Color Temperature Research Articles

An Artificial Intelligence-Assisted Flexible and Wearable Mechanoluminescent Strain Sensor System.

The complex wiring, bulky data collection devices, and difficulty in fast and on-site data interpretation significantly limit the practical application of flexible strain sensors as wearable devices. To tackle these challenges, this work develops an artificial intelligence-assisted, wireless, flexible, and wearable mechanoluminescent strain sensor system (AIFWMLS) by integration of deep learning neural network-based color data processing system (CDPS) with a sandwich-structured flexible mechanoluminescent sensor (SFLC) film. The SFLC film shows remarkable and robust mechanoluminescent performance with a simple structure for easy fabrication. The CDPS system can rapidly and accurately extract and interpret the color of the SFLC film to strain values with auto-correction of errors caused by the varying color temperature, which significantly improves the accuracy of the predicted strain. A smart glove mechanoluminescent sensor system demonstrates the great potential of the AIFWMLS system in human gesture recognition. Moreover, the versatile SFLC film can also serve as a encryption device. The integration of deep learning neural network-based artificial intelligence and SFLC film provides a promising strategy to break the "color to strain value" bottleneck that hinders the practical application of flexible colorimetricstrain sensors, which could promote the development of wearable and flexible strain sensors from laboratory research to consumer markets.

Construction and evaluation of a model for efficient identification of photothermal sensitivity of tobacco cultivars based on agronomic traits.

The photothermal sensitivity of tobacco refers to the degree to which tobacco responds to changes in light and temperature conditions in its growth environment, which is crucial for determining the planting area of cultivars and improving tobacco yield and quality. In order to accurately and effectively evaluate the photothermal sensitivity of tobacco cultivars, this study selected five cultivars and their hybrid combinations with significant differences planted under different ecological conditions from 2021 to 2022 as materials. The experiment was conducted in two locations with significant differences in temperature and light. We measured the agronomic traits and biomass of the experimental materials, and constructed an effective tobacco photothermal sensitivity evaluation model using principal component analysis, membership function, and regression analysis. The reliability of the model was evaluated by utilizing the photosynthetic characteristics, chlorophyll content, and antioxidant enzyme system activity of the experimental materials. The results showed that tobacco biomass is the most important principal component in agricultural traits, and the comprehensive evaluation model for tobacco photothermal sensitivity is: y = 0.4571y1 + 0.2406y2 + 0.1725y3, where the fitting coefficients R2 of y1, y2, and y3 are 0.945, 0.851, and 0.977, respectively; The photothermal sensitivity of the experimental materials was calculated using this model, and the comprehensive ranking of the 11 experimental materials is: G3 < G5 < G10 < G9 < G11 < G6 < G7 < G2 < G4 < G8 < G1. Conventional identification methods have found that G2, G4, G6, G7, G8, and G11 are sensitive materials, G3, G5, and G10 are insensitive materials, and G1 and G9 are intermediate materials. The consistency rate of the evaluation results of the two methods reached 90.91%. And there is a significant correlation between the agronomic traits selected in the model and the physiological indicators selected by conventional evaluation methods, providing a scientific basis for evaluating the light temperature sensitivity of tobacco cultivars using agronomic traits in this study. The results indicate that the photothermal sensitivity evaluation model established in this study provides an efficient, convenient, and reliable method for evaluating the photothermal sensitivity of tobacco.

Untypical tuneable emission activated by NIR radiation observed in gadolinium borate nanomaterials doped with Yb3+, Ho3+ and Ce3+ ions.

New luminescent nanoparticles with adjustable emission properties were synthesized via a hydrothermal method to investigate the effect of Ce3+ concentration on the tuneable emission properties of Yb3+/Ho3+ co-doped gadolinium borates. The synthesized samples' comprehensive structural and morphological analysis was conducted utilizing X-ray diffraction and transmission electron microscopy. To obtain highly crystalline nanoparticles GdBO3:Yb3+/Ho3+/Ce3+ characterized by intense and bright emission, they were annealed at 525°C and 925°C. Under the excitation of 972nm, the tunable yellow to green up-conversion (UC) emission was observed, while the Ce3+ concentration increased. This change correlated with a difference in the correlated color temperature from 4345K to 5442K, respectively. The untypical changes observed in the red-to-green (R/G) ratio, displaying a declining trend contrary to conventional expectations, allowed for the proposed mechanism for understanding their UC luminescence properties. The results obtained indicate that the Ce3+ doped GdBO3:Yb3+/Ho3+ nanoparticles demonstrate high application potential for anti-counterfeiting.

As virtual work becomes more prevalent, an important question arises: how do surface colors and light color temperature in a virtual environment impact creativity?

ABSTRACT Colors and light affect human emotions, and positive emotions encourage human creativity. To enhance student creativity, the appropriate surface colors and light color temperatures in a virtual environment must be determined. This study explores how color and light color temperature in a virtual space impact student creativity. In Experiment 1, color and light color temperature were chosen by surveying 189 architect students who answered questionnaires after watching 10 pictures of a workspace with five different surface colors and two light color temperatures. The workspace with white walls and daylight had the highest mode scores for positive emotion perception. Experiment 2 assessed the creativity of 46 participants using virtual reality (VR) and the alternative uses test (AUT). Participants were divided into two groups of 23. The first group was exposed to white surfaces under daylight. The second group interacted with red surfaces under warm light. The results indicate that a space with white surfaces and daylight significantly enhances creativity, specifically in originality component, compared to a space with red surfaces and warm light. Using light colors and daylight in VR workspace design may promote positive emotions and enhance creativity.

Simple synthesis of AgInS2/ZnS core/shell quantum dots with wide tunable emission wavelength for white light-emitting diodes

Phosphor with efficient and broad range emission is necessary for lighting applications. I-III-VI group quantum dots (QDs) have the advantages of non-toxic composition and large adjustable spectrum range, and have potential applications in the field of lighting. However, the efficient luminescence of these QDs at shorter wavelengths still needs further study, which is crucial for the development of high color rendering index white light LED devices (WLEDs). In this work, wide visible range emitting AgInS2/ZnS QDs with broad band and high luminous efficiency were obtained by altering the Ag/In ratios and Zn2+ inter-diffusion with cation of AgInS2. Photo-luminescent (PL) wavelength range of the obtained core-shell structured AgInS2/ZnS extended from 703 nm to 524 nm with high PL quantum yield (QY) and stability. The champion device based on the optimized AgInS2/ZnS QDs exhibits warm white light (correlated color temperature = 3652 K) characteristics with high color rendering index (CRI Ra) of 92.85 while maintaining excellent color stability under different driving currents. These properties are far superior to those of WLEDs with YAG phosphor.

Self‐reduction triggered color tuning of Eu3+‐doped aluminosilicate glass for solid‐state white illumination

AbstractRare earth‐doped transparent glass, boasting high transmittance and excellent luminescent properties, holds great potential in the field of all‐inorganic solid‐state white illumination. Currently reported single‐structure solid‐state white lighting usually has the problems of low color rendering index (CRI) and high correlated color temperature (CCT) due to the lacking of red light emission. In this work, a novel single‐structure MgO–Al2O3–SiO2–Eu2O3 (MAS: Eu) glass with color tuning was prepared by the simple glass melting process. Interestingly, the prepared Eu3+‐doped aluminosilicate glass possessed a unique capability to achieve color emission under different excitation wavelengths. The reason for this was attributed to the good self‐reduction capability of the MAS glass, which effectively reduced Eu3+ to Eu2+ under an air atmosphere. Meanwhile, only by regulating the Eu3+ doping concentration, the MAS glass also achieved a tunable emission from blue to white to red light under 380 nm excitation. The acquisition of white light was realized through the multispectral emission of blue–green light emitted by Eu2+ and orange–red light emitted by Eu3+. Remarkably, the single‐structure MAS glass doped with 8 wt.% Eu3+ successfully achieved high‐quality white light and high thermal stability, exhibiting a high CRI of 86, a low CCT of 2761 K, good chromaticity parameters of (0.407 and 0.3192), and the emission intensity at 423 K remains above 86.35% that of room temperature. Meanwhile, the doped Eu3+ exceeded 12 wt.%, without any observable concentration quenching. Moreover, the MAS: Eu glass showed a high transmittance of 90 and a moderate thermal conductivity of 1.45 W/mK (epoxy resin ∼0.17 W/mK). These results would dramatically inspire the development of high‐quality solid‐state white lighting applications.

Perception of commercial advertising by generations Y and Z

Generations Y and Z make up a significant share of consumers, so businesses need to adapt their advertising strategies and communication methods to the characteristics of each generation. The purpose of the paper is to investigate the differences in the perception of commercial advertising by generations Y and Z. The methodological basis of the study is marketing theory and the theory of generations. Comparison of means tests, linear regression, and Lasso regression were used as research methods. The data set of the study is represented by data from a survey of 308 respondents conducted in February 2023 and designed us ing the semantic differential method. Our findings show statistically significant differences in the perception by generations Y and Z of the colour temperature of a commercial, the dynamism and volume of the music, and friendliness of the actors. Among the factors affecting the probability of purchase by both generations are the need for product, colour temperature, and high-quality commercial editing, while generation Z is influenced by the semantic component and friendliness of the actors, and generation Y – by the emotional component. Generation Y consumers are more prone to impulse buying behaviour. The factors influencing the likelihood to purchase are ranked in descending order of importance: for generation Z, these are the need for product, inter est in the plot of the commercial, attractiveness of the actors, and exclusivity of the offer; for generation Y, these are the need for product, inspiration after watching, depth of meaning of the advertisement, and exclusivity of the offer. The results of the study may be useful to representatives of the marketing and advertising industry.

Tunable green-blue luminescence of Dy2O3 doped borosilicate glasses for optoelectronic devices

The optical-structural correlated properties of the 40B2O3−40SiO2−10V2O5−(10−x)Fe2O3−xDy2O3 system, where 2, 4, and 6 mol%, were studied. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) confirmed the glassy and amorphous nature of the samples. Adding Dy2O3 promoted the formation of bridging oxygens (upto 4 mol%) by converting BO3 into BO4 units, however, above 4 mol% Dy2O3 act as a modifier. The optical band gap increased from 3.70 to 4.01 eV, while the refractive index decreased from 2.23 to 2.16. The CIE coordinates indicated that the emission spectra fall within the green-blue region. The as-prepared sample exhibited the highest correlated colour temperature value above 5000 K, suggesting its suitability for cool light-emitting diodes sensitive to human vision. These glasses have potential applications in light-emitting diodes and optoelectronic devices.

Warm for fun, cool for work: the effect of color temperature on users’ attitudes and behaviors toward hedonic vs. utilitarian mobile apps

PurposeIn the competitive app store environment, understanding how various app store elements influence user preferences is crucial. While prior research has primarily focused on textual and numeric elements of app stores, the role of visual elements remains underexplored. This study addresses this gap by investigating how color temperature (warm vs. cool) in app screenshots can influence users’ intentions to download hedonic vs. utilitarian mobile apps.Design/methodology/approachMultiple online experiments were conducted, including two main experiments (N = 192) and two supplementary experiments (N = 157). The experiments manipulated the color temperature of screenshots for hedonic (e.g. gaming) and utilitarian (e.g. banking) apps and measured participants’ perceptions of color appropriateness, attitudinal responses, and download intentions.FindingsWarm colors were perceived as more appropriate for hedonic apps, while cool colors were perceived as more suitable for utilitarian apps. The congruence between color temperature and app value orientation significantly influenced users’ ad attitudes and app download intentions. Specifically, hedonic apps in warm colors and utilitarian apps in cool colors received more favorable responses, with perceived color appropriateness mediating this effect.Originality/valueThis research enhances the understanding of the impact of color on app users’ perceptions and behaviors and also offers valuable insights for app developers and marketers on effectively using color as a visual marketing tool in app store environments.

White Light Generation and Stability Analysis of High-Power Blue LDs with Remote YAG Phosphors

This paper presents a comprehensive analysis of white light generation and the associated aging dynamics using high-power blue laser diodes (LDs) combined with transmissive single crystal remote YAG phosphors. By systematically varying input currents (ranging from 0.6 A to 3 A) and phosphor thicknesses (250 μm and 500 μm), this study elucidates the optical and electrical characteristics of LD-phosphor systems under diverse operating conditions. The results highlight the system’s potential for stable and efficient white light generation, making it suitable for high-power lighting applications. Experimental setups included both single LDs and a 4 × 2 LD array. For the single LD, a peak optical output of 4.16 W was achieved at 3 A, corresponding to an initial luminous flux of approximately 700 Lm and a correlated color temperature (CCT) of 4653 K, with minimal color temperature shift observed during a 60 min aging process. The 4 × 2 LD array demonstrated consistent white light output across varying phosphor thicknesses, with maximum luminous fluxes of 1857 Lm at 1.4 A and 2622 Lm at 1.6 A for phosphor thicknesses of 250 μm and 500 μm, respectively. Importantly, the phosphor exhibited excellent thermal stability throughout the aging process, with the CCT maintained within a range of 4600 K to 5500 K. These findings underscore the reliability and applicability of LD-based white light systems in demanding high-power lighting environments, offering a promising alternative to conventional light sources for automotive, industrial, and specialized lighting applications.

Lead‐free Halide Perovskites With ≈100% PLQY and Dual‐Color Emission for White Light‐Emitting Diodes

AbstractLead‐free halide perovskites (LHP) have attracted extensive attention in the field of next‐generation solid‐state lighting. However, single perovskite phosphor with tunable white‐light emission and ultra‐high photoluminescence quantum yield (PLQY) are rare. Here, the tunable dual‐color emission LHP phosphor is developed with a near‐unity PLQY of 99.5%. The LHP phosphor comprises Cs2NaInCl6: Sb3+/Bi3+ and Cs2InCl5·H2O: Sb3+/Bi3+ crystals, with the transition between these two perovskite structures being adjustable by the concentration of Na+. The addition of NaCl inhibits the hydrolysis of the [Sb(H2O)Cl5]2− octahedron, resulting in 3D connected [SbCl6]3− octahedron with less Jahn‐Teller distortion, and the PLQY of LHP is greater than 90%. Finally, the white‐light diode device is fabricated by assembling the LHP with a ultraviolet light‐emitting diode chip and the white light‐emitting diode device achieved Commission Internationale de l'Eclairage color coordinates of (0.34, 0.33), correlated color temperature of 4936 K, and a high color rendering index of 92.9. The LHP perovskite exhibited multimodal luminescence when excited by 365, 335, and 310 nm UV light, showing the multi‐mode anti‐counterfeiting capabilities of the LHP crystals.

Performance of Triple-Cation Perovskite Solar Cells under Different Indoor Operating Conditions.

We systematically analyze triple-cation perovskite solar cells for indoor applications. A large number of devices with different bandgaps from 1.6 to 1.77 eV were fabricated, and their performance under 1-sun AM1.5 and indoor white light emitting diode (LED) light was compared. We find that the trends agree well with the detailed balance limit; however, the devices near the optimal bandgap (1.77 eV) perform worse due to the lower perovskite quality. Instead, we achieve the highest power conversion efficiency (PCE) of 34.0% under 870 lx with 1.67 eV and Al2O3 passivation. The perovskite with a bandgap of 1.71 eV is not far behind, with a high VOC of 1.02 V. Measurements under different white LED color temperatures confirm that the highest PCE is achieved under the warmest colors. All measurements were carried out in a dedicated indoor setup that ensures the diffuse light typical of indoor environments and allows both short- and long-term measurements. In the best case, we observe no degradation during the 33-day test under simulated office conditions with regular switching on and off of the light and a T80 of 30 days under continuous illumination. The results were obtained from multiple batches, which corroborates our findings and gives them statistical relevance.

On-Off Switching of Singlet Self-Trapped Exciton Emission Endows Antimony-Doped Indium Halides with Excitation-Wavelength-Dependent Luminescence.

Excitation-wavelength-dependent (Ex-De) emitters are a fascinating category of luminescent materials whose emission properties vary with the wavelength of the light used for excitation. Antimony (Sb3+)-doped indium (In)-based metal halides are efficient light emitters; however, the peak fluorescence emission of most Sb3+-activated In-halide remains independent of the excitation wavelength. Here, the study introduces a new Sb3+-doped In-halide cluster, (BDPA)2InCl5:Sb (BDPA+ = C15H18N+, benzyldimethylphenylammonium), which demonstrates efficient Ex-De emission originating from the on-off switchable fluorescence behavior of singlet self-trapped exciton (STE) in 5-coordinate Sb3+ dopant. Interestingly, when excited within the range of 240-370nm, photoluminescence (PL) spectra of (BDPA)2InCl5:Sb show both singlet and triplet STE emission. However, under excitation wavelengths of 370 to 420nm, the singlet STE emission is absent, resulting in a noticeable correlated color temperature change from 1700 to 3800 K. The study provides a new approach to designing color-tunable Sb3+-based luminophores, and also presents a novel application scenario for the widely recognized Sb3+ doping strategy.

Optimizing light environments in aquatics center to enhance the performance of Olympic champions and other elite swimmers: An experimental study

Several major international sports events in the next five years require new sports venues, with lighting environments being a crucial factor. Typically, the lighting systems in sports venues are primarily for illumination. However, since light has been indicated to affect human psychology and physiology, we investigated whether the light environments in sports buildings impact athletic performance. Additionally, swimming is the indoor sport with the most gold medals in the Olympics. Therefore, we conducted a within-subject, randomized crossover study in an aquatics center with fourteen elite swimmers, including the Olympic champions and Asian champions (6 female and 8 male; 19.3 ± 3.4 years of age). During the experiment, the elite swimmers were exposed to either a common correlated color temperature (CCT) light environment (controlled condition: 5780 K) or an experimental light environment (8512 K) in the aquatics center, with both having the same illuminance (1020 lx). The neurobehavioral and swimming test results showed that the Olympic champions and other elite swimmers had significantly faster responses, fewer lapses, greater arousal, less visual fatigue, quicker reactions at start, and higher swimming speeds in the experimental condition compared to the controlled condition (p < 0.05). Our findings suggest that the light environment in the aquatics center affects swimmers' non-visual performance and enhancing the CCT of the light environment could improve swimmers' performance. We propose the concepts of Sports Lighting Beyond Illumination and Sports Human-Centric Lighting to enhance athletes’ health and performance, and to improve the sports environment for a better experience for all participants.

Thermal reflectance of fabric in color temperature spectral domain

PurposeThis study aims to explore the thermal reflectance of fabrics under sunlight or other thermal radiation sources at various color temperatures.Design/methodology/approachThis study analyzed the spectral distribution of sunlight at different solar altitude angles as well as the spectral distribution characteristics of other light and thermal radiation sources, pointing out that their color temperatures can be used to identify their spectral distribution domains. Reflectance, transmittance, absorptance and color temperature domain reflectance of 35 different fibers and color fabrics were tested in a wide spectral range. The different behavior of these optical parameters in the segmented spectrum is discussed. The temperature rise tests demonstrate that the reflectance corresponding to the color temperature of the radiation sources is highly correlated with the temperature rise results.FindingsThe reflectance in the color temperature domain shows a strong correlation with the radiation source at same color temperature. The correlation coefficients for the 6,000 K xenon lamp test are −0.96 and −0.90 in two groups, and for the 3,200 K tungsten iodine lamp test are −0.87 and −0.90 as well.Originality/valueThe concept of fabric thermal reflectance in the color temperature domain was first introduced to match different thermal radiation sources. Validation of temperature rise is conducted through a self-constructed tester with unidirectional adiabatic heating. This new discovery could serve as a basis for developing functional fabric or clothing, such as sun-proof clothing, fire protection clothing, etc.

Evaluation of Luminescent and Thermal Properties of Dy³⁺ Doped Tungstate Phosphors for Optoelectronic and Thermometry Applications

Novel Ca2MgWO6: xDy3+ (x = 1, 2, 3, 4, and 6 mol%) phosphors were synthesized via solid-state reaction method. The phosphor structure remained unchanged upon doping with Dy3+ ions. Phosphors were optical optimizated using 4F9/2 → 6H13/2 transition, and 3 mol% of Dy3+ was found to be optimal concentration. We investigated optical quenching mechanisms including energy transfer, cross-relaxation, charge compensation, and multipole-multipole interactions. Colorimetric analyses assessed colour coordinates, purity, and correlated colour temperature (CCT). The optimized phosphor showed a direct band gap of 3.68 eV, a refractive index of 2.24, and covalent bonding between Dy3+ and the host. It exhibited exceptional thermal stability with only 0.31 wt% loss up to 440°C. Temperature-dependent emission spectra indicated high optical quenching temperature (498.82 K) and activation energy (0.21 eV). A multi-transition ratiometric approach confirmed suitability for non-contact thermometry and LED applications.

Calcium vacancy enhanced self-reduction of Ce4+ for single-phase full-spectrum lighting and information encryption

Due to the wide and adjustable emission range, Ce3+ is an indispensable luminous center for full spectrum lighting. However, it needs to be sintered at high temperature in a reducing atmosphere, resulting in difficulty to coexisting with other multivalent activated ions (such as Eu3+, Tm3+), which greatly hinders the formation of full spectrum. In this study, a calcium vacancy enhanced self-reduction of Ce4+ is realized in CaNaSb2O6F (CNSOF) host under air atmosphere sintering, through which Ce3+, Tm3+ and Eu3+ coexisting in a single-phase full spectrum phosphor was prepared. Notably, the artificial introduction of a calcium vacancy was designed to verify this self-reduction mechanism. Moreover, the energy transfer kinetics among Tm3+, Ce3+ and Eu3+ were explored. Finally, combined with a 340 nm UV chip, a full spectrum phosphor-converted light-emitting diode (pc-LED) was fabricated, showing a broad emission range from 400 to 750 nm, Commission Internationale de I’Eclairage (CIE) of (0.3485, 0.3673), Ra of 92 and correlated color temperature (CCT) of 4933 K. Utilizing the variation in emission colors of this phosphor under different UV wavelengths, a dual encryption method combining point character code and fluorescent encryption technique is proposed. This work provides an effective path for Ce4+ self-reduction to apply in full spectrum pc-LED and information encryption.

Violet Light Excitable BaLiZn3(PO4)3: Eu3+ Orange-red-emitting Phosphor towards White LED Application

White light-emitting diode (WLED) has been widely used as solid-state lighting in recent years, with the advantages of energy saving, high luminous efficiency, and safety. Red phosphors are crucial to the color rendering index of WLED, and Eu3+-activated red phosphors can significantly improve the chromaticity performance of WLED. In this work, a series of new orange-red emitting BaLiZn3(PO4)3: Eu3+ phosphors were synthesized through high-temperature solid-state reaction method. The phase composition, crystal structure, morphology and photoluminescence properties of BaLiZn3(PO4)3: Eu3+ samples were investigated. The phosphors can be effectively excited by the violet light at 394 nm and emit orange-red lights corresponding to the electric dipole transition (5D0→7F1) at 594 nm. The optimal doping concentration of Eu3+ ions was about 5 mol%. The concentration quenching was caused by the electric dipole-dipole interaction between Eu3+ ions. Temperature-dependent PL spectra indicate that BaLiZn3(PO4)3: Eu3+ has excellent emission and color stability at high temperatures. The color coordinates were calculated and fall in the orange-red luminescent area. The color purity is about 98.3%, and the correlated color temperature is 1710K. These results indicate that the new orange-red phosphor BaLiZn3(PO4)3: Eu3+ has potential application prospects in WLED.

A well-performed green-emitting Lu1.5Ca1.5Al3.5Si1.5O12:Ce3+ garnet phosphor for high-quality pc-WLEDs

High-brightness and thermally-stable broadband green-emitting phosphors are highly demanded for the fabrication of high-quality phosphor-converted white light-emitting diodes (pc-WLEDs) with high color rendering index (CRI) and low correlated color temperature (CCT). Herein, we report on the synthesis, luminescent properties, thermal stability and application of a novel highly efficient green-emitting Lu1.5Ca1.5Al3.5Si1.5O12:Ce3+ garnet-type phosphor for blue-chip-pumped high-CRI pc-WLEDs. A series of Lu1.5Ca1.5Al3.5Si1.5O12:Ce3+ green phosphors doped with various Ce3+ concentrations (0.5-4 mol%) have been prepared by a conventional high-temperature solid-state reaction approach. Impressively, the composition-optimized Lu1.5Ca1.5Al3.5Si1.5O12:2%Ce3+ sample exhibits a broad excitation band in the 400-500 nm spectral range with an excitation peak around 451 nm, and it gives rise to a bright broad green emission band in the 470-700 nm wavelength region (emission peak: 533 nm; bandwidth: 108 nm) with CIE color coordinates of (0.3361, 0.5640). Notably, high luminescence efficiency is obtained for Lu1.5Ca1.5Al3.5Si1.5O12:2%Ce3+ phosphor (internal quantum efficiency: 92.2%; external quantum efficiency: 50.7%). Moreover, it is also found that Lu1.5Ca1.5Al3.5Si1.5O12:2%Ce3+ shows excellent resistance to thermal quenching, while its emission intensity at 423 K remains 76% of the initial value at room temperature. Amazingly, the color stability of Lu1.5Ca1.5Al3.5Si1.5O12:2%Ce3+ is also outstanding, and only a very small chromaticity shift (3.99 × 10−3) is observed at 423 K. A high-performance pc-WLED device has been fabricated by using a 450 nm blue-emitting LED chip and as-prepared Lu1.5Ca1.5Al3.5Si1.5O12:2%Ce3+ green phosphor as well as commercial CaAlSiN3:Eu2+ red phosphor. Such device produces a bright warm-white emission under 280 mA driving current, demonstrating super CIE chromaticity coordinates (0.3870, 0.3818), high CRI of 93.8, low CCT of 3865 K, and high luminous efficacy (51.86 lmW-1).

Enhanced luminescence of CaO:Eu2+ red phosphor in glass for high-power warm LED

Highly emissive and stable red phosphors are vital for the warm Light Emitting Diode (LED). Herein, blue-light-excited CaO:Eu2+ red phosphors were prepared using the carbonation method, coupled with the double crucible carbon reduction technology. The addition of GeO2 and SnO2 significantly enhanced the photoluminescence (PL) intensity and quantum efficiency. Furthermore, a phosphor-in-glass (PiG) made from an improved luminescent CaO:Eu2+ was developed and utilized for LED applications. Such PiG samples considerably improved the stability of CaO:Eu2+ phosphors. The excellent stability, high color rendering index (Ra) value of 87.7 and low correlated color temperature (CCT) of 4469 K confirmed the resulting CaO:Eu2+-based PiG as a promising material for white light-emitting diodes (WLEDs).