Quantum dot display
A quantum dot display is a display device that uses quantum dots, semiconductor nanocrystals which can produce pure monochromatic red, green, and blue light.
QDs are either photo-emissive or electro-emissive allowing them to be readily incorporated into new emissive display architectures. 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.
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.
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, MicroLED, or QNED display panels. QD-OLED displays, which use blue OLED panels with QD color filters, started coming to market in 2023. 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.
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. Starting in the early 2000s, scientists started to realize the potential of developing quantum dots for light sources and displays.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. 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.
Technology
Quantum dot enhancement film
A widespread practical application is using quantum dot enhancement film 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. At the Consumer Electronics Show 2015, Samsung Electronics, TCL Corporation and Sony showed QD-enhanced LED-backlighting of LCD TVs. 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.
Quantum dot on glass replaces QD film with a thin QD layer coated on top of the light-guide plate, reducing costs and improving efficiency.
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.
Quantum dot color converter
LCD
QD color converter LED-backlit LCDs would use QD film or ink-printed QD layer with red/green sub-pixel patterned 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.Because quantum dots depolarize the light, output polarizer 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.
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. As of December 2019, issues with in-cell polarizer remained unresolved and no LCDs with QD color converter appeared on the market since then.
QD-OLED
QD color converters can be used with OLED or micro-LED panels, improving their efficiency and color gamut. QD-OLED panels with blue emitters and red-green color converters have been researched by Samsung and TCL. 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. 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.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.
QNED
A further development of QD-OLED displays is quantum dot nanorod emitting diode display 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. Samsung Display was expected to begin test production of QNED panels in 2021,with mass production in 2024–2025, but test production has been postponed as of May 2022.
microLED
An QD chip-on-board color conversion layer can be applied to microLED microdisplays commonly used in near-eye devices such as augmented reality glasses and micro projectors. Two main color conversion technologies have been developed: one embeds quantum dots in nanoporous GaN on blue LEDs, 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. 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. 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. 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.Additional experimental methods, such as inkjet printing of QD inks, are also under investigation for micron-scale integration.
Self-emissive quantum dot diodes
Self-emissive quantum dot displays will use electroluminescent QD nanoparticles functioning as Quantum-dot-based LEDs 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, greatly reducing pixel response times by eliminating the liquid crystal layer. This technology has also been called true QLED display, and electroluminescent quantum dots.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 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. The demonstrated color gamut from QD-LEDs exceeds the performance of both LCD and OLED display technologies. To realize all-QD LED, the challenge that should be overcome is the currently poor electrical conduction in the emitting QD layers.
As cadmium-based materials cannot be used in lighting applications due to their environmental impact, InP ink-jet solutions are being researched by Nanosys, Nanoco, Nanophotonica, OSRAM OLED, Fraunhofer IAP, Merck, and Seoul National University, among others. As of 2019, InP based materials are still not yet ready for commercial production due to limited lifetime.
Mass production of active-matrix QLED displays using ink-jet printing was expected to begin in 2020–2021, 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, and in 2026, to appear by 2029.
At CES 2024, Sharp NEC Display privately demonstrated prototypes of 12" and 30" display panels.