Ultrawide color gamut LCD display with CdSe/CdS nanoplatelets

We present a liquid‐crystal display (LCD) backlight made of nanoplatelets (NPLs) for the first time. Owing to the narrow emission linewidth of NPLs (8‐12 nm) and quantum dots (QDs), the spectrum exhibits a wide color gamut display with a 139.9% color gamut of National Television System Committee (NTSC) 1953 standard and 104.5% Rec.2020 (ITU‐R Recommendation BT.2020), realizing a truly ultrawide color gamut LCD display.     

High‐efficiency quantum dot light‐emitting diodes with blue cadmium‐free quantum dots

We report outstanding electroluminescence properties of high‐efficiency blue cadmium‐free quantum dot light‐emitting diodes (QD‐LED). External quantum efficiency (EQE) of 14.7% was achieved for QD‐LED emitting at 428 nm. Furthermore, we developed high‐efficiency and narrow wavelength emission zinc selenide (ZnSe) nanocrystals emitting at 445 nm and achieved QD‐LED with an EQE of 10.7%. These new QDs have great potential to be used in next‐generation QD‐LED display with wide color gamut.     

Seventeen‐inch laser backlight in‐plane switching liquid crystal display with 8K, 120‐Hz driving,and BT.2020 color gamut

We have developed a 17‐inch laser backlight in‐plane switching liquid crystal display satisfying the main BT.2020 specifications, which are 8K, 120‐Hz driving, and a BT.2020 wide color gamut. The color gamut of the developed in‐plane switching liquid crystal display covers 98% of the BT.2020 wide color gamut, thanks to a laser backlight and appropriate color filters. The liquid crystal response time of 5 ms, which is sufficient for 120‐Hz driving, is achieved by adapting a faster in‐plane switching liquid crystal display, namely, the short‐range lurch control in‐plane switching liquid crystal display.     

High efficiency heavy metal free QD‐LEDs for next generation displays

In this paper, we report on our progress on developing heavy metal free (or Cd‐free) QD‐LEDs for all three colors. With improvement in synthesis, we have developed high quantum yield heavy metal free quantum dots (more than 95% for red and green and more than 80% for blue), with peak wavelengths suitable for BT.2020. Building upon these high‐performance quantum dots and through novel device structure design and optimization we have demonstrated high efficiency heavy metal free QD‐LEDs with EQE = 16.9%, 13%, 9% for red, green, and blue, respectively. Specifically, we report a systematic study on the impact of shell thickness to the device efficiency performance.     

High efficiency and ultra‐wide color gamut quantum dot LEDs for next generation displays

Colloidal quantum dot‐based hybrid light‐emitting diodes (QLEDs) have been demonstrated that exhibit quantum efficiencies (EQEs) >10% for all three fundamental colors red, green, and blue (21% EQE, 82 cd/A for green). This is the first report of a green QLED with EQE >20% and current efficiency >80 cd/A. The devices have the longest lifetimes reported in the literature (280k hrs) and extremely well‐tuned color fidelity. The narrow QLED emission spectra (full width at half maximum < 30 nm) and well‐controlled peak wavelengths generate a color gamut covering >170% of the National Television System Committee (NTSC) 1987 color space and ~90% of the Rec. 2020 color space. This color gamut is larger than that of OLED televisions in mass production and is the largest of all QLEDs reported. Additionally, these devices are completely fabricated using solution‐processing techniques. The extremely desirable properties of high efficiency, color tunability/fidelity, long lifetime, and low cost processing from solutions make QLED technology disruptive and will lead to next generation displays.     

A dual‐gap RGBW transflective TFT‐LCD with adjustable color gamut

Abstract— An adjustable‐color‐gamut dual‐gap RGBW transflective liquid‐crystal display that uses a four‐color manufacturing process and a color‐processing algorithm to achieve the appropriate color performance in both the transmissive and reflective modes is presented. Based on superior‐color‐transformation units, the total brightness and color gamut can be modified under different ambience. The highest NTSC color gamut in the reflective mode (reflectance, 4.4%) that has been fabricated successfully for a RGBW 1.5‐in. dual‐gap panel is 23% with a 7%, 17%, and 40% NTSC color gamut in the transmissive mode by using different algorithms. Compared to a typical RGB panel, it not only provides flexibility for any environment but also satisfies a variety of personal requirements. Based on personal preference, users have more choices to adjust the LCD settings such as color saturation, brightness, etc. The smart RGBW TRLCD will definitely become the developing trend towards sunlight‐readable LCDs in the near future.     

Micro‐cavity design of bottom‐emitting AMOLED with white OLED and RGBW color filters for 100% color gamut

Abstract— Two optical structures used for a bottom‐emitting white organic light‐emitting diode (OLED) is reported. An RGBW color system was employed because of its high efficiency. For red, green, and blue (RGB) subpixels, the cavity resonance was enhanced by the use of a dielectric mirror, and for the white (W) subpixel, the mirror was removed. The optical length of the cavities was controlled by two different ways: by the thickness of the dielectric filter on top of the mirror or by the angle of oblique emission. With both methods, active‐matrix OLEDs (AMOLEDs) that reproduced a color gamut exceeding 100% of the NTSC (National Television System Committee) standard were fabricated. More importantly, the transmission of a white OLED through R/G/B color filters was significantly higher (up to 50%) than that of a conventional structure not employing a mirror, while at the same time as the color gamut increased from ～75 to ～100% NTSC.     

Use of quantum rods for display applications

We examined the use of quantum rods (QRs) in two configurations for display applications, including the backlight and emissive color pixels for liquid crystal and organic light‐emitting diode displays, respectively. For the backlight, we used an electrospun nanofiber sheet embedded with QRs, and found the nanofiber‐aligned sheet showed polarized emission with a very high outcoupling efficiency. We then fabricated emissive color pixels with QRs using an inkjet printer, and evaluated their optical properties. The color gamut area size was 82% of the BT2020 standard and the overlap with it was 69%.     

Achieving a foldable and durable OLED display with BT.2020 color space using innovative color filter structure

A foldable active‐matrix organic light‐emitting diode display capable of enduring very severe folding and environmental impact was obtained using symmetric panel stacking with an innovative design of color filter structure. The display was subjected to in situ folding cycle under an ambient test condition of 60°C/90% relative humidity, and no performance degradation was found for the display and the touch function during and after the test. In addition, 95% coverage of BT.2020 color space was obtained without additional power consumption compared with that of the panel with National Television System Committee (NTSC) color space.     

Active matrix QD‐LED with top emission structure by UV lithography for RGB patterning

We have developed full colour top emitting quantum dot light‐emitting diode (QD‐LED) display driven by a 176‐ppi active matrix of metal oxide thin‐film transistors. Red, green and blue (RGB) QD‐LED subpixel emission layers are patterned by our original UV photolithography process and materials. We also demonstrate the potential to achieve high resolution such as 528 ppi using this process.     

White LEDs using the sharp β‐sialon: Eu phosphor and Mn‐doped red phosphor for wide‐color gamut display applications

The sharp β‐sialon (Si_6‐zAl_zO_zN_8‐z : 0 < z < 0.1):Eu green phosphor, combining with a blue LED and CaAlSiN₃:Eu red phosphor, is suitable for the wide‐color gamut white LEDs backlighting system, because of its sharp and asymmetric emission spectrum shape. However, the color gamut and the brightness of the aforementioned display is restricted because of the wide emission band of the CaAlSiN₃:Eu red phosphor. In this work, we used K₂SiF₆:Mn as an alternate red phosphor, which has a sharp emission spectrum. The display with the white LED using sharp β‐sialon:Eu and K₂SiF₆:Mn shows a wide‐color gamut, which covers the hole NTSC triangle. The use of K₂SiF₆:Mn enables to realize not only a wider color gamut but also a higher brightness of displays, compared with the use of CaAlSiN₃:Eu. Furthermore, it is confirmed that the white LED using sharp β‐sialon:Eu and K₂SiF₆:Mn is stable against temperature and also durable under the accelerated drive conditions.     

Analysis of standard chromaticity gamut area metrics

It is herein proposed to measure display gamut sizes by employing the International Telecommunication Union—Radiocommunication Sector Recommendation BT.2020 (Rec. 2020) area‐coverage ratios in the xy chromaticity diagram rather than the standard gamut area metrics that use the horseshoe‐shaped spectrum chromaticity area as the target in the u′v′ chromaticity diagram. It is more reasonable to use the Rec. 2020 gamut than the spectrum gamut as the target because the Rec. 2020 area‐coverage ratios in the xy diagram are better correlated than the spectrum area‐coverage ratios with the volume‐coverage ratios of object color gamuts that are visually significant in displaying natural scenes.     

Inorganic EL devices with high‐performance blue phosphor and application to 34‐in. flat‐panel televisions

Abstract— A high‐performance inorganic electroluminescence (EL) device has been successfully developed by using an EL structure with a thick dielectric layer (TDEL) and sputtered BaAl₂S₄:Eu blue phosphor. The luminance and efficacy were higher than 2300 cd/m² and 2.5 lm/W at L⁶⁰, 120 Hz, respectively. Furthermore, the luminance at L⁶⁰, 1.2 kHz was more than 23,000 cd/m². The phosphor layer has a single‐phase and a highly oriented crystalline structure. The phosphor also shows high stability in air. A 34‐in. high‐definition television (HDTV) has been developed by combining a TDEL structure and color‐conversion materials. The panels with an optimized color filter demonstrated a peak luminance of 350 cd/m², a color gamut of more than 100% NTSC, and a wide viewing angle similar to that of plasma‐display panels. The high reproducibility of the 34‐in. panels using our pilot line has been confirmed.     

A method for selecting display primaries to match a target color gamut

Abstract— A method for selecting primaries of a wide‐gamut display is proposed, in which display color gamut is designed to match a target color gamut in CIELAB color space. A standard deviation of the relative maximum chroma of display and target color gamuts is defined. The selection method optimizes display primaries for the minimum standard deviation so that display and target color gamuts are similar in shape. It is shown that the color gamut of a laser display designed by this method is similar in shape to the theoretical maximum, or optimal, color gamut of objects. It is also shown that the color gamut of an LED display can be designed to include 99.7% of the gamut of Pointer's real‐world surface colors. LED primaries are selected to minimize the standard deviation of the relative maximum chroma of effective display color gamut and a target color gamut which is defined to include Pointer's real‐world surface colors. For both the laser and LED displays, it is necessary to constrain the red‐primary wavelength to avoid excessive optical power for the red primary.     

Quantum dots: The ultimate down‐conversion material for LCD displays

Assuming that large color gamut and therefore better color reproducibility will be a highly desired feature of all displays as we look to the near future, we make the case in this paper that quantum dots (QDs) are currently the down‐conversion technology of choice that will allow liquid crystal display makers to cost‐effectively reach and exceed 100% of the NTSC (National Television Standard Committee) and Adobe RGB color standards while achieving maximum system efficiency. We will discuss in detail the numerous fundamental advantages of QDs over phosphors, along with their scientific origins, and make the case that QDs are the ultimate light generating material for next‐generation displays.     

Design considerations for highly efficient edge‐lit quantum dot displays

Quantum dots (QDs) are increasingly the technology of choice for wide color gamut displays. Two popular options to incorporate QDs into displays include on‐edge and on‐surface solutions. The opto‐mechanical design for an on‐edge QD solution including a LED light bar (“on‐edge QD light bar”) is more complex than the design for a standard white phosphor LED light bar. In this paper, we identify and investigate a range of design parameters for an on‐edge QD light bar, and we show that these parameters have significant influence on system efficiency and color uniformity. The effects of varying these parameters are explored through the use of a custom adjustable testbed and optical raytracing methods. Our testbed data demonstrate the inherent trade‐offs between efficiency and color uniformity and provide guidance for the design of high‐performing displays. The optical raytracing data demonstrate a good predictive capability and support the use of optical modeling methods for a detailed exploration of a wider range of design parameters.     

Heat‐ and water‐proof quantum dot/siloxane composite film: Effect of quantum dot–siloxane linkage

We report on the effect of linkage between quantum dot (QD) and siloxane matrix by preparing two different QD/siloxane films. One has chemical linkages between QD and siloxane matrix, and the other has no chemical linkages between QD and siloxane matrix. The QD/siloxane (methacryl) film, which has the chemical linkages, exhibits no degradation of photoluminescence (PL) quantum yield (QY) under heat or moisture condition for over 1 month, while the QD/siloxane (epoxy) film, which has no linkages, shows drastic decreased of PL QY. The chemical linkages between QD and siloxane matrix that makes effective siloxane passivation layer intact on the surface of QDs in QD/siloxane (methacryl) film. Given its exceptional stability with the help of linkages between QD and siloxane matrix, we expect that the QD/siloxane (methacryl) film is best fitted in PL‐type down‐conversion layer for display applications.     

Development of 100‐in. TFT‐LCDs for HDTV and public‐information‐display applications

Abstract— LCDs have achieved a full‐high‐definition resolution of 1920 × 1080 (16:9), 600‐nit brightness, 3000:1 dynamic contrast ratio, 92% color gamut, 178° viewing angle, and 5‐msec response time at all gray levels and are targeted for HDTV and public‐information‐display applications. Some unique technologies, such as Cu bus line, advanced wide view polarizer, and wide‐color‐gamut lamp, were applied. A new stitching‐free technology was developed to overcome the size limitation of the photomask in both the TFT and color‐filter processes. The size of the panel (100 in.), based on the wide format (16:9), is determined by the maximum efficiency of the world's first seventh‐generation line (glass size, 1950 × 2250 mm) in LG.Philips LCD's (LPL) Paju display cluster. The issues facing 100‐in. TFT‐LCDs will be discussed.     

Ten micrometer pixel,quantum dots color conversion layer for high resolution and full color active matrix micro‐LED display

A fine patternable quantum dots (QDs) color conversion layer (CCL) for high resolution and full color active matrix (AM) micro‐LED (μ‐LED) display is demonstrated. QDs CCL could be patterned until 10 μm using photolithography process. It is found that multicoatings with red and green QDs (R‐ and G‐QDs) CCLs on LED array can provide full color AM display.     

Patterned liquid‐crystal laser film for multi‐dimensional multi‐color emissive film technology

Abstract— A two‐dimensional array consisting of dye‐doped reflection‐mode holographic‐polymer‐dispersed liquid crystal (H‐PDLC) lasers with alternating pitch lengths is presented. These post structures each reflect at a narrow bandwidth of light. The addition of laser dye to the H‐PDLC system allows for the generation of laser emission at the edge of the reflection band, or photonic band gap. In patterning these H‐PDLC post structures, a narrow‐linewidth patterned emissive color film is realized. The potential of such films and their implication in the display industry is discussed. In creating a three‐color array, an active emissive color film could replace the backlight and color filter components within the display. Such a patterned system would possess a wide color gamut, through spatial color synthesis, formed by narrow‐linewidth lasing structures with well‐defined wavelengths of emission.