Warm White Light-emitting Diodes Research Articles

Development and Evaluation of a High-Efficacy Solar-Powered Light Trap for Rice Black Bug (Scotinophara Coartata) Management

Rice black bugs (RBB) are a major pest causing significant yield losses in rice farms. This study investigates a novel solar-powered light trap for RBB control. The trap utilizes LEDs with different color temperatures (warm white and daylight) and incorporates an auto-response system for efficient operation. Performance evaluation over three months revealed the highest efficacy for the 50-watt warm white LED bulb (948 grams captured), followed by the daylight bulb (724 grams). However, the study found no significant difference between developing light traps with warm white and daylight LED in capturing RBBs. The trap's functionality was excellent, with low maintenance requirements. These findings suggest that the solar-powered light trap with warm white LEDs offers a promising, sustainable solution for RBB management in rice production.

Phosphor Ceramic Composite for Tunable Warm White Light.

Composite phosphor ceramics for warm white LED lighting were fabricated with K2SiF6:Mn4+ (KSF) as both a narrowband red phosphor and a translucent matrix in which yellow-emitting Y3Al5O12:Ce3+ (YAG) particles were dispersed. The emission spectra of these composites under blue LED excitation were studied as a function of YAG loading and thickness. Warm white light with a color temperature of 2716 K, a high CRI of 92.6, and an R9 of 77.6 was achieved. A modest improvement in the thermal conductivity of the KSF ceramic of up to 9% was observed with the addition of YAG particles. In addition, a simple model was developed for predicting the emission spectra based on several parameters of the composite ceramics and validated with the experimental results. The emission spectrum can be tuned by varying the dopant concentrations, thickness, YAG loading, and YAG particle size. This work demonstrates the utility of KSF/YAG composite phosphor ceramics as a means of producing warm white light, which are potentially suitable for higher-drive applications due to their increased thermal conductivity and reduced droop compared with silicone-dispersed phosphor powders.

A comparative study on the impact of cation replacements on the structural, optoelectronic and thermodynamic characteristics of hexafluorides red phosphors Cs2MF6 (M = C, Ge, Pb, Si) using first-principles calculations: a prospect for warm-white LEDs (w-LEDs) applications

A comparative study on the impact of cation replacements on the structural, optoelectronic and thermodynamic characteristics of hexafluorides red phosphors Cs2MF6 (M = C, Ge, Pb, Si) using first-principles calculations: a prospect for warm-white LEDs (w-LEDs) applications

Efficacy and Optimal Timing of Warm-white or Red + Far-red LED Lamps in Regulation of Flowering in Long-day Ornamentals

When natural days are short, photoperiodic lighting at the end or beginning of the day (day extension) or in the middle of the night (night break) promotes flowering of long-day plants. The objective of this study was to compare broad-spectrum warm-white light-emitting diodes (LEDs) and red (R) + far-red (FR) LEDs at flowering regulation when delivered at different timings in the night period. We performed a greenhouse experiment on four long-day ornamentals [coreopsis (Coreopsis grandiflora) ‘Early Sunrise’, snapdragon (Antirrhinum majus) ‘Liberty Classic Yellow’, petunia (Petunia ×hybrida) ‘Easy Wave Burgundy Star’, and petunia ‘Wave Purple Improved’]. We grew plants under a truncated 8-hour photoperiod with or without low-intensity (∼2 μmol·m−2·s−1) nighttime lighting from warm-white or R+FR LEDs. For each light quality, we delivered four timings: 1) 8 hours after dusk; 2) 8 hours before dawn; 3) 4 hours after dusk + 4 hours before dawn; and 4) 4-hour night break. The effectiveness of floral promotion was determined by time from the treatment onset to the first open flower. Coreopsis flowered similarly under all lighting treatments, irrespective of light quality and timing, but did not flower under the short-day treatment by the end of the experiment. At flowering, coreopsis was 18% to 19% shorter under white than R+FR LEDs. In contrast, snapdragon flowered 9 to 20 days later under white than R+FR LEDs, when delivered for 8 hours at night, but flowered similarly under these two lamp types as a 4-hour night break. Compared with the short-day treatment, white and R+FR LEDs promoted flowering of both petunia cultivars, although flowering generally occurred later under white than R+FR LEDs. Snapdragon and petunia ‘Easy Wave Burgundy Star’ developed 30% to 122% more lateral branches under white than R+FR LEDs, when delivered for 8 hours at night. The effectiveness of warm-white LEDs was generally unaffected by timing, although it was most promotive of flowering in snapdragon when delivered for 8 hours before dawn. For R+FR LEDs, 8-hour day-extension lighting was generally more effective than 4-hour night-break lighting, irrespective of timing. We conclude when delivered for 8 hours at night, warm-white LEDs are generally less effective than R+FR LEDs at promoting flowering of long-day ornamentals but similarly effective as 4-hour night-break lighting. The effectiveness of day-extension lighting is generally independent of timing, although for R+FR LEDs, 8 hours after-dusk and/or before-dawn lighting was generally more effective than 4-hour night-break lighting.

Effectively enhanced the luminescent properties and water resistance of K2TaF7: Mn4+ red phosphors by introducing In3+ ions in the matrix and constructing a homogeneous core-shell structure

Shell-free K2Ta1-xInxF7: Mn4+ red phosphor was synthesized by introducing In3+ ions in K2TaF7: Mn4+ with a non-centrosymmetric octahedral structure. The strategy of the heterogeneous substitution of In3+ by Ta5+ further distorted the octahedral structure, effectively enhanced the emission intensity of Mn4+. Its overall luminous intensity was increased to 6.9 times that of K2TaF7: Mn4+. Moreover, the red phosphor with a homogeneous core-shell structure was successfully prepared by using a weak reducing agent citric acid to solve the problem of poor water resistance. After soaking in water for 10 days, the emission intensity of the red phosphor with a homogeneous core-shell structure retained 90% of the initial value. It is the first time to successfully construct a core-shell structure for A2BF7: Mn4+ type fluoride phosphors to effectively improve its water resistance. Mixing it with commercial YAG: Ce3+ yellow phosphor and encapsulating them with a commercial blue chip led to the development of warm white light-emitting diodes (WLEDs) with good qualities. K2Ta1-xInxF7: Mn4+ red phosphor with homogeneous core shell is a novel red phosphor with good luminous performances and excellent water resistance.

Highly efficient blue-light-excitable ultra-broadband orange-emitting Mg2.5Y1.5Al1.5Si2.5O12:Ce3+ garnet phosphors for solid-state lighting

Lighting and display technologies are revolutionized by the invention of YAG:Ce3+ phosphors driven by InGaN blue light-emitting diode (LED). Yet, the faint emission components in the red spectral region from typical LED devices can cause circadian rhythm disorders and aesthetic fatigue of the human eye. Developing broadband orange-emitting phosphor with abundant red coverage is one of the approaches for addressing this challenging problem. Herein, an innovative ultra-broadband orange-emitting Mg2.5Y1.5Al1.5Si2.5O12:Ce3+ (MYASO:Ce3+) garnet phosphor is successfully reported to bridge the above gap. The representative MYASO:4%Ce3+ sample exhibits an unexpectedly luminescence band with the full width at half maximum (FWHM) of up to 155 nm, the high thermal robustness (58%@423 K), and satisfactory internal quantum efficiency of 67% upon 465 nm blue light excitation. Such a large FWHM value results from the occupation of a single crystallographic site of Ce3+ in the dodecahedral [YO8] position of MYASO garnet host. Red-shift emission with respect to commercial YAG:Ce3+ is mainly attributed to the cooperative effect of the enhanced crystal field strength and increased Stokes shift. The emission intensity reduction at the high-temperature environment of MYASO:4%Ce3+ is derived from the enhancement of the thermal cross-relaxation associated with the larger Stokes shift (4839 cm−1). The resulting high-quality warm white LED device fabricated from the optimal MYASO:4%Ce3+ sample shows a satisfactory color rendering index (CRI = 84), comfortable correlated color temperature (CCT = 4032 K) and an excellent luminous efficacy (LE = 58.7 lm W−1) under a 60 mA drive current. These findings stimulate the exploration of ultra-broadband orange-emitting phosphors with abundant red emission to fabricate high-CRI warm-white LEDs for healthy solid-state lighting.

Spectral studies of thermally stable Dy3+/Sm3+ co-doped Li2Ba5W3O15 phosphors for warm white LEDs

In the current study, a series of Li2Ba5W3O15: RE3+ (RE = Dy, Sm) [LBW:Dy3+/Sm3+] phosphors were prepared using a high-temperature solid-state method. X-ray diffraction, Scanning electron microscopy with energy-dispersive x-ray analysis scans showed that the crystal form was consistent with the standard LBW and comprised small irregularly shaped particles. Diffuse reflectance spectral (DRS) data was utilized to calculate the band gaps. Fluorescence study shows that LBW material doped with Dy3+ and Sm3+ yield distinct colors at 496 nm (blue) for Dy3+ and 582 nm (green-yellow), 612 nm (yellow), and 669 nm (red) for Sm3+ when excited by near-ultraviolet (336 nm) light. The observation of energy transfer between Dy3+ and Sm3+ ions play a role in modifying the luminescence of LBW:Dy3+/Sm3+ co-doped phosphors. With a constant excitation wavelength (λ Ex), different levels of activator doping lead to a change in the emission colors from their neutral white light to a deep orange-red region for LBW:Dy3+/Sm3+ phosphors. The decay curves demonstrate a decrease in lifetime with an increase in the concentration of activator ions (Sm3+). For D3S5 phosphor, the temperature-dependent photoluminescence characteristics were analyzed under λ Ex = 336 nm excitation. The results indicate excellent luminescence thermal stability with an activation energy of 0.16 eV at λ Ex = 336 nm. With its low color-correlated temperature and good thermal stability, the prepared phosphor sample shows potential as a solid-state emitting phosphor that can be used with UV chip stimulation for warm white LED applications.

Er3+-activated Na0.5La0.5MoO4 multifunctional molybdate phosphors for optical thermometers and white LEDs

In this report, we have successfully prepared a series of Er3+-activated Na0.5La0.5MoO4 green molybdate phosphors by solid-state reaction. The X-Ray diffraction patterns confirmed that all diffraction peaks of Na0.5La0.5MoO4:Er3+ phosphors matched well with the standard data card with orthorhombic phase and the Rietveld refinement results indicated that the space group of the crystal structure was I41/a. Under 379 nm excitation, Na0.5La0.5MoO4:3%Er3+ phosphor exhibited strong green emission, with two strong emission peaks at 530 nm, 551 nm and a weak one centered at 656 nm, corresponding to the transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively. The experimental results showed that the optimal doping concentration of Er3+ was x = 3%, and electric dipole-dipole interaction was the major mechanism for the concentration quenching according to Dexter theory. Surprisingly, the optimal Na0.5La0.5MoO4:3%Er3+ phosphor presented thermal enhancement to the ratio of 2H11/2 → 4I15/2 transition to 4S3/2 → 4I15/2 transition in the elevated temperature range of 300–475 K. The maximum Sa and Sr were 1.79 × 10−2 K−1 and 1.094% K−1 respectively, which were applied to optical thermometers based on fluorescence-intensity-ratio technique. Furthermore, Na0.5La0.5MoO4:3%Er3+ phosphor had excellent thermal quenching performance (I425K/I300K = 93.47%) and high activation energy (Ea = 0.366 eV). Finally, the prepared Na0.5La0.5MoO4:3%Er3+ green phosphor, commercial BaMgAl10O17:Eu2+ blue phosphor and CaAlSiN3:Eu2+ red phosphor were combined with the 365 nm near-UV chip to produce a warm white LED device with high color index (Ra = 86.4) and low correlation color temperature (CCT = 4328 K). The above results suggested that the Er3+-activated Na0.5La0.5MoO4 multifunctional phosphors had considerable potential in the field of optical temperature measurement and phosphor-converted white light emitting diodes.

Tuning of emission in BaLa1−x−yGa3O7:xDy3+, yEu3+ by local symmetry effects for WLEDs

Melilite structured phosphor is a significant luminescent material, but limited by its structure and luminescent properties, its luminescence intensity and spectral composition cannot satisfy the application requirements. To solve this issue, we look into the connection for the first time between the amount of rare-earth elements added and the symmetry of structure in melilite phosphors. We got the results by looking at the PL spectral data and J-O parameters of the melilite phosphor BaLa1−x−yGa3O7:xDy3+,yEu3+. Dy3+ was located in the low symmetry site, resulting in the local asymmetry being successfully enhanced to obtain warm-white color coordinates (0.398, 0.393) by adjusting the concentration of Eu3+ to vary the Y/B ratio of Dy3+ and the R/O ratio of Eu3+. Meanwhile, in the way that energy is transferred with an electric quadrupole-electric quadrupole between phosphor dopant ions. The energy transfer efficiency of Dy3+-Eu3+ is up to 81.99 %. At 475 K, the phosphor maintains an intensity of 81.1 % and exhibits reliable thermal stability. The color purity and EQE of BLGO:0.40Eu3+ are 49.7 % and 38.56 %, respectively. These results reveal that modifying the local symmetry surrounding the doped ions allows for adjusting the luminescence's wavelength composition. This approach can be applied to phosphors generated for warm white light-emitting diodes (WLEDs) with a single matrix.

Efficient preparation strategy of high quantum yield multicolor CDs for warm white LED

Multicolor carbon dots (CDs) possess tremendous potential applications, especially in optoelectronic devices. However, further applications in warm white LED have been constrained due to the extremely low quantum yield (QY) of multicolor CDs. In this work, fluorescence enhancement multicolor CDs (o-CDs(cat.) (emitted yellow, Em = 550 nm, QY = 85.4 %), m-CDs(cat.) (emitted blue, Em = 440 nm, QY = 35.7 %), p-CDs(cat.) (emitted red, Em = 610 nm, QY = 73.8 %)) with almost 15 % QY improvement, without changing the fluorescence emission wavelength, was successfully achieved by introducing MnSO4 into the reaction system. The relevant mechanism may be the catalytic effect of MnSO4, which leads to the increased content of C = N and pyridine N, further suppressing non radiative transitions, leading to the increasement of QY. Finally, the obtained high QY multicolor CDs were applied to warm white LED with the color coordinates (CIE) of (0.33,0.36), color rendering index (CRI) of 90, correlated color temperature (CCT) of 3473 K. Laying the foundation for the research methods and mechanisms of metal ion caused high QY of CDs.

STUDY OF K2SiF6:Mn4+@SiO2 PHOSPHOR FOR WHITE LEDS WITH HIGH ANGULAR COLOR UNIFORMITY

The distinctive wide-band blue illumination absorption and red strait-line discharge of the phosphor K2SiF6:Mn4+ (KMnSF) make it an attractive material for manufacturing warm white light-emitting diodes (WLED). Nevertheless, using the highly corrosive raw ingredient HF to produce commercial KMnSF red phosphor has negative effects on the environment and people. In this study, microfluidic technology was used to successfully manufacture the KMnSF without the need for HF compound while resulting in a phosphor product with homogenous granule shape and size. The luminescence capabilities of the KMnSF samples were then thoroughly examined and characterized. Eventually, we made WLED packages comprising of blue LED chips, yellow phosphor Y3Al5O12:Ce3+ (YGA:Ce), red phosphor KMnSF, and SiO2 scattering particle. Via varying the SiO2 concentration during the simulation process, the prepared WLED’s optical performances are obtained. The scattering properties of the phosphor layer as well as the lighting transmission and distribution were simulated with the utilization of both LightTools software and Monte Carlo theory. According to the outcomes, the microfluidic-synthesized K2SiF6:Mn4+ proves to be appropriate for WLED apparatuses. Besides, the proposed phosphor compound with SiO2 scattering particles showed the improvement in luminous flux and angular uniformity of the WLED.

The effect of different light wavelengths on the germination of lettuce, cabbage, spinach and arugula seeds in a controlled environment chamber

The rapid development of vertical farming techniques in recent years has accelerated the necessity for a more thorough investigation into the utilization of artificial lighting. Cultivation in controlled environment systems primarily relies on artificial lighting to provide energy to the plants. One food category that has surged in popularity in recent years is microgreens, which are seedlings consumed during their early stages of growth. Hence, enhancing seed germination and promoting rapid seedling growth can yield significant benefits in this field. The main aim of this study was to analyze how lettuce, cabbage, spinach, and arugula seeds respond under various light spectra and photoperiodic schemes. The selected spectra were UV-A, blue, red, far-red, blue+red, blue+red+far-red, cool-white LED, warm-white LED and darkness, under three different photoperiods: 4, 12 and 24 h. All lighting treatments presented different effects on both seed germination and the morphological characteristics of the seedlings. Lettuce and spinach seeds exhibited robust germination capacity in both darkness and light. However, significant increases in germination rates were observed for cabbage and arugula when exposed to light. In the case of lettuce, a 12 h photoperiod with a blue spectrum led to a 100% germination rate and a leaf area of 77.4 mm². For cabbage, the highest germination rate observed was 70%, which occurred under a blue-red spectrum with a 12 h light cycle. The corresponding leaf area was 44 mm². Spinach exhibited its highest leaf area, reaching 119.16 mm², and a 90% germination rate when exposed to a four h far-red spectrum. Arugula achieved its greatest leaf area, measuring 58.57 mm², and a germination rate of 70% when exposed to a 24 h photoperiod combined with blue-red-far-red lighting. The proper combination of spectra can significantly enhance seed germination rates and guide the plants’ growth towards the desired morphological characteristics.

A new yellowish‐green‐emitting phosphor: Eu2+‐doped Ba3YAl2O7.5

AbstractA yellowish‐green emitting phosphor Ba3YAl2O7.5:Eu2+ was synthesized by a solid‐state method. The crystal structure, luminescence, concentration quenching, fluorescence decay, and thermal quenching properties were systematically investigated. Under blue light (440 nm) excitation, Ba3YAl2O7.5:Eu2+ phosphors exhibit a yellowish‐green emission peaking at 550 nm with a full width at half maximum ∼ 69 nm, and The Commission Internationale de l'Eclairage (CIE) coordinates of Ba3YAl2O7.5:Eu2+ are (0.4064, 0.5811). Structural analysis and Van Uitert equation along with fluorescence lifetime analysis reveal that Eu2+ ions occupy 6‐coordinated Y and 9‐coordinated Ba sites in Ba3YAl2O7.5, and therefore generate two emission sub‐bands at 582 and 548 nm. In addition, Ba3YAl2O7.5:Eu2+ phosphor remaining 43% photoluminescence emission intensity at 125°C with an activation energy of 0.372 eV. Utilizing the title phosphor (Ba3YAl2O7.5:3%Eu2+), commercial red (Ca,Sr)AlSiN3:Eu2+ (CSAlSi:Eu2+) phosphor, and InGaN‐based blue light emitting diode (LED) chip, a proof‐of‐concept warm white LEDs (WLEDs) with a color rendering index of 80.1, CIE chromaticity coordinates of (0.411, 0.381), luminous efficacy of ∼ 22.13 lm/W, and correlated color temperature of ∼ 3288 K is achieved. Thus, Eu2+ activated Ba3YAl2O7.5 phosphors have the potential application in WLEDs pumped by a blue LED chip for solid‐state lighting application.

Ce3+-Activated SrLu2Al3ScSiO12 Cyan-Green-Emitting Garnet-Structured Inorganic Phosphor Materials toward Application in Blue-Chip-Based Phosphor-Converted Solid-State White Lighting.

Phosphor-converted white-light-emitting diodes (WLEDs) with superhigh color rendering index (CRI) are the ongoing pursuit of next-generation solid-state lighting. One of the most important challenges is the limited improvement in CRI on account of the absence of a cyan component in the typical commercial combination. Here, a bright broad-band cyan-green-emitting phosphor with cubic garnet structure, SrLu2Al3ScSiO12:Ce3+ (SLASSO:Ce3+), was successfully reported, which can compensate for the absence of cyan cavity in the 480-520 nm blue-green emission region. With 439 nm blue-light irradiation, the as-fabricated SLASSO:Ce3+ phosphor yields a broad-band cyan-green emission with the maximum emission peak positioned at 525 nm and an appropriate full width at half-maximum (fwhm) of 111 nm, capable of providing more cyan emission component without sacrificing green emission. Meanwhile, the optimal SLASSO:2%Ce3+ phosphor features CIE color coordinates of (0.3254, 0.5470) with cyan-green hue, along with a high internal quantum efficiency of up to 93%. Additionally, thermal stability measurements at different temperatures reveal that the luminescence emission intensity of the proposed phosphor retains 44% of its original integral emission intensity at 423 K with respect to room temperature, while also demonstrating an excellent color stability (ΔE = 5.4 × 10-3). This work shows that the highly efficient SLASSO:Ce3+ garnet phosphor can be utilized as a potential cyan-green-emitting phosphor for filling the cyan gap, resulting in the construction of a high-quality warm WLED with high CRI for "human-centric" sunlight-like full-spectrum solid-state illumination.

Multiwavelength Excitation in Ho3+-Doped All-Inorganic Double Perovskites Achieved by Codoping Mn2+ for Warm-White LEDs and Plant Growth.

Doping lanthanide ions is an efficient method to modify the optical properties of lead-free double-perovskite halides. However, most lanthanide-doped double perovskites show a low luminescence efficiency and require a high excitation energy. Here, we have successfully prepared a series of Ho3+-doped Cs2NaBiCl6 microcrystals through a simple hydrothermal method and obtained strong characteristic emissions of Ho3+ at 492 and 657 nm under low-energy excitation (449 nm). After codoping Mn2+, apart from the characteristic emissions from Ho3+ under 450 nm wavelength excitation, the orangish-red luminescence consisting of the emission band centered at 591 nm from Mn2+ and a sharp emission peak at 657 nm from Ho3+ is obtained under 355 nm UV light excitation. Photoluminescence (PL) emission and excitation spectra, along with the PL decay curves, confirm the existence of an energy-transfer channel from Cs2NaBiCl6 to Mn2+ and then from Mn2+ to Ho3+. The enhanced absorption efficiency (10.5 → 70.7%) suggests that the codoping of Mn2+ overcomes the low absorption efficiency caused by f-f forbidden transitions of Ho3+. Finally, the diverse luminescent performance within the Cs2NaBiCl6:Ho3+, Mn2+ phosphor is realized by altering the excitation wavelength, thereby enabling its application in warm-white-light-emitting diodes and plant growth in this work.

Optical Management of Perovskite Solar Cells by Biomimetic‐Structured Polydimethylsiloxane Films

The application of antireflective (AR) films is a promising optical management strategy to improve the light utilization of perovskite solar cells (PSCs). Plumeria petals of different colors are employed as the master mold for the first time to prepare biomimetic AR films. Hierarchical morphologies replicated from the petals have a primary characteristic size in tens of micrometer scale. A strong scattering effect happens when the incident light hits the AR films, leading to a remarkably reduced reflectance with broadband enhancement of the transmission over the entire visible range. With the incorporation of the biomimetic AR film, the highest power conversion efficiency for PSCs reaches 23.56% with a large short‐circuit density (Jsc) of 26.54 mA cm−2, corresponding to an average enhancement of 6.17%. The enhancement effect is verified under 1.5G AM radiation with different tilted angles and warm white LED light source with different light intensities. Furthermore, optical simulations are performed to illustrate the structure–effective relationship. This work offers an interesting experience by learning from nature and provides valuable references for further refining the design of the AR films in micrometer scale.

Bright Blue Emission Lead-Free Halides with Narrow Bandwidth Enabled by Oversaturated Europium Doping.

Eu2+-based lead-free metal halide nanocrystals (LFMH NCs), including CsEuCl3 NCs and CsX:Eu2+ NCs (X = Cl or Br), exhibit highly efficient narrow-band blue photoluminescence, making them competitive candidates for next-generation lighting and displays. However, the growing mechanism of the aforementioned NCs lacks in-depth study, which hinders the development of Eu2+-based nanomaterials. Herein, we demonstrate the colloidal synthesis of CsBr:Eu2+ NCs based on an air-stable europium source. The NCs show deep blue photoluminescence centered at 444 nm, with a maximum photoluminescence quantum yield (PLQY) reaching 53.4% and a fwhm of 30 nm. We further reveal the mechanism that determines CsBr host growth and Eu2+ doping in CsBr:Eu2+ nanocrystals, especially dopant trapping and self-purification, that determine the PLQY level. Pure white, warm white, and cold white LEDs are fabricated based on CsBr:Eu2+ NCs, red and green phosphors, and their performance suits the needs of high-quality lighting.

Emission enhancement in the luminescence performance of warm red light-emitting LiSrVO4 :Pr3+ phosphors.

Warm red-emitting praseodymium-doped LiSrVO4 phosphors were synthesized via solid-state reaction. The phase formation was verified using an X-ray diffraction study and the morphology was investigated using a scanning electron microscope study. The LiSrVO4 :Pr3+ phosphors emitted red light when exposed to ultraviolet light, indicating their possibility for use in warm white light-emitting diodes (WLEDs). Furthermore, the effect of charge compensators on the luminescence characteristics was addressed. The decay time was investigated using time-resolved photoluminescence. Furthermore, thermal quenching was analyzed through temperature-dependent photoluminescence spectra. Their sensitivity was calculated using temperature-dependent decay time analysis. The colour purity of the emitted light could be measured by photometric analysis. This comprehensive investigation provides a thorough understanding of the luminescence properties of phosphors for WLED applications.

The design and synthesis of 1-phenylimidazo[1,5-a]pyridine – anthracene-based fluorophore for greenish-yellow organic light emitting diode and warm white LED

Solution-processed OLEDs offer a promising and affordable technology for solid-state lighting and superior self-luminous display panels. Herein, an imidazo[1,5-a]pyridine (ImPy)-based fluorophore decorated with an aromatic π-system anthracene is synthesized by a one-pot condensation approach. From the theoretical study, the energy difference between HOMO and LUMO is 3.1 eV. The molecule shows excellent thermal stability and electrochemical stability. It exhibits efficient intramolecular charge transfer and displays a positive solvatochromic photoluminescence emission band ranging from 528 nm in hexane to 586 nm in acetonitrile with large Stokes’ shift of ∼11,000 cm−1. The OLEDs made of this emitter displayed good device performance with luminous efficiency of 4.4 cd A–1, power efficiency of 2.2 lm W–1 and external quantum efficiency of 3.2%. Additionally, this OLED emitted greenish-yellow light with CIE coordinate (0.34, 0.45) and possessed a low turn-on voltage of 7 V. The material also used in white LED fabrication and the fabricated white LED displayed an excellent color rendering index (CRI), the luminous efficiency of radiation (LER), and correlated color temperatures (CCT) of 89328 lm W–1 , and 4907 K, respectively with CIE coordinate (0.35,0.32).

One-pot synthesis of high-efficiency one-dimensional perovskite phosphor for warm white LEDs

A simple one-pot method was used to synthesize one-dimensional perovskite phosphor, which was characterized using X-ray diffraction, scanning electron microscopy, and photoluminescence spectroscopy. The material demonstrates excellent photoluminescence properties and can emit warm white light with a color temperature of 4710 K and a color rendering index of 84.6. The simple one-pot method makes it easy to synthesize the perovskite phosphor, positioning it as a promising candidate for the production of warm white LEDs. This work provides a detailed analysis of the material's crystal structure and photoluminescence properties.