最新刊期
卷 37 ， 期 5 ， 2016
- 摘要：The quantum efficiency of deep UV light emitting diodes (LED) drops dramatically with the increasing of Al content. Understanding the emission mechanism of high Al-content AlGaN multiple quantum wells (MQW) is the one of the most important objects for improving the quantum efficiency of deep UV LED. In this work, high Al-content AlGaN MQW structure with atomically flat hetero-interfaces was grown and characterized by photoluminescence (PL) measurements at different temperatures. The results indicate that there is a strong exciton-localization effect in the MQW structure and the emission is closely related to the hopping of the excitons. Due to the exciton delocalization and nonradiative recombination at defects, the PL intensity is strongly quenched at high temperatures.关键词：AlGaN;MQW;deep UV-LED;emission mechanism182|421|1更新时间：2020-08-12
- 摘要：In order to study up-conversion luminescence characteristics of Er3+/Yb3+ co-doped YNbO4 powder materials, the spectrum property was calculated by using J-O theory in this paper. The spectrum intensity parameters were obtained by the fitting method based on the absorption peak's area of the absorption spectrum, and the theoretical oscillator intensity and the experimental oscillator intensity were figured out according to the spectrum intensity parameters, and the mean square deviation of them(δrms) was 3.916×10-7. The parameters such as the transition probability, transition branching ratio and energy level life etc. of Er3+ particles in YNbO4 powder materials were calculated, and the stimulated emission cross section of Er3+ radiative transition from the energy level 2H11/2, 4S3/2 and 4F9/2 to the ground state was also figured out. The experimental results show that YNbO4 is one kind of superior up-conversion matrix materials.关键词：YNbO4;J-O theory;up-conversion luminescence114|84|4更新时间：2020-08-12
- 摘要：Silicate glasses with different ratio of Yb3+ and Tm3+ were prepared by high temperature melting method. Absorption spectra show that the absorption process of Tm3+ and Yb3+ in 300-1100 nm are not disturbed by each other. Up-conversion luminescence of the glass sample under 980 nm LD was studied. The results show that Yb3+, Tm3+ launches strong up-conversion blue light at 477 nm (1G4→3H6), but the emission of red light 654 nm(1G4→3F4) and 795 nm (3H4→3H6) infrared light are all weak. Improving the ratio of Yb3+ can improve the emission intensity of 477 nm blue, 654 nm red and 795 nm infrared. The relationship between the intensity of up-conversion luminescence and the pump power of the laser was studied. The conversion of blue and red emission are three photon processes, and the infrared emission is two photon processes. Finally, the mechanization of Yb3+ and Tm3+ in the transformation of the silicate glass was analyzed.132|132|6更新时间：2020-08-12
- 摘要：To obtain efficient luminescent liquid crystals materials, (Z)-2-(4-((E)-4-butoxy-2-hydroxybenzylideneamino)phenyl)-3-(4-butoxyphenyl)-acrylonitrile (BHPA) was designed and synthesized, by introducing the Schiff base unit into α-cyanostilbenzene system. The aggregation-induced emission enhancement (AIEE) was studied by UV-Vis absorption spectra and photoluminescence (PL) spectra. Thermodynamic properties and liquid crystals (LCs) properties of BHPA were investigated with TGA, DSC and POM. The results show that BHPA is a luminescent liquid crystals material with AIEE, and the ordered orientated film of BHPA possesses luminescent anisotropic property with the linear polarization of 0.41.关键词：Schiff base;AIEE;luminescent liquid crystals;polarization emission132|54|4更新时间：2020-08-12
- 摘要：Energy harvesting was investigated in relaxor ferroelectric terpolymer P(VDF-TrFE-CFE) by pyroelectric effect. Original energy was the temperature fluctuations. Due to the non-linear dielectric property in the vicinity of polarization mechanism transition of nanopolar regions, we can harvest energy by operating Ericsson cycle. Experimental results show that the best energy harvesting temperature range is from 20 to -20℃. Ericssion cycle was simulated using the unipolar cycle at different temperatures. Two modes of energy harvesting were presented and analyzed:modeⅠmaximizing and mode Ⅱ minimizing harvested energy, mode Ⅰ is idealized, by applying a low voltage, the harvested energy can reach nearly maximum. The explanation of the two modes was given from the view of microstructure. Temperature and electric field dependence was also given, at 100 kV·mm-1, temperature from 20 to -20℃, giant energy can be harvested around 3483 mJ·cm-3. Compared with the single crystals, the advantages, such as the harvested energy increased by 10 times, working temperature decreased to room temperature, and the material flexibility, make it possible as a good candidate for energy harvesting.关键词：energy harvesting;pyroelectricity;terpolymer;P(VDF-TrFE-CFE);temperature fluctuation123|236|0更新时间：2020-08-12
- 摘要：Brush-like hierarchical ZnO nanostructures on carbon fiber was fabricated by RF magnetic sputtering method and hydrothermal growth. The hybrid structures showed high surface-to-volume ratio and better electrical conductivity. An individual carbon fiber coated ZnO nanorods was transferred to the Au interdigital electrodes to form an ultraviolet photodetector, and the spacing of the electrodes is 180μm. Under the illumination of 325 nm UV light, the device shows a high photocurrent gain of 200, a good stability and the spectral responsivities. Furthermore, the mechanism for UV response is discussed.关键词：ZnO;hybrid structures;ultraviolet photoresponse117|167|1更新时间：2020-08-12
- 摘要：Through doping different organic dyes in organic light-emitting diodes (OLEDs) with the same structures, we hope to investigate the relationship between the energy gaps of the doped dyes and the emission wavelength of the devices, as well as to analyze the energy transfer mechanism in the system. The structure of the OLED is ITO/NPB/CBP:dyes/TPBi/Mg:Ag/Ag, and the doped organic dyes include Ir(MDQ)2(acac), Ir(ppy)3and Firpic. The three doped devices have almost the same threshold voltages and emit red, green and blue light, respectively. At an luminance of 100 cd/m2, the green-light device doped Ir(ppy)3 achieves the highest external quantum efficiency of 7.64%. Meanwhile, the red-light device doped Ir(MDQ)2(acac) has the external quantum efficiency of 2.75%, which is the lowest one among the three devices, while the blue-light one doped Firpic achieves an external efficiency of 5.65%. The differences of the emission wavelength and the external quantum efficiency of those devices are assigned to the difference of the energy gaps of the dyes. Further analysis also shows that energy transfer between the CBP and the dyes exists.关键词：organic dyes;organic light-emitting diode;doping;energy transfer144|242|0更新时间：2020-08-12
- 摘要：Sulfur-plasma process was proposed to clean and passivate the surface of (100) oriented GaAs wafers for stable sulfur passivation effect. The photoluminescence (PL) intensity of processed samples with sulfur-plasma had an obvious improvement after 360℃ annealing, and 71% higher than the unpassivated sample. The stability of passivation was also tested. There was no obvious PL intensity degradation while the sample stored in open air over a month. The experiment results show that the passivation of GaAs surface treated by sulfur-plasma process has good stability.关键词：RF plasma;PL;passivation;GaAs104|131|1更新时间：2020-08-12
- 摘要：In order to achieve higher output power of laser-diodes single emitter, thermal performance of sandwiched submounts based on aluminum nitride and silicon carbide was investigated. The thermal resistance of devices was first calculated by finite element method numerically, and then tested by spectral method experimentally. Both the stimulated results and the experimental data show that the thermal resistance of devices packaged by SiC submounts is less than the AlN submounts, which means better heat dissipation capability of SiC submounts. In addition, optical characteristics of the devices were further tested. It is showed that higher output power and higher electro-optical conversion efficiency are achieved by the devices packaged by the SiC-sandwiched submounts. The output power of single emitter achieves 16.3 W at the injected current of 15 A around 915 nm. The peak electro-optical conversion efficiency reaches 68.3%, leading the domestic level.关键词：high-power laser diode;finite element analysis;thermal resistance128|722|7更新时间：2020-08-12
- 摘要：A new method of preparing the LED remote fluorescent sheet based on the electrostatic spinning process with flexible PET substrate is proposed, and the free package device structure is realized by separating the blue chip and the phosphor layer. Electrostatic spinning process is a new technology to prepare fluorescent sheet with high performance, which can effectively solve the problem of uneven distribution of fluorescent powder. The yellow and red fluorescent sheets were prepared by electrostatic spinning process. The transmittance, absorption rate, PL spectra of yellow fluorescent sheet were studied. The effect of red fluorescent sheet on the optical performance parameters of white LED, including the luminous flux, correlated color temperature and luminous efficiency, was also studied. Experimental results show that the prepared yellow fluorescent sheets have good light transmission in the visible band. Fluorescent spectrum is completely determined by the fluorescent powder, so we do not need to consider the influence of complex processes. Using red fluorescent sheet can keep high efficiency and decrease the correlated color temperature of the bulbs from 5595 K to 3214 K at the same time, which provides more chance for the design of lamps and lanterns in luminescence of curved surface and regulation of color temperature. With the continuous improvement of the technology, the remote fluorescent technology based on the electrostatic spinning process will be more perfect, the performance of the product will be further improved, and the pace of the white LED going into the lighting field is promoted.关键词：electrostatic spinning;LED remote fluorescent sheet;transmittance;PL spectrum;correlated color temperature98|138|4更新时间：2020-08-12
- 摘要：Light-emitting electrochemical cells (LECs) have a crucial benefit in low cost fabrication processes in flexible and large area illumination panels, but the white light emission remains to be a problem. The fabrication of flexible yellow LECs based on a cationic iridium complex was reported in this paper, which showed yellow electroluminescence with high current efficiency of 11.6 cd/A at 6 V. White light-emitting electrochemical cells were fabricated by blending material mixing polyfluorene with cationic iridium complexes. The cells show white electroluminescence with CIE coordinates of (0.31, 0.33), which is close to standard white emission.关键词：light-emitting electrochemical cells;white light;cationic iridium complexes;polyfluorene102|172|0更新时间：2020-08-12
- 摘要：This essay has reported the fabrication of a metal-oxide-semiconductor AlGaN/GaN high electron mobility transistor (MOS-HEMT) with an Al2O3 insulator layer which was deposited by atomic layer deposition (ALD) as the gate dielectric. The MOS-HEMT with a gate-drain distance of 10μm exhibits a drive current density of 680 mA/mm at a gate-source bias (Vgs) of +3 V and a specific on-resistance of 1.47 mΩ·cm2. Under a negative gate bias of -20 V, the gate leakage current of the MOS HEMT is over four orders of magnitude, which is lower than that of the Schottky-gate HEMT. The off-state breakdown voltage is 640 V at drain leakage current of 27μA/mm with Vgs=-14 V. The Schottky-gate HEMT leakage current is 191μA at the gate bias of +2 V and the MOS HEMT leakage current is as low as 23.6 nA at the gate bias of +20 V, which is approximately seven orders of magnitude lower than that of the Schottky-gate HEMT with similar gate dimensions. The on/off drain-current ratio (Ion/Ioff) is over 109 for the MOS-HEMT.关键词：AlGaN/GaN;Al2O3;high breakdown voltage;MOS-HEMT142|56|0更新时间：2020-08-12
- 摘要：Stimulated Raman scattering(SRS) is a kind of efficient nonlinear optical frequency conversion technology to extend laser wavelength range, and it has extensive prospects for various applications. Thus, it is important to develop new Raman medium with excellent optical properties and improve the performance of Raman laser. Compared with conventional Raman materials, diamond grown by chemical vapor deposition (CVD) has high Raman gain coefficient, large Raman frequency shift, outstanding thermal conductivity and broad optical transmission range. These properties are beneficial to raise average output power and conversion efficiency of Raman laser. In this paper, the optical and thermal properties of the CVD diamond were introduced briefly, and researches on Raman lasers based on synthetic crystal diamond were summarized in ultraviolet, visible and infrared range, respectively. Finally, the development of diamond Raman lasers was forecasted.关键词：synthetic diamond;stimulated raman scattering;Raman laser126|184|3更新时间：2020-08-12
- 摘要：ZnO nanorods were fabricated by electrochemical deposition on ITO substrate with ZnO seed layer. The influences of the thickness of seed layer and the deposition potential on the morphology of ZnO nanorods were discussed. Furthermore, ZnO nanorods self-powered ultraviolet photodetector was fabricated. The spectral responsivity of this photodetector has a maximum value of 0.012 A/W from 300 to 400 nm.关键词：ZnO;electrochemical deposition;self-powered photodetector104|127|2更新时间：2020-08-12
- 摘要：Using an alternating-current driving single needle jet plasma device, we produce a super long plasma jet (SLPJ) in the dielectric tube. The super long plasma jet (SLPJ) can be arbitrarily curved along the tube and can be sprayed into the air outside the tube. Photographing the propagation process of the SLPJ in the tube helps in understanding the corresponding transmission mechanism. It is found that, under normal atmospheric pressure, the SLPJ can reach about 85 cm, and owns different morphologies and transmission mechanisms during the negative and the positive half cycles. During the positive half cycle, the SLPJ spreads forward through the way of "plasma bullet", while through the continuous model in the negative half cycle. Analysis reveals that, the electric field, produced by the space charge due to discharge and wall charge on the dielectric tube wall, is the main reason that influences the transmission mechanism.关键词：plasma jet;single needle discharge;plasma bullet108|200|2更新时间：2020-08-12
- 摘要：CD-ROM, made of polycarbonate substrate membrane withnano-stripe, was used as photonic crystal sensor in this article. Spectral reflectance rate of this CD photonic crystal sensor rose from 64.5% to 99.1% linearly when temperature changed from 40 to 120℃, and the correlation coefficient R2 was 0.9995. Therefore, this CD polycarbonate membrane photonic crystal can be used as a temperature sensor. This sensor also was used as an organic alcohol sensor. The CD photonic crystal sensor was inserted into methanol and the experimental results showed that the maximum spectral reflectance rate reduced linearly with the reaction time. Other organic alcohols like ethanol, N-propanol and N-butanol all had the same linear tendency. The relation of dielectric constants of these organic alcohols and spectral reflectance rate reducing was linear relation too. All these means that this CD photonic crystal sensor also can be used as the tool of the detection of organic alcohol.关键词：CD disks;photonic crystal;sensor98|114|1更新时间：2020-08-12
- 摘要：Due to the high mobility, excellent uniformity over large area and low manufacturing cost, indium gallium zinc oxide thin film transistor (IGZO TFT) is promising technology in promoting active matrix organic light emitting diode (AMOLED) into mass production. However, threshold voltage(VTH) shift of IGZO TFTs still exists, thus AMOLED pixel circuit is required to compensate VTH shift. VTH detection method is essential in AMOLED pixel circuit design. This paper reviews typical VTH detecting methods, namely the discharging method, charging method, and constant-current-biasing method. Simulations using Smart-Spiceare are carried out to compare the compensation efficiency. Also, the influences of VTH detection time and TFT parasitic capacitance on different VTH detecting methods are comprehensively analyzed. It is shown that the discharging method can not accurately compensate negative VTH shift, the charging method requires the longest VTH detection time, and the constant-current-biasing method has the highest compensation accuracy.关键词：IGZO;TFT;AMOLED;threshold voltage compensation116|489|0更新时间：2020-08-12
- 摘要：Rare earth complexes with succinic acid and 1, 10- phenanthroline were synthesized firstly and the interaction with DNA was investigated by spectroscopy method, which provide the basis for the design and development of new anticancer drugs. Three kinds of ternary complexes of rare earth(La3+, Nd3+, Eu3+) with succinic acid (SA) and 1, 10-phenanthroline (phen) were synthesized in absolute ethanol solution, which were characterized by eleme-ntal analysis, IR, UV-Vis and TG-DTA methods. The compositions of the complexes were confirmed to be (RE)2(SA)(phen)·2H2O (RE=La, Nd, Eu). Meanwhile, the interactions between complexes and herring sperm DNA have been investigated by electronic absorption spectrum and fluorescence spectrum. The UV absorption spectra showed that the maximal absorption peaks intensity of complexes was weakened with the adding of DNA, and accompanied by a red shift. The combining ratio, binding constant of complex to DNA was obtained and the corresponding thermodynamic parameters were calculated, showed that the interaction between complex and hsDNA was driven mainly by entropy. All the above indicated that the interaction mode of the complexes with DNA belonged to intercalative.关键词：succinic acid;1;10-phenanthroline;rare earth;herring sperm DNA;interaction138|206|2更新时间：2020-08-12
- 摘要：In order to enhance the cooling capacity of LED lamps and lanterns, we design a special LED bulb with straight chimney structure based on the principle of the chimney effect. We build a three-dimensional model by adopting Solidworks, and use its plug called Flow Simulation to simulate based on the model with the chimney height of 30 mm, chimney number of 6, and vent length of 2 mm. Through experiments, we find the highest temperature of this model is 69℃, lower than the simulation result only 1.66℃. It confirms the correctness of the simulation steps. Then, we study the influences of different chimney height, chimney number, and vent length on the highest temperature of LED bulb, respectively. The results show that the chimney effect can effectively improve the convection cooling performance of the LED bulb. When the chimney height is 45 mm, chimney number is 12, and vent length is 3.5 mm, the highest temperature of the LED chip is 61.04℃, which is 9.62℃ lower compared to the original model. Under the same set of model parameters, the highest temperature of the LED bulb has been reduced by 6.16℃ compared to the one in the model without a chimney structure, and the weight of radiator has also reduced 2.55 g. In conclusion, the designed LED bulb can better satisfy the working requirements under the nature convection conditions.关键词：straight type;LED bulb;chimney effect;highest temperature92|236|3更新时间：2020-08-12
- 摘要：The physicochemical characteristics of alpha and beta HMX which are isomers are quite different. In order to make a quantitative analysis of alpha and beta HMX mixtures, both pure and mixed alpha/beta HMX were detected and analyzed using of terahertz time-domain spectroscopy (THz-TDS) and THz absorption spectra were obtained. The THz absorption spectra of alpha/beta HMX mixtures were analyzed using linear fitting technique, and the forecast equations were set up to predict unknown samples. The results show that the absorption intensity of alpha/beta mixtures at 0.82 THz range has a good linear relationship with the content of alpha HMX. The absorption characteristics of alpha/beta HMX mixtures at 0.82 THz can be used for quantitative detection.关键词：α/βHMX;THz-TDS;absorption spectrum;quantitative detection114|28|3更新时间：2020-08-12
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