White Light-emitting Diodes Research Articles

Proposal for Low-Cost Optical Sensor for Measuring Flow Velocities in Aquatic Environments.

The ocean, with its intricate processes, plays a pivotal role in shaping marine life, habitats, and the Earth's climate. This study addresses issues such as beach erosion, the survival of propagules from species like Posidonia oceanica, and nutrient distribution. To tackle these challenges, we propose an innovative sensor that quantifies hydrodynamic velocity by measuring the output voltage derived from detecting changes in light absorption and scattering using LEDs and LDRs. Our results not only demonstrate the effectiveness of the sensor but also the accuracy of the processing algorithm. Notably, the blue LED exhibited the lowest mean relative error of 7.59% in freshwater, while the yellow LED was most precise in chlorophyll-containing water, with a mean relative error of 6.80%. In a runoff simulation, we observed similar velocities with the blue, green, and white LEDs, 6.89 cm/s, 6.99 cm/s, and 7.05 cm/s, respectively, for nearly identical time intervals. It is important to highlight that our proposed sensor is not only effective but also highly cost-efficient, representing less than 0.43% of the cost of a Nortek Vector 6 MHz and 0.18% of the Teledyne Workhorse II 300 kHz Marine. This makes it a key tool for managing marine ecosystems sustainably.

Colloidal Synthesis of Blue-Emitting Cs3TmCl6 Nanocrystals via Localized Excitonic Recombination for Down-Conversion White Light-Emitting Diodes.

Lead-halide perovskite nanocrystals (NCs) have gained significant attention for their promising applications in lighting and display technologies. However, blue-emitting NCs have struggled to match the high efficiency of their red and green counterparts. Moreover, many reported blue-emitting perovskite NCs contain heavy metal lead (Pb), which poses risks to human health and the environment. In this study, we synthesized rare-earth-based Cs3TmCl6 NCs via the hot injection method, which exhibit a broadband blue emission at 440 nm. Combined experimental and theoretical studies indicate that the broadband emission in Cs3TmCl6 arises from self-trapped excitons due to the excited-state structural distortion of the [TmCl6]3- cluster. Furthermore, the ultrafast dynamics of charge carriers were analyzed using time-resolved photoluminescence and transient absorption measurements. Encouraged by the remarkable thermal, light, and water stabilities of Cs3TmCl6 NCs, as evidenced by experimental and theoretical results, a white light-emitting diode was further designed and fabricated using the Cs3TmCl6 NCs as the color converter. The device exhibits outstanding performance, achieving a long half-lifetime of 336 h and a large color-rendering index of 87.0. Combining eco-friendly features and a facile synthesis method, the rare-earth-based Cs3TmCl6 NCs mark a significant breakthrough as a reliable blue emitter, showcasing their future potential in lighting and display applications.

Anion regulation for surface passivation enables ultrahigh-stability perovskite nanocrystals.

All-inorganic perovskite CsPbBr3 nanocrystals (NCs) display high photoluminescence quantum yield and narrow emission, which show great potential application in optoelectronic devices. However, the poor environment stability of NCs will hinder their practical application. Herein, a series of ionic liquids with different anions (BF4-, Br-, and NO3-) were used as a sole capping ligand to synthesize NCs. Among the three samples, 1-hexadecyl-3-methylimidazolium tetrafluoroborate ([C16MIM]BF4) capped NCs have the highest stability in light, thermal, and water, possibly attributing to the in situ passivation of bromine vacancy via pseudohalogen BF4- and tight binding of ionic liquid ligands and lead atoms. In addition, green-emission [C16MIM]BF4 NCs were used to assemble a white light-emitting diode device, and it possessed a wide National Television System Committee color gamut of 124.5% and a stable emission peak at high driving currents of 380 mA. This work paves the way for resurfacing perovskite NCs with ultrahigh stability, thereby driving the perovskite NC display industry closer to real-world application.

Solvent-Free in Situ Synthesis of a CsPbBr3 Nanocrystal/ZrO2 Hybrid Phosphor with Excellent Thermal Stability for White Light-Emitting Diodes.

All-inorganic cesium lead halide perovskite CsPbX3 (X = Cl, Br, I, or mixed) nanocrystals (NCs) are emerging as promising candidates in light-emitting diodes (LEDs) owing to their excellent luminescent properties. However, CsPbX3 NCs are extremely susceptible to the elevated temperature associated with prolonged LED operation due to their low formation energy and soft ionic crystal structure. Here, CsPbBr3 NCs hybridized with ZrO2 were in situ synthesized by a rapid solvent-free method under an ambient environment for the first time, which was also suitable for large-scale production. The as-prepared CsPbBr3/ZrO2 hybrid phosphor not only presented enhanced photoluminescence (PL) properties but also exhibited improved thermal stability. For example, the PL intensity of the CsPbBr3/ZrO2 hybrid phosphor could retain 70% of the initial value at 130 °C, obviously higher than that of 34% for pure CsPbBr3. The exceptional thermal stability of the CsPbBr3/ZrO2 hybrid phosphor could be attributed to the introduction of ZrO2, which effectively preserved the initial perovskite structure of CsPbBr3 during heat treatment, as confirmed by XRD results. The as-prepared CsPbBr3/ZrO2 hybrid phosphor had great practical applications verified by the construction of white LEDs (WLEDs) with a luminance degradation of only 9% after continuous operation for 24 h at the initial luminance of 2000 cd m-2, which was significantly better than that of 63% for control WLEDs. The proposed thermally stable hybrid phosphor is expected to greatly contribute to the industrialization process of perovskites.

Defect-Enabled Superior Negative Thermal Quenching in Palmierite Ba9La(VO4)7:Eu3+ for WLED In Situ Temperature Measuring.

Negative thermal quenching (NTQ) of the phosphors is critically important for both scientific research and practical applications, but the design of efficient NTQ phosphors is still a challenging task. Herein, we report a new strategy for developing NTQ materials by cation-vacancy engineering. Specifically, a new color-tunable Ba9La1-x(VO4):xEu3+ (BLVO:xEu3+) phosphor with abundant intrinsic cation vacancy was developed, exhibiting superior NTQ behavior under 365 nm excitation. The NTQ performance can be modulated via adjusting Eu3+ doping levels, and the emission intensity of Eu3+ ions in the BLVO:0.20Eu3+ phosphor increased by 275% at 473 K compared to room temperature. Furthermore, the reported material emitting bright white light under 365 nm excitation was well-suited for use in white light-emitting diode (WLED) phosphor and fluorescent temperature sensors, exhibiting outstanding color-rendering index (90.1) in lighting and high sensitivity (Sa = 11.83% K-1, Sr = 2.33% K-1) in temperature detecting. Lastly, the operating temperature of WLED at different currents can be monitored and displayed in real time through emission spectroscopy. All of the results demonstrated that the designed NTQ BLVO:xEu3+ can be used as a single-phase white phosphor and optical thermometry. This work provides a fresh perspective for designing high-efficient NTQ phosphors and expands the application of phosphors in WLED in situ temperature detection.

Solvent mediated synthesis of multicolor narrow bandwidth emissive carbon quantum dots and their potential in white light emitting diodes

The development of efficient and environmentally sustainable materials for white light-emitting diodes (WLEDs) is of paramount importance in the field of lighting technology. In this study, we present a solvent-modulated synthesis approach for the fabrication of multicolor narrow-bandwidth emissive carbon quantum dots (CQDs) as a promising solution for constructing WLEDs. The synthesis method involves the controlled reaction of organic precursors in different solvent environments, leading to the formation of CQDs with distinct emission wavelengths with a relatively small full width at half maximum, ranging from 28 to 42 nm. Moreover, these synthesized multicolor CQDs demonstrate a remarkably high fluorescence quantum yield of up to 65%, indicating their potential for constructing efficient WLED when incorporated in polymer matrix and coated on the surface of blue light-emitting diode (LED).

Refractive blur’s influence on discomfort glare perception from white LED headlights at night

This study examined the effects of refractive blur on discomfort perception caused by peripheral glare from white LED passing (low)-beam headlights at night. The study compared two levels of binocular blur (+0.50 diopter [D] and +1.00D) against a baseline of optimal refractive correction. Thirty participants (mean age 21.3±1.6 years; range 20–24 years) simulating a driving position assessed discomfort from glare sources (headlights of oncoming vehicles) located at 40 and 20 m distances using the de Boer scale. The study found that, with a blur of +0.50D, discomfort glare from white LED headlights did not significantly differ from the baseline regarding de Boer scores. However, with a blur of +1.00D, de Boer scores significantly decreased, indicating increased discomfort glare compared with the baseline for all distances (P=0.004). These results suggest that refractive blur may contribute to an increased perception of discomfort glare during nighttime driving.

High color rendering index WLEDs enabled by multi-band tuning of InP quantum dots

Quantum dots (QDs) represent a significant class of fluorescent materials, offering the potential to reduce power consumption and enhance the color rendering index (CRI) of white light-emitting diode (WLED) devices. However, the presence of toxic elements such as Cd and Pb in traditional fluorescent QDs limits their widespread commercial application. Compared to the broad emission characteristics of environmentally friendly AgInS2 and CuInS2 QDs, the narrower linewidth of InP-based core-shell QDs is advantageous for developing WLED devices with a higher CRI. In this study, we employed a multistage heating method to synthesize a series of amino-phosphine-based InP/ZnSe core-shell QDs, which exhibited emission wavelengths ranging from 535 to 650 nm, narrow emission linewidths of 43-47 nm, and high photoluminescence quantum yields of 60%-80%. Subsequently, six different color QDs are used to fabricate a WLED device. The best WLEDs show not only bright warm light (correlated color temperature = 3323 K) with a maximum luminous efficacy of 74.1 lm W-1, but also excellent color quality (CRI Ra = 93, as well as R9 = 94.8, and R13 = 97.1). These results indicate remarkable progress in InP-based WLEDs for high-quality lighting applications.

Reconstructing reflective metamers: A comparative analysis of white LEDs with high and low colour rendering indexes

This study introduces an innovative method for reconstructing metamers, the aim is to identify metamerism when utilising white LEDs with high and low colour rendering. Two types of white LEDs were utilised as experimental light sources with two colour rendering indexes: high colour rendering (International Commission on Illumination (CIE) Ra of 95, TM-30 Rf of 92) and low colour rendering (CIE Ra of 78, TM-30 Rf of 78). Employ 741 training colours, principal component analysis was applied to extract basis function. Subsequently, 18 chromatic samples on ColorChecker colour chart were employed as target colours for spectrum reconstruction. Five sets of constraint were established to effectively filter potential metamers which are capable of inducing metamerism. Ultimately, three sets metamers were successfully reconstruct to differentiate white LEDs with high colour rendering, while an additional three sets of metamers were developed to distinguish white LEDs with low colour rendering. This outcome demonstrates the efficient method in reconstructing metamers to identify metamerism under high and low colour rendering white LEDs.

Fluorescent Tetraphenylethylene-Based Cerium Metal-Organic Frameworks for White-Light-Emitting Diodes.

Discovery of highly efficient and thermal stable phosphors is the focus of the studies in phosphor-converted white light-emitting diodes (LEDs). Herein, a tetraphenylethylene-based cerium metal-organic framework (SYNU-2) was synthesized and characterized. The intricate architecture of SYNU-2 shows an overall 3D → 3D 2-fold interpenetration framework. SYNU-2 exhibited good luminescence properties, and its latent fingerprint developer was prepared, which showed good fluorescence and stability under ultraviolet (UV) radiation. It is worth noting that a prototype WLED device can be designed using SYNU-2 and red phosphors (Ca,Sr)AlSiN3:Eu2+ with CIE coordinates of (0.33, 0.33) at an applied 3 V bias.

Realizing Near-Unity Photoluminescence Efficiency in Antimony-Doped Indium-Based Halides Induced by Strong Electron-Phonon Coupling.

Exploring a zero-dimensional (0D) hybrid halide with a large Stokes shift and efficient broad-band emission is highly desirable due to its enormous potential for solid-state lighting (SSL) application. However, it is still challenging to develop a highly emissive 0D hybrid halide with low toxicity and remarkable stability. Herein, we developed a novel indium-based metal halide A5In2Cl16·4H2O (A = doubly protonated 1,4-diaminobutane) whose inorganic octahedrons are completely isolated by the organic cations to form the 0D structure. Experimental and theoretical studies confirmed that Sb-doped A5In2Cl16·4H2O exhibits broad yellow emission with a photoluminescence quantum yield (PLQY) of up to 98%. The intense yellow emission can be attributed to the radiative recombination of triplet self-trapped excitons (STEs) in [SbCl6]3- octahedrons caused by the strong electron-phonon coupling. Benefiting from the excellent stability and photoluminescence performance, A5In2Cl16·4H2O:15%Sb was used as the yellow phosphor to prepare a white-light-emitting diode (WLED) device with a color rendering index of 87.8 and a luminous efficiency of up to 36.18 lm/W, demonstrating its potential in SSL applications. This work provides a guidance for developing environmentally friendly, efficient, and stable ultraviolet (UV)-excited broad-band emission materials.

Dual-shell protection enables highly efficient and stable all-inorganic perovskite composites for light-emitting-diodes

Lead-halide perovskite nanocrystals (NCs) present superior photoelectric properties, but the poor stability seriously hinders their practical application. The encapsulation of perovskite NCs inside mesoporous silica (m-SiO2) matrix is considered as one of the most feasible pathways to improve the stability of NCs. However, the challenges of loose encapsulation structure, aggregation of particles, high energy consumption during the preparation of CsPbX3@m-SiO2 composites have not yet been overcome, which throw a shadow over the large-scale commercial applications. Here, we present a dual-shell encapsulation strategy that enables the formation of highly emissive CsPbBr3@m-SiO2@SiO2 composites, achieving an exceptional photoluminescence quantum yield (PLQY) of 97.37 %. The reaction parameters for the preparation of composites are meticulous investigated. The CsPbBr3 NCs can be well formed inside the pores of m-SiO2 as the m-SiO2 is introduced into the precursor solution. The secondary SiO2 shells can effectively seal the open pores of m-SiO2. As a result, the as-prepared CsPbBr3@m-SiO2@SiO2 composites present excellent stability, in which the composites can maintain 93.16 % of initial intensity after storage for 84 days. Besides, a series of CsPbX3@m-SiO2@SiO2 composites with tunable emission wavelength in the range of 428.6–630.6 nm are prepared through facile designing the halide ratios of precursor solution, which present a wide color gamut (148.48 % of the National Television Standards Committee). In addition, a white light-emitting diode (LED) is fabricated by combining CsPbBr3@m-SiO2@SiO2 composites and K2SiF6:Mn4+ phosphors with a 455 nm LED chip, which exhibits good photoelectric performances. This facile low-temperature dual-shell encapsulation strategy reported here provides a new pathway for preparing high-performance perovskite composites, facilitating their practical photoelectric application.

Spectral characteristics and luminescence applications of Eu3+-activated fluorosilicate Na2MgGd2[SiO3]4F2

This work reports the luminescence spectra and application of novel Eu3+-doped Na2MgGd2[SiO3]4F2 phosphor. The X-ray powder diffraction confirmed the pure phase formation of the samples with the monoclinic space group P21/c (No:14). The phosphors demonstrated efficient red emission at 613 nm from the electric dipole transitions 5D0→7F2. The optimal doping concentration was found to be approximately 25 mol%. Na2MgGd2[SiO3]4F2:0.25Eu3+ exhibits a high quantum efficiency (QE) of 57 % with excellent thermal stability and pure chromaticity. Red- and the white light-emitting diode devices were packaged using InGaN chips and Na2MgGd2[SiO3]4F2:0.25Eu3+. The fabricated WLED has CIE coordinates of (x = 0.33, y = 0.34), which are very close to the white point in the National Television System Committee (x = 0.33, y = 0.33). The color rendering index (CRI, Ra) and correlated color temperature (CCT) of the WLED are 91 and 4400 K, respectively. The results show that as a red luminescent phosphor, it is a potential candidate for the preparation of near-UV/blue InGaN-based WLEDs.

Mn2+ doped aluminum-rich spinel transparent ceramic phosphor with higher performance for wide color-gamut backlight display

Due to the great potential of narrow-band green-emitting phosphors for wide color-gamut white light-emitting diodes (WLED) backlight displays, there is great interest in finding host materials with the desired luminescent properties and high quantum efficiency. Herein, a series of Mg0.98-xAl2(1+x/3)O4: 0.02Mn2+ (x = 0, 0.125, 0.25) powders were synthesized using high-temperature solid-phase reactions, followed by a combination of pressureless sintering and hot isostatic pressure sintering to fabricate transparent ceramic phosphors. The crystal structure refinement, NMR spectroscopy, and photoluminescence results show tetrahedral coordination of Mn2+ ions and an increase in cation vacancies and disorder with increasing x. These transparent ceramics exhibit narrow-band green emission, which shifts from 523 to 520 nm with increasing x. The Mg0.855Al2.08O4: 0.02Mn2+ ceramic sample has an in-line transmittance of over 80 % above 500 nm and internal quantum efficiencies as high as 96.2 %. The luminous intensity of the Mg0.855Al2.08O4: 0.02Mn2+ ceramic remains above 88.6 % at 425 K compared to room temperature, with a thermal conductivity of 12.4 W·m−1·K−1. A WLED device fabricated using the Mg0.855Al2.08O4: 0.02Mn2+ ceramic, K2SiF6:Mn4+ phosphors, and a blue chip show a wide color gamut of 126 % National Television System Committee standard. The results show that Mn2+-doped aluminum-rich spinel transparent ceramics have great potential for application in wide color gamut WLED backlight devices.

Investigation of structural, optical, dielectric, and electrical properties of NaMn4(PO4)3 (NMP) with fillowite-type structure

We synthesized sodium tetra manganese phosphate, NaMn4(PO4)3, by a solid-state method at a temperature of 900 °C for a duration of 10 h. The application of Rietveld analysis to the PXRD patterns revealed that the sample synthesized show the small amount of the secondary phase (Mn2P2O7). The NaMn4(PO4)3 compound belongs to the trigonal system, namely the R-3 space group. The powder's morphology was examined using scanning electron microscopy (SEM), which revealed an average grain size of approximately 7 μm. The powder underwent elemental analysis using energy dispersive X-ray spectroscopy (EDS), which confirmed the uniformity of the sample. Raman and Fourier transform infrared (FTIR) spectroscopies reveal the distinctive spectral peaks associated with P-O bonds in the (PO4)3- functional group. The optical bandgap energy of 1.57 eV was calculated using the diffuse reflectance technique with the Kubelka-Munk function and Tauc's relation. The chromatic coordinates of NaMn₄(PO₄)₃ suggest that the sample can generate blue-purple light, rendering it appropriate as a red phosphor in white light-emitting diodes (LEDs). Integrating this red emission with blue and green light from additional LED components might enhance the overall color quality and efficiency of white light generation. The dielectric properties of NMP exhibited characteristics that were consistent with ionic conductivity. The Nyquist plot displayed a conspicuous semicircle, indicating the presence of a dominant singular process, most probably linked to the bulk grain. The material demonstrates a significant degree of conductivity, with a measured value of around 3.72 × 10–4 S·cm-1 at a temperature of 300 °C.

The Modification Strategy of Biomass-Derived Full-Color Carbon Dots and Its Applications to Warm White Light-Emitting Diodes with Ultra-High CRI-96.2

The Modification Strategy of Biomass-Derived Full-Color Carbon Dots and Its Applications to Warm White Light-Emitting Diodes with Ultra-High CRI-96.2

Both the Positioned Supplemental or Night-Interruptional Blue Light and the Age of Leaves (or Tissues) Are Important for Flowering and Vegetative Growth in Chrysanthemum.

In this study, the effects of supplemental or night interruptional blue light (S-BL or NI-BL) positioning on morphological growth, photoperiodic flowering, and expression of floral genes in Chrysanthemum morifolium were investigated. Blue light-emitting diodes (LEDs) at an intensity of 30 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) were used for 4 h either (1) to supplement the white LEDs at the end of the 10 h short-day (SD10 + S-BL4) and 13 h long-day conditions (LD13 + S-BL4), or (2) to provide night interruption in the SD10 (SD10 + NI-BL4) and LD13 (LD13 + NI-BL4). The S-BL4 or NI-BL4 was positioned to illuminate either the shoot tip, the youngest leaf (vigorously growing the third leaf from the shoot tip), or the old leaf (the third leaf from the stem base). In the text, they will be denoted as follows: SD10 + S-BL4-S, -Y, or -O; SD10 + NI-BL4-S, -Y, or -O; LD13 + S-BL4-S, -Y, or -O; LD13 + NI-BL4-S, -Y, or -O. Normally, the LD13 conditions enhanced more vegetative growth than the SD10 periods. The growth of leaves, stems, and branches strongly responded to the S-BL4 or NI-BL4 when it was targeted onto the shoot tip, followed by the youngest leaf. The SD10 + S-BL4 or +NI-BL4 on the old leaf obviously suppressed plant extension growth, resulting in the smallest plant height. Under LD13 conditions, the flowering-related traits were significantly affected when the S-BL4 or NI-BL4 was shed onto the youngest leaf. However, these differences do not exist in the SD10 environments. At the harvest stage, other than the non-flowered LD13 treatment, the LD13 + S-BL4 irradiating the youngest leaf induced the most flowers, followed by the shoot tip and old leaf. Moreover, LD13 + NI-BL4 resulted in the latest flowering, especially when applied to the shoot tip and old leaf. However, the SD10 + S-BL4 or + NI-BL4 irradiated the shoot tip, youngest leaf, or old leaf all significantly earlier and increased flowering compared to the SD10 treatment. Overall: (1) Generally, vegetative growth was more sensitive to photoperiod rather than lighting position, while, during the same photoperiod, the promotion of growth was stronger when the light position of S-BL4 or NI-BL4 was applied to the shoot tip or the youngest leaf. (2) The photoperiodic flowering of these short-day plants (SDPs) comprehensively responded to the photoperiod combined with blue light positioning. Peculiarly, when they were exposed to the LD13 flowering-inhibited environments, the S-BL4 or NI-BL4 shed onto the leaves, especially the youngest leaves, significantly affecting flowering.

High color purity aluminate phosphor SryCa1-x-yAl12O19: xEu2+ for lighting and backlight display applications

In the context of the rapid advances in electronic information technology, the advancement of novel high-efficiency narrow-band blue phosphors represents a pivotal step in the advancement of high-quality liquid crystal displays (LCDs), as well as the development of white light-emitting diodes (WLEDs) with a reduced correlated color temperature (CCT). In this study, based on the sensitivity of Eu2+ emission to local environment, the alkaline earth aluminate material CaAl12O19 with high structural symmetry was selected as the matrix, and the symmetry of crystal structure was improved by replacing Ca2+ with Sr2+, the narrow-band emission of the phosphor is realized. The Sr0.9Ca0.09Al12O19: 0.01Eu2+ (SCAO: Eu2+) phosphor exhibited narrow-band emission with the full width at half maximum (FWHM) of 45.76 nm, and the colour purity of up to 95.46 %. Moreover, the internal quantum efficiency (IQE) of SCAO: Eu2+ has been demonstrated to reach 81.70 %. In addition, SCAO: Eu2+ phosphor, (Ba, Sr)2SiO4: Eu2+ phosphor, CaAlSiN3: Eu2+ phosphor, and 275 nm UVLED chips were combined to prepare white LED devices exhibiting a low color temperature (3733 K). The three-band LEDs of SCAO: Eu2+, β-Sialon: Eu2+ and K2SiF6: Mn4+ exhibited a colour gamut covering 84.75 % of the National Television Standards Committee (NTSC) standard. This indicates that the phosphor possesses the characteristics of a highly effective narrow-band blue-light-emitting substance with considerable potential for utilization in lighting and backlighting displays.

Full-Visible-Spectrum White LEDs Enabled by a Blue-Light-Excitable Cyan Phosphor.

Efficient blue-light-excitable broadband cyan-emitting phosphors may yield full-visible-spectrum white light-emitting diodes (WLEDs) with ultrahigh color rendering (Ra > 95). However, this requires closing the "cyan gap" in the 480-520 nm region of the visible spectrum, which is challenging. Herein, a well-performed cyan-emitting garnet phosphor Ca2LuAlGa2Si2O12:Ce3+ (CLAGSO:Ce3+) is reported. Under 430 nm excitation, the optimal CLAGSO:5%Ce3+ compound exhibits a broadband cyan emission (peak, 496 nm; bandwidth, 102 nm) with a high internal quantum efficiency of 85.6% and an excellent thermal resistance performance (69.1% at 423 K). Importantly, this as-prepared cyan-emitting phosphor provides sufficient cyan emission and enables filling the well-known so-called "cyan gap" between the blue LED chip and the commercial Y3Al5O12:Ce3+ (YAG:Ce3+) yellow phosphor. Impressively, a WLED device fabricated with the optimal CLAGSO:5%Ce3+ sample shows a low correlated color temperature (4053 K) and an ultrahigh color rendering index (Ra = 96.6), as well as an excellent luminous efficacy (74.09 lm W-1). These results highlight the importance of blue-excited broadband cyan-emitting phosphors in closing the cyan gap and enabling human-centric full-visible-spectrum warm WLED devices for high-quality solid-state lighting.

Two Organic-Inorganic Hybrid Manganese Bromides with Highly Efficient Emission toward White LEDs.

Organic-inorganic metal halides have attracted great attention due to their tunable structural and spectroscopic properties. Here, two organic-inorganic hybrid manganese bromides, (TEMA)2MnBr4 (TEMA = triethylmethylammonium) and (TEBA)2MnBr4 (TEBA = benzyltriethylammonium), are synthesized using the evaporation crystallization method. Following a heat-induced phase transition at 363 K, the structure and optical properties of (TEMA)2MnBr4 change but return to their initial state upon cooling to room temperature, as confirmed by X-ray diffraction, photoluminescence (PL), and Raman spectra. Meanwhile, (TEBA)2MnBr4, with a larger Mn-Mn distance, exhibits a higher photoluminescence quantum yield of 98.1% and greater thermal quenching temperature. However, due to the poorer thermal stability of the organic cation, the crystal melts at 400 K, leading to fluorescence quenching. White LEDs based on (TEMA)2MnBr4 and (TEBA)2MnBr4 are successfully fabricated with color rendering indices of 97.4 and 97.2, respectively. The investigation provides deep insights into the structural and optical properties of (TEMA)2MnBr4 and (TEBA)2MnBr4, advancing research for LED display design by tuning organic cations.