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Broadband white-light emission in metal halides has been intensely explored because of their facile solution processability, structural adjustability, and high color rendering index. However, the m...

Compared with conventional textile coloring with dyes and pigments, structural colored fabrics have attracted broad attention due to the advantages of eco-friendliness, brilliant colors, and anti-fading properties. The most investigated structural color on fabrics is originated from a band gap of multilayered photonic crystals or amorphous photonic structures. However, limited by the nature of the color generation mechanism and a multilayered structure, it is challenging to achieve structural colored fabrics with brilliant noniridescent colors and high fastness. Here, we propose an alternative strategy for coloring a fabric based on the scattering of Cu2O single-crystal spheres. The disordered Cu2O thin layers (

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.

Full-color matrix devices based on perovskite light-emitting diodes (PeLEDs) formed via inkjet printing are increasingly attractive due to their tunable emission, high color purity, and low cost. A key challenge for realizing PeLED matrix devices is achieving high-quality perovskite films with a favorable emission structure via inkjet printing techniques. In this work, a narrow phase distribution, high-quality quasi-two-dimensional (quasi-2D) perovskite film without a "coffee ring" was obtained via the introduction of a phenylbutylammonium cation into the perovskite and the use of a vacuum-assisted quick-drying process. Relatively efficient emissions of red, green, and blue (RGB) uniform quasi-2D perovskite films with high photoluminescence quantum yields were cast by the inkjet printing technique. The RGB monochrome perovskite matrix devices with 120 pixel-per-inch resolution exhibited electroluminescence, with maximum external quantum efficiencies of 3.5, 3.4, and 1.0% (for red, green, and blue light emissions, respectively). Furthermore, a full-color perovskite matrix device with a color gamut of 102% (NTSC 1931) was realized. To the best of our knowledge, this is the first report of a full-color perovskite matrix device formed by inkjet printing.

We report here on the strategy for the preparation of a series of electrochromic (EC) materials in green shades designed for camouflage purposes. This top-down post-synthetic modification provides access to new EC materials by fine modulation of the color of the surface-confined metalorganic monolayer pre-deposited on indium tin oxide screen-printed supports. Selective on-surface N-quaternization of the outer pyridine unit of the EC metal complex covalently embedded onto an enhanced surface area electrode results in a bathochromic shift of the absorbance signal as well as visual color change from blue to different shades of green. When assembled into solid-state EC devices (ECDs), the materials demonstrate high color differences between colored and bleached states and significant differences in optical density. Upon electrochemical switching, the ECDs initially featuring different shades of green become yellowish or clay. The accessible gamut of colors, fulfilling the requirements for chameleon-like camouflage materials, is able to mimic conditions of various natural environments including forests and sands. Notably, ECDs demonstrate high long-term durability (95% retention of the performance after 3300 cycles), fast coloration (0.6-1.1 s), and bleaching (1.2-3.3 s) times and outstanding coloration efficiencies of 1018-1513 cm2/C. Importantly, post-synthetic N-quaternization/color tuning does not deteriorate the performance of the resulting EC materials and devices as judged by cyclic voltammetry, spectroelectrochemistry, and electrochemical impedance spectroscopy. This work adds to the limited number of reports that explore color tuning of EC molecular layers via on-surface modification with the aim to access new non-symmetric materials. Notably, the facile and straightforward technology presented here allows the creation of green-colored EC materials that are difficult to prepare in other ways.

Inorganic electrochromic (EC) materials with vibrant multicolor change that are compatible with large-scale processing have been at the forefront of EC technology and are crucial in a wide range of applications, such as displays and camouflage. However, limited strategies are available to realize such inorganic materials, and challenges such as low color purity are yet to be overcome. Here, we demonstrate multilayered metal-dielectric metamaterials (MMDMs) as a new family of inorganics-based EC materials to achieve dynamic alternation among multicolors with high contrast and high color purity, which are structurally realized by significantly enhancing the confinement of the incident light in specific optical frequencies. This multilayer structure renders high reflectivity (75%), high quality factor (7.4), and a full width at half-maximum of 60 nm before coloration and presents a color gamut at least 40% wider than that of previously reported metamaterials after coloration, indicating good color quality.

Recently, quantum dots (QDs) are finding enormous application in white light emitting diodes (WLEDs) and WLEDs with high color rendition are in high demand. QD-WLEDs use different color (Red, Blue, Green) emitting QDs to obtain white light. Use of different color emitting QDs affect purity of white light due to self-absorption losses and QD degradation, in the long run affecting color rendering index (CRI) of WLEDs. Herein, we report low cost, environment friendly, open air atmosphere synthesis of single system white light emitting carbon dots (CDs) with broad emission bandwidth ranging 116 –143 nm and quantum yields (QY) ~ 5 – 13 % in colloidal state by modifying CD surface. Furthermore, carbon dot polymer phosphor (CD-PDMS phosphor) is fabricated which emits white light under UV illumination with a record emission bandwidth of ~ 154 nm and QY ~ 16 % in solid state. Moreover, CD-PDMS phosphor exhibit excellent color rendering index (CRI) ~ 96, the highest reported so far with CIE co-ordinates (0.31, 0.33) that are quite akin to pure white light. Such high performances are achieved due to high quality of CDs and CD-PDMS polymer phosphors by precise control in passivation/functionalization of nanoparticle surface. This work will set platform for the application of CD-phosphor based WLEDs in lighting systems.

To achieve high color rendering and proper color temperature, a red color converter is essential for phosphor-converted white lighting devices. CaAlSiN3:Eu2+ (CASN) is a highly suitable red phosphor for white light-emitting diodes. However, it can be hardly used in high-power laser lighting due to poor thermal/chemical performance of the phosphor/silicone resin mixture. A series of all-inorganic CASN-based phosphors (e.g., composite ceramic and phosphor-in-glass) were developed to avoid the use of resin. However, new challenges emerged: none of them showed sufficient luminous efficacy (i.e., >50 lm/W) and adequate saturation-threshold (i.e., >30 W or 10 W/mm2). Here, we report a facile fabrication of CASN/glass composite films using a simple and efficient blade-coating method. Upon 450 nm excitation, the resultant composite film presents a high internal quantum efficiency of ~83%, comparable to that of pristine CASN powder (~90%). When irradiated with a blue laser, the composite film shows a record high luminous efficacy of 82 lm/W. Furthermore, its saturation threshold was investigated in high power and high power density mode, respectively. When measured in high power mode, it shows a high saturation threshold over 29.7 W (1.75 W/mm2), thus achieving a high luminous flux of 1576 lm; when measured in high power density mode, it shows a saturation threshold of ~10.2 W/mm2 (1.13 W). With abovementioned excellent properties, the CASN/glass composite film has great potential for use in high-power and high color rendering laser lighting.

In this work, we examined the color tuning of units in the hidden layers of AlexNet, VGG-16 and VGG-19 convolutional neural networks and their relevance for the successful recognition of an object. We first selected the patches for which the units are maximally responsive among the 1.2 M images of the ImageNet training dataset. We segmented these patches using a k-means clustering algorithm on their chromatic distribution. Then we independently varied the color of these segments, both in hue and chroma, to measure the unit’s chromatic tuning. The models exhibited properties at times similar or opposed to the known chromatic processing of biological system. We found that, similarly to the most anterior occipital visual areas in primates, the last convolutional layer exhibited high color sensitivity. We also found the gradual emergence of single to double opponent kernels. Contrary to cells in the visual system, however, these kernels were selective for hues that gradually transit from being broadly distributed in early layers, to mainly falling along the blue-orange axis in late layers. In addition, we found that the classification performance of our models varies as we change the color of our stimuli following the models’ kernels properties. Performance was highest for colors the kernels maximally responded to, and images responsible for the activation of color sensitive kernels were more likely to be mis-classified as we changed their color. These observations were shared by all three networks, thus suggesting that they are general properties of current convolutional neural networks trained for object recognition.

We tested whether similarity between events triggers adaptive biases in how those events are remembered. We generated pairs of competing objects that were identical except in color and varied the degree of color similarity for the competing objects. Subjects ( N = 123 across four experiments) repeatedly studied and were tested on associations between each of these objects and corresponding faces. As expected, high color similarity between competing objects created memory interference for object–face associations. Strikingly, high color similarity also resulted in a systematic bias in how the objects themselves were remembered: Competing objects with highly similar colors were remembered as being further apart (in color space) than they actually were. This repulsion of color memories increased with learning and served a clear adaptive purpose: Greater repulsion was associated with lower associative-memory interference. These findings reveal that similarity between events triggers adaptive-memory distortions that minimize interference.

Conventional white lightings based on light-emitting diodes (LEDs) lack deep red, which is responsible for their low color rendering index (CRI). To apply red quantum-dot (QD) caps is one way to improve the color-rendering property of white LEDs. Red QD caps were fabricated using CdSe/ZnS QDs in the acrylic resin matrix and applied to conventional white LED lighting, which clearly showed a significant increase in the CRI, especially R9 associated with the strong red. Optical simulation was carried out to find out the optimized structure of the QD caps. The CRI increased while the optical efficiency decreased as the color conversion efficiency increased, which suggested that there should be a compromise between the two properties. It was found that to form a non-absorbing optical cavity in the QD cap was an effective way to achieve high CRI values while maintaining a moderately good optical efficiency.

Quantum dot light-emitting diodes (QLEDs) show great potential in high-definition displays due to their narrow emission and high color purity. However, the imperfect quantum dots (QDs) with high tr...

Development of multicolor-emitting upconversion nanoparticles (UCNPs) is of significant importance for applications in optical encoding, anti-counterfeiting, display, and bioimaging. However, realizing the orthogonal three-primary color (TPC) upconversion luminescence in a single nanoparticle remains a huge challenge. Herein, we have rationally designed core-multishell-structured NaYF4 UCNPs through regulating the dopant concentration, composition of luminescent layers, and shell position and thickness, which are capable of emitting red, green, and blue luminescence with high color purity in response to ternary near-infrared quadrature excitations (1560/808/980 nm). Moreover, their high color purity is well retained with varying excitation power densities. This orthogonal TPC emissions property of such UCNPs endows them with great promise in the field of security. As a proof-of-concept, we have demonstrated the feasibility of combining such UCNPs with MnO2 nanosheets for information encryption and decryption. This work not only offers a new way to achieve TPC upconversion luminescence at a single nanoparticle level but also broadens the scope of application for security protection.

A simple device structure adopting double emitting layers (EMLs) for white organic light-emitting diodes (WOLEDs) is described. The white emission is composed of blue emission from an Ir(III) complex in the blue EML and green/red emission from a single tetradentate Pt(II) complex Pt–X-4 in the green/red EML. High color rendering index (CRI) of 81 and high external quantum efficiencies of up to 19.85% are achieved for this WOLED. In addition to the broad emission spectrum and high efficiency, the short emission lifetime of Pt–X-4 in the aggregate form enables a high luminance of nearly 1 00 000 cd m−2 and low efficiency roll-offs of 2.1% and 11% at 1000 and 10 000 cd m−2, respectively. The simple device structure with high efficiency at high luminance and decent CRI value renders this WOLED a potential candidate for next-generation illumination devices.

Due to the limited training data, current data-driven algorithms, including deep convolutional networks (DCNs), are susceptible to training data that cannot be applied to new data directly. Unlike existing methods that are trying to improve model generation capability using limited data, we introduce a learning-based image translation method to generate data that share the same characteristics of target data. The low-resolution panchromatic satellite images are converted into high-resolution color images through interpolation and colorization with the proposed symmetric colorization network (SCN). Experiments on a very-high-resolution (VHR) dataset show that images generated by our SCN are with both quantitatively and qualitatively high color fidelity. Furthermore, we also demonstrate that high extraction accuracy is retained during the model transferring from aerial to satellite images. For pre-trained feature pyramid network (FPN), compared to the performance on raw panchromatic images, the interpolated and colorized images increase 305.7% of recall (0.929 vs. 0.229), 78.2% of overall accuracy (0.768 vs. 0.431), 132.5% of f1-score (0.851 vs. 0.366), and 230.8% of Jaccard index (0.741 vs. 0.224), respectively.

As is well known, a way to obtain a high color resolution and saturation of a liquid crystal display and thereby obtain a higher visual accuracy and comfort in the coming 5G era remains an urgent challenge. In the present study, a new type of phosphor composite material doped with Ln3+ ions provides a promising alternative to the color filters used in White light-emitting diodes (WLEDs), achieving a better performance regarding the realization of a wider color gamut. The advantages of this composite material are illustrated through an abundant phase and morphology analysis along with a discussion regarding the X-ray photoelectron spectroscopy of the valence bond of Ce ions, which maintain the luminescence properties of the phosphor while providing a stable and solid amorphous environment. An improved spectral performance was obtained through color filtering at 580 nm along with the regulating effects of red, green, and blue emissions according to the doped Ln3+ ions. Notably, we fabricated a high-performance WLED based on a Ln3+-doped PiG with a correlated color temperature of 5037 K, color rendering index of 72.8, and high color gamut of 91.97%, providing a new choice for the development of luminescence materials with a high color resolution and saturation.

Objective: This study was aimed to investigate the muscle-specific beef color stability at normal and high ultimate pHs.Methods: The impact of muscle (Longissimus lumborum [LL] vs psoas major [PM]) and pH (normal ultimate pH [Np] vs high pH dark cutting beef [Hp]) on color stability, indicated by basic color traits, metmyoglobin reducing activity (MRA) and oxygen consumption (OC), as well as the lipid oxidation, were determined over 7 days of display at 4°C.Results: Hp-LL had the highest pH (6.92), followed by Hp-PM (6.01), Np-PM (5.76), and Np-LL (5.52). Hp-LL had increased (p*, chroma and % oxymyoglobin during display. Hp-LL also had the highest metmyoglobin (MMb) reducing activity and OC among all the samples, thus, the greatest color stability, although very dark throughout storage, with lowest values for lightness (L*) and yellowness (b*). Np-LL also exhibited relatively high color stability, as a result of its lower % MMb and OC and higher MRA than psoas muscle samples. The 0.2 unit difference of the pH between Hp and Np psoas muscle, resulted in the difference of the color intensity, not the color stability. Interestingly, high pH psoas muscle (Hp-PM) did not have better color stability than Np-PM, and in fact had lower color stability than even Np-LL. The similar level of OC and lipid oxidation cannot explain the difference in color stability between Hp-PM and Np-LL.Conclusion: The Hp does not always show better color stability compared with Np beef, which depends on the muscle type. The balance of MRA and OC is important to keep the color in great intensity and stability in the meantime.

BACKGROUND AND OBJECTIVES To demonstrate that high color fidelity light-emitting diode (LED) sources are preferred by dermatologists for the evaluation of patients during standard-of-care, outpatient visits when compared to low color fidelity LED sources similar to fluorescent lighting. STUDY DESIGN/MATERIALS AND METHODS Three different LED sources were installed in exam rooms at a single, academic, medical institution (low color fidelity [82 color rendering index (CRI)] similar to fluorescent lighting, and high color fidelity [97 CRI and 96+red CRI]). A cross-sectional survey study was conducted in three parts. Naturalness (i.e. ability to reproduce natural, daylight conditions), effectiveness, color contrast, comfort, and overall performance of each LED source were rated on a 5-point scale from 0 to 4 with 0 being the worse, and 4 being the best. The first part included a survey of board-certified dermatologists (n = 3) assessing their visual experience while clinically evaluating a subset of patients during standard-of-care outpatient visits. The second survey was completed by dermatologic medical providers (n = 55) at three separate monthly departmental Grand Rounds sessions in which standardized patients were evaluated with the LED sources. Lastly, patients (n = 75) finished a survey assessing the comfort level of the LED sources. RESULTS In the first part of the study, all dermatologists significantly preferred the high color fidelity sources over low color fidelity sources based on all five evaluation criteria, with two preferring the 97 CRI LED source overall, while the third dermatologist favored 96+red CRI. Assessments provided by the 55 participants at Grand Rounds demonstrated that the 97 CRI was most "liked." Patients also preferred the high color fidelity LED source, reporting the 96+red CRI source was the "most comfortable." CONCLUSION Dermatologists, dermatologists-in-training and mid-level providers significantly prefer high color fidelity LED sources for outpatient evaluation of dermatologist patients in enclosed spaces, rating them the more natural, effective, comfortable, and providing superior color contrast than low color sources. Patients also favor high color fidelity LED sources as being the most comfortable in the clinic room. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Hyperfluorescence has received significant attention as a promising strategy to design organic light-emitting diodes (OLEDs) with high color purity and enhanced stability. In this approach, emitter...

Tetrabenzocorrolazine dyes with high color strength and broad absorbance derived from a phthalocyanine moiety were designed and synthesized for a color filter on an array-mode black matrix of low dielectric constant. The prepared tetrabenzocorrolazine dyes focused the absorbance of phthalocyanine further into the visible light range so that the color was considerably closer to black, while making it easier to introduce an axial substituent in the vertical direction to the dye main body, thereby markedly improving its solubility in industrial solvents. Upon mixing with a perylene dye of 450-550 nm absorbance and a thermosetting resin composition, dye-based black matrix films with high optical density values, associated with superior light shielding capability, were fabricated. The prepared black matrix films not only ensured thermal resistance by allowing easy intermolecular cohesion but also served as an insulating membrane that did not interfere with the thin film transistor electric signals, exhibiting a value of 3-5 when dielectricity was measured as the most critical factor for the color filter on array mode display panels.

A series of K2MnF6/KHF2 red phosphors were prepared through a low temperature way and their morphology and photoluminescence (PL) properties were investigated. The as-prepared phosphor shows an int...

Thermally activated delayed fluorescence (TADF) sensitization of fluorescence is a promising strategy to improve the color purity and operational lifetime of conventional TADF organic light-emitting diodes (OLEDs). Here, we propose a new design strategy for TADF-sensitized fluorescence based on acrylic polymers with a pendant energy-harvesting host, a TADF sensitizer, and fluorescent emitter monomers. Fluorescent emitters were rationally designed from a series of homologous polycyclic aromatic amines, resulting in efficient and color-pure polymeric fluorophores capable of harvesting both singlet and triplet excitons. Macromolecular analogues of blue, green, and yellow fourth-generation OLED emissive layers were prepared in a facile manner by Cu(0) reversible deactivation radical polymerization, with emission quantum yields up to 0.83 in air and narrow emission bands with full width at half-maximum as low as 57 nm. White-light emission can easily be achieved by enforcing incomplete energy transfer between a deep blue TADF sensitizer and yellow fluorophore to yield a single white-emissive polymer with CIE coordinates (0.33, 0.39) and quantum yield 0.77. Energy transfer to the fluorescent emitters occurs at rates of 1-4 × 10

A pilot-scale filtration unit has been modified and operated at the Southern Regional Research Center of the US Department of Agriculture for scaled-up trials to test the efficacy of powdered activated carbon in the removal of color impurities from sugar beet extract (SBE). As a by-product of sugar beet processing, additional sucrose can be recovered from high color SBE by recycling it from the chromatography system back into the crystallization unit. Large amounts of color compounds can make this process unfeasible. Color and other impurities can be reduced prior to further processing into white refined sugar, by application of high surface area powdered activated carbon (PAC). Pilot-plant trials were undertaken to determine the feasibility of using PAC to adsorb both natural and process-induced colorants from SBE. Experiments were performed using a batch decolorization process to maximize color removal and determine optimal PAC distribution as either body feed or filter pre-coat. With initial colors at 4275 ± 114, 4256 ± 223 and 4774 ± 157 ICU for color measured at pH 4, 7 and 9, respectively, a target of 50% color removal was achieved using 4000 ppm on volume of PAC, with a recommended distribution of 75% as pre-coat in the filter and 25% as body feed in the feed tank. A 50/50 PAC distribution also reached the target color removal rate. A “merry-go-round” experiment was undertaken to simulate a semi-continuous process to achieve continuous color removal over time. Overall, PAC performance was slightly better for the removal of native sugar beet colorants than colorants produced during processing. Addition of PAC did not lead to significant sucrose losses nor affected the pH of beet extract.

Sm3+ ions activated BaGeTeO6 phosphors were firstly produced through a method of solid-state synthesis at high temperatures. X-ray diffraction pointed out the pure phase of BaGeTeO6 phosphors. Photoluminescence spectrum of BaGeTeO6:Sm3+ phosphor showed the strong red emission at 647 nm under 404 nm excitation, while the associated absorption peaks were in the near-ultraviolet area. The optimal doped concentration of BaGeTeO6:Sm3+ phosphor was found at 10 mol%. The Commission Internationale de L'Eclairage coordinates of BaGeTeO6:0.10Sm3+ were calculated to be (0.624, 0.375) and the color purity as high as 99.8%. White light-emitting diodes have been fabricated based on the InGaN chip with high color rendering index (CRI, Ra = 90) and good correlated color temperature (CCT = 5396 K). Therefore, Sm3+-doped BaGeTeO6 phosphors have potential application in the illumination field.

Displays play an extremely important role in modern information society, which creates a never-ending demand for the new and better products and technologies. The latest requirements for novel display technologies focus on high resolution and high color gamut. Among emerging technologies that include organic light-emitting diode (OLED), micro light-emitting diode (micro-LED), quantum dot light-emitting diode (QLED), laser display, holographic display and others, QLED is promising owing to its intrinsic high color gamut and the possibility to achieve high resolution with photolithography approach. However, previously demonstrated photolithography techniques suffer from reduced device performance and color impurities in subpixels from the process. In this study, we demonstrated a sacrificial layer assisted patterning (SLAP) approach, which can be applied in conjunction with photolithography to fabricate high-resolution, full-color quantum dot (QD) patterns. In this approach, the negative photoresist (PR) and sacrificial layer (SL) were utilized to determine the pixels for QD deposition, while at the same time the SL helps protect the QD layer and keep it intact (named PR-SL approach). To prove this method’s viability for QLED display manufacture, a 500-ppi, full-color passive matrix (PM)-QLED prototype was fabricated via this process. Results show that there were no color impurities in the subpixels, and the PM-QLED has a high color gamut of 114% National Television Standards Committee (NTSC). To the best of our knowledge, this is the first full-color QLED prototype with such a high resolution. We anticipate that this innovative patterning technique will open a new horizon for future display technologies and may lead to a disruptive and innovative change in display industry.

As an alternative to Cd-free quantum dots (QDs), graphene quantum dots (GQDs) have potential because of their various advantages, such as color tunability, nontoxicity, cost effectiveness, and phot...

Novel Sm3+-doped tellurate Bi4Sr3Te5O19 phosphors have been prepared through the solid-state reaction for the first time. The powder phase purity, particle morphology, and luminescence properties are analyzed in detail. Under the 405 nm excitation, the Bi4Sr3Te5O19:Sm3+ phosphors show orange-red emission with four typical peaks. The optimal doping concentration of Bi4Sr3Te5O19:xSm3+ is found at x = 0.02 mol and the critical transfer distance (Rc) is 21.08 A. The color purity of Bi4Sr3Te5O19:Sm3+ phosphors are as high as 99.9%. The commission international de l'Eclairage (CIE) color coordinates are in the orange-red region. Temperature-related photoluminescence spectra and the corresponding CIE color coordinates indicate the phosphors possess good thermal stability and stable color property. Besides, the internal quantum efficiency (IQE) of the Bi4Sr3Te5O19:0.02Sm3+ phosphor reached 17.23%. Thus, Bi4Sr3Te5O19:Sm3+ phosphors have great potential applications in abundant lighting and displays.

Summary Metal halide perovskites (MHPs) are being widely studied as a light-absorber for high-efficiency solar cells. With efforts being made throughout the globe, the power conversion efficiency of MHP solar cells has recently soared up to 25.2%. MHPs are now being spotlighted as a next-generation light-emitter as well. Their high color purity and solution-processability are of particular interest for display applications, which in general benefit from wide color gamut and low-cost high-resolution subpixel patterning. For this reason, research activities on perovskite light-emitting diodes (LEDs) are rapidly growing, and their external quantum efficiencies have been dramatically improved to over 20%. As more and more research groups with different backgrounds are working on these perovskite optoelectronic devices, the demand is growing for standard methods for accurate efficiency measurement that can be agreed upon across the disciplines and, at the same time, can be realized easily in the lab environment with due diligence. Herein, optoelectronic characterization methods are revisited from the viewpoint of MHP solar cells and LEDs. General efficiency measurement practices are first reviewed, common sources of errors are introduced, and guidelines for avoiding or minimizing those errors are then suggested to help researchers in fields develop the best measurement practice.

Quantum emitters capable of producing single photons on-demand with high color purity are the building blocks of emerging schemes in secure quantum communications, quantum computing, and quantum metrology. Such solid-state systems, however, are usually prone to effects of spectral diffusion (SD), i.e., fast modulation of the emission wavelength due to the presence of localized, fluctuating electric fields. Two-dimensional materials are especially vulnerable to SD by virtue of the proximity of the emitters to the outside environment. In this study we report measurements of SD in a single hexagonal boron nitride (hBN) quantum emitter on the nanosecond to second time scales using photon correlation Fourier spectroscopy. We demonstrate that the spectral diffusion dynamics can be modeled by a two-component Gaussian random jump model, suggesting multiple sources of local fluctuations. We provide a lower limit of ∼0.13 for the ratio of the emitter's coherence time (

Deep blue organic-emitting fluorophores are crucial for applications in white lighting and full color flat-panel displays but emitters with high color quality and efficiency are rare. Herein, novel tetraphenylbenzene (TPB) based deep blue AIE luminogens (AIEgens) with various donor units and the same acceptors of cyano groups are developed and used to fabricate non-doped deep blue and hybrid white organic light-emitting diodes (OLEDs). Benefiting from its high emission efficiency and high proportion of horizontally oriented dipoles in the film state, the non-doped deep blue device based on CN-TPB-TPA realizes a maximum external quantum efficiency of 7.27%, with low efficiency roll-off and CIE coordinates of (0.15, 0.08). Moreover, efficient two-color hybrid warm white OLEDs (CIEx,y = 0.43, 0.45) are achieved using CN-TPB-TPA as a blue-emitting layer and a phosphor doped host, which realize maximum current, power, and external quantum efficiencies of 58.0 cd A−1, 60.7 lm W−1 and 19.1%, respectively. This work provides a general strategy to achieve high performance, stable deep blue and hybrid white OLEDs by the construction of AIEgens with an excellent horizontal orientation.

A raw image captured by a color filter array (CFA), such as a Bayer pattern, is usually compressed after demosaicing with some processings (denoising, deblurring, tone-mapping, and so on). However, since photographers, designers, and high-end users prefer to work with the raw image sampled by CFA (referred to as “raw image”) directly, a raw image should be compressed before demosaicing. For effective raw image compression, this study introduces variable macropixel spectral-spatial transforms (VMSSTs), that can successfully decorrelate not only Bayer raw images but any other pure-color (RGB) ones. The proposed VMSSTs are designed by the following two steps: 1) intra-color decorrelation and 2) inter-color decorrelation. In lossless compression with JPEG 2000, compared with methods which do not use transforms, the VMSSTs reduced the average bitrates of three types of CFAs: from approximately 0.09 to 0.12 bpp for the modified Bayer CFA, from 0.25 to 0.65 bpp for the diagonal stripe CFA, and from 0.33 to 0.70 bpp for the Fujifilm X-Trans CFA due to their high color decorrelation efficiency. In addition, in lossy compression with JPEG 2000, compared with a rearranged method, the VMSSTs improved the average bitrates of the Bjontegaard delta by around 3.97%, 14.95%, and 18.65% for each CFA model, respectively. Although a data-dependent adaptive transformation, the Karhunen-Loeve transform (KLT), showed the best performance in lossy compression, the introduced VMSSTs have shown performances comparable to those of the KLT in lossless compression, despite their simple structures.

Solid-state white light-emitting diodes (WLEDs) based on carbon dots (CDs) have attracted broad attention due to their high brightness and environmental friendliness. However, the poor performance, including low efficiency and weak emission of red-emitting CDs, further hinder their application in WLED devices. Herein, we constructed one outstanding WLED device by combining carbon dots (blue emission and green emission) and Ag–In–Zn–S (AIZS) nanoparticles with red emission. Moreover, by adjusting the volume ratio of the three materials, the WLED showed a maximum color rendering index (CRI) of 97 and maintained a CRI value above 90 as the correlated color temperature (CCT) was tuned from 3387 to 8018 K. Meanwhile, the as-fabricated WLED devices showed excellent color rendering stability during the adjustment of working voltages from 3.0 V to 3.5 V. This work may provide one new avenue for the development of low-cost, environmentally friendly and high-performance CD phosphor-based WLEDs.