White Light-emitting Phosphor Research Articles

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.

Multiple energy transfer between CaNb2O6:Tb3+, Eu3+ for single-component white light-emitting phosphors

Multiple energy transfer between CaNb2O6:Tb3+, Eu3+ for single-component white light-emitting phosphors

White-light emission lead-free perovskite phosphor Cs2ZrCl6:Sb3+

Obtaining phosphors with white-light emission is a promising and economical approach for phosphor-conversion light emitting diodes (pc-LEDs), but traditional single-phase white light emission phosphors are inefficient. Here a white-light-emission phosphor was prepared via a co-precipitation method by doping Sb 3+ into lead-free and vacancy-ordered double perovskite Cs 2 ZrCl 6 . X-ray diffraction, X-ray photoelectron spectroscopy, and formation energy calculations confirmed that Sb 3+ ions replaced the Zr 4+ sites in the [ZrCl 6 ] 2− octahedron. The optical properties of Cs 2 ZrCl 6 :Sb 3+ were investigated and compared with those of blank Cs 2 ZrCl 6 . The origination of the emission bands was determined according to their fluorescence spectra and decay-time at an approximate temperature of 4 K Sb 3+ -doped Cs 2 ZrCl 6 exhibited white-light emission with double emission bands at 495 and 622 nm due to the 1 P 1 → 1 S 0 and 3 P 2, 1, 0 → 1 S 0 transitions of Sb 3+ , respectively. The intensity ratios of cyan light (495 nm) and the red light emission bands (622 nm) were tunable by adjusting the Sb 3+ concentration. The red component increased with increasing Sb 3+ concentration in the present experimental range. Moreover, 10% Sb 3+ -doped Cs 2 ZrCl 6 showed the strongest emission with a photoluminescence quantum yield of approximately 78% under excitation of 333-nm light White LED devices with different correlated color temperatures were achieved by combining 1% or 10% Sb 3+ -doped Cs 2 ZrCl 6 with a 310-nm ultraviolet chip, suggesting that the synthesized samples have potential applications in white-illumination LEDs. Single-phased white emitting phosphor Cs 2 ZrCl 6 : Sb 3+ and corresponding LEDs.

Layer-structure-suppressed concentration quenching of Dy3+ luminescence and the realization of a single phase white light-emitting phosphor cooperated with Tm3+

A special layered structure helps to suppress the concentration quenching to achieve high dysprosium–thulium co-doping single-phase white light.

White light emission phosphor modulation, nitrobenzene sensing property and barcode anti-counterfeiting via lanthanides post-functionalized metal-organic frameworks

Three isostructural lanthanide metal-organic frameworks (Ln-MOFs) [Ln2(L)3(H2O)5]n (1-Ln, Ln ​= ​Eu, Tb, Dy and Eu/Tb), and a transition MOF {[Cd(L)(H2O)2]·H2O}n (1-Cd) based on 1-(4-carboxyphenyl)-1H-pyrazole-3-carboxylic acid (H2L) ligand were obtained by solvothermal method. The white-light-emitting (WLE) material Eu3+/Tb3+@1-Cd with the CIE coordinate (0.33, 0.34) was successfully modulated by introducing Eu3+ and Tb3+ into the blue-emitting 1-Cd. The post-synthetic doping provides a facile and practical strategy for the development of WLE materials. Besides, the luminescence sensing experiments showed that 1-Ln can be used as an excellent probe for nitrobenzene detecting. And the multi-color barcode of 1-Ln showed great potential in commodity anti-counterfeiting and information security.

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

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

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

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

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

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

Introduction of Molybdenum into the lattice of single-host CaZrO3: Dy3+/Eu3+ to enhance luminescence intensity of the phosphor for white light emission

In the present study, we successfully prepared single-host CaZrO3 codoped Dy3+/Eu3+/Mo6+ for white light emission by employing solid state reaction method. Molybdenum was introduced into the lattice to enhance luminescence intensity of the phosphor materials. The luminescence properties of all the prepared samples were investigated under UV-lamp. The XRD results confirmed the formation of orthorhombic phase CaZrO3. The SEM photographs realized that the prepared phosphor materials have a tendency to form agglomerates. Similarly, the EDS test was carried out to confirm the absence of any extraneous impurities. Mo6+ was incorporated into Dy3+ and Eu3+ singly doped, and also in Dy3+/Eu3+ codoped CaZrO3. Furthermore, we also studied the energy transfer between Mo6+ → Dy3+ and Mo6+ → Eu3+ in detail. The increasing dopant concentration of Mo6+ (Mo = 0.1, 0.5, 0.8, 1.0, 2.0) mol% under 350 nm excitation source, the CIE color coordinates shift towards the vicinity of white light, which makes this material prominent for the fabrication of white light emitting diodes (WLEDs).

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

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

Photoluminescence and energy transfer of efficient and thermally stable white-emitting Ca9La(PO4)7:Ce3+, Tb3+, Mn2+ phosphors

The development of novel single-component white-emitting phosphors with high thermal stability is essential for improving the illumination quality of white light-emitting diodes. In this work, we synthesized a series of Ce3+, Tb3+, Mn2+ single- and multiple-doped Ca9La(PO4)7 (CLPO) phosphors with β-Ca3(PO4)2-type structure by the simple high-temperature solid-state reaction. The crystallization behavior, crystal structure, surface morphology, photoluminescence performance, decay lifetime and thermal stability were systematically investigated. The PL spectra and decay curves have evidenced the efficient energy transfer from Ce3+ to Tb3+ and from Ce3+ to Mn2+ in the CLPO host, and corresponding energy transfer efficiency reaches 41.8% and 54.1%, respectively. The energy transfer process of Ce3+→Tb3+ and Ce3+→Mn2+ can be deduced to the resonant type via dipole-dipole and dipole-quadrupole interaction mechanism, and corresponding critical distance were determined to be 12.23 and 14.4 Å, respectively. Based on the efficient energy transfer, the white light emission can be successfully achieved in the single-component CLPO:0.15Ce3+, 0.10Tb3+, 0.04Mn2+ phosphor, which owns CIE chromaticity coordinates of (0.3245, 0.3347), CCT of 5878 K, internal and external quantum efficiency of 84.51% and 69.32%. Especially, compared with the emission intensity at 25 °C, it still remains 98.5% at 150 °C and 92.0% at 300 °C. Based on these results, the single-component white light emission phosphor CLPO:0.15Ce3+, 0.10Tb3+, 0.04Mn2+ is a potential candidate for UV-converted white LEDs.

Modern aspects of strategies for developing single-phase broadly tunable white light-emitting phosphors

The latest developments of single-phase white-light-emitting Ba9Lu2Si6O24(BLSO) silicate phosphors are presented. The emerging approaches to crystal-site engineering and the energy transfer mechanisms are discussed at great length.

Dy3+-doped LaInO3: a host-sensitized white luminescence phosphor with exciton-mediated energy transfer

A new mechanism of host-sensitized energy transfer was proposed to describe the luminescence dynamics behaviors between excitons and activators. This provides a promising path to explore single-phase white light-emitting phosphors.

A novel Dy3+-activated single-phase white light-emitting phosphor for solid-state lighting

The doping of Dy3+ in the SCB host is capable of producing blue, yellow and red emissions, and therefore, SCB:Dy3+ can serve as a single-phase white-light-emitting phosphor for solid state lighting.

A Comparatitive Study on Photoluminescence and Color Propertites between Amorphous and Crystalline Organic-Inorganic Hybrids As Single-Phased and Single-Phased Phosphor for White-Light Emission

We have examined some zirconium organic complexes via an array of characterization techniques, showing that they are amorphous single-phased and single-doped phosphors for white-light emission. Combined with thermogravimetric measurement coupled with a quadrupole mass spectrometer, and inductively coupled plasma-atomic emission spectroscopy and/or mass spectrometry measurements, the detailed infrared spectroscopy analyses indicate that the amorphous phosphor is a sulphur species-doped zirconium oxy-hydroxyl acetate complex.The phosphors exhibit the photoluminescence and color properties comparable to or better than those of the crystalline metal-organic frameworks (MOFs). or organic-inorganic hybrid semiconductors for white-light emission.

Sm3+-doped strontium barium borate phosphor for white light emission: Spectroscopic properties and Judd–Ofelt analysis

This study aims to explore the spectroscopic properties of a Sr1.0Ba2.0B6O12:0.5Sm3+ phosphor synthesized using the solid-state reaction method. The morphology and elemental composition of the phosphor were determined using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. Phase changes and crystallite phases in the phosphor were studied using differential-scanning calorimetry and X-ray diffraction, respectively. Raman and Fourier-transform infrared spectra were used to identify the molecular vibrations in the phosphor. The energy bandgap and bonding nature of the phosphor were analyzed using the absorption spectrum. The nephelauxetic ratios determined from the absorption peaks revealed the presence of both ionic and covalent bonding in the phosphor. Judd–Ofelt parameters, along with radiative properties of the phosphor, were evaluated using the peaks in the absorption spectrum. Colorimetric analysis using the photoluminescence spectrum showed that the Sr1.0Ba2.0B6O12:0.5Sm3+ phosphor emits a cool-white light. The higher values of the spectroscopic quality factor, stimulated-emission cross-section, quantum efficiency, and the white-light emission of the phosphor suggest that Sr1.0Ba2.0B6O12:0.5Sm3+ is useful for display and lighting applications.

Controllable luminescence and efficient energy transfer investigation of a novel white light emission phosphor Ca19Na2Mg(PO4)14: Dy3+, Tm3+ with high thermal stability

White light emission phosphors are widely researched for application in lighting and display fields. However, the poor thermal stability is a real problem for the known single-phased white phosphors, which limits their further application. In this paper, Ca19Na2Mg(PO4)14: xDy3+, yTm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01) phosphors with adjustable emission and good thermal stability are synthesized. The X-ray diffraction and X-ray energy dispersive spectrometer measurement distinctly confirm the successful synthesis of CNMP: xDy3+, yTm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01). The photoluminescence results reveal that CNMP: Dy3+ shows characteristic excitation peaks in the range of 350–450 nm, and mainly exhibits strong yellow emission around 575 nm ascribed to the 4F9/2-6H13/2 transitions of Dy3+. To compensate the deficiency of blue light emission of CNMP: Dy3+, the trivalent Tm3+ ion is co-doped owing to its characteristic blue emission at 450 nm due to its 1D2-3F4 transitions. Therefore, the emission of CNMP: Dy3+, Tm3+ can be tuned from blue light region with CIE coordinates of (0.1649, 0.0387) to white light region with CIE coordinates of (0.3001, 0.3003) and finally move to yellow light region with CIE coordinates of (0.3732, 0.4493) through adjusting the doping ratio of Dy3+/Tm3+. The energy transfer efficiency and the energy transfer mechanism from Tm3+ to Dy3+ are further investigated. Moreover, CNMP: Dy3+, Tm3+ exhibites a high thermal stability and the emission intensity still keeps 84% of the initial intensity of Dy3+ at 230 °C. These outstanding properties show that Ca19Na2Mg(PO4)14: Dy3+, Tm3+ have great advantages and potentiality for applying in solid state lighting.

Novel thermally robust warm white light emitting phosphor Ca18Li3Y(PO4)14:Dy3+: Synthesis, crystal structure and luminescence property investigation

To explore novel single phase warm white light emitting phosphor, a series of phosphate phosphors Ca18Li3Y(PO4)14:Dy3+ were prepared. The phase purity, crystal structure, morphology and element component were confirmed by XRD Rietveld structure refinement, SEM and EDS analysis. The luminescence process of Ca18Li3Y(PO4)14:Dy3+ were systematically studied by photoluminescence spectroscopy and decay curves. The results indicated Ca18Li3Y(PO4)14:Dy3+ phosphors had strong excitation from 300 nm to 420 nm. Under the excitation of 350 nm, warm white light emission was achieved with the CIE color coordinates of (0.399, 0.448) and low CCT of ~ 3992 K. The concentration quenching mechanism and quantum efficiency of Dy3+ in Ca18Li3Y(PO4)14:Dy3+ were calculated and discussed in detail. The thermal quenching behavior revealed that Ca18Li3Y(PO4)14:Dy3+ had excellent thermal stability with stable color rendition. The thermal activation energy was finally calculated. All the results indicated the potential application of Ca18Li3Y(PO4)14:Dy3+ white light emission phosphor to be used in solid state lighting.

A novel single-phase Na3.6Y1.8(PO4)3:Bi3+,Eu3+ phosphor for tunable and white light emission

A new type of Bi3+,Eu3+ single- and co-doped Na3.6Y1.8(PO4)3 phosphate phosphors were manufactured using conventional high-temperature solid-state reaction technique to explore their application for solid-state lighting. The crystal structure, luminescent properties, luminescent mechanism and quantum efficiency were thoroughly explored. Results show that there are two crystallization sites for Bi3+ and Eu3+ ions. Upon the excitation of 342 and 373 nm, Bi3+ single-doped phosphors exhibit green and blue emission, derived from the 3P1 to 1S0 transition of Bi3+ located in different occupancy sites. Thanks to radiative energy transfer process from Bi3+ to Eu3+, adjustable emission could be acquired by altering Eu3+ content in co-doped phosphors. Pure white-light emission with quantum efficiency value of 22.9% can be realized in Na3.6Y1.8(PO4)3:0.01Bi3+,0.1Eu3+ sample and the integrated intensity of white light emission at 417 K remains 85% of that at room temperature. Our results indicate that Na3.6Y1.8(PO4)3:Bi3+,Eu3+ phosphors have feasible application in high-power ultraviolet driven solid-state lighting.

Improving thermal stability of novel single-component white-light emitting phosphor Ca8MgLu(PO4)7:Tm3+, Dy3+ by back-energy-transfer

The light degradation of WLED devices after long-time use has been proved to be mainly caused by thermal quenching of phosphors, therefore, the design of single-component white-light emitting phosphors with high thermal stability remains a huge challenge. A novel single-phase white light-emitting phosphor Ca8MgLu(PO4)7:Tm3+,Dy3+ was designed and prepared in this work. The photoluminescent results show that white light emission from the phosphor can be achieved by controlling the ratio of Tm3+ and Dy3+ to adjust the relative intensity of the emission at 451 nm of Tm3+ and the emissions at 488, 571 and 660 nm of Dy3+. The luminescence decay results reveal that there is energy transfer from Tm3+ to Dy3+ in Ca8MgLu(PO4)7:Tm3+,Dy3+ and the efficiency of energy transfer between the two dopants reaches as much as 55%. Temperature-dependent luminescent analyses suggest the highly stable emission of Ca8MgLu0.76(PO4)7:0.12Tm3+,0.12Dy3+ as the integrated emission intensity of the phosphor at 475 K reduces only about 13% of that at room temperature, which is due to the back-energy-transfer from highly doped Dy3+ to Tm3+ that compensates the luminescence energy. This single-phase white-light emitting phosphor exhibits superior color and luminescence stability and thus may find a potential application in WLEDs.