Chen | first2 = Chen | title = Nano-porous GaN enhances microLEDs | journal = Compound Semiconductor Magazine | volume = 27 | date = January 2021 | pages = 36–39 | url = https://compoundsemiconductor.net/article/113700/Nano-porous_GaN_Enhances_MicroLEDs }}</ref><ref>{{Cite journal
| last1 = Wu| first1 = Tingzhu| last2 = Huang| first2 = Yu-Ming| last3 = Konthoujam| first3 = James Singh| last4 = Chen| first4 = Zhong| last5 = Kuo| first5 = Hao-Chung| editor1-last = Jiang| editor1-first = Hongxing| editor2-last = Lin| editor2-first = Jingyu| title = Chapter Five - Quantum-dot-based full-color micro-LED displays| journal = Semiconductors and Semimetals| volume = 106| year = 2021| pages = 173–201| issn = 0080-8784| isbn = 978-0-12-823041-1
| doi = 10.1016/bs.semsem.2021.01.005| url = https://www.sciencedirect.com/science/article/pii/S0080878421000053 | url-access = subscription}}</ref> The NPQD process creates an in-situ nanoporous layer on a GaN microLED wafer, which is filled with quantum dots to convert blue emission into red or green light, enabling monolithic full-color displays with improved brightness, efficiency, and reliability.<ref>{{Cite web | title = Saphlux Debuts Full-Color MicroLED with NPQD Technology | website = Photonics Media | date = 2023-08-23 | url = https://www.photonics.com/Articles/Saphlux_Debuts_Full-Color_MicroLED/a69045 | access-date = 2025-04-03}}</ref> By replacing conventional AlInGaP-based red light-emitting chips—which differ in material composition from green and blue InGaN chips—with quantum dot-converted red subpixels, QD-COB displays demonstrate improved color consistency across a range of viewing angles.<ref>{{cite web|url=https://www.microled-info.com/leyard-starts-producing-microled-displays-saphluxs-qd-color-conversion|title=Leyard starts producing MicroLED displays with Saphlux's QD color conversion tech|date=2013-10-12|website=microled-info.com|access-date=3 April 2025}}</ref><ref>{{cite web|url=https://www.minimicroled.com/quantum-dot-displays-cob-2-0-era-saphlux|title=Quantum Dot Displays Enter the COB 2.0 Era with Saphlux Technology|date=27 Feb 2024|website=minimicroled.com|access-date=3 April 2025}}</ref> Commercial 0.22-inch microLED displays with a QD-COB layer were released in 2023-2024, with 0.39-inch and a 0.13-inch versions targeting pilot production in 2025.<ref>{{cite web|url=https://www.businesswire.com/news/home/20230817243001/en|title=Saphlux Unveils Revolutionary Full-Color NPQD Microdisplay for AR/VR Headsets|date=17 Aug 2023|website=businesswire.com|access-date=3 April 2025}}</ref><ref>{{cite web|url=https://www.ledinside.com/news/2025/3/2025_03_07_02|title=MicroLED Display Advancements and the Rise of NPQD Technology|date=27 Mar 2025|website=ledinside.com|access-date=3 April 2025}}</ref><ref>{{Cite web | title = Saphlux Launches QD-COB Mini/MicroLED Display with NPQD Red Chip | website = LEDinside | date = Mar 2024 | url = https://www.ledinside.com/news/2024/3/saphlux_qd-cob_release | access-date = 2025-04-03 }} </ref><ref>{{Cite web| title = QD-COB Pro Series: Saphlux Unveils Pro-Design Level Quantum Dot COB Display Solution| website = LEDinside| date = 2025-03-07| url = https://www.ledinside.com/news/2025/3/2025_03_07_02| access-date = 2025-04-03
}}</ref><ref>{{Cite web | title = Saphlux Introduces Nanopore MicroLEDs for Outdoor AR/VR Applications | website = Display Daily | date = 2024-03-26 | url = https://displaydaily.com/saphlux-introduces-nanopore-microleds-for-outdoor-ar-vr-applications/ | access-date = 2025-04-03 }}</ref>

Additional experimental methods, such as inkjet printing of QD inks, are also under investigation for micron-scale integration.

===Self-emissive quantum dot diodes ===
{{Anchor|EL-QLED|ELQD|QDEL}}
Self-emissive quantum dot displays will use electroluminescent QD nanoparticles functioning as Quantum-dot-based LEDs (QD-LED) arranged in either active matrix or passive matrix array. Rather than requiring a separate LED backlight for illumination and TFT LCD to control the brightness of color primaries, these QDEL displays would natively control the light emitted by individual color subpixels,<ref>{{cite web|url=http://www.trustedreviews.com/opinions/what-is-qled-the-future-of-tv-tech-explained#s3WOjf6fzwFBPchs.99|title=What is QLED? Demystifying the future of TV tech – Trusted Reviews|date=9 June 2016|website=trustedreviews.com|access-date=3 April 2018|archive-date=11 July 2017|archive-url=https://web.archive.org/web/20170711114340/http://www.trustedreviews.com/opinions/what-is-qled-the-future-of-tv-tech-explained#s3WOjf6fzwFBPchs.99}}</ref> greatly reducing pixel response times by eliminating the liquid crystal layer. This technology has also been called true QLED display,<ref name="Palomaki 2018">{{cite web | last=Palomaki | first=Peter | title=What's Next for Quantum Dots? | website=DisplayDaily | date=2018-04-05 | url=https://www.displaydaily.com/article/display-daily/what-s-next-for-quantum-dots | access-date=2019-01-14 | archive-date=4 December 2023 | archive-url=https://web.archive.org/web/20231204025109/https://displaydaily.com/what-s-next-for-quantum-dots/ }}</ref> and electroluminescent quantum dots (ELQD, QDEL, EL-QLED).<ref name="Johnson 2017">{{cite web | last=Johnson | first=Dexter | title=Nanosys Wants Printing Quantum Dot Displays to be as Cheap as Printing a T-Shirt | website=IEEE Spectrum: Technology, Engineering, and Science News | date=2017-11-21 | url=https://spectrum.ieee.org/printing-quantum-dot-displays-could-be-as-cheap-as-printing-a-tshirt | access-date=2019-01-14}}</ref><ref name="Samsung Display PID 2018">{{cite web | title=Peter Palomaki: The Evolution of Quantum Dot Technology | website=Samsung Display PID | date=2018-05-24 | url=https://pid.samsungdisplay.com/en/learning-center/blog/palomaki-on-the-evolution-of-quantum-dot-technology | access-date=2019-01-14 | archive-date=14 January 2019 | archive-url=https://web.archive.org/web/20190114153330/https://pid.samsungdisplay.com/en/learning-center/blog/palomaki-on-the-evolution-of-quantum-dot-technology }}</ref> 

The structure of a QD-LED is similar to the basic design of an OLED. The major difference is that the light emitting devices are quantum dots, such as cadmium selenide (CdSe) nanocrystals. A layer of quantum dots is sandwiched between layers of electron-transporting and hole-transporting organic materials. An applied electric field causes electrons and holes to move into the quantum dot layer, where they are captured in the quantum dot and recombine, emitting photons.<ref name=bul/><ref>{{Cite journal|date=2002|author=Seth Coe|author2=Wing-Keung Woo|author3=Moungi Bawendi|author4=Vladimir Bulovic|title=Electroluminescence from single monolayers of nanocrystals in molecular organic devices|volume=420|pmid=12490945|issue=6917|pages=800–803|journal=Nature|doi=10.1038/nature01217|bibcode=2002Natur.420..800C|s2cid=4426602}}</ref> The demonstrated color gamut from QD-LEDs exceeds the performance of both LCD and OLED display technologies.<ref name=creol_rec2020/><ref name=bul3/><ref name=SID2019tp/> To realize all-QD LED, the challenge that should be overcome is the currently poor electrical conduction in the emitting QD layers.<ref>{{Cite journal |last1=Kim |first1=Jaehoon |last2=Roh |first2=Jeongkyun |last3=Park |first3=Myoungjin |last4=Lee |first4=Changhee |date=2023-02-28 |title=Recent Advances and Challenges of Colloidal Quantum Dot Light-Emitting Diodes for Display Applications |url=https://onlinelibrary.wiley.com/doi/10.1002/adma.202212220 |journal=Advanced Materials |volume=36 |issue=20 |language=en |article-number=2212220 |doi=10.1002/adma.202212220 |pmid=36853911 |s2cid=257231945 |issn=0935-9648|url-access=subscription }}</ref><ref>{{Cite journal |last1=Septianto |first1=Ricky Dwi |last2=Miranti |first2=Retno |last3=Kikitsu |first3=Tomoka |last4=Hikima |first4=Takaaki |last5=Hashizume |first5=Daisuke |last6=Matsushita |first6=Nobuhiro |last7=Iwasa |first7=Yoshihiro |last8=Bisri |first8=Satria Zulkarnaen |date=2023-05-26 |title=Enabling metallic behaviour in two-dimensional superlattice of semiconductor colloidal quantum dots |journal=Nature Communications |language=en |volume=14 |issue=1 |page=2670 |doi=10.1038/s41467-023-38216-y |pmid=37236922 |pmc=10220219 |bibcode=2023NatCo..14.2670S |issn=2041-1723}}</ref>

As cadmium-based materials cannot be used in lighting applications due to their environmental impact,<ref>{{Cite web|url=https://www.koreaherald.com/view.php?ud=20141118000897|title=Quantum dot is no game changer: Merck|first=The Korea|last=Herald|date=18 November 2014|website=www.koreaherald.com}}</ref> InP (indium phosphide) ink-jet solutions are being researched by Nanosys, Nanoco, Nanophotonica, OSRAM OLED, Fraunhofer IAP, Merck, and Seoul National University, among others.<ref name=qd_forum_2018/><ref name=merck_inkjet_qd_2017>{{cite web|url=https://www.oled-info.com/merck-leads-new-consortium-develop-quantum-materials-light-emission|title=Merck leads a new consortium to develop quantum materials for light emission – OLED-Info|website=www.oled-info.com}}</ref><ref>{{cite web|url=https://www.displaydaily.com/article/display-daily/germany-pushing-the-boundaries-of-el-qled-with-consortium|title=Germany Pushing the Boundaries of EL QLED with Consortium|first=Peter|last=Palomaki|date=2018-09-17|website=www.displaydaily.com}}</ref> As of 2019, InP based materials are still not yet ready for commercial production due to limited lifetime.<ref>{{Cite web|url=https://displaydaily.com/article/display-daily/bright-long-lasting-cd-free-what-else-could-you-want-from-el-qled|title=Bright. Long Lasting. Cd-Free. What Else Could You Want from EL-QLED?|first=Peter|last=Palomaki|date=23 December 2019|website=DisplayDaily}}</ref>

Mass production of active-matrix QLED displays using ink-jet printing was expected to begin in 2020–2021,<ref name=digitimes_qled>{{cite web|url=https://www.digitimes.com/news/a20161031PD203.html|title=Digitimes Research: Samsung Electronics developing QD technology toward QLED|first=Jessie Lin, DIGITIMES Research|last=Taipei|website=digitimes.com|date=7 November 2016 |access-date=3 April 2018}}</ref><ref>{{cite web|url=https://www.oled-info.com/cpt-aims-start-mass-producing-qd-led-displays-within-2-years|title=CPT aims to start mass producing QD-LED displays within 2 years – OLED-Info|website=www.oled-info.com|access-date=3 April 2018}}</ref><ref>{{cite web|url=https://www.oled-info.com/digitimes-research-samsung-will-begin-qled-tv-production-2019|title=Digitimes Research: Samsung will begin QLED TV production in 2019 – OLED-Info|website=www.oled-info.com|access-date=3 April 2018}}</ref><ref name=qd_future_2018/><ref name=nanosys_ces2018>{{cite web|url=https://www.avsforum.com/nanosys-quantum-dot-update-ces-2018/|title=Nanosys Quantum-Dot Update at CES 2018 - AVSForum.com|date=20 January 2018|website=avsforum.com}}</ref> but as of 2024, longevity issues are not resolved and the technology remains in prototyping stage. In 2024, Nanosys assumed their QD electroluminescent technology to be available for production by 2026,<ref name=ars-technica-meet-qdel>{{cite web|url=https://arstechnica.com/gadgets/2024/04/meet-qdel-the-backlight-less-display-tech-that-could-replace-oled-in-premium-tvs/|title=Meet QDEL, the backlight-less display tech that could replace OLED in premium TVs|first=Scharon |last=Harding| date=April 22, 2024|website=[[Ars Technica]]|access-date=2024-01-05}}</ref> and in 2026, to appear by 2029.<ref name=nanoled2029>{{cite web | title=Nanosys: Brighter QD-OLEDs in 2026, NanoLED (QDEL) by 2029 | date=2 January 2026 | url=https://www.flatpanelshd.com/news.php?subaction=showfull&id=1768388916 }}</ref> 

At CES 2024, Sharp NEC Display privately demonstrated prototypes of 12" and 30" display panels.<ref name=digitaltrends-sharp-qdel>{{cite web|url=https://www.digitaltrends.com/home-theater/sharp-qdel-tv-ces-2024/|title=Sharp secretly revealed the first QDEL TV at CES|first=Simon|last=Cohen|date=January 15, 2024|website=[[Company:Digital Trends|Digital Trends]]|access-date=2024-05-01}}</ref><ref name=ars-technica-meet-qdel/>

==Commercial products==

A variety of brands sell displays that combine an LED-backlit LCD with a quantum dot film to improve color and contrast compared to regular LED-backlit displays.<ref>{{cite web |last1=Bizzaco |first1=Michael |last2=Cohen |first2=Simon |date=25 March 2025 |title=QLED vs. OLED TVs: which is better and what's the difference? |url=https://www.digitaltrends.com/home-theater/qled-vs-oled-tv/ |publisher=Digital Trends Media Group |access-date=22 December 2025}}</ref> Sony promotes their QD-enhanced products as ''Triluminos''.<ref>{{cite web |last=Turner |first=Adam |date=13 July 2025 |title=Hands on review: Sony Triluminos Full Array Ultra HD TV television |url=https://www.smh.com.au/technology/hands-on-review-sony-triluminos-full-array-ultra-hd-tv-television-20150712-giamzz.html |website=The Sydney Morning Herald |access-date=22 December 2025}}</ref> Samsung promotes their QD products as ''QLED''<ref>{{cite web |last=Katzmaier |first=David |date=26 September 2025 |title=QLED vs. OLED: What's Better? |url=https://www.cnet.com/tech/home-entertainment/qled-vs-oled-whats-better/ |website=CNet |access-date=22 December 2025}}</ref> and has allowed Hisense and TCL to promote theirs in the same way.<ref name="qled_alliance" /> Starting in 2021 LG Electronics introduced a series of TVs branded as "QNED Mini LED". These TVs are based on LCD displays with mini LED backlighting and don't use self-emissive technologies.<ref>{{cite web |last1=Abella |first1=Reycarlo |title=What Is QNED Explained: How It Compares To QLED & OLED |url=https://screenrant.com/qned-qled-oled-tv-display-explained-comparison/ |website=ScreenRant |access-date=28 December 2023 |date=24 February 2023}}</ref>

Some brands, such as Samsung, sell QD-OLED displays that combine an OLED panel with Quantum dot color converters to improve color and brightness compared to regular OLED displays; these typically use blue OLED layers instead of RGB or RGBW.<ref>{{cite web |last=Slater-Robins |first=Max |date=10 February 2025 |title=What is QD-OLED? The hybrid OLED TV tech explained |url=https://www.techradar.com/televisions/what-is-qd-oled-the-hybrid-oled-tv-tech-explained |website=TechRadar |access-date=22 December 2025}}</ref><ref>{{cite web |last=Willcox |first=James K. |date=22 November 2025 |title=QLED vs. OLED (and QD-OLED): Which TV Tech Is Right for You? |url=https://www.consumerreports.org/electronics-computers/tvs/qled-vs-oled-and-qd-oled-which-tv-tech-is-right-for-you-a6691090566/ |publisher=Consumer Reports |access-date=22 December 2025}}</ref>

Tests commissioned in 2024 by Hansol, a supplier for Samsung Electronics, suggest that several TCL models marketed as containing quantum dots do not actually contain quantum dot materials. However, news outlets warn readers to be skeptical of Hansol's claims due to their ties with one of TCL's competitors.<ref>{{cite news |last=Harding |first=Scharon |date=18 September 2024 |title=TCL accused of selling quantum dot TVs without actual quantum dots |url=https://arstechnica.com/gadgets/2024/09/tcl-accused-of-selling-quantum-dot-tvs-without-actual-quantum-dots/ |website=Ars Technica |access-date=22 December 2025}}</ref><ref>{{cite news |date=24 September 2024 |title=TCL QLED TVs Under Scrutiny: Are Quantum Dots Actually Present? |url=https://hometheaterreview.com/tcl-qled-tvs-under-scrutiny-are-quantum-dots-actually-present/ |website=Home Theatre Review |access-date=22 December 2025}}</ref> In March 2026, Samsung Electronics' law firm Pinsent Masons stated that it had won a misleading-advertising case against TCL Deutschland before the Landgericht München I concerning TCL televisions advertised as "QLED". According to the firm, the court barred TCL from continuing to market the challenged models from six series as "QLED" and ordered it to correct the statements; the judgment was not yet final.<ref>{{cite web |title=Pinsent Masons gewinnt für Samsung Electronics Rechtstreit gegen TCL wegen irreführender Werbung |url=https://www.pinsentmasons.com/de-de/ueber-uns/presse/pinsent-masons-gewinnt-fur-samsung-electronics-rechtstreit-gegen-tcl-wegen-irrefuhrender-werbung |website=Pinsent Masons |language=de |access-date=26 March 2026}}</ref>

==Optical properties of quantum dots==
Performance of QDs is determined by the size and/or composition of the QD structures. Unlike simple atomic structures, a quantum dot structure has the unusual property that energy levels are strongly dependent on the structure's size. For example, CdSe quantum dot light emission can be tuned from red (5&nbsp;nm diameter) to the violet region (1.5&nbsp;nm dot). The physical reason for QD coloration is the quantum confinement effect and is directly related to their energy levels. The bandgap energy that determines the energy (and hence color) of the fluorescent light is inversely proportional to the square of the size of quantum dot. Larger QDs have more energy levels that are more closely spaced, allowing the QD to emit (or absorb) photons of lower energy (redder color). In other words, the emitted photon energy increases as the dot size decreases, because greater energy is required to confine the semiconductor excitation to a smaller volume.<ref>{{cite book|first1=Bahaa E. A. |last1=Saleh|first2=Malvin Carl |last2=Teich|title=Fundamentals of Photonics|url=|date=5 February 2013|publisher=Wiley|isbn=978-1-118-58581-8 |page=498}}</ref>

Newer quantum dot structures employ indium instead of cadmium, as the latter is not exempted for use in lighting by the European Commission RoHS directive,<ref name=pid_samsungdisplay/><ref>{{cite web|url=http://optics.org/news/7/6/8|title=EU report sends mixed message on cadmium quantum dots|first=SPIE Europe|last=Ltd|website=optics.org|access-date=3 April 2018}}</ref> and also because of cadmium's toxicity.

QD-LEDs are characterized by pure and saturated emission colors with narrow bandwidth, with FWHM (full width at half maximum) in the range of 20–40&nbsp;nm.<ref name=bul/><ref name=creol_qd_2017/> Their emission wavelength is easily tuned by changing the size of the quantum dots. Moreover, QD-LED offer high color purity and durability combined with the efficiency, flexibility, and low processing cost of comparable organic light-emitting devices. QD-LED structure can be tuned over the entire visible wavelength range from 460&nbsp;nm (blue) to 650&nbsp;nm (red) (the human eye can detect light from 380 to 750&nbsp;nm). The emission wavelengths have been continuously extended to UV and NIR range by tailoring the chemical composition of the QDs and device structure.<ref>{{Cite journal|last1=Kwak|first1=Jeonghun|last2=Lim|first2=Jaehoon|last3=Park|first3=Myeongjin|last4=Lee|first4=Seonghoon|last5=Char|first5=Kookheon|last6=Lee|first6=Changhee|date=2015-06-10|title=High-Power Genuine Ultraviolet Light-Emitting Diodes Based On Colloidal Nanocrystal Quantum Dots|journal=Nano Letters|volume=15|issue=6|pages=3793–3799|doi=10.1021/acs.nanolett.5b00392|issn=1530-6984|pmid=25961530|bibcode=2015NanoL..15.3793K}}</ref><ref>{{Cite journal|last1=Supran|first1=Geoffrey J.|last2=Song|first2=Katherine W.|last3=Hwang|first3=Gyu Weon|last4=Correa|first4=Raoul E.|last5=Scherer|first5=Jennifer|last6=Dauler|first6=Eric A.|last7=Shirasaki|first7=Yasuhiro|last8=Bawendi|first8=Moungi G.|last9=Bulović|first9=Vladimir|date=2015-02-01|title=High-Performance Shortwave-Infrared Light-Emitting Devices Using Core–Shell (PbS–CdS) Colloidal Quantum Dots|journal=Advanced Materials|language=en|volume=27|issue=8|pages=1437–1442|doi=10.1002/adma.201404636|pmid=25639896|bibcode=2015AdM....27.1437S |s2cid=205258576|issn=1521-4095|doi-access=free}}</ref>

==Fabrication process==

Quantum dots are solution processable and suitable for wet processing techniques. The two major fabrication techniques for QD-LED are called phase separation and contact-printing.<ref name=bul2>{{Cite book|date=2005|display-authors=4|author=Coe-Sullivan, Seth|author2=Steckel, Jonathan S.|author3=Kim, LeeAnn|author4=Bawendi, Moungi G.|author5=Bulovic, Vladimir|title=Light-Emitting Diodes: Research, Manufacturing, and Applications IX|chapter=Method for fabrication of saturated RGB quantum dot light-emitting devices |editor3-first=E. Fred|editor3-last=Schubert|editor2-first=H. Walter|editor2-last=Yao|editor1-first=Steve A|editor1-last=Stockman |series=Proceedings of the SPIE  |volume=5739|pages=108–115 |doi=10.1117/12.590708 |bibcode=2005SPIE.5739..108C|s2cid=15829009}}</ref>

===Phase separation===

Phase separation is suitable for forming large-area ordered QD monolayers. A single QD layer is formed by spin casting a mixed solution of QD and an organic semiconductor such as TPD (N,-Bis(3-methylphenyl)-N,-diphenylbenzidine). This process simultaneously yields QD monolayers self-assembled into hexagonally close-packed arrays and places this monolayer on top of a co-deposited contact. During solvent drying, the QDs phase separate from the organic under-layer material (TPD) and rise towards the film's surface. The resulting QD structure is affected by many parameters: solution concentration, solvent ration, QD size distribution and QD aspect ratio. Also important is QD solution and organic solvent purity.<ref>{{Cite journal|date=2005|display-authors=4|author=Coe-Sullivan, Seth|author2=Steckel, Jonathan S.|author3=Woo, Wing-Keung|author4=Bawendi, Moungi G.|author5=Bulovic, Vladimir|title=Large-Area Ordered Quantum Dot Monolayers via Phase Separation During Spin-Casting|volume=15|pages=1117–1124|journal=Advanced Functional Materials|url=http://www.rle.mit.edu/organic/documents/LargeAreaQDMonolayers-AdvFuncMater2005.pdf|doi=10.1002/adfm.200400468|issue=7|bibcode=2005AdvFM..15.1117C|s2cid=94993172|access-date=30 April 2010|archive-url=https://web.archive.org/web/20160513220335/http://www.rle.mit.edu/organic/documents/LargeAreaQDMonolayers-AdvFuncMater2005.pdf|archive-date=13 May 2016}}</ref>

Although phase separation is relatively simple, it is not suitable for display device applications. Since spin-casting does not allow lateral patterning of different sized QDs (RGB), phase separation cannot create a multi-color QD-LED. Moreover, it is not ideal to have an organic under-layer material for a QD-LED; an organic under-layer must be homogeneous, a constraint which limits the number of applicable device designs.

===Contact printing===

The contact printing process for forming QD thin films is a solvent-free water-based suspension method, which is simple and cost efficient with high throughput. During the process, the device structure is not exposed to solvents. Since charge transport layers in QD-LED structures are solvent-sensitive organic thin films, avoiding solvent during the process is a major benefit. This method can produce RGB patterned electroluminescent structures with 1000 ppi (pixels-per-inch) resolution.<ref name=bul3>{{Cite journal|date=2008|display-authors=4|author=Kim, LeeAnn|author2=Anikeeva, Polina O.|author3=Coe-Sullivan, Seth|author4=Steckel, Jonathan S.|author5=Bulovic, Vladimir|title=Contact Printing of Quantum Dot Light-Emitting Devices|volume=8|pmid=19053797|issue=12|pages=4513–4517|journal=Nano Letters|doi=10.1021/nl8025218|bibcode=2008NanoL...8.4513K}}</ref>

The overall process of contact printing:

* Polydimethylsiloxane (PDMS) is molded using a silicon master.
* Top side of resulting PDMS stamp is coated with a thin film of Parylene-c, a chemical-vapor deposited (CVD) aromatic organic polymer.
* Parylene-c coated stamp is inked via spin-casting of a solution of colloidal QDs suspended in an organic solvent. 
* After the solvent evaporates, the formed QD monolayer is transferred to the substrate by contact printing.

The array of quantum dots is manufactured by self-assembly in a process known as spin casting: a solution of quantum dots in an organic material is poured onto a substrate, which is then set spinning to spread the solution evenly.

Contact printing allows fabrication of multi-color QD-LEDs. A QD-LED was fabricated with an emissive layer consisting of 25-μm wide stripes of red, green and blue QD monolayers. Contact printing methods also minimize the amount of QD required, reducing costs.<ref name=bul3/>

==Comparison==

Nanocrystal displays would render as much as a 30% increase in the visible spectrum, while using 30 to 50% less power than LCDs, in large part because nanocrystal displays would not need backlighting. QD LEDs are 50–100 times brighter than CRT and LC displays, emitting 40,000&nbsp;nits (cd/m<sup>2</sup>). QDs are dispersable in both aqueous and non-aqueous solvents, which provides for printable and flexible displays of all sizes, including large area TVs. QDs can be inorganic, offering the potential for improved lifetimes compared to OLED (however, since many parts of QD-LED are often made of organic materials, further development is required to improve the functional lifetime.) In addition to OLED displays, pick-and-place microLED displays are emerging as competing technologies to nanocrystal displays. Samsung has developed a method for making self-emissive quantum dot diodes with a lifetime of 1 million hours.<ref>{{Cite web|url=https://www.zdnet.com/article/samsung-develops-method-for-self-emissive-qled/|title=Samsung develops method for self-emissive QLED|website=[[ZDNet]]}}</ref>

<!-- Deleted image removed: [[File:QD LED color coordiations.JPG|thumb|Quantum dot light emitting diode color boundary]] -->
Other advantages include better saturated green colors, manufacturability on polymers, thinner display and the use of the same material to generate different colors.

One disadvantage is that blue quantum dots require highly precise timing control during the reaction, because blue quantum dots are just slightly above the minimum size. Since sunlight contains roughly equal luminosities of red, green and blue across the entire spectrum, a display also needs to produce roughly equal luminosities of red, green and blue to achieve pure white as defined by CIE Standard Illuminant D65. However, the blue component in the display can have relatively lower color purity and/or precision (dynamic range) in comparison to green and red, because the human eye is three to five times less sensitive to blue in daylight conditions according to CIE luminosity function.

=

== See also ==
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also}}

=Notes==
{{notelist}}

==References==
{{Reflist|2}}

==External links==
*[https://www.bccresearch.com/report/NAN027B.html Quantum Dots: Technical Status and Market Prospects]
*[https://news.vanderbilt.edu/2005/10/20/quantum-dots-that-produce-white-light-could-be-the-light-bulbs-successor-59204/ Quantum dots that produce white light could be the light bulb's successor]
{{DEFAULTSORT:Quantum Dot Display}}

{{Sourceattribution|Quantum dot display}}