Component For White Light Emitting Diodes Research Articles

A prime red phosphor Ca3Gd(AlO)3(BO3)4:Eu3+ with high color purity for low color temperature pc-WLEDs

A series of excellent thermal stability red phosphors Ca3Gd(AlO)3(BO3)4:Eu3+ were synthesized by conventional solid-state reaction method. Through the fluorescence spectrometer, the research results make clear that this phosphor has a best excitation wavelength of 396 nm, and 0.7 mol% of doping is optimal. The interaction between ions causes a concentration-quenching phenomenon when the doping concentration is too high. Under the excitation of 396 nm ultraviolet light, there is a significant emission peak at 623 nm due to the energy level transition of 5D0→7F2 in the outer layer of the fluorescent powder. The color purity of the Ca3Gd0.3(AlO)3(BO3)4:0.7Eu3+ is 98.8 %, which means the corresponding red light emitted can effectively compensate for the missing red light component in white light-emitting diodes(WLEDs). The operating temperature of WLED typically hovers around 150 degrees Celsius. At such temperatures, the luminous efficiency of fluorescent powders remains remarkably resilient, peaking at 94.84 % relative to room conditions. Even when the temperature surges to 200 degrees Celsius, the luminous efficiency of fluorescent powders persists at an impressive 88.87 %. The energy band gap of Ca3Gd0.3(AlO)3(BO3)4:0.7Eu3+ is up to 5.05 eV, which further demonstrates its excellent thermal stability. Ca3Gd0.3(AlO)3(BO3)4:0.7Eu3+ phosphor used in the WLED device emits warm white light (CCT = 3628 K, CRI = 87.4). As a result of these results, the phosphor can be used as an excellent red light component in pc-WLEDs.

Tailoring robust luminescent-based BaSrY4O8: Eu3+ platform opens new avenues for screening diverge surface prompted cheiloscopy, WLED's, and dosimetric applications

The discovery, evaluation, and manipulation of material can open new avenues in different technological applications in a real-time practical implementation scenario is highly necessary. In this regard, the present work deals with the synthesis of a series amber-red color emitting BaSrY4O8:Eu3+(1–9 mol %) nanophosphors followed by a solution combustion route. X-ray diffraction studies of the prepared phosphors confirmed the orthorhombic phase with Pnma (62) space group. Scanning electron microscopy results revealed that the particles are dumbbells in shape with network-like structures. From diffuse reflectance spectroscopy data, the energy band gap was estimated and found to be ∼5.72–5.92 eV. The photoluminescence emission spectra of the prepared nanophosphors consist of intense and sharp peaks located at ∼ 578, 594, 612, 650, and 708 nm, which attributed to 5D0→7F0, 5D0→7F1,5D0→7F2,5D0→7F3 and 5D0→7F4 transitions of Eu3+ ions, respectively. The estimated Commission International de I'Eclairage color coordinates were found to be tuned from pink to amber-red region. Thermoluminescence glow curve of BaSrY4O8: Eu3+ (5 mol %) nanophosphor after irradiated with various γ –ray doses ranging from 1 to 8 KGy exhibits a broad band with maximum intensity at 340 °C. Thanks to intensive luminescence and nano-regime of the nanophosphor, which enable latent lip prints to visualize on various non-porous surfaces by revealing defined type I–V groove patterns without any background hindrance or color distraction under the excitation. The aforementioned results create new perspective avenues by demonstrating the versatility of the prepared nanophosphor as an excellent red component for white light-emitting diodes, dosimetry, and cheiloscopy applications.

Eu3+ Activated Red Phosphor Ca3 YAl3 B4 O15 with Low Thermal Quenching Behavior.

This paper reports a sequence of Ca3 YAl3 B4 O15 : xEu3+ red phosphor prepared by a high-temperature solid-state reaction. At the excitation of 396 nm, the samples emit intense red emission centered around 623nm, which can be attributed to the 5 D0 →7 F2 transition of the Eu3+ ion. The results showed that the optimum Eu3+ doping concentration of Ca3 YAl3 B4 O15 : Eu3+ phosphor is x= 80mol%, and the concentration quenching mechanism of Ca3 YAl3 B4 O15 : Eu3+ red phosphor belongs to the exchange coupling between Eu3+ ions. The CIE coordinate and color purity of Ca3 Y0.2 Al3 B4 O15 : 0.8Eu3+ were calculated as (0.6375, 0.3476) and 95.5%, respectively. Moreover, the red emission of the obtained phosphor Ca3 YAl3 B4 O15 : 0.8Eu3+ exhibits low thermal quenching behavior with an intensity retention rate of 92.85% at 150 °C. The above results manifest that the Eu3+ -activated Ca3 YAl3 B4 O15 phosphor is predicted to be a promising red luminescent component for the white light-emitting diodes.

Double Perovskite Mn4+-Doped La2CaSnO6/La2MgSnO6 Phosphor for Near-Ultraviolet Light Excited W-LEDs and Plant Growth.

Non-rare earth doped oxide phosphors with far-red emission have become one of the hot spots of current research due to their low price and excellent physicochemical stability as the red component in white light-emitting diodes (W-LEDs) and plant growth. Herein, we report novel Mn4+-doped La2CaSnO6 and La2MgSnO6 phosphors by high-temperature solid-phase synthesis and analyzed their crystal structures by XRD and Rietveld refinement. Their excitation spectra consist of two distinct excitation bands with the dominant excitation range from 250 to 450 nm, indicating that they possess strong absorption of near-ultraviolet light. Their emission is located around 693 and 708 nm, respectively, and can be absorbed by the photosensitive pigments Pr and Pfr, proving their great potential for plant growth. Finally, the prepared samples were coated with 365 nm UV chips to fabricate far-red LEDs and W-LEDs with low correlation color temperature (CCT = 4958 K/5275 K) and high color rendering index (Ra = 96.4/96.6). Our results indicate that La2CaSnO6:Mn4+ and La2MgSnO6:Mn4+ red phosphors could be used as candidate materials for W-LED lighting and plant growth.

Novel double molybdate LiLu(MoO4)2:Sm3+ red phosphors with excellent thermal stability for white LEDs

A series of LiLu(MoO4)2:Sm3+ red phosphors with high thermal stability were synthesized by sol-gel method. The crystal structure, morphology, concentration-dependent luminescence spectra and temperature-dependent luminescence spectra/decay times of the phosphors were systematically investigated. The LiLu(MoO4)2:Sm3+ phosphors have a scheelite structure with tetragonal system. Under the UV excitation of 405 nm, the LiLu(MoO4)2:Sm3+ phosphors emit red light centered at 648 nm corresponding to the 4G5/2→6H9/2 transition of the Sm3+ ion. LiLu(MoO4)2:Sm3+ red phosphors exhibited high color purity (98.84%) and a CIE coordinate (0.5806, 0.4145). The LiLu(MoO4)2:Sm3+ phosphors also demonstrate an excellent luminescence thermal stability (the luminescence intensity at 473 K remains 93% of that at 298 K). These experimental results demonstrate the potential application of LiLu(MoO4)2:Sm3+ phosphor in the red component of white light-emitting diodes.

Combustion-assisted Ca8.25 Na1.5 Al6 O18 :Sm3+ phosphors for solid-state lighting and WLED applications.

Aluminate-based phosphors have been the most investigated luminescent phosphors over decades due to their outstanding optical properties. In the proposed work, a series of Sm3+ -doped Ca8.25 Na1.5 Al6 O18 (CNAO) phosphor sample was prepared using a simple combustion technique with the help of two fuels i.e., urea-glycine. The purity of phase and structural analysis of the CNAO phosphors were confirmed using X-ray diffraction analysis. Vibrational features of this phosphors confirmed were via Fourier transform infrared analysis. A photoluminescence study of this phosphor showed a doublet emission at 568 and 576 nm in the yellow region attributable to the 4 G5/2 →6 H5/2 transition of Sm3+ ions, whereas a doublet peak noticed in red region ranged from 600 to 620 nm and was attributable to the 4 G5/2 →6 H7/2 transition of Sm3+ ions. Moreover, Commission Internationale de l'éclairage colour coordinates were also located in the yellowish-red region and confirmed the potential of this phosphor as a yellowish-red component for white light-emitting diodes and display devices applications.

Fabrication of high-efficiency YAG:Ce3+ phosphors via concurrent optimization of firing atmosphere and fluxing agent

Y3Al5O12:Ce3+ (YAG:Ce3+) phosphors are common components of white light-emitting diodes. However, the efficiency of the phosphor synthesis process remains inadequate. Particularly, when synthesizing YAG:Ce3+ samples from oxide raw materials, it is necessary to reduce CeO2 to Ce3+, which is the luminescent central ion, in a reducing gas atmosphere. However, the defects that form in a Y3Al5O12 matrix in a reducing gas atmosphere cause photoluminescence property degradation. Therefore, this study was designed for fabricating highly efficient YAG:Ce3+ samples with high internal quantum efficiency. We achieved an internal quantum efficiency of 99.5% by concurrently optimizing the fluxing agent and the phosphor synthesis conditions. Specifically, by optimizing the species and proportions of the fluoride and carbonate fluxing agents and sintering them with oxide materials, we could increase the percentage of Ce3+ that contributes to photoluminescence and suppresses defect generation, which significantly improved the internal quantum efficiency of the phosphors.

Crystal structure, luminescence properties and thermal stability of novel Sr2CaLa(VO4)3: Sm3+ phosphor synthesized by the combustion method

Sr3-xCaxLa(VO4)3: Sm3+ (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5) and novel Sr2CaLa(VO4)3: ySm3+ (SCLVO: ySm3+, y = 0.01, 0.03, 0.05, 0.07, 0.09) phosphors were synthesized by the citric acid-assisted sol-combustion method. The crystal structure, morphology, concentration-dependent emission spectrum, decay time, and thermal stability of phosphors were studied. These synthesized phosphors have a hexagonal structure with a space group of R-3 m (166). High-purity Sr3-xCaxLa(VO4)3: Sm3+ phosphors were obtained when x < 2.5. The change in particle shape and unit cell parameters of the Sr3-xCaxLa(VO4)3: Sm3+ phosphors led to reduced luminescence performance when the Ca2+ concentration was x > 1. The optimal doping concentration of Sm3+ in the SCLVO host is 3 mol%. Under the excitation of 402 nm near-ultraviolet (NUV) light, all phosphors in this series emit orange–red light at 603 nm, which is attributed to the 4G5/2→6H7/2 transition of Sm3+. The SCLVO: 0.03Sm3+ phosphor exhibits a double exponential decay time of 0.872 ms, excellent thermal stability with an activation energy Ea of 0.232 eV, a chromaticity coordinate of (0.5817, 0.4136), and a high color purity of 98.48%. These experimental results demonstrate the potential application of phosphor SCLVO: 0.03Sm3+ in the red component of white light-emitting diodes (WLEDs).

Charge compensation effects of alkali metal ions M+ (Li+, Na+, K+) on luminescence enhancement in red-emitting Ca3Si2O7:Eu3+ phosphors

Red-emitting Ca3Si2O7:Eu3+ and Ca3Si2O7:Eu3+, M+ (M = Li, Na, K) phosphors were prepared via a solid-state reaction. The effects of Eu3+ doping concentration and alkali metal ions M+ co-doping on the structure and luminescence performance of Ca3Si2O7:Eu3+ were investigated. X-ray diffraction patterns demonstrated that the Ca3Si2O7:Eu3+ phase synthesized at 1400 °C was consistent with the standard Ca3Si2O7 structure. Characteristic emission peaks of Ca3Si2O7:Eu3+ phosphors were revealed at 593 nm and 617 nm under excitation at 394 nm, which relate to the 4f electron transitions of Eu3+ ions. After co-doping M+ as a charge compensator, the luminescence intensity of red-emitting Ca3Si2O7:Eu3+, M+ phosphors were significantly improved by 2.62-, 1.80-, and 2.92-fold for Li+, Na+, K+ co-doping, as well as the luminescence lifetime compared with that of Eu3+-doped Ca3Si2O7. Moreover, actual LEDs with excellent chromaticity parameters were manufactured via coating the as-prepared phosphor onto a 395 nm n-UV chip. All results indicate that the Ca3Si2O7:Eu3+, M+ red-emitting phosphor has an excellent potential application as a red component in white light-emitting diodes.

Effect of Li+ doping on the luminescence performance of a novel KAlSiO4:Tb3+ green-emitting phosphor

A new green-emitting phosphor, KAlSiO4:1.5 mol% Tb3+, x mol% Li+, was prepared via a high-temperature solid-phase method, and its crystal structure, diffuse reflectance spectrum, and luminescence were studied. The results show that the Li+ doping shifts the strongest diffraction peak to a high angle direction, reducing grain size by 11.4%. The entry of Li2CO3 improves the luminescence performance of KAlSiO4:1.5 mol% Tb3+. At a Li+ concentration of 1.5 mol%, the sample has strong absorption in the ultraviolet light range from 250 to 400 nm. The luminous intensity of the sample at 550 nm approximately quadruples after Li+ doping. Additionally, the colour purity of the sample and the internal quantum yield increase to 83.3% and 42%, respectively. The sample changes colour with time when exposed to air without an obvious fading phenomenon. The emission intensity at 200 °C is 95.1% of its value at room temperature, indicating that the phosphor has excellent thermal stability when x = 1.5. These results show the feasibility of using the silicate phosphor for generating the green light component of white light-emitting diodes for solid-state lighting.

Effect of A+ (A = Li, Na and K) co-doping on enhancing the luminescence of Ca5(PO4)2SiO4:Eu3+ red-emitting phosphors as charge compensator

A series of Ca5-x(PO4)2SiO4:xEu3+ red-emitting phosphors were synthesized through solid-state reaction, and alkali metal ions A+ (A = Li, Na and K) were co-doped in Ca5(PO4)2SiO4:Eu3+ to improve its luminescence property. The impacts of synthesis temperature, luminescence center Eu3+ concentration and charge compensator A+ on the structure and luminescence property of samples were studied in detail. X-ray diffraction results indicated that prepared Ca5(PO4)2SiO4:Eu3+, A+ had a standard Ca5(PO4)2SiO4 structure with space group P63/m. Under the excitation of 392 nm, Ca5(PO4)2SiO4:Eu3+ phosphors showed a red emission consisting of several emission peaks at 593 nm, 616 nm and 656 nm, relevant to 5D0→7F1, 5D0→7F2 and 5D0→7F4 electron transitions of Eu3+ ions, respectively. Luminescence intensity and lifetime of Ca5(PO4)2SiO4:Eu3+ can be significantly enhanced through co-doping alkali metal ion A+, which play an important role as charge compensator. The results suggest that Ca5(PO4)2SiO4:Eu3+, A+ red phosphors with excellent luminescence property are expectantly served as red component for white light-emitting diodes excited by near-ultraviolet.

Luminescence Properties of Si4+-doped LiZnPO4:Eu3+ and Application in the Development of Latent Fingermarks

Si4+ and Eu3+ co-doped LiZnPO4 phosphors (LZPS:Eu3+) with red luminescence were prepared by high temperature solid-state reaction. The maximum photoluminescence intensity is achieved at the Eu3+ content of 12% (molar concentration). The study also investigated the effect on luminescent properties of LiZnPO4:Eu3+ by the introduction of Si4+ into the host to substitute P5+. The Eu3+ emission intensity at 592 nm and 612 nm is enhanced by 105% and 108%, respectively. Decreasing the amount of Eu3+ significantly reduces the raw material costs. The phosphor is efficiently excited under 395 nm and 254 nm ultraviolet radiation, and is used as the red component in white light-emitting diodes (WLEDs) or fluorescent lamps. The excitation spectra consist of a broad band extending 200–280 nm and a series of sharp peaks extending 310–500 nm, centered at 395 nm, which corresponds to the charge transfer band of O2− → Eu3+ and the f → f transition of Eu3+, respectively. The study applies this distinctly bright phosphor in the detection and imaging of lipid fingermarks on common non-porous and semi-porous substrates such as colored paper, glass, porcelain, and leather, etc. All results indicate that the LZPS:Eu3+ phosphor is an ideal detection powder for background interference reduction due to its high fluorescence brightness which offers high contrast images, which is applicable to the development of fingermarks on the common non-porous and semi-porous substrates.

Eu3+-doped fluoro-telluroborate glasses as red-emitting components for W-LEDs application

From 0.1 up to 2.5 mol% Eu3+-doped fluro-telluroborate glasses as red light-emitting components for white-light-emitting diodes (WLEDs) were investigated. Non-periodicity in the atomic arrangements was studied through the XRD pattern. The photoluminescence (PL) spectra were recorded under blue light (464 nm) excitation and analyzed. All the PL spectra exhibit an intense peak at 612 nm for 5D0 → 7F2 transition, revealing their red photoemission. Optimal PL emissions were achieved for 1.0 mol% Eu3+-doped sample. The CIE chromaticity coordinates for all the glasses (x = ~0.69, y = ~0.30) fall within the red color region. The J‒O parameters (Ω2, Ω4) were calculated following the emission spectra of Eu3+-doped samples and the intensity parameters (Ω2>Ω4), as well as the high asymmetry ratio (R/O), indicate the low ionicity in all the studied glasses. Using the J-O parameters, several radiative features like total emission transition probability (AT), branching ratios (radiative (βR) & experimental (βexp)), stimulated emission cross-section (σPE), gain bandwidth (σPE × λeff), and optical gain (σPE × τrad) were evaluated. All the luminescence decay curves fit well to non-exponential function and decay times were decreased at Eu3+ concentration >0.5 mol%. The evaluated σPE = 19.684 × 10−21 cm2, βexp = 0.759, τexp = 1.325 m s, minimum non-radiative relaxation, WNR = 296/s, and 60.78% of quantum efficiency (η) for 1.0 mol% Eu3+-doped glass for 5D0 → 7F2 transition indicates its promising features for red light-emitting optical devices and also as a red component in WLEDs.

Blue-light excitable La2Ce2O7:Eu3+ red phosphors for white light-emitting diodes

Inorganic phosphors which can be effectively excited with blue-light are highly desirable for white light-emitting diodes (WLEDs). Herein, Eu3+-activated La2Ce2O7 phosphors are prepared by a self-rising reaction using urea and glycine as leavening agents under hydrothermal conditions. The phosphors display a well-distributed round or elliptical particle shapes with an average diameter of about 55 ± 10 nm. The excitation spectrum is dominated by the 7F0→5D2 transition (∼465 nm) that overlaps the emission of efficient blue emitting LEDs, rendering these phosphors as very attractive as blue down converters. The luminescence performance can be effectively improved by optimizing the molar ratios of leavening agents and the content of Eu3+ concentration and, thus, the absolute quantum yield can reach 0.229 ± 0.023. By combining a commercial blue emitting LED chip (InGaN, 465 nm) and the phosphors, intriguing efficient pure red emission is achieved with International Commission on Illumination (CIE) color coordinates of (0.669,0.330). This pure red emission is used to tune the well-known poor correlated color temperature values of WLEDs based on YAG:Ce3+. WLEDs are fabricated by coating LED chips emitting in the blue with blends of YAG:Ce3+ and Eu3+-activated La2Ce2O7, yielding prototypes with enhanced color rendering index that is easily adjusted from 7119 to 3242 K, demonstrating that this strategy may use to complement the red component in WLEDs.

Stabilizing Fluoride Phosphors: Surface Modification by Atomic Layer Deposition

The use of an Al2O3- or TiO2-coated layer, deposited by using atomic layer deposition (ALD), was explored to improve the adhesion properties of fluoride phosphor particles. K2SiF6:Mn4+ was investigated as a benchmark fluoride phosphor. Mn4+-doped fluoride phosphors show a narrow red emission band centered at around 630 nm, making them suitable candidates for the red component in white light-emitting diodes. In lighting applications, red fluoride phosphors can lower the correlated color temperature without sacrificing the luminous efficacy of the radiation. In displays, their saturated red emission enlarges the color gamut. Although attractive optical properties are provided by fluoride phosphors, a remaining hurdle is their sensitivity to moisture, which leads to phosphor degradation. Protective hydrophobic shells can be used to enhance the moisture stability of phosphor materials. For fluoride phosphors, the surface fluorine inhibits a good adhesion between the core and shell, potentially leading to delamination of the shell with time. Ideally, the thin ALD-deposited seed layers provide an OH-saturated particle surface, offering an enhanced adhesion to outer moisture barrier layers or hydrophobic encapsulants. The results obtained indicate that the Al2O3 seed layers suffered from delamination and blistering after deposition, related to surface reactions during ALD. In contrast to Al2O3, the TiO2 layer could be grown with high uniformity and conformality. In a final step, the ALD-coated fluoride powders were successfully made hydrophobic using a nonchlorinated hydrophobic precursor.

Optimized photoluminescence properties of a novel red phosphor LiSrAlF6:Mn4+ synthesized at room-temperature

A red phosphor with a broad excitation band in blue region and sharp emission peaks in red region is needed for compensating the red components of white light-emitting diodes (WLEDs) by converting blue light with a yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce). The red phosphor LiSrAlF6:Mn4+ (LSAF:Mn) with morphology of flaky particles about 50 μm in diameter has been synthesized by an ion-exchange reaction route at room-temperature in air. The as-synthesized phosphors were characterized by x-ray powder diffraction (XRD), scanning electron microscope (SEM), and temperature-dependent photoluminescence (PL) spectra. The excitation spectrum of LSAF:Mn shows a broad-band excitation from 400 to 500 nm that is due to the spin-allowed transition of 4A2g → 4T2g of Mn4+, indicating a potential application for solid state lighting. The optimal PL intensity of the phosphor LSAF:Mn has been obtained by optimizing the synthetic parameters.

Influence of Bi3+content on photoluminescence of InNbO4:Eu3+,Bi3+for white light-emitting diodes

AbstractA series of red-emitting phosphors InNbO4:Eu3+,Bi3+was prepared by a high temperature solid-state reaction. The structure, size distribution and luminescence properties of the phosphors were respectively characterized by X-ray diffraction (XRD), laser particle size and molecular fluorescence spectrometer. The XRD results indicate that the phase-pure samples have been obtained and the crystal structure of the host has not changed under the Eu3+and Bi3+co-doping. The test of size distribution shows that the phosphor has a normal size distribution. The excitation spectra illustrate that the dominant sharp peaks are located at 394 nm (7F0→5L6) and 466 nm (7F0→5D2). Meanwhile, the emission spectra reveal that the phosphors excited by the wavelength of 394 nm or 466 nm have an intense red-emission line at 612 nm owing to the5D0→7F2transition of Eu3+. Bi3+doping has not changed the peak positions except the photoluminescence intensity. The emission intensity is related to Bi3+concentration, and it is up to the maximum when the Bi3+-doping concentration is 4 mol%. Due to good photoluminescence properties of the phosphor, the InNbO4:0.04Eu3+,0.04Bi3+may be used as a red component for white light-emitting diodes.

Hierarchical zinc aluminate 3D nanostructures, synthesized by bio-inspired ultrasound assisted sonochemical route: Display and dosimetry applications

ZnAl2O4:Tb3+ (0.25–5mol%) nanophosphors were synthesized by ultrasound assisted sonochemical route using bio-sacrificial Aloe Vera (A.V.) gel as a template. The effect of sonication time, A.V. gel concentration, pH value, sonication power and temperature on the morphologies of the prepared samples were systematically explored and discussed. Probable formation mechanism for various morphologies of ZnAl2O4:Tb3+ nanophosphors was discussed. Structural and luminescence properties of the obtained samples were thoroughly investigated. Rietveld refinement of the prepared samples exhibit cubic structure with Fd3¯m space group. Thermoluminescence (TL) glow curves exhibit a well resolved glow peak at ∼197°C. TL intensity was found to increase linearly up to 1kGy and thereafter it shows sub-linear behavior with increase of dose which indicates that the present phosphor was quite useful for TL dosimetry. Kinetic parameters related with the glow peaks were estimated by different methods. Photoluminescence spectra shows the characteristic Tb3+ ions peaks at ∼488nm, 542nm, 584nm and 622nm corresponding to 5D4→7FJ (J = 3, 4, 5 and 6) transitions respectively. The chromaticity co-ordinates of all the phosphors were well located in green region. Therefore, the present phosphor was quite useful as green component of white light-emitting diodes.

Recent Progress in Quantum Dot Based White Light-Emitting Devices

Colloidal semiconductor quantum dots (QDs) have been widely employed as components of white light-emitting diodes (WLEDs) due to their excellent optical properties (highly saturated emission color, high luminescence quantum yield) as well as thermal and chemical stability. Much effort has been devoted to realize efficient QD-based WLEDs, including the synthesis of superior luminescent nanomaterials with excellent stabilities, and the design of advanced devices structures. In this paper, after introducing photometric parameters of the contemporary QD-based WLEDs, we highlight the recent progress in these devices grouped according to three main mechanisms for white light generation: optical excitation, direct charge carrier injection, and Förster resonance energy transfer. The methods to generate white light, the design of QD emitters and QD-based devices, as well as their fabrication techniques are considered, and the key scientific and technological challenges in the QD-based WLEDs are highlighted. Novel light-emitting materials for WLEDs such as carbon-based nanoparticles are also considered.

Luminescence properties of novel red-emitting phosphor InNb1-xPxO4:Eu3+ for white light emitting-diodes

Abstract InNb1-xPxO4:Eu3+ red phosphors were synthesized by solid-state reaction and their luminescence properties were also studied through photoluminescence spectra. The excitation and emission spectra make it clear that the as-prepared phosphors can be effectively excited by near-ultraviolet (UV) 394 nm light and blue 466 nm light to emit strong red light located at 612 nm, due to the Eu3+ transition of 5D0 → 7F2. The luminescence intensity is dependent on phosphorus content, and it achieves the maximum at x = 0.4. Excessive phosphorus in the phosphors can result in reduction of luminescence intensity owing to concentration quenching.With the increasing content of phosphorus, the phosphors are prone to emit pure red light. This shows that the InNb1.6P0.4O4:0.04Eu3+ phosphor may be a potential candidate as a red component for white light emitting-diodes.