Codoped YF3 Research Articles

Upconversion luminescence enhancement and color modulation in Yb3+/Er3+/Ln3+ (Ln = Tm, Ho) tri-doped YF3 microrods

Upconversion luminescence enhancement and color modulation in Yb3+/Er3+/Ln3+ (Ln = Tm, Ho) tri-doped YF3 microrods

Synthesis of Yb3+/Er3+ co-doped Y2O3, YOF and YF3 UC phosphors and their application in solar cell for sub-bandgap photon harvesting

Abstract Yb3+/Er3+ co-doped Y2O3, YOF and YF3 upconversion (UC) phosphors were synthesized by co-precipitation method. The three upconversion phosphor samples show strong green (540 nm) and red (660 nm) emission bands visible to naked eyes even at the low intense incident light. The potential application of Y2O3, YOF, and YF3 UC phosphors was demonstrated by incorporating them in amorphous silicon thin film solar cells and they showed upconversion current densities of 0.36 mA/cm2, 0.23 mA/cm2, and 0.207 mA/cm2 respectively when the cell was illuminated with a 980 nm IR laser. Intensity-dependent J-V studies were carried out to understand the effectiveness of UC phosphors in improving solar cell parameters. An improvement of 7.5% in Jsc was obtained for amorphous silicon solar cell incorporated with YF3 UC phosphors under AM1.5 along with 980 nm NIR illumination.

Role of Ca2+ co-dopants on structural and optical properties of YF3:Tm3+/Yb3+ upconversion phosphor for improved optical thermometry

Abstract This work describes the synthesis, structural and optical properties of Tm3+/Yb3 doped and Ca2+ co-doped YF3 upconversion phosphor material. The effect of Ca2+ ions co-dopant concentration is varied at 0, 10, 20 and 30 mol% to observe it’s effect on YF3:Tm3+/Yb3+ through different characterizations like XRD, XPS, FE-SEM, FTIR, UV–vis and upconversion measurements. Dominant upconversion emission bands are found at 450, 476, 645 and 696 nm emission wavelengths corresponding to the 1D2→3F4, 1G4→3H6, 1G4→3F4 and 3F3→3H6 transitions within Tm3+ activator center on 976 nm excitation. Finally, prepared samples are utilized in temperature sensing application demonstrations with Ca2+ ions co-dopants concentration variations.

Radioluminescence and thermoluminescence of rare earth doped and co-doped YF3

Abstract An investigation of the luminescent properties of undoped and rare earth (RE) singly- and co-doped YF 3 was carried out by means of radioluminescence (RL) and thermoluminescence (TL) measurements. Materials were obtained by ligand-free co-precipitation with Ce, Tm, Tb or Eu substituting for Y, followed by calcination in air at 500 °C for 1 h. RL measurements confirmed the effective luminescence activation of the host. TL measurements revealed a relatively intense contribution of the host, with Tm doping yielding the strongest signal among the singly-doped samples. Co-doping with Ce and Tm was investigated within the 0.5–5 mol% range for each RE, with the 0.5,0.5 (Ce,Tm) mol% co-doping yielding the strongest luminescence signal. However, a clear correlation between the RE dopant(s) and TL peaks was not found.

Constructing multiform morphologies of YF: Er3+/Yb3+ up-conversion nano/micro-crystals towards sub-tissue thermometry

Abstract Er 3+ /Yb 3+ co-doped YF 3 samples with uniform rice-like, two-dimension (2D) hexagonal nano-architectures and truncated octahedral micro-crystals were synthesized through a one-step hydrothermal method, and their possible growth mechanisms were also proposed. Upon 980 nm excitation, the up-conversion (UC) emitting color of samples was finely modulated from yellow to pure green with increasing the particle size, which was interpreted in terms of non-radiative process and surface effect. Thermometric capabilities of samples with different morphologies were evaluated based on the fluorescence intensity ratio (FIR) of 2 H 11/2 and 4 S 3/2 levels through temperature-dependent UC spectra, and the optimal absolute sensitivities of samples were all approached to about 0.0026 K -1 at 490 K. The potentiality of rice-like nano-crystals for temperature detection in sub-tissue was demonstrated by ex vivo experiments. Results display that the sensitivity of YF 3 : Er 3+ /Yb 3+ nano/micro-crystals is independent of morphologies and sizes, which exploit an effective avenue for developing UC-based thermometers in sub-tissue with stable sensitivity.

Synthesis and Luminescent Properties of Ce3+/Eu3+ Coactivated YF3 Nanobundles

YF3 nanobundles have been synthesized via a facile solvothermal synthesis, which were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FT-IR) and Thermogravimeter (TG). Results show that there are adsorbed water and residual organic molecules on the surface of YF3 nanobundles, which play a key part in the formation of the final structure. Their morphology and structure can be tuned by varying reaction conditions including the amount of F− ions and temperature. The luminescence properties of Ln3+-doped and Ce3+/ Eu3+co-doped YF3 have been investigated by photoluminescence (PL). It is found that the luminescence intensity of Ce3+/ Eu3+co-doped YF3 nanobundles is obviously enhanced due to the efficient sensitizing of Ce3+.

Preparation and Photoluminescent Properties of Ce<sup>3+</sup>, Yb<sup>3+</sup> Co-Doped YF<sub>3</sub> Nanophosphors for Solar Cells

An efficient near-infrared (NIR) quantum cutting (QC) nanophospors with Ce3+, Yb3+ co-doped in YF3 had been prepared by hydrothermal method and characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), photoluminescence spectra and decay dynamics. The obtained nanorods were uniform and monodisperse. Under the excitation of 5d level of Ce3+, an intense NIR emission at 900 1100 nm was observed which match to the energy of Si band gap of Si - based solar cells. In the Ce3+, Yb3+ codoped YF3, the lifetime of Ce3+ decreases and the quantum efficiency (QE) increases with increasing Yb3+ concentration.

Facile chemical conversion synthesis and luminescence properties of uniform YF3 nanowires

Well-dispersed YF3 nanowires were synthesized by a designed hydrothermal conversion method with Y(OH)3 nanowires as precursor. Various equipments were used to characterize the samples. The results show that Y(OH)3 nanowires precursor was prepared through a simple hydrothermal process, which then served as the precursor for the fabrication of YF3 nanowires by a hydrothermal process. The whole process was carried out under aqueous conditions without any organic solvent, surfactant or catalyst. The conversion process from Y(OH)3 precursor to YF3 nanowires was investigated by time-dependent experiments. The possible formation mechanism of YF3 nanowires was presented in detail. Under UV excitation, 5%(mass fraction) Eu3+ or 5%(mass fraction) Tb3+ doped YF3 samples exhibit strong red or green emission, corresponding to the characteristic lines of Eu3+ and Tb3+, respectively. Moreover, the luminescence colors of the Eu3+ and Tb3+ codoped YF3 samples can be tuned from red, yellow and green-yellow to green by simply adjusting the relative doping concentrations of the activator ions under a single wavelength excitation, which might find potential applications in the fields of, such as, light display systems and optoelectronic devices.

Solvothermal synthesis and tunable luminescence of Tb3+, Eu3+ codoped YF3 nano- and micro-crystals with uniform morphologies

Abstract Tb3+, Eu3+ codoped YF3 nano- and micro-crystals with the morphologies of ellipsoid-like nanoplate, spindle, sandwich-structural rhombus and nanoaggregate were synthesized through a solvothermal method. The morphologies of the prepared products can be tailored by controlling the volume ratio of ethylene glycol (EG) to H2O, solvent type or the reaction time. A possible formation mechanism of the sandwich-structural rhombus like YF3 phosphor was proposed. The emitting colors of YF3:Tb3+,Eu3+ phosphors can be easily tuned from yellowish green, yellow to orange by increasing Eu3+ concentration. The energy transfer from Tb3+ to Eu3+ in YF3 phosphors was studied. It was found that the interaction type between Tb3+ and Eu3+ is electric dipole–dipole interaction.

Electrospinning preparation and upconversion luminescence of yttrium fluoride nanofibers

Rare earth (RE) fluoride fibers were synthesized by polymer-supported electrospinning combining two subsequent thermal treatments. One-dimensional (1D) structure was maintained after the fibers were heated. The treated fibers, which were usually several millimeters long, consisted of closely-packed crystalline grains. Pumped with a 980 nm laser, Yb3+ and Tm3+ codoped YF3 fibers exhibited intense upconversion (UC) fluorescence.

Upconversion Luminescence Properties of YF3:Yb3+, Er3+ Nanoclusters

The synthesis, characterization, and spectroscopy of upconverting Yb3+/Er3+ codoped YF3 rod-like nanoclusters are presented. The YF3 nanoclusters were synthesized by a simple hydrothermal method. The clusters structure was characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Under 978 nm laser excitation, stronger blue (4F(5/2) --> 4I(15/2) and 2p(3/2) --> 4I(11/2)) and green (4S(3/2), 2H(11/2) --> 4I(15/2)) upconversion luminescence were observed at 978 nm. The measured intensity of upconversion luminescence was different when pump power changed, which shows that the blue and green upconversion luminescence come from three-photon and two-photon energy transfer processes, respectively.

Size Dependent Ultraviolet Upconversion in Single YF3:Yb3+/Tm3+ Particles

Yb3+-Tm3+ codoped YF3 bulk material was synthesized through a facile high-temperature calcinations method. By grinding and selecting, the particles with different desired sizes in microns were obtained. Under 980 nm excitation, optical upconversion (UC) from near-infrared (NIR) to ultraviolet (UV) was studied for each group of particles for the effect of their size on UC. Comparing with the bulk sample, the micro-size particles exhibited strong ability for NIR-to-UV UC. With the particle size decreasing from 800 microm to 20 microm, their UV emission intensities increased rapidly. Two possible mechanisms were proposed and discussed for clarifying the small size effect (SSE).

Red and near infrared down-conversion in Er3+/Yb3+ co-doped YF3 performed by quantum cutting

Er3+/Yb3+ co-doped YF3 powder is prepared by combining a nitrate decomposition method with a NH4HF2 fluorization process, from which efficient energy transfer induced down-conversion is achieved. An absorbed 365 nm near ultraviolet photon is split into two photons of 650 nm red and 1000 nm near infrared radiations, both falling in the responding region of Si-based solar cells. The quantum cutting mechanism has been proposed and discussed and the energy transfer efficiency for the quantum cutting is evaluated by developing an emission intensity ratio contrast method. The investigation might offer a new possible approach to achieve Si-based solar cells of high efficiency by down-converting the near ultraviolet part of the solar spectrum.

Study on Upconversion Luminescence and Luminescent Dynamics of 20%Yb3+, 0.5%Tm3+ Co-Doped YF3 and GdF3 Nanocrystals

20%Yb3+, 0.5%Tm3+ co-doped YF3 and GdF3 were synthesized through a facile hydrothermal method. After annealing under an argon atmosphere, the sizes and morphologies of the two samples were characterized by field emission scanning electron microscopy, and the phase and crystallization were analyzed by X-ray diffraction. With a 980 nm continuous wave laser diode as the excitation source, blue and ultraviolet upconversion emissions in the wavelength range of 260-510 nm of Tm3+ and Gd3+/Tm3+ ions were recorded. Under the same excitation conditions, the upconversion emission spectra of the two nanocrystals were compared and analyzed. Gd3+ in the ground state cannot absorb 980 nm photons directly because of the large energy gap between the ground state 8S7/2 and the first excited state 6P7/2. In the 20%Yb3+, 0.5%Tm3+ co-doped GdF3 nanocrystals, the excited states 6I(J) of Gd3+ can be populated through the energy transfer 3P2 --> 3H6 (Tm3+): 8S7/2 --> 6I(J)(Gd3+), meaning that Yb3+ acted as primary sensitizers and Tm3+ acted as secondary sensitizers, transferred energies to host material Gd3+ and resulted in the ultraviolet upconversion emission of the host ions. In this article, the upconversion luminescent dynamics were studied at the onset of a 980 nm pulsed laser from an optical parametric oscillator pumped by a 10 ns pulsed Nd:YAG laser, too.

Ultraviolet and visible upconversion emission in Tb3+/Yb3+ co-doped fluorophosphate glasses

Ultraviolet and visible upconversion emissions in Tb3+/Yb3+ co-doped YF3–BaF2–Ba(PO3)2 glasses were observed under 980-nm laser diode excitation. The dependence of the emission intensities of Tb3+ on the pump power reveals that two-photon processes account for blue cooperative emission of Yb3+ at 476 nm and green upconversion emission of Tb3+ at 543 nm, and three-photon processes for ultraviolet emission of Tb3+ in the wavelength range of 379–435 nm. The effects of Tb3+ concentration on the emission intensity and the lifetime of Tb3+ and Yb3+ are investigated in detail. It is found that the cooperative energy transfer from a pair of excited Yb3+ ions to a ground Tb3+ ion is responsible for the appearance of blue and green upconversion emissions due to the 5D4→7F J (J=6,5,4,3) transitions of Tb3+, and the resonance energy transfer from Yb3+ to Tb3+ accounts for the population on the 5D3,5G6 level and ultraviolet upconversion emission.

Luminescence properties of rare earth doped YF3 and LuF3 nanoparticles

Eu 3 + doped and Yb3+/Ho3+ codoped LuF3 and YF3 nanoparticles with a size distribution of 200–300 nm have been prepared by adopting a combustion-fluorization method. The luminescence spectra of Eu3+ and Ho3+ ions in the YF3 and LuF3 nanoparticles have been investigated through comparison. It is found that the Eu3+ and Ho3+ ions in the two hosts show different luminescence properties although the sites occupied by the rare earth (RE) ions in the LuF3 and YF3 hosts are of the same symmetry. The different luminescence properties may be ascribed to the difference in the RE-F bond nature in the YF3 and LuF3 hosts.

Self-Assembly of Yb3+-Tm3+ Co-Doped YF3 Elongated Nanocrystals into Nanobundles of Straw and Up-Conversion Fluorescence

The hierarchical self-assembly of Yb3+ and Tm3+ co-doped YF3 elongated nanocrystals (NCs) into nanobundles of straw were synthesized through a facile hydrothermal route. The formational mechanisms of regular aggregates of the building blocks were studied. Ultraviolet (UV)-blue upconversion emissions of Tm3+ were recorded under 980-nm excitation by the Yb3+ sensitizer. The relatively bright blue emission indicated that the bundles have the potential for applications such as short-wavelength solid-state lasers and display devices.

Synthesis and Luminescence Properties of Lanthanide (III)-Doped YF3 Nanoparticles

Synthesis process and luminescence properties of trivalent lanthanide ions (Ln3+) doped YF3 nanoparticles have been investigated. To synthesis Ln(3+)-doped YF3 nanoparticles, the mixture of (YCl3 x nH2O + LnCl3 x nH2O), and NH4F was hydrothermal treated at 180 degrees C in a Teflon-liner auto-clave or heated at higher temperatures (400 degrees C - 600 degrees C) in a stove. The XRD patterns showed that the Ln(3+)-doped orthorhombic YF3 nanoparticles with no second phase have been prepared. The solid solution Y(1-x)Eu(x)F3 (x = 0 - 0.4) nanoparticles have been synthesized. The luminescence concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurred at higher Eu3+ concentrations (30 mol%). The upconversion luminescence of Er(3+)-Yb3+ codoped YF3 nanoparticles under 980 nm excitation has also been observed. With increase of heated temperature, the size of the Er(3+)-Yb3+ codoped YF3 nanoparticles increased gradually, and upconversion luminescence intensity increased significantly.

Down/Up Conversion in Ln3+-Doped YF3 Nanocrystals

Nanocrystalline Ln3+-doped YF3 phosphors have been synthesized via a facile sonochemistry-assisted hydrothermal route. YF3 nanoparticles are demonstrated to be a good host material for different lanthanides. Varying the dopants leads to different optical properties. In particular, the feasibility of inducing red, green, and especially blue emission in the Yb3+/Er3+ co-doped YF3 sample by up-conversion excitation in the near-infrared region is demonstrated. Such unusually strong 411 nm blue up-conversion emission has seldom been reported in other Yb3+/Er3+-doped systems. The up-conversion mechanisms have been analyzed.