Search

This study focuses on the facile combustion synthesis of highly luminescent Y2O3:Sm3+, Gd3+ nanophosphors, bringing down the thermal budget to a minimum of 500 K. When Sm3+ ions are doped in the Y2O3 cubic crystal system of bandgap 5.6 eV and studied under a down-conversion excitation of 260 nm, the emission spectra offered an intense vermilion color at 608 nm due to the 4G5/2 → 6H7/2 transition within the Sm3+ ions. The Y2O3:2wt%Sm3+ matrix is co-doped with 3wt%Gd3+, highlighting 100% pure vermilion emission 4.21 times higher than doped samples, which is a perfect choice for domestic lightening owing to better eye compatibility. Further, post-annealing is performed to improve the structural parameters and luminescence properties, creating sufficient alterations in the crystal lattice. It is professed that Y2O3:Sm3+, Gd3+ nanophosphors can be effectively used in optoelectronic devices, owing to their enhanced crystallinity and photoluminescence properties resulting from the Gd3+ → Sm3+ energy transfer efficiency of 75.15%. [ABSTRACT FROM AUTHOR]

A series of Ca 3 Y 2 Ge 3 O 12 : xTb3+, yEu3+ (CYGO) phosphors were prepared by the high-temperature solid-phase reaction method. The physical phases, luminescence properties, and energy transfer of the samples were systematically analysed and discussed by XRD and fluorescence spectroscopy. Under the excitation at 377 nm, the CYGO: xTb3+ phosphor emits green light, and the concentration quenching point of Tb3+ ions is x = 0.24. The fluorescence intensity of Tb3+ ions decrease with the increase of the concentration of Eu3+ in CYGO: xTb3+, yEu3+ phosphors, the fluorescence intensity of Eu3+ ions increase rapidly, and the luminescence colour changes from green to red with the increasing of the concentration of Tb3+ at a certain concentration of Tb3+, the luminescence colour changes from green to red, confirm the existence of an energy transfer process between Tb3+ and Eu3+. The energy transfer mechanism is quadrupole-quadrupole interaction. The quantum yield is as high as 95.45%. Under the excitation of the UV-LED chip at 370 nm, the LED based on CYGO:0.24 Tb3+, 0.08Eu3+ phosphors have a R a of 86.7, low CCT of 4917 K and CIE coordinate of (0.3498,0.3789), so the CYGO: xTb3+, yEu3+ phosphors have a potential for application in the field of UV-near-UV white LEDs. has a certain application potential. [ABSTRACT FROM AUTHOR]

Eu3+,Dy3+ co‐doped Sr2LaZrO5.5‐based phosphors were prepared through a sol–gel method. Through characterization, it was found that the Sr2LaZrO5.5‐based fluorescent powder co‐doped with Eu3+ and Dy3+ had a cubic structure. At an excitation wavelength of 290 nm, the substrate Sr2LaZrO5.5 exhibited strong blue emission at 468 nm, and the Sr2LaZrO5.5:18%Eu3+ phosphor exhibited a strong red emission peak at 612 nm. When the doping amount of Dy3+ was 5, 8, 12, 15, or 18%, the Sr2LaZrO5.5:18%Eu3+ phosphor changed from an orange‐red light, to a warm white light, and to a cold white light. According to the emission spectra, the emission intensities of the substrates Sr2LaZrO5.5 and Sr2LaZrO5.5:Eu3+ decreased with increasing Dy3+ concentration, confirming the energy transfer between the host Sr2LaZrO5.5‐Eu3+,Dy3+, and resulting in a lower CCT value, with significantly improved white light emission. [ABSTRACT FROM AUTHOR]

In this investigation, the photoluminescence properties, energy transfer phenomenon of BaY 2 ZnO 5 :Sm3+/Eu3+ doped/co-doped phosphor are reported and synthesized by high temperature solid state reaction method. The crystal structure, micromorphology, optical diffuse reflectance and photoluminescence properties of the samples were studied. The results show that concentration quenching phenomenon is found. With the increase of Eu3+ ion concentration, the emission peaks of Sm3+ gradually decrease, indicating that energy transfer between Sm3+ and Eu3+. The optimal concentrations are 0.05 mol and 0.2 mol for single doping Sm3+ and Eu3+, respectively. The energy transfer efficiency is calculated to be 78.47–95.19 %. The BaY 2 ZnO 5 phosphors have potential application value in the fields of white light LEDs and anti-counterfeiting. • The BaY 2 ZnO 5 :RE3+ (RE=Sm3+, Eu3+) phosphors have been synthesized. • The phosphors can be effectively excited by near ultraviolet or blue light. • The phosphors exhibit good optical properties. [ABSTRACT FROM AUTHOR]

The construction of high luminous quality (quantum efficiency, color purity, etc.) cyan emission phosphor has a milestone significance for improving lighting quality and expanding the application fields of phosphor. Here, a kind of cyan emission phosphor Ca 8 ZnY(PO 4) 7 :Eu2+ is prepared by using β-Ca 3 (PO 4) 2 as prototype according to structural engineering strategy. Through the activation of Eu2+ and the energy transfer from Eu2+ to Mn2+ in Ca 8 ZnY(PO 4) 7 , the applications of WLEDs and optical anti-counterfeiting are realized. Excited at 320 nm, the central peak of Ca 8 ZnY(PO 4) 7 :Eu2+ spectra is at around 490 nm, the full width at half maximum is ∼80 nm, and the internal quantum efficiency is up to 51.52 %. Based on Rietveld refinement of XRD data and Gaussian fitting, three luminescence centers are identified. The maximum energy transfer efficiency from Eu2+ to Mn2+ is 51.05 %, and the energy transfer type is also determined by calculation. With the regulation of Mn2+ concentration, the luminous color of the series phosphor transitions from cyan to white and finally to red. The prepared phosphors possess certain thermal stability, which can not only compensate the cyan gap in the commercial phosphor combination LEDs, but also be used as phosphor raw material for single-phase WLEDs. In addition, the optical anti-counterfeiting films prepared by mixing the prepared phosphors with polyvinyl alcohol have the advantages of transparency, flexibility and rapid response, exhibiting great potential applications in the fields of optical anti-counterfeiting, information encryption and even criminal investigation. In summary, the prepared phosphors have the potential of multi-functional application in the field of high-quality lighting and anti-counterfeiting. [Display omitted] • A novel cyan light emission phosphor Ca 8 ZnY(PO 4) 7 :Eu2+ was prepared. • Ca 8 ZnY(PO 4) 7 :Eu2+ phosphor has a high cyan color purity. • Ca 8 ZnY(PO 4) 7 :Eu2+ phosphor has high quantum efficiency. • With the participation of Ca 8 ZnY(PO 4) 7 :Eu2+, the Ra of WLED can reach 96.8, and the CCT can reach 4461 K. • The application demonstration in optical anti-counterfeiting, information encryption and criminal investigation is provided. [ABSTRACT FROM AUTHOR]

KSrGd(PO 4) 2 :Ln3+ (Ln = Ce, Sm, Eu, Tb, Dy, Dy/Eu, Yb/Ho, Yb/Er, Yb/Tm) phosphors were synthesized by high temperature solid state method. Doping the KSrGd(PO 4) 2 matrix with 5%Dy3+ ions resulted in white light emission under 345 nm excitation. The calculated color temperature (CCT) of this white light is 5523 K, indicating as positive white light. It was found that the luminous intensity of the obtained KSrGd(PO 4) 2 :5%Dy3+ at 200 °C was 76.80 % of that at room temperature, showing good thermal stability as well as possibility of application in white LED. Under the excitation at 392 nm, the fluorescence quantum yield of KSrGd(PO 4) 2 :10%Eu3+ is 79.92 %. Energy transfer between Dy3+ and Eu3+ is observed in KSrGd(PO 4) 2 :Dy3+/Eu3+ samples, with identified mechanism as the quadrupole-quadrupole interaction. Tunable luminescence ranging from white to yellow then to orange-red is achieved by adjusting the doping concentration of Eu3+ in KSrGd(PO 4) 2 :5%Dy3+, x%Eu3+. Under the excitation of 980 nm near-infrared light, the prepared KSrGd(PO 4) 2 :Yb3+/Ho3+, KSrGd(PO 4) 2 :Yb3+/Er3+ and KSrGd(PO 4) 2 :Yb3+/Tm3+ samples showed up-conversion emissions of red, yellow and blue, respectively, with two-photon processes. In KSrGd(PO 4) 2 matrix, multi-color and multi-security marks were successfully prepared by utilizing up/down conversion luminescence characteristics, which obtained good anti-counterfeiting effect and improved anti-counterfeiting security. Therefore, the obtained KSrGd(PO 4) 2 : Ln3+ phosphors exhibit promising application prospects in the fields of WLED and multiple anti-counterfeiting. • The luminous intensity of the obtained KSGP: 5%Dy3+at 200 °C was close to that at room temperature, showing excellent thermal stability. And the activation energy value of KSGP:5%Dy3+ sample is 0.245 eV. • Doping the KSrGd(PO 4) 2 matrix with 5%Dy3+ ions resulted in white light emission under 345 nm excitation, indicating as positive white light. • The obtained KSGP:10%Eu3+ red phosphor exhibits a fluorescence quantum yield as high as 79.92 %. • The photoluminescent multi-color anti-counterfeiting materials with high security were prepared by using the polychromatic luminescence characteristics of the synthesized KSGP: Ln3+ phosphors. [ABSTRACT FROM AUTHOR]

[Display omitted] Doping Mn2+ into CsPbCl 3 nanocrystals (NCs) yields strong orange emission, while the related emission in Mn2+ doped CsPbBr 3 NCs is impaired seriously. This is mainly ascribed to back energy transfer from the Mn2+ dopant to the host. Doping Mn2+ into perovskites with multiple-quantum-well (MQW) structures may address this issue, where the energy funnels ensure a rapid energy transfer process, and thus resulting in a high photoluminescence quantum yield (PLQY). Here, we have developed an Ag+ assisted Mn2+ doping method in which Mn2+ can be easily doped into Br-based MQW perovskites. In this MQW perovskites, both nanoplatelets (NPLs) and NCs were formed simultaneously, where efficient energy transfer occurred from the NPLs with a higher energy bandgap to the NCs with a smaller energy bandgap, and then to the Mn2+ dopants. White lighting solution with a PLQY up to 98% has been acquired by altering the experimental parameters, such as reaction time and the Pb-to-Mn feed ratio. The successful doping of Mn2+ into CsPbBr 3 host has great significance and shows promising application for next-generation white lighting. [ABSTRACT FROM AUTHOR]

Multi-color single-phase white emission Sr3B2SiO8:Tm3+/Dy3+/Eu3+ fluorescent powders were prepared by solid-state fritting method. The fluorescence performance of Tm3+, Dy3+ and Eu3+ ions single-activated Sr3B2SiO8 phosphors were investigated and they exhibit desirable behaviors in their characteristic emissions. Meanwhile, the energy required for migration from Tm3+ to Dy3+ and from Dy3+ to Eu3+ in co-doped fluorescent substance was determined by the aids of steady-state and transient-state photoluminescence spectra/decay measurements. The energy transmission process from Tm3+ to Dy3+and Dy3+ to Eu3+ has been explored to be a dipole–quadrupole interaction and a dipole–dipole interaction of the resonant type, respectively. More significantly, by tuning the molarity ratio of doping Dy3+/Eu3+ ions, multicolor emission from yellow to red shall be achieved in Sr3B2SiO8:Dy3+, Eu3+ phosphors for its potential adhibitions in solid-state lighting applications. The Sr3B2SiO8:Tm3+, Dy3+ samples can implement white light emission by the appropriate changeable doping molar quantity of Tm3+and Dy3+, applying potentially in white LEDs. The energy migrations between co-doped rare earth ions play a decisive role in these processes. [ABSTRACT FROM AUTHOR]

Phosphors with multiband emissions have unique applications in thermometers and white LED, which can be readily realized by energy transfer. In this work, the energy transfers from Ce3+ to Mn2+/Tb3+ have been successfully constructed to achieve multiband emission in the KBaLu(BO 3) 2 (KBLBO) phosphors. KBLBO:Ce3+ can be efficiently excited by the near-ultraviolet light and shows a broad emission band at 453 nm. On the basis of the energy transfer from the Ce3+ to Mn2+/Tb3+ ions, KBLBO:Ce3+,Mn2+/Tb3+ exhibits a multiband emission consists of blue and red bands/green bands. The KBLBO:0.02Ce3+,0.03Mn2+ phosphor can function as a ratiometric thermometer with high temperature sensing performance by taking use of the differences in the thermal quenching behavior between the Ce3+ and Mn2+ ions. Moreover, a single-phase white light emitting phosphor KBLBO:0.02Ce3+,0.03Mn2+,0.01 Tb3+ was obtained. Meanwhile, the as-prepared WLED device exhibits CRI of 87.1 and CCT of 5090 K. Our work not only reveals the multifunctionality of the new KBLBO phosphors, but also points out the design and utilization strategies of multiband emission phosphors based on energy transfer. [Display omitted] • A series of KBaLu(BO 3) 2 :Ce3+,Mn2+,Tb3+ phosphors with tunable multiband emissions were synthesized. • The KBaLu(BO 3) 2 :Ce3+,Mn2+ phosphor exhibits high temperature sensing performance when used as a ratiometric thermometer. • KBaLu(BO 3) 2 :Ce3+,Mn2+,Tb3+ phosphor can be used for single component near-UV WLED device. [ABSTRACT FROM AUTHOR]

Y 3 Al 5 O 12 :Ce3+/Mn2+/Si4+ phosphor ceramics were fabricated by solid state reaction. Red emission is obtained, which is attributed to the Mn2+:4T 1 →6A 1 spin-forbidden transition under the excitation of 450 nm via the efficient energy transfer from Ce3+ to Mn2+.The green emission (535 nm) originating from Ce3+ and the orange emission (587 nm) from Mn2+ ions were observed. Mn2+ ions are more inclined to occupy Al3+ octahedral sites and the Si4+ ions locate in the Al3+ tetrahedral sites and their co-doping is for charge compensation. The red emission component in Ce3+/Mn2+/Si4+ doping YAG phosphor ceramics is significant for obtaining warm white lighting upon increasing Mn2+ concentration under 450 nm excitation. White light emitting diodes were successfully constructed by combining the fabricated ceramics with the GaN blue chips. • Highlights. • YAG: Ce3+, Mn2+ phosphor ceramics were obtained by the solid-state reaction. • Efficient energy transfer from Ce3+ to Mn2+ is observed. • The emission color can be tuned from green to orange. [ABSTRACT FROM AUTHOR]

Several series of near-ultraviolet (n -UV) convertible white Ce/Tb/Sm-tridoped borate Sr 3 Y 2 B 4 O 12 (SYBO) via Ce → Tb → Sm energy transfer (ET) have been successfully obtained by solid-state reaction under reducing atmosphere. The reason why picks Ce/Tb/Sm ions is based on the facts that these lanthanide ions are all extensively used ions in inorganic phosphors and emitting typically in blue, green and red region, respectively, that could be easily mixed and regulated to obtain warm white light within a single phase matrix. The structure, determined from XRD and analysed based on the Rietveld method, shows Y and Sr have 8-fold and 10-, 9- and 8-fold coordination, respectively, and all dopants are more inclined to enter Y sites as compared with Sr sites due to different degrees of radius ratio and charge among the dopants, Y and Sr. The ET mechanism is detailed studied via photoluminescence and decay lifetimes, where the obvious spectral overlap of the PLE for Tb/Sm and PL of Ce with systematic relatively decrease and increase of PL peaks of Ce, Tb/Sm, respectively, clearly indicate the ET occurs. Further, according to spectral studies on codoped (Ce/Tb, Ce/Sm and Tb/Sm) and tridoped phosphors, the Tb acts actually as the ET bridge to better connect Ce and Sm due to ET directly from Ce to Sm is difficult to achieve. Finally, the near-ideal white light from optimal SYBO:Ce/Tb/Sm with color coordinates of (x = 0.328, y = 0.343) and R a = 86 was observed under n -UV excitation indicates this kind of phosphors could be potentially applied in solid-state lighting. Warm white LEDs based on the 'n-UV' + Ce/Tb/Sm tridoped SYBO borate phosphor via 'capping' packaging. [Display omitted] • All dopants are more inclined to enter Y sites determined from XRD and Rietveld method. • ET mechanism is studied via photoluminescence and decay lifetimes. • Tb acts as ET bridge to connect Ce and Sm via donor.→ intermediate → acceptor. • Warm white light via the ' n -UV LED + tridoped white emitting phosphor' is achieved. [ABSTRACT FROM AUTHOR]

Abstract A series of single-phase blue-to-red tunable-color emitting and excellent green-emission Sr 2 MgSi 2 O 7 :Bi3+, Sm3+/Tb3+ phosphors have been synthesized by high temperature solid state reaction. The crystal structure of Sr 2 MgSi 2 O 7 and the crystallographic sites of Bi3+, Sm3+ and Tb3+ ions in the host have been identified through the crystallographic data from Rietveld refinements. The luminescent properties of Sr 2 MgSi 2 O 7 :Bi3+/Sm3+/Tb3+ phosphors were investigated and the Bi3+, Sm3+ or Tb3+ single doped samples exhibit blue, orange-red and green emissions, originating from the 3P 1 →1S 0 transition of Bi3+, the 4G 5/2 to 6H J (J = 5/2, 7/2, 9/2) transitions of Sm3+ and the 5D 4 →7F J (J = 6, 5, 4, 3) multiplet transitions of Tb3+, respectively. Meanwhile, the energy migration from Bi3+ to Sm3+ and Tb3+ in co-doping samples was confirmed by emission/excitation spectra and luminescent decay behaviors. The mechanism of energy transfer from Bi3+ to Sm3+ has been demonstrated to be the resonant type via a dipole–dipole interaction and the critical distances between Bi3+ and Sm3+ were calculated to be 22.28 Å. Additionally, the temperature-dependent photoluminescence for as-prepared phosphors have been investigated in detail. The luminescence intensity of Sm3+ and Tb3+ ions can be sensitized to enhance by Bi3+ ion. The blue and orange-red colors can be tuned by adjusting the concentration ratio of Bi3+/Sm3+ base on the energy transfer from Bi3+ to Sm3+ ions, and the phosphors Sr 2 MgSi 2 O 7 :Bi3+, Tb3+ develop excellent green-emission properties, which indicate that the Sr 2 MgSi 2 O 7 :Bi3+, Sm3+/Tb3+ phosphors with tunable multicolor and green emissions may be of potential application in pc-white LEDs. Highlights • The Sr 2 MgSi 2 O 7 :Bi3+/Sm3+/Tb3+ are novel luminescent materials and the crystal structure has been investigated. • Energy transfer from Bi3+ to Sm3+/Tb3+ were investigated and the luminescence intensity of Sm3+ and Tb3+ ions is sensitized to enhance by Bi3+ ion. • The emission color of Sr 2 MgSi 2 O 7 :Bi3+/Sm3+/Tb3+ can be adjusted from blue to orange-red to green. [ABSTRACT FROM AUTHOR]

Samarium (III) doped fluorapatite phosphors La 6- x Ba 4 (SiO 4 ) 6 F 2 : x Sm 3+ (LBSF: Sm 3+ ) were synthesized for the first time, via the conventional high-temperature solid-state method in the air atmosphere. The samples were measured by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy, i.e. emission and excitation spectra, as well as luminescence decay curves. The as-prepared samples can be excited in the range from 300–500 nm, centered at 404 nm. Photoluminescence measurements showed the emission spectra are composed of four sharp peaks characteristic of Sm 3+ ions, at about 565, 603, 650 and 711 nm. The critical concentration for quenching of Sm 3+ ions in the LBSF matrix is about 0.12 mol. According to the Dexter's theory, the mechanism of energy transfer between Sm 3+ ions was considered to be dipole-quadrupole (d-q) interactions, with the critical distance calculated by the concentration quenching method to 9.89 Å. Moreover, the temperature-dependent emission spectra showed that the as-prepared phosphors have good thermal stability, with an activation energy of about 0.161 eV. Finally, according to the CIE coordination, the phosphor exhibited reddish-orange emission. Thanks to the mentioned favorable structural and optical properties, the Sm 3+ -doped La 6 Ba 4 (SiO 4 ) 6 F 2 phosphors have a potential application character, for the near ultraviolet white light emitting diodes. [ABSTRACT FROM AUTHOR]

Ce/Pr -doped YAG (Ce:Pr:YAG) transparent ceramics are fabricated by the vacuum sintering. The crystal structure and morphology, the energy transfer between Ce 3+ and Pr 3+ , and luminescence properties are measured and discussed. The effect of the micrographs of the starting powders and the doping contents of Ce 3+ and Pr 3+ ions on the microstructure of YAG ceramic is also exhibited. In the photoluminescence spectra, the characteristic emission peaks of Pr 3+ ions at 608 nm and 638 nm are observed, and therefore white light-emitting diodes (WLEDs) with improved color-rendering properties obtained by using modified Ce:Pr:YAG phosphors. The composite phase structure of ceramic phosphor is designed for improving the extraction efficacy and increasing the luminous efficacy by breaking the total internal reflection (TIR) at the interface between air and ceramic. [ABSTRACT FROM AUTHOR]

Abstract: A new series of color tunable from yellow to near white emitting phosphors, La3SbO7:xBi3+, yEu3+ were prepared using a conventional solid state method and its structural, morphological, absorbance and photoluminescence properties and lifetime measurements were carried out to analyze the phosphor characteristics. The La3SbO7:Bi3+ phosphors crystallize into a phase pure weberite type structure with good particle morphology. Upon UV light excitation at 315 nm, these phosphors show broad band emission in the blue green region centered near 517 nm owing to the 3P1‐1S0 transitions of the Bi3+ activator. Critical emission quenching of La3SbO7:xBi3+ samples was observed at x = 0.04. Eu3+ is co‐doped with La3SbO7:0.04Bi3+ blue green phosphor to incorporate the red component to make a full color emission phosphor. The effective energy transfer from Bi3+ to Eu3+ ions has been assessed using Dexter's theory indicating resonance type through dipole‐quadrupole interaction. Further the decreasing trends in lifetime measurements confirm the existence of energy transfer process from Bi3+ to Eu3+. The near white light emitting phosphor La3SbO7:xBi3+, yEu3+ can be realized by adjusting the concentrations of the Bi3+ and Eu3+ with chromaticity coordinates: (0.30,0.48). The above results suggest that the developed phosphor could be potential to be used as a single phase white emission phosphor for n‐UV LED applications. [ABSTRACT FROM AUTHOR]

The achievement of multiple emission color phosphors has a significant importance in screen display, lighting devices, and multicolor imaging, but it still faces formidable challenges. In this work, double perovskite La 2 MgTiO 6 : Tb3+, Eu3+ phosphors with tunable emissions are designed and successfully synthesized. The obtained phosphors can emit intense green (Tb3+), red (Eu3+), and yellow emissions (Tb3+/Eu3+) via varying the co-doping concentration of Tb3+ and Eu3+. The CIE coordinates exhibit an excellent linear behavior in La 2 MgTiO 6 : Tb3+, Eu3+, revealing the possibility of linear adjustment of multiple emission colors. Detailed material characterization demonstrates that the multicolor tunable emission originates from energy transfer between Tb3+ and Eu3+. The decay dynamics analysis suggests that the multipole interaction between Tb3+ and Eu3+ is quadrupole-quadrupole interaction. A white light-emitting diode device with color rendering index of 84.7, correlated color temperature of 4684 K, and CIE coordinate of (0.3472, 0.3083) is fabricated by combining La 2 MgTiO 6 : Tb3+, Eu3+ yellow phosphor and BaMgAl 10 O 17 : Eu2+ blue phosphor. Our results reveal that La 2 MgTiO 6 : Tb3+, Eu3+ phosphors are promising luminescent materials in white light-emitting diodes. [Display omitted] • The linear adjustment of tunable luminescence from green to yellow and red region under excitation at 377 nm is achieved. • The influence of Tb3+/Eu3+ single- and co-doping concentration on luminescence performance is studied. • The yellow-emitting La 1.695 MgTiO 6 : 0.3 Tb3+, 0.005 Eu3+ phosphor have promising application in WLED. [ABSTRACT FROM AUTHOR]

• Crystallization induces incorporation of Tm3+/Dy3+/Zn2+ in the Al 4 B 2 O 9 lattice. • Appropriate heat treatment enhanced luminescence emission. • Crystalization promotes energy transfer from Tm3+ to Dy3+. Tm3+/Dy3+-doped glass ceramic (GC) phosphors containing Al 4 B 2 O 9 nanocrystallites were prepared by isothermal heat-treatment of aluminoborosilicate glass and the structure, optical properties were characterized. The GCs with Tm3+/Dy3+ luminescent center incorporated in the lattice of Al 4 B 2 O 9 nanocrystals reveal notable energy transfer from Tm3+ to Dy3+ and possess comparable thermal stability. The luminescence emission shift from cool white light to warm white light with increasing concentration ratio of Dy3+/Tm3+ and crystallinity. With extending heat-treatment time, the luminescence emission of GC increase firstly followed by decline in addition that the energy transfer efficiency increases whereas contrarily the lifetime decreases. Crystallization induced Dy3+/Tm3+ penetrating Al 4 B 2 O 9 is proposed to enhance the ligand field environment at luminescence center and further the energy transfer from Tm3+ to Dy3+. By adjusting concentration ratio of Dy3+/Tm3+ and the heat-treatment time, The doped GC phosphor with suitable chromaticity coordinate and prominent fluorescence potential for white light-emitting applications can be achieved. [ABSTRACT FROM AUTHOR]

Luminescence of Pr 3+ in Li 2 SrSiO 4 showed a broader f–f emission band compared with YAG:Pr 3+ . Atom parameters of Li 2 SrSiO 4 crystal were refined to provide data for quantifying the distortion of [SrO8] polyhedron. The distortion of [SrO8] was compared with that of [YO8] polyhedron in YAG to show the different Pr 3+ environments in Li 2 SrSiO 4 and YAG. Then, Pr 3+ was co-doped with Eu 2+ in Li 2 SrSiO 4 to provide a single phosphor for wLEDs. Energy transfer processes from 5d of Eu 2+ to both 3 P 2 and 1 D 2 of Pr 3+ were observed. The interaction type between Eu 2+ –Pr 3+ was proved to be dipole-quadrupole and kinetics of the energy transfer process was discussed based on Inokuti–Hirayama model. [ABSTRACT FROM AUTHOR]

A series of Ca2Mg0.25Al1.5Si1.25O7:Ce3+/Eu2+/Tb3+ phosphors was been prepared via a conventional high temperature solid-state reaction and their luminescence properties were studied. The emission spectra of Ca2Mg0.25Al1.5Si1.25O7:Ce3+,Eu2+ and Ca2Mg0.25Al1.5Si1.25O7:Ce3+,Tb3+ phosphors show not only a band due to Ce3+ ions (409 nm) but also as a band due to Eu2+ (520 nm) and Tb3+ (542 nm) ions. More importantly, the effective energy transfer from Ce3+ to Eu2+ and Tb3+ ions was confirmed and investigated by emission/excitation spectra and luminescent decay behaviors. Furthermore, the energy level scheme and energy transfer mechanism were investigated and were demonstrated to be of resonant type via dipole-dipole (Ce3+ to Eu2+) and dipole-quadrupole (Ce3+ to Tb3+) reactions, respectively. Under excitation at 350 nm, the emitting color could be changed from blue to green by adjusting the relative doping concentration of Ce3+ and Eu2+ ions as well as Ce3+ and Tb3+ ions. The above results indicate that Ca2Mg0.25Al1.5Si1.25O7:Ce3+,Eu2+/Tb3+ are promising single-phase blue-to-green phosphors for application in phosphor conversion white-light-emitting diodes. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

• Simulated data exhibited that energy transition can be easily achieved between Mn and Ge, and the potential application in the excitation of blue light. • The exchange interaction dominates the energy transfer mechanism. • A profound promotion achieved in the emission intensity on the 0.4% GeO 2 -doped phosphors. Ab initio calculation of density of states and the absorption spectral analysis were performed, and the influence of doping Mn4+ activator and Ge4+ sensitizer on the photoluminescence properties was also successfully discussed. The critical concentrations of Mn4+ and Ge4+ in Li 2 ZnTi 3 O 8 host excited at 350 nm were determined to be 0.3 and 0.4 %, respectively. The results obtained in this study indicated that there was a 50 % promotion in the emission intensity in the 0.4 % GeO 2 -doped phosphors when compared to the performance of undoped Li 2 ZnTi 3 O 8 : 0.3 % Mn4+ phosphors. Moreover, the International Commission on Illumination of Li 2 ZnTi 3 O 8 :0.3 % Mn4+ point was successfully turned from (0.7268, 0.2732) to (0.7318, 0.2682), and the color purity - from 98.3 to 99.5 % by co-doping 0.4 % GeO 2. The energy transfer mechanism (Mn4+---Mn4+ pairs, and Ge4+---Mn4+ pairs) was also investigated. Concentration and thermal quench were also under consideration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Continuous synthesis of Cs x Pb y Br z NCs were realized via a microfluidic system. • Cs x Pb y Br z perovskite NCs with tunable dimensionalities were achieved. • Stable CsPbBr 3 /Cs 4 PbBr 6 composite NCs exhibited bright emissions in solid forms. • Growth and luminescence mechanisms of Cs x Pb y Br z perovskite NCs were revealed. All-inorganic perovskite CsPbBr 3 shows great potential in optoelectronic device applications due to their excellent optoelectrical properties. However, its practical use is still dauntingly plagued by the poor stability. Recently, its derivatives Cs 4 PbBr 6 and CsPb 2 Br 5 featured with good stability and the versatility in crystal structure have emerged as promising alternatives. Nevertheless, synthesizing such a series of perovskites through a facile, scalable, and high-yield method is challenging, and their luminescence mechanisms are still elusive. Herein, we reported a facile and rapid method for continuous synthesis of Cs x Pb y Br z -based perovskites (including Cs 4 PbBr 6 , CsPbBr 3 /Cs 4 PbBr 6 , CsPbBr 3 , CsPbBr 3 /CsPb 2 Br 5 , CsPb 2 Br 5) via a microfluidic system. The transformations of different dimensional perovskite nanocrystals were realized by simply adjusting the precursor flow rate. CsPbBr 3 /Cs 4 PbBr 6 and CsPbBr 3 /CsPb 2 Br 5 composite nanocrystals exhibited bright emissions in their solid forms, where CsPbBr 3 nanocrystals uniformly embedded in Cs 4 PbBr 6 or CsPb 2 Br 5 matrix. Simultaneously, strong green fluorescence exclusively from CsPbBr 3 nanocrystals was detected and related energy transfer in composite nanocrystals was further investigated. Finally, the highly stable CsPbBr 3 /Cs 4 PbBr 6 nanocrystals were used for the construction of WLED with a wide color gamut of 131% NTSC. This work provides a novel path for large-scale and controlled synthesis of the ternary Cs-Pb-Br materials for specific light-emitting applications. [ABSTRACT FROM AUTHOR]

White light emitting diodes (WLEDs), as the fourth generation of new light source, has the advantages of light weight, small size, low energy consumption, fast response speed and convenient use, but their poor thermal stability, high correlation color temperature (CCT) and low color rendering (Ra) limit their large-scale application of high-power WLED. In this work, we report the preparation of WLEDs by combining rare earth ions Tb3+-Eu3+ with La 2 Ge 2 O 7 , which exhibits tunable photoluminescence properties and excellent thermal stability. The detailed study shows that the layered structure of the material is conducive to efficient energy transfer (ET) between Tb3+ (sensitizer) and Eu3+ (activator), and effectively inhibits the luminescence attenuation caused by concentration quenching. Based on this, the doping ratio of Tb3+/Eu3+ in the phosphor is controlled and the phosphor is combined with blue chip to obtain excellent white light (CCT = 3955 K). The light efficiency (87 lm w−1) is comparable to that of commercial phosphors, and there is no significant decrease after continuous operation for 1000 h, which provides a good candidate material for the preparation of high-power WLED. • Coordinated white light emission can be achieved by La 2 Ge 2 O 7 doping Tb3+ and Eu3+ in a single substrate. • The LGO material realizes efficient energy transfer and suppresses concentration quenching and thermal quenching. • It achieves 1000 h of stable and efficient white light (CCT = 3955 K) with a light efficiency of 87 lm w−1. [ABSTRACT FROM AUTHOR]

In this work, we provide a paradigm how to realize white light emission by utilizing the energy transfer from the Bi3+ to Eu3+ ions. First, a novel Bi3+ activated phosphor set of highly oxygen-deficient perovskite derivatives (Ba 3 YGa 2 O 7.5 , BYGO) were synthesized through the conventional high-temperature solid-state method. The crystal structure was confirmed by Rietveld refinement. Then, Eu3+ was introduced to the phosphor composition to construct energy transfer pathway with Bi3+. The emission color of the BYGO:Bi3+,Eu3+ phosphors can be changed from cyan to white and orange-red by altering the Bi3+/Eu3+ doping ratio. The energy transfer from the Bi3+ to Eu3+ ions was ascribed to dipole-dipole interaction. Finally, a single-component WLED device with a color-rendering index of 84.9 was successfully prepared by employing a near-ultraviolet chip and the BYGO:Bi3+,Eu3+ phosphors. This work not only indicates that the as-prepared BYGO:Bi3+,Eu3+ phosphors are a potential candidate for near-ultraviolet WLED, but also demonstrated that energy transfer is an avenue for single-phased white light emission. [Display omitted] • The cyan phosphor Ba 3 YGa 2 O 7.5 :Bi3+ was synthesized for the first time. • The energy transfer from the Bi3+ to Eu3+ ions is constructed. • Adjusting the doping ratio of Bi3+ to Eu3+ realizes multicolor emission. • A single-phased WLED with a color rendering index of 84.9 was achieved. [ABSTRACT FROM AUTHOR]

Ce 3+ and/or Dy 3+ activated Ca 20 Al 26 Mg 3 Si 3 O 68 phosphors were synthesized by high temperature solid state reaction and their luminescent properties were studied. There are two emissions peaking at 407 and 577 nm in the emission spectra of Ca 20 Al 26 Mg 3 Si 3 O 68 :Ce 3+ , Dy 3+ , which are due to the transitions of Ce 3+ and Dy 3+ ions, respectively. More importantly, the effective energy transfer from Ce 3+ to Dy 3+ ions has been confirmed and investigated by emission/excitation spectra and luminescent decay behaviors. Furthermore, the energy level scheme and mechanism of energy transfer were investigated and it was demonstrated to be resonant type via dipole–dipole reaction. Under the excitation of 345 nm, the emitting color can change from blue to white by adjusting the relative doping concentration of Ce 3+ and Dy 3+ ions, indicating that the phosphors Ca 20 Al 26 Mg 3 Si 3 O 68 :Ce 3+ , Dy 3+ are promising single-phase white-emitting phosphors for application in pc-white LEDs. [ABSTRACT FROM AUTHOR]

Abstract: Ce3+ and/or Eu2+ activated Ca2Mg0.5AlSi1.5O7 phosphors have been synthesized by high temperature solid state reaction. The luminescence of Ca2Mg0.5AlSi1.5O7:Ce3+, Eu2+ is studied as potential ultraviolet light-emitting diodes (UV-LEDs). There are two emissions peaked at 409 and 525nm which come from d–f transitions of Ce3+ and Eu2+ ions. The energy transfer from the Ce3+ to Eu2+ has been discussed and it is demonstrated to be a resonant type via a dipole–dipole mechanism. The critical distance of Ce3+ to Eu2+ in Ca2Mg0.5AlSi1.5O7 has been calculated to be 26.71Å by spectral overlap method. Furthermore, the Ca2Mg0.5AlSi1.5O7:Ce3+, Eu2+ phosphors can emit a tunable blue-to-green light under the excitation of 350nm by appropriately tuning the relative proportion of Ce3+/Eu2+, indicating that the phosphors Ca2Mg0.5AlSi1.5O7:Ce3+, Eu2+ are promising blue-to-green emitting phosphors for application in pc-white LEDs. [Copyright &y& Elsevier]

Phosphors with excellent color adjustable properties have always been the research focus of scientific researchers. This work uses two strategies to control the luminescence behavior of Eu2+ ions in the Lu 2 Mg 2 Al 2 Si 2 O 12 (LMAS) matrix. Firstly, by adjusting the Eu2+ ion concentration, the emission spectra of Lu 2 Mg 2 Al 2 Si 2 O 12 :Eu2+ (LMAS:Eu2+) could achieve a 39 nm red shift from 451 to 490 nm, which provides a good blue to cyan emission. Secondly, the Lu 2 Mg 2 Al 2 Si 2 O 12 :Eu2+,Mn2+ (LMAS:Eu2+,Mn2+) realized the tuning from the cyan to the white region by introducing Mn2+ ions, which is owing to the sensitization process of Eu2+ to Mn2+ enhancing the red-light emission. The energy transfer process was explored in detail, and the energy transfer efficiency was calculated to be more than 60%. Meanwhile, the thermal stability of the material was also studied. The thermal stability illustrates its potential application in white light-emitting diode (WLED). Under 30 mA drive current, the device obtained by using 365 nm ultraviolet (UV) chip with LMAS:0.01Eu2+,0.35Mn2+ phosphor has a color rendering index (Ra) as high as 93.1, R9 = 85, LE = 1.81 lm/W, the color coordinate is (0.3076, 0.3119) and the correlated color temperature (CCT) is 6984 K, which is obviously in the white light area. The above results indicate that LMAS:Eu2+,Mn2+ phosphors with full-visible-spectrum have potential applications in solid-state lighting. Two strategies to control the luminescence behavior of Eu2+ ions in the LMAS matrix. By adjusting the Eu2+ ions concentration, the emission spectra of LMAS:Eu2+ could achieve a 39 nm red shift from 451 to 490 nm, and it demonstrated the occupying problem of Eu2+ ions in detail. Based on the energy transfer process in phosphor, white light emission is realized. The single-phase full-visible-spectra LMAS:Eu2+,Mn2+ phosphor-converted WLED achieves the ultra-high Ra (93.1) and R9 (85), near-standard CIE (0.3076, 0.3119) and CCT (6984 K). [Display omitted] • The main novelties are highlighted as follows. • By adjusting the Eu2+ ion concentration, the emission spectra of Lu 2 Mg 2 Al 2 Si 2 O 12 :Eu2+ (LMAS:Eu2+) could achieve a 39 nm red shift from 451 to 490 nm, which provides a good blue to cyan emission. • The luminescence properties of Eu2+ ions at different sites in the garnet matrix were discussed. • Through the introduction of Mn2+ ions, energy transfer is realized, and a single matrix white phosphor is obtained. • The device obtained by using 365 nm ultraviolet (UV) chip with LMAS:0.01Eu2+,0.35Mn2+ phosphor has a color rendering index (Ra) as high as 93.1, the color coordinate is (0.3076, 0.3119) and the correlated color temperature (CCT) is 6984 K. [ABSTRACT FROM AUTHOR]

High quantum efficiency and thermal stability have always been the goals to pursue and challenges for lighting application. In this work, sunlight-like white emission has been achieved in a new prepared single phased Rb 2 CaP 2 O 7 : 0.005Ce3+, 0.01Eu2+ phosphor, which exhibits high internal quantum efficiency (IQE = 74.36%), external (EQE = 56.77%) quantum efficiency and excellent thermal stability. Based on the broadband emission from 4f-5d transitions of Ce3+/Eu2+ ions and high energy transfer efficiency of Ce3+→Eu2+ (measured up to 60%), the extremely wide color-tunable emission from blue-violet to white and then to orange-yellow is realized in Rb 2 CaP 2 O 7 : 0.005Ce3+, xEu2+ phosphors. Moreover, a prototype WLED device is packaged by combing the prepared Ra 2 CaP 2 O 7 : 0.005Ce3+, 0.01Eu2+ white phosphors with an UV LED chip (λ = 310 nm), and the obtained WLED emits bright sunlight-like white light with color coordinates of (0.377, 0.324). The correlated color temperature (CCT) and the color rendering index (CRI) value of the WLED are 3208 K and 88.4, respectively. These results can provide effective guidance for the design of color-tunable single-phase white phosphors with high luminous efficacy and thermal stability. Sunlight-like emission phosphor with high quantum efficiency and excellent thermal stability is achieved, and a WLED prototype device with CCT = 3208 K, Ra = 88.4 is fabricated from the synthesized phosphors. [Display omitted] • Extremely wide color-tunable emission is realized in Ra 2 CaP 2 O 7 : Ce3+, Eu2+ phosphors. • Sunlight-like emission with high quantum efficiency and excellent thermal stability is achieved. • A WLED prototype device with CCT = 3208 K, Ra = 88.4 is fabricated from the synthesized phosphors. [ABSTRACT FROM AUTHOR]

• Dy3+ doped and Dy3+/Eu3+ co-doped Na 2 ZnP 2 O 7 phosphors were successfully synthesized via the solid-state method. • The emission color of Dy3+/Eu3+ co-doped phosphors could be tuned from the yellowish-white region to the reddish. • An efficient ET from Dy3+ to Eu3+ is obtained with dipole-dipole interaction. • Na 2 ZnP 2 O 7 doped Dy3+ and codoped Dy3+/Eu3+ phosphors can be applied in the fields of lighting and WLEDs. A series of Dy3+ single doped and Dy3+/Eu3+ codoped Na 2 ZnP 2 O 7 phosphor was synthesized by conventional solid-state reaction method. The crystal structure, vibrational modes and luminescence properties were researched. The absorption spectrum was analyzed in term of the Judd–Ofelt theory; the intensity parameters Ω 2 , Ω 4 , and Ω 6 have been evaluated for Dy3+ doped Na 2 ZnP 2 O 7 sample. The luminescence spectra are dominated by a strong emission in the 574 nm region corresponding to the 4F 9/2 → 6H 13/2 transition and the optimal doping concentration of Dy3+ is about 4%mol. The optical properties of Dy3+/Eu3+ codoped Na 2 ZnP 2 O 7 micro crystals were also investigated in order to study the energy transfer between the two ions. The PL spectra of the as prepared samples recorded under the 349 nm, 365 nm and 393 nm excitations show emission peaks of both Dy3+ and Eu3+. The emission intensity of Dy3+ is decreased with increasing Eu3+ concentration, which is due to the energy transfer from Dy3+ to Eu3+ in the Na 2 ZnP 2 O 7 host matrix. Furthermore, the chromaticity color coordinates are tuned from the yellowish-white region for the single Dy3+ doped Na 2 ZnP 2 O 7 to the reddish region for Dy3+/Eu3+ co-doped Na 2 ZnP 2 O 7 samples. This type of luminescence phosphors has promising applications in the fields of W-LEDs, solid-state lighting and optoelectronic devices. [ABSTRACT FROM AUTHOR]

PL excitation and emission spectra of Dy3+ doped Y 2 WO 6 , mixture of Y 2 WO 6 and Y 2 W 3 O 12 , Y 2 W 3 O 12 , and Y 6 WO 12 phosphors. • Y 2 WO 6 , Y 2 W 3 O 12 , and Y 6 WO 12 were synthesized. • The Dy3+ doped Y 2 WO 6 has the strongest PL intensities. • The Dy3+ optimal doping concentration was 2 mol% in Y 2 WO 6 phosphor. • 2 mol% Dy3+ doped Y 2 WO 6 phosphor kept 74 % intensity of 50 °C at 150 °C. • WLEDs were obtained by combining the phosphor with 308 nm chips. Through a solid-state reaction method, Dy3+ doped monoclinic phase of Y 2 WO 6 , Y 2 W 3 O 12 , and hexagonal phase of Y 6 WO 12 phosphors were synthesized. The Y 2 WO 6 and Y 2 W 3 O 12 were composed of micrometre-scale particles, and the Y 6 WO 12 was composed of nanometre particles. The energy-dispersive spectra (EDS) suggested that the atom ratio of Y to W decreased with the sequence of Y 6 WO 12 , Y 2 WO 6 , and Y 2 W 3 O 12 phosphors. The E g values were calculated based on the diffuse reflection (DR) spectra. The Dy3+ doped Y 2 WO 6 phosphor had the most intense photoluminescence (PL) intensities and the optimal doping concentration was 2 mol%. The energy transfer efficiency from WO 6 6− to Dy3+ was calculated. The lifetime of 4F 9/2 →6H 13/2 transition of Dy3+ was a few hundred nanoseconds. At 150 °C, the 2 mol% Dy3+ doped Y 2 WO 6 phosphor kept 74 % intensity of 50 °C. The white light emitting diode (WLED) devices were fabricated by combining phosphors with 308 nm LED chips. [ABSTRACT FROM AUTHOR]

Single-composition Ba 2 YAlO 5 : Eu3+ (BYAO: Eu) red luminescent phosphor were prepared through high temperature solid-state reaction. The crystal structure and luminescence properties were studied via X-ray diffraction and photoluminescence spectra. Upon 468 nm excitation, the main emission peaks of BYAO: Eu phosphors locate in the 582, 591, 614 and 705 nm, corresponds to the 5D 0 →7F J (J = 0–3) conversion of Eu3+ ions. In Eu3+ singly doped BYAO phosphor, the optimum doping concentration and transfer distance was 20 mol%, 11.16 Å, respectively. Under 468 nm excitations, the phosphors of BYAO: Eu showed obvious thermal quenching properties and the 473 K luminescence intensity was 74.4% of 298 K. Moreover, the CIE chromaticity coordinate range from yellow-green to red through changing the concentration of Eu3+ ions, and calculated value of purity is 96.4%. it indicates that BYAO: Eu phosphor is potentially promising material for commercial red phosphors. • Phosphor energy transfer is between the nearest neighbor ions. • Eu3+-O2- charge transition band appeared redshifted. • Phosphors have obvious thermal quenching properties. • The color coordinates of phosphors range yellow-green from red. • Color purity of Ba 2 YAlO 5 : 0.2Eu3+ phosphor is calculated to be 96.6%. [ABSTRACT FROM AUTHOR]