Near infrared quantum cutting in Yb3+-doped NaY(WO4)2 phosphor with a high quenching concentration

The near infrared quantum cutting phenomenon has been demonstrated in Yb3+-doped NaY(WO4)2 phosphor. The phosphor shows intense absorptions in the range of 250-330 nm, and intense near infrared emission is obtained via cooperative energy transfer from the host to Yb3+, which involves the emission of two near infrared photons around 1000 nm from an absorbed ultraviolet photon. Decay curves of the host emission around 480 nm have been measured, and the calculated energy transfer efficiency turns out to be as high as 81.6% at 40 mol% Yb3+ doping. Besides, infrared emission intensities increase with increasing Yb3+ concentration until the doping gets larger than 40 mol%. The excellent luminescence properties of the Yb3+-doped NaY(WO4)2 phosphor demonstrate its potential application as a better quantum cutting layer to enhance the energy efficiency of solar cells.     

Photoluminescence of Eu3+-doped LaPO4 nanocrystals synthesized by combustion method

Eu³⁺-doped LaPO₄ nanocrystals were synthesized for the first time by a combustion method with urea as a fuel calcined at 700 °C. The diffraction profile of the obtained sample was indexed as a monoclinic monazite-structure by X-ray diffraction (XRD) data. The obtained nanocrystals appeared to be short rod-like with diameters of 5–10 nm and lengths of 20–70 nm. The luminescence intensities of Eu³⁺-doped LaPO₄ nanocrystals were found to be strongly dependent on the quantities of urea added and the concentration of Eu³⁺.     

Spectroscopic studies of Sm3+-doped phosphate glasses

Optical properties of Sm³⁺ ion in phosphate glassy matrices were studied. The absorption, fluorescence, excitation spectra and decay patterns were obtained at room temperature. The oscillator strengths of the transitions betweenJ manifolds were calculated using Judd-Ofelt theory and compared with the ones obtained experimentally. Various laser intensity parameters such as J-O parameters, radiative transition probabilities, lifetimes, branching ratio, and integrated absorption cross-section were evaluated. Radiative lifetimes of the excited states were determined and used to obtain nonradiative transition rates and quantum yields. Integrated intensity and dynamics of the fluorescence originating from the excited states were also studied as a function of Sm³⁺ concentration.     

Spectroscopic properties of Sm3+-doped oxy-fluoride powders with various Sm3+ concentration and sintering temperature

Sm³⁺-doped oxy-fluoride (OFSm) powders are prepared by the melt quenching technique and characterized using FE-SEM, optical absorption and emission techniques. Spectroscopic properties of Sm³⁺-doped oxy-fluoride powders with different Sm³⁺ concentration and sintering temperature are presented and discussed by using the absorption, emission measurements. The Judd–Ofelt intensity (J–O) parameters (Ω_λ, where λ = 2, 4 and 6), measured from the experimental oscillator strengths of the absorption spectra, are used to evaluate the radiative parameters of the fluorescence transitions. Intense orange emission can be obtained when excited with 325 nm wavelength by increasing the sintering temperature to 1400 °C. Ratio of fluorescence intensities arising from the two closing lying ⁴F_3/2 and ⁴G_5/2 levels is studied, concentration quenching has been noticed beyond 2 mol% of Sm³⁺ ions concentration. The excellent spectroscopic properties along with the outstanding thermal stability suggest that the OFSm03 powders may become an attractive laser material to exhibit efficient visible lasing emission in the orange spectral region.     

Structural and color tunable properties in Sm3+/Eu3+-doped Ca3Bi(PO4)3 phosphor for solar cell and w-LED applications

Journal of Materials Science: Materials in Electronics - Crystalline eulytite-type Ca3Bi(PO4)3 (CBP) phosphors activated with Sm3+ and combination of Sm3+ & Eu3+ ions have been prepared by...     

Emission analysis of Sm3+:Ca4GdO(BO3)3 powder phosphor

This paper reports on the spectral analysis of reddish orange color luminescent Sm³⁺:Ca₄GdO(BO₃)₃ powder phosphor. This phosphor powder has been synthesized by a solid state reaction method. Emission spectrum of it has shown four emission transitions of ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, 9/2, 11/2) and among them, the transition ⁴G_5/2 → ⁶H_7/2 displays the reddish orange (605 nm) color. Lifetimes of three emissions (⁴G_5/2 → ⁶H_{J=5/2, 7/2 & 9/2}) have been computed based on the measured decay curves. Besides the measurement of emission spectrum of this material, its nature and structural details have also been investigated from XRD, SEM and FTIR studies.     

掺Ho^3＋钛酸锶钡薄膜的结构及发光性能研究

采用溶胶-凝胶法制备了1mol%、3mol%、5mol%、8mol%Ho3 掺杂的Ba0.65Sr0.35TiO3薄膜,研究了薄膜的表面AFM、XRD谱,光学透射谱和光致发光谱.结果表明:Ho3 浓度从1mol%增加到8mol%时,BST薄膜的晶格常数先增大后减小;位于615、650和750nm处的发光,分别对应5F3→5F7、5F5一fF8和5S2、5F4一5F7的跃迁,发光谱和5S2,5F4的寿命谱分析表明,在Ho3 浓度为3mol%时三个发光带强度均最大.并分析了Ho3 与Ba2 /Sr2 /Ti4 的离子位置替代机制及交叉弛豫机制.     

Synthesis and luminescent properties: Mn4+-doped Sr3NaNbO6 phosphor with far-red emission

Journal of Materials Science: Materials in Electronics - The unique luminescence properties of far-red emitting materials make them important components in the phosphor-converted LEDs (pc-LEDs) for...     

Upconversion fluorescence in Sm3+-doped zinc phosphate glassy matrix

The mechanism governing the upconversion fluorescence from the ⁴G_5/2 level of Sm³⁺ ion has been investigated in zinc phosphate glass matrices under infrared (1.06?µm) laser excitation. This visible emission is centred at 590?nm and corresponds to the ⁴G_5/2?→?⁶H_7/2 transition. The dependence of the integrated intensity on the excitation power confirms that this emission is due to the three-photon absorption process and is in agreement with the existing theory. The intensity of the upconversion fluorescence has a cubic dependence on the excitation power. An absolute upconversion efficiency of about 10^?7 was obtained for the sample doped with 0.5?wt% Sm³⁺ ions. A quantitative estimate of the number of photons leaving the sample was also determined.     

掺钐聚合物光纤的光辐射跃迁特性

制备了掺钐螯合物的阶跃型聚合物光纤,研究了螯合物Sm(DBM)3(TOPO)2掺杂的聚甲基丙烯酸甲酯(PMMA)的吸收光谱、激励光谱和发射光谱.根据Judd-Ofelt(J-O)理论,从吸收光谱获得了光学跃迁的强度参数Ω2、Ω4、Ω6分别为18.53×10-20 cm2、2.87×10-20 cm2、3.71×10-20cm2.用光学强度参数计算了激发态4G5/2的辐射跃迁几率(536.19s-1)和辐射寿命(1865μs);同时,计算了4G5/2→6HJ'跃迁的受激发射截面和4G5/2→6FJ'、6HJ'的荧光分支比.分析表明,Sm(DBM)3(TOPO)2掺杂的PMMA可望用于聚合物光纤激光器和放大器.     

Visible quantum cutting through downconversion in Eu3+-doped K2GdZr(PO4)3 phosphor

K₂Gd_1?xZr(PO₄)₃:Eu_x³⁺ (0.02 ≤ x ≤ 0.1, x is in mol.%) were prepared by solid-state reaction method and their photoluminescence properties were investigated in ultra-violet (UV) and vacuum ultra-violet (VUV) region. The phenomenon of visible quantum cutting through downconversion was observed for the Gd³⁺–Eu³⁺ couple in this Eu³⁺-doped K₂GdZr(PO₄)₃ system. Visible quantum cutting, the emission of two visible light photons per absorbed VUV photon, occurred upon the 186 nm excitation of Gd³⁺ at the ⁶G_J level via two-step energy transfer from Gd³⁺ to Eu³⁺ by cross-relaxation and sequential transfer of the remaining excitation energy. The results revealed that the efficiency of the energy transfer process from Gd³⁺ to Eu³⁺ in the Eu³⁺-doped K₂GdZr(PO₄)₃ system could reach to 155% and K₂GdZr(PO₄)₃:Eu³⁺ was effective quantum cutting material.     

Emission features of LiBaBO3:Sm3+ red phosphor for white LED

A novel red phosphor, LiBaBO₃:Sm³⁺, was synthesized by solid state reaction, and its emission properties were studied. The excitation and emission spectra indicate that this phosphor can be effectively excited by ultraviolet (UV) 345, 373 and 404 nm light, and exhibit a satisfactory red performance (597 nm), nicely, fitting in with the widely applied UV LED chip. The emission intensity of LiBaBO₃:Sm³⁺ phosphor varies with increasing Sm³⁺ concentration, and occurs to concentration quenching, and the concentration self-quenching mechanisms are the d-d interaction by Dexter theory. Emission intensity of LiBaBO₃:Sm³⁺ phosphor was enhanced by doping charge compensation Li⁺, Na⁺, K⁺, and the emission intensity of doping Li⁺ is higher than that of Na⁺ or K⁺.