最新刊期
卷 39 ， 期 6 ， 2018
- 摘要：Herein, degradation behavior and mechanism of K2SiF6:Mn4+ (KSFM) red phosphors in hot and humid environment were investigated. The attack by moisture can induce the emission intensity of KSFM phosphors to decrease and limit their applications in white LEDs. The moisture degradation of KSFM would be aggravated at higher temperatures. Under 85% humidity and 70℃ for 6 h, the relative brightness of K2SiF6:7%Mn4+ falls to 25% of the initial value. With the increase of Mn4+ contents in KSFM phosphors, more significant emission intensity decrease in hot and humid environment is obtained. Based on the comparative analysis of XRD, morphology and optical properties of KSFM phosphors before and after heat-moisture treatments, the degradation of KSFM can be attributed to the reaction between environmental moisture and phosphors. The reaction products, which are located on the particle surface and exhibit broad absorption bands between 400 and 700 nm, can decrease the excitation efficiency and re-absorb the emitted light of phosphors, lead to the degradation of KSFM phosphors in hot and humid environment. It is also found that the hydrothermal post-treatments result in the increase of the particle size of phosphors and the improvement of their crystalline, and thus significantly enhance the moisture resistance of KSFM phosphors. The hydrothermally post-treated K2SiF6:7%Mn4+ phosphor can retain 80% of the initial brightness after exposure a hot and humid environment (85% humidity and 70℃) for 6 h.关键词：K2SiF6:Mn4+;red phosphors;white LED;degradation;moisture-resistance204|610|4更新时间：2020-08-12
- 摘要：In order to explore the growth process of NaLuF4 nanocrystals in detail, we prepared a series of NaLuF4:Yb3+/Tm3+ nanomaterials by using a self-developed automatic nanomaterial synthesizer which can precisely control the experimental parameters. The phase analysis of samples prepared at different reaction temperatures(285, 295, 305℃) shows that the NaLuF4 nanocrystals follow the similar growth law with the increase of reaction time. We can obtain pure β-NaLuF4 nanocrystals with small size(less than 50 nm), monodispersity, and narrow size distribution at different temperatures. On the other hand, we measured the upconversion spectra of β-NaLuF4:Yb3+/Tm3+ nano-materials which prepared under 285, 295, and 305℃. These results indicate that the luminescence intensity of samples increase first and then decrease with the increase of reaction temperature. In addition, the luminescence of sample in ultraviolet region is stronger than that of the near-infrared region. For example, the intensity of 361 nm emission peak is twice large compared to that of 800 nm emission peak, which makes the nano-material suitable for near-infrared excited ultraviolet sensitive materials.关键词：NaLuF4;growth process;small size;crystallinity;upconversion131|118|5更新时间：2020-08-12
- 摘要：Eu3+ doped potassium-sodium niobate(KNN) ceramics were fabricated by a solid-state reaction method. X-ray diffraction, photoluminescence spectra and LCR meter were used to characterize the structure and properties of Eu3+ doped KNN ceramics. XRD results show that the obtained KNN ceramics are orthogonal architecture. The relative density and Eu3+ doping concentration can affect the luminescent properties of KNN ceramics, Eu3+ doping mole fraction is a key factor. 4% Eu3+ doped KNN ceramics at 930℃ sintering temperature has excellent red-orange luminescence under 396 nm excitation, and the strongest emission peak is located at 614 nm, corresponding to 5D0-7F2 transition of Eu3+. The piezoelectric properties of all samples are measured after polarized at 3 kV/cm and 110℃ for 30 min. The results reveal that the piezoelectric properties can be improved by increasing the Eu3+ content and the ceramics relative density. KNN-4%Eu3+ ceramics shows good piezoelectric and dielectric performance. Piezoelectric constant D33 reaches up to 98 pC/N, dielectric constant ε is 217, dielectric loss tanθ is 0.199(1 kHz, 100℃) and Curie temperature Tc is 426℃.关键词：solid-state method;KNN;photoluminescence;dielectric properties;piezoelectric ceramics169|241|1更新时间：2020-08-12
- 摘要：Nano-textured multi-crystalline silicon solar cells were fabricated on industrial production line. The nano-textured multi-crystalline silicon solar cells showed an improved short-circuit current as compare to traditional multi-crystalline silicon solar cells, and resulting in an increasing amount of >0.4% for power conversion efficiency and up to 19.1%. The light reflectance spectra and the external quantum efficiency of the nano-textured multi-crystalline silicon solar cells were investigated. The improved power conversion efficiency was attributed to enhanced light trapping and light response by the nano-structure. The results confirm that the nano-textured multi-crystalline silicon solar cells can be produced by using the industrial production process, and has high power conversion efficiency.关键词：multi-crystalline silicon solar cells;nano-structure;reactive ion etching;power conversion efficiency126|262|1更新时间：2020-08-12
- 摘要：The Si/NiO heterojunctions with and without Na or Cu doping were prepared by the magnetron sputtering method. The best rectifying characteristics appears in the Si/NiO:Na heterojunction, where the average optical transmittance can reach to 70% in the visible range, which may be explained by the reduced defects due to the improved crystallization. The fitted I-V curve of Si/NiO:Na heterojunction indicates that the interface state also affects the rectifying property. Good rectifying property hasn't been observed in Si/NiO and Si/NiO:Cu heterojunctions because of the appearance of more defects. These results are also evidenced by XRD, SEM, AFM and UV results.关键词：NiO;Na doping;Cu doping;heterojunctions;rectifying property109|139|0更新时间：2020-08-12
- 摘要：The molecular structure and the formation of chemical bonds of organic semiconductor materials PTCDA were analyzed, and the lattice structure of crystal plane index (100)Si single crystal was discussed. On this basis, the mechanism of the growth of PTCDA molecules on the crystal surface of P-Si single crystal(100) was reviewed, and the sample PTCDA/P-Si(100) was prepared. X-ray diffraction(XRD) measurement shows that there are only α-PTCDA phases in the P-Si(100) pace. XPS test shows that the four hydroxyl O atoms in the acid anhydride of PTCDA molecular are covalently bound to the C atom in the interface layer, and the binding energy is 532.4 eV; the eight C and H atoms covalently bind in the periphery of perylene nuclear group, and the binding energy is 289.0 eV. At the interface, Si atoms with 2s and 2p electrons on the surface state danglingbond are bound to the C and O atoms in the acid anhydride of PTCDA molecular to form a C-Si-O bond and C-Si bond, thereby constructing a stable structure of interfacial molecules.关键词：organic semiconducot material PTCDA;P-type Si(100) crystal face;growing mechanism132|334|0更新时间：2020-08-12
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First-principles GGA+U Investigation on The Electronic Structure and Optical Properties of Zn1-xMgxO
摘要：Mg substitution in ZnO can form ternary alloys Zn1-xMgxO(ZMO)(0 ≤ x ≤ 0.25)which has wide band gap and tunable electronic properties. So ZMO has a large application in transparency electrode of thin-film solar cells and optoelectronic device. The electronic structure and optical properties of ZMO ternary alloys were calculated using first-principles calculations based on the density functional theory combined with GGA+U approach. The calculation results show that the doping of magnesium leads to an apparent change of the electronic structure of ZMO. With Mg concentration increasing, the band gap of ZMO widens from 3.32 eV(x=0) to 3.78 eV(x=0.25). In addition, the absorption edge exhibits a blue shift with Mg concentration increasing. At the same time, the reflectivity and loss-function show mainly in the ultra-violet region, which is similar to those of optical absorption. The calculation results are in good agreement with the experiment.关键词：ZMO;first-principles;electronic structure;optical properties140|258|2更新时间：2020-08-12 - 摘要：In order to compress the pulse width of MOPA all-fiber Q-switched lasers, the basic parameters of the resonator were studied. Firstly, the expression of the pulse width was deduced according to the rate equation theory, and the relationship between the expression parameters and the pulse width was established by numerical solution. Then, the effects of gain fiber length, cavity output transmittance and Q-switch performance on the output pulse width of all-fiber Q-switched source were analyzed and the results were verified experimentally. Finally, an all-fiber Q-switched laser was constructed by optimizing the parameters. At the repetition frequency of 20 kHz, the seed laser output with pulse width of 54 ns and average power of 0.86 W was obtained. At the repetition frequency of 100 kHz, the seed light with the pulse width of 142 ns and the average power of 1.66 W was used to prevent large and main power amplification, and finally the stable pulse laser output with average power of 120 W, pulse width of 180 ns and spectral width of 0.67 nm was obtained. The Q-switched fiber lasers can be constructed by optimizing the AOM performance and reducing the length of the gain fiber to optimize the pulse width of the resonator.关键词：pulse width;all-fiber;Q-switched153|378|1更新时间：2020-08-12
- 摘要：The effects of the interlayer on the white organic light-emitting diodes(WOLEDs) was studied by inserting the 2 nm TCTA and 2 nm TmPyPb interlayer into the interface between different emission layers respectively based on the structure of ITO/NPB/TCTA/Ir(MDQ)2(acac):TCTA/FIrpic:TmPyPb/Ir(ppy)3:TmPyPb/TmPyPb/LiF/Al. The results show that the distribution of exciton and energy transfer can be adjusted and influenced because of the existence of interlayer. The peak efficiency of the high quality WOLEDs with two interlayers is 22.56 cd/A.关键词：organic light-emitting diodes(OLEDs);interlayer;primary three colors;energy transfer152|224|1更新时间：2020-08-12
- 摘要：Study on ionizing radiation response characteristics of four types of CCD and CMOS pixel image sensors were presented. The photon response event distribution, average pixel value and typical photon radiation response events of sensors were analyzed by comparing the structural characteristics of various pixel sensors at different dose rates. The reasons for the ionizing radiation response difference were further discussed. The experimental results show that the degree of photon response is related to the radiation dose rate. The channel transmission mode of CCD pixel sensor makes the radiation response of each pixel easier to interfere with each other. The average pixel value has obvious gradient with the different dose rates. The output signal fluctuates around the mean pixel value, and the fluctuation range of CCD pixel sensors are smaller. The response of each pixel of CMOS pixel sensor to photon is more obvious. The signal produced by the majority of pixels to the photon is drowned by the crosstalk signals caused by the neighboring pixels in CCD pixel sensors. The number of pixels corresponding to photon response in the typical radiation response region of each pixel sensor increases with large dose rate, which indicates that the response event is not the behavior of any single photon, but reflects the process of simultaneous deposition of energy by multiple photons in the region.关键词：complementary metal oxide semiconductor(CMOS);charge coupled device(CCD);pixel image sensor;photon ionizing radiation;radiation response characteristics152|33|3更新时间：2020-08-12
- 摘要：Mo/Cu source/drain(S/D) electrodes for amorphous InGaZnO thin film transistors(a-IGZO TFTs) were investigated. The experimental data indicate that the single-layer Mo electrodes have good adhesion to gate insulators, smaller surface roughness, and higher resistivity, whereas the single-layer Cu electrodes possess bad adhesion to gate insulators as well as the serious Cu atom diffusion problems, larger surface roughness, and lower resistivity. To complement each other's advantages, the double-layer Mo/Cu electrodes as well as the corresponding a-IGZO TFTs are designed and fabricated, which exhibits good performance parameters(field effect mobility of 8.33 cm2·V-1·s-1, threshold voltage of 6.0 V, subthreshold swing of 2.0 V/dec, and on-off current ratio of 1.3×107). This proved the feasibility and practicability of the double-layer Mo/Cu source/drain electrodes for the mass productions of a-IGZO TFTs.关键词：flat panel displays;amorphous InGaZnO;thin film transistors;Mo/Cu electrodes;magnetron sputtering139|227|2更新时间：2020-08-12
- 摘要：A high efficiency all-solid-state green laser was reported which was double end-pumped by the laser diode(LD) Nd:YAG, passive Q-switched by Cr4+:YAG, and critical phase matched by LBO intracavity. The thermal effect of double end-pump YAG laser was analyzed. In the experiment, double end-pump of LD is used to conduct the conduction cooling of Nd:YAG with the U-type parallel flat cavity structure. When the input power is 33.8 W, the output power of linear polarized light with 10 kHz passive Q-switch is 8.21 W which leads to the output power instability of 6.72 W and frequency doubling efficiency of 86%. The output beam is the fundamental model and M2 reaches 1.4. The experiments show that the double end-pumped YAG frequency multiplication laser has quite high conversion efficiency.关键词：double end-pumping;passive Q-switched;intracavitary frequency;partially polarized light;high efficiency206|228|1更新时间：2020-08-12
- 摘要：B doped ZnO(BZO) films were prepared on glass substrate by low pressure chemical vapor deposition(LPCVD) method. BZO films were annealed in hydrogen atmosphere and then were used as front contact structure for fabrication of amorphous silicon thin film solar cells. The results show that the carrier concentration of BZO films has no change after annealing in the hydrogen atmosphere, but the carrier mobility dramatically increases, which lead to great enhancement of electrical conductivity of BZO films. When a thinner BZO film with higher transmittance workes as the front contact structure, the light-generated current density increases by 0.3-0.4 mA/cm2 and the conversion efficiency of amorphous silicon thin film solar cells is improved by 0.2%. The results in this paper can provide a method for further improving the conversion efficiency of amorphous silicon thin film solar cells by optimizing optical and electrical properties of front contact of BZO thin films.关键词：BZO thin film;front contact;transmittance;amorphous silicon thin film solar cells;conversion efficiency129|167|0更新时间：2020-08-12
- 摘要：In-phase mode operation can be obtained from implant-defined vertical cavity surface emitting laser arrays. However, the non-uniformities in the fabrication process induce the relative phase difference, which can impact the beam quality. In this paper, multi contacts were designed to make current injection into each element separately. In-phase mode with high beam quality was achieved in 3-element arrays. The divergence of the array is only 3.4°. About 25.6% of total power is concentrated in the central lobe. The line width in the spectrum is 0.24 nm. The side mode suppress ratio(SMSR) is 28 dB. The method can improve the beam quality of coherently coupled arrays effectively. It can also mend the non-uniformity of the elements in fabrication process, improving the reliability and practicability. The method of proton implantation is simple and of low cost, which can be an alternative to fabricate coherently coupled arrays.关键词：proton implantation;vertical cavity surface emitting laser(VCSEL);coherent coupling multi contacts122|188|4更新时间：2020-08-12
- 摘要：In order to improve the reliability of semiconductor laser devices, the effect of AlN transition heat sink with different ratio AuSn solder on the performance of semiconductor laser devices was studied. The 975 nm dies were grown using MOCVD. The surface morphology, voidicity, spectral characteristics, thermal resistance and lifetime of the semiconductor laser device were measured. Compared to the devices on the AlN transition heat sinks with more Au, the devices on the sinks with less 72% Au that the surface morphology was significantly different and the average wavelength increased about 5 nm, were prematurely lost in the life test. It was found that the Au content in the AuSn solder should be controlled within a certain range, preferably greater than 72%, less than 80%, in order to ensure the quality of packaging equipment. That became important guiding significance for the actual production and the user.关键词：AuSn solder;semiconductor laser;AlN transition heat sink;thermal resistance143|452|0更新时间：2020-08-12
- 摘要：A 2 μm subwavelength high contrast grating(HCG) mirror based on GaSb was designed and investigated, which had a low index grating layer structure. These designs of structure were optimized by use of rigorous coupled wave theory to maximize the reflectivity and bandwidth to meet the requirements of a VCSEL cavity mirror. The mirror has excellent reflectivity for TM mode of the 2 μm wave band. The ratio of bandwidth to design wavelength is 15%(reflectivity R>99%). When the reflectivity R>99.9%, Δλ/λ0>9.5%, and the bandwidth center wavelength is 2.003 μm. At the same time, the reflectivity of TE mode does not exceed 70.20%. Several parameters in the mirror structure have larger fabrication tolerances, and the thickness is less than 1.1 μm, which is beneficial to the monolithic integration on vertical cavity surface emitting semiconductor lasers.关键词：subwavelength grating;mirror;VCSEL;GaSb115|388|1更新时间：2020-08-12
- 摘要：The matching of AM1.5 standard solar spectrum in visible light (380-780 nm) with standard light source of CIE-D65 was realized using monochromatic LED, and the matching algorithm of the target spectrum was put forward using active set algorithm. The peak wavelength and FWHM of Epitex's high-power monochromatic LED were used as the effective data set, and a database was established. The maximum correlation index R2 was used as the optimization objective. The least squares solution of overdetermined equations was solved by MATLAB programming, and the type and quantity of monochromatic LED needed for fitting were obtained. 24 kinds of monochromatic LED are used in the best combination of AM1.5 visible light fitting, and the correlation index R2 is as high as 0.850 2. 25 kinds of monochromatic LED are used in the best combination of standard light source CIE-D65 fitting, and the correlation index R2 is as high as 0.940 5. The optimization experiments of increasing and reducing LED numbers were carried out too. The results provide a theoretical basis for the study of monochromatic LED fitting solar spectrum in engineering practice.关键词：AM1.5;monochromatic LED;spectral fitting;optimum combination;correlation index173|210|4更新时间：2020-08-12
- 摘要：The citric acid was placed in monoethanolamine to achieve fast and large-scale synthesis of nitrogen doped fluorescent carbon dots by simple heating. When the NCDs are excited by 370 nm, there is a strong fluorescence emission at 458 nm, and the maximum absorption wavelength is 365.085 nm. DNA can enhance the fluorescence of the carbon quantum dots and has a related linear relationship. Thus, a hybrid nanocomposite(Nano probe) with nitrogen doped carbon dots and DNA was prepared. The method was first used to detect protamine. Under the optimum experimental conditions, the method is simple and selective. The linear detection range of this method is 1-10 μg·mL-1, and the detection limit is up to 0.61 μg·mL-1.关键词：N-doped carbon quantum dots;DNA;nanoparticle probes;protamine172|242|1更新时间：2020-08-12
- 摘要：The fluorescence pH sensing characteristics and applications of universal pH-indicator paper in the pH range of 2.2-12.5 were researched. In the experiment, pH-indicator paper strips were dipped into different pH buffer solutions first, then aired dry to be tested under light excitation. The fluorescence spectra were analyzed using peak shift and band barycenter shift. Experimental results indicate that the fluorescence of pH-indicator paper depends on the pH value of tested solution, and the dependence is repeatable. In the pH range of 4.0-9.0, the barycenter wavelength of the emission band is linearly dependent on pH value. As a consequence, pH sensing function of λB=603.8-4.09pH is obtained. When a pH value of 7 is set as a reference, the relative sensitivity is determined as 0.71%/pH. Resolution of the experimental setup is determined as 0.4. The applications on urea solution and tap-water verify the merit of the sensing method and the corresponding system. The research can offer an optoelectronic method and corresponding experimental system for remote pH sensing. Moreover, the fluorescence pH test is more precise than the strip color judgment with naked eyes, particularly for acidulous or alkalescent solutions.关键词：pH-indicator paper;emission spectrum;band shift;fluorescence sensing137|219|0更新时间：2020-08-12
- 摘要：Time advancement of fast light in small signal regime was derived from three wave coupling equations of stimulated Brillouin scattering(SBS) in photonic crystal fibers(PCFs), and the influence of air-filling ratio and doping(doped GeO2) on Brillouin frequency shift, time advancement, pulse broadening factor and pulse deformation were simulated by full vectorial finite element method. The results show that the Brillouin frequency shift decreases with the increase of air-filling ratio and doping mass fraction. The time advancement increases with the increase of air filling factor, but decreases with the increase of doping mass fraction at a given pump power of 20 mW and fiber length of 10 m. The varying trend of broadening factor is just contrary to that of the time advancement. The time advancement of 29.7 ns and the pulse broadening factor of 0.88 are achieved at the air filling factor of 0.8 and GeO2 doping mass fraction of 18%. The Brillouin threshold decreases with the increment of filling factor and decrement of doping mass fraction.关键词：stimulated Brillouin scattering;photonic crystal fiber;fast light;GeO2 doped136|225|0更新时间：2020-08-12
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