Color Conversion Research Articles

Investigation and comparison of the influence of modified DBR and yellow color filters for quantum dot color conversion-based micro LED applications

This study compares how a modified distributed Bragg reflector (DBR) and yellow color filter (Y-CF) increase the color purity, viewing angle, and brightness of the quantum dot color conversion layer (QDCC) for micro-LED displays. We designed and built a 53-layer high-performance modified DBR with almost total blue leakage filtering (T %: 0.16 %) and very high G/R band transmittance (T %: 96.97 %) for comparison. We also use a Y-CF that filters blue light (T %: 0.84 %) and has good G/R band transmittance (T %: 94.83 %). Due to DBR's angle dependency effect, the modified DBR/QDCC structure offers a remarkable color gamut (117.41 % NTSC) at the forward viewing angle, but this rapidly diminishes beyond 30°. The Y-CF/QDCC structure retains 116 % NTSC color at all viewing angles. Because of its consistent color performance at all viewing angles, sufficient brightness, and outstanding color gamut, the Y-CF/QDCC structure is the best option for contemporary QDCC-based micro-LED displays.

Improved multi-input parameter optimization method for camera colorimetric characterization

In order to improve the accuracy of camera colorimetric characterization, a multi-input parameter optimization method was proposed in this paper. The input parameters of the traditional camera characterization method were generally RGB values; in the proposed method, the luminance parameter L was introduced in addition to RGB values, and the four-input parameters of RGBL were used as input parameters for the conversion model. In the experiment, 549 colors were uniformly selected from the Munsell Book of Color (Matte Edition), and the RGBL values and corresponding CIEXYZ values of the selected colors were measured by a spectroradiometer and three cameras, including an imaging luminance meter, respectively. Then, a polynomial model and a backpropagation (BP) neural network model were employed to establish the improved color conversion model with RGBL four-input parameters, which was compared with three-input parameter models to verify the effectiveness of the proposed method. Experimental results show that the proposed method can significantly improve the conversion accuracy and reduce the color difference with a maximum reduction of 57.7% in CIELAB.

Enhancing thermal consistency and stability of quantum dots through encapsulation: A study on microscale-structured hybrid for WLEDs

Quantum dots (QDs) are regarded as highly potential materials for color conversion in light-emitting diodes (LEDs) and display technologies owing to their distinctive and outstanding optical characteristics. Nevertheless, the energy transfer process occurring among various colored QDs, known as Förster resonance energy transfer (FRET), results in a notable redshift in fluorescence emission, restricting the precise control of photoluminescence spectra in fabricated devices. This study presents a dual-impact technique to enhance the stability of CdSe/ZnS colloidal QDs while also preventing the FRET process. This is achieved by encapsulating the QDs within silica (SiO2) and ethylene-vinyl acetate (EVA) films. The research features two distinct encapsulation methods: enveloping multiple QDs within a SiO2 matrix (MQD) and adsorbing QDs onto SiO2 spheres as a shell (SQD and SQDS). Those hybrid structures are successfully fabricated with their nanostructure, chemical composition, and optical properties extensively analyzed. Moreover, the photo-physical properties of QDs/SiO2/EVA hybrid composite films and their impact on blue lightemitting diodes (LEDs) and White-LEDs have been conducted. Among those formulations explored, the MQD/EVA films stand out, displaying natural sunlight color emission with a color temperature of 4214 K, a color coordinate at (0.37, 0.37), and significant improvements in chromatic and thermal stability under high driving power. The successful integration of high-molecular-weight polymers and SiO2 coatings highlights the effectiveness of this approach in producing robust, high-quality QD-polymer film composites, making them ideal candidates for display technologies.

Monolithic full-color micro-LED displays featuring three-dimensional chip bonding and quantum dot-based color conversion layer

What we believe to be a novel fabrication process for monolithic full-color (RGB) micro-LED (µLED) display technology, featuring three-dimensional (3D) and quantum dot (QD)-based color conversion layer, has been proposed. This method offers advantages such as a wide color gamut, high pixel density, high yield, and low cost. A 16 × 16 passive matrix (PM) RGB µLED array, with a pitch size of 80 µm and a pixel density of 328 pixels per inch (PPI), has been successfully realized using flip-chip bonding technology. When measuring the electroluminescence (EL) spectra of the green and red pixels with the addition of color filters, the color gamut can achieve a maximum of 124% of the National Television System Committee (NTSC) standard. Additionally, this process significantly reduces the risk of damage to the QD film during photolithography compared to using two different colored QDs for RGB µLED arrays. The proposed manufacturing process shows considerable promise for commercialization.

Ultra‐Stable and Bright Pure‐Red Perovskite Nanocrystals for Backlit Displays

AbstractMetal halide perovskite nanocrystals (NCs) have emerged as an alternative to conventional phosphors for wide color gamut displays. However, the issues of poor stability and low emission efficiency of pure‐red CsPbBrxI3‐x NCs set an obstacle to their practical application. Herein, the synergistic effect of Mn doping and mesoporous SiO2 sealing is reported through in situ formation of Mn‐doped NCs into mesoporous SiO2 nanospheres (MnNCs@SiO2) to structurally and spatially stabilize the perovskite NCs for bright and stable pure‐red emitter. The large bonding energy of Mn‐halogen effectively suppresses the halide vacancy defects, prompting the highest photoluminescence quantum yield (PLQY) up to 84% (634 nm) among the pure‐red composite analogs. More importantly, the nanocrystal structure stability is fundamentally improved by the enhanced formation energy with Mn doping, together with the spatial isolation by SiO2 nanospheres. The MnNCs@SiO2 films exhibit impressive stabilities against high‐temperature heating, thermal cycle test, UV irradiation, water, and acid/alkali erosion, representing one of the most stable pure‐red perovskite emitters. By integrating fabricated all‐perovskite CsPbX3 single color conversion film into the liquid crystal display (LCD) modules, a wide color gamut of 128% of NTSC is achieved, enabling an excellent color rendition for high‐saturation object colors toward practical applications.

Preparation and properties of tellurite glass-based CsPb(BrCl)3@glass fluorescent film for a white light emitting diode color converter

Perovskite nanocrystal glass has the advantages of narrow-band emission, easy tuning, and stable structural, physical, and chemical properties, and can be used to mix with other colored materials for white light modulation. The current white light mode widely adopts the packaging method of blue light chip and yellow phosphor, which has the problem of a blue-yellow cavity and low light quality. In this work, the central wavelength of CsPb(BrCl)3 can be adjusted continuously ranging from 463 nm to 486 nm by adjusting the relative ratio of bromine to chlorine in nanocrystals. On the basis of the previous design of YAG:Ce phosphor-in-glass, perovskite nanocrystal glass powder as a color compensator was introduced into the tellurite glass matrix to form a doubly encapsulated system by low-temperature co-sintering. The yellow phosphor and perovskite nanocrystal glass maintain good structural integrity in the glass matrix. By combining the double-package fluorescent material with the blue chip, the continuous adjustment of chromaticity coordinates along the saddle line is realized, and the color-rendering index is also improved to 81.3.

Multishell Silver Indium Selenide-Based Quantum Dots and Their Poly(methyl methacrylate) Composites for Application in Red-Light-Emitting Diodes.

In this work, the production of novel multishell silver indium selenide quantum dots (QDs) shelled with zinc selenide and zinc sulfide through a multistep synthesis precisely designed to develop high-quality red-emitting QDs is explored. The formation of the multishell nanoheterostructure significantly improves the photoluminescence quantum yield of the nanocrystals from 3% observed for the silver indium selenide core to 27 and 46% after the deposition of the zinc selenide and zinc sulfide layers, respectively. Moreover, the incorporation of the multishelled QDs in a poly(methyl methacrylate) (PMMA) matrix via in situ radical polymerization is investigated, and the role of thiol ligand passivation is proven to be fundamental for the stabilization of the QDs during the polymerization step, preventing their decomposition and the relative luminescence quenching. In particular, the role of interface chemistry is investigated by considering both surface passivation by inorganic zinc chalcogenide layers, which allows us to improve the optical properties, and organic thiol ligand passivation, which is fundamental to ensuring the chemical stability of the nanocrystals during in situ radical polymerization. In this way, it is possible to produce silver-indium selenide QD-PMMA composites that exhibit bright red luminescence and high transparency, making them promising for potential applications in photonics. Finally, it is demonstrated that the new silver indium selenide QD-PMMA composites can serve as an efficient color conversion layer for the production of red light-emitting diodes.

Energy Transfer‐Assisted Color Conversion of Persistent Mechanoluminescence in RhB@SiO2/SrAl2O4:Eu,Dy System for Multilevel Information Encryption

AbstractPersistent mechanoluminescence (PML) is highly desirable for its ability to overcome transient‐emitting behavior, but its applications are hindered by the limited emission wavelengths. Herein, a universal chemical interlinkage‐assisted efficient energy transfer (ET) strategy is introduced to achieve color conversion from green to red in traditional PML materials. A straightforward chemical route to create the RhB@SiO2/SAOED system is established via covalent chemical interlinkage by depositing mesoporous silica‐encapsulated Rhodamine B (RhB) nanoparticles (RhB@SiO2) onto SrAl2O4:Eu, Dy (SAOED) particles. The resulting system exhibits a high ET efficiency of 53.5%. The multicolor PML of the RhB@SiO2/SAOED system remains visible to the naked eye for exceeding 28 s after mechanical stimulation. With this unique PML behavior, the RhB@SiO2/SAOED system demonstrates the potential applications ranging from visualized reading activities to multi‐mode anticounterfeiting. This universal PML color‐conversion strategy provides a new approach to high‐performance mechanical light energy‐conversion systems and may further inspire more diverse functional applications of classical PML materials.

A Novel PiGF@Diamond Color Converter with a Record Thermal Conductivity for Laser-Driven Projection Display.

High-brightness laser lighting is confronted with crucial challenges in developing laser-excitable color converting materials with effective heat dissipation and super optical performance. Herein, a novel composite of phosphor-in-glass film on transparent diamond (PiGF@diamond) is designed and fabricated via a facile low-temperature co-sintering strategy. The as-prepared La3Si6N11:Ce3+ (LSN:Ce) PiGF@diamond with well-retained optical properties of raw phosphor shows a record thermal conductivity of ≈599 W m-1 K-1, which is about 60 times higher than that of currently well-used PiGF@sapphire (≈10 W m-1 K-1). As a consequence, this color converter can bear laser power density up to 40.24 W mm-2 and a maximum luminance flux of 5602lm without luminescence saturation due to efficient inhibition of laser-induced heat accumulation. By further supplementing red spectral component of CaAlSiN3:Eu2+ (CASN:Eu), the PiGF@diamond based white laser diode is successfully constructed, which can yield warm white light with a high color rendering index of 89.3 and find practical LD-driven applications. The findings will pave the way for realizing the commercial application of PiGF composite in laser lighting and display.

Factors Influencing the Effects of Triticale on Laying Hens’ Performance: A Meta-Analysis

Multiple studies have yielded conflicting findings regarding the impact of incorporating triticale as a feed ingredient on laying hens’ production parameters. This article used a meta-analysis to assess the factors influencing its effects on layers’ performance. According to the PRISMA guidelines, articles examining the influence of triticale on layers’ egg production (EP), egg weight (EW), egg yolk color (EYC), feed intake (FI), and feed conversion ratio (FCR) were identified across Google Scholar, PubMed, and Science Direct. As a result, six articles were selected and categorized into 16 experiments for inclusion in our meta-analysis. Overall, the trim-and-fill method indicated that triticale had comparable effects to conventional cereals on the performance of laying hens. However, the meta-ANOVA emphasized that the Hy-Line Brown hen strain and Joesong and Juanilo triticale strains induced the best laying hen performance. Moreover, the meta-regression emphasized a positive correlation between the triticale inclusion percentage and the EW in Juanilo triticale diets and a negative correlation between the triticale inclusion percentages and the EYC in the triticale and laying hens strains studied. Therefore, this meta-analysis makes a valuable contribution to comprehending the factors that may influence the effects of triticale on the performance of layers.

Stable colour conversion layer with enhanced conversion efficiency by incorporating nanoparticles for micro-LED display application

Due to their promising optical performance, micro-light emitting diodes (micro-LEDs) based on colour conversion layer (CCL) have garnered significant attention as the next-generation display technology. However, fabricating CCL with excellent conversion efficiency (CE) with minimal blue light leakage for miniaturized sub-pixel designing is still in its infancy. Herein, we have demonstrated CCL of a thickness (<3.5 μm) based on an organic-inorganic hybrid system incorporated with Titanium dioxide (TiO2) and Zinc Oxide (ZnO) Nanoparticles (NPs) with high CE. The inclusion of the NPs enhances the absorption of blue light within the CCL. We further combined the CCL with a colour purification filter to mitigate blue light leakage, which recycles blue light and suppresses blue light loss, resulting in improved CE. Specifically, we achieved a CE of 83.80 % for the green CCL and 66.97 % for the red CCL. Subsequently, full-colour arrays with a pixel size of 4 μm × 4 μm were successfully patterned and fabricated based on reduced thickness and improved optical performance using NP-doped CCL. This paves the way for cost-effective higher-resolution micro-LED displays for various applications.

Behaviour quantification of Sm3+ in borotellurite glass phosphors for warm-colour illumination

Lighting in unconventional environments is closely related to eye health and circadian rhythms, making it essential for warm-colour light sources to align with technological advancements in solid-state lighting. Herein, warm light in spectral region over 550 nm is realised in Sm3+ doped multicomponent borotellurite (MBT-Sm) glass phosphors as colour converters for LEDs/LDs and their luminescent behaviours are quantified in detail. MBT-Sm glass phosphors standout for their high transparency and the large absorption/emission cross-section, with high quantum efficiency of 84.1 % and quantum yield of 19.15 % under violet LED excitation, and a high luminous flux of 3.33 lm under 50 mW laser. Remarkably, it not only possesses superior colour performance with the correlated colour temperature below 2000 K and colour purity up to 99.8 %, but also shows excellent heat resistance of luminescence. MBT-Sm glass phosphors show promising applications as colour conversion materials in innovative lighting technology.

High performance composite phosphor-in-glass film for laser-driven warm white light on patterned sapphire substrate

Phosphor-in-glass film (PiF) based on sapphire substrate (SS) is a promising laser-driven color converter. Herein, by using an optimized silicon borate glass component, high-performance Y3Al5O12:Ce3+ PiFs are successfully prepared on both flat sapphire substrate (FSS) and patterned sapphire substrate (PSS) surfaces. Compared with planar structure of FSS, PSS has a periodic arrangement of conical structures on its surface, which effectively increases the contact area between the PiF and the substrate by approximately 56%, thereby forming a more robust film composite structure. The blue laser light is affected by the structure of PSS and produces a typical diffraction effect, which realizes the dispersion of the convergent beam. This significantly expands the laser spot on PSS-PiF and improves the uniformity of light. The saturation power density of PiF-PSS (6.29 W/mm2) is found to be 91% higher than that of PiF-FSS, while maintaining a high luminous efficiency (220 lm/W) and a low correlated color temperature (4500 K). Finally, the thermal quenching mechanism of PiF with different substrate surface morphologies is compared and analyzed. The present results provide important support for designing the interface structure between SSs and PiF to achieve higher efficiency and higher saturation threshold for warm white light.

An Intelligent Moving Object Segmentation Using Hybrid IFCM-CSS Clustering Model

In this study, a novel hybrid deep clustering approach is proposed for the effective moving object segmentation. Initially, the data is collected, and the keyframe selection is performed using the threshold-based Kennard–Stone method. Then, the preprocessing step involves noise filtering using bilateral wavelet thresholding and binary color conversion. The blob detection is performed using normalized Laplacian of Gaussian. Finally, the segmentation of moving objects is performed using a hybrid clustering approach called improved fuzzy C-mean (IFCM) clustering with chaotic salp swarm (CSS) optimization algorithm (Hybrid IFCM-CSS). The overall evaluation is done in MATLAB. The performance of the hybrid IFCM-CSS is compared to other approaches based on some measures. The proposed Hybrid IFCM-CSS achieves the highest precision of 0.971, using the SBM-RGBD dataset.

Efficient white light-emitting electrochemical cells based on quantum-dot color conversion layers with high EQE >20 %

Solid-state light-emitting electrochemical cells (LECs) offer promising benefits, including simple device architecture, low operating voltage, and insensitivity to electrode work functions. These advantages make them highly suitable for low-cost display and lighting applications, with significant potential for widespread adoption. However, great challenges remain in realizing stable and efficient white LECs. In this work, the blue LECs integrated with red or yellow/red quantum-dot (QD) color conversion layers (CCLs) are shown to achieve efficient and stable white emissions. When the blue LECs are combined with red QD CCLs, they achieve an external quantum efficiency (EQE) exceeding 20 % at a low current density of 0.003 mA cm−2. Alternatively, the blue LECs integrated with yellow/red QD CCLs deliver white emissions with a low CCT <2500 K and a high CRI up to 93 while the peak EQE at a low current density of 0.005 mA cm−2 still remains high (>16 %). The data effectively showcase that efficient and stable white emission can be achieved through partial energy down-conversion from the blue LECs to the QD CCLs, and the proposed white light sources are potential candidates for lighting applications.

Recent Progress of Quantum Dots Light-Emitting Diodes: Materials, Device Structures, and Display Applications.

Colloidal quantum dots (QDs), as a class of 0D semiconductor materials, have generated widespread interest due to their adjustable band gap, exceptional color purity, near-unity quantum yield, and solution-processability. With decades of dedicated research, the potential applications of quantum dots have garnered significant recognition in both the academic and industrial communities. Furthermore, the related quantum dot light-emitting diodes (QLEDs) stand out as one of the most promising contenders for the next-generation display technologies. Although QD-based color conversion films are applied to improve the color gamut of existing display technologies, the broader application of QLED devices remains in its nascent stages, facing many challenges on the path to commercialization. This review encapsulates the historical discovery and subsequent research advancements in QD materials and their synthesis methods. Additionally, the working mechanisms and architectural design of QLED prototype devices are discussed. Furthermore, the review surveys the latest advancements of QLED devices within the display industry. The narrative concludes with an examination of the challenges and perspectives of QLED technology in the foreseeable future.

Tackling toxicity and stability using eco-friendly metal-halide ion substituted perovskite nanocrystals for advanced display color conversion

In recent years organic–inorganic hybrid halide perovskites nanocrystals have made a remarkable impact in display color converting layer application. However, lead toxicity and stability issues always pose arduous challenges. In this regard, the incorporation of a suitable metal ion to reduce toxicity and enhance stability is a widely tested method. In this study, we used a simple ligand-assisted reprecipitation (LARP) technique to simultaneously introduce metal ion and halide ion substitution by synthesizing MAPb1-xZnxBr3-2xCl2x nanocrystals (NCs). Being eco-friendly with a smaller ionic radius than lead ion, zinc metal ion was chosen as a substitute. With the variation of Zn2+ concentration, the highest quantum yield of 95 % was recorded with an emission width of 21 nm. Temperature-dependent photoluminescence (PL) studies revealed the higher optical phonon-exciton interaction after Zn2+ incorporation leading to radiative transition in NCs. Variation of PL peak energy with temperature revealed the reduced thermal chromaticity of Zn2+ incorporated NCs making them suitable for display application. Further, these NCs maintained a stable cubic structure and luminescence up to 150 °C, indicating higher thermal stability. The MAPb0.9Zn0.1Br2.8Cl0.2 (x = 0.1 or 10 mol%) NCs embedded in PMMA (poly (methyl methacrylate) polymer matrix coated LED emits narrow width, green light with color coordinate (0.15, 0.79), which is closer to green coordinate (0.17, 0.79) in Rec.2020. This helps to reproduce close to 97 % color gamut of Rec.2020. This research paves the way for finding less toxic and stable green light-emitting materials instead of cadmium-based molecules.

P‐152: The method of QD color conversion layer and pattern‐able Encapsulation with high thickness BM fabricated by inkjet‐printed process

This study develops a novel high‐thickness BM QD color conversion layer structure and a surface‐planarization process for QD materials after inkjet printing. This process reduces the height differences caused by the multi‐step exposure‐developing process. Following the fabrication of 8μm BM structure and 2μm CF structure, precise inkjet printing of QD materials is conducted within the 100ppi pixel area. we adjusted the surface energy of the color conversion layer by using an organic solution treatment to control the thickness profile and improve the color conversion efficiency. The printed QD materials are covered by a high‐transparency, low‐density polymer. After the color conversion layer component is encapsulated, reliability verification with a reliability assessment of 240 hours at RA (60℃ degrees, 90%RH) demonstrates an encapsulation effect where QD brightness retention rate remains above 90%.

P‐146: Research on Optical Model of Quantum Dot Color Conversion and Blue Backlight Device Architecture

Due to its high quantum yield and unique spectral characteristics, quantum dots (QDs) color conversion materials have attracted great attention in the application of luminescent display products. However, there is a lack of effective optical model for QD color conversion materials, especially for the propagation and distribution of light, when the QD ink contains scattering particles. In this paper, a full‐view optical model of QD conversion and blue backlight device architecture is established. The model can not only output the spectral information in the front view, but also predict the spectral information of the QD color conversion device in other different views. At the same time, the effects of QD concentration, thickness, particle size and refractive index on the luminous efficiency of the device structure are also studied by using this optical model. On the other hand, the influence of conversion efficiency of QD and EL backlight on the power consumption and lifetime of QD products is also studied by using this optical model. The model can realize the output of the optical influence on the future products by the parameters related to QD color conversion materials and backlight without actual device fabrication, which can greatly reduce time and labor cost.

P‐261: Late‐News Poster: Highly Efficient Color Conversion Layers Using Organic Nano‐dots

In this study, we report color conversion layers (CCLs) developed by new organic nano‐dots (ONDs). These ONDs, comprised of organic fluorescent materials and surfactant molecules, offer unique advantages such as tunable optical properties, high (100%) photoluminescence quantum yield (PLQY), and narrow (25‐35 nm) full‐width at half‐maximum (FWHM). Compared to the inorganic (InP) reference CCLs, OND CCLs exhibit almost double (80‐85%) color conversion efficiencies with good photo and thermal stability.