White Light-emitting Phosphor Research Articles

Synthesis and luminescence properties of a novel narrow band green-emitting Na2MgAl10O17:Mn2+ phosphor for backlight display

An activator’s selective occupation of a host is of great significance for designing high-quality white light-emitting diodes (w-LEDs) phosphors, while achieving a full-spectrum single-phase white light emission phosphor is challenging. For developing high-performance and green-emitting phosphors with narrow bands used for backlight display, a series of Na2Mg1-xAl10O17:xMn2+ (NMAO:xMn2+) phosphors with high Mn2+ concentration were synthesized. The NMAO:0.65Mn2+ green phosphor exhibits an ultra-narrow band green emission with full width at half maximum (FWHM) about 27 nm and peak position at 513 nm when excited by the blue light with wavelength of 450 nm. The NMAO:0.65Mn2+ not only has a super narrow band which is narrower than β-SiAlON:Eu2+ (FWHM ∼ 55 nm) but also shows an exceptional thermal stability performance (77% peak intensity @423 K). A w-LED device was assembled with NMAO:0.65Mn2+, a blue GaInN chip and K2SiF6:Mn4+ phosphors, which represents a wide color-gamut of 112% National Television System Committee (NTSC) standard under the current of 50 mA. These results demonstrate the NMAO:0.65Mn2+ has potential superiority in application of backlight display.

A single-phase Ca2GdNbO6: Dy3+ white light-emitting phosphors for near-UV double-excited WLEDs application

The development of white light emitting diodes (WLEDs) prepared with tricolor phosphors is limited by issues such as reabsorption, difficulty in controlling sample proportions, low thermal stability, etc. This study synthesized a series of single-host Ca2GdNbO6:xDy3+ (CGNO:xDy3+) phosphors using High-temperature Solid-state Reaction. Then the structure characteristics, luminescence, thermal stability, and morphology were analyzed in detail. The results showed that all the samples, emitted white light superposed by the blue at 483 nm and the yellow light at 575 nm under near-ultraviolet excitation, exhibit good quantum yield, excellent optical properties, and good moisture resistance. Besides, the CIE chromaticity coordinates (CIE) and luminous pictures of CGNO:xDy3+ phosphors both at 352 nm and 389 nm were investigated. Then, the properties of LED devices obtained by coating the aforementioned phosphors on 365 nm and 395 nm chips were characterized. The research confirmed that CGNO:xDy3+ are potential single-host white light phosphors in the field of lighting.

White light-emitting calcium tungstate microspheres synthesized via co-precipitation at room temperature and application to UV-LED chip

Crystalline CaWO4 was synthesized by a co-precipitation method at room temperature. XRD peak at a position like that in the reference pattern, and the signal was detected from the (112) plane. Raman signals suggested the presence of symmetrical vibrations of the WO4 bond. The absorption was observed in the UV region, and the bandgap calculated from the Tauc plot was 4.47 eV. When the sample was excited at 230 nm, blue emission with a peak at 430 nm was observed. Crystalline CaWO4 was doped with Dy3+ ions to synthesize a white light-emitting phosphor. The addition of Dy3+ ions altered the crystal structure and shifted the Raman signals slightly. The sample was excited at 230 nm, both 430 nm and 575 nm emissions were observed, and the intensity of the 575 nm emission increased with increasing Dy3+ concentration. The CaWO4:0.1Dy3+ sample showed the highest luminescence intensity, and excessive doping decreased the luminescence intensity owing to concentration quenching. The photoluminescence decay lifetime initially increased with increasing Dy3+ concentration but decreased at concentrations greater than 0.1 mol% because of concentration quenching. The synthesized white light emitting CaWO4:Dy3+ powder was mixed with PDMS to form a flexible composite. The composite could be easily bent with a finger and emitted white light when applied on a UV-LED chip.

Enhancement of color rendering index of stable lead-free perovskite WLEDs through incorporating green carbon dots

In this work, the carbon quantum dots@Cs2NaInCl6 (CDs@CNC) composites are presented by a facile solution synthesis. The obtained CDs@CNC composites maintain the octahedral morphology of original CNC host and the characteristic functional groups of original CDs. As a result, the rare-earth-free CDs@CNC composites exhibit green light emission with good stability for UV irradiation, heat, and humidity. In addition, CDs were combined with ion-doped CNC to obtain multicolor phosphor and the corresponding white light emitting diode (WLED) devices were fabricated by coating composites on commercial UV chips. The color render index (CRI) of WLEDs increases significantly from 66.24 to 90.95 while the cold-warm white fluorescence can be flexibly tuned by the change of excitation wavelength. The combination of CDs and double perovskites provide a new route to design white light emission phosphors, which could lead to the fabrication of next generation high-quality lighting devices.

Effects of La3+ Ion Doping Concentration on the Crystal Structure and Photoluminescence Properties of Y0.998Pr0.002InGe2O7 Single-phased White Light-emitting Phosphor

Effects of La3+ Ion Doping Concentration on the Crystal Structure and Photoluminescence Properties of Y0.998Pr0.002InGe2O7 Single-phased White Light-emitting Phosphor

Effect of oxygen vacancy on photoluminescence properties of Dy3+ doped K2BaCa(PO4)2 phosphor and remote luminescence multi-layer for white light

Dy3+ ions singly-doped phosphors, emerging as single-component white light-emitting phosphors, have been regarded as a promising candidate for white light generation under ultraviolet (UV) or near-ultraviolet (NUV) excitation. Here, a series of Dy3+ doped K2BaCa(PO4)2 phosphors with single phase was successfully synthesized by solid-state reaction method. Under NUV excitation, K2BaCa(PO4)2: Dy3+ phosphors exhibits the desire blue emission at 490 nm and yellow emission at 580 nm, attributed to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions, respectively. Interestingly, the broad emission peak centered at 458 nm can also be found and assigned to the oxygen vacancy in K2BaCa(PO4)2 host lattice. Significantly, the emission intensity of the phosphor is greatly enhanced to 4.1 times higher than that of the sample without oxygen vacancy due to the energy transfer from oxygen vacancy to Dy3+ ions. K2BaCa(PO4)2: 0.03Dy3+ phosphor with high quantum yield of 76.9% exhibits good thermal stability with the relative emission intensity of 95.7% and 88.6% at 323 K and 373 K, respectively. Subsequently, the white light with correlated color temperature (CCT) of 4521 K and color rendering index (CRI) of 79 can be achieved for the optimized K2BaCa(PO4)2: 0.03Dy3+ phosphor packaged with NUV LED chip (365 nm). Further, the remote luminescence multi-layer based on K2BaCa(PO4)2: 0.03Dy3+ phosphors is fabricated on glass substrate by screen printing technology and exhibit better heat dissipation performance than that of the conventional NUV LEDs, which can be a promising candidate of single-component phosphors for the manufacture of white LEDs with adjustable remote luminescent layers.

Anionic Regulation toward Bi3+ Selective Occupation for Full-Spectrum White Light Emission.

An activator's selective occupation of a host is of great significance for designing high-quality white light-emitting diode phosphors, while achieving a full-spectrum single-phase white light emission phosphor is challenging. In this study, a boron phosphate solid-solution Na2Y2(BO3)2-x(PO4)xO:0.005 Bi3+ (NYB2-xPxO:0.005 Bi3+) white phosphor was designed by selectively occupying Bi3+ activators in the mixed anionic groups. The substitutes of the anionic unit (BO3)3- by the (PO4)3- unit are supposed to force part of the Bi3+ ion to enter the Na lattice site, which produces an intense orange-red emission peaked at 590 nm. In parallel, spectral tuning from blue to white light and an internal quantum efficiency of 56.42% was obtained, and the thermal stabile luminescence intensity remains at 94.2% of the initial intensity after four heating-cooling cycles from 30 to 210 °C (luminescent intensity is 83.6% of room temperature (RT) at 150 °C, with excellent thermal stability and recovery performance). Finally, an excellent color rendering index (Ra = 90.8 and R9 = 85) was demonstrated for white light-emitting diode devices using only an NYB1.5P0.5O:0.005 Bi3+ phosphor and a near-ultraviolet (n-UV) 365 nm LED chip. This work delves into the different selective occupancy of Bi3+ ions and explores a new avenue for the design of phosphors for full-spectrum white light emission.

UV-excited single-component white phosphor of Lu2WO6 with broad-band emission for pc-WLED.

Obtaining white light from a single-component phosphor is still a significant challenge due to the complex energy transfer between multiple luminescent centers. Herein, white light emission is obtained in a single-component lutetium tungstate without any doping elements. By tuning the pH values during the hydrothermal synthesis, the orthorhombic Lu2W3O12 transformed into monocline Lu6WO12 and rhombohedra Lu6WO12. Only the monoclinic Lu2WO6 phase emitted light, whereas the other two phases did not. The main reason was that the exciton binding energy of Lu2WO6 was larger than that of Lu2W3O12 and Lu6WO12. Except for the 480 nm intrinsic emission of Lu2WO6, new long-wavelength excitation and emission bands were observed with the center at 340 nm and 520 nm. Based on the first-principle calculation, this new photoluminescence band comes from the electron transition between the local states of oxygen vacancies and valence band. Owing to this new broad-band emission, the white light LED lamp is fabricated by combining Lu2WO6 phosphor synthesized at pH values of 4.5 and 6 and 365 nm LED chips. The CIE coordinates of the pc-WLEDs are (0.346, 0.359) and (0.380, 0.380), respectively, and both are located in the white light region. Our research demonstrated a facile way to obtain a single-component white light emission phosphor without any doping components for pc-WLED applications.

Single-component full-color emitting Ca6Y2Na2(PO4)6F2:Eu2+,Tb3+,Mn2+ phosphors with superior performance: color-tunable and energy transfer study.

Highly efficient single-component full-color emitting Ca6Y2Na2(PO4)6F2 (CYNPF):Eu2+,Tb3+,Mn2+ phosphors have been synthesized by a high-temperature solid-state reaction. Coupled with the Eu2+, Tb3+, and Mn2+ emission bands centered at 455 nm, 547 nm, and 580 nm, color-tunable white light can be generated. The energy transfer (ET) process from Eu2+ to Tb3+ and Mn2+ is attributed to the resonant dipole-dipole/dipole-dipole interaction mechanism with ultra-high ET efficiency (>90%). The emission color of the phosphors can be tuned from blue to yellowish green and orange with the corresponding CIE chromaticity coordinates of (0.1719, 0.1215), (0.2852, 0.4289), and (0.4752, 0.3903), respectively. Through controlling the concentration ratio of Tb3+ and Mn2+ ions, optimal white light emission can be obtained with CIE coordinates of (0.3381, 0.3353) excited at 365 nm, which is very close to the National Television Standards Committee white (0.330, 0.330). The thermal stability of the Eu2+, Tb3+, and Mn2+ codoped CYNPF phosphors has been investigated systematically. A single-component white LED (wLED) device has been fabricated by combining the CYNPF:Eu2+,Tb3+,Mn2+ phosphor with a 365 nm near-ultraviolet (n-UV) LED chip, which exhibits a high color rendering index (Ra = 80.2) along with a low color temperature of 5207 K and CIE coordinates of (0.3212, 0.3221). The results suggest that the phosphors can be used as a candidate material for single-component white phosphors for n-UV excited full-visible-spectrum wLEDs.

Optimizing the luminescence efficiency of an europium (Eu3+) doped SrY2O4 phosphor for flexible display and lighting applications.

This research paper reports the synthesis and luminescence study of an Eu3+ activated SrY2O4 phosphor prepared by a modified solid-state reaction method with varying concentrations of Eu3+ ions (0.1-2.5 mol%). X-ray diffraction (XRD) revealed the orthorhombic structure and Fourier transform infrared spectroscopy (FTIR) methods were used to analyse the produced phosphors. Photoluminescence emission and excitation spectra were recorded for varying concentrations of Eu3+ ions, and an optimum concentration of 2.0 mol% was found to produce the highest intensity. Under 254 nm excitation the emission peaks were found to be at 580 nm, 590 nm, 611 nm and 619 nm, corresponding to transitions at 5D0 → 7F0, 5D0 → 7F1, and 5D0 → 7F2 respectively. Because of Eu3+ inherent luminosity, these emission peaks indicate radiative transitions between excited states of ions, making them useful for developing white light-emitting phosphors for optoelectronic and flexible display applications. The 1931 CIE (x, y) chromaticity coordinates were calculated from the photoluminescence emission spectra and found to be near white light emission, indicating the potential application of the prepared phosphor for light emitting diodes (white component). TL glow curve analysis was also performed for various concentrations of doping ions and UV exposure times, and a single broad peak was observed at 187 °C. Using the computerised glow curve deconvolution (CGCD) method, kinetic parameters were computed.

Tuning the Red Emission to Instigate Intrinsic White-Light Emission in Single-Phase Phosphor with Excellent Color Rendering Index.

There is ever-growing interest to develop intrinsic white light emitting single-phase phosphors that have high CRI, devoid of bluish tinge, ease of synthesis and are scalable. Herein, manipulating vacuum pressure to instigate white light emission in Cu2+ -doped-ZnS phosphors is reported. The detailed X-ray diffraction and electron microscopy confirm the cubic phase of Cu2+ -doped-ZnS phosphor having agglomerated particles (∼130-150 nm). The incorporation of Cu2+ in the ZnS lattice is substantiated by the anti-Stokes shift of Raman peaks and shifting of XRD peaks to higher 2θ values. Upon increasing Cu2+ doping concentration, the resulted decrease in the FWHM of XRD peaks implies shrinkage of the ZnS lattice. Interestingly, by tailoring the excitation wavelength, the stoichiometry of dopant ion, and defect states by varying the vacuum pressure, the optimized ZSC-3 (3% Cu2+ -doped-ZnS) displays the origin of clear blue, green and red emission bands, consequently giving rise to white light emission (CIE values: 0.345:0398). The PLQY and average lifetime calculated for ZSC-3 are 5.98% and 1.5 ms, respectively. Such intense white light emission prompted to fabricate a prototype using a 310 nm UV LED. It exhibits high CRI (97) and warm CCT (4538 K), meeting highly desired values for a white light-emitting phosphor for different lighting and electroluminescence applications.

Novel NiO/ZnO/Fe2O3 white light-emitting phosphor: facile synthesis, color-tunable photoluminescence and robust photocatalytic activity

Novel NiO/ZnO/Fe2O3 white light-emitting phosphor: facile synthesis, color-tunable photoluminescence and robust photocatalytic activity

White luminescent calcium molybdate phosphor synthesized at room temperature via the Co-precipitation method used in a LED flexible composite

To synthesize a white light-emitting phosphor, Dy3+, a rare earth ion, was added to synthesize crystalline CaMoO4 at room temperature by co-precipitation. In the synthesized powder, the main peak of the (112) plane was clearly observed in the x-ray diffraction pattern, and it was observed that the lattice constant was changed by the addition of the Dy3+ ions. The synthesized phosphor showed a strong absorption in the ultraviolet region and both blue light emission from the host and yellow light emission by the Dy3+ ions and cold white light emission. A flexible composite was prepared by mixing the synthesized phosphor powder with a PDMS polymer. It showed white light emission when placed on a UV-LED with an applied voltage, suggesting that it can be used as an LED color filter.

Improvement in white light emission of Dy3+ doped CaMoO4 via Zn2+ co-doping

The research in developing a single ingredient phosphor for white-light emission is progressively increasing. It is well known that the 4F9/2 → 6H13/2 (yellow) and 4F9/2 → 6H15/2 (blue) transitions of Dy3+ ions give near-white light emission. The white light emission of Dy3+ ions can be enhanced via improving the crystallinity of the host phosphor via co-doping of transition metal ions. In this paper, we report a significant improvement in the white light emission of Dy3+ doped CaMoO4 by co-doping Zn2+ ions. The x-ray diffraction pattern confirms the tetragonal phase of pure and doped CaMoO4 phosphor. The peak broadening and a red-shift in the absorption peak are observed by UV–vis absorption analysis of Zn2+/Dy3+ doped CaMoO4. From Photoluminescence studies, we have observed that in Dy3+ doped CaMoO4, the 4% Dy3+ doped CaMoO4 exhibits maximum emission. The Zn2+ ions are co-doped to further increase the luminescence intensity of CaMoO4:4%Dy3+ and the maximum luminescence is obtained for 0.25% Zn2+ concentration. Two intense emission peaks centered at 484 nm and 574 nm related to transitions 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 of Dy3+ ion are observed for Dy3+ doped phosphor. The 4F9/2 → 6H13/2 transition is the forced electric dipole transition which is affected by its chemical environment. After Zn2+ co-doping, the 4F9/2 → 6H13/2 transition is affected due to a change in asymmetricity around the Dy3+ ions. The 0.25% co-doping of Zn2+ gives 34% enhancement in luminescence emission of 4% Dy3+ doped CaMoO4. As a result, the CIE coordinates of chromaticity diagram and the color purity of the 0.25% Zn2+ co-doped CaMoO4:4Dy3+ show improvement in the overall white light emission. We have shown that with Zn2+ co-doping, the non-radiative relaxations are reduced which results in improved white light emission of Dy3+ions.

IMPORTANCE OF THE COLOR TEMPERATURE IN COLD WHITE LIGHT EMISSION OF Ca2MgSi2O7: Dy3+ PHOSPHOR

A promising candidate of white light-emitting (Ca2MgSi2O7: Dy3+) phosphor was successfully synthesized via traditional high-temperature solid-state synthesis technique using boric acid (H3BO3) as a fuel. The synthesized material sample was characterized with the help of powder X-ray diffraction (PXRD), FT-IR (Fourier Transform Infra-red) Spectroscopy, FESEM (Field Emission Scanning Electron Microscopy) and PL (Photoluminescence) spectra. Using the Debye-Scherer formula and UDM method, the crystallite size and crystal lattice strain were evaluated, respectively. Photoluminescence (PL) properties (both excitation & emission spectra) for the prepared phosphor were systematically investigated in detail. Photoluminescence spectra were revealed that the strong transition of spectral emission lines centered at 484nm (blue), 578nm (yellow) and weak transition of spectral emission lines centered at 615nm (red) wavelength. These peaks were assigned to following transitions (4F9/2 → 6H15/2,13/2,11/2), which are responsible for the (f→f) transitions from the ground level (lower energy state) to excited level (higher energy state) in the 4f9electronic configuration of dopant [Dy3+] ions. CIE color chromaticity coordinates and Color Correlated Temperature (CCT) of synthesized Ca2MgSi2O7: Dy3+ phosphor sample is well suited for the generation of cold white light emission with a CIE coordinate value of (X = 0.31, Y = 0.32) and CCT value also calculated as 5167K. Here upon, it is highly applicable to be a novel hopeful phosphor for cold WLEDs.

Green anti-solvent processed white light emitting perovskite phosphors in one step

Despite the excellent properties of perovskite materials, the strict oxygen-free atmosphere, heating temperature and a large number of toxic solvents applied during preparation obstruct their more widespread applications. Using ethanol as a green anti-solvent to successfully prepare a series of copper-based perovskite micro-phosphors. They have a luminescence peak between 445 nm and 580 nm adjusted with halogen and the highest PLQY of 81.6%. Moreover, by simply adjusting the molar ratio of CsI to CuI, white-light emission phosphors can be synthesized in one step. It exhibits a Commission Internationale de L'Eclairage (CIE) chromaticity coordinates (0.35, 0.35) and a correlated color temperature (CCT) of 4798 K. After two months of storage, there is still 97.4% of the initial light intensity. This technology offers a green and straightforward method for producing perovskite phosphors.

Non-cytotoxic Dy3+ activated La10W22O81 nanophosphors for UV based cool white LEDs and anticancer applications

White-light-emitting La10W22O81 (LWO): xDy3+ (0.5 ≤ x ≤ 10 mol%) nanocrystalline phosphors were developed by a facile hydrothermal assisted solid-state reaction. X-ray diffraction (XRD) pattern indicated that the prepared samples adopted orthorhombic crystal structures. The agglomeration of uniform nanorods was identified from the FE-SEM analysis of the optimized LWO: 1.5 mol% Dy3+ nanocrystalline phosphors. Additionally, transmission electron microscope, scanning transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy were employed to explore the surface morphology, size, interplanar distance, and chemical composition with valence states of the LWO: 1.5 mol% Dy3+ phosphors, respectively. By exciting with 387 nm, the LWO: Dy3+ emission spectra showed two intense peaks at 476 nm (4F9/2→6H15/2) and 571 nm (4F9/2→6H13/2) and a shoulder peak at 659 nm (4F9/2→6H11/2). Optimum emission intensity was achieved for 1.5 mol% Dy3+ in the LWO host lattice. The luminescence quenching beyond 1.5 mol% Dy3+ is attributed to the dipole–dipole interactions when the Dy3+ (donor) and Dy3+ (acceptor) ions are at a critical distance of 58.53 Å. Photometric studies were conducted to evaluate the performance and practical applicability of the phosphors. The CIE chromaticity diagram suggests that the LWO: 1.5 mol% Dy3+ nanophosphor conspicuously exhibits cool white light. Therefore, this material could be a promising and potential white light-emitting nanocrystalline phosphor material for white light emitting diodes (LEDs) under near-UV excitation. In addition, the toxicity of the optimized nanophosphor in normal WI-38 lung fibroblast cells and MCF-7 breast cancer cells was examined. Surprisingly, LWO: 1.5 mol% Dy3+ nanophosphor was found to be non-cytotoxic to normal cells, but extremely toxic to cancer cells. Therefore, the nanophosphor materials can be considered potential candidates for biomedical applications, particularly for cancer treatment.

Tunable Dual Emission in Bi3+/Te4+-Doped Cs2HfCl6 Double Perovskites for White Light-Emitting Diode Applications.

Multicolor-emission-based single-phase white light derived from different luminescence centers is an effective way to manipulate the optical properties of halide perovskites. In this work, we developed a codoping strategy to incorporate Bi3+ and Te4+ emission centers into all-inorganic lead-free Cs2HfCl6 perovskite by a hydrothermal method. The as-prepared Bi3+/Te4+-doped Cs2HfCl6 microcrystals show bright blue (Bi3+), yellow (Te4+), and warm-white emissions (Bi3+/Te4+), respectively. The broad efficient dual emission in Bi3+/Te4+ co-doped Cs2HfCl6 is assigned to the typical 3P1 → 1S0 transition emission from Bi3+ originating from [BiHf + VCl] and self-trapped excitons (STEs) from Te4+. Moreover, the concentration-optimized Cs2HfCl6:Te4+ shows excellent antiwater stability and high photoluminescence quantum yield (PLQY) of ∼70%. Meanwhile, a white light-emitting diode (WLED) fabricated using Bi3+/Te4+ co-doped Cs2HfCl6 is close to warm white with a color rendering index (CRI) of 75.4, CIE color coordinate of (0.370, 0.393), and a correlated color temperature (CCT) of 4380 K. These results suggest that Bi3+/Te4+ co-doped all-inorganic lead-free Cs2HfCl6 is a potential single-phase white light-emitting phosphor candidate for solid-state lightings.

Luminescence properties and thermal stability of Dy3+/Eu3+co-doped single-component BaZn2(PO4)2 glass-ceramic phosphors

Highly thermally stable BaZn2(PO4)2: Dy3+/Eu3+ glass-ceramic (GC) phosphors were synthesized using a high-temperature solid-state reaction and controlled-temperature pre-crystallization method. It is found that Dy3+-doped BaZn2(PO4)2 GC phosphors produce cold white light emission at 484 nm and 575 nm under 350 nm excitation with the optimal Dy3+ doping concentration of 0.25 mol%. The theoretical analysis indicates that the dipole-dipole interaction might be the origin of the concentration quenching mechanism of phosphor. The Eu3+-doped BaZn2(PO4)2 GC phosphors produce orange-red emission at 592, 616, 654 and 700 nm under 395 nm excitation. More than that, tunable white light emission can be achieved by optimize the co-doped concentration of Eu3+ on BaZn2(PO4)2: 0.25Dy3+ GC phosphor. The emission spectral intensity and luminescence decay curves from BaZn2(PO4)2: 0.25Dy3+/yEu3+ (range of y) GC phosphors show the energy transfer from Dy3+ to Eu3+ and the emission color can be tuned from cool white to warm white region with the color correlated temperatures (CCTs) reduction from 7299 K to 2520 K. The typical BaZn2(PO4)2: 0.25Dy3+/1Eu3+ GC phosphors have a high thermal stability with an activation energy of 0.30641 eV. Finally, the white LED devices were fabricated by coupling a 363 nm UV light-emitting diode chip with the BaZn2(PO4)2: 0.25Dy3+/yEu3+ GC phosphors. These results suggest that BaZn2(PO4)2: Dy3+/Eu3+ GC phosphors may be suitable candidates for single-component white light-emitting phosphors for application in UV-WLEDs.

Tendentious multiple sites occupation towards white light emission in single-phase Ba2(1-y/3)Ca(1-y/3)SryB2Si4O14:Eu2+ phosphors

Site preferences of Eu2+ ions on the Ba2+ sites and the Ca2+ sites were discovered in the mixed cation borosilicate Ba2CaB2Si4O14 (BCBSO). Eu2+ ions are more likely to locate on the Ba2+ sites over the Ca2+ sites according to the Density Functional Theory (DFT) calculation and the photoluminescence spectrum analysis. The emission band centered at 408 ​nm was confirmed to be generated from the Eu2+ ions located on the Ba2+ sites, while the emission band centered at 548 ​nm was considered to be generated from the Eu2+ ions on the Ca2+ sites. Dual sites occupation results in a collective emission band covering 380 ​nm–780 ​nm in BCBSO:Eu phosphors. By further doping with Sr2+ ions, crystal environment of the luminescence centers could be well modulated, resulting in the tunable emission from yellow to white under UV excitation. The photoluminescence quantum yield was significantly improved from 17.9% to 36.8%. Finally, a series of white LEDs with tunable CCT (from 5132 ​K to 3402 ​K) and high Ra (reach up to 89.6) were obtained using the Ba2(1-y/3)Ca(1-y/3)SryB2Si4O14:0.03Eu single-phase white light emission phosphors.