International Commission On Illumination Research Articles

Effect of a novel low-concentration hydrogen peroxide bleaching gel containing nano-sized sodium trimetaphosphate and fluoride

ObjectivesTo evaluate in vitro the effects of nano-sized sodium trimetaphosphate (TMPnano) and sodium fluoride (F) added to a 17.5 % hydrogen peroxide (H2O2) bleaching gel on the color change, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion. Materials and MethodsBovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 17.5 % H2O2 (17.5 % HP); 17.5 % H2O2 + 0.1 % F (HP/F); 17.5 % H2O2 + 1 % TMPnano (HP/TMPnano); 17.5 % H2O2 + 0.1 % F + 1 % TMPnano (HP/F/TMPnano) and 35 % H2O2 (35 % HP). The gels were applied for 40 min on three sessions, each session spaced 7 days apart. The total color change (ΔE*ab) according to the Commission Internationale de l'Eclairage (CIE) L*a*b* color change measured by CIEDE2000 (ΔE00), whitening index (ΔWID), surface hardness (SH), surface roughness (Ra), cross-sectional hardness (ΔKHN), and transamelodentinal diffusion were assessed. Enamel surfaces were examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDS) analysis. The data were analyzed using ANOVA, followed by the Student-Newman-Keuls test (p < 0.05). ResultsΔE*ab, ΔE00, and ΔWID values were comparable among the gels that produced a bleaching effect post-treatment (p < 0.001). The HP/F/TMPnano group exhibited lower mineral loss (SH and ΔKHN), Ra, and H2O2 diffusion compared to the 17.5 % HP and 35 % HP groups, which had the highest values (p < 0.001). SEM/EDS analysis revealed surface changes in all bleached groups, though these changes were less pronounced with F/TMPnano. ConclusionsThe 17.5 % HP gel containing F/TMPnano maintains the bleaching effect while reducing enamel demineralization, roughness, H2O2 diffusion, and enamel morphological changes. Clinical RelevanceLow-Concentration H2O2 bleaching gel containing F/TMPnano can be used as a novel approach to enhance safety and maintain the performance of aesthetic effects.

An efficient and generalisable approach for mapping paddy rice fields based on their unique spectra during the transplanting period leveraging the CIE colour space

As one of the most important staple foods globally, rice sustains nearly half of the world's population. Accurate and timely paddy rice mapping is, thus, essential for rice-related policy-making to ensure food security in the context of anthropogenic, environmental and climate changes. However, paddy rice mapping remains a challenging task since it usually has similar spectral characteristics to other land covers. In this research, for the first time, an entirely new approach, called RiceTColour, was proposed for mapping rice fields within the Commission Internationale de l'Eclairage (CIE) colour space based on their unique spectra during the rice transplanting period as observed in remotely sensed imagery. We demonstrate that transplanted rice fields, representing a mixture of soil, water and rice seedlings, consistently exhibit relatively low spectral values in both SWIR and NIR bands across various geographical locations, leading to their unique dark green colours in the false-colour image composed of SWIR, NIR and Red bands. Based upon this, we transformed these three spectral bands into the CIE colour space where paddy rice was found to be readily and completely separated from the other land covers. Straightforward, but specific classification criteria were established within the CIE colour space to differentiate paddy rice from the other land covers. The proposed RiceTColour, thus, represents a new approach for paddy rice identification, that is mapping paddy rice using the CIE colour space based upon the previous underexplored remotely sensed spectra of paddy fields during the transplanting season. The effectiveness of the proposed method was investigated over five rice-planting regions distributed across different geographical regions, characterised by different climates, rice cropping intensities, irrigation schemes and cultural practices. Specifically, the mapping criteria established in a training site (S1) were directly generalised to the other four sites (S2 to S5) for paddy rice mapping. Experimental results demonstrated that the RiceTColour method consistently achieved the most accurate and balanced classifications across all five sites compared with four benchmark comparators: a SAR-based method, an index-based method and two supervised classifier-based methods. In particular, the RiceTColour method performed relatively stable, producing an overall accuracy exceeding 95% in the training site (S1) as well as the four generalised sites (S2 to S5), which is an encouraging result. Such efficient yet stable rice mapping results across various rice-planting regions suggest a very strong generalisation capability of the proposed RiceTColour method. In consideration of the relatively large planting area of paddy rice fields globally, the proposed parameter-free, efficient, and generalisable RiceTColour method, thus, holds great potential for widespread application in various rice-planting areas worldwide.

Full-color biomass carbon dots for high-level information encryption and multi-color light emitting diode applications.

Six biomass carbon dots (BCDs) with adjustable emission from 450 to 680nm under a single wavelength excitation were successfully synthesized from spinach via solvent control strategy. The obtained BCDs show blue, green, yellow, violet, pink, and red emission with high photoluminescence quantum yield (PLQY = 12.68 ~ 30.77%). Detailed characterizations disclose that the tunable-emission mechanism is caused by the synergistic effect of carbon conjugate and surface oxidation degree. Meanwhile, full-color photoluminescence BCDs/PVP powder and BCDs/PVP/PVA films were fabricated by utilizing the prepared BCDs combined with polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA), respectively, which presented excellent high-level information encryption application. Importantly, multi-color and white light-emitting diode (LED) with Commission Internationale de L' Eclairage (CIE) of blue (0.25, 0.29); green (0.25, 0.31); yellow (0.42, 0.45); red (0.52, 0.31); and white (0.32, 0.31) were achieved by only using our prepared BCDs. This work provides a valuable strategy of preparing multi-color BCDs using readily available biomass materials and paves a way for high-level information encryption and LED applications.

Microwave synthesis of composite of AgInS2 quantum dots and zeolitic imidazolate framework-8 for application in white light emitting diodes

Preparation of AgInS2 quantum dots (AIS QDs) with high photoluminescence quantum yield (PLQY) and thermal stability remains an important challenge. In this paper, AIS QDs were successfully introduced into zeolitic imidazolate framework-8 (ZIF-8) by microwave-assisted hydrothermal method. Due to the effective isolation of the ZIF-8, the AIS QDs avoid the concentration quenching when they were assembled into white light emitting diodes (WLEDs) devices as color conversion materials. More importantly, the generation of ZnS layer between the interfaces of AIS QDs and ZIF-8 can efficiently improve the optical performance of AIS QDs, resulting in the fluorescence lifetime extended to 470.05 ns. Meanwhile, the PLQY of AIS/ZIF-8 composite reached up 34.30 % when microwave hydrothermal heating at 120 °C for 60 min with AgIn/Zn=1/3, which was higher than that of the pristine AIS QDs as 25.30 %. Finally, the WLED devices were fabricated by combining AIS/ZIF-8 composite fluorescent powder with (Ba, Sr)Si2O2N2:Eu2+ phosphors and blue LED. At 20 mA, the AIS/ZIF-8 based WLED shows the luminous efficiency (LE) of 44.54 lm/W, correlated color temperature (CCT) of 4242 K and color rendering index (CRI) of 89.1. Moreover, the Commission International de L'Eclairage (CIE) was (0.36, 0.35), indicating the WLED emited warm white light. The present strategy aims at enhancing the optical performance of AIS QDs, which also may trigger the development of QDs-based WLED.

Design, synthesis, and characterization of intrinsic black polyimide with complete absorption of visible light and low coefficient of thermal expansion

Black polyimides (BPIs) show increasing demand in the microelectronics and optoelectronics fields. However, the existing BPIs have drawbacks of poor masking ability, dimensional stability, thermal and electrical properties. 3,6-Bis(thiophen-2-yl)diketopyrrolopyrroles (TDPP) is a typical dye that possesses a high molar extinction coefficient. In the work, a new diamine (DPPTOMePDA) bearing TDPP connected with methoxyl-substituted benzene rings was synthesized. Based on such diamine and pyromellitic dianhydride (PMDA), a high-performance intrinsic BPI (DPPTOMePPI) was obtained. The resulting DPPTOMePPI exhibited a red-shifted and broadened absorption spectrum, thus achieving complete absorption of visible light and highly black color. Its cut-off wavelength (λcut) was up to 734 nm, and the Commission International de l’Eclairage (CIE)-Lab coordinate L* decreased to 0.53. Furthermore, DPPTOMePPI exhibited excellent thermal and electrical performances with a low coefficient of thermal expansion (CTE). Density functional theory calculation was executed to analyze the underlying electron transitions of DPPTOMePPI. The results showed that the strong light absorption of DPPTOMePPI was primarily ascribed to the electronic transition of HOMO to LUMO+1 that occurred in the chromophores units. The flexible copper clad laminates (FCCLs) derived from DPPTOMePPI film showed high peel strength and resistance to solder heat. The work offers a theoretical guide for the construction of intrinsic black PI possessing complete visible absorption and low CTE.

Fluorescent Aromatic Polyether Sulfones: Processable, Scalable, Efficient, and Stable Polymer Emitters and Their Single-Layer Polymer Light-Emitting Diodes.

In this study, fully aromatic polyether sulfones were developed, bearing blue, yellow, and orange-red π-conjugated semiconducting units. Carbazole-, anthracene-, and benzothiadiazole-based fluorophores are copolymerized with a diphenylsulfone moiety. A diphenylpyridine comonomer was additionally utilized, acting as both a solubilizing unit and a weak blue fluorescent group. Using this rationale, fluorescent polyarylethers with high molecular weights, up to 70 kDa, were developed, showing film formation ability and high thermal stability, while preserving excellent solubility in common organic, nonvolatile, and nonchlorinated solvents. Fine-tuning of the emission color was achieved through subtle changes of the comonomers' type and ratio. Single-chromophore-bearing copolymers emitted in the blue or the yellow region of the visible spectrum, while the dual-chromophore-bearing terpolymers emitted throughout the visible spectrum, resulting in white light emission. Solutions of 20 wt% in polar aprotic solvents at ambient conditions allowed the deposition of fluorescent copolyethers and printing from non-chlorinated solvents. All polyethers were evaluated for their structural and optoelectronic properties, and selected copolymers were successfully used in the emitting layer (EML) of organic light-emitting diode (OLED) devices, using either rigid or flexible substrates. Remarkable color stability was displayed in all cases for up to 15 V of bias voltage. The Commission Internationale de L'Eclairage (CIE) of the fabricated devices is located in the blue (0.16, 0.16), yellow (0.44, 0.50), or white region of the visible spectrum (0.33, 0.38) with minimal changes according to the ratio of the comonomers. The versatile methodology toward semiconducting polyethersulfones for polymer light-emitting diodes (PLEDs) developed herein led to the scaled-up production of luminescent polymers of up to 25 g of high-molecular-weight single batches, demonstrating the effectiveness of this approach as a straightforward tool to facilitate the synthesis of flexible and printable EMLs for large-area PLED coverage.

A highly thermal-stable orange red emitting La(OH)₃:Sm³⁺ phosphor for w-LED and thermal sensor dual-applications

The orange-red emitting La(OH)₃:Sm³⁺ (1–5 mol.%) phosphors are synthesized using urea-assisted solution combustion synthesis (SCS). The synthesized La(OH)₃:Sm³⁺ phosphors were validated by Rietveld refinement and X-ray diffraction (XRD) patterns and exhibit a single-phase structure, characterized by a hexagonal system with space group P63/m. At 250 nm, the phosphors display a charge transfer band (CTB) involving O2− and Sm3+, indicating intense excitation. La(OH)₃:Sm³⁺ phosphor exhibits distinctive peaks at 565, 604, 651, and 708 nm under 250 nm excitation, which correspond to the 5G₅/₂ → 6HJ (J = 5, 7, 9, 11) transitions. Among these, 604 nm exhibits the most intense emission. The optimal doping concentration of La(OH)₃:Sm³⁺ is x = 2 mol.%. Importantly, even as the temperature increases to 420 K, La(OH)₃:Sm³⁺ demonstrates exceptional thermal stability, retaining 86.38 % of its initial luminescence intensity. The La(OH)₃:2Sm³⁺ phosphor exhibits an activation energy (Ea) of 0.328 eV. The internal quantum efficiency (IQE) measures 50.09 %. The colour purity (CP) for each phosphor is calculated to be 96.50 %. Additionally, 405 nm chips are effectively used for fabricating single-coloured and white light-emitting diodes (w-LEDs). The Commission Internationale de l'Eclairage (CIE) coordinates of the packaged w-LED are (0.325, 0.350), with a high colour rendering index (CRI) of 90. These results from investigations show that orange-red emitting La(OH)₃:Sm³⁺ phosphors have potential for development lighting device materials.

Delignification of wood toward photoluminescent smart window infiltrated with glass nanofibers-reinforced polystyrene for multifunctional applications

Multifunctional photochromic and fluorescent woods that can change their color in the presence of ultraviolet light were developed. A formulation of electrospun glass nanofibers-reinforced styrene as a hosting agent and rare-earth strontium aluminate (RSA) as a photoluminescent was infiltrated into a lignin-modified wooden substrate, resulting in translucent wood with fluorescence and photochromic properties. The RSA pigment is known for its good photostability and thermal stability. An ideal method for producing transparent photoluminescent wood involves dispersing the RSA phosphor in pre-polymerized glass nanofibers-reinforced styrene without aggregation. According to the colorimetric data from the CIE (Commission Internationale de l´Eclairage) Lab color space coordinates, this photoluminescent wood substrate became green when exposed to ultraviolet light, but remained colorless when exposed to visible light. Electron microscopic images were used to investigate the morphologies of the synthesized pigment nanoparticles (NPs) and electrospun glass nanofibers, displaying diameters of 5–15 nm and 50–100 nm, respectively. The photoluminescent woods were inspected with different microscopic and spectroscopic techniques, including energy-dispersive X-ray spectroscopy (EDX), X-ray fluorescent spectroscopy (XRF), and scanning electron microscopy (SEM). Upon excitation at 365 nm, the photoluminescence transparent timbers demonstrated an emission intensity at 519 nm. When increase the phosphor content, the produced luminous wood was monitored to be more water-resistant and had better protection from ultraviolet rays. The reaction of the transparent luminous wood to ultraviolet light was rapid and reversible without fatigue.

Pedogenic variables with color indices of rubified Alfisols in the Kakalachinte microwatershed, Karnataka, South India

Soil properties and processes can often be estimated by soil color, which provides valuable information about composition and other properties. We focused on the morphology, particle size distribution, and chemical properties of Alfisols in Kakalachinte microwatershed, Karnataka, India. Soil redness indices were calculated: Buntley's and Westin's rate (BWR), Hurst's rate (HR); Torrent’ rates (TR1 and TR2); Barrón's and Torrent's rates (BTR1 and BTR2), and Viscarra's rate (VR). The Munsell notation was converted to the CIE (Commission Internationale del'Eclairage, CIE) Lab system, Lab model: L*, luminance, a*, redness, and b*, yellowness of moist soil samples. Forty-five soil samples were characterized for texture, soil reaction (pH), electrical conductivity, calcium carbonate content, organic carbon (OC) content, exchangeable cations (sodium, Na; potassium, K; magnesium, Mg; and calcium, Ca), base saturation (BS), and cation exchange capacity (CEC). The pH of the soils ranged from strongly acid (pH of 5.25) to strongly alkaline (pH of 8.73). These soils exhibited low CEC, with a mean of 8.36 cmol(+)/kg and a coefficient of variation of >35%. The BS was found to be >70%, with a dominance of exchangeable Ca (6.93 ± 1.08 cmol(+)/kg). Correlation analysis revealed strong positive relationships between OC and the L* value (r = 0.6**). The correlation results revealed a strong positive correlation of a* value with TR1 (r = 0.54**), significant negative relationship between L* and BTR1 (r = −0.54*), BTR2 (r = −0.525*), and VR (r = −0.53*). Regression between soil OC and the L* value showed R2 of 0.40 and RMSE of 0.01; soil exchangeable K and Mg with the R2 = 0.74; RMSE = 0.12 and the R2 = 0.42; RMSE = 0.11 at p < 0.001. The study highlights the importance of converting Munsell color notation to the CIELab system for understanding the rubification process in relation to soil properties in Alfisols at the microwatershed level.

Nitrogen-Embedding Strategy for Short-Range Charge Transfer Excited States and Efficient Narrowband Deep-Blue Organic Light Emitting Diodes.

The development of deep-blue organic light-emitting diodes (OLEDs) featuring high efficiency and narrowband emission is of great importance for ultrahigh-definition displays with wide color gamut. Herein, based on the nitrogen-embedding strategy for modifying the short range charge transfer excited state energies of multi-resonance (MR) thermally activated delayed fluorescence (TADF) emitters, we introduce one or two nitrogen atoms into the central benzene ring of a versatile boron-embedded 1,3-bis(carbazol-9-yl)benzene skeleton. This approach resulted in the stabilization of the highest occupied molecular orbital energy levels and the formation of intramolecular hydrogen bonds, and thus systematic hypsochromic shifts and narrowing spectra. In toluene solution, two heterocyclic-based MR-TADF molecules, Py-BN and Pm-BN, exhibit deep-blue emissions with high photoluminescence quantum yields of 93 % and 94 %, and narrow full width at half maximum of 14 and 13 nm, respectively. A deep-blue hyperfluorescent OLED based on Py-BN exhibited a maximum external quantum efficiency of 27.7 % and desired color purity with Commission Internationale de L'Eclairage (CIE) coordinates of (0.150, 0.052). These results demonstrate the significant potential for the development of deep blue narrowband MR-TADF emitters.

Preparation of lanthanide aluminate‐encapsulated silica nanoparticles toward long‐persistent photoluminescent polymer paint with superhydrophobic and anticorrosion properties

AbstractSmart afterglow paints can function as energy‐saving products that are able to persist lighting in the dark. Additionally, polyurethane paints (PURPs) have shown some limitations, including weak adhesion, poor mechanical performance, poor corrosion, and low water resistance as compared with solvent‐based paints. Herein, nanoparticles of lanthanide aluminate (NLA; 16–24 nm) were mixed with polyurethane and silica to develop novel photoluminescent nanocomposite paints. A precursor of NLA‐encapsulated silica nanoparticles (NLA@Silica; 200–225 nm) can be described as a SiO2‐coated NLA pigment prepared by the heterogeneous precipitation method. Steel was coated with nanocomposite paints made of PURP, silica, and NLA. Using emission spectra and Commission Internationale de l'Eclairage (CIE) Lab coordinates, the coloring and transparency of painted films were investigated. Upon excitation at 365 nm, the UV‐irradiation of transparent painted films showed green emission at 518 nm. The hydrophobic activity and hardness properties were examined. Using electrochemical impedance spectroscopy (EIS), the anticorrosion of coatings applied to mild steel was studied. Improved anticorrosion characteristics were observed due to the fluorescence of NLA@Silica in the applied coatings. The optimal long‐lasting luminous characteristics were observed for nanocomposite films containing 12.5% of NLA@Silica.

Spectrally Stable and Bright Red Perovskite Light-Emitting Diodes.

Mixing iodide and bromide in three-dimensional metal-halide perovskites is a facile strategy for achieving red light-emitting diodes (LEDs). However, these devices often face challenges such as instability in electroluminescence spectra and low brightness due to phase segregation in mixed-halide perovskites. Here, we demonstrate spectrally stable and bright red perovskite LEDs by substituting some of the halide ions with pseudohalogen thiocyanate ions (SCN-). We find that SCN- can occupy halogen vacancies, thereby releasing microstrain and passivating defects in the perovskite crystals. This leads to the suppression of mixed-halide phase segregation under electrical bias. As a result, the red perovskite LEDs exhibit a high brightness of >35 000 cd m-2 with stable Commission Internationale de l'Eclairage (CIE) coordinates of (0.713, 0.282). This brightness surpasses that of the best-performing red perovskite LEDs, showing great promise for advancing perovskite LEDs in display and lighting applications.

Characterization of a thermally stable red-light-emitting phosphor: synthesis, photoluminescence, and thermoluminescence studies of CsCaF3 compound doped with Eu3+ for solid-state lighting applications

In this investigation, we focused on the synthesis and characterization of CsCaF3 compound doped with europium (Eu3+) ions using a solid-state route. To analyze the crystal structure of the synthesized phosphors, X-ray diffraction analysis was employed. Additionally, the doped sample underwent examination of surface morphology and elemental composition through Field Emission Scanning Electron Microscopy and EDAX mapping. The color of the pure and doped CsCaF3 sample was quantified and fitted using Color coordinate graph by the Commission Internationale de l'Eclairage (CIE). The red emission on the doped CsCaF3 compound was detected at 465 nm, which is the transition from 5D0 to 7Fj (j = 0, 1, 2, and 3). The 0.5 mol. % Eu3+ doped CsCaF3 sample was found to have a color purity of 81% and an associated color temperature of 1660 K, indicating its suitability for aesthetic lighting applications. Furthermore, thermoluminescence study, electron paramagnetic resonance (EPR), and effective atomic number (Z eff) calculations were conducted to provide valuable information for potential radiation dosimetry applications.

Exploring the role of neutral ligands in modulating the photoluminescence of samarium complexes with 1,1,1,5,5,5-hexafluoro-2,4-pentanedione.

Four eight-coordinated luminescent samarium complexes of type [Sm(hfpd)3L2] and [Sm(hfpd)3L'] [where hfpd = 1,1,1,5,5,5-Hexafluoro-2,4-pentanedione L = tri-octyl-phosphine oxide (TOPO) and L' = 1,10-phenanthroline (phen), neocuproine (neoc) and bathocuproine (bathoc) were synthesized via a stoichiometrically controlled approach. This allows for precise control over the stoichiometry of the complexes, leading to reproducible properties. This investigation focuses on understanding the impact of secondary ligands on the luminescent properties of these complexes. Infrared (IR) spectra provided information about the molecular structures, whereas 1H and 13C nuclear magnetic resonance (NMR) spectra confirmed these structural details along with the coordination of ligands to trivalent Sm ion. The UV-vis spectra revealed the molar absorption coefficient and absorption bands associated with the hfpd ligand and photoluminescence (PL) spectroscopy demonstrated intense orange-red emission (648 nm relative to 4G5/2 → 6H9/2) from the complexes. The Commission Internationale de l'Éclairage (CIE) triangles indicated that the complexes emitted warm orange red light with color coordinates (x, y) ranging from (0.62, 0.36) to (0.40, 0.27). The investigation of the band gap as well as color parameters confirms the utility of these complexes in displays and LEDs.

Methods for detecting green tide in the Yellow Sea using Google Earth Engine platform

The green tide was a blooming phenomenon consisting of outbreaks and aggregations of marine macroalgae, causing severe damage to the ecosystem of the Yellow Sea in China. Remote sensing technology was considered an effective means of green tide detection. Currently, commonly used low spatial resolution satellites cannot satisfy the green tide detection in the fine-scale range. To better improve the accuracy of green tide identification, based on the Commission Internationale del'éclairage (CIE) system, two new green tide detection algorithms (CIE xy, hue angle α) were established using Sentinel-2 MultiSpectral Instrument (MSI) and Landsat-8 Operational Land Imager (OLI) data on the Google Earth Engine (GEE) platform. These algorithms were validated by introducing the quantitative index Dgw from "Interclass Distance". The CIE xy algorithm and the hue angle α algorithm based on Sentinel-2 MSI exhibited higher Dgw values of 10.29 and 5.87, respectively, surpassing the performance of the two algorithms based on the Landsat-8 OLI in green tide identification (Dgw values of 3.36 and 5.17, respectively). Meanwhile, the proposed algorithms were compared with normalized difference vegetation index (NDVI), difference vegetation index (DVI), ratio vegetation index (RVI), floating algae index (FAI), enhanced vegetation index (EVI), and algal bloom detection index (ABDI) algorithms using Sentinel-2 MSI images. The results showed that the CIE xy algorithm and the NDVI algorithm outperformed the other algorithms. Especially in turbid water, the CIE xy algorithm exhibited significant advantages. However, the hue angle α algorithm still showed some potential in identifying green tide, particularly in the presence of thin cloud interference. These findings can provide effective information support for the monitoring of green tide in the Yellow Sea.

Enhancing Emission and Stability in Na-Doped Cs3Cu2I5 Nanocrystals.

Lead-free Cs3Cu2I5 metal halides have garnered significant attention recently due to their non-toxic properties and deep-blue emission. However, their relatively low photoluminescence quantum efficiency and poor stability have limited their applications. In this work, sodium iodide (NaI) is used to facilitate the synthesis of Cs3Cu2I5 nanocrystals (NCs), demonstrating improved photoluminescence intensity, photoluminescence quantum yield, and stability. Systematic optoelectronic characterizations confirm that Na+ is successfully incorporated into the Cs3Cu2I5 lattice without altering its crystal structure. The improved Photoluminescence Quantum Yield (PLQY) and stability are attributed to the strengthened chemical bonding, which effectively suppresses vacancy defects in the lattice. Additionally, light-emitting diodes (LEDs) based on 10% NaI-doped Cs3Cu2I5 NCs were assembled, emitting vibrant blue light with a maximum radiant intensity of 82 lux and Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.15, 0.1). This work opens new possibilities for commercial lighting display applications.

A diphenylphosphine oxide decorated multi-resonance TADF emitter for narrowband green electroluminescence with an EQE of 32.4.

A new narrowband thermally activated delayed fluorescence emitter, PhCzBN-PO, was developed by incorporating the diphenylphosphine oxide (DPPO) group into a multi-resonance core. The unique properties of DPPO enabled PhCzBN-PO to achieve pure green emission and a nonplanar structure. The resulting electroluminescent devices achieved high external quantum efficiencies up to 32.4% with extremely low efficiency roll-off and pure-green emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.24, 0.67).

Synthesis and luminescence properties of Eu3+-activated Mg3(PO4)2 phosphors and substitution of phosphate with molybdate, tungstate and sulphate

In the present work, trivalent europium (Eu3+) ion activated Mg3(PO4)2 red phosphors have been synthesized through solid-state reaction method. X-ray diffraction (XRD) confirmed the successful formation of Mg3(PO4)2:Eu3+ phosphors with monoclinic phase with space group P21/c (14). The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu3+ activated Mg3(PO4)2 phosphor. Under the excitation of 395 nm, the resultant samples exhibited the characteristic emissions of Eu3+ ions corresponding to the 5D0 → 7FJ transitions. The optimal doping concentration of Eu3+ ions was determined to be 0.5 mol%. The Commission Internationale de l'Eclairage (CIE) coordinates of Eu3+ activated Mg3(PO4)2 phosphor is calculated, which shows strong red emission. In addition, phosphate group replaced with molybdate, tungstate and sulfate group and found enhancement in emission intensity of prepared phosphors. The obtained results demonstrated that the Eu3+-activated Mg3(PO4)2 phosphors are very appropriate red-emitting phosphors for applications in near-ultraviolet-excited white Light emitting diodes (LEDs).

Yellowish light emitting Dy3+ doped single phase – BaNb2O6 phosphors for solid state lighting applications

BaNb2O6:Dy3+ phosphors that emit cool light has been synthesized via traditional solid-state reaction technique. Developed samples show orthorhombic structure with space group C2221 according to X-Ray Diffraction (XRD) and Rietveld structural refinement. Observations made using a scanning electron microscope (SEM) show densely packed particles with irregular shapes in the micrometre range. Optical bandgap was also determined using Diffuse Reflectance Spectroscopy (DRS). When excited at 389 nm, the as-prepared phosphors show blue (481 nm) and yellow (577 nm) emissions, which correspond to the 4F9/2 → 6HJ (J = 15/2, 13/2) transitions of Dy3+ ions. A thorough investigation has been done on the energy transfer process between Dy3+ ions. The optimized phosphor's computed chromaticity coordinates for the Commission Internationale de L'Eclairage (CIE) are x = 0.392 and y = 0.414. The values of CIE chromaticity coordinates and correlated colour temperature (CCT) of 3995 K endorse near cool light emission from the phosphor. Thermal stability and temperature dependent photoluminescence spectroscopy were studied for optimized phosphor which revealed that the phosphor can be a potential material for lighting applications at higher temperature. The study also reveals that BaNb2O6:Dy3+ phosphor could be a promising candidate for near ultra-violet (NUV) excited, yellowish LED applications.

Insights into the preparation and photoluminescence properties of MgTi2O5: Eu3+ red phosphor with high color purity for w-LED applications

As one of the critical components for achieving high-quality white light emitting diodes (w-LEDs) are efficient phosphors, a series of intense red emitting Eu3+doped magnesium dititanate (Mg(1-x)Ti2O5: xEu3+; x = 0, 0.005, 0.008, 0.01, 0.02 and 0.03 mol) phosphors were prepared via solid-state reaction method. The X-ray diffraction (XRD) patterns confirmed the phase purity and orthorhombic structure of the prepared phosphors. The Ti-O functional groups were detected from the Fourier transform infrared (FTIR) spectra and Field emission scanning electron microscopy (FESEM) images revealed agglomerated spherical-like shaped phosphor particles. Under 465 nm excitation, intense red emission corresponding to 5D0→7FJ (J = 0, 1, 2, 3, and 4) transitions of Eu3+ ions were recorded in the photoluminescence (PL) spectra with an intense peak at 615 nm. The optimum concentration of Eu3+ ions was determined to be 1 mol% and the concentration quenching mechanism was due to the interaction between adjacent Eu3+ ions. The lifetime values of the samples were in the millisecond range and the internal quantum efficiency was determined to be 31.65 %. The Commission Internationale de l'Eclairage (CIE) coordinates of the optimum sample Mg0.99Ti2O5:0.01Eu3+ are (0.6421, 0.3575), lies in the red region with 99.9 % color purity and have warm correlated color temperature (CCT) values. Therefore obtained results suggest that the prepared Mg(1-x)Ti2O5:xEu3+phosphors can be used as an efficient red phosphor for w-LED applications.