Cyan Phosphor Research Articles

A comparison research on replacements of Ba2+ by Lu3+ and Ba2+-Si4+ by Lu3+-Al3+ in BaSi2O2N2:Eu phosphors

As a cyan-emitting oxonitridosilicate phosphor, BaSi2O2N2:Eu2+ can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes (WLEDs). However, low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting. The replacements of Ba2+ by Lu3+ and Ba2+-Si4+ by Lu3+-Al3+ can greatly increase the luminescence intensity and improve the thermal stability at the same time. With Lu3+ doping, the internal quantum efficiency ηIQE of Ba0.925Si2O2N2:0.03Eu2+,0.045Lu3+ is 24.08% higher than that of Ba0.97Si2O2N2:0.03Eu2+. After Al3+ co-doping, the ηIQE is further increased by 10.31% compared to Ba0.925Si2O2N2:0.03Eu2+,0.045Lu3+. When the temperature rises to 473 K, the luminescence intensity of Ba0.925Si2O2N2:0.03Eu2+,0.045Lu3+ maintains 62.32% of that at room temperature, which increases by 17.35% in relative to the Ba0.97Si2O2N2:0.03Eu2+, while the luminescence intensity of Ba0.925Si1.97O2N2:0.03Eu2+,0.045Lu3+,0.03Al3+ keeps 73.87% of the initial value, which increases by 18.52% compared to Ba0.925Si2O2N2:0.03Eu2+,0.045Lu3+. The mechanisms for luminescence and thermal stability improvement are proposed. The Ba0.925Si1.97O2N2:0.03Eu2+,0.045Lu3+,0.03Al3+ cyan phosphor, Y3Al5O12:Ce3+ yellow phosphor and CaAlSiN3:Eu2+ red phosphor are mixed thoroughly and coated on a blue LED (450 nm) to assemble a WLED. The WLED demonstrates a color rendering index (Ra) of 97.1 at 150 mA, and the R1–R15 values are all above 90. The results indicate that as an effective cyan compensator in WLED, the BaSi2O2N2:Eu2+,Lu3+,Al3+ phosphor has great application prospect in the field of full-spectrum lighting.

Design of a broadband cyan-emitting phosphor with robust thermal stability for high-power WLED application

Due to the complicated production process and reabsorption problem, the development and application for white light-emitting diodes (WLEDs) are affected. A combination of cyan and red phosphors with near-ultraviolet (n-UV) LED chip has been proposed to solve these problems. Its key is developing cyan phosphor with broad emission band and excellent performances. In this work, we have developed a broadband cyan-emitting phosphor RbBa2(PO3)5: Eu2+ (RBP: Eu2+) by a solid-state method. The phase purity, crystal structure, luminescence properties and their relationship were investigated systematically. The RBP: Eu2+ phosphor can yield asymmetric broadband cyan emission upon 350 nm light excitation, which is ascribed to the occupation of Eu2+ for both the Ba1 and Ba2 sites. The measurement of temperature-dependent luminescence implies that the phosphor remains 89.5% of the initial value at 150 °C, which is much better than the commercial Ba2SiO4: Eu2+ phosphor. Furthermore, a WLED device has been obtained by composing the RBP: 0.01Eu2+ and CaAlSiN3: Eu2+ phosphors with a 365 nm LED chip. The emitted white light can show fabulous performances with the color coordinates of (0.3792, 0.3359), correlated color temperature of 3841 K and CRI of 90.8. The results suggest the RBP: Eu2+ phosphor to be a promising candidate for high-power WLEDs.

The synthesis and photoluminescence characteristics Bi3+/Dy3+ doped Ca2LaTaO6 phosphors upon the NUV light excitation

The researches on cyan phosphors those can be effectively excited by near-ultraviolet (NUV) light are being hot topics lately because that they have potential applications in phosphor converted white light emitting diodes (pc-WLEDs) based on the NUV chips. In this work, Bi3+/Dy3+ doped Ca2LaTaO6 phosphors were prepared through a solid state reaction procedure, and their luminescence characteristics were investigated through the measurements of the luminescence spectra and the decay curves. The excitation spectra indicate that the Bi3+ or Dy3+ single doped and Bi3+/Dy3+ codoped Ca2LaTaO6 phosphors are suitable for NUV excitation due to the excitation spectra within 250–500 nm. The emission spectra show that the lights of Bi3+/Dy3+ codoped Ca2LaTaO6 phosphors locate in cyan region. The ptotoluminescence characteristics indicate that they have possible uses in pc-WLEDs based on NUV chips.

Study on Spectral Structure and Photoelectric Properties of LED Healthy Light Source

LED healthy light source by using a blue LED chip to excite phosphor was prepared successfully. Four kinds of LED commercial phosphors (cyan phosphor with a peak wavelength of 498 nm, green phosphor with 520 nm, yellow-green phosphor with 546 nm, and red phosphor with 628 nm) were selected that could be excited by blue light. A series of experimental studies were carried out on the different amounts of glue, different powder-glue ratio, different combinations of phosphors, and the influence of different driving currents. Trough the optimization of the experimental scheme, we obtained a LED healthy light source spectrum with luminous efficiency higher than 124 lm/w, color rendering index higher than 80, color temperature around 4000 k. These spectra are in good agreement with the full spectrum of sunlight, and the spectral continuity and uniformity are better, which accord with the requirements of bright (dark) vision, and the proportion of the blue spectrum is less than 2.4%, which meets the high quality and healthy lighting requirements of safety and comfort.

Using an excellent near-UV-excited cyan-emitting phosphor for enhancing the color rendering index of warm-white LEDs by filling the cyan gap

White light-emitting diodes (LEDs) with high color rendering index (CRI) and low correlated color temperature (CCT) are desirable for next-generation solid-state lighting. In this work, we demonstrated an efficient near-UV-excited cyan-emitting phosphor based on Ce3+-doped Ca2LuHf2Al3O12 (CLHAO) garnet, which could be used to cover the cyan gap for fabricating high-CRI warm-white LEDs. We found that the CLHAO:Ce3+ samples exhibited a broad excitation band in the 300–450 nm wavelength range peaking at 400 nm, and upon 400 nm excitation they showed broad cyan emission bands in the 420–600 nm spectral region with peak positions ranging from 477 to 493 nm. The optimal CLHAO:0.02Ce3+ sample had CIE color coordinates of (0.160, 0.255), and its internal and external quantum efficiencies were measured to be 84.3% and 60.8%, respectively. Impressively, the luminescence intensity of CLHAO:0.02Ce3+ sample at 423 K still remained at 62% of the initial value at 303 K, and the chromaticity shift was calculated to be as low as 1.7 × 10−2, revealing its high thermal stability and color stability at a higher temperature. Finally, a warm-white LED device (CCT = 3,194 K) was fabricated by combining CLHAO:0.02Ce3+ cyan phosphors with commercial blue/green/red tricolor phosphors, showing bright white-light emission with a high CRI of 89.4, which was superior to that of another warm-white LED device (CRI = 83.2) fabricated without CLHAO:0.02Ce3+ cyan phosphors. These outstanding luminescence properties of CLHAO:Ce3+ cyan phosphors illustrated that they offer a new feasible approach for the production of high-CRI warm-white LEDs toward high-color-quality solid-state lighting.

Cyan-Light-Emitting Chalcogenometallate Phosphor, KGaS2:Eu2+, for Phosphor-Converted White Light-Emitting Diodes.

A novel KGaS2 phosphor host that emits a cyan light was discovered to fill the cyan gap in the visible spectrum of phosphor-converted white light-emitting diodes (pc-wLEDs). KGaS2, belonging to the chalcogenometallates of the type ABQ2, was synthesized via a solid-state route with compositions optimized to achieve a phosphor host that would achieve the best photoluminescence (PL) properties. The activation with Eu2+ gave rise to PL in the cyan region of the spectrum with a PL maximum at ∼498 nm, as measured under the near-UV (420 nm) and blue (450 nm) excitations. The PL properties at the near-UV excitation are found to be much better, as compared to those obtained at the blue excitation. The Rietveld analysis, using high resolution synchrotron X-ray diffraction calibrated at a wavelength of 1.522 Å and selected area electron diffraction (SAED) pattern analysis of the composition optimized with the highest PL intensity, revealed a centrosymmetric monoclinic structure in the C2/c space group. The stoichiometry of the optimized composition, as estimated using Rietveld refinement, was revealed as KGa0.921S1.882:Eu2+. The decay curve measurement, using time-resolved spectroscopy, yielded a 10% decay time of 0.41 μs, which is much smaller compared with the decay time of the commercially available β-SIALON phosphor that has a 10% decay time of 1.71 μs. The white pc-LED, fabricated with a cyan phosphor, had a higher value on the color rendering index and a lower value for color correlated temperatures, as compared with the version fabricated without a cyan phosphor, which makes this novel phosphor suitable for applications as a pc-wLED.

Tuning luminescence of Ba3Si6O12N2:Eu2+ phosphor for full-spectrum warm white LED lighting

• A cyan emission was achieved via the replacement of Si-N with Al-O in Ba 3 Si 6 O 12 N 2 :0.05Eu 2+ . • The emission peak could be shifted from 512 nm to 495 nm. • The emission intensity of the optimal cyan phosphor is 36% higher than Ba 3 Si 6 O 12 N 2 :0.05Eu 2+ . • The CCT of wLED decreases from 4407 K to 4038 K and the Ra increase from 85.8 to 90.8. Developing cyan phosphors excited by near ultraviolet (n-UV) or blue LED chips is extremely significant for making up for the cyan cavity of the existing white light emitting diodes (wLEDs). In this research, a cyan emission was successfully achieved via the replacement of Si-N with Al-O in Ba 2.85 Si 6 O 12 N 2 :0.15Eu 2+ green phosphor. The emission peak could be shifted from 512 nm to 495 nm. The mechanism of spectral blue shift can be interpreted by the decrease of the crystal field splitting strength, which is induced by the square of the bond length and the decrease of centroid shift of 5d level, which is induced by the spectroscopic polarizability and 6th power of the bond length. The optimal cyan Ba 2.85 Si 5.65 Al 0.35 O 12.35 N 1.65 :0.15Eu 2+ phosphor possess a broad excitation and emission band at the same time, whose emission intensity is 36% higher than that of Ba 2.85 Si 6 O 12 N 2 :0.15Eu 2+ . The CCT of the wLED with Ba 2.85 Si 5.65 Al 0.35 O 12.35 N 1.65 :0.15Eu 2+ phosphor realizes from 4407 K to 4038 K and the Ra values achieve from 85.8 to 90.8. The results indicate that Ba 2.85 Si 6- y Al y O 12+ y N 2- y :0.15Eu 2+ phosphor can serve as a cyan component for application in full-spectrum warm white lighting.

Site-selective excitation and photoluminescence properties of a cyan-emitting NaGd9(SiO4)6O2: Bi3+ phosphor for potential application in white light-emitting diodes

Bismuth ions, as excellent non-rare-earth activators for luminescent materials, possess characteristic excitation in the near ultraviolet (n-UV) region rather than in the visible region and could avoid reabsorption as compared to traditional rare-earth (e.g., Eu2+, Ce3+) phosphors. In this work, a series of apatite-type NaGd9(SiO4)6O2: xBi3+ (NGSO) phosphors with a hexagonal crystal system were synthesized through high-temperature solid-solid reactions. They showed intense n-UV absorption and cyan emission of Bi3+ ions. The optimal Bi3+ doping concentration was 0.02. Further, there were two types of Bi3+ ions that provided seven- and nine-coordination in NGSO: xBi3+ phosphors, resulting in two luminescence centers at 462 and 558 nm, respectively. Bi3+ (Ⅰ) ions were dominant for the emission at 558 nm excited at a wavelength of 340 nm, and Bi3+ (Ⅱ) ions governed the luminescence at 462 nm excitation at 370 nm; energy transfer occurred from Bi3+ (Ⅰ) to Bi3+ (Ⅱ) ions. Finally, good thermal stability with activation energy (Ea) of 0.296 eV was demonstrated. These findings exhibit the potential application of NGSO: 0.02Bi3+ phosphors as cyan phosphors in n-UV white light-emitting diodes.

Cyan-emitting Ba0.45Ca2.5La6(SiO4)6: 0.05 Eu2+ and Ba1.45Ca1.5La6(SiO4)6:0.05 Eu2+ solid-solution phosphors for white light-emitting diodes

Two cyan-emitting phosphors with different bandwidths were successfully synthesized through the high-temperature solid-state method in a reducing atmosphere. The crystal structures, morphologies, and luminescence properties of the as-prepared phosphors were investigated. The Rietveld refinements of the powder X-ray diffraction (XRD) data demonstrated the single phase of the samples, and two crystallographic sites of La3+ were observed in the crystal structure. Under the excitation of UV light, both Ba0.45Ca2.5La6(SiO4)6: 0.05 Eu2+ and Ba1.45Ca1.5La6(SiO4)6: 0.05 Eu2+ phosphors emitted cyan light due to the 4f65 d1→4f7 transitions of the Eu2+ ion. The emission spectra could be well fitted by two component Gaussian peaks corresponding to two different coordination environments of the Eu2+ ions. The temperature-dependent photoluminescence spectra show a large difference on the thermal stability between the two phosphors. The two phosphors exhibit effective absorption of near-UV light and their internal quantum efficiencies (IQEs) were calculated as 31.5% and 42.4% under 295 nm UV-light excitation. The experimental results indicate that the novel cyan phosphors might have potential applications in white light-emitting diodes (LEDs) based on the near-UV LED chip.

Full-visible-spectrum lighting realized by a novel Eu2+-doped nitride-based cyan-emitting phosphor.

Cyan phosphors have attracted considerable attention in recent years as an indispensable component for realizing full-spectrum lighting. In this study, a novel nitride-based cyan-emitting phosphor Ca2BN2Cl:Eu2+ was successfully prepared. Its crystal structure refined by the Rietveld refinement reveals that Ca2BN2Cl is formed by a tight host lattice and the edge-sharing Ca(N,Cl)4 tetrahedrons along with multiple crystallographic Ca sites for Eu2+ ions to occupy, which corresponds to its broad emission band. Under the near ultraviolet (NUV) light excitation, Ca2BN2Cl:Eu2+ emits a broad-band cyan light and its full width at half-maximum (FWHM) can reach 121 nm, which effectively compensates the "cyan cavity". The time-resolved photoluminescence (TRPL) spectra of Ca2BN2Cl:Eu2+ were investigated to expose the energy transfer between the multiple luminescent centers. Furthermore, the temperature-dependent spectra of Ca2BN2Cl:Eu2+ were measured to evaluate its thermal stability. All of the discussion and results reveal that Ca2BN2Cl:Eu2+ is a promising cyan phosphor for use in white light-emitting diodes to realize full-spectrum lighting.

A cyan-emitting phosphor Ca3SiO4(Cl,Br)2:Eu2+ with high efficiency and good thermal stability for full-visible-spectrum LED lighting

In this study, Ca2.98SiO4Cl2-yBry:0.02Eu2+ cyan-green phosphors with high efficiency and good thermal stability were prepared by a low temperature synthesis. The crystal structure, luminescence properties and thermal stability of as-prepared phosphors were systematically investigated by means of X-ray diffraction (XRD), photoluminescence excitation spectra (PLE), photoluminescence spectra (PL), CIE coordinates and variable temperature spectra. Simply increasing Br− in Ca2.98SiO4Cl2-yBry:0.02Eu2+, the emission peak can be shifted from 502 nm to 491 nm under near-UV (n-UV) excitation, which can make amends for the cyan gap (480–520 nm) and realize high color rendering. The remarkable blue shift of the emission band can be ascribed to the small crystal field splitting and Stokes shift. The external quantum efficiency of Ca3SiO4ClBr:Eu2+ moves up to 55.58% and exhibits an impressively absorption efficiency. Furthermore, a white LED device was fabricated via blue-emitting Sr5(PO4)3Cl:Eu2+, green-emitting YAGG:Ce3+, red-emitting (Ca,Sr)AlSiN3:Eu2+, and the cyan phosphor Ca3SiO4(Cl,Br)2:Eu2+ with 410 nm-chip. The WLED exhibits a warm and bright white light with low correlated CCT (3969 K), high Ra (96.9), and CIE color coordinates of (0.3828,0.3810). The results indicate that Ca2.98SiO4Cl2-yBry:0.02Eu2+ can be used as a potential cyan phosphor for full-spectrum warm white LED.

Design of a Bismuth-Activated Narrow-Band Cyan Phosphor for Use in White Light Emitting Diodes and Field Emission Displays

To overcome the problem that Bi3+-activated phosphors suffer from, it is an urgent need to realize narrow-band light emission of Bi3+-activated phosphors, which not only improves their luminescence...

Ce3+ doped BaLu2Al2Ga2SiO12 — A novel blue-light excitable cyan-emitting phosphor with ultra-high quantum efficiency and excellent stability for full-spectrum white LEDs

It is well known that cyan-emitting phosphors play a very important role in full-spectrum white LEDs. A large number of cyan-emitting phosphors have been reported in the past few years, however, most of them can only be effectively excited by near-ultraviolet light. There are very few cyan-emitting phosphors that can be intensively excited by blue light (440 and 470 nm). Here, a novel blue-light excitable cyan-emitting phosphor BaLu1.95Ce0.05Al2Ga2SiO12 with excellent performance is reported. The cyan phosphor has a cubic structure in space group Ia3¯d with a = 1.205379(3) nm, which can be easily obtained through a solid-state reaction pathway. The emission peak of the cyan phosphor is located at 500 nm and its internal quantum efficiency is as high as 90.01% when excited at 455 nm at 25 °C. The cyan phosphor exhibits superior resistance against thermal quenching of luminescence, and its intensity at 125 °C is as strong as 92.14% of the intensity at room temperature. Meanwhile, it also shows an outstanding resistance against water, where its luminescence intensity is hardly changed after being immersed in pure water for 528 h. The white LED lamp prepared by employing the obtained BaLu1.95Ce0.05Al2Ga2SiO12 as cyan phosphor displays remarkable optical properties with CCT = 4441 K, Ra = 93.7, CRI = 90.4 and CIE 1931 (x, y) as (x = 0.3648, y = 0.3752). The experimental results demonstrate that BaLu1.95Ce0.05Al2Ga2SiO12 is a promising cyan-emitting phosphor with great application potential in full-spectrum white LEDs.

Achieving full-visible-spectrum LED lighting via employing an efficient Ce3+-activated cyan phosphor

At present, near-ultraviolet-pumped white light-emitting diodes (LEDs) based on tri-color (blue, green, and red) phosphors still suffer from insufficient color rendering index (CRI), due to the presence of cyan gap in the 480–520 nm spectral range. To solve this problem, it is urgent to develop an efficient cyan phosphor with emission peak around 490 nm and absorption band in the near-ultraviolet range of 380–420 nm. Herein, a highly efficient cyan-emitting Ca2GdHf2(AlO4)3:Ce3+ (CGHA:Ce3+) garnet phosphor with internal quantum efficiency as great as 80% is reported. Impressively, the CGHA:1%Ce3+ sample showed a broad excitation band ranging from 350 to 470 nm with a maximum at 408 nm, and upon 408 nm excitation it exhibited an intense broad cyan emission band in the 420–700 nm wavelength range with peak at 489 nm and a full width at half-maximum of 103 nm. Importantly, by applying the newly discovered cyan-emitting CGHA:1%Ce3+ phosphors as color converter, the CRI value of the fabricated warm-white LED device is greatly enhanced from 80.5 to 91.6. This work demonstrates that the novel developed CGHA:Ce3+ cyan phosphors could compensate for the cyan gap and realize full-visible-spectrum lighting, which have a bright prospect in high-quality solid-state white lighting.

Multi-site occupancies and photoluminescence characteristics in developed Eu2+-activated Ba5SiO4Cl6 bifunctional platform: Towards manufacturable optical thermometer and indoor illumination

Eu2+-activated Ba5SiO4Cl6 phosphors with blue and green emissions were synthesized by a solid-state reaction route in a reduction atmosphere. The obtained crystal structure and photoluminescent properties indicated that three various Ba2+ ions sites were partially occupied by the Eu2+ ions. The optimal doping content for Eu2+ ions in the Ba5SiO4Cl6 system was 5 mol%. The electric dipole-dipole interaction was attributed to the involved concentration quenching effect. The thermal resistance performance was identified by using the temperature-dependent emission spectra. Importantly, the internal quantum efficiency of the established final products reached up to 50.8%. Through utilizing the diverse sensitivities of blue and green emissions from Eu2+ ions to the temperature, a neoteric optical thermometer with a high absolute and relative sensor sensitivity of 0.031 K-1 and 0.87% K−1, respectively, at 498 K was achieved. By integrating the resultant cyan phosphors, commercial CaAlSiN3:Eu2+ red phosphors and a near-ultraviolet chip, the warm white light-emitting diodes with admirable colorific properties were integrated and manufactured. The complementary results elaborate that the Eu2+-activated Ba5SiO4Cl6 phosphors are bifunctional platforms for both optical thermometer and indoor illumination.

Current Situation and Trend of the Phosphors for Full Spectrum LED Lighting

With the increase of the requirements for lighting quality, full spectrum light emitting diode (LED) lighting becomes the development hotspot. In this paper, the key materials for full spectrum LED phosphors are discussed and compared in detail. The advantages and disadvantages, research progress, and practical application of various color phosphors excited by violet and near ultraviolet light are emphasized, and then the existing problems, development trend, and industrial direction in this field are analyzed and prospected. Currently, there remain many problems in the phosphors excited by violet and near ultraviolet light, which can be applied in full spectrum. For example, the blue and cyan phosphors take on narrow emission spectrum, low light efficiency, and poor thermal stability; yellow phosphors and far-red phosphors have a low luminous efficiency due to their low absorption of violet or near ultraviolet light; and single matrix white phosphors have insufficient red light emission. Among them, luminous efficiency and thermal stability are the key factors restricting the application of the phosphors. Therefore, it is urgent to research the preparation and application technology of wide spectrum blue, cyan, yellow green, yellow, far-red, and single matrix white phosphors with high light efficiency and thermal stability, and develop the high-efficient and continuous preparation technology of the present phosphor products, to promote the further development of full spectrum LED.

Cyan phosphors for full-visible-spectrum lighting: shining new light on high-CRI white pc-LEDs

Cyan phosphors for full-visible-spectrum lighting: shining new light on high-CRI white pc-LEDs

Processing and valence-dependent photoluminescence of (Tb1-xEux)3Al5O12 garnet phosphors (x=0.0025–0.05)

Calcination of coprecipitated precursors at 1500 °C in air produced (Tb1-xEux)3Al5O12 garnet phosphors (x = 0.0025-0.05) that exhibit dominant excitations via 4f8 → 4f75d1 (E1-4) and 7F6 → 5D3,4 transitions of Tb3+ and negligible excitation of Eu3+. Exciting the phosphors with 275 nm light (E2 transition of Tb3+) produced the typical 5D0 → 7FJ red emissions of Eu3+. Annealing the x = 0.03 sample in hydrogen at 1500 °C reduced ∼62.8% of Eu3+ to Eu2+ and yielded a cyan phosphor that simultaneously exhibits the luminescence of Eu3+ (red), Tb3+ (green) and Eu2+ (broad-band, 400–725 nm) under 327 nm excitation (E1 transition of Tb3+). The (Tb0.97Eu0.03)AG optimal phosphors calcined in air and hydrogen were assayed to have external/internal quantum efficiencies (in percentage) of ∼23.2/24.2 and 18.6/23.7, respectively. Luminescence features of the two types of phosphors were investigated in detail, and the energy transfer among Tb3+, Eu2+ and Eu3+ ions was discussed.

Novel cyan‐emitting KBaScSi2O7:Eu2+ phosphors with ultrahigh quantum efficiency and excellent thermal stability for WLEDs

AbstractOwing to the conventional phosphor‐converted white LEDs (pc‐WLEDs) generally suffer from blue‐green cavity, thus, developing an appropriate phosphors covering both the blue and green regions in their emission spectra are very urgent. Herein, a novel Sc silicate phosphor, KBaScSi2O7:Eu2+ (KBSS:Eu2+), has been successfully designed and prepared via a solid‐state reaction. The crystal structure, luminescent properties, thermal quenching, quantum efficiency as well as its application in UV‐pumped WLEDs have been investigated systematically. The KBSS:Eu2+ phosphor exhibits a strong and broad excitation band ranging from 290 to 450 nm, and gives a sufficient cyan emission of 488 nm with a full‐width half‐maximum (FWHM) of 70 nm, which filled the blue‐green cavity. Importantly, the optimized KBSS:Eu2+ phosphor possesses an ultrahigh quantum efficiency (QE) up to 91.3% and an excellent thermal stability retaining 90% at 423 K with respect to that measured at room temperature. Finally, the as‐fabricated UV‐based WLEDs device, with only coupled the mixture of KBSS:Eu2+ cyan phosphor and CaAlSiN3:Eu2+ red ones to a commercial 365nm UV chip, exhibits a satisfactory color‐rendering index (Ra = 88.6), correlated color temperature (CCT = 3770K), and luminous efficiency (LE = 21 lm/W).

Luminescent properties of a new cyan long afterglow phosphor CaSnO3:Lu3.

Persistent luminescence (PPL) materials have gained lots of attention and have been widely used in traffic signs, displays, medical diagnosis and architectural decoration. Single ion doped PPL materials with stable emission are excellent for practical applications, but it is difficult to cover the entire wavelength range. Here, a new cyan long-lasting phosphor CaSnO3:Lu3+ was successfully synthesized at 1200 °C by the conventional high temperature solid state method. From the X-ray photoelectron spectroscopy (XPS), it can be concluded that the Sn2+ ions exist in the crystal lattice because the doping of Lu3+ ions changes the valence state of the Sn ions. According to the thermally simulated luminescence (TSL), the continuous afterglow of CaSnO3:Lu3+ phosphors is produced by appropriate hole or electron traps, which are caused by doping the calcium stannate host with rare earth ions (Lu3+). The long-lasting phosphorescence (LLP) properties of the cyan phosphor were first discussed and the afterglow mechanism was expounded in detail. The excitation and the emission spectra of the phosphor revealed the characteristic broad peak of the Sn2+ ion. Typical afterglow behavior of the CaSnO3:Lu3+ phosphors was exhibited after power was turned off.