Excellent Color Research Articles

Interfacial Molecule Control Enables Efficient Perovskite Light‐Emitting Diodes

AbstractPerovskite light‐emitting diodes (PeLEDs) are emerging as promising candidates for new‐generation high‐definition displays with excellent color purity and low power consumption. Nevertheless, the massive defects at grain boundaries and severe interfacial exciton quenching are critical challenges that hinder the commercialization process of PeLEDs. Herein, a novel and feasible strategy of interfacial molecule control is demonstrated by employing a bifunctional material with abundant phosphine oxide groups to induce strong interaction and exciton management between the perovskite and electron‐transport layers (ETLs). This modification layer is capable of passivating the surface crystal defects and blocking the interfacial exciton transfer simultaneously, contributing to minimized energy loss at the interface. Consequently, the modified PeLEDs with green (at 513 nm), blue (at 488 nm), and red (at 666 nm) emissions achieve maximum external quantum efficiencies of 18.8%, 12.6%, and 12.3%, respectively. This study reveals the importance of interfacial molecule control for reducing the energy loss in PeLEDs.

Introducing Relatively Isolated In/Out‐Gap Bands in Cs2XCl6 (X = Sn, Hf, Zr, Ti) via B‐Site Substitution: A Route to Brighter Luminescence and Tunable Emission Wavelengths

AbstractBoth theoretical and experimental approaches are utilized to investigate the fluorescence mechanism of B‐site substituted Cs2XCl6 (A2BX6‐type perovskite, X = Sn, Hf, Zr, Ti), aiming to enhance the luminescence and tune the emission wavelengths. Using Te‐monosubstituted Cs2SnCl6 as a model system, thecomputational discovery that the introduction of out‐gap and in‐gap bands by Te can significantly enhance its transition dipole moment is reported. This is further experimentally confirmed, showing a single emission peak resulting from the radiative transition between the out‐gap and in‐gap bands. The broadening of the emission peak is attributed to self‐trapped exciton (STE), while additional absorption/excitation peaks arise from composition segregation. Additionally, the high‐throughput first‐principles calculations indicate that substituting B‐sites of Cs2XCl6 with Se, Te, Po, As, Sb, and Bi may also significantly enhance their light emission with the introduced bands. Thus, fine‐tuning the emission wavelengths by controlling the position of out‐gap and in‐gap bands through cation selection is proposed. Furthermore, tunable white‐light emission is achieved with excellent color stability by adjusting the Te and Bi composition in co‐substituted Cs2SnCl6 material. The findings highlight the potential of utilizing out‐gap and in‐gap bands to tune luminescence in this perovskite family for advanced device applications, including white‐light‐emitting diodes (WLEDs).

Reconstruction of Upper Third Defect of the Auricle by Conchal Cartilage Graft and Coverage by Postauricular Flap.

The defects of the upper third of the auricle are considered significant reconstructive challenges, as they require frequent operations with a high risk of morbidity at the donor site and result in unacceptable cosmetic abnormalities. Is to perform the reconstruction of a full-thickness auricular defect located in the upper third of the ear using a conchal cartilage graft with postauricular flap coverage, aiming to minimize both donor and recipient morbidity. The current study included 20 patients with unilateral upper-third auricular defects. The repair involved 2 components: a cartilage graft from the concha to provide structural support and a flap for coverage. Follow-up was conducted for 6 months after the operation. Successful outcomes were achieved in both subjective and doctors' assessments. Regarding subjective outcomes, 85% of the patients reported high satisfaction (P < .001). In terms of doctors' subjective assessment, 90% of the patients had excellent results (P < .001). Mild early and postoperative complications, if encountered, resolved spontaneously. The use of a combined conchal cartilage graft and postauricular flap in treating a full-thickness upper third auricular defect is safe and effective, with no major complications. The technique preserves the cosmetic and functional outcomes of the auricle, providing an excellent color match and minimal donor-site morbidity.

A novel red phosphor Sr3In2WO9: Eu3+ for WLEDs

A series of Sr3In2WO9: xEu3+ red phosphors were prepared using a solid-state reaction. The strongest excitation peak of Sr3In2WO9: xEu3+ appeared at 394 nm, and the strongest emission peak appeared at 612 nm. The concentration-dependent emission spectra show that the optimal doping concentration of Eu3+ ions is x = 0.30 for all Sr3In2WO9: xEu3+ samples and Eu3+ occupies the non-inverted centrosymmetric site. Analysis of the causes of concentration quenching, the dipole-quadrupole interaction in Sr3In2WO9: xEu3+ was determined to be the main cause. The thermal stability of the Sr3In2WO9: 0.30Eu3+ sample was analyzed, and it was found that the luminescence intensity of the Sr3In2WO9: 0.30Eu3+ was retained by 55.1 % at 423 K. The thermal quenching activation energy ΔE = 0.291 eV was calculated after the thermal quenching analysis. The calculated CIE chromaticity coordinate of Sr3In2WO9: 0.30Eu3+ is (0.6450, 0.3544), which are very close to the standard red light (0.667, 0.333) given by the National Television Standards Committee system. The color purity of all samples is above 95 %, and the associated color temperature is below 2400 K. The chromaticity coordinates of the encapsulated WLED point of (0.329, 0.388) with a lower correlation color temperature of 5841 K and excellent color rendering index of 88, which indicated the near-UV excited SIWO: Eu3+ red phosphor has great potential for application in the field of WLEDs devices.

Stability improvement of N-GQDs/AgNWs/PET based flexible electrochromic device for smart window application

The design and development of cost-effective and highly stable flexible transparent conductive electrodes (f-TCEs) is crucial for various optoelectronic applications. Herein, we report the fabrication of nitrogen-doped graphene quantum dot (N-GQD)-protected silver nanowire (AgNWs)-modified polyethylene terephthalate (PET) electrodes as f-TCEs (N-GQDs/AgNWs/PET). Furthermore, we fabricated flexible electrochromic devices (ECDs) for smart window applications using N-GQD/AgNW/PET as the f-TCE. The presence of N-GQDs on the AgNW/PET electrode improved the stability of the developed N-GQD/AgNW/PET-based flexible ECDs. The N-GQDs/AgNWs/PET-based flexible ECDs demonstrated an excellent coloration efficiency (ȠCE) of 42.7 cm2C−1 with an optical contrast of 45.4 %. Additionally, they demonstrated fast coloring and bleaching times of 6.9, and 5.7 s, respectively.

+Development of a modified route for the preparation of BiVO4/ZrO2 composite with tuned heterojunction in it for efficient near-infrared solar reflectance

Recent advancements in pigmentation technology have focused on the development of cost-effective routes to achieve high near-infrared (NIR) reflectivity, offering multifunctional and sustainable applications over conventional methods. Here, we have developed a modified route for the preparation of BiVO4/ZrO2 composite with tuned heterojunction in it. Several advanced techniques were employed to investigate the elemental composition, microstructure, band gap energy, particle size, electronic transition, and color characteristics of the composite. The band gap of BiVO4 was tuned to optimize its suitability for the efficient NIR solar reflections. N2 adsorption and desorption studies indicated that the composite had a typical microporous material behavior, categorized as a type IV isotherm. Thermogravimetric analysis (TGA) and differential thermogravimetry (DTG) revealed excellent thermal stability of the composite up to 800 °C. The equimolar ratio of the composite (1:1 BiVO4/ZrO2) composite demonstrated appreciable NIR solar reflectance, reaching 96%, and exhibited an intense yellow color with excellent color characteristics. Consequently, (1:1 BiVO4/ZrO2) composite holds significant promise as a material for the development of multifunctional, thermally stable, anti-corrosive, and energy-saving exterior cool roof applications.

Gonadal growth and qualitative color assessment of the sea urchin Paracentrotus lividus Lamarck, 1816 (Echinodermata: Echinoidae) of the Southeastern Mediterranean Sea

This study aims to investigate the gonadal growth and gonads qualitative color assessment of the sea urchin Paracentrotus lividus in the Southeastern (SE) Mediterranean coast off Egypt. A total of 1895 sea urchins were collected between 2017 and 2018, and their reproductive biology parameters were determined. The gonadosomatic index with the histological analysis revealed that P. lividus has two spawning seasons (spring – autumn). Females and males have four maturity stages; recovery, growing, mature, and spent. Mature oocytes and sperms were observed during autumn, winter, and spring, while nutritive phagocytes dominated the tissue of both ovaries and testes in the summer season. The sex ratio (F: M) was male-biased (1: 1.2). The smallest observed size of mature males was 19.10 mm TD (test diameter), whereas the calculated L50 was 26.2 mm. In females, the smallest observed size of a mature individual was 22.70 mm TD, and the calculated L50 was 33.5 mm TD. The qualitative color assessment of the gonads revealed the dominance of excellent and acceptable color throughout the year (83.93%), with maximum value during the resting and recovery periods, while, the occurrence of unacceptable color was linked to the maturation and spawning periods. The present findings would assist the decision makers to propose management strategies and regulations on the harvesting of P. lividus off the Egyptian Mediterranean coast.

Synthesis and characterization of Ba3MgTa2O9:xSm3+ orange-red phosphor with excellent color purity and superior color stability

Synthesis and characterization of Ba3MgTa2O9:xSm3+ orange-red phosphor with excellent color purity and superior color stability

An intelligent chitosan/gelatin film via improving the anthocyanin-induced color recognition accuracy for beef sub-freshness differentiation monitoring

A novel volatile amine-responsive food freshness smart film, CG-BAE, has been developed utilizing chitosan (CS) and gelatin (GL) as film substrates and butterfly pea flower anthocyanin extract (BAE) as the indicator. The pH value of the film-forming solution was found to significantly impact the physical properties, biogenic amine response sensitivity, and initial color of the film. The hydrogen bonding interaction between anthocyanins and the film matrix was identified as the main binding force, as confirmed by FT-IR spectroscopy and molecular docking simulation analysis. Notably, CG-BAE-2.0 films have demonstrated excellent color stability, antioxidant activity, and color responsiveness. The performance of the film in monitoring beef freshness was evaluated and proved clear differentiation between four stages: freshness, sub-freshness, onset of spoilage, and complete spoilage. The color change of the film was assessed using RGB values obtained from a smartphone App, reducing the difference in color recognition by individual naked eyes. Therefore, this work addresses the limitation that BAE-based intelligent films cannot be distinguished at the starting point of meat spoilage, and presents a promising approach to sub-freshness indication, opening new possibilities for food freshness differentiation monitoring.

Introducing Spiro-locks into the Nitrogen/Carbonyl System towards Efficient Narrowband Deep-blue Multi-resonance TADF Emitters.

The current availability of multi-resonance thermally activated delayed fluorescence (MR-TADF) materials with excellent color purity and high device efficiency in the deep-blue region is appealing. To address this issue in the emerged nitrogen/carbonyl MR-TADF system, we propose a spiro-lock strategy. By incorporating spiro functionalization into a concise molecular skeleton, a series of emitters (SFQ, SOQ, SSQ, and SSeQ) can enhance molecular rigidity, blue-shift the emission peak, narrow the emission band, increase the photoluminescence quantum yield by over 92 %, and suppress intermolecular interactions in the film state. The referent CZQ without spiro structure has a more planar skeleton, and its bluer emission in the solution state redshifts over 40 nm with serious spectrum broadening and a low PLQY in the film state. As a result, SSQ achieves an external quantum efficiency of 25.5 % with a peak at 456 nm and a small full width at half maximum of 31 nm in a simple unsensitized device, significantly outperforming CZQ. This work discloses the importance of spiro-junction in modulating deep-blue MR-TADF emitters.

Introducing Spiro‐locks into the Nitrogen/Carbonyl System towards Efficient Narrowband Deep‐blue Multi‐resonance TADF Emitters

AbstractThe current availability of multi‐resonance thermally activated delayed fluorescence (MR‐TADF) materials with excellent color purity and high device efficiency in the deep‐blue region is appealing. To address this issue in the emerged nitrogen/carbonyl MR‐TADF system, we propose a spiro‐lock strategy. By incorporating spiro functionalization into a concise molecular skeleton, a series of emitters (SFQ, SOQ, SSQ, and SSeQ) can enhance molecular rigidity, blue‐shift the emission peak, narrow the emission band, increase the photoluminescence quantum yield by over 92 %, and suppress intermolecular interactions in the film state. The referent CZQ without spiro structure has a more planar skeleton, and its bluer emission in the solution state redshifts over 40 nm with serious spectrum broadening and a low PLQY in the film state. As a result, SSQ achieves an external quantum efficiency of 25.5 % with a peak at 456 nm and a small full width at half maximum of 31 nm in a simple unsensitized device, significantly outperforming CZQ. This work discloses the importance of spiro‐junction in modulating deep‐blue MR‐TADF emitters.

Smart pH indicating functional fabric based on reversible acidichromic self-colored microparticles

Our study focuses on developing a novel wearable fabric with reversible acidichromic properties by dyeing it with self-colored hollow microparticles as polymeric dyes. To synthesize the pH-responsive chromophore, we introduced a self-synthesized 3-methyl-3-2,2′-dihydroxydiethylamine azobenzene (MDPD) to polyurethane microparticle shells. This prevented any dye leakage compared to conventional dye microcapsules. The self-colored microparticles exhibited an approximately spherical shape, with the particle size distribution ranging from 400 nm to 900 nm, peaking around 600 nm. By covalently bonding MDPD to the molecular chain of the polyurethane shell, we increased thermal stability and avoided dye leakage. We calculated the actual content of MDPD in the shell to be 3.84 %. To investigate the pH-responsive chromic mechanism of self-colored hollow microparticles, we characterized their color properties at various pH values. The polyester fabric dyed with pH-responsive self-colored microparticles showed a K/S value of up to 4.8. The dyed fabric exhibited a clear color change from yellow to rose red after decreasing the pH value, with a highly reversible mode, excellent color fastness, and aging resistance. Furthermore, we analyzed the combination mechanism of microparticles and polyester fabrics, highlighting the reversibility and large-area flexibility of pH-responsive microparticle dyed fabrics. The ability to accurately monitor pH levels in real-time using these fabrics opens new avenues for creating intelligent and responsive textile-based devices. As we continue our research and development, we aim to explore and maximize the potential of these fabrics, making them a valuable and innovative addition to the realm of wearable technologies.

Multicolor-tunable biomass thermochromic dyes utilizing tea polyphenols color developer for temperature-controlled linen fabric

Linen, an important industrial crop, is commonly used in the textile field. The development of temperature-controlled linen fabrics is important for the high-value utilization of cellulose-based industrial products. The linen fabrics with color and performance changes controlled by temperature are prepared via the vacuum impregnation process utilizing biomass three-component thermochromic dyes. Currently, three-component thermochromic dyes based on the bisphenol A (BPA) color developer have received special attention due to high saturation color and reversible color-changing performance. However, the toxicity and carcinogenicity of BPA limit its applications in security inks, decorative coatings, plastics, etc. Exploiting excellent and safe biomass color developers for three-component thermochromic dyes remains a challenge. Tea polyphenols (TP) are proposed as alternatives to BPA to prepare the blue, red, yellow, and green three-component thermochromic dyes. According to the laws of subtractive color mixing, multicolor-tunable thermochromic dyes are obtained by color matching of red, yellow, and blue dyes to span multiple shades. Biomass thermochromic dyes are adopted to fabricate temperature-controlled linen fabrics by the vacuum impregnation process. Temperature-controlled linen fabrics can change color reversibly between the original color and achromatic color. The color-changing occurs due to the ring opening and closing of leuco dyes triggered by the solid-to-liquid transition of solvent. The phase transition temperature of the thermochromic dyes absorbed on the linen fabric is 46 ℃. As the temperature increases, the contact angle of temperature-controlled linen fabrics decreases from 129° to 29°, resulting in a change from hydrophobic to hydrophilic with 49 J g−1 of thermal energy stored. The linen fabrics exhibit temperature-controlled changes in color, surface wettability, strength, and thermal insulation. This eco-friendly method with biomass thermochromic dyes for the preparation of color-changing linen fabrics provides a new approach, which is contributing to the development of cellulose-based smart color-changing textiles.

Fabrication of Al2O3[sbnd]GAGG:Ce composite ceramic phosphors with excellent color quality for high-power laser-driven lighting

The application of high-power laser-driven lighting is limited by the insufficient heat dissipation of phosphor converters and the poor color quality of white light. In this study, the Al2O3(Gd,Ce)3(Al,Ga)5O12 (Al2O3GAGG:Ce) composite ceramics were designed to improve thermal performance of phosphors, while maintaining excellent color rendering under high-power laser excitation. Dense composite ceramics were fabricated by pre-sintering at 1600 °C in air followed by HIP at 1700 °C through the investigation of the phase evolution and sintering process. The emission spectrum of GAGG:Ce shows a red shift of 31 nm and a high full width at half maximum (FWHM) of 128 nm. Meanwhile, the thermal conductivity was increased to 13.2 W·m−1K−1 by addition of Al2O3, which is 72% higher than that of single-phase GAGG:Ce ceramic. Therefore, warm white light with high color rendering index (CRI) of 71.4 and low correlated color temperature (CCT) of 4352 K was attained under excitation of high-power LDs.

Impurity doping effects and ecological friendly synthesis of cerium sulfide powders for enhanced chromaticity and color tunability

Red non-toxic and environmentally friendly γ-phase cerium sulfide powders have promising applications in the fields of coatings, outdoor displays and smart buildings. However, the development of an environmentally friendly preparation process and the improvement of production efficiency of cerium sulfide powders remain major challenges. In this study, eco-friendly γ-Ce2S3 powders with excellent color properties have been produced by adding ammonium thiocyanate to the precursor of cerium without H2S or CS2. The effect of impurities (mainly Ce2O2S) with different amounts on spectral properties of cerium sulfide powders has been studied through chemical and physical methods. In addition, the significance of impurity doping on the reaction synthesis was studied by combining detailed experimental characteristics with density functional theory calculations. The results show that the reduction of impurity content can greatly improve the chromaticity value of γ-Ce2S3 and change color from dark red to bright red.

Hybridization of short-range and long-range charge transfer excited states in multiple resonance emitter

Multiple resonance (MR) thermally activated delayed fluorescence emitters have been actively studied as pure blue dopants for organic light-emitting diodes (OLEDs) because of excellent color purity and high efficiency. However, the reported MR emitter, 2,5,13,16-tetra-tert-butylindolo[3,2,1-jk]indolo[1′,2′,3′:1,7]indolo[2,3-b]carbazole (tDIDCz) based on bis-fused indolocarbazole framework could not demonstrate efficient triplet-to-singlet spin crossover. In this work, we report two isomeric MR emitters designed to promote triplet exciton harvesting by reconstructing the electronic structure of tDIDCz. To manage excited states, strong electron donors were introduced at the 2,5-/1,6-position of tDIDCz. As a result, 2,5-positions managed tDIDCz shows long-range charge transfer characteristics while preserving the MR nature. Quantum chemical calculation demonstrates direct spin-orbit coupling by long-range charge transfer and spin-vibronic coupling assisted reverse intersystem crossing by short-range charge transfer simultaneously contribute to triplet-to-singlet spin crossover. Consequently, high performance blue OLED recorded a high external quantum efficiency of 30.8% at a color coordinate of (0.13, 0.13).

Ultrahigh-efficient material informatics inverse design of thermal metamaterials for visible-infrared-compatible camouflage

Multispectral camouflage technologies, especially in the most frequently-used visible and infrared (VIS-IR) bands, are in increasing demand for the ever-growing multispectral detection technologies. Nevertheless, the efficient design of proper materials and structures for VIS-IR camouflage is still challenging because of the stringent requirement for selective spectra in a large VIS-IR wavelength range and the increasing demand for flexible color and infrared signal adaptivity. Here, a material-informatics-based inverse design framework is proposed to efficiently design multilayer germanium (Ge) and zinc sulfide (ZnS) metamaterials by evaluating only ~1% of the total candidates. The designed metamaterials exhibit excellent color matching and infrared camouflage performance from different observation angles and temperatures through both simulations and infrared experiments. The present material informatics inverse design framework is highly efficient and can be applied to other multi-objective optimization problems beyond multispectral camouflage.

Digital ink‐jet printing of regenerated cellulose nanofibrous mats with reactive inks

AbstractThe versatility of nanofibres enables them to be used for various technological applications such as filtration, biomedicine and healthcare, composites, protective and functional textiles. Recently, in addition to the functional properties of electrospun nanofibrous mats, their aesthetic properties have been explored. Herein, attempts have been made to develop digital ink‐jet printing of regenerated cellulose nanofibrous mats with reactive inks. First, a cellulose acetate polymer was created to fabricate electrospun cellulose acetate nanofibrous mats, which were then converted into regenerated cellulose nanofibrous mats through deacetylation. Next, the cellulose nanofibrous mats were treated with an alkaline solution then coloured with four (cyan, magenta, yellow and black) commercially available reactive inks by a digital ink‐jet printing method using a piezoelectric digital ink‐jet printer. Various parameters were investigated, including the optimal concentration of the pretreatment agents, fixation temperature and time, colour yield and the absorbency of the electrospun nanofibrous mats. The digital ink‐jet printed cellulose nanofibrous mats exhibited excellent colour yield and colour fastness properties. Morphological analysis through scanning electron microscopy and chemical analysis through Fourier Transform–infrared were also carried out.

Cooling colors below ambient temperature

The colors of objects originate from reflection of light in certain directions and absorption of undesired light, producing substantial heating. Extensive efforts are expended to cool colorful objects to reduce their energy consumption. However, a strategy to cool colorful objects below ambient temperature while fully preserving their excellent color properties with high saturation and large viewing fields remains a significant challenge. Inspired by Morpho butterflies, we report a robust configuration consisting of a multilayer, disordered structure, and total reflection layer to cool colorful objects to overcome this challenge. Numerical simulations and experimental measurements demonstrated that our configuration can cool a class of colorful objects not only to a temperature of approximately 2°C below ambient temperature, but also with ultrahigh saturation (100%) and a wide range of viewing angles (±60∘). These colorful cooling films have significant potential for energy sustainability in buildings, vehicles, facilities, and equipment.

Effect of sodium ions doping on structure and spectral properties of γ-Ce2S3 microcrystals

Rare earth sulfides are environmentally friendly and have excellent physical optoelectronic properties and coloring applications. In particular, red γ-Ce2S3 is an important and popular inorganic optical functional material. However, it has become crucial to improve the production efficiency of γ-Ce2S3 and its color performance and stability. By adding ammonium thiocyanate to the precursor, eco-friendly γ-Ce2S3 with excellent color performance was produced in this study. In addition, the effect of different amounts of Na+ doping on the final product's purity and the effect of chroma value were systematically investigated. Results show that an increase in Na+ can effectively lower the synthesis temperature of γ-Ce2S3, improve production efficiency, and optimize color performance prior to saturation. Finally, using density functional theory, the influence of the vacancy structure of γ-Ce2S3 and the change of energy band after the addition of Na+ were calculated, and a detailed experimental characterization in conjunction with density functional theory calculation thoroughly explained the significance of ion doping for reaction synthesis.