最新刊期
卷 34 ， 期 12 ， 2013
- 摘要：Cu doped natural sodalite phosphors were synthesized by solid-state reaction method at high-temperature. To examine chemical components of sodalite, we conducted electron probe micro-analysis (EPMA) and energy dispersive spectroscopy (EDS) analiysis using an electron probe scanning electron microscope spectrometer. The structure of Cu doped sodalite samples were characterized with X-ray diffraction (XRD). The VUV-Vis luminescence properties were measured at room temperature. The results show that the excitation band at 171 nm attributed to host absorption and that at 202, 255, 280, 290 nm are due to the 3d103d94s transition of Cu+ ion. Cu existed in two lattice sites in the sodalite crystal, including Cu1 at the lattice site of Na+ ions and Cu2 between the composite layers, and formed Cu1 and Cu2 luminescence center of Cu+ ion, respectively. These emission spectra with the blue-ray peak at 420 nm and 470 nm, which were obtained by exciting the Cu1 and Cu2 luminescence center under different wavelength, and can be attributed to the 3d94s3d10 electronic transition of Cu+ ion. The mechanism of luminescence and concentration quenching process were discussed.关键词：natural sodalite;Cu+ ion;luminescent center;vacuum ultraviolet photoluminescence;concentration quenching149|324|1更新时间：2020-08-12
- 摘要：Coumarin 6 (C6) doped fluorescent hybrid nanoparticles (NPs) were prepared by a reprecipitation-encapsulation method. The as-prepared NPs were characterized by SEM and DLS. The C6-doped NPs gave strong green fluorescence under the excitation of 450 nm. The concentration-dependent fluorescence of C6-doped NPs was then studied. The results indicated that the fluorescence of C6 was quenched by intermolecular energy transfer rather than by aggregation. In addition, the difference in spectral shape of PS-based and PMMA-based NPs was interpreted from the view of polymer structure. The broad emission band in PS-based NPs was attributed to two different microenvironments surrounding C6, while the narrower emission band in PMMA-based NPs to one local environment. Finally, the loading capacity of the hybrid NPs for C6 is studied, and higher doping concentration will result in aggregates in water.关键词：Coumarin 6;fluorescence;hybrid nanoparticles;concentration quenching139|154|0更新时间：2020-08-12
- 摘要：The phosphors composed of Eu or Ce ions doped in Ba10(PO4)4(SiO4)2 matrix were prepared by solid state reaction. The PL spectra properties of Ba10(PO4)4(SiO4)2:Eu2+ and Ba10(PO4)2(SiO4)2:Ce3+ were investigated. Strong broad excitation band was observed in both samples. The Eu2+ of Stokes shift (ΔS) and excitation energy of Ba10(PO4)4(SiO4)2:Eu2+ were calculated by the PL spectra of Ba10(PO4)2(SiO4)2:Ce3+. The estimated excitation energy and the experiment result are closely coincided. Ba10(PO4)4(SiO4)2:Eu2+ can be excited by UV-LED or blue LED, and emits absinthe-green light.关键词：phosphors;spectra;Eu2+;Ce3+;Ba10(PO4)2(SiO4)2142|113|2更新时间：2020-08-12
- 摘要：Polyfluorene containing thiadiazole (PDOF-TAF) was synthesized by palladium-catalyzed Suzuki cross coupling reaction of 2,7-dibromo-9,9-dioctyl-9H-fluorene (Br-DOF), 9,9-dioctyl-9H-fluorene-2,7-diyldiboronic acid (B-DOF) and 4-(8-(2,7-dibromo-9-octyl-9H-fluoren-9-yl)octyloxy)-N-(4-(7-(4-(diphenylamino) phenyl)benzo[c][1, 2, 5] thiadiazol-4-yl)phenyl)-N-phenylaniline (Br-TAF). The synthesized polymer was applied as white light-emitting polymer and was used as the emitting layer to prepare the non-doped white organic light-emitting diodes (WOLED) by spin-coating. The color coordinates locate at (0.23, 0.18). By inserting 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBI) as electron transport layer and Poly(N-vinylcarbazole) (PVK) as hole transport layer, the emission spectra of the diode cover 410~700 nm visible region, and the color coordinates shift to (0.24, 0.32), locating close to the white point. In addition, the luminescence and current efficiency can reach up to 2 020 cd/m2 and 1.4 cd/A, respectively, indicating that the synthesized polymer has highly potential application as the material of white light-emitting layer in WOLED.关键词：white emitter;fluorene;polymer;WOLED139|149|0更新时间：2020-08-12
- 摘要：Double Gaussian functions with different center wavelengths or bandwidths were used to fit LED chips' spectra. Emission spectra and correlated color temperatures (CCTs) of Ce/Tb/Eu co-doped glasses excited by different LED chips were calculated by experimental results of fluorescence spectrophotometer. When the bandwidths of chips keep unchanged, CCTs of Ce/Tb/Eu co-doped glasses decrease with the red shift of center wavelength from 370 nm to 378 nm. When center wavelength of chips keeps unchanged and bandwidth increases from 10 nm to 25 nm, CCTs of Ce/Tb/Eu co-doped glasses depend on the center wavelengths of LED chips. When the emissions of LED chips are stable, the effect of bandwidth on CCTs of Ce/Tb/Eu co-doped glasses is less than that of center wavelength. So for the application of LED, we should give preference to the center wavelength of LED chips.关键词：luminescence glass;LED chip;excitation wavelength;bandwidth145|279|1更新时间：2020-08-12
- 摘要：The varisized samples (4.7~115.5 nm) of β-NaGdF4:1%Tb3+,1%Er3+ nanocrystals (NCs) were synthesized by hydrothermal method using Span 80 as template. In Rayleigh limit (the size of the particle is comparability with the wavelength of the transition), the influences of the NCs sizes on local density of states (LDOS), radiation and nonradiation of Tb3+-Er3+ spectral pairs embedded in β-NaGdF4 nanospheres were investigated, to reveal the physical mechanics of DC process further. Based on the Tb3+-Er3+ spectral pair located at the center of a dielectric β-NaGdF4 nanosphere model, the spontaneous decay rate of Tb3+-Er3+ emitter, as a probe of the LDOS, was calculated with the Green tensor approach. There is no significant variation of LDOS inside the nanospheres. For the small size (R<<λ) of NCs, a new Gauss's distribution-like of the LDOS was obtained by Chew's theory, for R>35 nm (in our case) the descent side of the Gauss-like distribution of the LDOS was obtained. The LDOS is directly proportional to local field E2, thus the Gauss-like distribution of the LDOS can be attributed to the strong interaction between the small emitter and the local field. By calculating the ratio of spontaneous radiative rate of bulk medium and the size of NCs, the filling factors can be determined directly.关键词：energy downconversion;β-NaGbF4 dielectric sphere;spontaneous emission rate;local density of state101|25|0更新时间：2020-08-12
- 摘要：Yb3+/Er3+ co-doped BaGd2O4 phosphors were prepared by the sol-gel method. The influence of annealing temperature on BaGd2O4 crystal structure was investigated. Under 971 nm excitation, the dependence of the emission power and the up-conversion efficiency on the excitation density was studied. The obtained data show that the light conversion and absolute quantum efficiency of BaGd2O4:Yb3+,Er3+ are 82 and 7.8 times smaller than that of BaGd2ZnO5:Yb3+,Er3+, respectively. But the phonon energy of BaGd2O4 is almost the same with that of BaGd2ZnO5:Yb3+,Er3+ which possesses the highest efficiency as ever reported. So, we can conclude that the material structure is the main influencing factor on the up-conversion efficiency when the phonon energy of the host is not very high.关键词：up-conversion;BaGd2O4;efficiency;Yb3+/Er3+132|92|0更新时间：2020-08-12
- 摘要：In order to improve the up-conversion efficiency of Yb3+-Er3+ co-doped TiO2 film, SiO2 was doped into the film which deposited on the glass substrate by sol-gel method and spin-coating technique. The effect of SiO2 on the film's morphology and optical properties was researched. The morphology, near-infrared transmittance, and photoluminescence (PL) spectra of the film were tested and analyzed. The results show that the particle size of TiO2 decreases with the introduction of SiO2, but the property of near-infrared light transmittance decreases nearly keep steady. The film emits red light at 630~670 nm, weak green light at 516~537 nm and 537~570 nm under 980 nm excitation. In additional, the intensity of the up-conversion luminescence tends to be saturated with pump power increasing.关键词：sol-gel;SiO2/TiO2;thin film;rare earth;up-conversion130|93|0更新时间：2020-08-12
- 摘要：The OLED devices were fabricated with the structure of ITO/NPB (30 nm)/Rubrene (0.2 nm)/CBP:Bczvbi (8 nm, x%)/Bphen (30 nm)/Cs2CO3:Ag2O (2 nm, 20%)/Al (100 nm). The effect of different CBP:Bczvbi doping concentration (x=5, 10, 15) on the properties of white light device was studied. High luminance and efficiency white organic light-emitting diodes (OLEDs) were obtained comprehensively utilizing the energy transfer between the host and the guset in the luminous layer and the hole-blocking characteristics. The device had the maximum efficiency and luminance when the mass fraction of Bczvbi was 10%. This device had a maximum current efficiency of 4.61 cd/A at 7 V and maximum luminance of 21 240 cd/m2 at 9 V. The CIE coordinates of the device were well within the white region when the voltage changed from 4 V to 9 V.关键词：doping concentration;energy transfer;current efficiency;luminance100|112|0更新时间：2020-08-12
- 摘要：The high-resistivity (HR) GaN is the basis of GaN-based electronic devices. The HR-GaN films were grown by metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrates, using trimethyl gallium (TMGa) and NH3 as precursors and high purity H2 as carrier gas. GaN samples with different resistivity were prepared at various annealing pressures between 10 000 Pa and 54 200 Pa. Surface morphology, dislocation density of different resistivity of the GaN films were characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). The resistance of GaN increases rapidly with the annealing pressure reducing. The high-quality GaN epitaxial films have been achieved by the experimental method. With the annealing pressure reducing, the edge dislocation density significantly increases by several times, and the screw dislocation density changes. The correlation between the morphology of threading dislocations (TDs) and the origin of HR GaN films was investigated using transmission electron microscopy. It is observed that the morphology of TDs can lead to different resistivity in GaN film, and the edge-type TDs are more sensitive to the sheet resistivity than the screw-type TDs. The sheet resistivity increases by seven orders of magnitude with the increase in the edge-type TDs. The morphology of TDs determines the movement of the negative charges which leads to different resistivity of the GaN film. The TDs can work as the electronic conduction channels. In the low-resistivity GaN, almost all TDs are bent and interactive, and the electrons also move along with the channels formed by the bent TDs. In the HR-GaN, TDs are all straight and perpendicular to the sapphire, and the electrons are difficult to move in the lateral direction.关键词：GaN;morphology of threading dislocations;high-resistivity;MOCVD167|179|1更新时间：2020-08-12
- 摘要：In order to improve the fill factor and efficiency of the homogeneous high sheet resistance emitter solar cell, the effect of the gridline pattern on the performance of the solar cell was studied by using PC2D software. The results show that the efficiency of the solar cell can reach 19.09% after the optimization of the gridline pattern(109 gridlines with a width of 40 μm). The results indicate that a high efficiency can be realized for solar cell with homogeneous emitter without employing complicated structure and fabrication process.关键词：PC2D;gridline pattern optimization;conversion efficiency103|171|0更新时间：2020-08-12
- 摘要：It is of great importance for developing stable-metal-based cathode interfacial layer of polymer light-emitting diodes (PLEDs), which is one of the key points for the mass-production techniques of PLEDs. Phosphonate-functionalized polyfluorene (PF-EP) is a neutral polar polymer material, which is soluble in alcohol solvent (thus being compatible for preparing multilayer solution-processed lighting devices). And most importantly, it can achieve highly efficient electron injection current in conjunction with stable aluminum as cathode. Herein, we systematically discussed the applications of two cathode structures of PF-EP/LiF/Al and PF-EP/Al in a prototype green-polyfluorene based PLEDs. The results indicate that the structure of PF-EP/LiF/Al possesses much higher electron injection capability than PF-EP/Al. The electron injection behavior and mechanism has been discussed based on the studies on the electron-only devices and X-ray photoelectron spectroscopy.关键词：phosphonate-functionalized polyfluorene;interfacial modification;polymer light-emitting diodes106|133|0更新时间：2020-08-12
- 摘要：In order to improve the light emitting efficiency of GaN-based LED, a double-grating structure was established by etching grating on both sides of silver metal film. A numerical simulation was conducted using the finite difference time domain method (FDTD). The light extraction efficiency in different patterns was compared, including without-silver-film pattern, without-grating pattern, single-grating pattern and double-grating pattern. When the grating period is 300 nm, duty cycle is 0.23, silver film thickness is 30 nm and light source depth is 150 nm, the light extraction efficiency of the double-grating structure is improved by 6 times than the single-grating structure, and 16 times than the structure without grating.关键词：light emitting diodes;finite-difference time-domain;light extraction efficiency;surface plasmon polaritons120|156|3更新时间：2020-08-12
- 摘要：The Au Nano-ropes (AuNRs) with aspect ratio of ~5 were synthesized through seed-mediated growth. We measured the absorption spectrum of the AuNRs and the AuNRs had a broad absorption band (800~1 600 nm). Furthermore, we measured the nonlinear absorption of the AuNRs and the result indicated that the AuNRs could be used to realize saturable absorption around 1.56 μm. Therefore, passively Q-switching could be achieved by using them. By inserting the AuNRs into the Er-doped fiber laser cavity, stable Q-switched pulses were achieved for a threshold pump power of 30 mW, and the emission wavelength was 1.56 μm. The highest output power of about 6.9 mW and the pulse energy as high as 219 nJ were obtained when the pump power was increased to 205 mW. Our results show the AuNRs are promising saturable absorber(SAs) for pulsed lasers.关键词：gold nanorods;nonlinear optics;fiber laser;passively Q-switching116|74|3更新时间：2020-08-12
- 摘要：In order to study the output characteristics of 808 nm InGaAlAs vertical cavity surface emitting laser (VCSEL) array at different temperature, the InGaAlAs VCSEL temperature shift is calculated under the temperature-dependent Sellmeier equation. 2×2 arrays of 808 nm VCSEL are fabricated with non-closed structure. Each emitter diameter is 60 μm. Lasing wavelength, optical power and the threshold current are measured by changing the temperature of heat sink. The maximum output power reaches 56 mW in the pulse width of 50 μs, and the repetition frequency of 100 Hz at 20 ℃. The central wavelength is 808.38 nm, and the full width at half maximum is 2.5 nm, continuous output power reaches 22 mW, the output power decreases rapidly above 50 ℃, the temperature shift is 0.055 nm/℃. Experimental temperature shift is consistent with the theoretical value.关键词：808 nm;VCSEL;arrays;temperature shift156|146|0更新时间：2020-08-12
- 摘要：A heterojunction solar cell based on poly (hexylthiophene) (P3HT) and fullerene (PCBM) was fabricated. The hole transport layer and the active layer were prepared by spraying. The effect of the substrate temperature on the morphology of the active layer and the performance of the device were studied. The results show that the film roughness decreases and the absorption rate increases when the substrate temperature increases. And when the substrate temperature is 130 ℃, the device performance is optimized and the efficiency of a 25 mm2-size device is 2.09%.The small size devices were combined in series and parallel to achieve a 11.2 cm2-size large area organic solar array and the conversion efficiency is 1.83%. It is found that the area is increased by 44.8 times, while the efficiency loss is less than 13%.关键词：spraying;organic solar cell;P3HT：PCBM;large area;series-paralle105|125|1更新时间：2020-08-12
- 摘要：AlxGa1-xN/AlN/GaN high electron mobility transistor (HEMT) materials with different Al compositions (x=0.19, 0.22, 0.25, 0.32) were grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD). The effects of Al composition on electrical and structural properties of HEMTs materials were analyzed. It is observed that two-dimensional electron gas (2DEG) density and mobility are improved with the raising of Al content within a certain range. However, too high Al composition will make the surface turn to be rougher and the mobility deteriorate, which was reinforced by the test results of atomic force microscopy (AFM). The optimum Al content is 25%. Based on this, the HEMT materials showed a high 2DEG density of 1.2×1013 cm-2 with a low sheet resistance of 310 Ω/□, and highly Hall mobility of 1 680 cm2/(V·s) at room temperature.关键词：Al composition;AlGaN;HEMT;electrical properties;MOCVD122|62|1更新时间：2020-08-12
- 摘要：The continuous xenon lamp spectra and realistic sunlight spectra were compared. The results show that the infrared part of xenon luminescence spectra covers about 57.4% of the total spectra, but the infrared part only covers 28.3% in the standard spectra. According to the difference of the spectra, curve was fitted and λ0=925 nm of the lowest point of transmittance curve was got. The infrared part of luminescence spectra of xenon was properly filtered by optical filter and the spectra are up to standard marched-degree after filtering. The biggest deviation value for spectra is only 12.5% by testing the spectra of 6 different position points. The result shows that the spectral uniformity of xenon is good after filtering. Silicon cell was detected to have defection by electro-luminescence and the electric performance test was done. The value of Ⅰ-Ⅴ is different for discrepancy power 0.22 W by using the optical filter and without the filter. It indicates that the accuracy rating of electric performance testing is directly influenced by spectral marched degree of xenon.关键词：continuous xenon lamp;spectral matched degree;transmittance;electric performance151|751|1更新时间：2020-08-12
- 摘要：The transmission of a subwavelength zigzag-shaped metal-insulator-metal (MIM) plasmonic waveguide structure was numerically researched by using the finite-difference time-domain (FDTD) method. The zigzag-shaped waveguide has two bending corners, where waveguide can extend out from one to four cuts. Each cut can be looked as a self-existent resonant cavity. The resonant wavelength is approximately linear proportional to the depth of cut, and independent on the direction of cut. When any cut satisfies with the resonant condition, the transmission of the waveguide structure is close to zero at the resonant wavelength. With the increase of number of the same depth of cuts, the wavelength region of band gap is broaden gradually, thus a good broadband filter is formed.关键词：subwavelength;surface plasmon polaritons;plasmonic waveguide;filters110|133|0更新时间：2020-08-12
- 摘要：The interaction between succinic-oligochitosan-rare earth complexes (BCS-La and BCS-Nd) and herring sperm DNA was investigated by cyclic voltammetry and UV-Vis spectra. The results indicated as follows. Firstly, the peak current of probe molecule Fe(CN)63-/4- at Au/DNA electrodes obviously decreased and the peak potential shifted positively because of the existences of complexes. All above these showed that there was a competitive effect between complexes and probe molecule with herring sperm DNA, which revealed that a binding mode intercalation was interacted between complexes and herring sperm DNA. The reaction of Fe(CN)63-/4- at Au/DNA electrodes was controlled by adsorption mechanism in the range of scan rate from 0.01 V/s to 0.2 V/s. Secondly, the absorption intensity of herring sperm DNA decreased with the adding of complexes, and the maximum absorption peak had a red shift, which further illustrated that a binding mode intercalation was interacted between complexes and herring sperm DNA, thus led to the change of DNA conformation. The combining ratio of n(BCS-La) and n(BCS-Nd) with DNA was 2:1 and 6:1, respectively.关键词：succinic-oligochitosan;rare earth;complexes;herring sperm DNA97|96|6更新时间：2020-08-12
- 摘要：The optimum molecular geometry of 16 kinds of polycyclic aromatic hydrocarbons (PAHs) and six kinds of PAHs nitro derivatives were calculated by the B3LYP method of Density Functional Theory (DFT). Under the basis of 6-311++G(d, p), 40 parameters of vibration frequency, polarizability, dipole moment and thermo-dynamical parameters were calculated. Using the toxicity of 13 PAHs for photobacterium as the dependent variable, other 3 PAHs were used to test and verify, toxicity of PAHs quantitative structure-activity relationship (QSAR) model based on quantum chemical parameters has been constructed to forecast the toxicity of PAHs nitro derivatives. The QSAR model has been proved that the model coefficient of simulation is 0.816. The seriation of the toxicity of PAHs nitro derivatives calculated by the model is same with the toxicity sorting reported in the literature indicates that the model can be used to predict the toxicity of PAHs nitro derivatives. It also illustrated that there are similarities between the toxic mechanism of PAHs nitro derivatives and PAHs, so as to provide a theoretical basis for the control and prediction the toxicity of PAHs and PAHs nitro derivatives.关键词：density functional theory (DFT);quantitative structure-activity relationship model;polycyclic aromatic hydrocarbons (PAHs);PAHs nitro derivatives;toxicity104|115|1更新时间：2020-08-12
- 摘要：The characteristics of one-dimensional photonic crystals with insertion of defect layers were studied by using transfer matrix method. There are two PBG range of 467~510 nm and 1 279~1 715 nm in the PC without defect layers. The relationship of the transmission spectra between the defect layer thickness and the angle of incidence was studied. The location of the defect mode is very sensitive to the angle of incidence. The number of the defect mode is equal to that of the defect layers. The thickness of one-dimensional photonic crystal does not change the number of defect mode and the central location of transmission peaks, it just changes the width and transmittance of the transmission peak.关键词：photonic crystal;photonic band gap;one-dimensional photonic defect mode;filter99|104|0更新时间：2020-08-12
- 摘要：Due to the limitation of single LED, it is of great significance to apply LED arrays to enhance the brightness and enlarge the luminous area to improve the uniformity of illuminace. Different from traditional analytical calculation methods, particle swarm optimization algorithm was proposed to optimize the structure of LED arrays to achieve a good uniform illuminace distribution on the target plane in this paper. Firstly, formulae of illuminance distribution on target plane illuminated by LED arrays were obtained, and then an evaluation function was constructed to measure the uniformity of illuminance distribution. Matlab software was used to calculate the initial structure parameters. Finally, Tracepro optical software was adopted to give an imitation and simulation. The simulation results show that the LED arrays can produce highly uniform illuminace distribution. It indicates that our method is simple and can optimize the LED automatically by computer program.关键词：LED arrays;particle swarm optimization algorithm;illuminance;uniformity277|217|19更新时间：2020-08-12
- 摘要：The complete bandgap of surface resonances on a metal plate perforated with a triangular array of air holes was theoretically and experimentally investigated. Parametric study of holes size implies that the triangular lattice is predominant to the formation of the complete bandgap. As a useful application, highly directive emission from a dipole antenna positioned near the meta-surface is observed at the lower band edge and at other frequencies inside the bandgap. It has a half power beamwidth of 5.6° in E-plane and 6.2° in H-plane, exhibiting a very high directivity.关键词：metamaterials;surface resonance bandgap;directive emission110|154|0更新时间：2020-08-12
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