Transition Of Yb3 Research Articles

Cr3+-Yb3+ energy transfer drives ultra-wideband thermally-stable NIR-emitting Sr3Sc2Ge3O12 garnet phosphors for pc-LED application

The development of medical, military, and other fields has greatly increased the demand for broadband near-infrared light sources. This article reports that Sr3Sc2Ge3O12: Cr3+ (SSGO: Cr3+), a broadband near-infrared phosphor with 850 nm as the luminescence center, has an emission spectrum covering 700–1200 nm and a full width at half maximum (FWHM) of 125 nm under 490 nm excitation. To further increase the FWHM value, Yb3+ is introduced into the phosphor of SSGO: Cr3+ to enable energy transfer from Cr3+ to Yb3+. After doping 1 % of Yb3+ onto the Sr2+ site, the near-infrared emission generated by the 4A2→4T1(4P) transition of Cr3+ and the near-infrared emission generated by the 2F5/2 → 2F7/2 transition of Yb3+ work so that the FWHM increases to 220 nm. In addition, the thermal stability of the phosphor after co-doping with Yb3+ is also greatly enhanced from 61.6 % to 75.1 % by comparing it to the Cr3+ single-doped sample. In addition, SSGO:0.08Cr3+, 0.01 Yb3+ was combined with a commercial 490 nm chip to prepare a broadband near-infrared light-emitting diode (pc-LED).

Efficient broadband NIR emission of Yb3+-activated double-perovskite tungstate Ba0.5MgLaWO6☆

Broad-band near-infrared (NIR) phosphors have garnered increasing attention due to the versatile applications in spectroscopy technology fields, but the choice of efficient NIR phosphors remains a challenge. Here, Yb3+-activated cubic double-perovskite tungstate Ba0.5MgLaWO6 was synthesized using a solid-state reaction method. A broadband NIR emission (800–1150 nm) is observed from the 2F5/2→2F7/2 transition of Yb3+ activators in Ba0.5MgLaWO6 under the excitation by UV and near-UV light. Photoluminescence (PL) spectra, decay and emission lifetimes, concentration-dependent intensities, and low temperature luminescence of Yb3+-activated Ba0.5MgLaWO6 were investigated to study the energy transfer (ET) from isolated WO6 polyhedra to Yb3+ activators. The main luminous mechanism involves cooperative energy transfer (CET), wherein, one high-energy excitation photon absorbed by host WO6 group converts to two NIR photons emitted by Yb3+. The partial substitution of Mo6+ for W6+ in Ba0.5MgLaWO6 further leads to a significant increase of the intensity and lifetime of the NIR luminescence. This work provides a feasible strategy for developing a new Yb3+-doped perovskite tungstate, which demonstrates efficient wavelength down-conversion from UV and near-UV to NIR. This material could find versatile applications as an effective NIR luminescent candidate.

Influence of Au0 metallic particles on NIR laser emission of Yb3+ ions in Li2O−HfO2−SiO2 glass ceramic

This study consists of the synthesis, characterization, and analysis of photoluminescence (PL) spectra for Li2O−HfO2−SiO2−Yb2O3 glass ceramics sensitized with small amounts of Au2O3. Using the results of XRD and X-ray photoelectron spectroscopy (XPS) studies indicated a progressive reduction of Au3+ ions into Au0 metallic particles (MPs) with increase of Au2O3 content. Investigations into the infrared spectra highlighted a growing concentration of induced defects in the samples due to the increased proportion of Au0 MPs. Optical absorption (OA) spectra exhibited a distinct band attributed to the 2F7/2 → 2F5/2 transition of Yb3+ within wavelength range of 800–980 nm. Furthermore, a wide absorption band linked to the surface plasmon resonance (SPR) of Au0 MPs was identified in the visible region. PL spectra, recorded at λexc = 450 nm, revealed a band between 980 to 1025 nm, associated with the 2F5/2 → 2F7/2 transition of Yb3+ ions. Another emission band was observed due to the sp → d transition of Au0 MPs within the visible region. Observed enhanced PL emission from Yb3+ ions in the NIR range was ascribed to the energy transfer from Au0 MPs to Yb3+ ions. Ultimately, it was deduced that Au0 MPs played a pivotal role in enhancing the PL output of Yb3+ ions in the Li2O−HfO2−SiO2 glass ceramic. Thus, glass ceramics incorporating an optimal concentration of Au2O3 hold significant potential as materials for NIR lasers.

Enhancing the inherent NIR photoluminescence in SrLaLiTeO6 through Cr3+-Yb3+ co-substitution for high performance pc-LEDs.

Until now, double perovskite tellurates have not been reported to exhibit inherent NIR photoluminescence. Therefore, the current study's revelation of inherent NIR luminescence in SrLaLiTeO6 double perovskite centered at 970 nm under 340 nm excitation is particularly intriguing. This phenomenon is attributed to the photoluminescence of Te4+ ions. This study also examines the NIR luminescence of Cr3+-Yb3+ co-doped SrLaLiTeO6. The host and SrLaLiTeO6:3%Cr3+, y%Yb3+ (y = 1, 2, 4, 6, 8, 10 mol%) were synthesized using the solid-state ceramic route. The successful incorporation of Cr3+ and Yb3+ ions into the host lattice was confirmed through XRD, Raman, and diffuse reflectance spectral analyses. Under 270 nm excitation, the photoluminescence (PL) of SrLaLiTeO6:Cr3+ exhibits a blueshift of the PL band to 965 nm due to the 4T2(4F) → 4A2g(4F) emission component of Cr3+ ions. The excited-state lifetime of SrLaLiTeO6:0.5%Cr3+ was measured at 36 μs, but this decreased to 26 μs as the Cr3+ concentration reached 10 mol%, primarily due to the enhancement of non-radiative energy transfer between Cr3+ ions. Incorporating Yb3+ into the system results in additional spectral lines with an enhanced intensity in the range of 970 nm to 1125 nm when excited at 270 nm. These emission lines correspond to the 2F5/2 → 2F7/2 transitions of Yb3+ ions, indicating an efficient energy transfer from Cr3+ to Yb3+. Furthermore, the study also reveals that Yb3+ emission is observed even without Cr3+ ions in SrLaLiTeO6 under 340 nm excitation, suggesting the possibility of energy transfer from the host to Yb3+ ions. The thermal stability and crystal field parameters of the synthesized phosphors are also explained in detail. To explore the potential of these phosphors in practical applications, phosphor-converted NIR LEDs were fabricated using SrLaLiTeO6, SrLaLiTeO6:3% Cr3+, and SrLaLiTeO6:3% Cr3+, 1%Yb3+.

Development of NaY9Si6O26:Yb3+ Phosphor with High Thermal Stability and Its Crystals Structure and Luminescent Properties for NIR Anti-Counterfeiting

Near-infrared (NIR) radiation has attracted considerable industrial and research interest. NIR emission has promising potential for varied applications, mostly related to the characterization of chemicals, security, pharmaceutical, medical, cosmetic, food, and agricultural industries, which contribute to the advancement of modern technology. Emission sources such as tungsten halogen lamps, light emitting diodes (LEDs) and phosphor converted LEDs (pc-LEDs) can emit in the infrared range. Among these, NIR pc-LED is considered as the most suitable emission source because it provides adequate emission, high efficiency, long lifetime and excellent durability. In recent years, studies have been conducted to adjust the emission spectrum suitable for NIR phosphors and to improve quantum efficiency in order to apply them to advanced applications and devices of pc-LEDs.Recently, it is necessary to develop a material capable of specifying the near-infrared emission wavelength of near-infrared excitation beyond ultraviolet excitation infrared for advanced anti-counterfeiting against advanced counterfeiting technology. In the present study, a rare-earth-containing compound doped with an activator was used as a host system for a near-infrared phosphor to develop suitable luminescent properties. Yb3+-doped NaY9Si6O26 phosphors were synthesized using a conventional solid-state reaction method. The main phase of the synthesized phosphor samples exhibited a hexagonal structure NaY9Si6O26 phase, and had an angular-shape with an average grain size of 1-3 μm. The NaY9Si6O26:Yb3+ phosphors showed a broad near-infrared emission from 950 to 1100 nm, which was attributed to the 2F5/2 → 2F7/2 transition of Yb3+ ions under 270 and 920 nm excitation. The excitation spectra, recorded by monitoring the emission at 985 nm, showed two bands in the ultraviolet and infrared regions The excellent thermal stability of NaY9Si6O26:Yb3+ phosphor was evident from the fact that the relative PL intensity of NaY9Si6O26:Yb3+ phosphor was 82% of the initial PL intensity at 300 °C, and the thermal degradation was negligible after cooling. These results suggest NaY9Si6O26:Yb3+ phosphors are promising next-generation candidates for advanced anti-counterfeiting applications.

Optical transition and near-infrared upconversion luminescence properties of YNbO4: Er3+, Yb3+ phosphors

Optical transition and near-infrared upconversion luminescence properties of Er3+ single-doped and Er3+, Yb3+ co-doped YNbO4 phosphors are reported. Based on the framework of Judd-Ofelt theory and modified Judd-Ofelt calculation method, the optical transition properties of Er3+ and Yb3+ ions in YNbO4: Er3+, Yb3+ sample were studied, respectively. The calculated results showed that the absorption cross-section of Er3+ ion at ∼1550 nm is larger than that at ∼980 nm in YNbO4: Er3+ phosphor. And, the absorption cross-section of 2F7/2 → 2F5/2 transition of Yb3+ in YNbO4: 15.0 mol% Er3+, 15.0 mol% Yb3+ sample was calculated to be 138.70 × 10−20 cm2. According to the emission cross section of Er3+ (4I11/2 → 4I15/2) and the absorption cross section of Yb3+ (2F7/2 → 2F5/2), the energy transfer rates from Er3+ to Yb3+ were quantitatively analyzed via the Föster-Dexter model. Furthermore, 1550 nm was selected as the excitation wavelength, the near-infrared upconversion emission spectra of YNbO4: Er3+, Yb3+ samples were measured. It was found that the sample has strong emission at ∼980 nm and the emission intensity was still enhanced with the incorporation of Yb3+.

A Novel Near-Infrared Ytterbium Complex [Yb(DPPDA)2](DIPEA) with Φ = 0.46% and τobs = 105 μs.

The luminescent performances of near-infrared (NIR) lanthanide (Ln) complexes were restricted greatly by vibration quenching of X-H (X = C, N, O) oscillators, which are usually contained in ligands and solvents. Encapsulating Ln3+ into a cavity of coordination atoms is a feasible method of alleviating this quenching effect. In this work, a novel ytterbium complex [Yb(DPPDA)2](DIPEA) coordinated with 4,7-diphenyl-1,10-phenanthroline-2,9-dicarboxylic acid (DPPDA) was synthesized and characterized by FT-IR, ESI-MS and elemental analysis. Under the excitation of 335 nm light, [Yb(DPPDA)2](DIPEA) showed two emission peaks at 975 and 1011 nm, respectively, which were assigned to the characteristic 2F5/2 → 2F7/2 transition of Yb3+. Meanwhile, this ytterbium complex exhibited a plausible absolute quantum yield of 0.46% and a luminescent lifetime of 105 μs in CD3OD solution. In particular, its intrinsic quantum yield was calculated to be 12.5%, and this considerably high value was attributed to the near-zero solvent molecules bound to Yb3+ and the absence of X-H oscillators in the first coordination sphere. Based on experimental results, we further proposed that the sensitized luminescence of [Yb(DPPDA)2](DIPEA) occurred via an internal redox mechanism instead of an energy transfer process.

Ceria nanomaterials containing ytterbium: low and high concentration - luminescence analyzed in the near infrared region.

Lanthanide based ceria nanomaterials are important practical materials due to the redox properties that are useful in the avenues pertaining to technology and life sciences. Sub 10 nm spherical and highly monodisperse Ce1-xYbxO2-y (0.04 ≤ x ≤ 0.22) nanoparticles were synthesized by thermal decomposition, annealed separately at 773 K and 1273 K for 2 hours and characterized. Elemental mapping for Yb3+ doped ceria nanoparticles shows homogeneous distribution of Yb3+ atoms in the ceria with low Yb3+ content annealed at 773 K and 1273 K for 2 hours. However, clusters are observed for 773 K annealed ceria samples with high concentration of Yb3+. These clusters are not detected in 1273 K annealed nanomaterials. Introducing small amounts of Yb3+ ions into the ceria lattice as spectroscopic probes can provide detailed information about the atomic structure and local environments allowing the monitoring of small structural changes, such as clustering. The emission spectra observed at room temperature and at 4 K have a manifold of bands that corresponds to the 2F5/2 → 2F7/2 transition of Yb3+ ions. Some small shifts are observed in the Stark splitting pattern depending on the sample and the annealing conditions. The deconvolution by PARAFAC analysis yielded luminescence decay kinetics as well as the associated luminescence spectra of three species for each of the low Yb3+ doped ceria samples annealed at 773 K and one species for the 1273 K annealed samples. However, the ceria samples with high concentration of Yb3+ annealed at the two temperatures showed only one species with lower decay times as compared to the low Yb3+ doped ceria samples.

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

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

Linear and nonlinear optical properties of trigonal borate crystals K7MIn2−xYbx(B5O10)3 (M = Ca, Sr, Ba; x = 0…2) with isolated B5O10 units

Noncentrosymmetric borates K7MIn2−xYbx(B5O10)3 (M = Ca, Sr, Ba; x = 0…2) were synthesized by the solid state reaction and the crystals were successfully grown by the top seeded solution growth method using the K2O-B2O3-MF2 flux. According to Rietveld refinement, the crystal structure belongs to the noncentrosymmetric R32 space group. Also, the octahedrally coordinated In atoms are located at wide ranges ∼8 Å which may be promising for phosphor and laser applications. Samples with ytterbium show a characteristic emission band in the range of 950–1050 nm related to the 2F5/2 → 2F7/2 transition of Yb3+ ions that is commonly used for laser generation. IR, Raman and absorption spectra were obtained for the samples as well. The short cut edge of UV absorption, SHG intensity comparable with KDP and low concentration quenching of luminescence suggest that the K7MIn2−xYbx(B5O10)3 borates are promising self-frequency doubling materials.

Polymer and biopolymer organic-inorganic composites containing mixed oxides for application in energy up- and down-conversion

Organic-inorganic composites are interesting for many commercial applications— the chemical and thermal stability of inorganic oxides combined with the processability and flexibility of organic compounds and polymers provides these composites with attractive mechanical, optical, and thermal properties. In general, the desired properties cannot be found in one single constituent, but adequate association of the components affords composites with complementary properties. In this study, we have synthesized and characterized organic-inorganic composites based on the natural polymers Gellan Gum and Karaya Gum containing luminophores consisting of niobium and gadolinium mixed oxides doped with Eu3+ or Yb3+/Er3+. In this paper luminophores were prepared by a modified non-hydrolytic sol-gel route, and was obtained the organic-inorganic composites by the casting technique. The investigated how the luminophore concentration, 1.0 or 3.0% m/m of gum, affected the luminescent properties of the composites. For all the composites doped with Eu3+, the down-shifting luminescence results revealed an intense emission band at 612 nm, due to the 5D0 → 7F2 transition of Eu3+, as well as an emission band between 300 and 500 nm, attributed to polymer emission, which shifted the chromaticity coordinates toward the blue region. As for the composites doped with Yb3+/Er3+, they displayed bands at 1005 and 1535 nm, ascribed to the 2F5/2 → 2F7/2 and 4I13/2 → 4I15/2 transitions of Yb3+ and Er3+, respectively. The up-conversion luminescence results evidenced emission bands in the visible region, at 520, 550, and 655 nm, assigned to the 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 transitions of Er3+, respectively, indicating that two photons were absorbed.

Enhancement of Near‐Infrared Phosphor Luminescence Properties via Construction of Stable and Compact Energy Transfer Paths

AbstractThe rapid development of near‐infrared (NIR) spectroscopy urgently requires the exploration of NIR‐emitting phosphors with excellent luminescence properties. Herein, GaTaO4:Cr3+,Yb3+ NIR phosphor with excellent luminescence properties is reported, which exhibits ultra‐broadband NIR emission with a full width at half maximum of 300 nm, good thermal stability of 90%@423 K, and most remarkably, high internal quantum efficiency of 95.5% and external quantum efficiency of 44.79%. Such outstanding luminescence properties mainly give the credit to the unique sandwiched structure of GaTaO4:Cr3+,Yb3+, in which layers of Yb3+ ions (activator) are sandwiched between layers of Cr3+ ions (sensitizer), and hence many stable and compact Cr–Yb pairs are formed, so that the energy can be rapidly transferred from Cr3+ to Yb3+, effectively activating the characteristic f–f transition of Yb3+ that is very stable and almost independent of the temperature, and at the same time, the non‐radiative transition of Cr3+ ions can be suppressed to a certain degree. The NIR phosphor‐converted light‐emitting diodes (pc‐LEDs) are fabricated by combining GaTaO4:Cr3+,Yb3+ with blue LED chips, and the application potential is fully demonstrated by non‐destructive food detection, night vision, and vein display. The results provide novel prospects for the design of NIR‐emitting materials with desirable luminescent properties.

Near-IR Luminescence of Rare-Earth Ions (Er3+, Pr3+, Ho3+, Tm3+) in Titanate-Germanate Glasses under Excitation of Yb3.

Inorganic glasses co-doped with rare-earth ions have a key potential application value in the field of optical communications. In this paper, we have fabricated and then characterized multicomponent TiO2-modified germanate glasses co-doped with Yb3+/Ln3+ (Ln = Pr, Er, Tm, Ho) with excellent spectroscopic properties. Glass systems were directly excited at 980 nm (the 2F7/2 → 2F5/2 transition of Yb3+). We demonstrated that the introduction of TiO2 is a promising option to significantly enhance the main near-infrared luminescence bands located at the optical telecommunication window at 1.3 μm (Pr3+: 1G4 → 3H5), 1.5 μm (Er3+: 4I13/2 → 4I15/2), 1.8 μm (Tm3+: 3F4 → 3H6) and 2.0 μm (Ho3+: 5I7 → 7I8). Based on the lifetime values, the energy transfer efficiencies (ηET) were estimated. The values of ηET are changed from 31% for Yb3+/Ho3+ glass to nearly 53% for Yb3+/Pr3+ glass. The investigations show that obtained titanate–germanate glass is an interesting type of special glasses integrating luminescence properties and spectroscopic parameters, which may be a promising candidate for application in laser sources emitting radiation and broadband tunable amplifiers operating in the near-infrared range.

White upconversion emission and color tunability of Y2O3:R(R=Yb3+, Er3+, Tm3+) nanophosphors

The Y2O3:R(R = Yb3+, Er3+, Tm3+) nanophosphors were synthesized by a solvothermal method and the temperature dependence of the white upconversion emission was studied using a 975 nm LD. The upconversion emission spectra in 1 mol% Er3+/5 mol% Yb3+/xTm3+ tri-doped Y2O3 nanophosphors were sintered at 1000 °C with x from 0 to 0.5 mol%. The blue emission intensity increases increasing Tm3+ concentration from 0 to 0.5 mol%, because the Tm3+ state can be easily reached due to the 2F7/2 → 2F5/2 transition of Yb3+ near 10,000 cm−1. The Y2O3: Er3+/Yb3+/Tm3+ nanophosphors exhibit upconversion emission from white to green with increasing sintering temperature. The calculated CIE coordinates are located in the white region at a pump power of 700 mW at 1000 °C, and the color coordinates were very similar to the standard white light emission. Their upconversion process was described through energy level diagrams and results of upconversion emission spectra and pump power dependence.

Structural and spectroscopic characterization of cadmium sodium phosphate glasses doped with ytterbium for optical applications

Cadmium sodium phosphate glasses doped with ytterbium ions were fabricated by standard melt-quenching technique. The structural changes of the glass matrix doped with different ratios of Yb3+ ions were investigated via FTIR and Raman spectroscopies. The optical absorption spectra were studied via UV–Vis–NIR spectroscopy and the optical constants such as bandgaps, Urbach energies, refractive indices, and dispersion parameters were calculated. The emission cross-sections and gain spectra for 2F5/2 → 2F7/2 transition of Yb3+ ions were investigated. The high values of emission cross-sections of the studied glasses make them strong candidates for laser and amplifier applications.

Comparison of energy transfer between Terbium and Ytterbium ions in glass and glass ceramic: Application in photovoltaic

The structural and optical properties of thin layers based on 70%SiO2–30%HfO2 doped with different concentration of rare earth ions (terbium and ytterbium) have been studied with a view to integrating them in a photovoltaic cell as a spectral conversion layer in order to improve its efficiency, by using down-conversion process. These thin films were synthesized by using sol gel technique and deposited on the pure silica substrate by dip-coating method. The DC layer can be placed on the front side of a solar cell and can enhance the current by converting ultraviolet (UV) photons into a large number of visible photons.In present study two series of samples are compared, the first series corresponds to samples treated at 900 °C (glass- S) while the second series concerns samples treated at 1000 °C (glass-ceramic- SC). These series are based on 70SiO2–30HfO2 activated by different molar concentrations of rare earths [Tb + Yb]/[Si + Hf] = 7%, 9%, 12%, 15%, 17%, 19% and 21%.Photoluminescence results of reference samples (without Yb3+) showed an emission from 5D4 to 7FJ (J = 3, 4, 5, 6) level characteristic transitions of Tb3+, with a maximum peak in the green centered at 543.5 nm corresponding to the 5D4→7F5 transition. For the co-doped samples a clear NIR PL emission around 980 nm was detected, due to the 2F5/2→2F7/2 transition of Yb3+ ions. From luminescence decay curves of Tb3+ maximum emission peak (7F5→5D4 transition at 543.5 nm) we have identified the energy transfer efficiency. The quantum efficiency increases by increasing the total [Tb + Yb] concentration. The most significant yield was achieved with [Tb + Yb]=19%, the maximum quantum transfer efficiency obtained was 190% for glass-ceramic samples and 161% for glassy one.

Efficient near-infrared luminescence and energy transfer mechanism in Ca3Al2O6: Ce3+, Yb3+ phosphors

Solar cells have been extensively studied as a means of green energy converters in recent decades, especially the silicon solar cells. However, the energy efficiency of crystalline solar cells is very low, which is due to the reason that they have a good absorption in 800–1100 nm region but a bad absorption in 300–500 nm region. Based on this, a series of Ce3+-Yb3+ codoped Ca3Al2O6 samples are synthesized by the conventional solid state method in reduced atmosphere. Energy transfer process from Ce3+ to Yb3+ is affirmed by the characterizations of photoluminescence, photoluminescence excitation spectra and decay curves in different temperatures. The photoluminescence intensity and lifetime of Ce3+ decrease with the increase of Yb3+ content. And as the temperature increases, the energy transfer efficiency increases. These results demonstrated that the near-infrared luminescence from 2F5/2 to 2F7/2 transition of Yb3+ is implemented via a multi-phonon assisted energy transfer process in the Ce3+-Yb3+ ions pair. These phosphors exhibit broadband absorption in the ultraviolet region with efficient near-infrared emission (centering at 976 nm), which has better spectral response for crystalline Si solar cells. The obtained results illustrated that the phosphors have potential applications as spectral conversion materials to enhance the performance of crystalline Si solar cells.

Optical gain based on NaYF4: Er3+, Yb3+ nanoparticles-doped polymer waveguide under convenient LED pumping

The relative optical gains at three near infrared wavelengths (1550 nm, 1064 nm, and 980 nm) were achieved in NaYF4: Er3+, Yb3+ nanoparticle-doped SU-8 waveguides when using two low-cost light-emitting diodes (LEDs) instead of traditional 980 nm semiconductor laser as pump source. The polymer waveguides were fabricated by one-step photolithography process. The fluorescence bands around 1550 nm and 1000 nm wavelengths due to the 4I13/2 → 4I15/2 transition of Er3+ ions and 2F5/2 → 2F7/2 transition of Yb3+ ions were observed under the excitation of 405 nm and 520 nm LEDs. By using the vertical top pumping mode of LEDs, the relative gains of 4.2 dB, 1.7 dB, and 2.1 dB at 1550 nm, 1064 nm, and 980 nm wavelengths were achieved, respectively, on a 10-mm-long waveguide.

A NIR to NIR rechargeable long persistent luminescence phosphor Ca2Ga2GeO7:Yb3+,Tb3+

Near infrared to near infrared (NIR–NIR) photo-stimulated persistent luminescence (PSPL) has shown excellent potential in high-resolution bioimaging for deep tissues. However, the PSPL in NIR-Ⅱ region (900–1700 nm) is still lacking. In this work, Ca2Ga2GeO7:Yb3+,Tb3+ (CGGYT) phosphor with unique low-dimensional crystal structure was synthesized by high-temperature solid–state reaction. Thanks to the carriers transferring from deep traps to shallow ones induced by low energy light, the 978 nm PSPL originating from 2F5/2 to 2F7/2 transition of Yb3+ induced by multimode stimulating (980 nm or WLED) is successfully realized after pre-excited by UV lamp. The NIR PSPL of the specimen can be repeatedly stimulated after placed in dark for 12 h. Moreover, the results indicate that codoping with Tb3+ can significantly enhance the NIR-II PSPL owing to the quantum cutting persistent energy transfer (QC PET) from Tb3+ to Yb3+. Our study points to a new direction for the future development of multimode PSPL materials for bioimaging or multimode optical storage applications.

Down-conversion of YOF: Pr3+, Yb3+ phosphor

Abstract The photoluminescence (PL) of yttrium oxyfluoride (YOF) samples co-doped with praseodymium (Pr3+) and ytterbium (Yb3+) was investigated for possible down-conversion (DC) applications for c-Si solar cells (SCs). The optimum infrared (IR) emission obtained through DC was recorded with a Yb3+ content of 2% and a Pr3+ content of 0.3% and this was within the effective response range for Si SCs. YOF:Pr3+, Yb3+ samples were synthesized by the pyrolysis method with trifluoroacetate as precursor. The X-ray diffraction patterns indicated a crystalline phase of stoichiometric rhombohedral YOF (space group: R 3 ‾ m (166)) after annealing at 900 °C. X-ray photoemission spectroscopy's high resolution peak fits for the high concentration YOF: 0.3 mol % Pr3+, 6 mol % Yb3+ co-doped sample revealed two Pr oxidation states, Pr3+ and Pr4+. The presence of Pr4+ was due to the annealing in ambient air. The Pr3+ visible (VIS) emission's excitation spectra showed an intense 4f-5d band of Pr3+ at 250 nm accompanied with weaker 4f-4f peaks at 456, 470 and 483 nm. The VIS green PL emission was due to the 4f-4f [3P0 → 3H4] and [3P0 → 3F2] transitions at 498 nm and 659 nm, respectively. Quenching of the Pr3+ green emission was due to the energy transfer to Yb3+ ions through the cross-relaxation mechanism with a dipole-dipole interaction. The Yb3+ IR emission's excitation spectrum revealed a new band at 225 nm that overlapped with the 4f-5d band of Pr3+. The band at 225 nm was ascribed to the charge transfer band of Yb3+ due to electrons transferred from the O2− 3p6 level to the 4f13 level of Yb3+. Excitation with 250 nm showed multi-narrow peaks in the IR range between 885 nm and 1120 nm that corresponded to the Pr3+ 3P0 → 1G4 and 1D2 → 3F3, 3F4 transitions and to the 2F7/2 → 2F5/2 transition of Yb3+. Upon excitation of 225 nm, the IR emission showed only emission of Yb3+ transitions with almost no traces of Pr3+ emission. The decay times for VIS and IR emissions were calculated to be in the microseconds range.