最新刊期
卷 36 ， 期 6 ， 2015
- 摘要：Eu3+ doped β-Ga2O3 powders were prepared by hydrothermal method. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and photoluminescence spectra were used to characterize the structure and properties of β-Ga2O3: Eu3+ powders. The results reveal that the obtained samples are monoclinic β-Ga2O3 powders. Under the excitation of 325 nm He-Cd laser, the strongest emission peak is located at 612 nm, corresponding to the 5D0→7F2 transition of Eu3+. β-Ga2O3:Eu3+ powders have high photocatalytic degradation rate for methyl orange under simulated solar irradiation, and the photocatalytic degradation rate of methyl orange is up to 75% after 2 h degradation.关键词：hydrothermal method;β-Ga2O3:Eu3+;photoluminescence123|26|1更新时间：2020-08-12
- 摘要：Two sized CdSe quantum dots (QDs) were synthesized, and the polymethylmethacrylate (PMMA)-QD samples were annealed. The photoluminescence (PL) spectra of the samples were measured, and the annealing-induced effects on these two sized QDs were compared with colorimetric study. The QDs with small size tend to aggregate in annealing process, which results in the bimodal size distribution phenomenon. Caused by annealing, the CIE coordinate of small CdSe QDs shifts up to the green region from white region. The bigger QDs with better thermal stability have similar emission color before and after annealing, because the CIE coordinate in green region moves toward right slightly in annealing process. After all, the better thermal stability of bigger QDs makes them more suitable for the application of light emitting display.关键词：CdSe;quantum dots;annealing;bimodal size distribution;defect states143|445|1更新时间：2020-08-12
- 摘要：For the sake of investigating the photoluminescence (PL) characteristics and the mechanims from zinc oxide nanocrystals, the crown-like nanostructural samples prepared by vapor phase transport method were excited by laser pulse and Xe-lamp. Under 1 100 nm and 1 150 nm excitation, the ultroviolet emission at 388 nm and visible emission at 575 nm were observed. Based on the third disturbation theory of the interaction between intensive light field and matter and the relationship between the emission intensity and excitation power, it is confirmed that the emission performances under 1 100 nm and 1 150 nm excitation should be attributed to the three-photon absorption process and the second harmonic generation effects. Moreover, the redshift phenomena of the ultroviolet emission was analyzed based on the exciton-exciton inelastic collision recombination process.关键词：zinc oxide;photoluminescence;three-photon absorption;second harmonic generation effect137|184|2更新时间：2020-08-12
- 摘要：In order to research the origin of red emission in NaYF4:Yb3+,Er3+ upconversion nanoparticles, the dependence of upconversion fluorescence intensity on the excitation power was studied in this paper. The bare core and core/shell NaYF4:Yb3+,Er3+ nanoparticles were synthesized, and their emission spectra were analyzed in detail. It is found that the cross-relaxation has great influence on the red emission in NaYF4:Yb3+,Er3+ upconversion nanoparticles. Different from bare core NaYF4:Yb3+,Er3+ nanoparticles, the cross-relaxation plays a leading role for the red emission in core/shell NaYF4:Yb3+,Er3+ nanoparticles, and the multi-photon relaxation can be almost ignored.关键词：upconversion;excitation power dependence;cross-relaxation;energy state population239|141|1更新时间：2020-08-12
- 摘要：Micro/nano-sized ZnO crystals with different shapes were fabricated by a simple hydro/solvothermal method using zinc acetate and methenamine as precursors. The morphology and size of ZnO crystals are strongly dependent on synthetic conditions. The growth of the polar plane can be suppressed due to the ethylenediaminetetraacetic acid disodium salt and citric acid compound selective adsorbing on the polar plane facets by the chemical adsorption. The selective adsorption makes the shape of ZnO crystal be tunable. Raman spectra confirm that grain size is smaller as ZnO synthesized in citric acid solution. The photoluminescence shows the transitions of exciton and defects in ZnO.关键词：ZnO;microstructure;Raman spectroscopy99|136|0更新时间：2020-08-12
- 摘要：Sr2.95SiO5:0.05Eu phosphors were synthesized by high temperature solid phase method, and the phosphor phase, excitation and emission spectra, particle size distribution, surface morphology were investigated with the help of X-ray diffraction, spectrometer, granulometer and scanning electron microscopy. The influence of crucible lid-covering technology on the performance of the product was analyzed. The results indicate that the luminous intensity of the samples increases with the increasing of the crucible close degree. Crucible with lid is of benefit to the product for high purity Sr3SiO5 phase. The particle size of the sample with crucible lid-covering is larger, but the size distribution is uniform.关键词：silicate;phosphor;lid-covering technology;property135|79|0更新时间：2020-08-12
- 摘要：In order to solve the problem that GaN-based vertical structure LEDs (VS-LEDs) suffer from efficiency droop under high current injection level, hybrid quantum wells (HQWs) with coupled quantum wells (CQWs) and normal quantum wells (NQWs) were employed. Compared to VS-LEDs with NQWs, VS-LEDs with HQWs had better properties, wherein forward voltage reduced by 0.68 V and light-output power increased by 53.0% at a forward current of 350 mA. Meanwhile, the relative external quantum efficiencies of VS-LEDs with NQWs and VS-LEDs with HQWs reduced to 37.7% and 67.5% of their maximum, respectively. The results reveal that the efficiency droop of LEDs can become less severe by exploiting HQWs.关键词：GaN;vertical structure LEDs;hybrid quantum well;efficiency droop106|171|2更新时间：2020-08-12
- 摘要：Fluorescent nondoped white organic light-emitting diodes (WOLEDs) were fabricated by using three ultrathin layers, including red, green and blue, separately monochromatic emission layers. The structure of the device is ITO/MoO3(5 nm)/TCTA(40 nm)/C545T(1 nm)/TCTA(2 nm)/BePP2(1 nm)/Bphen(2 nm)/DCJTB(1 nm)/Bphen(30 nm)/LiF(1 nm)/Al(1 000 nm). The maximum luminance and current efficiency reach 16 154.73 cd/m2 and 11.58 cd/A, respectively. The Commissions Internationale De L'Eclairage (CIE) coordinates at (0.322 2, 0.335 1) are observed at 7 V bias and show a very slight variation of (0.017 4, 0.002 9) in a wide range of voltages. Compared with doped white structure device, ultrathin structure white device has high current efficiency and stable electroluminescence spectrum, which is attribute to the excitons being confined effectively in the recombination zone by the charge trapping effect of ultrathin layers.关键词：organic semiconductor;fluorescent material;ultrathin emitting layer;white organic light-emitting devices186|131|4更新时间：2020-08-12
- 摘要：Multi-shadow is an important problem for the reading lamp. In order to analyze the control factors of the multi-shadow of LED array on the curved surface plate, some experiments were designed by applying Taguchi method and simulated via TracePro software. After that, ANOVA theory was integrated to evaluate the influence of the control factors to the illumination. So that the control factors can be optimized efficiently. The experiment results show that the number of LEDs is the main influence on multi-shadow(50.17%)and the optimum combination of minimum multi-shadow is 1.19 mm. Furthermore, the best combination of the control factors can be obtained by adjusting the angle between the LED chips and the optical axis.关键词：Taguchi method;cured surface;LED illumination;multi-shadow problem;ANOVA110|150|3更新时间：2020-08-12
- 摘要：The luminescence performance characterized by luminous flux, color temperature, chromaticity coordinate of three-dimensional light emitting diodes (LEDs) has been investigated by using different phosphor coating methods. The LED die was directly coating with mixed phosphors and silicone which have the maximum total luminous flux. However, this encapsulation incurs luminous uneven problem of front and back which limit three-dimensional luminescence application. Therefore, this work attempts to use the silicon and spreading powder to change the light path on the basis of less loss of luminous flux. Experimental results indicate that the brightness uniformity can be improved when increasing silicon layer between LED die and phosphor, while spreading powder layer would induce significant light attenuation. Moreover, the three packing have similar light angle. Therefore, silicon layer provides an alternative packing solution for three-dimensional LED light application.关键词：three-dimensional light-emitting;LED lamp;luminous flux;color temperature;chromaticity coordinate109|210|0更新时间：2020-08-12
- 摘要：Amplified spontaneous emission (ASE) properties of organic material EnBOD were studied under ultraviolet pulse laser pumping. EnBOD sample in dilute toluene solution shows narrow-band absorption and PL spectra, with the maximum peak located at 508 nm and 527 nm, respectively. The ASE efficiency changes with the solution concentration. The maximum ASE efficiency of 22.6% was obtained when the EnBOD sample concentration is 0.008 mol·L-1, in which the ASE threshold is 29.5 kW·cm-2, ASE peak is 542 nm and full width at half maximum is about 12.4 nm. The ASE output intensity attenuated to 61.2% of the initial strength under the pulse pump frequency of 200 000. The results indicated that EnBOD is a kind of laser material with low ASE threshold and good light stability.关键词：organic material;amplified spontaneous emission;photostability124|202|2更新时间：2020-08-12
- 摘要：The effect of different solvents on the performance of polyethylenimine ethoxylated as a cathode interfacial layer in inverted polymer solar cells is investigated. Four solvents, distilled water (DW), isopropanol (IPA), 2-methoxyethanol (MEA) and 2-ethoxyethanol (EEA) were chosen as the diluting solvents of PEIE to fabricate devices. Surface-charge accumulation and carrier collection at interface between ITO and PEIE layer fabricated from four different solutions are analyzed and compared by the measurements of transient photocurrent characteristic and photo-excitation capacitance-voltage (C-V) profiling. The results show that the photoelectric conversion efficiency (PCE) of the MEA device reaches 3.61%, compared with the DW device (2.66%) increased by 24%.The morphology of PEIE film depends on PEIE solvents, and the traps tracing to the morphology of PEIE layer lead to different charge accumulation and charge collection efficiency, which further affects the performances of devices.关键词：polymer solar cells;solvent;morphology;charge accumulation;polyethylenimine ethoxylated174|222|1更新时间：2020-08-12
- 摘要：The spatial coherence properties of high power vertical cavity surface emitting lasers (VCSELs) triangle-arrays were studied based on the theorem of Hermitian-Gaussian beams and spatial coherence. The far-field divergence angle and spatial coherence degree were gauged using the second-moment method and spatial coherence degree integral average value method for the devices of 980 nm wavelength VCSEL arrays. The influence of array-units distance on far-field characteristics and coherent characteristics was also discussed. With the increasing of array element spacing from 200 μm to 300 μm, the far-field divergence angle of VCSEL arrays device increases from 9.5° to 12.5°, and the spatial coherence degree decreases from 0.719 to 0.526, while the unit aperture of triangle array is 150 μm. Under the same injection current condition, the optical powers of three VCSEL array devices are almost equal.关键词：VCSEL triangle-arrays;optical beam quality;spatial coherence126|181|2更新时间：2020-08-12
- 摘要：A new kind of charge generation layer (CGL) without doping: LiF/Al/C60/m-MTDATA was reported in this work, and a series of tandem OLED(TOLED) were fabricated using this new CGL. The TOLED offered a max current-efficiency of 48.4 cd/A and a power-efficiency of 19.4 lm/W, respectively, which increased by 2.95 and 1.65 times compared with the reference device. We also constructed a series of reversed devices with several CGLs, and by exploring the effect of the thicknesses of C60 and Al films and the evaporating ratio of Al on the new CGL, charge generation and dissociation mechanism in the CGL were made clear.关键词：organic light-emitting device;charge generation layer;tandem114|198|2更新时间：2020-08-12
- 摘要：Novel hybrid white organic light-emitting diodes (HWOLEDs) based on blue-green fluorescent MQAB and red phosphorescent Ir(MDQ)2acac materials were fabricated. 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)-benzene (TPBI), 1,3-bis(triphenylsilyl)benzene (UGH3) or a mixture of the two at different ratios was used as a spacer layer. It is found that the mixed spacer of TPBI and UGH3 is able to tune the hole injection/transport effectively. The optimized HWOLEDs with a spacer of m(TPBI):m(UGH3)=1:1 exhibits a luminance of 14 700 cd/m2 and a current efficiency of 11.60 cd/A with an excellent color stability. In comparison with the devices using spacer of pure TPBI or pure UGH3 layer, the current efficiency from the device using mixed spacer enhanced 200%-300%.关键词：white organic light-emitting diodes (WOLED);hybrid fluorescence and phosphorescence;mixed spacer layer110|77|2更新时间：2020-08-12
- 摘要：In order to enhance the light-output performance of GaN-based high-voltage light-emitting diodes (HV-LEDs), the width of isolation trench between light-emission cells was optimized. The electrical and optical performance is the best while the width is 20 μm. When the injection current is 20 mA, the forward voltage is 50.72 V, the light-output power is 373.64 mW, and the electro-optical conversion efficiency is 36.83%. Then, four chips were connected in series and packaged in reflective aluminum substrate or ceramic substrate using chip-on-board (COB) technology. Since the thermal conductivity and reflectivity are higher for reflective aluminum substrate comparing to ceramic substrate, the packaged HV-LEDs with reflective aluminum substrate show better light-output performance at a high injection current or a high temperature. On condition that the injection current is 20 mA and the substrate temperature is 20 ℃, the forward voltage and the light-output efficiency of HV-LEDs packaged using reflective aluminum substrate are 198.9 V and 122.2 lm/W, respectively.关键词：high-voltage light-emitting diode;chip fabrication;package substrate;light-output efficiency128|143|1更新时间：2020-08-12
- 摘要：Detailed transient current response characteristics of organic light-emitting diode (OLED) were investigated. Transient current response curve can be divided into three partitions: positive current spike (IP), stead-state current (IS) and negative current spike (IN). It is found that the positive and negative current peaks correspond to the charging and discharging process of space charges near electrode/organic interface, respectively. Linear relationship between the current spikes and pulsed voltage amplitude is found. Larger IN than IP is induced by the difference between Femi level of electrode and the highest occupied orbital level (HOMO) of organic materials. Different duty-ration dual pulsed voltages are modulated to investigate the relation between current response and space charges. It is found the space charge charging and discharging threshold duty-ration is only depended on the hole injection barrier and independent with internal device structure.关键词：organic light-emitting diode;transient current response;interface;space charges140|255|1更新时间：2020-08-12
- 摘要：The reaction mechanism between pioglitazone hydrochloride (PGH) and bovine serum albumin (BSA) was studied by fluorescence quenching method and synchronous fluorescence method under different temperatures. The results show that the conclusions of two methods are identical on the quenching mechanism, type of interaction force, binding constants, binding location, synergistic effect, energy-transfer parameters of pioglitazone hydrochloride with bovine serum albumin, etc. These indicate that the synchronous fluorescence spectroscopy can be used to replace the traditional fluorescence spectroscopy to study the reaction mechanism of drugs with protein.关键词：fluorescence spectroscopy;synchronous fluorescence spectroscopy;pioglitazone hydrochloride;bovine serum albumin;reaction mechanism117|269|4更新时间：2020-08-12
- 摘要：Color partition method is the main method of multi-color reproduction. In this paper, the whole color area of 7 primary colors was divided into 6 partitions in group of 3 primary colors, and principal component analysis (PCA) was used to dimensionality reduction of the color spectrum reflectance. A three layers BP neural network was established to describe the transformation model of dot area coverage and spectral reflectance. Genetic algorithm (GA) was adopted for optimizing the weight threshold of BP NN to improve the prediction accuracy of model. Experimental results show that GA-BP model has higher prediction precision and stability compared with BP ANN and cell neugebauer model. When the number of training sample is 64 and test sample is 216 in the partition, the optimized model can predict color with the accuracy of 1.669 mean ΔEab* and 0.7% spectral RMSE. By comparing with the non-optimized model with the training sample numbers of 125, 216, 343 (mean ΔEab* are 3.267, 2.776, 2.175 and spectral RMSE are 0.97%, 0.79%, 0.76%), the prediction accuracy of GA-BP model with the training sample numbers of 64 is equal to the accuracy of the non-optimized model with the training sample number of 343. The results show that GA-BP model can reach high precision color reproduction with small amount of samples, and have good portability in practice.关键词：BP neural network;genetic algorithm;principal component analysis;color prediction model;spectral reflectance144|117|3更新时间：2020-08-12
- 摘要：A new kind of optofluidic varifocal lens driven by hydraulic pressure drop was put forward in this paper. The whole microfluidic device consisting of micro-channels and micro-cavities was made of polydimethylsiloxane (PDMS) material and produced by soft lithography. COMSOL simulation showed the deformations of micro-cavity under different hydraulic pressure drops, forming convex lens and concave lens. The focal lengths and light path diagrams of all sorts of lens were obtained by using the ZEMAX optical simulation software. In the end, an effective method to correct spherical aberration of convex lens was proposed.关键词：varifocal lens;optofluidics;simulation;COMSOL;ZEMAX187|185|10更新时间：2020-08-12
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