Orange Phosphor Research Articles

Photoluminescence evolution and high thermal stability of orange red-emitting Ba3-xSrxZnNb2O9: Eu3+ phosphors

A series of Ba3-xSrxZnNb2O9: 0.3Eu3+ (x ​= ​0, 0.5, 1, 1.5, 2, 2.5, 3) orange-red phosphors were synthesized by high-temperature solid-phase reaction. In order to identify and describe the crystal structure, luminescence characteristics and thermal stability of the samples, XRD and luminescence spectroscopy tests were carried out. The refined XRD results showed that Eu3+ ions have been successfully doped into Ba3-xSrxZnNb2O9 matrix and occupied partly the sites of Eu3+ ions. Under UV excitation of 396 ​nm, the emission spectra of the samples are composed of two emission peaks near 593 ​nm and 612 ​nm with a slight blue shift, attributed to the increase in splitting degree of 5d electron orbit of Eu3+ ions. At 523 ​K, the thermal stabilities of phosphors with Sr2+ ion doping concentration of 2 and 3 are 82.14% and 84.33%, respectively. With the increase of Sr2+ ion concentration, the activation energy increases from 0.198 ​eV to 0.230 ​eV, better than the other reports. In addition, the CCT (below 2000 K) and color purity (above 95%) of the samples are calculated. A WLED device can be obtained by combining the as-prepared orange red-emitting phosphor with commercial blue (BaMgAl10O17: Eu2+) and green ((Sr, Ba)2SiO4: Eu2+) phosphors. All these indicated that the self-made phosphors are promising to be used in UV/n-UV pumped WLEDs requiring low CCT.

Near-ultraviolet excited broadband orange-yellow emitting Sr8MgIn(PO4)7:Eu2+ phosphors for WLEDs with high color rendering index

As is well known, whitlockite β-Ca3(PO4)2-type phosphors are easily evolved to a new crystal structure by cation substitution, and have various crystallographic sites for doping activators to achieve luminescence. Herein, a novel broadband emitting Sr8MgIn(PO4)7: Eu2+ (SMIP) phosphor was prepared by high temperature solid state reaction. Its crystal structure was analyzed and refined via the Rietveld refinement method. The SMIP crystal presents a monoclinic system with space group C2/m. Their diffuse reflection and excitation spectra both show an intense absorption to the wavelength of 250–500 nm. And the photoluminescence spectrum exhibits a strong broadband emitting from 450 to 800 nm. Moreover, the luminescence decay curves reveal three kinds of Sr/Mg2+ crystallographic sites for Eu2+ occupying in SMIP host. For SMIP: xEu2+ samples, the optimized doping concentration was determined to be 0.03, and the energy transfer among the nearest-neighbor was dominating. Further, the activation energy was estimated to be 0.1145 eV. Finally, white light-emitting diodes (WLED) lamps were fabricated by coating the mixtures of SMIP: 0.03Eu2+ phosphors and BaMgAl10O17: Eu2+ phosphors on the surface of 400 nm near-ultraviolet chip. The optimized WLED lamp exhibits a correlated color temperature of 3034 K and a good color rendering index of 91.7. These results demonstrate the commercialized prospect of SMIP: Eu2+ materials as a broadband orange phosphor for application of solid state lighting.

In-air self-reduction synthesis and luminescence properties from Mg21 Ca4 Na4 (PO4 )18 :Eu2+ -Eu3+ excited using ultraviolet light.

A series of Mg21 Ca4 Na4 (PO4 )18 :Eu2+ -Eu3+ phosphors was successfully synthesized using a high-temperature solid-state method in an air atmosphere. The phase structures and luminescence properties of the samples were studied in detail. The phosphors exhibited strong visible light emission under different wavelengths of ultraviolet light excitation. By harmonizing the doping concentration of Eu3+ to adjust the relative luminescence intensity of Eu2+ and Eu3+ , a colourful emission of phosphors could be achieved. In addition, the colour coordinates of the International Commission on lighting indicated that Mg21 Ca4 Na4 (PO)18 :Eu2+ -Eu3+ could be considered as a potential blue, orange and red phosphor for white light-emitting diode applications.

Room temperature synthesis, Judd Ofelt analysis and photoluminescence properties of down-conversion K0·3Bi0·7F2.4:Eu3+ orange red phosphors

This work aims at studying optical properties of Eu3+ dopant in K0·3Bi0·7F2.4 host and seeking their applications. A series of orange red emitting K0·3Bi0·7F2.4:Eu3+ phosphors were synthesized via a chemical precipitation reaction method at room temperature, which is convenient, economical and less time consuming. XRD and Rietveld refinement results confirm the pure phase of as-prepared materials. The optimal doping concentrations are determined to be 40%mmol, and both of the corresponding concentration quenching mechanism have been validated to be dipole−dipole interactions. Additionally, the Judd-Ofelt theory was selected to study the local structure environment of the Eu3+ ions in the K0·3Bi0·7F2.4 host lattices and the tendency of J-O parameters (Ω2>Ω4) confirm the asymmetric environment around Eu3+ ions. The thermogravimetric analysis and activation energy results of K0·3Bi0·7F2.4:Eu3+ materials with high thermal stability exhibit promising performances for temperature sensor applications. Moreover, the temperature-dependent of samples are investigated in a large temperature range of 303–573 K to explore thermal quenching performance. Significantly, luminescent temperature sensing has been accomplished by specifically utilizing thermal quenching performance and high temperature sensitivity around 1.54 × 104 K−1 is achieved, which indicates that K0·3Bi0·7F2.4:Eu3+ fluorescent nanoparticles can be exploited for promising luminescent thermometer. Another important results are the K0·3Bi0·7F2.4:40%Eu3+ nanoparticles exhibiting orange red emission with the CIE coordinates (0.6226, 0.3747) and the luminescence photographs of K0·3Bi0·7F2.4:40%Eu3+ samples under UV lamp (365 nm) irradiation revealing obvious orange red. Besides, the color purity of orange red K0·3Bi0·7F2.4:40%Eu3+ phosphor is demonstrated to be about 98.4%, which indicate that the as-prepared K0·3Bi0·7F2.4:Eu3+ phosphors may be a candidate component applied in UV w-LEDs.

A novel Ba3Bi2(PO4)4: Sm3+ orange red-emitting phosphor: Influences of sintering temperature and Sm3+ concentration on microstructures and photoluminescence properties

A series of novel Ba3Bi2(PO4)4: Sm3+ phosphors have been prepared by the conventional solid reaction process at different sintering temperature and Sm3+ ion concentration. X-ray powder diffraction patterns, scanning electron microscopy, photoluminescence spectra, decay curve, as well as the temperature-dependent properties and CIE chromaticity coordinate were used to characterize the performance of the as-prepared phosphors. The results show that sintering temperature can significantly affect the phase purity, morphology and photoluminescence performance of the obtained phosphors. The X-ray powder diffraction patterns confirmed that a pure Ba3Bi2(PO4)4 phase could be formed at 980 °C for 5 h in our case. The scanning electron microscopy shows the particle size of the obtained phosphors increases when sintering temperature increases from 900 to 980 °C. And the synthesized Ba3Bi2(PO4)4: Sm3+ is an orange red-emitting phosphor, which can emit 600 nm orange red light under the excitation of 403 nm. Moreover, as the Sm3+ ion concentration increases, the emission intensity reaches the maximum at x = 0.07. The luminescence lifetime of Ba3Bi2(PO4)4: 0.07Sm3+ phosphor was determined to be 1.978 ms. Meantime, the Sm3+ doped Ba3Bi2(PO4)4 phosphor has a good thermal stability with the thermal activation energy is 0.21 eV. The CIE chromaticity coordinate was calculated located in the orange reddish region, which indicated that the Ba3Bi2(PO4)4: Sm3+ phosphors have a potential application in white light emitting diodes.

Enhanced quantum efficiency and thermal stability in tunable yellow-emitting Sr Ca1-AlSiN3:Ce3+ phosphor

Abstract Ce3+ doped CaAlSiN3 is a promising broadband orange phosphor that can be applied in white light-emitting diodes (wLEDs) solid state lighting for general illumination. However, its emission color and quantum efficiency are not good enough to achieve high color rendering properties and luminous efficacy of wLEDs. In this work, we proposed to realize the spectral tuning and property enhancement of CaAlSiN3:Ce3+ by bandgap engineering via the cationic substitution of Ca by Sr. The relationship between photoluminescence and local coordination structure as well as electronic structure were revealed. The substitution led to a blue-shift in emission maximum by 13 nm (from 595 to 582 nm) and a highest external quantum efficiency of 55% (enhanced by 10%). This broadband yellow phosphor enabled to produce wLEDs with a color rendering index of 83.3, luminous efficacy of 114.6 l m/W and a color temperature of 4604 K.

A Multifunctional Bipolar Luminogen with Delayed Fluorescence for High‐Performance Monochromatic and Color‐Stable Warm‐White OLEDs

AbstractIncreasing exciton utilization and reducing exciton annihilation are crucial to achieve high performance of organic light‐emitting diodes (OLEDs), which greatly depend on molecular engineering of emitters and hosts. A novel luminogen (SBF‐BP‐DMAC) is synthesized and characterized. Its crystal and electronic structures, thermal stability, electrochemical behavior, carrier transport, photoluminescence, and electroluminescence are investigated. SBF‐BP‐DMAC exhibits enhanced photoluminescence and promotes delayed fluorescence in solid state and bipolar carrier transport ability, and thus holds multifunctionality of emitter and host for OLEDs. Using SBF‐BP‐DMAC as an emitter, the nondoped OLEDs exhibit maximum electroluminescence (EL) efficiencies of 67.2 cd A−1, 65.9 lm W−1, and 20.1%, and the doped OLEDs provide maximum EL efficiencies of 79.1 cd A−1, 70.7 lm W−1, and 24.5%. A representative orange phosphor, Ir(tptpy)2acac, is doped into SBF‐BP‐DMAC for OLED fabrication, giving rise to superior EL efficiencies of 88.0 cd A−1, 108.0 lm W−1, and 26.8% for orange phosphorescent OLEDs, and forward‐viewing EL efficiencies of 69.3 cd A−1, 45.8 lm W−1, and 21.0% for two‐color hybrid warm‐white OLEDs. All of these OLEDs can retain high EL efficiencies at high luminance, with very small efficiency roll‐offs. The outstanding EL performance demonstrates the great potentials of SBF‐BP‐DMAC in practical display and lighting devices.

Electronic structure and luminescent properties of Sr3Al2O6:Sm3+ orange phosphor prepared by hydrothermal method

A series of Sm3+ ions doped Sr3Al2O6 phosphors was successfully synthesized via hydrothermal method. The crystal structure, morphology and luminescent properties of samples were analyzed by X-ray diffraction, scanning electron microscopy and photoluminescence spectra. All the samples took on cubic structure with Pa-3 space group. The Sr3Al2O6:Sm3+ phosphors could be excited by 405 nm and emit orange-red light peaked at 565, 609 and 660 nm. The effect of hydrothermal reaction time on the morphology and luminescent properties of phosphor was investigated. The influence of molar fraction of Sm3+ ions on the emission intensity of samples was studied and it has been found that the optimal dosage is 0.01. The calculated results by the first principle indicated that the Sm3+ ions will easily occupy the symmetric center site (Sr1). The results indicated that the luminescent intensity of Sr3Al2O6:Sm3+ phosphors could be modulated by reaction conditions of hydrothermal method.

Luminescence properties of Ca2Sn2Al2O9: Mn as a long afterglow and field-emission displays material with high yellow color purity

In this work, a series of rare earth free orange phosphors Ca2Sn2Al2O9: Mn (CSA: Mn) are synthesized successfully by two-steps high temperature solid-state reaction. Their crystal structure and luminescence properties are studied detail. CSA is a typical orthorhombic crystal system and belonging to P b c n (60) space group. There is only one kind Ca2+ site with seven coordinations in the structure for Mn2+ occupying. This phosphor possesses self-emitting and self-reduction due to the defects carrying negative charge which can provide electrons for Sn4+ and Mn4+. When Sn4+ and Mn4+ get electrons, they will generate their characteristic low valence electron transfer (Sn2+ and Mn2+) and emit relative radiation transition. The host emission yielding from Sn2+ and the broad orange emission from Mn2+ has an apparent energy transfer because of their overlap of the luminescence spectra. Furthermore, CSA: Mn2+ possesses orange PL emission with long afterglow about 7 h after 10 min UV excitation due to the defects’ trap energy level. And, Mn2+’s temperature dependent photoluminescence intensity appeared anomalous phenomena that the intensity increases firstly and then decreases, which is due to the traps energy level’s contribution of electron’s transition. Besides, CSA: Mn2+ can emit bright orange light under cathode ray and it has very stable CL properties after suffering long time electron beam bombarding. CSA: Mn2+ is a kind potential application value material in long afterglow and FED.

Highly Efficient Green‐to‐Yellowish‐Orange Emitting Eu2+‐Doped Pyrophosphate Phosphors with Superior Thermal Quenching Resistance for w‐LEDs

AbstractHighly efficient green/yellowish‐orange phosphors with low thermal quenching behavior are urgently required to improve the luminescence efficiency, color stability, and color rendering of phosphor‐converted white light emitting diodes (w‐LEDs). Herein, a novel green Cs2BaP2O7:0.01Eu2+ phosphor with high luminescence efficiency (82.7%) and thermal quenching behavior (92.5% at 423 K) is reported. Besides, a further luminescence improvement in the quantum yield (98.9%) and thermal quenching resistance (120% at 448 K) is successfully achieved in green/yellowish‐orange color‐tunable Cs2MP2O7:0.01Eu2+ (M = Ba, Sr, and Ca) phosphors. Surprisingly, these green/yellowish‐orange Cs2MP2O7:0.01Eu2+ (M = Ba, Sr, and Ca) phosphors even have a prior advantage over the commercial green β‐SiAlON:Eu2+ and yellow YAG:Ce3+ phosphors. The corresponding spectral adjustment and thermal stability mechanisms are revealed, related to the optimization of local lattice symmetry. The prototype w‐LEDs exhibit warm white light with CIE color coordinate at (0.337, 0.322). The color rendering index, corrected color temperature, and luminescence efficiency can reach 92.6, 4044 K, and 152.56 lm W−1, respectively. In general, the as‐reported green/yellowish‐orange Eu2+‐doped pyrophosphate phosphors are promising candidates in the future high‐quality w‐LEDs applications. The proposal of local lattice symmetry modulation can provide a new approach to exploit novel phosphors with excellent thermal quenching resistance.

Luminescent properties of CaSc2O4:Ce3+ green phosphor for white LED and its optical simulation

Green-emissive Ce3+-doped CaSc2O4 phosphors were synthesized by solid-state method. The water washing process of the as-prepared samples was several times conducted because of severe hydration of unreacted CaO and CaF2 flux residual. The washed CaSc2O4:Ce3+ phosphors showed a single phase with a crystallite size of 1–3 μm, and its photoluminescence intensity was 10% improved compared with the as-prepared. It shows the broad 450 nm excitation peak and the green emission peak at 520 nm with a half width of 105 nm. Its temperature dependence showed the similar thermal stability with a commercial silicate phosphor. The optical simulation and the real fabrication of white LEDs with a combination of our green phosphor and one of possible orange-red phosphors demonstrated that the white LED with Sr3SiO5:Eu2+ orange phosphor gives the best luminous efficacy and the appropriate color rendering index of 70 under the daylight color temperature of 6400 K.

Photoluminescence properties of near ultraviolet excited Ca8La2(PO4)6O2:Sm3+ red orange phosphor

Novel Ca8La2(PO4)6O2:Sm3+ phosphors are successfully synthesized in air by the high temperature solid state reaction method. The X-ray diffraction patterns, morphology, energy spectrum diagram, elemental mapping, luminescence properties, concentration-dependent emission spectra, thermal stability, and decay curves are investigated. The excitation spectrum of Ca8La2(PO4)6O2:8%Sm3+ phosphor monitored at 604 nm extends the region from 220 nm to 520 nm with many excitation spectral bands because of the O2−–Sm3+ charge transfer band and the f–f transitions of Sm3+ ion. Ca8La2(PO4)6O2:Sm3+ phosphor with excitation at 402 nm emits red orange light in the range of 550–770 nm with many emission spectral bands derived from the 4G5/2 → 6H5/2 (550–570 nm), 4G5/2 → 6H7/2 (570–630 nm), 4G5/2 → 6H9/2 (630–690 nm), and 4G5/2 → 6H11/2 (690–760 nm) transitions of Sm3+ ion, and the optimal Sm3+ concentration is ~ 8 mol%. The lifetime of Ca8La2(PO4)6O2:Sm3+ phosphor decreases from 1.39 to 1.11 ms with increasing Sm3+ concentration from 2 to 12 mol%. Ca8La2(PO4)6O2:Sm3+ phosphor has the good thermal stability and emission color stability. The luminous mechanism, concentration quenching, and thermal quenching are explained, respectively. The experimental results indicate that Ca8La2(PO4)6O2:Sm3+ phosphor as red orange component has a potential application in white LED based on near ultraviolet LED chip.

The structure and photoluminescence properties of a novel orange emission phosphor Ba3Sc1.9Al0.1B4O12: Eu2+ excited by NUV light

A novel borate mineral of Ba3Sc1.9Al0.1B4O12 was synthesized successfully by traditional high temperature solid-state reaction. Its structure is determined by High-resolution transmission electron microscopy, Energy Dispersive X-Ray Spectroscopy and X-ray powder diffraction Rietveld refinement. The crystal structure of Ba3Sc1.9Al0.1B4O12 was found to be trigonal crystal system and the space group is attributed to P-3m1 (164). Moreover, a series of Eu2+ doped Ba3Sc1.9Al0.1B4O12 phosphors are investigated. The electron structure, band structure and photoluminescence properties of Ba3Sc1.9Al0.1B4O12: Eu2+ are investigated in detail by density functional theory calculations, diffuse reflection spectra, emission-excitation spectra, decay curves and temperature dependence spectra. It can emit orange light peaking at ∼592 nm upon 400 nm NUV excitation with quantum efficiency 40.1%. According to structure and photoluminescence (PL) properties analysis, Eu2+ can occupy two kinds of Ba2+ site. The concentration quenching mechanism of Eu2+ could be a d-d interaction luminescence center. It has not good temperature stability properties because of too much temperature-dependent electron–phonon interaction at high temperature. The fabricated white-LEDs using a 370 nm GaN NUV chip combined with orange/blue phosphors under different weight ratio driven by 30 mA current can get series warm-white light, which the correlated color temperature is smaller than ‘YAG + Blue chips’ It demonstrates that Ba3Sc1.9Al0.1B4O12: Eu2+ is a potential orange phosphor matching NUV LED chips to get warm white light.

Enhancement of radiative transitions in Sm3+ activated CaTiO3 nanophosphor by modulating co-activator concentration

In present era, rare earth doped nanophosphors are the key architecture in the development of white light-emitting diodes (WLEDs) and their performance has become a major topic of interest among the researchers. Still, the deficiency of orange phosphor has become a barrier for the commercialization of the WLED. In this work, single phase intense orange light emitting Na+ co-activated CaTiO3 (CTO):Sm3+ nanophosphor is synthesized via modified sol–gel method with an average particle size of 60 nm. The synthesized nanophosphor strongly exhibits bright orange emission under 408 nm excitation. Comparative photoluminescence (PL) analysis of CTO:Sm3+ and Na+ co-doped CTO:Sm3+ nanophosphors irrefutably reveals that incorporation of Na+ facilitates almost threefold increase in the luminescence intensity along with significant improvement in thermal stability. Obtained results conclusively suggest that strong orange emitting Na+ co-activated Sm3+ doped CTO nanophosphor could be a potential candidate for use in blue light chip based warm WLED and others lighting device applications.

Broadband orange phosphor by energy transfer between Ce3+ and Mn2+ in Ca3Al2Ge3O12 garnet host

Ca3Al2Ge3O12 phosphors, singly doped with Ce3+ and co-doped with Mn2+, were synthesized by the solid-state reaction in ammonia atmosphere at 1200 °C using Li2CO3 as a flux. The band gap energy of the host was determined to be 3.7 eV. In these phosphors, Ce3+ ions exclusively occupy the Ca2+ site, while Mn2+ ions occupy both the Ca2+ and Al3+ sites. Under 420 nm excitation, the Ce3+:Ca3Al2Ge3O12 phosphor emits bluish-green light from Ce3+ (470 nm) with a Stokes shift established at 2280 cm−1. The Ce3+/Mn2+:Ca3Al2Ge3O12 phosphor excited at 420 nm emits orange light (580 nm) from Mn2+ in the Ca2+ site due to the Ce3+→Mn2+ energy transfer almost exclusively to this site. Ce3+ emission in the co-doped phosphor is very weak, even for relatively small concentrations (1%) of Mn2+. For Mn2+ concentration of 5% it disappears almost completely. Luminescence quantum yields of these phosphors amount to 24% and 20% in the case of Ce3+:Ca3Al2Ge3O12 and Ce3+/Mn2+:Ca3Al2Ge3O12, respectively. The critical distance for Ce3+ → Mn2+ energy transfer was calculated to be 6.2 Å and the efficiency of the energy transfer was estimated as 88%. These parameters suggest a non-uniform distribution of doped ions and the formation of Ce-Mn clusters.

Crystal Structure and Site Symmetry of Undoped and Eu3+ Doped Ba2 LaSbO6 and BaLaMSbO6 Compounds (M=Mg,Ca): Tuning Europium Site Occupancy to Develop Orange and Red Phosphor.

Double perovskite antimonates of the type BaLaMSbO6 (M=Mg, Ca) were synthesized by a standard solid-state route. The compounds were characterized by X-ray crystallography and the structures were refined using Rietveld method. BaLaMgSbO6 and BaLaCaSbO6 crystallized in monoclinic space groups (I2/m) and (P21 /n), respectively. In both compounds, La occupied the A-site of perovskite, which is 12-coordinated as compared to Ba2 LaSbO6 where La ion shifts to the B-site octahedral coordination due to the larger size of Ba as compared with Mg and Ca. The samples were further characterized using FTIR and the frequency of the octahedral vibration is correlated to the electronegativity of the B-site ions. Photoluminescence study of the title compounds and Ba2 LaSbO6 was carried out upon doping with 2 atom% Eu3+ ion, which confirmed that Eu3+ occupies distorted 12-coordinated A-site in BaLaMSbO6 (M=Mg, Ca) and symmetrical octahedral B-site in Ba2 LaSbO6 . Furthermore, the emission spectrum corresponding to each Eu3+ ion at different crystal site was successfully isolated through a TRES study. This site selective occupancy of Eu3+ ion also has a direct impact on the light emission, which was found to change from orange to red in a dark room in the order Ba2 LaSbO6 : Eu→BaLaCaSbO6 : Eu→BaLaMgSbO6 : Eu. Such an outcome will have high impact in designing new commercial Eu3+ ion doped phosphor materials and tailoring of their optical properties.

White polymer light-emitting diodes based on dibenzo-24-crown-8 decorated orange-emitting iridium complexes

Two orange phosphorescent iridium complexes decorated by dibenzo-24-crown-8 unit as the dopants were used into polymer light-emitting diodes (PLEDs) with a configuration of ITO/PEDOT:PSS/emission layer (EML)/CsF/Al. Monochromic orange-emitting PLEDs using complex 2 as dopant and poly(N-vinylcarbazole) (PVK) as host exhibit best device performance with a peak luminous efficiency (LE) of 8.94 cd/A at a current density of 1.3 mA/cm2 and a Commission Internationale de L'Eclairage (CIE) coordinate of (0.52, 0.41). More importantly, several white polymer light-emitting diodes (WPLEDs) were also fabricated with the skyblue–orange dual emitters system. The WPLEDs combination of the orange phosphor complex 2 with skyblue phosphor iridium(III)bis(2-(4,6-difluorophenyl)-pyridinato-N,C2′)picolinate (FIrpic) in a single-emissive-layer exhibit best electroluminescent performances with a maximal LE of 5.12 cd/A at a current density of 2.63 mA/cm2, a turn on voltage of 6.5 V and a CIE coordinates of (0.33, 0.39), which is very close to the ideal CIE coordinate of (0.33, 0.33) for pure white color.

Synthesis and Luminescence Properties of Bi3+-Activated K2MgGeO4: A Promising High-Brightness Orange-Emitting Phosphor for WLEDs Conversion.

In this article we synthesized a series of phosphors K2MgGeO4:Bi3+ with high brightness for white light-emitting diodes (WLEDs) conversion and investigated their crystal structures and luminescence properties using powder X-ray diffraction, diffuse reflectance spectra, X-ray photoelectron spectroscopy, photoluminescence spectra, and absolute quantum efficiency. K2MgGeO4:Bi3+ phosphor exhibits intense absorption in near-UV area and presents a broad asymmetric emission band with the main peak located at 614 nm, which was ascribed to the 3P1 → 1S0 transition of Bi3+. The absolute quantum efficiency of the K2MgGeO4:0.01Bi3+ phosphor was measured to be 66.6%. Also, this orange emission with color chromaticity coordinates of (0.4989, 0.4400) has an excellent resistance to thermal quenching: its integrated intensity at 393 K still maintained ∼85% of the one at room temperature. The WLEDs devices with Ra = 93.8 were fabricated by employing K2MgGeO4:0.01Bi3+ as an orange phosphor, which contains abundant red light component in its emission spectrum. The excellent luminescent performance of K2MgGeO4:0.01Bi3+ suggests that it is a promising orange-emitting phosphor for near-ultraviolet WLEDs.

Confining Mn2+-Doped Lead Halide Perovskite in Zeolite-Y as Ultrastable Orange-Red Phosphor Composites for White Light-Emitting Diodes.

CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) have emerged as competitive candidate luminescent materials in the photoelectric fields due to their superior luminescence properties. However, the major drawback such as poor resistance to temperature, moisture, and irradiation of light, especially for the red QDs with I-, hinders their practical applications. Herein, we synthesized Mn2+-doped CsPbCl3 embedded in the cage of zeolite-Y as a new orange-red phosphor for the white light-emitting diode (WLED). The composites have significantly improved resistance to both elevated temperature and water over the bare Mn2+-doped QDs. The former exhibits little degradation whereas the latter shows apparent decline upon the irradiation of lights in the orange LED devices, which are fabricated by employing each material as a color-conversion phosphor coated on a 365 nm UV chip. A WLED is also achieved with a 365 nm UV chip coated with a CsPb(Cl0.5,Br0.5)3-Y blue phosphor and a CsPb0.75Mn0.25Cl3-Y orange phosphor. The device possesses a Commission Internationale de l'Éclairage coordinate of (0.34, 0.36), a correlated color temperature of 5336 K and a color rendering index of 81.

Unique Color Converter Architecture Enabling Phosphor-in-Glass (PiG) Films Suitable for High-Power and High-Luminance Laser-Driven White Lighting.

As a next-generation high-power lighting technology, laser lighting has attracted great attention in high-luminance applications. However, thermally robust and highly efficient color converters suitable for high-quality laser lighting are scarce. Despite its versatility, the phosphor-in-glass (PiG) has been seldom applied in laser lighting because of its low thermal conductivity. In this work, we develop a unique architecture in which a phosphor-in-glass (PiG) film was directly sintered on a high thermally conductive sapphire substrate coated by one-dimensional photonic crystals. The designed color converter with the composite architecture exhibits a high internal quantum efficiency close to that of the original phosphor powders and an excellent packaging efficiency up to 90%. Furthermore, the PiG film can even be survived under the 11.2 W mm-2 blue laser excitation. Combining blue laser diodes with the YAG-PiG-on-sapphire plate, a uniform white light with a high luminance of 845 Mcd m-2(luminous flux: 1839 lm), luminous efficacy of 210 lm W-1, and correlated color temperature of 6504 K was obtained. A high color rendering index of 74 was attained by adding a robust orange or red phosphor layer to the architecture. These outstanding properties meet the standards of vehicle regulations, enabling the PiG films with the composite architecture to be applied in automotive lighting or other high-power and high-luminance laser lighting.