High Color Gamut Research Articles

P‐7.21: The Main Technologies of Large Size 8K LCD Display System

In recent years，BOE has launched many excellent display products and has been adhering to the research of 8K technology, while leading related technologies. In 2021, we launched a new large size smart display terminal system. In this paper, a new hardware system and several key technologies are proposed for large-size 8K display terminals. In this paper, it is focused on introducing the system architecture of the hardware system, the design of the high zones Mini-LED backlight and driver system, the realization of high color gamut display, and the solution and effect of eyesafe about display.

59‐2: Invited Paper: High‐Color‐Gamut Organic Light‐Emitting Diode Microdisplay for Augmented‐Reality/Virtual‐Reality Devices

In this paper, we developed high color gamut OLED microdisplay. To minimize the crosstalk, a single stack white OLED structure with RGB main peaks was adopted, and RGB color filters were directly patterned on the OLED. In addition, we designed the optical crosstalk prediction model, which could predict the light loss according to the thickness of the passivation layer. As a result, we achieved high color gamut of 125.0% at sRGB, which demonstrated the high color gamut OLED microdisplay.

P‐112: A Super Excellent Image Quality LCD Display Technology

Based on the liquid crystal display technology, by studying the polarizer compensation function, color film and backlight matching, liquid crystal materials and process improvement, this paper realizes the functions of excellent image quality and fast response, including wide viewing angle, high contrast, high color gamut, so as to make the liquid crystal display benchmark and catch up with and surpass the OLED products.

52‐2: Ultrawide‐Color Gamut, Low‐Power Consumption White OLEDs for Large 8K OLED TV

Next generation WOLED displays demand high color gamut and low power consumption, but it is a severe challenge for the WOLED display technology to meet the needs for high color gamut and low power consumption simultaneously. In this paper, with the optimization of WOLED spectrum which was well matched with CF, wide color gamut close to 99% at DCI‐P3 standard and lower power consumption of W/R/G/B as well as BDR power consumption is obtained.

Effect of silica encapsulation on the stability and photoluminescence emission of FAPbI3 nanocrystals for white-light-emitting perovskite diodes

The α-FAPbI 3 perovskite nanocrystals exhibit interesting optical properties, which make them attractive for versatile optoelectronic applications; however, the spontaneous phase transformation to the non-perovskite phase (δ-FAPbI 3 ) in humid conditions requires a new strategy to improve the phase stability of the material. We employed 3-Aminopropyl triethoxysilane (APTES)-assisted reprecipitation and sol-gel methods at ambient temperature to prepare stable α-FAPbI 3 nanocrystals embedded in a silica matrix. Transmission electron microscopy (TEM) and X-ray diffraction analysis determined that ultrafine perovskite nanocrystals (11.5 ± 3 nm) were uniformly distributed in a silica matrix. Investigations of the optical properties of the synthesized materials revealed that about 94% of the photoluminescence (PL) emission of silica-encapsulated FAPbI 3 nanocrystals was preserved under humid conditions (60%) after at least a month, while the PL emission of untreated FAPbI 3 was significantly decayed after few days. The thermal analysis also determined that the thermal stability of FAPbI 3 nanocrystals was improved by silica encapsulation. The red-emitting silica-encapsulated FAPbI 3 nanocrystals with a wavelength of 720 nm were used to fabricate white light-emitting diodes (LEDs) in a vertical structure consisting of a blue-chip, PMMA/CsPbBr 3 QDs, and PMMA/FAPbI 3 -SiO 2 QDs. Stable perovskite-based white LEDs with a color gamut of 144% NTSC were fabricated, which was better than many phosphor-based and perovskite-based LEDs. The synthesized composite perovskite nanocrystals could be used for next-generation optoelectronic devices. • Synthesis of silica-encapsulated FAPbI 3 quantum dots at ambient temperature by a combined LARP and sol-gel process. • Minor PL intensity loss in the humidified atmosphere after few months. • WLEDs with a high color gamut of 144% NTSC. • A pure red LED with coordination (0.729, 0.270).

Evolutionary Generation of Phosphor Materials and Their Progress in Future Applications for Light-Emitting Diodes.

Light-emitting diodes (LEDs) are attracting considerable attention around the world. Phosphor materials, as crucial color-converted components, play central roles in LED development. The demands for phosphor materials have become increasingly stringent over the past decades, from high brightness to narrowband emission or function-dependent spectrum engineering. Although substantial progress has been made for currently developed phosphor materials, simultaneously satisfying all requirements for high-level applications remains challenging. In this review, we aim to provide a comprehensive understanding of the development of phosphor materials in different generations and to elucidate the key designed mechanisms concerning the activators and the host structures to fulfill the aforementioned aspects. We highlight the developments in phosphor materials through the classification of demands for high luminescence, high thermal stability, narrowband emission for high color gamut, and broadband emission for near-infrared. We also focus on elucidating the key designed mechanisms of phosphor materials in different generations. Furthermore, future perspectives about micro-LED applications and nanoluminescent materials are provided. This study opens up an avenue for designing the luminescent materials of the future.

Rapid synthesis and theoretical analysis of CH3NH3Pb1-xCdxBr3 perovskite quantum dots for backlight LEDs: A step towards enhanced stability

Colloidal CH 3 NH 3 Pb 1-x Cd x Br 3 perovskite quantum dots (PQDs) have shown potential for the development of new solar cell and light-emitting diodes due to their enhanced optoelectronic properties. Here, we have reported a potential ligand-assisted room temperature rapid synthesis method for partial cation exchange in colloidal CH 3 NH 3 Pb 1-x Cd x Br 3 PQDs, where exchange of Pb 2+ takes place for various similar cations, which result in doped CH 3 NH 3 Pb 1-x Cd x Br 3 maintaining its original PQDs shape and structure. There was lattice contraction was observed into the Cd doped perovskite. A blue shift in optical spectra was observed due to partial Pb 2+ exchange in place of Cd 2+ , however high photoluminescence quantum yields, sharp absorption features, and narrow emission of the original CH 3 NH 3 Pb 1-x Cd x Br 3 PQDs remained the nearly same. XPS study confirmed the incorporation of Cd 2+ ions in the place of Pb 2+ . Theoretical analysis was also performed to study the different structural and optical aspects of the doped perovskite samples. Furthermore, a prototype perovskite QDs based white LEDs was fabricated that have a higher color gamut. The current work presents a new possibility to develop stable PQDs with enhancing optoelectronic properties. • Rapid perovskite quantum dot synthesis within 30 min. • Cd incorporation enhanced the stability and performance of PQDs. • Theoretical and experimental investigation of Cd: MAPbBr 3 PQDs. • High color purity, PLQY, and intense PQDs enhanced thin films. • Backlight LEDs with high color gamut.

Organic light-emitting diode structure for high color gamut in high-resolution microdisplay: Over 90% color gamut based on BT.2020

To implement primary colors in high-resolution organic light-emitting diode (OLED) microdisplays, color filters or cavity structures are applied to white OLEDs (WOLEDs). In terms of the high luminance and high color gamut required by microdisplays, two methods were experimentally compared in this study. In addition, a method for applying a color filter to WOLEDs with high-order cavity structures is proposed. The luminance of the proposed structure is lower than that of the cavity-only structure, but is similar to that obtained by applying a color filter to normal WOLEDs. Although previous methods do not satisfy the BT.2020 standard, the proposed structure achieves 90.8% of the BT.2020 standard.

Hybrid Device of Blue GaN Light-Emitting Diodes and Organic Light-Emitting Diodes with Color Tunability for Smart Lighting Sources.

A lighting device with a wide color-tunable range is still a challenge for lighting based on either organic light-emitting diodes (OLEDs) or inorganic LEDs. In this work, we first proposed a novel hybrid device of organic LEDs and inorganic blue GaN LEDs to achieve full white and other colors. Organic LEDs were stacked with green and red emissive layers and connected with blue GaN LEDs in parallel but in opposite polarity voltage. Under the alternate-current (AC) driving, the hybrid structure can be controlled independently by applying timing variable opposite voltages to emit the light from either blue LEDs or the stacked OLEDs for forming mixed colors. The hybrid device can generate white light, varying in a wide range by changing the amplitude and duty ratio (DR) of AC-driving signals, from cold white to standard white and to warm white (3668–11 833 K). When an AC voltage of (4.80 V, −2.45 V) was applied, the device has a high color gamut of 95.24% National Television System Committee (NTSC) and a high color rendering index (Ra) of 92.4%. The novel hybrid device with the blue LED and OLED in opposite polarity exhibits potential applications in smart solid-state lighting, display, and light communication.

A green emitting (Ba,Ca)ScO2F:Bi3+,K+ perovskite phosphor with high efficiency and good thermal stability for LED backlight displays

A new efficient green-emitting (Ba,Ca)ScO2F:Bi3+,K+ phosphor realizes a high color gamut of 110% of the NTSC value under 415 nm chip excitation.

Design of white tandem organic light‐emitting diodes for full‐color microdisplay with high current efficiency and high color gamut

Microdisplays based on organic light-emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a high-resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED-based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard.

Chasing Down the Eu2+ Ions: The Delicate Structure−Property Relationships in the Ultra‐Narrow Band Phosphor K1.6Na2.1Li0.3[Li3SiO4]4:Eu2+

AbstractEu2+‐activated phosphors of the UCr4C4 structure type have emerged as promising new (ultra‐)narrow band phosphors. Especially the UCr4C4‐type alkali lithosilicates have caused a sensation in the field of phosphor research in the recent years due to their consistent (ultra)narrow‐band luminescence in the cyan and green range that can pave the way to novel backlighting LEDs with high color gamut. The compound “K2Na2[Li3SiO4]4:Eu2+” stands out with a strikingly narrow emission in the cyan range (<0.2 eV or <30 nm full width at half maximum in the energy or wavelength scale, respectively) but the position of the Eu2+ ions within this structure has been so far controversial. High‐resolution photoluminescence spectroscopy at 10 K reveals a complex emission spectrum with seven emission bands in the violet to green range. Combination with single‐crystal X‐ray diffraction (SCXRD) demonstrates that the cation channels in the structure also contain Li+ ions. The presence of emission bands in the violet and blue spectral range reveals that the Eu2+ ions also occupy the available K sites in the structure independently confirmed by advanced ligand field calculations. This study demonstrates that a combination of SCXRD, photoluminescence spectroscopy, and theory can help elucidate advanced structural problems.

Lead oxide enables lead volatilization pollution inhibition and phase purity modulation in perovskite quantum dots embedded borosilicate glass

Embedding all-inorganic cesium lead halide CsPbX3 (X=Cl, Br, I) perovskite quantum dots (PQDs) PQDs into glass is one of the most effective strategies to improve their optical, thermal and chemical stabilities. Herein, by using PbO instead of PbBr2 as the lead source, it is effective to lower the melting temperature and reduce the volatilization pollution from lead halide raw materials. Thus, a high-purity CsPbBr3 PQDs embedded glass with 71.5 % PLQY was successfully prepared. The thermal stability, and photo-aging properties were also improved. By simply changing the halogen element, the red and blue CsPbX3 PQDs embedded glasses were successfully prepared. The white LED fabricated by coating obtained green/red CsPbX3 PQDs embedded glass on a blue chip displays high color gamut of 121.9 % NTSC standard and >91.1 % Rec. 2020 standard, which embodies the great potential of PQDs embedded glass in lighting and display fields.

Three-wavelength white organic light-emitting diodes on silicon for high luminance and color gamut microdisplays

Organic light-emitting diode (OLED) microdisplays have attracted considerable attention owing to their low power consumption, rapid response, high contrast ratio, and self-luminescence. To expand the use of OLED microdisplays, high luminance and vivid color are required. Herein, we developed a high-luminance, low-voltage, three-wavelength, top-emitting white OLED (WOLED) using a silicon substrate for complementary metal–oxide–semiconductor-based, full-color microdisplay applications. Optimal thickness of the emitting layer and thickness and position of the interlayer were determined to improve device performance. The device exhibited luminance of ∼4,200 cd/m2 at 3.3 V, and the maximum luminance reached 170,000 cd/m2 at 11.4 V. In addition, red, green, and blue color filters were deposited onto the WOLED after the thin-film encapsulation process to verify feasibility of the device for full-color microdisplay applications. The color gamut of the developed WOLED with color filters was 136% compared to sRGB. The maximum luminance and color gamut of the developed device is among the highest values obtained to date for OLED microdisplays.

Diversity of Luminescent Metal Complexes in OLEDs: Beyond Traditional Precious Metals

Organic light-emitting diodes (OLED) have attracted increasing attention due to their excellent properties, such as self-luminosity, high color gamut and flexibility, and potential applications in display, wearable devices and lighting. The emitters are the most important composition in OLEDs, mainly classified into fluorescent compounds (first generation), metal phosphorescent complexes (second generation), and thermally activated delayed fluorescence (TADF) materials (third generation). In this review, we summarize the advances of novel emitters of organic metal complexes in the last decade, focusing on coinage metals (Cu, Ag, and Au) and non-precious metals (Al, Zn, W, and alkali metal). Also, the design strategy of d10 and Au(III) complexes was discussed. We aim to provide guidance for exploring efficient metal complexes beyond traditional phosphorescent complexes.

P‐9.2: Quantum Dots Color Filter Liquid Crystal Display

In recent years, as a hot inorganic luminescent materials, Quantum dots have been widely used in display devices because of their high photoluminescence efficiency and excellent color gamut. In order to further improve the performance of LCD display devices, we consider introducing quantum dot color film into the structure of LCD. In this report, we pixelate the QDs to replace the traditional color film, this is different from the QD was widely used method which QDs was made into thin film as part of the back light unit. Compared with the general LCD, QDCF can achieve higher efficiency, higher color gamut and wider viewing angle, in order to solve the polarization of the liquid crystal cell, we use WGP In liquid crystal cell to achieve high contrast ratio.

24‐3: High‐Color‐Gamut OLED Displays with Reduced Power Consumption for Laptop Applications

In this paper we discuss the benefits that can be realized by phosphorescent OLED technology for low power consumption high color gamut displays. We show that relative to LCD based displays, the higher the display color gamut, the more OLED displays have a power consumption advantage over LCDs, enabling high performance displays for laptops. Based on Intel's day in life PC usage model, our simulation shows that DCI‐P3 and 97% BT2020 color profiles will deliver 13% and 18% improvement respectively in battery life for OLEDs versus equivalent LCDs.

62‐8: Invited Paper: High Color Gamut QDot™ LCD Displays with Perovskite Quantum Dots: Devices Architecture, Performance and Reliability

Perovskite Quantum Dots (QDs) promise to deliver over 90% of Rec2020 color representation, the highest for RoHS compliant LCD displays. In this study, we strive to demonstrate the performance of LCD displays using QDot™ green emitting Perovskite QDs with various backlight architectures. Using different blue and red light sources, we fabricated four types of LCD display, which showed contrasting Rec2020 color gamut from 80 to 86% and brightness from 1000 to 2000 nits. With these impressive metrics, Perovskite Quantum Dots paves the way for mass adoption of the technology in the display field.

Deep blue fluorescent material with a narrow FWHM based on indolo[3,2,1-jk]carbazol/pyrimidine hybrids

A series of blue fluorescent materials containing electron accepting pyrimidine and electron donating bis(biphenyl)amine, diphenylcarbazole, and diphenylindolo[3,2,1- jk ]carbazole moieties were synthesized in moderate yields, and their optical and electrochemical properties were investigated. Diphenylindolo[3,2,1- jk ]carbazole was revealed to be a promising building block for deep blue fluorescent materials with a very narrow full width at half maximum. • Deep blue fluorescent materials based on indolo[3,2,1- jk ]carbazol/pyrimidine hybrids. • Deep blue fluorescent materials with a very narrow full width at half maximum and a high color gamut. • Indolo[3,2,1- jk ]carbazol/pyrimidine hybrids for blue emitting materials of OLED. • Indolo[3,2,1- jk ]carbazol/pyrimidine hybrids having small Δ E (S 1 -T 1 ) similar to TADF materials.

Quantum-dot and organic hybrid tandem light-emitting diodes with color-selecting intermediate electrodes for full-color displays.

The immaturity of the color patterning technology and the poor stability of blue (B) quantum-dots are two of the challenges that restrict the development of quantum-dot electroluminescence displays. In this work, we demonstrate a hybrid tandem light-emitting diode (LED), in which a yellow (Y) quantum-dot LED and a B organic LED are vertically connected using an IZO/Ag intermediate electrode. The transparent IZO sets the resonance wavelength of the Y-QLED and thus selectively converts the yellow emission into R or G emission, while the semi-reflective Ag enhances the optical interference of the B LED and hence improves the color saturation of the B emission. Enabled by the multi-functionalities of color-selection and color-enhancement of the intermediate electrode, the tandem LED can emit independently controllable R, G and B colors with a high color gamut of ∼110% NTSC without the need to pattern the light-emitting layers. The demonstrated tandem LED could provide a promising way for the realization of emitting-layer-patterning-free, color-filter-free and wide-color-gamut electroluminescence displays.