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 共查询到10条相似文献,搜索用时 125 毫秒
1.
We report on the short wavelength (green, blue, and ultra-violet (UV)) emission in trivalent holmium doped fluoro-zirconate fiber (Ho3+:ZBLAN) under direct and upconversion pumping. Efficient red to UV upconversion has been observed using 647 nm cw pumping by krypton ion laser. A close to cubic UV signal intensity dependence on incident red pump power was determined, confirming the three-photon character of the observed process. The responsible upconversion mechanisms were investigated and shown to be excited state absorption (ESA) via low-lying 5I7 and 5I6 sates. Dynamics of the involved excited states have been studied under pulsed laser excitation.  相似文献   

2.
A novel class of orange-red phosphors namely CaLa2ZnO5 (CLZ) doped with Eu3+ ions were prepared by adopting citrate based sol-gel method. Those were thoroughly characterized by means of XRD, SEM, Tg-DTA, photoluminescent (PL) spectral profiles. PL studies reveal that its emission intensity strongly depends on sintering temperature as well as the dopant ion (Eu3+) concentration. Eu3+ ion doped CaLa2ZnO5 phosphor has a strong excitation at 468 nm, which correspond to the popular emission line from a GaN based blue light-emitting diode (LED) chip. The influence of the preparation method on the luminescence property was studied by comparing the emission performance of phosphors prepared by sol-gel and solid-state reaction methods along with a commercial red phosphor Y2O2S:Eu3+. Thus, the intense red emission (5D0 → 7F2) of the Eu3+ doped CLZ phosphors under blue excitation suggests them to be a potential candidate for the production of white light by blue LEDs.  相似文献   

3.
Spherical and rod like nanocrystalline Nd2O3 phosphors have been prepared by solution combustion and hydrothermal methods respectively. The Powder X-ray diffraction (PXRD) results confirm that hexagonal A-type Nd2O3 has been obtained with calcination at 900 °C for 3 h and the lattice parameters have been evaluated by Rietveld refinement. Surface morphology of Nd2O3 phosphors show the formation of nanorods in hydrothermal synthesis whereas spherical particles in combustion method. TEM results also confirm the same. Raman studies show major peaks, which are assigned, to Fg and combination of Ag + Eg modes. The PL spectrum shows a series of emission bands at ∼326-373 nm (UV), 421-485 nm (blue), 529-542 nm (green) and 622 nm (red). The UV, blue, green and red emission in the PL spectrum indicates that Nd2O3 nanocrystals are promising for high performance materials and white light emitting diodes (LEDs).  相似文献   

4.
In this work we fabricated white LEDs using a blue InGaN LED precoated conjugated copolymer/quantum dots (QDs) composite (green-emitting Poly {(9,9-dioctyl-2,7-divinylenefluorenylene)-alto-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene)}/red-emitting CdSe quantum dots) as a hybrid phosphor. The emission peak wavelengths of the blue and red emissions in the spectra were 462 and 618 nm, respectively. The green-emitting polymer had two emission peaks at 515 and 543 nm. The subpeak of the copolymer (515 nm) was decreased by the absorption of QDs as the ratio of QDs increased, while the emission of the QD (618 nm) increased. Therefore, changes in the CIE-1931 coordinate, color temperature (Tc) and color-rendering index (Ra) were dependent on the QDs to copolymer ratios. The white LED of the hybrid phosphor containing 20 wt.% QDs had a luminous efficiency of 44.2 l m/W at 20 mA with a CIE-1931 coordinate, Tc and Ra of (0.3297, 0.3332), 5620 K and 75.3, respectively.  相似文献   

5.
Pr3+ doped CaBi2Ta2O9 based bismuth layered-structure oxides were synthesized by a simple solid state reaction method. The photoluminescence properties of the samples were investigated by excitation and emission spectra. Photoluminescence excitation spectra show that the samples have broad blue excitation band located at 430-510 nm, which covers the emission wavelength of commercial blue light-emitting diode (LED) chips. Upon the excitation of 450 nm light, a novel red emission centered at 621 nm of Pr doped CaBi2Ta2O9 makes it useful in the white LEDs. In addition, it was also found that the photoluminescence can been improved by partial substituting Sr for Ca. These Pr3+ doped CaBi2Ta2O9 based ferroelectrics could possibly be used as a multifunctional material for a wide range of applications, such as integrated electro-optical devices.  相似文献   

6.
Szu-po Huang  Hsin-Hung Lu  Show-An Chen   《Synthetic Metals》2009,159(19-20):1940-1943
We demonstrated a high-efficiency white polymer light-emitting diode (WPLED) based on carbazole-grafted poly(para-phenylene) (CzPPP) doped with green- and red-emitting Ir complexes as the emitting layer. The device exhibits pure white light yet with stable sharp blue (430 nm), green (512 nm), and red (613 nm) emissions and has the maximum current and external quantum efficiencies of 16.8 cd/A and 8.65%, respectively. The overall performance is resulted from the excellent shielding effect of CzPPP host to prevent back transfer of triplet energy especially from the green phosphor.  相似文献   

7.
A luminescent europium-containing copolymer, poly(MMA-MA-co-Eu(TTA)2phen), was synthesized though a reaction of EuCl3, 1,10-phenanthroline (phen), α-thenoyltrifluoroacetone (TTA) with copolymer of maleic acid (MA) and methyl methacrylate (MMA). The copolymer was characterized by FT-IR, UV–vis, gel permeation chromatograph (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. The Eu-copolymer phosphor exhibited high thermal stability and excellent photoluminescence properties, appropriate CIE chromaticity coordinates for red and a quantum yield of 24% under near-UV light excitation. It emitted intense red light at 613 nm under UV excitation at room temperature, which is attributed to the 5D0  7F2 transition of Eu(III) ions. An intense red-emitting light-emitting diode (LED) was fabricated by combining poly(MA-MMA-co-Eu(TTA)2phen) with a 395 nm-emitting InGaN chip. The results indicate that the Eu-copolymer phosphor may act as a red component for fabrication of white LEDs.  相似文献   

8.
Polyaniline (PANI) is one of the highly pursued conducting polymers in recent times owing to its excellent electrical and optical properties, better air stability and easy and cheap synthesis route. Doped PANI has been extensively investigated as a hole-injecting electrode in polymer light emitting diodes (LEDs). However, the work on doped PANI as emissive layers in polymer LEDs is quite scanty. Though there are reports on the photoluminescence characteristics of doped PANI, a detailed investigation on a comparative study of the photo luminescence in PANI doped with different dopants, which is the essence of our work, has not been carried out earlier. In the present work, we compare the photoluminescence (PL) emission intensity of PANI doped with hydrochloric acid (HCl), camphor sulphonic acid (CSA) and orthophosphoric acid, with a view to assessing the prospects of doped PANI as emissive layer in polymer LEDs. The PL emission peak is centered around 450 nm when excited at 365 nm. PANI doped with orthophosphoric acid exhibits the highest photoluminescent intensity followed by PANI doped with HCl and CSA. A comparison of the X.R.D spectra of the samples show that both HCl doped PANI and CSA doped PANI, do not show any significant crystalline nature whereas orthophosphoric acid doped PANI exhibits considerable crystallanity. The observed long-range order in orthophosphoric acid doped PANI could be a consequence of the more orderly arrangement of benzenoid and quinonoid units, resulting in enhanced PL emission intensity.  相似文献   

9.
In order to enhance luminescence properties of Eu2+-doped ternary nitride phosphor for white light-emitting diodes (LEDs), Sr2Si5N8:Eu2+ phosphors with different Eu2+ concentrations were synthesized using a multi-step heat treatment. Impurities and luminescence properties of prepared Sr2Si5N8:Eu2+ phosphors were investigated using X-ray diffraction (XRD) and photoluminescence spectroscopy. Excitation spectra of Sr2Si5N8:Eu2+ phosphor showed broad excitation bands by both UV and blue light. Emission peak positions in spectra were red-shifted from 613 to 671 nm as Eu2+ ion concentrations increased. Phosphors following a multi-step heat treatment showed excellent luminescence properties. These included high emission intensity and very low thermal quenching compared to measurements using a commercially available YAG:Ce3+ phosphor.  相似文献   

10.
BaMgAl10O17:Eu2+ (BAM) is one kind of commercial blue phosphor in fluorescent lamps, because of its efficient blue emission. A serial of phosphors BaMgAl10O17:0.1Eu2+ doped different H3BO3 concentration were prepared by solid-state reaction technique, and their photoluminescent properties were investigated. The introduction of H3BO3 broadens the excitation band of the phosphor BAM around 400 nm and enhances the emission intensity under 400 nm light excitation. The emission of the phosphor BAM doped with 6% H3BO3 has optimum blue emission, with good CIE (Commission Internationale de l’Eclairage, International Commission on Illumination) chromaticity coordinates x = 0.151, y = 0.058. Hence, the phosphor can be applied in fabrication of near-UV LED excited white light-emitting diode (LED).  相似文献   

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