Color Gamut Coverage Research Articles

Elevating Red Emission: Yb3+ Doped CsPbBr1I2 Nanocrystal Glass for Exceptional PLQY and Stability in Wide Color Gamut Backlit Displays

As display technologies progress towards enhanced visual performance, there was a growing demand for color conversion materials to meet increasingly stringent performance requirements. In recent years, all-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) had gained attention in the field of wide color gamut backlight displays due to their tunable full spectrum, narrow-band emission, high color purity, and ease of processing. However, red-emitting perovskite NCs were still facing challenges with photoluminescence quantum yield (PLQY) and stability. In this study, Yb3+ doped CsPbBr1I2 perovskite nanocrystal glass (Yb3+@CsPbBr1I2 PNG) was synthesized using a melt-quenching technique. Samples emitting at a narrow band centered at 630nm, with a full width at half maximum(FWHM) of 31.8nm, exhibited a high PLQY of 80.36% and retained fluorescence intensity at 98.2% of the initial value in water, maintaining to 92.6% after continuous blue light irradiation for 60 days. Moreover, the optical conversion film Yb3+@CsPbBr1I2@CsPbBr3@PET developed in our study showcased color gamut coverage surpassing 132.9% of the NTSC 1953 standard and 98.8% of the Rec.2020 standard. In summary, the highly efficient and remarkably stable red-emitting Yb3+@CsPbBr1I2 PNG composite material introduced in this study paved the way for future advancements in wide color gamut and ultra-high definition backlight display technologies.

Enhanced stability of perovskite CsPbBr3 QDs via Synergetic encapsulation with ZnO nanocrystals and commercial polymer

Lead halide perovskite nanocrystals with attractive optical properties and low-cost production have emerged as a reliable and promising candidate for next-generation display applications. However, the preparation of optical devices while maintaining high performance in complex environments poses a prominent challenge. Herein, a flexible, stretchable and stable nanocomposite was fabricated through embedding CsPbBr3 QDs (PeQDs) into ZnO nanocrystals and polymer, leading to the enhancements of both stability and luminescence efficiency. This simple approach allows PeQDs own a uniform size of ∼14 nm. Optical characterization showed that the PeQDs size did not change after embedding ZnO nanocrystals, while these QDs exhibit a distinct green emission, with emission centering at 518 nm and narrow bandwidth of ∼20 nm. It was also found that the PeQDs/ZnO/EPDM nanocomposite maintained sufficient stability even after being left in an outdoor environment for 27 days, soaked in water for 60 h, and placed on a hot plate at 90 °C for 60 min. Besides, nanocomposite still maintain good luminescent properties even when stretched four times its original length. Furthermore, using this PeQDs/ZnO/EPDM nanocomposite, the synthesized white light emitting diode (WLED) exhibits a color gamut coverage rate of 129 % under standard NTSC, and 97 % under standard Rec.2020. By using this PeQDs/ZnO/EPDM encapsulation adhesive film, the absolute efficiency of solar cell can be improved by 0.23 %. This work highlights a new insight into defect passivation techniques for PeQDs by the utilization of heterogeneous structures provided by metal oxides.

Dynamic multi-color switching using ultrathin vanadium oxide on aluminum-based asymmetric Fabry–Pérot resonant structure

Vanadium dioxide (VO2) exhibits strong infrared optical switching due to its insulator–metal phase-transition property. However, in the visible wavelengths, its intrinsic optical switching is quite low. Current research explores solutions like multilayering, intricate structural patterning, high thermal budget processes, and costly metals for improved color switching. Nonetheless, the color gamut coverage with these methodologies remains notably limited. This work overcomes these limitations and demonstrates dynamic multi-color switching covering a large color gamut using a simple, unpatterned, ultrathin (∼ λ14, where wavelength λ is taken as 575 nm at the center of the visible spectrum) asymmetric Fabry–Pérot structure of VO2 on aluminum (Al). We use the transfer matrix method to design the VO2/aluminium (Al)/sapphire structure for maximum visible reflectance switching. VO2 films are synthesized using a simple, low thermal budget atmospheric oxidation of vanadium (V). With varying oxidation durations, different colors of the oxidized samples are observed. Consistent and reversible color-switching is observed visibly and in reflectance measurements with the change in temperature from low (RT ∼ 30 °C) to high (HT ∼ 100 °C) or vice versa due to the phase transition property of the VO2 layer in the structure. Compared to the existing studies, this work shows a significant change in chromaticities and covers a large color gamut when plotted on the CIE chromaticity diagram. This work has potential applications in the fields of display, thermochromic structures, and visible camouflage.

Deep learning-assisted inverse design of metasurfaces for active color image tuning.

Metasurfaces, artificial planar nanostructures, offer numerous advantages for color printing applications, including ultra-high resolution, resistance to fading, wide color gamut coverage, and multifunctional capabilities. Due to the sensitivity of their resonance spectra to the external environment, metasurfaces have garnered significant interest for color tuning applications. However, most existing approaches are limited to passive color tuning, wherein only the color changes passively while the composite color image remains unaltered. Active color image tuning, on the other hand, requires precise matching of both color and intensity to the designed targets before and after the tuning process. In this study, we propose a novel approach for active metasurface color image tuning by modulating the environmental refractive index. Building upon a forward neural network that establishes the relationship between the metasurface geometric parameters and color/intensity information, we employ a multi-objective inverse adjoint neural network. This network not only overcomes the inherent 'one-to-many' problem in inverse design using neural networks but also facilitates active color image tuning under three distinct environmental conditions. Our work provides a new approach for the inverse design of metasurfaces and opens up possibilities for applications in dynamic color printing, information encryption, and other related fields.

Enhanced stability of CsPbBr3 nanocrystals through Al2O3 and polymer coating.

Lead halide perovskite nanocrystals have emerged as a promising candidate for next-generation display applications due to their attractive optical properties and low-cost production. However, the environmental stability of perovskite remains a major challenge, hindering their practical applications and scalability for commercialization. In this study, we present an effective method to enhance the stability of CsPbBr3 nanocrystals by coating them with a combination of Al2O3 and a polymer. The unique double protection structure significantly improves their resistance to moisture, heat, and polar solvents. It is worth noting that compared with the ordinary CsPbBr3 nanocrystals, the modified nanocrystals have better stability and higher luminous intensity. After soaking in water for 360 hours, the modified nanocrystals retained 85% of their initial luminous intensity. Under optimal conditions, the luminous intensity of modified nanocrystals increased by 36%. Furthermore, the thermal stability and organic solvent resistance of the nanocrystals are improved compared with the nanocrystals uncoated with Al2O3. The synthesized white light emitting diode using the modified PNCs achieves a color gamut coverage rate of 129% under standard NTSC, and 95% under standard Rec.2020, indicating its potential for future display applications. This research presents a promising approach for the development of stable perovskite nanocrystals with enhanced performance in various optoelectronic devices.

Tunable luminescence properties of the Ca3-xLuxSc2-xMgxSi3O12:Ce3+ phosphor based LD lighting

In white-light laser diodes (LD) illumination, the full width at half maximum (FWHM) of the emission spectrum of blue LD is too narrow, leading to the cyan light deficiency, while the emitting color of the material limits the red component of the device. Therefore, in this paper, Ca3-xLuxSc2-xMgxSi3O12:Ce3+ (CLSMS:Ce3+, x = 0, 0.5, 1, 1.5, 2) phosphor samples were successfully prepared based on Ca3Sc2Si3O12 (CSS) cyan-green fluorescent materials with different concentrations of Lu–Mg ions introduced in the matrix instead of Ca–Sc ions. And their luminescence properties were systematically investigated. The peak of the sample was shifted from 508 nm to 590 nm as the concentration of Lu–Mg increased. The thermal stability of the series phosphors gradually deteriorated with increasing Lu–Mg concentration. At 423 K, the emission intensity of the samples was 98.11 %, 94.13 %, 92.18 %, 81.96 % and 77.60 % of that at 298 K, respectively. And the thermal quenching activation energy also gradually decreases. The CLSMS:Ce3+ fluorescent materials were prepared into LD devices and tested. It was found that the series of samples showed a gradual decrease in cyan-green light and a gradual increase in red light with increasing Lu–Mg concentration. The CSS compounded with CaLu2Mg2Si3O12 (CLMS) obtained a white LD device with color coordinates of (0.3440, 0.3455), and the cyan and red components of the samples were compensated. In summary, this study demonstrates that CLSMS:Ce3+ is a very promising fluorescent material to extend the color gamut coverage of fluorescent materials. And it has a potential reference value for the field of white-light LD lighting.

Fano resonant optical coatings platform for full gamut and high purity structural colors

Structural coloring is a photostable and environmentally friendly coloring approach that harnesses optical interference and nanophotonic resonances to obtain colors with a range of applications including display technologies, colorful solar panels, steganography, décor, data storage, and anticounterfeiting measures. We show that optical coatings exhibiting the photonic Fano Resonance present an ideal platform for structural coloring; they provide full color access, high color purity, high brightness, controlled iridescence, and scalable manufacturing. We show that an additional oxide film deposited on Fano resonant optical coatings (FROCs) increases the color purity (up to 99%) and color gamut coverage range of FROCs to 61% of the CIE color space. For wide-area structural coloring applications, FROCs have a significant advantage over existing structural coloring schemes.

55‐2: Invited Paper: Quantum Dot Color Conversion for Displays

Quantum dot (QD) color conversion has recently been demonstrated in commercial QD‐OLED displays on the market exhibiting exceptional color gamut coverage, brightness, black levels, and viewing angles. To continue developing QDs for a wide range of future display technologies, two key aspects remain under study. First, how can blue light absorption be maximized for small pixel formats (<10 μm) requiring thin QD color conversion layers and second, as pixel sizes shrink and display brightness increases, how can these materials remain stable under high blue‐light excitation flux (up to 5W/cm 2)? Here we describe experiments addressing these two areas of continued development for heavy‐metal free QDs.

Quantum Dot Enabled Efficient White LEDs for Wide Color Gamut Displays

AbstractIn recent years quantum dots (QDs) emerge as a powerful building block for liquid‐crystal display (LCD) technology, and they are successfully used in the form of color enhancement films. However, their transition toward efficient and wide color gamut LEDs for backlighting remain as an important challenge, which can decrease the required amount of QDs per TV for orders of magnitude. Herein, QD‐based white LEDs are reported that can simultaneously operate with a high external quantum efficiency (EQE) of 39.8% and a wide NTSC color gamut coverage of 133.3%. For red‐emitting spectral range, giant CdSe/CdS core/shell QDs are synthesized via hot injection method, and it is observed that 20 monolayers of CdS shell can lead to a near‐unity photoluminescence quantum yield (PLQY) of 98%. In addition, green‐emitting CdZnSeS/ZnS alloyed core/shell QDs show a PLQY of 97% with a narrow full width at half maximum (FWHM) of 20 nm. To maintain the optical properties of QDs in device architecture, QDs are injected in liquid matrix on blue LED chips and used as the backlighting source for LCD TV that lead to bright and vivid colored images. QD‐based white LEDs with high efficiency and wide color gamut have significant potential for next‐generation display technology.

Fundus-Vascular Responses to Color Deviation Caused by Non-Oxidative Blue Filtering.

Aims Short-wavelength blue light damaged retina by the oxidative stress in the retinal pigment epithelial (RPE) cells. Filtering blue light from screen could reduce blue hazard, whereas it inevitably altered color-gamut coverage and color-deviation level. Although abnormal fundus-vascular density (FVD) sometimes indicated fundus disease, few researchers noticed its responses to the variation of color-gamut coverage and color-deviation level. Methods In this study, we performed cellular experiments and analyzed the RPE cell viabilities (CVs) in spectrums with different blue (455-475 nm) ratios to describe the corresponding oxidative-stress levels. Further, we investigated the effects of color-gamut and deviation on FVD variations during the screen-watching task using human factor experiments with 30 participants (university students, including 17 males and 13 females, 21 to 30 years old). Results RPE CVs were similar in different spectrums, implying that non-oxidative blue filtering hardly contributed to CV improvement. Color-deviation level seems to induce more significant effects on the visual function compared to color-gamut coverage, and MTF and FVD presents similar variation trends during the visual task. Conclusion Oxidative-free blue filtering contributed little to decrease retinal oxidative stress yet caused color-deviation increase, which caused significant FVD reduction.

Wide color gamut, low non-visual effect, and their stabilities related to luminous properties in four-primary-color display

The circadian effect and photobiological safety of the display should be concerned, as well as the color gamut. By adding another primary color to the traditional blue-green-red (RGB) direct emission display, a four-primary-color display was proposed. The display presents wide color gamut and high stability with variation of primary colors. The optimal color gamut coverage (CGC) in Rec. 2020 standard reaches 98.2 %, and it also maintains above 96.5 % with 20 nm variation of peak wavelengths and full widths at half maximum (FWHMs). At D65 white point, the melanopic efficacy of luminous radiation (MELR) of four-primary-color display decreases to 0.60, which is 29.4 % and 43.9 % less than liquid crystal display (LCD) and organic light-emitting diode (OLED) display, respectively. Presenting ten reference colors, the MELRs of four-primary-color display are also less than other displays in most cases. In addition, the blue light hazard efficiency of radiation (BLHER) of four-primary-color display is slightly less than other displays. At last, the further improvement for the four-primary-color display was discussed.

23‐1: Invited Paper: Visualization of Color‐Gamut Coverage‐Gamut Ring Intersection

The D50 CIELAB gamut volume was standardized as a suitable and unified gamut size measurement methodology. The color gamut volume is visualized using proportionate gamut rings in a two‐dimensional diagram. Gamut ring intersection assists the visual comparison of the size and shape of the color gamut coverage between a display and a reference. This paper introduces a desktop application with an intuitive graphical interface for visualizing the gamut rings and describes the algorithm of the gamut ring intersection.

Optimizing the display performance for virtual reality systems

We propose a systematic optimization method for two commonly used display devices, organic light-emitting diode (OLED) display and liquid crystal display (LCD), for virtual reality (VR) headsets. An optical simulation model for the VR system is established, and three performance metrics, namely total light efficiency (TLE), field color gamut coverage, and field color non-uniformity, are proposed as the optimization objectives. For the RGB (red, green, and blue) OLED display, the microcavity structure is optimized to suppress the field color unevenness while maintaining a high TLE and large field color gamut coverage. For the direct-lit LCD, the optimization is from the viewpoint of entire VR system. A two-dimensional patterned prism film is implemented in the backlight unit to locally modulate the radiation pattern of the LCD. Thus, the vignetting effect in the VR system is alleviated and the TLE is further enhanced by 40%. After optimizing the OLED display and LCD, their pros and cons in the VR systems are analyzed. Our optimization method is proven to be effective for designing a proper display panel for VR systems.

Comparative evaluation of color reproduction ability and energy efficiency between different wide-color-gamut LED display approaches

LED display is valued as a promising future generation of display if breakthrough in micron-size LED technology is made. In this study, for LED display with contemporary tri-primary design, wide-color-gamut design of higher-saturation tri-primary and that of multi-primary, calculation is targeted at color gamut coverage ratio and power consumption. Based on the results, evaluation is made in terms of color reproduction ability and energy efficiency. It turns out that selectable multi-primary design (S-MPD) proposed in this paper is a much more energy-efficient color gamut expanding approach for LED display. This finding might be a reference to further research on wide-color-gamut LED display.

In-situ stabilization strategy for CsPbX3-Silicone resin composite with enhanced luminescence and stability

Abstract Inorganic lead halide perovskite (CsPbX3, X = Cl, Br, I) nanocrystals (LHP NCs) are promising materials for a variety of photonic or optoelectronic applications. Yet their intrinsic instability issue remains a critical challenge to overcome. Encapsulation of ionic LHP NCs in inert matrices such as polysiloxanes has been proved as an effective stabilization strategy, but the ex-situ synthesis of LHP NCs remains a limiting factor. Herein, an in-situ stabilization strategy that involves synergistic crystallization of LHP NCs and crosslinking of addition-type silicone oil precursors is reported. This simple, yet general stabilization strategy can effectively passivate the trap defects and increase the radiative recombination of CsPbX3 NCs, which leads to a significant enhancement of the photoluminescence quantum yield (PLQY) from 68% for the solution to 82% for the composite powder. A series of CsPbX3-silicone resin composites with tunable emission wavelength ranging from 445 to 613 nm can be simply obtained by using suitable halide salts. Because of the protection of the silicone resin, the CsPbBr3-silicone resin composites exhibit high stability against moisture or heat in the ambient environment and could still keep their photoluminescence (PL) emission after being kept in air for one year or immersed in water for two months. Such composites have been used as functional downconverters in white LEDs that demonstrated a 92.7% color gamut coverage of Rec.2020. This work provides an alternative approach to solve the challenging stability issue of perovskite NCs.

All‐Solution Processed Multicolor Patterning Technique of Perovskite Nanocrystal for Color Pixel Array and Flexible Optoelectronic Devices

AbstractIn the present study, a new patterning method is introduced through the surface modification and stabilization of perovskite nanocrystals, which is compatible with conventional photolithography process based on all‐solution processes. Chemically designed gel‐type silica‐coated CsPbX3 (X = Br, I, etc.) perovskite nanocrystals combined with dip coating method are introduced to form stable and uniform films. Analyses of the physical and chemical states of nanocrystals and investigation of the kinetics in silica formation are conducted. In an optimized condition, physically uniform and chemically stable perovskite thin films are deposited on various substrates such as flexible, stretchable substrates, or even nonflat objects. By adopting these advantages and developing stable photolithographic chemicals, the high resolution patterns are successfully patterned with green and red emitting CsPbBr3 and CsPbBr3I3−x perovskites with the size down to 5 µm of radius and even a multicolor pixel array which can be used for the color filter, light converting or detecting applications. Flexible white light emitting diode is also fabricated with a large color gamut coverage. This work provides a fundamental understanding of perovskite nanocrystals, and also offers a technological breakthrough enabling various optoelectronic applications.

Design and Simulation of Low Circadian Action Micro-LED Displays with Four Primary Colors

Nowadays, displays are ubiquitous in our daily lives. Long-time exposure to a display’s unnatural light could influence the user’s circadian rhythm, especially at night. Here, we propose a four-color micro-light-emitting diode (LED) display to achieve low circadian action for nighttime uses. Specifically, we evaluate the RGBW-type (red, green, blue, and white) and RYGB-type (red, yellow, green, and blue) micro-LED displays in terms of circadian effect and color gamut coverage. With the addition of an extra white subpixel, it was found that the circadian effect at night can be reduced dramatically, but the color gamut remains unchanged. However, with an additional yellow subpixel, both the circadian effect and color gamut were found to improve. Finally, we simulated the circadian illuminance of real image contents for different displays. In comparison with existing liquid crystal displays, organic LED displays, and RGB (red, green, blue) micro-LED displays, the proposed four-primary-color micro-LED displays can significantly reduce the circadian effect at night.

5‐3: 3‐Stacked Top‐Emitting White OLEDs with Super‐Wide Color Gamut and High Efficiency

A set of top‐emitting OLED with wide‐color gamut and high‐efficiency were successfully fabricated by using 3‐stacked B/RG/B tandem structure and color filter. Optimization of MgAg and Indium Zinc Oxide (IZO) composite structure made the devices with IZO served as capping layer almost identical to the devices with conventional organic capping layer. On the whole, they exhibited 90% color gamut coverage of the ultra‐high definition display standard BT.2020, while maintaining high efficiency of red 15.5 cd/A, green 26.6 cd/A, blue 3.5 cd/A. The impressive properties make them applicable to a variety of occasions, such as the medium‐sized notebook monitors, emerging high‐specification virtual and augmented reality (VR/AR) technologies, and special medical displays.

Emerging Perovskite Nanocrystals-Enhanced Solid-State Lighting and Liquid-Crystal Displays

Recent advances in perovskite nanocrystals-enhanced solid-state lighting (SSL) and liquid-crystal displays (LCDs) are reviewed. We first discuss the development, optical properties, and stability issue of materials, and then we evaluate the performance of SSL and LCDs with perovskite downconverters adopted. In SSL performance evaluation, we investigate the fitting-curve effect in calculations and optimizations where simple Gaussian fitting and precise fitting are compared in detail, and we further optimize for highly efficient, good color-rendering, and human-healthy SSL sources. For LCD performance evaluation, we study the intrinsic tradeoffs between total light efficiency and color gamut coverage. Through optimizations using real line shapes, Rec. 2020 standard coverage as large as 92.8% can be achieved through hybrid integration. Finally, we briefly discuss two future challenges: materials development and device integration. We believe the emerging perovskite nanocrystals are highly promising for next-generation SSL and LCDs.

Enhanced Optical Properties of Colored Semitransparent Ultrathin Hybrid Solar Cells Employing Fabry–Pérot Etalon With a Dielectric Overlay

We investigate the effect of a dielectric overlay in a planar microcavity on optical performances of colorful, see-through ultrathin amorphous silicon/organic hybrid solar cells, where a conventional Fabry–Perot cavity is integrated with a cathode. The proposed colored solar cell devices show an enhanced transmission efficiency by optimizing both a thickness and a refractive index of the dielectric overlay at a resonance wavelength, which is primarily attributed to a better admittance matching. In addition, a purity of semitransparent red, green, and blue colors is improved by increasing a thickness of metallic layers in the microcavity with little sacrificing the transmission efficiency; thus, achieving a wide color gamut coverage as compared to conventional liquid crystal displays. Furthermore, mitigating reflection losses at complementary wavelength ranges and creating sharp resonances lead to an improved photocurrent generation from the semitransparent hybrid solar cells. The study described in this work provides insights and possibilities to enhance the characteristic performances of diverse applications, such as energy-efficient display technologies and decorative solar cells.