最新刊期
卷 32 ， 期 1 ， 2011
- 摘要：This work presents novel field emission organic light emitting diodes (FEOLEDs) with dynode, in which an organic EL light-emitting layer is used instead of an inorganic phosphor thin film in the field emission display (FED). The proposed FEOLEDs introduce field emission electrons into organic light emitting diodes (OLEDs), which exhibit a higher luminous efficiency than conventional OLED. The field emission electrons emitted from the carbon nanotubes (CNTs) cathode and to be amplified by impact the dynode in vacuum. These field emission electrons are injected into the multi-layer organic materials of OLED to increase the electron density. Additionally, the proposed FEOLED increase the luminance of OLED from 10 820 cd/m2 to 24 782 cd/m2 by raising the current density of OLED from an external electron source. The role of FEOLED is to add the quantity of electrons-holes pairs in OLED, which increase the exciton and further increase the luminous efficiency of OLED. Under the same operating current density, the FEOLED exhibits a higher luminous efficiency than that of OLED.关键词：field emission diodes;organic light emitting diodes;electrons113|66|0更新时间：2020-08-12
- 摘要：Ca4Y6Si6O25 ∶ Eu2+ green phosphor was prepared by high temperature solid-state reaction. The XRD speetrum indicates that Ca4Y6Si6O25 has a hexagonal crystal structure with a space group of P63/m(176). The excitation and emission spectra of Ca4Y6Si6O25 ∶ Eu2+ were measured when the mole fraction of Eu2+ was 20%. Its excitation spectrum is a broad band, from 350 nm to 450 nm, which matches with near ultraviolet LED chip. The emission spectrum of Ca4Y6Si6O25 ∶ Eu2+ exhibits an asymmetry broad band with the peak center at 527 nm, and it is because that Eu2+ takes the place of Ca2+ and forms two different luminescence centers. The effect of Eu2+ concentration on Ca4(1-x)Y6Si6O25 ∶ 4xEu2+ intensity was also investigated. With the increase of Eu2+ concentration, the luminescence intensity of the green phosphor get to maximum and then decrease. The optimal mole fraction of Eu2+ is 20%(x=0.05). According to Dexter theory, concentration quenching can be attributed to quadrupole-quadrupole interaction.关键词：luminescence;phosphor;Ca4Y6Si6O25 ∶ Eu2+;white LED109|67|1更新时间：2020-08-12
- 摘要：Ho3+ doped Ba0.8Sr0.2TiO3 (BST) thick films were fabricated on alumina substrates by the screen printing techniques. XRD patterns show that the lattice parameters of BST films have a maximum value when Ho3+ concentration is 1.0%. Under 514 nm Ar+ laser excitation, the emission peaks lacate at about 549,650 and 753 nm corresponding to (5F4,5S2)→5I8,5F5→5I8 and (5F4,5S2)→5I7 transition of Ho3+ ion. Under 800 nm laser excitation, blue and green up-conversion luminescence was observed. The blue and green up-conversion luminescence mechanisms were also discussed. The results show that the Ho3+ ∶ BST materials are prospective candidates for applications in new photoelectric devices.关键词：Ho3+;BST thick films;up-conversion luminescence102|46|2更新时间：2020-08-12
- 摘要：A series of Ce3+ and Eu2+ doped Ca8Mg(SiO4)4Cl2 powder were synthesized by high-temperature solid-state reaction. The crystal structure was investigated by X-ray diffraction (XRD) and the fluorescence spectra were also recorded and analyzed. The relative spectral power distribution was obtained by spectral power calibration curve, and the emission color coordinates of samples were calculated and characterized. The XRD spectrum indicate that the phosphor is Ca8Mg(SiO4)4Cl2 with face centered cubic lattice. Ce3+ and Eu2+ doped Ca8Mg(SiO4)4Cl2 samples present purplish-blue and green colors under the excitation of ultraviolet radiation, and the corresponding color coordinates are (0.157 3, 0.052 8) and (0.154 0, 0.466 3),respectively. In Ce3+/Eu2+ codoped Ca8Mg(SiO4)4Cl2 powder, the introduction of Ce3+ changes the luminescent color obviously, and with the increasing of concentration Ce3+, the color coordinates shift to the greenish blue color region.关键词：cerium and europium ions;calcium magnesium chlorosilicate;spectral power distribution;color coordinates107|90|2更新时间：2020-08-12
- 摘要：In this paper, nano-ZnO and Eu3+ doped nano-ZnO powders were prepared by ultrasonic atomization and co-precipitation method with Zn(NO3)2 and (NH4)2CO3 as reactants. The effects of the ultrasonic spraying condition, the reaction time and chemical composition on the morphology and size of ZnO nanopowder were carefully investigated. And the chemical processing condition of the zinc hydroxide dehydrated to ZnO nano-powder was analyzed. XRD, SEM and fluorescence spectrophotometer were employed to characterize the phase composition, particle size and luminescence property of the nano-powder. XRD results of the powder show a typical wurtzite hexagonal crystal structure. The photoluminescence spectra indicate that Eu3+ ions are successfully doped into the crystal lattice of ZnO matrix. The emission of the 5D0→7F2 comes from an allowed electric-dipole transition is the strongest. The SEM results show that the prepared spherical nanosized zinc oxide have narrow size distributions at 35~45 nm. The effect of ZnO content on the emission intensity was also investigated. The concentration quenching for the emission intensity did not occur when the doping concentration of Eu3+ up to 10%.关键词：nano-ZnO powder;ultrasonic atomization and co-precipitation method;luminescence property98|71|0更新时间：2020-08-12
- 摘要：The Hamiltonian of a quantum rod with an ellipsoidal boundary is given after a coordinate transformation which can transform the ellipsoidal boundary into spherical one. The properties of the strong-coupling impurity bound polaron in a quantum rod in a three-dimensional anisotropic harmonic potential are studied by using the linear combination operator and the unitary transformation methods. The relationships among the vibrational frequency, the mean number of phonons of strong-coupling impurity bound polaron in a quantum rod and the Coulomb bound potential, the electron-phonon coupling strength, the aspect ratio of the ellipsoid and the transverse and the longitudinal effective confinement length of quantum rods were derived. Numerical calculations are performed and the results show that the vibrational frequency and the mean number of phonons increase the electron-phonon coupling strength and the Coulomb bound potential, decrease with the transverse and the longitudinal effective confinement length of quantum rods and the aspect ratio of the ellipsoid. These can be attributed to the interesting quantum size confining effects.关键词：quantum rods;linear combination operator;impurity bound polaron95|78|1更新时间：2020-08-12
- 摘要：A new ternary complex of Eu3+ with bis(β-diketone) ligand 1,3-bis benzene and 1,10-phenanthroline was synthesized. The properties of this complex were characterized by IR ,UV-Visible spectrometry, elemental analysis and TG-DSC.The photoluminescence of complex indicated that there is a sharp and strong red emission peak at 612 nm attributed to 5D0→7F2 transition of Eu3+ ion. The results showed that this Eu3+-bis(β-diketone) complex would be a potential excellent red emission material.关键词：bis(β-diketone);rare earth europium;complex;luminescent property185|29|3更新时间：2020-08-12
- 摘要：The SrIn2O4 ∶ Sm3+ red emission phosphor were synthesized by combustion method and their luminescence properties were studied. The SrIn2O4 ∶ Sm3+ shows three major emission peaks at 568,606,660 nm, which correspond to the 4G5/2→6H5/2,4G5/2→6H7/2 and 4G5/2→6H9/2 typical transition of Sm3+ ,respectively. The strongest emission peak is at 606 nm. Their excitation spectra containing two bands whose peaks located at 413,476 nm indicating that this phosphor can be excited effectively in both near-ultraviolet light-emitting diode (UVLED) and blue light-emitting diode for white LED. The influence of the concentration of Sm3+ was investigated also. The SrIn2O4 ∶ Sm3+ phosphor is a very appropriate red-emitting phosphor for white light-emitting diode device.关键词：LED;phosphor;Sm3+;SrIn2O4154|82|7更新时间：2020-08-12
- 摘要：This paper reports a high performances Fe3O4 doped organic light emitting devices (OLEDs). The tris-(8-hydroxyquinoline) aluminum (Alq3)-based OLEDs with Fe3O4 doped N,N '-diphenyl - N,N'-bis (1,1'-biphenyl)-4,4'-diamine (NPB) exhibit a very low turn-on voltage of 2.5 V, and a high luminance of 30 590 cd/m2,while the turn-on voltage is 5 V and the luminance is 1 680 cd/m2 at 10 V for the undoped one. The power efficiency is increased from 1.2 lm/W to 2.0 lm/W at the current density of 20 mA/cm2 by inserting the Fe3O4-doped NPB layer. The Fe3O4 doping effects on the OLEDs are further clarified by analyzing the results of ultraviolet/visible/near-infrared absorption spectra and the characteristics on the hole-only devices. The improvements in device performances are attributed to the improved hole transport and conducti-vity through the formation of the charge transfer complex between Fe3O4 and NPB. Results on the UV photo-electron spectroscopy studies reveal that the hole-injection barrier from ITO to NPB is reduced by 0.37 eV by introducing the doped layer NPB ∶ Fe3O4. This enhances the hole injection and decreases the driving voltage, resulting a higher power efficiency. Therefore, the power consumption is lowered, and that good for prolonging the lifetime.关键词：organic light-emitting devices;Fe3O4;p-dopant89|92|1更新时间：2020-08-12
- 摘要：In this paper, dramatic improvements in vertical cavity surface emitting laser (VCSEL) perfor-mance have been obtained due to the advanced fabrication techniques and electrical confinement, as well as the structural design and growth of Bragg mirrors. A numerical simulation of current density distribution in the active of a large aperture single device and an array element were constructed. It is found that the current density at the perimeter of the oxide aperture is higher than at the center of the active region. The highe order transverse modes were excited due to the current crowding at the perimeter of the oxide aperture, which lea-ding to large divergence angle. And it is suppressed by optimizing the p-contact diameter in a single device and suppressed by using an extra Au layer. The far-field angle of a single device with a 600 μm oxide aperture decreased from 30°to 15° when the p-contact diameter is optimized from 650 μm to 580 μm, and there is a slight increase in output power due to the optimization. By using an extra Au layer, the output aperture of a 4×4 two dimension array element is decreased to 180 μm, and the far-field angle of the array device is suppressed to 10°. There is a slight drop in output power due to the introduction of the extra Au layer.关键词：lasers;vertical-cavity surface-emitting laser;far-field divergence angle111|157|2更新时间：2020-08-12
- 摘要：The 970 nm reflection-mode vertical cavity semiconductor optical amplifiers (VCSOA) were designed and fabricated. Based on the structure of VCSOA, the amplifier noise, gain and bandwidth characteristics were experimentally investigated and analyzed in the reflection mode. For a signal light of 970 nm, the maximum of gain amplification can reach to 26 dB after VCSOA. The bandwidth is 25 GHz when the gain is 26 dB. The noise factor is 6.6 when the bottom and top reflectivity is 0.99 and 0.98, respectively.关键词：vertical cavity semiconductor lasers;semiconductor optical amplifier;gain;bandwidth126|110|0更新时间：2020-08-12
- 摘要：The piecewise linear current density recursive convolution finite-different time-domain method is applied to study the filtering properties of one dimension tunable unmagnetized plasma photonic crystals with single defect layer. In frequency domain, the transmission coefficients of electromagnetic differential Gaussian pulses are computed, and under the isothermal hypothesis, the plasma relaxation time, plasma temperature and plasma frequency are taken as the tunable parameters to study the effects of filtering properties. The results are as follows: the filter channel can be tuned by changing relaxation time and frequency of plasma,while the resonant frequency can not be tuned by changing plasma temperature.关键词：photonic crystals;plasma;tunable filter;finite-different time-domain method107|102|1更新时间：2020-08-12
- 摘要：A LED-based illumination system with unique feature of instant color variability was fabricated after analyzing the working principle and designing the optical structure of the system. The driving circuits realized constant-current drive and PWM dimming by using IC MAX16807. The experimental results show that the irradiance, the dominant wavelength and the chromaticity coordinate are stable; the uniformity of irradiance distribution is above 90%. Finally, a good image result was obtained and this illumination system was proved to be suitable for color vision measurement.关键词：color vision measurement;light source;optical design;LED drive107|108|0更新时间：2020-08-12
- 摘要：Electromagnetically induced transparency (EIT) with extremely narrow spectral width is obtained in a well-studied lambda three level system where a coupling field and a probing field interact with two optical transitions. By tuning coupling field, it excites the transitions between two ground state hyperfine levels and excited state level. In this paper, both EIT and spontaneous radiation induced coherent dip can be obtained, and even the gain is observed to superpose to the EIT window. By discussing the behaviors of probing field absorption profiles under the effect of the tuned coupling field, it can be seen that there are quantum interference and coherence between EIT and spontaneous radiation induced coherent dip, and the coherence becomes remarkable when the excitation frequency of the coupling field satisfies certain conditions.关键词：electromagnetically induced transparency (EIT);gain;spontaneous radiation induced coherent dip;tuned coupling field105|104|0更新时间：2020-08-12
- 摘要：This article demonstrates the EVA film encapsulant effect in PV(Photovaltaic) modules and the test method of EVA film cross-linking degree. Through testing EVA film cross-linking degree, we optimizes PV modules laminated time, temperature and other factors in order to maximize PV modules conversion efficiency and ensure much longer lifetime. To test different positions EVA film cross-linking degree, the laminate machines surface work temperature in different region was detected. It ensures the passing rate of PV modules.关键词：solar module;laminating machine;EVA film;cross-linking degree135|150|0更新时间：2020-08-12
- 摘要：Nano-amorphous carbon films were synthesized on Si substrates by microwave plasma enhanced chemical vapor deposition (MPECVD). Through Raman, SEM, XRD characterization, the effects of catalyst FeCl3 on the growth rate and the field emission properties of nano-amorphous carbon films were discussed. The experimental results show that the catalyst FeCl3 can increase the growth rate of the nano-amorphous carbon films greatly. Compared with the nano-amorphous carbon films without catalyst in the same preparation conditions,the threshold field of the carbon films using catalyst is very low(about 0.5 V·μm-1 ),the current density of 2.6 mA·cm-2 can be obtained at an electric field of 1.8 V·μm-1 and the emission sites density are greater, and with homogeneous distribution.关键词：nano-amorphous carbon films;catalyst;field emission109|140|0更新时间：2020-08-12
- 摘要：Double-exponential model of ultraweak photon emission of soybean callus was proposed based on the mechanism of ultraweak photon emission in biological system. Treated soybean callus by UV-B radiation(20 μW/cm2 )for 2 h,ultraweak photon emission of soybean callus treated by UV-B for 4 d after was measured. The results show that double-exponential model accurately describes the characteristics of ultraweak photon emission of soybean callus and its changes, delayed luminescence of ultraweak photon emission of soybean callus is composed by both fast and slow phase. Spontaneous luminescence in ultraweak photon emission of soybean callus and some parameters of delayed luminescence such as initial photon number I(0), integrated intensity I(T) and decay parameters of delayed luminescence are obtained through analysis of the double-exponential model, the characteristics of ultraweak photon emission of soybean callus can be quantitative expressed by these parameters. The studies also find that there is an excellent positive correlation between initial photon number I(0) and integrated intensity I(T),and I(0) or I(T) can be used to measure the metabolic intensity of soybean callus. Induced by UV-B radiation(20 μW/cm2 ) for 2 h,the decay parameter of fast phase in delayed luminescence decreases first and then increases, the change of spontaneous luminescence is opposite, it suggests that fast phase of delayed luminescence is sensitive to the UV-B radiation and membrane lipid peroxidation could be the reason of the drastic change of fast phase in delayed luminescence of soybean callus.关键词：ultraweak photon emission;double-exponential model;soybean callus;UV-B radiation98|82|3更新时间：2020-08-12
- 摘要：In order to obtain the relationship between temperature-stress and delayed fluorescence (DF) emission spectra, in this paper, three different heat-resistant maizes were used as samples to experimentally study the plant DF emission DF spectra at different elevated temperatures (10~50 ℃). The experimental spectra were obtained by 660 nm excitation. Results showed that there are two distinct emission peaks in DF spectra, that is, the main peak at around 685 nm and the second peak at around 730 nm. The maximal values of DF emission spectra at 685 nm and 730 nm were marked as F685 and F730, respectively. The experimental results illustrated that the F685/F730 ratio varied with the increase of temperature. It was also found that the F685/F730 ratio at 10 ℃and 50 ℃, which was marked as V10 and V50, respectively, are obviously different. The V10/V50 ratio depended on the heat-resisting property of the samples. These results indicated that the higher the heat-resisting property of the sample is, the lower the V10/V50 ratio is. Additionally, the longer temperature stress time is, the lower V10/V50 ratio is. Hence, we concluded that DF emission spectra vary with the temperature-stress, and the response curve of F685/F730 ratios of different samples display a similar law. Moreover, the responses of F685/F730 ratio of DF emission spectra to the temperature for the different heat-resistant Maize samples could be a new and useful judgment to identify and evaluate the heat-resisting property of maize.关键词：delayed fluorescence;delayed fluorescence spectra;temperature stress;F685/F730;heat tolerance property94|51|0更新时间：2020-08-12
- 摘要：Ponceau S (PS) can quench the fluorescence of bovine serum albumin (BSA) in the aqueous solution of pH=7.40. The static fluorescence quenching process between BSA and PS was confirmed and the binding constant, the number of binding sites and thermodynamic parameters between BSA and PS were obtained. It showed that the number of binding sites was 1 and the electrostatic attraction played an important role in the binding of BSA to PS. Based on the theory of Frester energy transfer, the binding distance (r＜7.0 nm) between PS and BSA was obtained. Studies utilizing synchronous spectra showed that the conjugation reaction between PS and BSA would affect the conformation of BSA, leading to the weak polarity around tyrosine residues and the strong hydrophobicity. The site markers competitive experiments indicated that the binding of PS to BSA primarily took place in sub-domain ⅡA (site Ⅰ).关键词：bovine serum albumin;ponceau S;conjugation reaction;binding site;spectroscopic probe89|75|0更新时间：2020-08-12
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