White Phosphor Research Articles

Machine learning identification of experimental conditions for the synthesis of single-phase white phosphors

<h2>Summary</h2> Single-phase white phosphors for solid-state lighting are commonly designed using different dopants responsible for emissions in different spectral regions. However, the phenomena of energy transfer and concentration quenching often prevent any clear prediction of the accurate experimental conditions to be selected, leading to a time-consuming trial-and-error discovery process. In this article, a high-throughput experimental approach equipped with machine learning (ML) enabling an efficient identification of the experimental conditions for designing a white phosphor is demonstrated. Li₂BaSiO₄:Eu,Ce was selected to illustrate this strategy. A total of 88 samples were prepared from the initial synthesis of eight compounds with different concentrations of dopants followed by a post-treatment under a gradient of temperature. The decision tree model identified the experimental conditions for designing a white emission. The analysis of the experimental conditions to obtain other colors of emission, which were also identified by ML, enabled rationalization of the different mechanisms of energy transfer between dopants.

Achievement of high-efficiency sunlight-like emission in Rb2CaP2O7: Ce3+, Eu2+ phosphors

High quantum efficiency and thermal stability have always been the goals to pursue and challenges for lighting application. In this work, sunlight-like white emission has been achieved in a new prepared single phased Rb2CaP2O7: 0.005Ce3+, 0.01Eu2+ phosphor, which exhibits high internal quantum efficiency (IQE = 74.36%), external (EQE = 56.77%) quantum efficiency and excellent thermal stability. Based on the broadband emission from 4f-5d transitions of Ce3+/Eu2+ ions and high energy transfer efficiency of Ce3+→Eu2+ (measured up to 60%), the extremely wide color-tunable emission from blue-violet to white and then to orange-yellow is realized in Rb2CaP2O7: 0.005Ce3+, xEu2+ phosphors. Moreover, a prototype WLED device is packaged by combing the prepared Ra2CaP2O7: 0.005Ce3+, 0.01Eu2+ white phosphors with an UV LED chip (λ = 310 nm), and the obtained WLED emits bright sunlight-like white light with color coordinates of (0.377, 0.324). The correlated color temperature (CCT) and the color rendering index (CRI) value of the WLED are 3208 K and 88.4, respectively. These results can provide effective guidance for the design of color-tunable single-phase white phosphors with high luminous efficacy and thermal stability.

Site occupation and energy transfer in full color emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+

White light-emitting diodes (WLEDs) fabricated by single-phase full color emitting phosphor are an emerging solution for health lighting. The crystallographic site occupation of activators in a proper host lattice is crucial for sophisticated design of such phosphor. Here, we report a high quality white light-emitting phosphor Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ with spectral distribution covering whole visible region. Blue light emission originates from Ce3+ ions occupying preferentially Ba2+ site by controlling synthesis conditions. Green and red lights are obtained from Eu2+ occupying Ba2+ (and Ca2+) site and Mn2+ occupying Ca2+ site, respectively. In this triple-doped phosphor, strong red emission with a low concentration of Mn2+ is realized by the efficient energy transfer from Ce3+ and Eu2+ to Mn2+. Furthermore, high quality white light is accomplished by properly tuning the relative doping amount of Ce3+(K+)/Eu2+/Mn2+ based on efficient simultaneous energy transfer. The results indicate that Ba2Ca(BO3)2:Ce3+(K+),Eu2+,Mn2+ is a promising white light-emitting phosphor in WLEDs application.

Efficient, Stable, and Tunable Cold/Warm White Light from Lead‐Free Halide Double Perovskites Cs2Zr1‐xTexCl6

AbstractSingle‐component materials with efficient, stable, and tunable cold/warm white‐light emission are ideal candidates for lighting applications, which can overcome the problems of different deterioration rates and reabsorption effect in conventional mixed‐phosphors strategy. Efficient white phosphors based on double halide perovskite have been reported via manipulating the parity transitions recently. However, the emission wavelength is nonadjustable. Herein, a lead‐free double perovskite Cs2Zr1−xTexCl6 that exhibits efficient and stable white‐light emission is reported. The introduction of Te4+ results in bright self‐trapped exciton (STE) emission, which endows Cs2ZrCl6 matrix with multiple luminescent centers. Efficient white luminescence with tunable color temperature and high photoluminescence quantum yield (PLQY) of 61.5% (under 254 nm, CCT = 4039 K) and 96.1% (under 365 nm, CCT = 3313 K) is achieved. Efficient energy transfer between multiple luminescent centers and appropriate doping concentrations are the key points to achieve such highly efficient and tunable white emission. The as‐synthesized Cs2Zr1−xTexCl6 composites exhibit a robust stability against heat, ultraviolet light, and environmental oxygen/moisture, which show little spectra variation with less than ≈20% efficiency loss after 980 h testing even under high temperature and UV light. These results indicate Cs2Zr1−xTexCl6 are promising single‐component white‐light‐emitting phosphors for next‐generation lighting and display technologies.

Synthesis and luminescent property of Sm3+ doped and (Sm3+, Zr4+) co-doped calcium stannate phosphors via co-precipitation and sintering

Sm 3+ doped calcium stannate (CaSnO 3 :Sm 3+ ) and (Sm 3+ , Zr 4+ )-co-doped calcium stannate (CaSnO 3 :Sm 3+ , Zr 4+ ) photoluminescent phosphors were synthesized via co-precipitation and subsequent sintering in oxidizing atmosphere at 1400 °C for 60 min with SnCl 4 ·5H 2 O, CaCl 2 ·2H 2 O, ZrO(NO 3 ) 2 · x H 2 O and Sm 2 O 3 as main raw materials. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, photoluminescent spectroscopy, luminescent decay curves, afterglow spectroscopy and thermo-luminescent glow curves. The results show that CaSnO 3 pure phase is synthesized in co-precipitation reaction at an optimum molar ratio of CaCl 2 ·2H 2 O:SnCl 4 ·5H 2 O of 1.4:1.0 and subsequent sintering at 1400 °C for 60 min. Calcium stannate as a host matrix can be doped with Sm 3+ ions or co-doped with Sm 3+ /Zr 4+ ions for the formation of white photoluminescent phosphors. CaSnO 3 :0.03Sm 3+ phosphor has an optimum photoluminescent intensity. Also, the fluorescent emission intensity of CaSnO 3 :0.03Sm 3+ ，0.04Zr 4+ phosphor under excitation of 365 nm wavelength can be enhanced due to Zr 4+ ions doping at an optimum doping amount y of 0.04. The CIE 1931 chromaticity coordinates change from (0.3600, 0.3535) for CaSnO 3 :0.03Sm 3+ phosphor to (0.3622, 0.3574) for CaSnO 3 :0.03Sm 3+ , 0.04Zr 4+ phosphor as the average crystalline size decreases from 71.5 to 68.3 nm and the unit cell volume increases from 0.2686 to 0.2775 nm 3 . In addition, the electron transition mechanism for the photoluminescent and long afterglow properties was also discussed. • The CaSnO 3 : x Sm 3+ , y Zr 4+ phosphors were prepared by co-precipitation and subsequent sintering in oxidizing atmosphere at 1400℃. • The incorporation of Zr 4+ into CaSnO 3 :0.03Sm 3+ phosphor increased the photoluminescent intensity and luminescent decay times.

Effects of NaB&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;:Mn&lt;sup&gt;2+&lt;/sup&gt; and Ba&lt;sub&gt;2&lt;/sub&gt;Li&lt;sub&gt;2&lt;/sub&gt;Si&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;:Sn&lt;sup&gt;3+&lt;/sup&gt;,Mn&lt;sup&gt;2+&lt;/sup&gt; phosphors and remote structure organizations on the white light-emitting diodes with quantum dots and phosphors

In order to increase the optical features of white light-emitting diodes (WLEDs), quantum dots (QDs) and phosphor materials have been proposed because of outstanding performance. The configuration of WLEDs with QDs layer and phosphor-silicone layer suggested placing these components separately to limit light loss, and enhance consistency at contact surface of QDs. In this research, the effects of QDs and phosphor on the performance of WLEDs are concluded through experiments. The emitted light and PL spectra were examined thoroughly, and infrared thermal imagers were applied to simulate the heat generation of an actual WLED device. The results show that with the configuration of 60 mA energy source, WLEDs which has the QDs-on-phosphor form attained luminous efficiency (LE) of 110 lm/W, with color rendering index (CRI) of Ra=92 and R9=80, whereas the WLEDs which has the phosphor-on-QDs form only has 68 lm/W in LE, Ra=57 and R9=24. Furthermore, WLEDs which has the QDs-on-phosphor form has less high temperature generated at the components’ conjunction in comparison to the counterpart, the peak generated heat in QDs-on-phosphor WLEDs is also lower and the heating capacity gap between 2 structures can go up to 12.3°C.

Machine Learning Guided Design of Single-Phase Hybrid Lead Halide White Phosphors.

Designing new single‐phase white phosphors for solid‐state lighting is a challenging trial–error process as it requires to navigate in a multidimensional space (composition of the host matrix/dopants, experimental conditions, etc.). Thus, no single‐phase white phosphor has ever been reported to exhibit both a high color rendering index (CRI ‐ degree to which objects appear natural under the white illumination) and a tunable correlated color temperature (CCT). In this article, a novel strategy consisting in iterating syntheses, characterizations, and machine learning (ML) models to design such white phosphors is demonstrated. With the guidance of ML models, a series of luminescent hybrid lead halides with ultra‐high color rendering (above 92) mimicking the light of the sunrise/sunset (CCT = 3200 K), morning/afternoon (CCT = 4200 K), midday (CCT = 5500 K), full sun (CCT = 6500K), as well as an overcast sky (CCT = 7000 K) are precisely designed.

A novel Eu-dependent G-La2Si2O7 single matrix phosphor for white light-emitting diodes

A novel G-La2Si2O7: Eu phosphor has been synthesized through SiC-reduction assisted with sol-gel method. Divalent Eu2+ and trivalent Eu3+ luminescent centers coexist in G-La2Si2O7: Eu lattice. Furthermore, two types of Eu2+ luminescent centers exist in G-La2Si2O7: Eu lattice, labeled as Eu1 and Eu2, arising from two La3+ crystallographic sites in G-La2Si2O7 host. Eu1 represents blue band emission while Eu2 shows green-yellow emission. Eu2+ selective occupation introduces Eu2+ large-scale blue-yellow regulation. Eu3+ shows typical red sharp line emission mainly located at 593 nm and 611 nm assigned to 5D0→7FJ (J = 1, 2) transitions. The luminescence process in G-La2Si2O7: Eu is discussed in details. Energy transfer processes from Eu3+ to Eu1 and Eu2, Eu1 to Eu2 occurs in G-La2Si2O7: Eu lattice. The influence of Eu dopant concentration is explored. As Eu increases, the dominant emission changes from Eu2+ to Eu3+. The coexistence of Eu1, Eu2 and Eu3+ brings G-La2Si2O7: Eu blue to red regulation. Fixing Eu doping at 0.5%, G-La1.99Si2O7: 0.01Eu sample shows a single-phased white light-emitting phosphor. At ultraviolet light 254 nm excitation, the emission spectrum approximate to full spectrum with a high rendering index of Ra = 91 is obtained using La1.99Si2O7: 0.01Eu sample at 254 nm excitation. Besides, G-La2Si2O7: Eu represents a good fluorescent thermal stability with luminous intensity keeping 80% (160 °C) of that at room temperature (30 °C), indicating G-La2Si2O7: Eu is a great potential single-matrix candidate in nUV-chip WLEDs.

Li+ Ion Induced Full Visible Emission in Single Eu2+‐Doped White Emitting Phosphor: Eu2+ Site Preference Analysis, Luminescence Properties, and WLED Applications

AbstractA series of Eu2+ single doped Ca9Na1–xLixSc0.667(PO4)7 phosphors with full‐spectrum emission have been synthesized. Under the 385 nm excitation, the Eu2+ single doped Ca9NaSc0.667(PO4)7 without Li+ doping displays a broad cold white light emission with the peaks at about 480 and 610 nm. With the introduction of Li+ ions, the Eu2+ ions selectively occupy the Ca1, Ca2/Ca3, and Na sites. The variation of local environment of Eu2+ ions caused by Li+ ions enhances the luminous intensity, solves the problem of the lack of a red light component, and realizes the emission color tuning from cold white via warm white to orange. A special charge compensation method caused by Li+ migration avoids the generation of defects and is beneficial to the improvement of luminescence properties. Eventually, a warm white light‐emitting diode device is prepared by combining the white emitting Ca9Na0.8Li0.2Sc0.667(PO4)7:2%Eu2+ phosphors with 385 nm LED chip, which exhibits a high color‐rendering of 92.9, low correlated color temperatures of 4529 K, and excellent color stability under working temperature. The as‐reported warm white emitting Eu2+‐doped phosphors have potential applications in full‐spectrum solid‐state lighting. The site engineering strategy provides an extensive guide for optimizing and designing novel single‐composition white‐emitting phosphor materials.

Tailoring of White Luminescence in a NaLi3 SiO4 :Eu2+ Phosphor Containing Broad-Band Defect-Induced Charge-Transfer Emission.

Single-component materials with white-light emission are ideal for lighting applications. However, it is very challenging to achieve white luminescence in single-dopant activated solid phosphors. Herein, white NaLi3 Si1- x O4 :Eu2+ materials are designed via defect engineering and synthesized by reducing the Si content (0.15 ≤ x≤ 0.25). Stochiometric NaLi3 SiO4 :Eu2+ exhibits a narrow-band blue emission at 469nm, ascribed to the 5d → 4f transition of Eu2+ at highly symmetric cuboid Na sites, while samples with Si content reduced by 15-25% display white emission with two peaks at 472nm and 585nm. The newly appeared broadband yellow peak arises from charge-transfer transitions involving Eu2+ and nearby defects, as verified by an unusual bandwidth, a large Stokes shift, and a long decay time. A single-component white light-emitting diode device is fabricated by employing a white phosphor to demonstrate a color-rendering index of 82.9. This result provides a new design strategy for single-component white-light materials with broad-band defect-induced charge-transfer emission.

Bi3+ occupancy rearrangement in K2-xAxMgGeO4 phosphor to achieve ultra-broad-band white emission based on alkali metal substitution engineering

Ultra-broad-band white emitting phosphors have a wide application prospect in the new generation of illumination systems. Due to the sensitivity of Bi3+ to the surrounding environment, it exhibits different luminescence properties in different crystallographic sites, which makes it easy to achieve white emission. Cationic substitution engineering is the most effective strategy for controlling the environment around Bi-site and realizing the spectrum tuning. Herein, we conducted substitution engineering in K2MgGeO4:Bi3+ (KMGO:Bi3+) that uses alkali metal A+ (A = Li, Na, Rb) to substitute K+. The difference in emission spectrum excited at various wavelengths is related to extra luminescent centers generation and Bi3+ occupancy rearrangement in KMGO:Bi3+ under the influence of Li+ and Na+, which also leads to the expansion of full widths at half-maximum (FWHM) to 204 nm forming a bright white emission. Besides, the modulation of Rb+ increases the activation energy and enhances its thermal stability to 88.66%. The high Ra values (93.4) of the fabricated WLED indicate that K1.456Na0.54MgGeO4:0.004Bi3+ could be used as a single-component white phosphor in solid-state lighting. Our research shows that alkali metal substitution engineering is of great significance to controlling the luminescence emission and improving the thermal stability of luminescent materials.

Tb3+ and Sm3+ co-doped CaWO4 white light phosphors for plant lamp synthesized via solid state method: Phase, photoluminescence and electronic structure

A series of CaWO4: Tb3+, Sm3+ phosphors was successfully synthesized via the facile high temperature solid state reaction method. The phase purity and effect of different valence doping on cell parameters were evaluated by XRD analysis. When the trivalent RE3+ replaces the divalent Ca2+, the local electric field is generated, which has obvious influence on the lattice. The excitation spectra show that Tb3+ and Sm3+ can be excited simultaneously in the co-doped phosphors. The emission spectra of phosphors show that white phosphors can be obtained by adjusting the doping ratio and there is an energy transfer from Tb3+ to Sm3+ in the co-doped phosphors. The electronic structures of phosphors were studied by the first principle calculations. The quantum efficiency, thermal dependence and comparison with the absorption spectra of the pigments show that CaWO4: 0.01 Tb3+, 0.01Sm3+ phosphor has potential applications in the fields of white LEDs and plant lamps.

Impact of Carbon Co-Doping on the Optical and Scintillation Properties of a YAG:Ce Scintillator

This paper addresses the carbon co-doping of Ce-doped garnets, an efficient scintillation material and white light phosphor. The composition and the optical and scintillation properties of carbon-c...

Full-visible-spectrum emission with high color rendering index and low correlated color temperature enabled by a single-phased phosphor of α-Sr2V1.98P0.02O7: 0.5% Eu3+

A single-phased warm white phosphor of α-Sr2V1.98P0.02O7: 0.5 % Eu3+ with low correlated color temperature (CCT) and high color rendering index (CRI) was synthesized by high temperature solid phase method. By changing the ratio of PO43−/VO43−, the emission intensity of VO43− and the energy transfer efficiency of VO43−→Eu3+ can be effectively tuned, and the full-spectrum warm white light emission of phosphors in the range of 400−700 nm can be realized. Moreover, the temperature-dependent emission spectra and thermal quenching properties were investigated in detail. On this basis, the WLED prototype devices were packaged with the synthesized phosphors α-Sr2V1.98P0.02O7: 0.5 % Eu3+ and 365 nm near-ultraviolet (NUV) chips and high-quality warm white light emission with CCT = 3188 K and CRI Ra = 93.5 were achieved. These findings provide new insights into exploring single-phased white phosphors for NUV-pumped warm w-LEDs with high CRI property and low CCT value.

Preparation, structure, and luminescent properties of Dy3+-doped borate Ca3La3(BO3)5: Dy3+ for potential application in UV-LEDs

A single-phase white light-emitting phosphor Ca3La3(BO3)5: Dy3+ (CLBD) was prepared via a solid-state reaction. The introduction of Dy3+ in Ca3La3(BO3)5 with a preferred location on La3+ was confirmed by x-ray diffraction and Rietveld structural refinement studies. The micrograph observed by scanning electron microscopy reveals an inhomogeneous and uneven dense morphology in the micrometer range. The optical spectra analysis shows that the CLBD can be efficiently excited by ultraviolet (UV) light and emitted intense white light due to the combination of blue 4F9/2 → 6H15/2 (∼485 nm) and yellow 4F9/2 → 6H13/2 (∼575 nm) emissions originated from 4f–4f transitions of Dy3+. The critical concentration is determined to be ∼12 mol. %, and the dipole–dipole (d–d) interaction is responsible for the quenching mechanism. In additional, the CLBD has high thermal stability. By incorporating the CLBD with a phosphor-capping method on AlInGaN LED, we obtain the white light that meets the spectral and efficiency requirements for high-efficacy solid-state white lighting lamps. The Commission Internationale de I'Eclairage chromaticity coordinates and color correlated temperature with optimal electroluminescence intensity are calculated to be ∼(0.338, 0.342) and 5950 K, respectively. All results indicate the CLBD could serve as a promising candidate for white UV-LEDs.

An insight into the structure, luminescent characteristics and Judd-Ofelt analysis of (1-x) ZnS-(x) Dy2O3 phosphors

We report a white light emitting of (1- x) ZnS - (x) Dy2O3 with x = 0, 0.1, 0.2 and 0.3 phosphor synthesized via conventional solid state reaction method. The crystal structure, modes of vibrations, morphology, NIR-UV absorption and luminescence characteristics were discussed. The X-ray diffraction study confirmed the single phase of hexagonal ZnS and cubic Dy2O3 structure. The intensity parameters Ω2, Ω4 and Ω6 were estimated for x = 0.1, from the optical absorption spectra using Judd-Ofelt theory, since the optimal doping concentration is about 10mol%. The optical band gap energy of the samples varied from 3.41 to 3.49 eV. The photoluminescence spectra has an intense strong emission at 582 nm corresponding to 4F9/2 → 6H13/2 transition due to a forced electric dipole (ED) allowed transition with selection rule ΔL = 2 and ΔJ = 2. The transition radiative parameter (AR) and the stimulated emission cross section, σe values suggested that (1- x) ZnS - (x) Dy2O3 with x = 0.1 phosphor material is suitable for white LED applications. The nephelauxetic ratio and the bonding parameter of concentration x = 0.1 were calculated. The negative value of bonding parameter indicated that Dy3+ ion and ZnS material is bonded ionically. The CIE chromaticity coordinates, Yellow to Blue intensity ratio, Color Purity and Correlated Color Temperature were also estimated. The CIE coordinates of the samples lie in the white light region and this type of white light luminescence phosphors could be promising phosphors for w-LEDs and optoelectronic devices applications.

Synthesis and luminescence studies of mixed phase LiCa3MgV3-XWXO12 phosphors for enhanced quantum yield

Highly efficient bluish white phosphors based on self-activated luminescent materials are essential part for fabricating white lighting diodes. Transition metals have a wide application in catalyst and photoluminescence aspects especially for molybdenum and tungsten, which multi-metal oxides also promote diverse properties. In this work, a serial of novel structural mixed phases phosphors LiCa3MgV3-XWXO12 (short as LCMV-W-X) combined with vanadate and tungsten oxides are constructed by sol-gel method for the first time. The photoluminescence quantum yield (PLQY) of LCMV-W-0.20 is significantly enhanced to 64.37% related to the decreasing of luminous centers distance and oxygen vacancies. The deeper reason for the significant enhancement in PLQY can be ascribed to the fact that the introduction of tungsten phase leads to the lattice deformation of [VO4] and [WO4] tetrahedron of LCMV-W-X, which increases the interaction of luminescence centers. At the same time, the luminescence characteristics of tungsten oxide make LCMV-W-X fluorescence performance change with the change of tungsten content. Hence, this work enlightens a new method to construct highly efficient phosphors.

Realization of high-quality white light emission in single-phased α-Sr2P2O7: Dy3+, Tm3+ phosphor

A single-phased white phosphor of α-Sr2P2O7: Dy3+, Tm3+ with low correlated color temperature (CCT) was synthesized by high temperature solid phase method. Our experimental results show that by co-doping Tm3+ and Dy3+ ions in the α-Sr2P2O7 matrix, the blue characteristic emission peak of Tm3+ ions can be used to effectively enhance the blue emission of the phosphor, and finally achieve high-quality white light emission. Moreover, since the emission spectrum of Tm3+ overlaps with the excitation spectrum of Dy3+ in the wavelength band from 445 to 465 nm, Tm3+ can transfer energy to Dy3+ ions, so the emission spectrum of Dy3+ can be further regulated and the emission intensity can be improved. Consequently, by optimizing the co-doping ratio of Tm3+ and Dy3+ ions, we achieved the optimal white light emission in α-Sr2P2O7: 0.01Tm3+, 0.01Dy3+ samples. Under the excitation of 351 nm ultraviolet light, the color coordinates of α-Sr2P2O7: 0.01Tm3+, 0.01Dy3+ emitting white light are (0.3292, 0.3521), and the CCT value is 5500 K, which are almost consistent with the color coordinates of standard white light and the color temperature of daylight. Therefore, α-Sr2P2O7: Dy3+, Tm3+ is a single-phased white phosphor material with great application potential for UV excitation.

Daylight-White-Emitting and Abnormal Thermal Antiquenching Phosphors Based on a Layered Host SrIn2(P2O7)2.

Single-phase white-emission phosphors possess a judicious usage potential in phosphor-converted white-light-emitting diodes (WLEDs). Recently, numerous efforts have been made toward the development of new patterns of white-emitting phosphors that achieve excellent quantum yield, superior thermal stability, and applaudable cost effectiveness of WLEDs. Finding suitable single-component white phosphor hosts to provide an ideal local environment for activators remains urgent. Inspired by the original discovery of the promising host MgIn2(P2O7)2 (MIP) and its structural dependence on alkali-metal cations, we synthesized a brand-new phosphor host, SrIn2(P2O7)2 (SIP), via the traditional solid-state reaction. Its crystal structure was determined using an ab initio analysis and the Rietveld method. It belongs to a monoclinic unit cell with the space group C2/c. Besides, SIP exhibits a special layered three-dimensional framework in which the monolayer [SrO10]∞ was surrounded by a bilayer [In2P4O14]∞ made of the InO6 octahedra and P2O7 groups. A series of pure SIP:Tm3+,Dy3+ phosphors with tunable blue-white-yellow emission were prepared by adjusting the dopant concentration and utilizing the Tm3+-Dy3+ energy transfer. The daylight-white-emitting phosphor SIP:0.01Tm3+,0.04Dy3+ (the correlated color temperature is 4448 K) exhibits an abnormal thermal antiquenching property, and the emission intensity of 423 K reaches 103.7% of the initial value at 300 K. On the basis of the temperature-dependent lattice evolution and microenvironment analysis, the reduction of β and lattice distortion can lead to lower asymmetry of the activators and benefit the compensation of trapped-electron thermal activation. In this work, an integration study was carried out on the crystal structure of the new matrix, the occupation of the luminescent center, the interaction of different activators in the host, and the distortion degree of the local structure for the activators, which is of great practical sense for producing a novel single-matrix white phosphor possessing superior thermal endurance for UV-light-stimulated WLEDs.

Development of White Persistent Phosphors by Manipulating Lanthanide Ions in Gadolinium Gallium Garnets

Lanthanide ions act as excellent luminescence centers and good charge carrier traps. By selecting proper lanthanide ions, persistent phosphors with the desired luminescent color can be developed. In addition, an appropriate host material can give not only better persistent luminescence performance but also an additional function. Herein, bright white persistent phosphors of Pr3+–Tb3+–Eu3+ tridoped paramagnetic Gd3Ga5O12 (GGG) are successfully developed. The GGG phosphors singly doped with Pr3+, Tb3+, and Eu3+ show reddish‐white (3PJ–3HJ), blue (5DJ–7FJ), and red (5D0–7FJ) photoluminescence, respectively, by UV excitation. On the other hand, the GGG samples codoped with Pr3+–Eu3+ and with Tb3+–Eu3+ show only Pr3+ reddish‐white persistent luminescence and Tb3+ blue persistent luminescence, respectively. Based on the thermoluminescence glow curves, it is found that the Eu3+ ion acts only as an electron trap in the persistent luminescence mechanism and the trapped electrons are released at around 325 K. The cool‐white persistent luminescence is achieved by combining Pr3+ and Tb3+ persistent luminescence centers in the GGG:Pr3+–Tb3+–Eu3+ phosphors. It is demonstrated that the white persistent phosphor powder in water can be dragged around by a permanent magnet due to the paramagnetic property of GGG.