最新刊期
卷 35 ， 期 8 ， 2014
- 摘要：Ce3+-and Yb3+-doped YAG powders were prepared and the energy transfer (ET) mechanism with (Ce3+)*-Yb3+ charge transfer transition in the powders was evaluated by the photoluminescence (PL), the photoluminescence excitation (PLE) and the lifetime. The possibility of the NIR emission of QC was also discussed because the 1 000 nm emission of Yb3+ just meets the largest spectral response of c-Si solar cells, which may have potential application in enhancing the conversion efficiency of c-Si solar cells.关键词：rare earth;NIR emission;energy transfer;quantum cutting123|103|3更新时间：2020-08-12
- 摘要：Tb/Eu co-doped zinc borophosphate glasses were successfully synthesized by melt quenching method. The effect of glass matrix composition and rare erath ions concentration were discussed. The structural and luminescent properties were characterized by Fourier transform infrared (FT-IR) spectra, absorption spectra, photoluminescence(PL) spectra, fluorescence lifetimes and colorimetric analysis. Eu3+ ions were partly reduced to Eu2+ during the synthesization in air. Under 380 nm excitation, white light emission was observed composited by emission at 612 nm and 590 nm for Eu3+, 544 nm and 488 nm for Tb3+, and 430 nm for Eu2+. The FT-IR spectra showed that the structure of glass matrix changed when B2O3 content increased, which affected the Eu2+/Eu3+ ratio in glass samples. The spectra results show that Eu2+ ions are donors which can transfer energy to Eu3+ and Tb3+. Lifetime analysis proved that Tb3+ ions can transfer energy to Eu3+ through nonradiative transition. The luminescence intensity and emission color can be efficiently controlled by changing glass composition and rare earth ion concentration. Optimized white light with CIE(0.3187, 0.2861) and correlated color temperature at 6 480 K was obtained when the mole fractions of Eu and Tb were both 1.5%.关键词：borophosphate glass;luminescent properties;europium;terbium;white LED111|177|3更新时间：2020-08-12
- 摘要：Tm3+/Yb3+ co-doped Y2(MoO4)3 phosphors with various Tm3+ concentrations were prepared via a traditional high temperature solid state reaction method using NH4HF2 as a flux. The microstructure analysis by means of X-ray diffraction revealed that the as-synthesized samples presented a pure phase Y2(MoO4)3. Under 980 nm excitation, intense blue, near infrared (NIR) and weak red upconversion emissions which centered at 487, 800 and 649 nm were observed, and these emissions were corresponding to the 1G4→3H6, 3H4→3H6 and 1G4→3F4 transitions of Tm3+, respectively. The upconversion luminescence mechanisms of Y2(MoO4)3:Tm3+,Yb3+ phosphors were analyzed based upon the power dependent upconversion emissions. The results show that the populations of 1G4 and 3H4 levels come from three-and two-photon energy transfer upconversion processes, respectively. The possible upconversion mechanisms for the blue, red and NIR emissions were discussed based on the energy level diagrams of Tm3+ and Yb3+. In addition, with the increase of Tm3+ concentration, all of the emission bands obviously increase firstly and then decrease, which can be attributed to the concentration quenching. Meanwhile, the intensity ratio of the blue emission and the NIR emission decreases with the increase of Tm3+ concentration.关键词：Tm3+;blue upconversion;phosphor;concentration quenching;energy transfer138|55|0更新时间：2020-08-12
- 摘要：12CaO·7Al2O3 (C12A7:Sm3+) phosphors with different Sm3+ doping concentrations were synthesized through self-propagating combustion method. Under 404 nm UV excitation, there are three dominating emission peaks observed at 565, 599 and 648 nm, corresponding to the 4G5/2→6HJ/2(J=5,7,9) transitions of Sm3+ respectively. With the increasing of Sm3+ doping concentration, the red emitting intensity exhibited a behavior that increased firstly and then decreased. The optimal Sm3+ ion concentration is 1.5% and the concentration quenching effect is due to the cross-relaxation (CR) processes between the Sm3+ ions. Through adopting mixed-phase strategy, 12CaO· 7Al2O3/5CaO·3Al2O3:1.5%Sm3+ (C12A7/C5A3:Sm3+) powders were prepared by decreasing the calcining temperature to 900℃ and the enhanced red emitting intensity was obtained. The temperature-dependent photoluminescence showed that the thermal activation energy of the mixed-phase sample is about 200 meV and its thermal stability is high.关键词：12CaO·7Al2O3;5CaO·3Al2O3;Sm3+;red emitting light;photoluminescence93|30|0更新时间：2020-08-12
- 摘要：Polymer films doped by Coumarin 500, Coumarin 540 and Rhodamine 6G dyes were fabricated on glass. The absorption spectra, fluorescence spectra and down-conversion characteristics of these films were experimentally studied using LED and xenon lamps as illumination sources. The photons from 350 nm to 550 nm can be down-converted to photons of 580 nm by these dye-doped polymer films. Higher dopant concentrations within certain range, more photons can be down-converted. Since Nd3+ in Nd3+/Yb3+ co-doped glass has a strong absorption band around 580 nm, these dye-doped polymer films are helpful to enhance absorption of blue and green light and convert them to near infrared emission of Yb3+ through resonance energy transfer. These films can be potentially used to improve the compositive photovoltaic conversion efficiency of crystalline silicon solar cells.关键词：dye;down-conversion;red shift;resonant energy transfer;photovoltaic application108|213|0更新时间：2020-08-12
- 摘要：The influence of gallium (Ga) doping on the structure of cubic MgZnO was studied by changing the doping level. Cubic Mg0.56Zn0.44O films with various Ga-doping levels were grown by metal-organic chemical vapor deposition method. The mole fraction of Ga in this experiment was 0, 2.8%, 3.1%, 3.3%, and 4.5% in MgZnO. Ga2O3, ZnO and ZnGa2O4 phase separations took place subsequently with Ga mole fraction increasing to 3.1%, 3.3%, and 4.5%. The Ga2O3 and ZnGa2O4 phase separations can be attributed to their solubilities in MgZnO, and the formation of ZnO comes from the introduction of Ga which breaks the metastable structure of cubic MgZnO.关键词：cubic MgZnO;Ga doped;crystal structure;phase separation124|162|0更新时间：2020-08-12
- 摘要：A series of blue-emission Zr(Ⅳ) complexes[Zr(NN)(DBM)3] Cl(DBM=dibenzoylmethane,NN=1,10-phenanthroline 1; 2,9-dimethyl-1,10-phenanthroline 2; 4,4'-dimethyl-2,2'-bipyridine 3;1-ethyl-2-(naphthalen-1-yl)-1H-imidazo-4,5-f-1,10-phenanthroline 4) were synthesized. The emission peaks of these complexes are all centered at 445 nm upon excitation at 355 nm, while their half-width are in the range of 36~45 nm. Under the same condition, complex 1 shows the strongest emission and highest photoluminescence quantum yield. This result attributes to its rigid structure because such structure can efficiently decrease energy loss coming from non-radiative transition. Moreover, the decomposing temperatures of complexes 1-3 are all above 200℃ indicating their excellent thermal stability. Such results suggest that complexes 1-3 can be utilized in the preparation of light-emitting device.关键词：Zr(Ⅳ) complex;blue-emission;thermal stability117|153|3更新时间：2020-08-12
- 摘要：Red phosphors of Ca0.88TiO3:0.12Eu3+ (CTE) were synthesized by solid-state method, and their structure and morphology were studied. XRD results show that CTE phosphors sintered at different temperature exhibit orthorhombic structure. The average grain size increases with the increase of sintering temperature, and their crystallization sintered at 1 300℃ is the best, which is consistent with the SEM results. CTE phosphors can be efficiently excited by near-ultraviolet light of 398 nm, and emit intensive red light with peaks around 594 nm and 616 nm corresponding to the transition 5D0→7F1 and 5D0→7F2 of Eu3+. The peak around 616 nm is stronger than that of 594 nm, showing that Eu3+ ions site at lattice without the center of inversion symmetry. The emission intensity of CTE phosphor increases with the sintering temperature, and is the highest when the sintering temperature is 1 300℃ due to higher crystallinity. Furthermore, CTE phosphors have very good thermal stability and high color purity, implying the potential to be a promising red phosphor in white light emitting diodes.关键词：phosphor;CaTiO3;photoluminescence109|101|2更新时间：2020-08-12
- 摘要：Cubic structure Mg1-xZnxO films were deposited by pulsed laser deposition method. The influence of temperature on the growth orientation and optical absorption characteristics of cubic structure Mg1-xZnxO films were studied. The preferred growth orientation of MgZnO thin films changed from (200) to (111) when the growth temperature increased from 150℃ to 700℃. The UV absorption edge of MgZnO thin film changed with the Mg/Zn ratio in MgZnO crystal lattice when the growth temperature increased from 150℃ to 600℃. When the temperature changed from 600℃ to 700℃, the grain size of MgZnO thin film increased, and the UV absorption edge of MgZnO thin film blue shifted though the Mg/Zn ratio in MgZnO crystal lattice decreased. Finally, single (200) and (111) orientation MgZnO thin films were deposited on (200) and (111) orientation MgO substrates at 300℃and 700℃, respectively.关键词：MgZnO;pulsed laser deposition;optical band gap;growth temperature104|119|0更新时间：2020-08-12
- 摘要：Sr2+ doped Ca2Nb2O7:Eu3+ red-emitting phosphors were synthesized by a high temperature solid-state reaction. The photoluminescence properties of Ca1.97-xSrxNb2O7:3%Eu3+(x=0.10, 0.50, 1.0, 1.5, 1.97) and the effect of Sr2+ concentration on this phosphor were investigated. X-ray diffraction patterns of Ca1.97-xSrxNb2O7:3%Eu3+ show several compositional phase transformations with different Sr2+ concentration. The excitation spectrum of Ca1.97Nb2O7: 3%Eu3+(x=0) exhibits a broad band centered at 302 nm corresponding to the charge transfer (CT) transition of O2-→Eu3+. The shoulder peak at 272 nm is attributable to CT transition of NbO7-6. The excitation spectrum also shows several sharp lines of f-f transitions of Eu3+ from 350 to 600 nm. Excited by 398 nm, Ca1.97Nb2O7:3%Eu3+ shows an intense red-emitting originated from 5D0→7F2 transition of Eu3+ at 616 nm. The intensities of the excitation peaks of Ca1.97-xSrxNb2O7:3%Eu3+ are enhanced firstly and then decrease with the increasing of Sr2+ content. The CT transitions of O2-→Eu3+ have a red shift with the increasing of Sr2+ content. The doping of a small amount of Sr2+ can enhance the red-emitting of Ca1.97Nb2O7:3%Eu3+, and the optimum content is x=0.01. The results indicate that Ca1.97-xSrxNb2O7:3%Eu3+ may become a candidate for ultra-violet chip pumped and multi-phosphors converted white LEDs.关键词：Sr2+ doped Ca2Nb2O7：Eu3+;Sr2+;niobate;red-emitting phosphor133|163|1更新时间：2020-08-12
- 摘要：CdSe/CdS core-shell nanocrystals were one-step prepared by microwave-hydrothermal method. The growth mechanism of nanoparticles was discussed and attributed to the sulfur release process from mercaptopropionic acid. The results from XRD and Raman spectra suggested that the core-shell CdSe/CdS nanocrystals were obtained under the reaction temperature of 140℃. FTIR spectra were in situ monitored for the decomposition of mercaptopropionic acid upon reaction time, which contributed to the formation of CdS shells. The band-related and trap states fluorescent emission from nanocrystals were both observed in PL spectra. The increased band related emission intensity further verified the formation of core/shell structure of CdSe nanocrystals.关键词：microwave-hydrothermal method;core-shell nanocrystals;growth mechanism;emission spectrum120|443|1更新时间：2020-08-12
- 摘要：Ce-doped Bi2O3 photocatalysts with different molar ratio were prepared by the hydrothermal process, and then calcined at 600℃ for hours. The Ce-Bi2O3 photocatalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopic(XPS), and ultraviolet-visible spectrophotometry (UV-Vis), respectively. The photocatalytic properties of Ce-Bi2O3 were evaluated by the photo-degradation of acid orange Ⅱ under visible light irradiation. The results show that the doping of Ce can decrease the band gap of Bi2O3 significantly, and extend the visible light absorption. The doped Ce partially substitutes Bi in the lattice of Bi2O3, which exists in the form of Bi—O—Ce chemical bond. Meanwhile, a new complex metal oxide compound (Bi7.38Ce0.62O12.31) appears in the catalysts, which can separate the electron-hole pairs and improve the photocatalytic performance. The results also indicate that the catalyst can be sintered with the extension of calcination time, resulting in lower catalytic activity of Ce-doped Bi2O3. Generally, the Ce-doped Bi2O3 samples with the Ce/Bi molar ratio of 1:2 calcined at 600℃ for 2 h possess the great photocatalytic activity for acid orange Ⅱ.关键词：Ce-doped;Bi2O3;visible light response;acid orange Ⅱ227|121|1更新时间：2020-08-12
- 摘要：By spraying organic solid nano-crystals of 2,5-diphenyloxazole (DPO) on the nano-Au film, the nano-Au/DPO multilayer films were fabricated. The crystal structure, surface morphology, and UV fluorescence properties were tested by X-ray diffraction(XRD), field emission scanning electron microscope (SEM), and fluorescence spectrophotometer, respectively. Compared with pure DPO film, the UV fluorescence peaks of nano-multilayer films appear blue shift of 5 nm, and the shapes of DPO fluorescence peaks are different. The fluorescence intensity of DPO is inversely proportional to the number of layers, and the fluorescence intensity of nano Au film is directly proportional to the number of layers in the nano-Au/DPO multilayer films. DPO film is amorphous in the nano-Au/DPO multilayer films, and nano Au film is composited of nano-Au particles from 1 to 3 nm. Due to the interaction effects of DPO and nano Au, the crystal structure of DPO in nano-Au/DPO multilayer films is different from that in pure DPO film, so the fluorescence characteristics of DPO are different, too.关键词：fluorescence properties of nano-au films;nano-multilayer films;UV fluorescence blue shift;2;5-diphenyloxazole(DPO)97|178|2更新时间：2020-08-12
- 摘要：The temperature of the active region of the semiconductor laser was simulated by using Ansys with different heat generation on the cavity surface and different width of non-injection regions near cavity surface. The temperature rise of the facet has a great impact on the reliability of the laser. The results indicate that the temperature of the facet can be reduced effectively by the introduction of non-injection region. The temperature drop provides an advantage for suppressing the non-radiation recombination and optics absorption to improve the COD threshold.关键词：semiconductor laser;ANSYS;non-injection regions;COD104|160|5更新时间：2020-08-12
- 摘要：Before the epitaxy of low-temperature buffer layer, the patterned sapphire substrate was prepared by a pre-growth treatment at a high temperature under a small amount of trimethyl gallium (TMGa) and a great quantity of ammonia (NH3). Four types of blue light-emitting diode (LED) wafers were fabricated using different flow-rate of TMGa. The laser interferometer in MOCVD was used to monitor the thin-film reflectance during the epitaxial growth process. The high-resolution X-ray diffraction rocking curves of (002) and (102) crystal faces were utilized to estimate the threading dislocation density. The photoluminescence spectra were measured to feature the light-output performance. Moreover, LED chips were fabricated and tested. It is shown that the pre-growth treatment benefits the lateral growth of three-dimensional GaN islands in epitaxy process and leads to fast coalescence within a small thickness. Thus, the threading dislocation can be suppressed and the quality of epitaxial film would be improved. The enhancement of light-output power of LED chips can be up to 29.1% without degradation of electrical performance. However, the flow rate of TMGa should be tuned carefully, because excess quantity of TMGa would cause a large size of GaN grain crystal, which induces delayed coalescence time and low-quality of epitaxial film.关键词：LED;GaN;patterned sapphire substrate;high-temperature pre-growth treatment110|202|0更新时间：2020-08-12
- 摘要：3 nm well-width GaAs/AlAs multiple-quantum wells were grown by molecular beam epitaxy with Be acceptors δ-doped at quantum-well center on a semi-insulating GaAs (100) substrate. According to the transitions from bound to unbound states of quantum-confined acceptors, the terahertz prototype photodetector based Be acceptors-doped GaAs/AlAs multiple-quantum wells was designed and fabricated. The terahertz photocurrent spectrum and dark current-voltage characteristics of the device were measured at 4.2 K, respectively. Under a bias of 6 V and the normal incidence of a 6.8 THz laser, the hole carriers transport along quantum well layers, and the photodetector responsivity is 2×10-4 V/W (2 μA/W). According to the I-V curves measured at 4.2 K, the device full-shot noise current was calculated. It is 5.03 fA·Hz-1/2 with a bias of 6 V.关键词：terahertz photodetector;responsivity;δ-doped quantum wells;quantum-confined acceptors95|160|1更新时间：2020-08-12
- 摘要：Highly-fluorescent green and red CdSe/ZnS core/shell gradient alloy quantum dots (QDs) were synthesized by one-step method. The phosphine-free three-band white light LEDs were fabricated by directly incorporating QDs/epoxy composites with blue InGaN chip. The influences of the content and proportion of red (650 nm) and green (550 nm) QDs on the color coordinate and efficiency of white LED were researched. When the red/green QDs ratio is 2:3, the standard three-band RGB QDs-WLED can be achieved with a CIE-1931 color coordinates of (0.322 8, 0.335 9), CCT of 5 725 K, CRI of 72.7, and power efficiency of 26.61 lm/W. FWHM of the red, blue, and green peak of the white QDs-LED is 30, 25, and 38 nm, respectively.关键词：quantum dot;core-shell;white-LED;light conversion layer165|42|2更新时间：2020-08-12
- 摘要：Photonic crystal structures of 290 nm period were fabricated on the surface of AlGaN layer by nanoimprint lithography. Highly ordered porous anodic aluminum oxide was adopted as a convenient approach for large area of PhC pattern transferred. In contrast to a planar sample, both intensity and radiation profile of surface emission from AlGaN materials with PhCs structures were improved significantly. Honeycomb PhC structures deflected the original in-plane vector of TE guided light. The modified radiation profile was attributed to the diffraction and Bragg scattering effects of PhCs. The results would be helpful to enhancing surfacing emission and ameliorate polarization properties of deep-UV LEDs.关键词：light extraction efficiency;deep ultraviolet light;anodic aluminum oxide;photonic crystals;polarization property152|124|3更新时间：2020-08-12
- 摘要：The amplified spontaneous emission (ASE) of the blend waveguide based on poly (9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) and poly (3-hexylthiophene) (P3HT) was studied, and the gain and loss of the blend waveguides were discussed in detail. The photoluminescence quantum efficiency (PLQE) of F8BT:P3HT blend decreases with the increasing of P3HT fraction. When the P3HT fraction is less than 20%, PLQE of blends decreases slightly. Meanwhile, the loss coefficient decreases from 7.8 cm-1 for F8BT waveguide to 4 cm-1 for the waveguide based on the blend of F8BT and P3HT. So the decrease of ASE threshold of blend waveguides is resulted from the reduction of loss of the blend film waveguides. The decrease of ASE threshold would be benefit to the realization of electrically driven laser in waveguide based on the blend of F8BT and P3HT.关键词：amplified spontaneous emission;blend polymer waveguides;threshold;photoluminescence quantum efficiency;loss coefficient109|206|1更新时间：2020-08-12
- 摘要：A novel optical humidity sensor based on single microring with three couple points was proposed, and polyimide (PI) was used as the moisture material. The transmission characteristics of the PI microring vary with the environmental humidity, which leads to the shift of the output optical spectrum. Humidity was measured by detecting the drift of the output spectrum, meanwhile, the optimal humidity sensing part was selected and the sensing properties of different sensing-parts were discussed. The numerical results show that the sensitivity and the sensing-range are improved obviously and the free spectral range (FSR) of the structure is tripled compared to the conventional single microring sensor. Moreover, the whole structure of single micro-ring with three couple points could be served as the optimum sensing part. The sensitivity of the humidity sensor is up to 0.98 nm/%RH and the sensing relative humidity range is from 10%RH to 80%RH. The structure in this paper is of great importance to low-cost and high sensitivity humidity sensor.关键词：microring resonator;humidity sensor;polyimide195|194|5更新时间：2020-08-12
- 摘要：The fluorescence emission and synchronous spectra of the bovine serum albumin (BSA) and terazosin hydrochloride (THD) mixed system were studied. The most intensive characteristic peak (340 nm) was found in the spectrum of BSA solution, and the addition of THD resulted in the fluorescence quenching of BSA. Based on this phenomenon, the determination method for THD was established, in which BSA was used as the fluorescent probe. The correlation coefficients of the model functions are all more than 0.99. The recoveries of emission and synchronous spectra are 96.04%~103.16% and 100.41%~105.58%, the relative standard deviations (RSD) are 3.70% and 2.42%, the limits of detection are 0.64×10-8 mol/L and 0.66×10-8 mol/L, and the limits of quantification are 0.21×10-7 mol/L and 0.22×10-7 mol/L, respectively.关键词：bovine serum albumin;terazosin hydrochloride;fluorescence spectrum;content determination134|177|0更新时间：2020-08-12
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