摘要:SrLiAl3N4:Eu2+ red-emitting phosphors were prepared in reducing atmosphere by high temperature solid-state reaction which could be effectively excited by ultraviolet and blue light. Luminescence properties and crystal structure of the phosphors were investigated. X-ray diffraction patterns and scanning electron microscopy image show that the sample is a pure phase of SrLiAl3N4.In the excitation spectrum (from 200 to 600 nm), there are two wide bands and peaks at 267 nm and 474 nm. The emission spectrum shows a wide band with a peak at 654 nm corresponding to the 5d→4f transition of Eu2+. The effect of the doping concentration of Eu2+ was investigated. The result shows that the luminescent intensity firstly increases and then decreases with the increasing of Eu2+ mole fraction, and the best doping mole fraction of Eu2+ is 0.4%. The concentration quenching will occur if Eu2+continue to be doped. The phosphors have good thermal quenching properties and quantum efficiency.
关键词:high temperature solid-state reaction;phosphor;red;Eu2+
摘要:Using dicyanodiamine and ammonium iodide as the precursors respectively, the SiO2/CNI composite photocatalysts with different mass ratio of SiO2 and CNI were successfully prepared by a bath-calcination process. The samples were characterized by X-ray diffraction(XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy(XPS), photoluminescence(PL) and UV-Vis diffuse reflection spectra(UV-Vis DRS), respectively. The results show that the photocatalytic activity of the SiO2/CNI samples are greatly enhanced, compared with pure CNI. When the mass ratio of SiO2 and CNI is 1:15, the activity of SiO2/CNI for photolysis water producing hydrogen is the highest, and the rate of photolysis water producing hydrogen of SiO2/CNI reaches 88.6μmol/h. The enhanced photocatalytic activities can be mainly attributed to the fact that the proper composite of SiO2 and CNI makes the recombination of the photoproduction electronic-hole pair be observably controlled, increases the absorption in 200-600 nm region and the absorption edge has a little shift to long wavelength.
关键词:dicyanodiamine;ammonium iodide;bath-calcination process;SiO2/CNI;photocatalysts;photolysis water producing hydrogen
摘要:A simple phosphorescent compound system for DNA detection was established by utilizing Mn (covered with 3-hydracrylicacid (MPA)) doped with ZnS quantum dots and mitoxantrone. By taking MTX as good electron acceptor, the room temperature phosphorescence (RTP) of Mn-doped ZnS quantum dots were quenched through photoinduced electron transfer principle. After the addition of DNA in system, DNA and MTX were combined through static electricity and intercalation, and a more stable compound was formed as well, which enable MTX removing from the surface of Mn-doped ZnS quantum dots and achieving RTP recovery of Mn-doped ZnS quantum dots. Thus, the trace detection of DNA was realized. The linear scope of this system for DNA detection and the detection limit is 0.1-20 mg·L-1 and 0.07 mg·L-1, respectively. This method can effectively avoid the interference from other coexisting substances, which can be used in rapid detection of DNA content in practical biological sample.
摘要:The carbon-doped nanoporous alumina films were prepared by two-step anodic oxidation in ethanol-oxalic acid mixture. This kind of doping method can effectively control the doping concentration of carbon. The thermoluminescence (TL) measurements show that the TL intensity of the films prepared in ethanol-oxalic acid mixture has been significantly improved comparing with the film prepared in oxalic acid, and the TL intensity increases with the carbon concentration. The TL intensity at 320 ℃ first increases then decreases with the elevated annealing temperature and reaches a maximum value at 500 ℃. The films prepared in oxalic acid show a linear dose response in the dose range of 10-50 Gy and a superlinear dose response in the range of 50-100 Gy, while the films prepared in ethanol-oxalic acid mixture show a linear dose response in the range of 10-100 Gy.
摘要:Li+, Na+ and Eu3+ co-doped Lu2O3 phosphors were synthesized by the high temperature solid-state reaction. The structure of the sample was characterized by XRD, the morphology was observed with scanning electron microscope, the excitation spectra and emission spectra were measured, and the effects of Li+, Na+ and Eu3+ dopingconcentration and the calcined temperature on the luminescence intensity of the synthesized samples were analyzed. The results show that the emission of the sample with 2.5%Li+, 1%Na+ and 5%Eu3+ co-doped Lu2O3 is the strongest in the four samples calcined at 800 ℃ in the air for 2 h. In the same condition, the luminous intensity of Lu2O3:5%Eu3+,2.5%Li+, 1%Na+ is 1.89 times than that only with 2.5%Na+ doping, 3.97 times than that only with 2.5%Li+ doping, and 6.43 times than that without Li+ and Na+ doping.
摘要:Due to many special applications, the 980 nm pumping source semiconductor lasers should have the characteristics of spectrum stability, low power consumption. Based on the optimization design of a 980 nm single mode semiconductor laser cavity length, cavity reflectivity and fiber Bragg grating reflectivity, the low threshold, high power 980 nm fiber Bragg grating external cavity semiconductor lasers with wavelength stability are developed. The pigtail output power of the low power consumption single mode semiconductor lasers with wavelength stability can reach 51 mW under 100 mA, 3 dB bandwidth of 0.16 nm. The side mode suppression ratio (SMRS) is greater than 40 dB. The pigtail output power of the device can reach 120 mW under 250 mA.
关键词:semiconductor lase;fiber bragg grating(FBG);external cavity structure;wavelength stabilization;low power dissipation
摘要:We prepared yellow phosphorescent OLED devices, which used R-4B, GIrl as the green phosphorescent dopant, CBP as the main body material. We investigated the BPhen as spacer layer between the red and green emitting layers to regulate currieries recombination. The device structure was ITO/MoO3(40 nm)/NPB(40 nm)/TCTA(10 nm)/CBP:GIrl(14%)(20 nm)/BPhen(x nm)/CBP:R-4B(6%)(10 nm)/BCP(10 nm)/Alq3(40 nm)/LiF(1 nm)/Al (1 000 nm). In this structure, x referred to six different thickness of BPhen in the devices. We studied its luminescent properties and controlled its spectra by adjusting the thickness of BPhen. The results show that appropriate thickness of BPhen can improve the performance of the device. When the thickness of BPhen is 6 nm, the performance of the device is the optimum. The maximum brightness is 11 270 cd/m2 at 16 V, and the maximum efficiency is 24.35 cd/A. Meanwhile, the green and red peaks almost have the same intensity in the spectra which means the purest yellow of all devices, and the color coordinates close to (0.5, 0.5).
摘要:Displacement damage effects due to neutron irradiations of charge coupled devices were presented through the analysis of the dark signals behavior in pixel arrays. When the fluence of neutron reached the predetermined point, the change of dark signal, dark signal non-uniformity, charge transfer efficiency and saturated output signal was measured off line. The major effect of neutron induced displacement damage on charge coupled device is the increase in dark signals as a result of carrier generation in the bulk depletion region of the pixel. Although the increase in the mean dark signals with neutron irradiation is important, the dark signals non-uniformity is generally the biggest concern for charge coupled device applications in space. Very large dark signals pixels can be produced when a collision occurs in a high electric field region of a pixel as a result of electric field enhanced emission. Another important performance parameter for a charge coupled device is the charge transfer efficiency, which is the fraction of signal charge transferred from pixel to pixel during read out. If a signal charge is trapped by neutron induced defect, and remains trapped for more than one clock cycle, it will be lost from the signal charge packet. Saturation output signal voltage does not have any obvious degradation even at the highest DDD level. The research will help the designers to know the radiation damage in charge coupled device and improve the tolerance by radiation hardening design.
关键词:charge coupled devices;neutron irradiation;displacement damage effect;charge transfer efficiency;dark signal
摘要:Solution processed HfInZnO (HIZO) thin film transistors (TFTs) with HfSiOx dielectrics modified by Al2O3 layer were fabricated. After the Al2O3 layer was inserted, the optical transmittance of HfSiOx films was hardly changed and the surface root mean square (RMS) roughness was decreased from 0.24 to 0.16 nm. The excellent surface was benefited to improve the interface properties between dielectrics and semiconductors of HIZO TFTs. Furthermore, the characteristics of thin film transistors were improved. The threshold voltage shift between forward and reverse sweep was decreased obviously. Simultaneously, the threshold voltage and subthreshold voltage were decreased, and the on to off current ratios and mobility were increased. Above all, the experiment results indicate that Al2O3 film is fit for using in TFTs as the interface modification layer to improve TFTs performance.
关键词:solution process;thin film transistors;modification layer Al2O3
摘要:We demonstrate a new one-step solution approach to prepare perovskite CH3NH3PbI3 films by adding polyvinylpyrrolidone (PVP) to the standard CH3NH3PbI3 precursor solution. The film morphologies, crystallinities, and optical properties of CH3NH3PbI3 perovskite layers are carefully studied by SEM, XRD, and UV-Vis. The results reveal that the perovskite film properties can be manipulated by incorporating a small amount of PVP. The absorbance of the film with PVP additive is significantly higher than the pristine film and the absorption peak is red shift by 20 nm, indicating the perovskite film with additive possessing better crystal structures. The use of PVP strongly affects the crystallization process of forming pure CH3NH3PbI3 and helps the formation of smooth film, leading not only to enhanced crystallization of CH3NH3PbI3 but also to significantly improved coverage of CH3NH3PbI3 on a planar substrate. The optimized power conversion efficiency (PCE) of CH3NH3PbI3 solar cells improved from 1.30% to 8.38% for the planar cell structure after the addition of 1% mass fraction of PVP. These results suggest that this new one-step solution approach is promising for controlling CH3NH3PbI3 growth to achieve high-performance perovskite solar cells.
关键词:perovskite solar cells;polyvinylpyrrolidone;additive
摘要:In order to study the silicon based semiconductor's electro-optic-thermal muti-field coupling characteristics and electric modulation problems, both the Poisson equation and the carrier continuity equation were introduced to calculate the carrier concentration distribution in the carrier transport procession. Drude Lorentz relation and K-K relation were also employed to discuss the effect of the carrier concentration on the refractive index and absorption coefficient. The heat deposited items were obtained by calculating electromagnetic dissipation. The coupled semiconductor basic equation, electromagnetic wave equation and energy equation were solved by using finite element method. With the effect of external voltage, initial concentration of carrier and heat transfer coefficient, the change of dielectric properties, optical transmission behavior of silicon based semiconductor were also analyzed by coupling solution and analysis. The results show that the reflective optical field mode of the semiconductor P area increases with the increasing of the applied voltage, and decreases with the increasing of the heat transfer coefficient. Using this mechanism, a scheme of electric thermal modulation for the space distribution of the reflection intensity was presented.
摘要:Tm3+/Ho3+ co-doped fluorotellurite microstructure fibers with low concentration of -OH were fabricated by using a rod-in-tube method. Pumped by 1 560 nm fiber laser, electron at Tm3+:3H6 jump to Tm3+:3F4, and then energy transfer from Tm3+ to Ho3+ can occure for the reason of small energy gap (745 cm-1) between Tm3+:3F4 and Ho:5I7, fluorescence at ~2.1 μm can be obtained with the transition from level of Ho3+:5I7 to Ho3+:5I8. By using a 1 560 nm Er3+ doped fiber laser as the pump source, an all-fiber lasing at 2 063 nm is obtained from a 18 cm Tm3+/Ho3+ co-doped fluorotellurite microstructure fiber. The corresponding slope efficiency is about 12.9%, the threshold is 163 mW, and the maximum unsaturated laser output power is 40 mW. The results indicate that the Tm3+/Ho3+ doped fluorotellurite microstructure fiber is a promising gain medium for 2.1 μm fiber laser.
摘要:High-power narrow spacing array stack is an effective solution to improve the power density of diode laser pumping sources, and its heat-sink structural design for package plays a vital role in cooling capacity management. Several important factors affecting thermal effect, such as stack spacing, ceramic thickness, the distance between ceramic and heat-sink thermostatic surface etc., were analyzed in this paper. The maximum temperature rises of the devices under different structure parameters were simulated using ANSYS finite element analysis method to get the variation laws and optimize these three parameters. According to the optimization results, an efficient cooling heat-sink structure suitable for high power density laser diode stack pumping source was designed. It can significantly improve the cooling effect and reduce consumption of cooling water pump-power.
摘要:For encapsulated thin film of the organic light emitting devices and flexible electronic devices, water vapor transmission rate (WVTR) is one of the most important parameters to evaluate the performance of thin film. In this paper, the method of calcium electrical test was studied. Based on this method, a new type of water vapor transmission measurement system was designed and developed, which can meet the requirement of accuracy and rapidity for WVTR testing of OLED. The results show that the precision of the system is 1×10-6 g·m-2·d-1 and the range is 10 g·m-2·d-1. The system can measure 20 samples rapidly and accurately at the same time. Deposited by atomic layer deposition, the WVTR of the different thickness Al2O3 thin films encapsulated layers (TFE) were studied. The results show that Al2O3 thin film has low water vapor barrier properties.
摘要:In order to improve the thermal performance of the high-power LED, the novel nanosilver paste with higher melting temperature and thermal/electrical conductivity was used as die-attach material, and Al2O3-based ceramic substrates were used to form a high-power LED chip-on-board (COB) architecture. To compare the effect of die attach material, high power COB LED modules were packaged by nanosilver paste, traditional Sn/Ag3.0/Cu0.5 solder and silver epoxy, respectively. The photoelectricity properties of three kinds of LEDs under various ambient temperatures from 27 to 120 ℃ were measured to evaluate their thermal management. The accelerated degradation testing under 100 ℃ was measured to evaluate the reliability. The test results show that the nanosilver paste is a very promising die-attach material for high power multi-chip modules packaging.
关键词:high power LED;COB packaging;nanosilver paste;photoelectricity property;reliability
摘要:In order to verify the laser induced breakdown spectroscopy (LIBS) is feasible for the detection of heavy metal elements in Chinese traditional medicine, using coptis chinensis, aconite root and poria cocos as detection object, a series of Cu element samples with different concentrations were prepared. 1 064 nm Nd:YAG solid pulse laser was used as the excitation source, the eight channel spectrometer was used for spectral data acquisition. Cu 324.7 nm was selected as characteristic spectral line, and the optimal delay time was determined for 0.5 μs. According to the different substrate conditions of coptis chinensis, aconite root and poria cocos, the appropriate internal standard parameters were selected, and the linear degree was 0.986, 0.931, 0.975, respectively. The results were compared with the results of direct calibration. The experiment results show that the internal standard method can improve fitting accuracy and LIBS can be used for the rapid detection of heavy metal Cu pollution of traditional Chinese medicine.
关键词:laser induced breakdown spectroscopy;traditional Chinese medicine;heavy metal;internal standard method;calibration curve
摘要:The color temperature of LEDs is influenced by injection current and junction temperature synchronizing change. The experimental data of GaN-based white LED color temperature dynamic changes were analyzed under the action of different pin temperature and injection current. The methods based on curve fitting and trend regression were applied to dynamic non-linear predictive model, among the color temperature, injection current and pin temperature. The predicted value fluctuation of color temperature was reduced to improve the accuracy of model calculations using quadratic regression for coefficient of nonlinear model. The sampling tests compared with the model calculations show that the relative error between the calculated value and the actual measured value is less than 1.5%.
摘要:A SU-8 polymer waveguide sensor based on local surface plasmonresonance( LSPR ) was designed. The extinction model of Au nanoparticles was established. Influence of Au nanoparticle' radius and refractive index of analyte on LSPR curve was analysized. The theoretical analysis results show that the resonance wavelengths of LSPR sensor move to longwave direction when the refractive index of the analyte increases. With the increasing of Au nanoparticles' radius, the sensitivity increases and the resonance absorption peak gradually changes from one peak to two peaks. One of the peaks locates near 520 nm wavelength, mainly caused by surface plasmon absorption. Another peak which is caused by surface plasmon scattering, moves to longwave direction gradually with the increasing of Au nanoparticles' radius.
摘要:A facile preparation of highly fluorescent Ag nanoclusters (AgNCs) was synthesized using a surfactant-free N,N-dimethylformamide (DMF) reduction method by reflux at 140 ℃. The as-prepared samples were characterized by UV-Vis absorbtion spectroscopy, fluorescence spectroscopy and HRTEM. The results show that the AgNCs with small size emit strong blue fluorescence possessing excellent water-solubility and photostability. Moreover, the fluorescence from AgNCs can be efficiently quenched by Hg2+. By virtue of the specific response, a new, simple, selective and sensitive fluorescent method for detecting Hg2+ has been developed based on DMF-AgNCs. This method shows a good linear relationship within the concentration range of 5.0×10-9~1.5×10-7 mol/L, the detection limit was 3.0×10-9 mol/L, and the correlation coefficient R2= 0.995 8.
摘要:The effects of current-temperature stress on the reliability of LED were investigated, and the failure mechanism was analyzed from the structure of LED. It is found that the current and temperature have different influences on the reliability of LED. When LEDs are applied current accelerating stress, the degradation of phosphor is the main failure mode which can cause the increasing of correlated color temperature and decreasing of red ratio. When LEDs are applied temperature accelerating stress, the structure of chip would change, which leads to the blueshift of peak wavelength. In addition, the structure of housing also appears aging at high temperature. The temperature stress has greater effect on the reliability than current stress when the current stress and temperature stress are applied together. The attenuation of luminous flux under current-temperature stress is greater than the sum of current and temperature stress working alone, which namely implies that the current and temperature stress do not have the features of linear superposition.