Co-doped Y2O3 Research Articles

Y2O3: Eu3+, Tb3+ spherical particles based anti-reflection and wavelength conversion bi-functional films: Synthesis and application to solar cells

In this study, Eu3+ and Tb3+ co-doped Y2O3 particles were prepared via the simple, cost-effective urea homogeneous precipitation method without additives. The chosen particles were added in the SiO2 sols to get anti-reflection (AR) and wavelength conversion bi-functional films. Careful investigations were carried out to find the optimum preparation conditions and proper morphology. SEM images showed that the particle sizes reduced as metal ion/urea ratio decreased. Additionally, the extracted particles turned from sphere to lamellar type when the deionized water, which was used as solvent, reduced to a certain extent. The mechanisms of the morphology formation and diversification were proposed as well. The as prepared materials can convert UV region photos to visible photons between 460nm and 640nm, which just matched the spectral response of most solar cells. The spherical sample showed better luminescence performance than the one with lamellar morphology. In addition, the optical transmittance spectra indicated that the films adding spherical particles had better anti-reflective performance, and the best adding amount was 0.08g. Finally, As a proof-of-concept application, the as prepared bi-functional films were used to test the standard monocrystalline silicon solar cell assembled with anti-reflection and wavelength conversion bi-functional films photoelectric conversion properties. As a result, the as prepared bi-functional films could effectively improve the photoelectric conversion efficiency by0.23% compared to pure SiO2 AR coating film and 0.55% compared to glass.

Y2O3∶Bi,Yb减反转光薄膜的制备及其性能研究

Y₂O₃∶Bi,Yb减反转光薄膜的制备及其性能研究

Effect of the Li+ ion on the multimodal emission of a lanthanide doped phosphor

The present study probes the multimodal emission: upconversion, photoluminescence and quantum cutting processes in a Ho3+/Yb3+ co-doped Y2O3 phosphor and further examines the impact of the Li+ ion on the multi-modal emission, for the first time.

Enhancement of the upconversion luminescence in Y2O3:Er3+ powders by codoping with La3+ ions

Infrared-to-visible upconverted luminescent spectra of Er3+ and La3+ codoped Y2O3 powders are investigated. By introducing La3+ ions, the upconversion green radiation is found to be greatly enhanced when compared with the powders with La3+ absent. Such enhancement can be attributed to the modification of the local symmetry surrounding the Er3+ ion, which benefits the intra-4f transitions of Er3+ ion, and the decreasing interaction between Er3+ ions, which suppresses the energy transfer process F7/24+I411/2→F49/2+F49/2.

Structural characterizations and intense green upconversion emission in Yb3+, Pr3+ co-doped Y2O3 nano-phosphor

We report the structural and optical properties of Yb3+, Pr3+ co-doped Y2O3 nano-phosphor synthesized through solution combustion method. The structural studies reveal the nano-crystalline structure of the sample. The energy dispersive spectroscopy (EDS) measurements confirm the presence of Y, O, Pr and Yb elements in the sample. Fourier transform infrared studies show the vibrational features of the samples. The fluorescence spectra of the samples have been monitored on excitation with 976nm and the intense green upconversion emission observed at 552nm is due to 3P0→3H5 electronic transition. The concentration of Pr3+ ion in the sample is optimized and the fluorescence intensity is maximum at 0.08mol% of Pr3+. The power dependence studies reveal the involvement of two photons in the emission process. The possible mechanism of upconversion has been discussed on the basis of schematic energy level diagram. The sample annealed at higher temperature enhances the fluorescence intensity up to 8 times and this enhancement is discussed in terms of the removal of optical quenching centers. The nano-phosphor can be applicable in the field of display devices and green laser.

Energy transfer mechanisms of quantum cutting near infrared luminescence in Ho3 +/Yb3 + co-doped Y2O3 transparent ceramics

Blue to near infrared quantum cutting luminescence has been achieved in the Ho3+/Yb3+ co-doped Y2O3 transparent ceramics upon the 449nm excitation. Based on the steady and the dynamic emission spectra and the energy level diagrams of Ho3+ and Yb3+, the energy transfer between Ho3+ and Yb3+ was proposed to be first via the Ho3+: 5F4, 5S2+Yb3+: 2F7/2→Ho3+: 5I6+Yb3+: 2F5/2 cross relaxation, then followed by the efficient energy transfer from Yb3+: 2F5/2 to Ho3+: 5I6, and further the enhanced Ho3+: 5I6→5I8 transition emitting at 1206nm.

Near-infrared luminescence from Y2O3:Eu3+, Yb3+ prepared by sol-gel method.

Eu3+ and Yb3+ codoped Y2O3 phosphors were synthesized by the sol-gel method. The phosphors possess absorption in the region of 300-550 nm, exhibiting an intense NIR emission of Yb3+ around 1000 nm, which is suitable for matching the maximum spectral response of c-Si solar cells. The optimum composition of Eu3+ and Yb3+ codoped Y2O3 was (Y1.94Yb0.04Eu0.02)2O3. It is observed that two-step energy transfer occurs from the 5D2 level of Eu3+ situated around (466 nm) exciting two neighboring Yb3+ ions to the 2F5/2 level (1000 nm). The down-conversion material based on Eu(3+)- Yb3+ couple may have great potential applications in c-Si solar cells to enhance their photovoltaic conversion efficiency via spectral modification.

Pr3+–Yb3+ codoped Y2O3 phosphor for display devices

Efficient green colour emitting Pr3+–Yb3+ codoped Y2O3 phosphor prepared by low temperature solution combustion process has been investigated under the excitation with a 980nm diode laser. Several upconversion emission bands from Pr3+ ions with their enhanced upconversion emission intensity have been observed on codoping of Yb3+ ions in the Y2O3:Pr3+ system. To identify the phase formation, size of crystallites and strain present in synthesized sample, X-ray diffraction pattern has been recorded. The decay curve analysis for the emitting level has also been performed along with power dependence study to clear the upconversion process. The tunability of colour emitted from the codoped phosphor has been examined which proves its suitability for display devices.

Structural morphology, upconversion luminescence and optical thermometric sensing behavior of Y2O3:Er3+/Yb3+ nano-crystalline phosphor

Infrared-to-visible upconverting rare earths Er3+/Yb3+ co-doped Y2O3 nano-crystalline phosphor samples have been prepared by solution combustion method followed by post-heat treatment at higher temperatures. A slight increase in average crystallite size has been found on calcinations verified by X-ray analysis. Transmission electron microscopy (TEM) confirms the nano-crystalline nature of the as-prepared and calcinated samples. Fourier transform infrared (FTIR) analysis shows the structural changes in as-prepared and calcinated samples. Upconversion and downconversion emission recorded using 976 and 532nm laser sources clearly demonstrates a better luminescence properties in the calcinated samples as compared to as-prepared sample. Upconversion emission has been quantified in terms of standard chromaticity diagram (CIE) showing a shift in overall upconversion emission of as-prepared and calcinated samples. Temperature sensing behaviour of this material has also been investigated by measurement of fluorescence intensity ratio (FIR) of various signals in green emission in the temperature range of 315 to 555K under 976nm laser excitation.

Efficient monochromatic red, green, and blue up-converted luminescence from Yb3+-doped micro-phosphors co-doped with Er3+ or Tm3+ ions

Yb3+-doped YVO4 and Y2O3 micro-phosphors co-doped with Tm3+ or Er3+ ions were prepared using a solid-state reaction method without the use of additional flux. Analysis of their crystalline properties indicates essentially complete inter-diffusion of the dopant ions into the host crystal with no evidence of impurity phases. The luminescence up-conversion properties of the micro-phosphors were investigated using 980nm laser diode excitation. Blue up-converted luminescence centred at 474nm associated with the 1G4→3H6 transition of Tm3+ is produced by the Tm3+/Yb3+ co-doped YVO4 phosphor, with an overall efficiency of luminescence up-conversion of 1.3%. The Er3+/Yb3+ co-doped YVO4 micro-phosphor produced two green up-converted luminescence emission bands centred at 526nm and 554nm corresponding to the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3+, respectively, with a total efficiency of up-converted luminescence of 6.6%. In contrast with the green-emitting Er3+/Yb3+ co-doped YVO4-based phosphor, Er3+/Yb3+ co-doped Y2O3 micro-phosphors were produced displaying almost exclusively intense red up-converted luminescence associated with the 4F9/2→4I15/2 transition of Er3+, with efficiencies of luminescence up-conversion up to 14%. Micro-phosphors were produced for which the blue, green and red up-converted luminescence in each case accounts for >94% of the total up-converted luminescence emission.

Observation of multi-mode: Upconversion, downshifting and quantum-cutting emission in Tm3+/Yb3+ co-doped Y2O3 phosphor

Micro-crystalline Y2O3 phosphor co-doped with Yb3+/Tm3+ has been synthesized and characterized. The phosphor material gives efficient multimodal emission via downshifting (DS), upconversion (UC), and downconversion (DC)/quantum cutting (QC) luminescence processes. Cross relaxation and co-operative energy transfer (CET) have been ascribed as the possible mechanism for QC; as result of which a UV/blue photon absorbed by Tm3+ splits into two near infrared photons (wavelength range 950–1050nm) emitted by Yb3+. The Yb3+ concentration dependent ET efficiency and QC efficiency has also been evaluated. Such multi-mode emitting phosphors could have potential applications in increasing the conversion efficiency of solar cells via spectral modification.

Controlled synthesis and defect dependent upconversion luminescence of Y2O3: Yb, Er nanoparticles

Er3+ and Yb3+ co-doped Y2O3 nanoparticles have been prepared by using a coprecipitation method followed by a post-thermal-treatment, in which a surfactant (cetyltrimethylammonium bromide, CTAB) plays an important role in the size-controlling and upconversion luminescence tuning. The green (2H11/2, 4S3/2 → 4I15/2) and red emission (4F9/2 → 4I15/2) intensity can be effectively tuned by varying the surfactant concentration, which can induce the defects in the as-obtained products. The probability of quenching and nonradiative relaxation from 4F7/2, 2H11/2, and 4S3/2 to 4F9/2 could be increased as the number of defects introduced by the surfactant increases, and thus the ratio of red to green emission is also changed. The upconversion mechanism has been analyzed and discussed, which may be a new complement for upconversion luminescence.

Efficient visible upconversion luminescence in Er3+ and Er3+/Yb3+ co-doped Y2O3 phosphors obtained by solution combustion reaction

Combustion derived Er3+ -doped Y2O3 and Er3+/Yb3+co-doped Y2O3 powders have been characterized by X-ray diffraction, energy dispersive X-ray analysis, Fourier transform infrared spectroscopy and laser excited spectroscopy. Formation of Y2O3 phosphor was confirmed by X-ray diffraction and energy dispersive X-ray analysis. The vibrational properties of Y2O3 powder was studied by Fourier transform infrared spectroscopy. The luminescence spectra of Er3+ -doped and Er3+/Yb3+ co-doped Y2O3 powders were studied under 379nm excitation. The strong up-conversion luminescence for Er3+ -doped and Er3+/Yb3+ co-doped Y2O3 powders have been observed under 978nm laser excitation. The effect of Yb3+ addition on optical and luminescence properties of Er3+:Y2O3 powders were studied. The ratio of red to green intensity has been enhanced when Er3+ -doped Y2O3 is co-doped with Yb3+ ions. The effect of co-doping of Yb3+ ions on the visible luminescence intensity of Er3+ has been studied and the mechanism responsible for the variation in the green and red intensity is discussed.

Band gap and trapping parameters of color tunable Yb3+/Er3+ codoped Y2O3 upconversion phosphor synthesized by combustion route

This paper reports the structural, optical and luminescence properties of Yb3+/Er3+ codoped Y2O3 phosphor synthesized by combustion method. The prepared phosphor was characterized by X-ray diffraction (XRD). XRD studies confirm the body-centered cubic structure of the phosphor. The optical properties such as diffuse reflectance (DR), photoluminescence and thermoluminescence were studied. DR spectra were used to determine the bandgap of the phosphor. Mechanism of upconversion by two-photon and energy transfer processes are interpreted and explained. The color coordinates were measured and the color tunability was analyzed as a function of the 980 nm excitation source power. Different trapping parameters associated with the glow peak were calculated by various glow curve methods.

Er3+-Yb3+ and Eu3+-Er3+-Yb3+ codoped Y2O3 phosphors as optical heater

The internal optical heating in the cubic phase Er3+-Yb3+ and Eu3+-Er3+-Yb3+ codoped Y2O3 phosphors synthesized by low temperature, urea assisted combustion technique due to near infrared (NIR) diode laser excitation have been performed by monitoring the upconversion luminescence bands corresponding to the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3+ ions. The results indicate that the developed phosphor materials are of significant interest for making optical heater.

Influence of Li+ codoping on visible emission of Y2O3:Tb3+, Yb3+ phosphor

Upon 980nm diode laser excitation visible upconversion emission from the Tb3+ ions has been observed in combustion synthesized Tb3+–Yb3+ codoped Y2O3 phosphor. The intensity of upconversion as well as downconversion emission bands has been increased by codoping of Li+ ions into Tb3+–Yb3+:Y2O3 phosphor and the reason behind this increment is discussed. The pump power dependence of upconversion emission bands has shown two-photon absorption process. The cooperative energy transfer from Yb3+ to Tb3+ ions is supposed to be responsible for the upconversion emission from the Tb3+ ions on near infrared excitation. The calculated colour coordinates indicate the purity of intense green emission from present phosphor which is suitable for various photonic applications.

Influence of morphology and Yb3+ concentration on blue and red luminescence of uniform cube-like Y2O3:Yb3+/Tm3+ particles

Well-dispersed cube-like Y2O3:Yb3+/Tm3+ particles have been prepared via solvothermal route using carbon microspheres as template followed by a heat treatment. X-ray diffraction (XRD) results demonstrate that all the diffraction peaks of the samples can be well indexed to the pure cubic phase of Y2O3. SEM images reveal the existence of some rough pores on the surface of cubic Y2O3:Yb3+/Tm3+ particles. Intense blue emission (1G4 → 3H6) and weak red emission (1G4 → 3F4, 3F2,3 → 3H6) of Tm3+ were observed for the Yb3+ and Tm3+ co-doped Y2O3 particles under 975 nm infrared excitation. The results show that the integrated intensity of visible emission strongly depends on the uniform and well-dispersed morphology and the concentration of Yb3+ ions. Well-dispersed cube-like Y2O3:Yb3+/Tm3+ particles with rough surface can remarkably increase the blue and red emission intensity of Y2O3:Yb3+/Tm3+ particles, which might have potential application in the fields of infrared detection, advanced flat panel displays and biological fluorescent labeling.

Improving pure red upconversion emission of Co-doped Y2O3:Yb3+–Er3+ nanocrystals with a combination of sodium sulfide and surfactant Pluronic-F127

Nanocrystals of Y2O3:Yb3+–Er3+ (2:1mol% Yb3+:Er3+) were prepared by a novel precipitation technique using Na2S and Pluronic-F127 (PF127) surfactant. Crystal structure, particle size, red emission intensity and fluorescence decay lifetimes were determined using microscopy and spectroscopy techniques. TEM analysis indicates that the average particle size ranged from 40 to 70nm. The nanocrystals showed a strong red emission band centered at 663nm after excitation at 970nm. The upconverted signal intensity was improved 250% with an optimum concentration of Na2S (0.48M) and PF127 (0.1mM). The improvement was explained in terms of the reduction of surface contaminants as well as the cubic crystalline phase of the parent Y2O3 material. Interestingly, the formation of sulfates (SO42−) is faster than that of O–H, which is responsible for quenching the red and green emissions. The results suggest that Na2S and PF127 are good candidates for surface passivation, especially when used in conjunction. The preparation of Y2O3:Yb3+–Er3+ using Na2S with strong red emission band was produced at a lower cost than that of other sulfuration processes.

Comparative study of Er3+ and Tm3+ co-doped YOF and Y2O3 powders as red spectrally pure upconverters

We prepared Er3+ and Tm3+ co-doped yttrium oxyfluoride (YOF) powder by combustion synthesis and we observed that under near-infrared (λ=980nm) laser excitation the characteristic green (2H11/2, 4S3/2→4I15/2) emission of Er3+ was suppressed by energy transfer (ET) mechanisms between Tm3+ and Er3+. The ET process observed in YOF was much more efficient than that observed in standard Y2O3 powder prepared under similar conditions. YOF combines the superior mechanical and thermal properties of oxides with low phonon energy of fluorides. Our results show that this material is a serious candidate for use as a red upconversion phosphor.

Energy transfer between Tb3+ and Eu3+ in co-doped Y2O3 nanocrystals prepared by Pechini method

Tb3+ and Eu3+ co-doped Y2O3 nanoparticles with a volume-weighted average size of about 30 nm were synthesized via simple Pechini-type sol–gel process. The growth of monocrystalline nanoparticles is investigated via XRD and TEM analysis. The study of energy transfer between Tb3+ and Eu3+ ions was carried out by means of PL, PLE, and photoluminescence decay analyses. The energy transfer from Tb3+ to Eu3+ is efficient and we show how a resonant type via a dipole–dipole interaction is the most probable mechanism. We compared the energy-transfer efficiencies calculated from the intensities and from the lifetimes of \({}^5\hbox{D}_4 \longrightarrow ^7\hbox{F}_5\) transition of Tb, showing the presence of two populations of Tb, with different local surroundings, in the matrix. Furthermore, the critical distance between Tb3+ and Eu3+ ions has been calculated by means of different theories, from a new probabilistic approach based on the discretization of the theory of Chandrasekhar about the distribution of the nearest neighbors in a random distribution of particles, and from the PL data, suggesting a value of about 7 A.