Near-ultraviolet Chip Research Articles

Development of highly thermal-stable blue emitting Y4Al2O9:Bi3+ phosphors for w-LEDs, fingerprint and data security applications

A new blue-emitting Y4Al2O9:Bi3+ (YAO:Bi3+) phosphor is synthesized using the solution combustion method with mushroom extract as a binder. Its structural properties, concentration effects, temperature-dependent luminescence, and performance in LED devices are thoroughly investigated. Upon excitation at 367 nm, a strong blue light emission at 423 nm is observed, attributed to the 3P1→1S0 transition of Bi3+. The quantum efficiency reached approximately 63.5 %. The CIE diagram shows that the emission colour falls within the intense blue region, achieving a colour purity (CP) of 94 %. YAO:Bi3+ exhibits strong absorption in the near-ultraviolet range (330–400 nm), making it suitable for LEDs powered by near-ultraviolet chips. A thermal quenching experiment revealed an activation energy (Ea) of 0.323 eV, indicating that this YAO:Bi3+ phosphor possesses good thermal stability. This study showcases the use of YAO:Bi3+ phosphor in encapsulated LED devices. The device’s Commission Internationale de l’Éclairage (CIE) coordinates are (0.325, 0.310), with a high colour rendering index (CRI) of 94.70 and a low correlated colour temperature (CCT) of 5915 K at a current of 120 mA. These properties indicate that this phosphor is suitable for developing white LED devices powered by near-ultraviolet chips. The optimized YAO:Bi3+ phosphor is employed to enhance the detection of Level I-III fingerprint (FP) details with high resolution and contrast, showing effective visualization of latent fingerprints (LFPs) on various substrates. Furthermore, it is used as a model for developing fluorescent ink, which is applied to different media. The results suggest that YAO:Bi3+ phosphor has significant potential for applications in w-LEDs, advanced forensics, and anti-counterfeiting ink technologies.

Bi3+-activated Na3Ca2TaO6: A novel narrow-band blue-emitting phosphor towards backlight display applications

Developing efficient and stable narrow-band blue phosphors has always been crucial for advancing LED backlighting technology. In this study, a host of Na3Ca2TaO6 with a strong rigid structure and high cationic site symmetry was selected, while Bi3+ was utilized as the activator. A novel narrow-band blue-emitting phosphor Na3Ca2TaO6:Bi3+ was obtained through high temperature solid phase sintering. The excitation peak of Na3Ca2TaO6:0.005Bi3+ is at 370 nm, which can effectively match the near-ultraviolet chip. Under near-ultraviolet light excitation, the Na3Ca2TaO6:0.005Bi3+ sample exhibits narrow-band blue emission, characterized by a dominant peak at 421 nm and a full width at half maximum of 47 nm. Additionally, Na3Ca2TaO6:Bi3+ demonstrates the color purity of 93.7 %, a quantum efficiency of 56.3 % and thermal stability of 80 %@150 °C. Based on crystal structure data, spectral data, and empirical formulas, it can be inferred that Bi3+ occupies the Na2 and Ca site and forms two luminous centers in Na3Ca2TaO6. When Na3Ca2TaO6:Bi3+ is utilized as the blue light component in WLED devices packaging, an impressive NTSC color gamut of 89.4 % can be achieved. The present study is anticipated to serve as a valuable point of reference for the future advancement of phosphors specifically tailored for backlight display applications.

Bright white light emission from lanthanide oxide LaGdO3 for LED lighting by Bi3+ to Eu3+ energy transfer.

Phosphors with intrinsic white light emission are of great potential in constructing high-quality white LEDs (WLEDs). In this work, we propose the use of energy transfer from Bi3+ to Eu3+ ions for white light emission. A unique Bi3+-activated phosphor LaGdO3 (LGO):Bi3+ was generated using the conventional high-temperature solid-state process. An energy transfer was established by introducing Eu3+ into the phosphor composition. The emission colour of LGO:Bi3+,Eu3+ phosphors changes from cyan to white to orange-red depending on the Bi3+/Eu3+ doping proportion. The energy transfer between the Bi3+ and Eu3+ ions results from the dipole-dipole interaction. The LGO:Bi3+,Eu3+ phosphors were combined with a near-ultraviolet chip to successfully create a single-component WLED device with a colour-rendering index of 92.4. Our work demonstrates the energy transfer as a route for single-component white light emission and makes LGO:Bi3+,Eu3+ phosphors one of the candidate materials for near-ultraviolet lighting.

Luminescent properties of ZSM-5 zeolite phosphor and its application to aquatic plant lighting and white LEDs

In order to explore ideal materials with suitable excitation wavelengths, high thermal stability and good emission characteristics for phosphor-converted white light emitting diodes (pc-WLEDs), in this work, a blueish-white phosphor (λex = 390 nm) was realized by a new strategy of carbocations formation in ZSM-5 zeolite, which maintains the luminescence intensity at 473 K is 103% of that at room temperature. Following immersion in ethanol, water, 40 wt% sodium hydroxide solution (NaOH), and concentrated hydrochloric acid (HCl) for 120 h, the luminescence intensity was maintained at 92%, 87%, 80%, and 82% of the normal state, respectively. By packaging the sample on a near-ultraviolet (NUV) chip (390 nm), a blueish-white pc-LED was fabricated, which has a promising commercial prospect in the field of aquatic plant lighting. Meanwhile, a pc-WLED device was fabricated by combining a 390 nm NUV chip and ZSM-5 zeolite and red phosphor K2MgGeO4:Eu3+. It has an excellent property with the correlated color temperature (CCT) = 4600 K and color rendering index (CRI) = 91.5, indicating that ZSM-5 zeolite has good application prospects in the pc-WLEDs field.

Development of single matrix aluminum silicate fluorescent powder activated by Bi3+, Eu3+, and Eu2+ and use in white LEDs

In the field of luminescent materials, the search for good substrates and the use of a single substrate to excite near-ultraviolet chips to produce white LED devices has always been of great interest. This study utilized energy transfer between Bi3+ and Eu3+ to design KAlSiO4: 0.02Bi3+, 0.04Eu3+ red emission phosphors with a potassium nepheline structure, which were calcined in air with a high-temperature solid-state method. Under 286 nm excitation, energy transfer between Bi3+ and Eu3+ up to 85.9 %. Through DFT theoretical calculations, it was found that the bandgap of the matrix was 4.86 eV, KAlSiO4: 0.02Bi3+, 0.04Eu3+ has excellent heat quenching resistance, and the emission intensity at 150 °C is 92.9 % of that seen at room temperature. Second, by doping with Eu2O3 and calcining in a reducing atmosphere, KAlSiO4: 0.02Eu2+, 0.1Li+ broadband blue emitting phosphors were obtained. Finally, KAlSiO4: 0.02Bi3+, 0.04Eu3+ was mixed with KAlSiO4: 0.02Eu2+, 0.1Li+ to prepare a near-ultraviolet white LED device. The color rendering index of the device reached 87.1, the color coordinates were (0.3328, 0.3015), and the color temperature was 5422 K. These results proved that KAlSiO4: 0.02Bi3+, 0.04Eu3+ samples have potential for use in near-ultraviolet white LEDs and that KAlSiO4 is a good substrate in the field of luminescence. This work provides a new breakthrough in the use of a single substrate to prepare multiple colored fluorescent powders and mix them together to produce white LED devices.

Insight into the optical evaluation of sunlike LED devices with full-visible spectrum emission based on ultra-low melting tin fluorophosphate glass for human centric lighting

Full spectrum sunlike light-emitting diode (LED) devices in the wavelength range of 380–670 nm have received much attention for their applications in human centric lighting. Herein, the inorganic color converter of the sunlike phosphor-in-glass (PiG) has been developed by embedding the green-emitting (Lu3-xYxAl5O12: Ce3+) and red-emitting (Sr0.6Ca0.4AlSiN3: Eu2+) phosphor powders in ultra-low melting tin fluorophosphate glass. Notably, the sunlike PiG exhibits the full spectrum in the wavelength range of 380–670 nm under the excitation of a near-ultraviolet (NUV) chip. Tunable color temperature (2785 K–5806 K) and high color rendering index (Ra = 95) were obtained by varying the mix ratio of the red-emitting component in the glass matrix. Further, the full visible spectrum emission was regulated by adjusting the Lu/Y ratio of the green phosphor Lu3-xYxAl5O12: Ce3+ and the color quality was further optimized (Ra = 97). The color quality of white light-emitting diode (WLED) was systematically investigated using Illuminating Engineering Society (IES) of North America evaluation systems and the LED devices exhibit fidelity index (Rf) and gamut index (Rg) close to sunlight (Rf = 95, Rg = 101). Compared with the traditional phosphor-in-silicone (PiS), the sunlike PiG based WLED exhibits a low working temperature of ∼37 °C for high power LED. Therefore, the WLED devices based on sunlike-PiG can be regarded as promising candidates for ultra-high color rendering index light sources because of the adjustable color temperature, high color quality, low-efficiency loss, excellent thermal properties and water stability.

Study of morphological, elemental, optical and excitation wavelength dependent red photoluminescence in Eu3+ doped Li2SrSiO4 for solid state lighting

A comprehensive investigation of Eu3+ doped Li2SrSiO4 phosphors synthesized via the solid-state reaction method was conducted. XRD confirmed the crystalline phase and SEM along with and its 3D projection's observations confirmed that the phosphor particles were in the micro meter size range, indicating their suitability for applications in primary phosphor-converted LEDs. FTIR spectroscopy elucidated vibrational characteristics, while TGA, EDX and XPS analysed thermal stability, elemental composition and valence states respectively. Doping-induced band gap increase was attributed to the Moss-Burstein effect. Photoluminescence excitation studies revealed enhanced absorption at 394 nm compared to the charge transfer transition band (CTB) at 254 nm, aligning with industry-standard near-ultraviolet chips. XPS suggested two distinct Eu3+ sites in the LSS crystal, corroborated by excitation wavelength-dependent PL emission. As a result of excitation wavelengths, the magnetic-dipole transition (5D0 → 7F1) at 592 nm, the electric-dipole transition (5D0 → 7F2) at 615 nm and the induced electric-dipole transition ((5D0 → 7F3,4) at 650 and 700 nm arose. Additionally, the phosphor gave an improved conversion efficiency at 2% Eu doping. Low synthesis temperature, micro-sized particles, thermal stable, short lifetime, excitation bands at near UV to blue region, colour tunability, lower CCT, LER and similar CIE to available red phosphors are the key factors for the Li2SrSiO4:Eu3+ proving reliable red phosphor for solid state lighting.

A high-efficiency double perovskite phosphor SrLaNaTeO6:Mn4+: Potential applications in w-LEDs and indoor plant growth lighting

A novel deep-red phosphor with Mn4+-doped double perovskites SrLaNaTeO6 (SLNTO) was synthesized by the conventional high-temperature solid-state method. SLNTO contains both [NaO6] and [TeO6] octahedra. The octahedral structure of double perovskites facilitates the doping of Mn4+. The band gap (Eg) of the direct semiconductor SLNTO is 2.88 eV. With an excitation wavelength of 322 nm, SLNTO:Mn4+ has a 700 nm deep-red wavelength emission assigned to the energy level transition from 2E1g to 4A2g of Mn4+ ions. Photoluminescence (PL) of the sample and phytochrome far-red light (PFR) absorption are satisfactory matches. According to the Tanabe-Sugano diagram, Mn4+ is located in the strong crystalline field for 2E1g. A 2.0 mol% concentration of Mn4+ is optimal; further high doping results in concentration quenching, ascribed to the neighbour ion interaction and dipole‒dipole (d-d) interactions. The internal quantum efficiency (IQE) is 87.84 %. Additionally, the electroluminescent (EL) spectrum of the encapsulated plant growth lamp overlaps with the chlorophyll a and b absorption spectra. Its Commission Internationale de l'Eclairage (CIE) coordinates of SLNTO:2.0 mol%Mn4+ phosphor with a near-ultraviolet (n-UV) chip are located in (0.720, 0.280). The phosphor-converted white light-emitting diode (pc-WLED) has a high colour rendering index (Ra = 96) with a suitable correlated colour temperature (CCT = 6240 K). The results are satisfactory for white light-emitting diodes (w-LEDs) and plant growth lamps.

K2CaPO4F:Eu2+,RE3+ for pc-WLEDs: Cationic substitution inducing tunable emission and anti-thermal quenching

Near-ultraviolet (n-UV) chip based phosphor-converted white light-emitting diode (pc-WLED) is proposed as one of the methods to realize full-spectral illumination with high color rendering index (CRI). Accordingly, it is crucial to explore n-UV excitable, efficient, and thermally stable phosphors. Here in, the redistribution of Eu2+ on different crystallographic sites (K and Ca) of K2CaPO4F was achieved by introducing Ce3+ and other optically inert rare earth (RE) ions (La3+, Y3+, and Lu3+). This cationic substitution resulted in the enhancement of blue emission, the weakening of red emission, and the appearance of white emission finally. The introduction of RE3+ not only improves the excitation at ∼400 nm, but also changes the quantum efficiency and thermal stability of the phosphors. For example, the introduction of Y3+ increases the external quantum efficiency from 52 % to 62 %. The introduction of Ce3+, Y3+, and Lu3+ brings traps and therefore results in anti-thermal quenching behavior within 398 K. The pc-WLEDs fabricated by covering a 365/380 nm chip with phosphor blend containing K2CaPO4F:Eu2+,RE3+ can emit a warm white light with a CRI as high as 98. This work provides an effective approach to tune the luminescence properties for high performance solid-state lighting.

Highly efficiency blue emissive from Bi3+ ions in zero-dimensional organic bismuth halide for white LED applications

Zero-dimensional organic-inorganic metal halides (OMHs) attract increasing interest in the fabrication of light-emitting diodes because of their broad emission band and high photoluminescence quantum yield. Thus, almost all OMHs showed green and yellow emissions, while blue was rarely reported. The luminescence mechanism of OMHs was attributed to the self-trapped excitons (STEs), no matter the similar performances between STEs and translations from energy levels of ns2 ions (Sb3+, Bi3+, and Te4+ ions). In this work, zero-dimensional organic tetraphenylphosphonium bismuth chloride TPP2BiCl5 (C48H40P2BiCl5, abbreviated as TBC, TPP=tetraphenylphosphonium.) was synthesized via the antisolvent method The obtained TBC showed the highest efficiency (58%) in blue light emission at 480 nm. While most of the OMHs function according to the STE mechanism, the emission of TBC was confirmed to originate from the 3P1-1S0 transition of Bi3+ ions. The white light-emitting diodes (WLEDs) with a color rendering index of 81 were fabricated by using a near-ultraviolet (NUV) chip, blue emitting single crystal TBC, green-emitting single crystal TPP2MnCl4 (C48H40P2MnCl4, abbreviated as TMC), and red-emitting single crystal TPP2SbCl5 (C48H40P2SbCl5, abbreviated as TSC). Moreover, the single-component white emission was achieved by doping Mn2+ and Sb3+ ions into the lattice of TBC. This work demonstrates the different emission mechanism of ns2 ions based OMHs, and the great potential of bismuth-based OMHs in the applications of WLEDs.

Preparation and luminescence properties of Ba0.92-xSrxAl2Si2O8:0.08Eu2+ blue-cyan phosphors for white light LEDs

Currently, there is a cyan gap in white light-emitting diodes (LEDs) manufactured by combining near-ultraviolet (NUV) chips with tricolour (blue/green/red) phosphors, resulting in a poor colour rendering index (Ra). Broadband blue-cyan phosphors contain blue, cyan and green luminescent components that complement the cyan gap. In this paper, feldspar-structured Ba0.92-xSrxAl2Si2O8:0.08Eu2+ (x = 0–0.5) phosphors were prepared by a high-temperature solid-phase method and a cation substitution strategy. A phase transition was achieved by varying the concentration of x, which resulted in the formation of two luminescent centres and a 10.33-fold enhancement of the luminescence intensity for Ba0.92Al2Si2O8:0.08Eu2+. The colour of the emission changed from the original green to blue-cyan, and the strongest emission peak with a half-height width of 94.5 nm was observed at a Sr2+ concentration of 0.3 (30%) and covered the blue, cyan and green wavelength ranges (390–600 nm). The experimental value of the optical band of the substrate is 5.71 eV, and the luminous intensity of the Ba0.62Sr0.3Al2Si2O8:0.08Eu2+ sample at 150 °C was 91.3% of that at room temperature. Ba0.62Sr0.3Al2Si2O8:0.08Eu2+, (Ca, Sr) AlSiN3:Eu2+ and 365 nm NUV chips were successfully packaged into white LED devices. The colour rendering index (Ra) of the prepared white LED devices was 87, R9 was 89, the colour coordinates were (0.3763, 0.3382), and the colour temperature was 3759 K, which effectively solves the problem of the lack of cyan luminescent components in white LED devices and simplifies the manufacturing process of white LEDs.

Wide-band blue-emitting in Ce3+ doped Ca2YZr2Al3O12 garnet-type phosphor designed via local structural lattice distortion and synthesized in nonreducing atmosphere

It is of great significance to explore blue photoluminescent phosphor for white light-emitting diodes excited by near-ultraviolet chip. However, it is very challenging to prepare efficient blue luminescence in phosphor by an unsophisticated synthesis process. In this work, a series of blue-emitting Ca 2 Y 1-x Zr 2 Al 3 O 12 : xCe 3+ phosphors are designed via local lattice distortion and synthesized in nonreducing atmosphere. The crystal structure of samples and the coordination environment of Ce 3+ have been investigated in detail by X-ray diffraction and Rietveld refinement method. The wide-band blue emission peaking at 460 nm is attributed to a relaxed crystal field strength. Based on dodecahedron distortion caused by unequal increase of Ce–O bond length, the wavelength of blue color luminescence tuning can be realized from 459 nm to 472 nm. In addition to the concentration quenching effect, the fluorescent lifetimes, thermal quenching effect, the internal quantum efficiency, CIE chromaticity coordinates and related mechanisms of samples have also been studied systematically. Using the representative sample with other tricolor phosphors on a 365 nm chip, a prototype LED device with chromaticity point of (0.394, 0.384) and high CRI (93.5) at CCT of 3755 K is fabricated. All the results suggest that Ca 2 Y 1-x Zr 2 Al 3 O 12 : xCe 3+ phosphors can be conducted as potential alternative of blue-emitting phosphor for near-ultraviolet pumped white light-emitting diodes.

Strategy to probe multimodal light emissions from Eu3+/Yb3+ activated garnet nanophosphors for LED devices and solar cell applications.

This study investigates multimodal light emission from an Eu3+/Yb3+ activated Y3Ga5O12 (YGG) nanophosphor synthesized using a low temperature solution combustion method. The prepared sample possesses a cubic phase and an Ia3̄d space group and this is confirmed with X-ray diffraction and Rietveld refinement analysis. The synthesized sample shows orange-red emission bands because of the f-f transitions of Eu3+ under UV (393 nm) and NIR (980 nm) excitations via downshifting (DS) and upconversion (UC) processes, respectively. Upon UV (393 nm) excitation of the sample, the Eu3+ ions absorb this energy and then transfer it to a neighboring pair of Yb3+ ions giving NIR emission (900-1100 nm) corresponding to the 2F5/2 → 2F7/2 transition of Yb3+. The energy transfer from a single Eu3+ ion to a pair of Yb3+ ions is possible because of the quantum cutting (QC) process and this energy transfer efficiency is found to increase with the increasing concentration of the Yb3+. The quantitative estimation of energy transfer and internal quantum cutting efficiency is determined by measuring the decay kinetics. An activation energy of 0.25 eV indicates the good thermal stability of the sample. Furthermore, samples are suitable for use in practical applications in lighting devices by combining them with the near-ultraviolet (NUV; InGaN) chip. The fabricated LED device shows stability with the driving current flow values. Studies indicate that the present nanophosphor could be useful for display devices, and in enhancing the spectral conversion efficiency of the solar cells.

Blue-green luminescence properties and charge compensation of Ca9MgLi(PO4)7 doped with Tb3+ and alkali metal ions

Abstract Ca9MgLi(PO4)7: 4%Tb3+, 4%R+ (R = Li, Na, K) phosphors were synthesized by a solid-state reaction method. The crystal structure, morphology, composition and luminescent properties of as-prepared samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometer (EDS), high-angle annular dark field (HAADF) and spectroscopy technique. The effect of a small concentration of charge compensators like Li+, Na+, K+ on Ca9MgLi(PO4)7: Tb3+ phosphor has also investigated. Ca9MgLi(PO4)7: Tb3+, R+ (R = Li, Na, K) exhibit superior blue-green luminescence around 5D4 → 7F5 (543 nm) to Ca9MgLi(PO4)7: Tb3+ and can be effectively excited by 370 nm light, which implies that efficient charge compensation can promote the emitting of Tb3+ in Ca9MgLi(PO4)7. The CIE coordinates and decay lifetimes of typical samples were also studied. The Ca9MgLi(PO4)7: Tb3+, R+ (R = Li, Na, K) have promising application as a blue-green phosphor for near-ultraviolet chip excited white LEDs.

Versatile phosphor-in-glass based on Sn–F–P–O matrix with ultra-high color rendering for white LEDs/LDs

White light with excellent color rendering property has been highly required for comfortable and healthy illumination. A facile strategy to achieve high color rendering index (Ra >90) in practical applications is using near ultraviolet chips as excitation sources combined with RGB phosphors. However, achieving high color rendering with both blue chips and near-ultraviolet (NUV) chips for commercial phosphors dispersed in phosphor-in-glass (PiGs) materials is still a big challenge. In this work, the PiG based on the ultra-low melting point Sn–F–P–O glass with commercial green (Lu3Al5O12:Ce3+) and red (SrxCa1-xAlSiN3:Eu2+) phosphors has been successfully fabricated by one-step sintering method. The phase identification and distribution of monochromatic red phosphor in glass (R-PiG) and green phosphor in glass (G-PiG) were investigated in detail. The Sn2+ ions in Sn–F–P–O matrix show the intense blue emission bands centered at 420 nm under the excitation of NUV chips (365 nm). Notably, the polychromatic red/green phosphor in glasses (R/G-PiGs) are versatile and exhibited excellent color rendering (Ra = 93, Ra = 95, Ra = 92, respectively) properties excited by both blue chips, NUV chips and laser diodes (WLD). The working temperature of R/G-PiGs is stable at ∼33 °C and ∼55 °C when employed in WLEDs/WLDs (1 W), which greatly prevented the phenomenon of “thermal quenching” for the phosphors caused by high temperature. Thus, the versatile R/G-PiG with ultra-high color rendering and excellent thermal properties indicates its promising application in high-power white LEDs/LDs.

A phenomenon thermal denaturation of Copper(I) complexes with blue-to-red emission transition for white color displays

Here we report two luminescent copper complexes with different structures and luminescent properties, the blue-green [CuI(dmpyHS) (PPh3)2]⸱CH3CN (CuPy-PPh3) and the red [Cu6(dmpyS)6]⸱H2O (CuPy). When the blue-green light (CuPy-PPh3) is heated to above 147 °C, it loses the phosphine-containing ligand, PPh3, and turns into CuPy and instead emits red light. Many luminescent complexes show the change of luminescence properties when the temperature is lower than room temperature, while the luminescence change of CuPy-PPh3 occurs during the heating process above room temperature. Even more interesting, the luminescence wavelength transition span is large, from blue-green light emission at 490 nm to red light at 676 nm. The luminescence of the two copper complexes covers the three primary colors of red, green and blue required for the formation of white light emitting diodes WLEDs, which has potential in the development of non-rare earth phosphor white color displays. The integration of CuPy-PPh3 and CuPy on a 395 nm near-ultraviolet chip can assemble WLEDs with good white light properties, which provides a new way for the construction of rare earth-free phosphor WLEDs. The synthesis of the two luminescent copper complexes is simple and environmentally friendly. Even though the structures of two copper complexes have been reported, the synthesis methods are different from those in the related literature and the luminescence properties of these complexes have never been described previously. The red emission copper complex CuPy is obtained by the thermal conversion of the blue-green emission copper complex CuPy-PPh3, which is a new phenomenon discovered for the first time in this work.

Enhancement on the luminescence of Ca2B5O9Cl:Eu2+ by co-doping of Al3+ and Ba2+ ions for full spectrum lighting application

B3+ and Ca2+ ions in Ca2B5O9Cl host are replaced by Al3+ and Ba2+ ions, respectively, in order to change the host environment of Eu2+ for improving its luminescence properties. It is found that the blue emission centered at 453 nm under 410 nm excitation is increased by 28% at the Al3+ doping concentration of 14 mol% and Ba2+ doping concentration of 20 mol%. The luminescence intensity at 150 °C for the modified phosphor could maintain 67% of that at room temperature, indicating its good thermal stability. By combining a 410 nm near-ultraviolet chip with the blue phosphor developed in the present work, a red phosphor (SrxCa1-xAlSiN3:Eu2+), and a yellow-green phosphor (Y3Al5-xGaxO12:Ce3+), a pc-WLED device is fabricated, which can give warm white emission with CIE coordinate of (0.3847, 0.3888), and has high color rendering index (Ra = 97.4) and low correlated color temperature (CCT = 3978 K) at 3 V driving voltage.

A novel efficient red-emitting K7SrY2B15O30: Eu3+ phosphor with non-concentration quenching and robust thermal stability for white LEDs

Inhibiting energy migration between Eu3+ ions in a fixed host to get higher doping concentration is a permanent topic. Herein, a novel non-concentration quenching red-emitting K7SrY2-2xB15O30: xEu3+ (0.1 ≤ x ≤ 1.0) phosphor was synthesized via high-temperature sintering method. XRD measurement, Rietveld refinement results, and radius percentage deviation calculation demonstrated the phase purity and the occupation preference of Eu3+ ions. With continuously increasing doping Eu3+ ions, the absence of concentration quenching could be explained by long distance between two Eu3+ (7.012 Å) and the K7SrEu2B15O30 could exhibit striking photoluminescence performance with the highest emission wavelength centered at 617 nm. Meanwhile, under the radiation of 393 nm, the high internal quantum efficiency ( ∼ 78.71 %), excellent color purity ( ∼ 88.32 %) and robust thermal stability whose emission intensity at 140 °C could still reach ∼ 97.31 % could guarantee its potential application. When coating BaMgAl10O17: Eu2+, (Ba, Sr)2SiO4: Eu2+, and K7SrEu2B15O30 on a near-ultraviolet chip, the bright white light with a low correlated color temperature of 4211 K and CIE color coordinates of (0.3675, 0.3556) could be obtained. Taking the analytic results above, the non-concentration quenching K7SrY2B15O30: Eu3+ compound has great potential to act as a candidate for red-emitting phosphors in solid-state lighting field.

Towards high performance cyan phosphor by replacing F− with Cl− in Ba3Ca2(PO4)3(F/Cl): Eu2+

Currently, phosphor-converted white light-emitting diodes (pc-wLEDs) for solid-state lighting are mainly composed of blue or near-ultraviolet (n-UV) chips combined with phosphors. In the emission spectra of these pc-wLEDs, there always exists a missing valley in cyan region (from 470 to 510 nm). In order to achieve full-spectrum lighting, it is a challenging task to develop a cyan phosphor of high performance. In this work, a series of phosphors Ba2.97Ca2(PO4)3F1-xClx: 3%Eu2+ (x = 0-1) with apatite structure were synthesized and investigated. As Cl− replacing F−, the emission spectra of those phosphors present obvious blue-shift at 365 nm excitation. The obtained cyan phosphor Ba2.97Ca2(PO4)3Cl: 3%Eu2+ has higher quantum efficiency than the prototypical green phosphor Ba2.97Ca2(PO4)3F: 3%Eu2+ due to the smaller Stokes shift. As F− is replaced by Cl−, the band gap of the materials increases, which effectively reduces the probability of thermal ionization, thereby improving the thermal stability of luminescence (the integrated emission intensity of Ba2.97Ca2(PO4)3Cl: 3%Eu2+ at 150 °C can still maintain 81.2% of that at room temperature). The wLED fabricated has a high color rendering index and suitable correlated color temperature. This work develops a cyan phosphor with excellent performance, and it also can be as an important guidance for discovering novel excellent phosphors by the strategy of anionic substitution in the future.

Enhanced cyan emission via competitive site occupancy engineering in Sr2SiO4:Eu2+ phosphor for achieving full-spectrum LED lighting

Highly efficient containing cyan-emitting phosphors are used to bridge the cyan cavity for near ultraviolet (NUV) light-emitting diodes (LEDs) to obtain high-quality full-spectrum white lighting. In this work, a series of Sr2-xNaxSi1-xNbxO4:Eu2+ (x = 0–0.25) (SNSNO:Eu2+) solid solution phosphors were prepared by a solid-state reaction method. The bright SNSNO:Eu2+ phosphors were proceeded to fill the cyan gap. Such a cosubstitution of Na + -Nb5+ ion pair improves the cyan sub-band emission peaking at around 500 nm owing to the competitive site occupancy of Eu2+ on the Sr2+ site. Notably, codoping Na+-Nb5+ ion pairs into the host can realize a tuning of spectrum of SNSNO:Eu2+ from yellow-green to cyan-green region by crystallographic site engineering. Finally, employing mixture of SNSNO:Eu2+ and commercial BAM:Eu2+ and CaAlSiN3:Eu2+ coated on a 365 nm NUV chip, a full spectrum wLED package with remarkable color rendering index (Ra = 95.1) and low CCT = 3167 K was generated. The results indicate that the SNSNO:Eu2+ phosphor is very significative on closing the cyan gap for full-spectrum white lighting.