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1.
硅材料带隙与太阳光子光谱的失配导致了比较严重的光子损失,大大降低了硅太阳能电池的效率。为了减少入射光子的损失,可以利用具有近红外量子剪裁效应的光谱转换材料来提高硅太阳能电池的效率。本研究采用溶胶凝胶法制备了Sr_3Al_2O_6∶Tb~(3+),Yb~(3+)荧光粉,并研究了其近红外量子剪裁效应。实验结果表明:在320 nm的紫外光激发下,Sr_3Al_2O_6∶Tb~(3+),Yb~(3+)荧光粉发射出Tb~(3+):5D4→~7F_j的可见光;另外,由于Tb~(3+)、Yb~(3+)离子之间的合作能量传递,得到了Yb~(3+):~7F_(5/2)→7F7/2的近红外发光。荧光寿命衰减证明Tb~(3+)到Yb~(3+)之间的确存在合作能量传递,而且存在量子剪裁效应,其中,能量传递效率为35.9%,量子剪裁效率为135.9%。由于Yb~(3+)的发射光谱与硅太阳能电池的吸收匹配,Sr_3Al_2O_6∶Tb~(3+),Yb~(3+)荧光粉有可能作为潜在的光谱转换材料应用于硅太阳能电池以提高其光电转换效率。  相似文献   

2.
The materials Sr3−x(VO4)2:xYb were successfully synthesized by co-precipitation method varying the concentration of Yb3+ ions from 0 to 0.06 mol. It was characterize by powder X-ray powder diffraction (XRD) and surface morphology was studied by scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied by spectrophotometers in near infra red (NIR) and ultra violet visible (UV–VIS) region. The Yb3+ ion doped tristrontium vanadate (Sr3(VO4)2) phosphors that can convert a photon of UV region (349 nm) into photons of NIR region (978, 996 and 1026 nm). Hence this phosphor could be used as a quantum cutting (QC) luminescent convertor in front of crystalline silicon solar cell (c-Si) panels to reduce thermalization loss due to spectral mismatch of the solar cells. The theoretical value of quantum efficiency (QE) was calculated from steady time decay measurement and the maximum efficiency approached up to 144.43%. The Sr(3−x) (VO4)2:xYb can be potentiality used for betterment of photovoltaic (PV) technology.  相似文献   

3.
In the present paper, we investigate the near-infrared (NIR) luminescence of Tb3+–Yb3+ codoped lanthanum borogermanate (LBG) glasses under visible and ultraviolet light excitation. The results indicate that NIR quantum cutting occurs through cooperative energy transfer from Tb3+ to Yb3+ ions when only 4f 8 levels of Tb3+ ions are excited in the wavelength region of 300–490 nm. The highest quantum efficiency under the excitation 5 D 4 level of Tb3+ at 484 nm is 146%. Ultraviolet excitation that populates the charge transfer band (CTB) of Yb3+ near 270 nm does not result in quantum cutting as the fast nonradiative decay from CTB to 2 F 5/2 level dominates. These materials are expected to be used as a converting layer for silicon solar cells to enhance their efficiency by splitting each high-energy photon into two NIR photons.  相似文献   

4.
The host sensitized near‐infrared (NIR) emitting phosphor Sr2CaMoO6:Yb3+ was fabricated by the solid state reaction method. The structural refinement and Raman spectra elucidate that Yb3+ ions preferentially occupy Ca2+ sites. The phosphor can harvest ultraviolet (UV)–blue photons and exhibits intense NIR emission at around 1012 nm with full‐width‐at‐half‐maximum of 1635 cm–1. Moreover, the absolute NIR photoluminesence quantum yield (PLQY) is estimated to be about 9%. The Sr2CaMoO6:Yb3+ phosphor may be a promising luminescence downshifting material for improving the spectral response of solar cells in the UV region. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
A NIR excitation of Er3+ doped Lithium modified tellurite (Li:TeO2) glass results in antistokes fluorescent emission near 380, 530, 551 and 654 nm (ultraviolet, green and red regions) in addition to NIR Stokes emission. The antistokes emissions are ascribed to transition from the excited 4G11/2, 4S3/2(2H11/2) and 4F9/2 levels in Er3+. The excitation involves three and two incident photons. On excitation with the green laser line at 532 nm also leads to similar emissions. The mechanisms involved in these processes are discussed on the basis of the known energy level diagram and the upconversion efficiency has been calculated. Lifetime of the 4S3/2 level has been measured. The temperature dependence of the upconversion process has also been investigated.  相似文献   

6.
RE/Yb co-doped Y2O3 transparent ceramics (RE=Er, Ho, Pr, Tm) were fabricated and characterized from the point of up-conversion luminescence. All the samples exhibit high transparence not only in near-infrared band (NIR) band but also in visible region, which ensures the output of the up-conversion luminescence. Under 980 nm excitation, green and red emissions were observed in Er, Yb:Y2O3 transparent ceramic, while green emission was detected in Ho, Yb and Pr, Yb co-doped Y2O3 transparent ceramics. In Tm, Yb co-doped Y2O3 ceramic, very intense blue up-conversion luminescence was detected. The dependence of up-conversion emission intensity on the pumping power was measured for each RE/Yb co-doped Y2O3 transparent ceramic, and the up-conversion mechanism was discussed in detail. Meanwhile, the energy transfer efficiency was calculated.  相似文献   

7.
Intense green‐emitting Li(Gd,Y)F4:Yb,Er/LiGdF4 core/shell (C/S) upconversion nanophosphors (UCNPs) with a tetragonal bipyramidal morphology are synthesized. The morphology and UC luminescence of the Li(Gd,Y)F4:Yb,Er UCNPs are significantly affected by the Li precursors, and bright UC green‐emitting Li(Gd,Y)F4:Yb,Er UCNPs with a tetragonal bipyramidal shape, i.e., UC tetragonal bipyramids (UCTBs), are synthesized using LiOH·H2O as a Li precursor. A LiGdF4 shell is grown on the Li(Gd,Y)F4:Yb,Er UCTBs, and the C/S UCNPs exhibit 4.7 times higher luminescence intensity than core UCTBs. The C/S UCNPs show a high absolute UC quantum yield of 4.6% under excitation with 980 nm near infrared (NIR) light, and the UC luminescence from the C/S UCNPs is stable under continuous irradiation with the 980 nm NIR laser for 1 h. The hydrophobic surfaces of the as‐synthesized C/S UCNPs are modified to hydrophilic surfaces by using poly(acrylic acid) (PAA) for bioimaging applications. They are applied to human cervical adenocarcinoma (HeLa) cell imaging and SK‐MEL‐2 melanoma cell imaging and in vivo imaging, including subcutaneous and intramuscular imaging, and UC luminescence images with high signal‐to‐noise ratio are obtained. Furthermore, sentinel‐lymph‐node imaging is successfully conducted with the PAA‐capped Li(Gd,Y)F4:Yb,Er/LiGdF4 C/S UCNPs under illumination with NIR light.  相似文献   

8.
An efficient near-infrared (NIR) quantum cutting (QC) by converting ultraviolet into NIR via cooperative downconversion (DC) for the (Nd3+, Yb3+) couple in CaWO4 is studied since efficient two-step energy transfer occurs from the 4G9/2 level of Nd3+ to two neighboring Yb3+:2F5/2 level. The authors have analyzed the measured luminescence spectra and decay lifetimes for different Yb3+ concentrations and proposed a mechanism to rationalize the DC effect. The maximum quantum efficiency (QE) of Nd3+ is up to 164.03 %. Application of the broadband NIR-QC phosphors might enhance the performance of silicon-based solar cells.  相似文献   

9.
We propose the concept of the infrared detection and photon energy up-conversion in the devices using the integration of the graphene layer infrared detectors (GLIPs) and the light emitting diodes (LEDs) based on van der Waals (vdW) heterostructures. Using the developed device model of the GLIP-LEDs, we calculate their characteristics. The GLIP-LED devices can operate as the detectors of far- and mid infrared radiation (FIR and MIR) with an electrical output or with near-infrared radiation (NIR) or visible radiation (VIR) output. In the latter case, GLIP-LED devices function as the photon energy up-converters of FIR and MIR to NIR or VIR. The operation of GLIP-LED devices is associated with the injection of the electron photocurrent produced due to the interband absorption of the FIR/MIR photons in the GLIP part into the LED emitting NIR/VIR photons. We calculate the GLIP-LED responsivity and up-conversion efficiency as functions the structure parameters and the energies of the incident FIR/MIR photons and the output NIR/VIR photons. The advantages of the GLs in the vdW heterostructures (relatively high photoexcitation rate from and low capture efficiency into GLs) combined with the reabsorption of a fraction of the NIR/FIR photon flux in the GLIP (which can enable an effective photonic feedback) result in the elevated GLIP-LED device responsivity and up-conversion efficiency. The positive optical feedback from the LED section of the device lead to increasing current injection enabling the appearance of the S-type current-voltage characteristic with a greatly enhanced responsivity near the switching point and current filamentation.  相似文献   

10.
A distinct enhancement of upconversion luminescence from core to core/shell (C/S) structure under low flux near infrared (NIR) excitation at 976 nm has been achieved in lanthanide (Er3+, Yb3+)-doped NaYF4 core with undoped NaYF4 shell nanoparticles (NP). A green chemistry approach has been taken to synthesize monodisperse monophasic C/S NP with the core (~20 nm) and shell (~5 nm) crystallizing into cubic phase. Hydrophobic C/S NP have been further made hydrophilic by coating a transparent SHMP layer without affecting luminescence. C/S (NaYF4: Er, Yb/NaYF4) NP integrated dye-sensitized solar cell indicated 11.9% enhancement in overall conversion efficiency under AM 1.5 conditions, due to NIR–visible spectrum modification by fluorescent NPs. The results indicate great potential of such upconverting C/S nanophosphor in solar cell applications.  相似文献   

11.
This study investigated photoluminescent properties of Sr2CaWO6:Yb3+, Na+ phosphor. The samples were successfully synthesized via a solid-state reaction method with various doping concentrations. The phosphor can efficiently absorb ultraviolet photons of 250–350 nm and transfer its absorbed photon energy to Yb3+ ions. Then subsequent quantum cutting between WO6 groups and Yb3+ ions takes place, down-converting an absorbed ultraviolet photon into two photons of 1007 nm radiations. Analyses of decay curves of different samples reveal an efficient energy transfer from WO6 groups to Yb3+ ions. Cooperative energy transfer from host to Yb3+ ions is responsible for downconversion via lifetime analysis. Quantum efficiencies were calculated, and estimated maximum efficiency reached 190%. These phosphors combine wide wavelength absorption in the ultraviolet range with high quantum efficiency, enabling potential application of efficiency enhancement of Si solar cell.  相似文献   

12.
利用共沉淀方法制备了Eu3+/Yb3+单掺和共掺的ZrO2粉体材料,研究了煅烧温度和掺杂浓度对结构和发光性质的影响。XRD结果表明:所制备单掺样品含有单斜相和四方相2种不同结构,随着热处理温度的升高,四方相向单斜相转变,经1 150℃处理后,四方相消失,呈现单一的单斜相;Yb3+离子的掺入有稳定ZrO2四方相的作用,随着掺杂浓度的增加,单斜相转变为四方相。由于晶相的不同,Eu3+处在四方相和单斜相2种发光中心,二者发光性质不同。Eu3+/Yb3+共掺后,在270 nm激发Eu3+时,观测到了Yb3+在近红外波段(980 nm)的发光,同时证实Eu3+的激发光谱和Yb3+的激发光谱相一致,表明存在Eu3+到Yb3+的能量传递,交叉弛豫和共合作能量传递过程是其可能的能量传递机理。  相似文献   

13.
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.  相似文献   

14.
In the fluorides YF3 and α-NaYF4, the trivalent praseodymium ion shows a two photon luminescence in which one ultraviolet photon (?210 nm) is converted into two visible photons.  相似文献   

15.
The Yb-doped Bi2O3–GeO2 glasses were prepared by the conventional melt quenching technique. Near-infrared (NIR) broadband emission was found at about 1024 nm, and 1330 nm (under 785 nm excitation), and the measured fluorescent lifetime was about several hundred microseconds. The emission intensity of Yb-doped Bi2O3–GeO2 glasses increased with increasing of Yb dopant in our experiments. The NIR emission should be related to Yb3+ and lower valence Bi ions.  相似文献   

16.
In this work, different compositions of lanthanum hexaboride (LaB6) and tin-doped indium oxide (ITO) nanoparticles were doped into poly(vinylbutyral) (PVB) matrix to prepare PVB/LaB6–ITO nanocomposite (PLINC) films by a solution casting method. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis (TGA) and ultraviolet–visible–near infrared spectroscopy (UV–vis–NIR) were employed to characterize the PLINCs. The TGA and UV–vis–NIR results reveal that the nanocomposite films possessed outstanding thermal stability. The temperature where 5 % weight loss of the PVB matrix was improved after the addition of LaB6 and ITO particles and the property for blocking near infrared light was also enhanced as compared with the case of pure PVB film.  相似文献   

17.
Er and Yb co-doped ZnAl2O4 phosphors were prepared by solution combustion synthesis and the identification of Er and Yb were done by energy-dispersive X-ray analysis (EDX) studies. A luminescence at 1.5 μm, due to the 4I13/24I15/2 transition, has been studied in the NIR region in Er and Yb co-doped ZnAl2O4 phosphors upon 980 nm CW pumping. Er-doped ZnAl2O4 exhibits two thermally stimulated luminescence (TSL) peaks around 174°C and 483°C, while Yb co-doped ZnAl2O4 exhibits TSL peaks around 170°C and 423°C. Electron spin resonance (ESR) studies were carried out to identify defect centres responsible for TSL peaks observed in the phosphors. Room temperature ESR spectrum appears to be a superposition of two distinct centres. These centres are assigned to an O ion and F+ centre. O ion appears to correlate with the 174°C TSL peak and F+ centre appears to relate with the high temperature TSL peak at 483°C in ZnAl2O4:Er phosphor.  相似文献   

18.
The neutral homoleptic Ln(III) complex Ln(Tp)3 (Ln=Sm, Eu, Tb, Yb; Tp=hydrotris(pyrazol-1-yl)borate) were used as dopants for the preparation of novel photoluminescent poly(methyl methacrylate) glasses indicated as Ln(Tp)3@PMMA. The doped polymers containing samarium, europium and terbium derivatives showed emission associated to ff transitions in the visible range upon excitation with UV light, while a NIR emission was obtained from Yb(Tp)3@PMMA. The maximum incident wavelength able to induce emissions from the Ln(Tp)3-doped polymers depends upon the choice of the lanthanide ion. No meaningful antenna-effect was instead observed using dysprosium as metal centre.  相似文献   

19.
Yb:Ca4YO(BO3)3 (Yb:YCOB) crystal with good quality and large size has been grown by the Czochralski method. The polarization absorption and fluorescence spectra have been measured. The laser action of the Yb:YCOB crystal has been demonstrated when it is pumped by a fiber-coupled laser diode (LD) at the wavelength of 976.4 nm. The pumping threshold is 55 mW, the light-light conversion efficiency is 58.7%, and a slope efficiency of up to 73% is thus calculated. Received: 16 December 1998 / Revised version: 4 February 1999 / Published online: 7 April 1999  相似文献   

20.
利用VUV同步辐射光源和反射式飞行时间质谱仪,在超声冷却条件下对四氯乙烯(C2Cl4)进行了光电离研究,通过测量各离子的光电离效率(PIE)曲线,得到了C2Cl4的电离势IP(C2Cl4) =(9.36±0.05)eV及C2Cl4光解离碎片离子C2Cl3+,C关键词: 真空紫外光电离 离子出现势 电离势 四氯乙烯  相似文献   

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