最新刊期
卷 26 ， 期 2 ， 2005
- 摘要：Defects can be produced in the matrix by aliovalent ionic substitution or by high-energy radiation. Electrons or holes can be trapped by these defects. Light will emit by radiative recombination of these electrons and holes released from traps with different depth. Some important luminescence materials doped with rare earth ion Eu2+ or Mn2+ such as long-lasting phosphorescence and solid dosimeters are based on this electron trapping process. Recently, we synthesized some electron trapping materials for long-lasting phosphors use. We prepared some glasses possessed of long-persistent phosphorescence and information storage properties. For example, ZnO-SiO2-B2O3:Mn2+ glass shows red long afterglow. It is interesting to note that photo-stimulate long-persistent phosphorescence phenomenon is observed, information can be written and storages in the glass with 254nm UV light and read out by visible or IR light. Depending on different annealing temperatures, this glass can transform into glass ceramics emitting yellow or green long-lasting phosphorescence light. We synthesized also the yellow phosphor CaGa2S4:Eu2+,Ho3+ and red phosphor CaS:Eu2+,Tm3+with long-persistent phosphorescence properties. For improving the stability of the latter phosphor, we studied the oxide coating. We studied also the solid dosimetric property of some borates doped with Dy3+ or Tb3+ such as Sr0.93Dy0.07B4O7 or Zn0.96(BO2)2:0.04Tb. After aliovalent ionic substitution and β-ray or γ-ray radiation, defects and traps are formed. The respond of the thermoluminescence intensity with the dose is linear, it may be used as detector for radio-diagnosis.关键词：rare earth;electron trapping material;defect148|135|5更新时间：2020-08-11
- 摘要：Three kinds of white organic light emitting devices (WOLED) were constructed:Cell-S, with a single-doped red dye in the light emitting layer(EML); Cell-D, with both red and blue dyes doped in a single EML(double-doped); Cell-T, with red and blue dyes doped in one EML and a green dye in another layer(triple-doped).The structure of these devices are as follows:Cell-S:CuPc(12nm)/NPB(40nm)/ADN:DCJTB(50nm)/Alq3(12nm)/LiF(4nm)/Al; Cell-D:CuPc(12nm)/NPB(40nm)/ADN:DCJTB:TBPe(50nm)/Alq3(12nm)/LiF(4nm)/Al; Cell-T:CuPc(12nm)/NPB(40nm)/ADN:DCJTB:TBPe(50nm)/Alq3:C545(12nm)/LiF(4nm)/Al. Experimentals indicate that the Cell-T and Cell-D show much higher luminance and efficiency than that of Cell-S.The Cell-T achieves a current efficiency of 6cd/A and a power efficiency 3.11 lm/W, which is twice that of Cell-S, 1026cd/m2 at driving current 20mA/cm2 and maximum luminance 21200cd/m2, In addition, it exhibits a flatcd/Avs. current density response, indicating a weak current induced fluorescence quenching. At the driving current 12mA/cm2, at the initial luminance of 575cd/m2, the half life is over 3862h for Cell-T, for an initial luminance of 100cd/m2, the half life (t/2) is projected to be 22245h with a little change of EL spectrum before and after aging.关键词：OELD;white emitting device;stability111|82|1更新时间：2020-08-11
- 摘要：Various external factors can influence on the energy-band structure of a solid, the changes of the energy-band structure will result in many novel physical phenomena, which has made people explore many new applied fields and attracted considerable attention in the last several decades. In the middle of the 70's of the 20th century, the influences of pressure on the absorption band edge of the semiconductor GaAs have been observed in the experiment. In the early period, some theoretical methods have been developed to investigate dependence of the direct energy gap of GaAs on hydrostatic pressure and optical properties of semiconductors under pressure. Although these theoretical methods have achieved some successes, yet they belong basically to the semi-experience phenomenology and the semi-classical theory. Recently, by using self-consistent pseudopotential method based on density-functional theory, XIAO Qi, etal. have investigated the electronic structure of iron pyrite FeS2 under external pressure, it was shown that the forbidden-band width become wider with increase of external pressure. However, the work studying the influence of external pressure on the energy-band structure by using energy-band theory of quantum mechanics is little still. The aim in the paper is to study the influences of pressure on the energy-band structure of a solid by using the tight-binding theory. We have calculated the 1s and 2s energy bands of a body-centered cubic lattice, and discussed the influences of pressure on the energy-band structure. The results show that the pressure makes lattice constant change, which results in the changes of the 1s and 2s energy-band width and the forbidden-band width between two energy bands for the body-centered cubic lattice. From our results, we have calcu-lated concretely the influences of pressure on the energy-band structure of the Li metal, with the increase of the pressure, the 1s and 2s energy-band width of Li metal will widen, the forbidden-band width between the two energy bands will narrow. Compared with the published data, our results are agreement with the experiment results in order of magnitude. In summary, by using the tight-binding theory we have investigated the influence of pressure on the energy-band structure of a solid. We can describe the energy-band width and the forbidden-band width as a function of the distance between neighbour atoms, when the pressure increase, the distance between neighbour atoms will decrease and make the energy-band structure of a solid change, which makes people understand easily the physical essence of the influence of pressure on the energy-band structure of a solid, it is obvious that the tight-binding theory has remarkable advantages in studying the influence of pressure on the energy-band structure of a solid.关键词：external pressure;energy-band width;forbidden-band width115|86|0更新时间：2020-08-11
- 摘要：Because nanometer materials is smaller, they possess rich scientific meaning and quantum effect. Base on quantum effect of these materials,develop a series new materials on photoelectron, photon and related quantum parts, bring about new trend on study and development of materials science. Quantum dot is very special because it's confined in three-dimension, quantum effect is more obvious, and become a new study realm. The structures of quantum dots were studied by perturbation method, varational method, and a few bodies method, base on effective mass approximation. E. Peter et al. report on the observation of asymmetric phonon sidebands on both the exciton and biexciton emission lines in single GaAs monolayer fluctuation quantum dot, and indicate that the contribution of phonon sidebands to the emission line is larger for the biexciton than for the exciton. R. P. Wang et al. studied Raman spectra of InO power and free-standing nanowires prepared by ablation. They found that the coupling strength determined by the ratio of second-to first-order Raman scattering cross sections diminishes with decreasing nanowire diameter, and the Frohlich interaction plays the main role in electron-phonon coupling in InO. J. L. Chen et al. studied the spin-relaxation time due to the electron-acoustic phonon scattering in GaAs quantum dots by exact diagonalized the electron Hamiltonian with the spin-orbit coupling, and discussed different effects such as the magnetic field, the quantum dot size, and the temperature on the spin-relaxation time.In this paper, the properties of polaron with electron-LO-phonon weak-coupling in cylindrical quantum dot, which was in quantum well and parabolic potential, were investi-gated by using the linear combination operator and unitary transformation methods. The results indicated that the renormalization mass of polaron in quantum dot decrease with increasing cylinder height, and increase with increasing coupling strength because of interaction between electron and crystal vibration. Ground state energy has something to do with size of quantum dot, characteristic frequency, coupling strength, and magnetic-field strength etc., it increased with decreasing cylinder height and increasing characteristic frequency, magnetic-field strength.关键词：quantum dot;polaron;renormalization mass117|74|0更新时间：2020-08-11
- 摘要：The planar channelling radiation for the super-relativistic electron is discribed by the classical electron-dynamical method; the spectral distribution and the maximum radiation energy are derived in classical mechanic frame. ch-2x potential described to a interaction of particle with the crystal is introduced. As example, the channelling radiation for a electron in the Si(110) planar channel is calculated.It shows that the maximum radiation energy may be represented as ε=ω=57lMeV for a l-order harmonics, the result is consistent with other work. A direction level of the channelling radiation is very well, and the greater part of the energy concentrate in a reqgion with angle width of Δθ≈γ-1/2 alone the motion direction of an electron,but also the radiation energy is very high.As example,the channelling radiation energy for 1-st order harmonic is ε=57.0MeV for a electron with energy 5.0GeV. Obviously, this energy is located in a γ-region, thus it is possible to take the channeling radiation as a new X-laser or γ-laser. In addition,the polarization level of the channeling radiation is very well also. Of course, take an attempt to reform the channelling radiation as a new type of X-laser and γ-laser require great efforts. It is expected that the coherence of the channelling radiation may be obtained by using a interaction between the channelling radiation and the superlattice with a multi-layer film construction.关键词：superrelativistics;channeling radiation;electron106|61|0更新时间：2020-08-11
- 摘要：A charged particle moving along the direction of the low crystal face index can penetrates through the crystal as easily as it does through a channel. This phenomenon is so-called channeling effect. The classical physics points out that an accelerated charged particle radiates energy continuously when moving in an electromagnetic field. The analogous situation occurs in crystal channel. When a charged particle moves in an accelerated way through a lattice field, the radiation energy can be produced. It is such an extremely strong lattice field that results in the rather higher radiation energy. For a positron with the energy of 10MeV, the radiation energy can reach keV in order of magnitude. The motion behavior of the channeling particle is governed by the interaction potential between the particle and the crystal. The potential, which we generally use, is Lindhard potential, Moliere potential, and sine-squared potential. Because the motion behavior of the channeling particle is most similar with that of a free electron moving in a Wiggler, it is expected that the channeling radiation can be changed as X-laser or γ-laser to pretend new high energy laser source. In 4th-order Lindhard potential approximation, the particle motion equation can be reduced to a second order nonlinear differential equation with a cubic term under the frame of the classical mechanics. By employing both the Jaco-bian ell iptic function and the first kind complete elliptic integral, the solution of the equation is derived and the channeling radiation frequency is obtained in an analytical expression. Besides, the instantaneous radiation intensity, the average radiation intensity and the maximum radiation frequency of positrons are also obtained. As an application of channeling radiation of positrons, the average intensity and the maximum frequency of single crystal silicon are calculated. The results indicate that it is possible to make channeling radiation as γ-laser.关键词：channeling radiation;nonlinearity;interaction potential120|84|0更新时间：2020-08-11
- 摘要：Photonic crystals are artificially fabricated periodic dielectric structures. The periodic dielectric structures exist photonic band gap. The photonic band gap depends on the symmetry of photonic crystals, the refractive index of constituents and the size of unit cell. Conventional photonic crystals are usually constructed by positive refraction materials. In recent years, a complex artificial materials with negative permittivity and negative permeability have attracted much attention theoretically and experimentally. According to the definition, the refractive index is also negative for such materials. In this paper, we consider a new kind of photonic crystals with alternative layers of negative refraction materials and positive refraction materials. Many unique features of light propagation are expected in this structure. By using the condition that the tangential components of electromagnetic field and its first derivative are continuous across the interface, we can get the transfer matrix which connects the fields between the incident end and the exit end. Using the transfer matrix, the transmission coefficient of the monochromatic plane wave can be expressed in terms of its matrix elements. By means of transfer matrix method, the numerical simulation and analyses for the properties of light propagation in one-dimensional photonic crystals with alternative layers of negative refraction materials and positive refraction materials have been made in this paper. The transmittance and dispersion relations of one-dimensional photonic crystals containing negative refraction materials were calculated. It's shown that, on normal incidence, the photonic crystals containing negative refraction materials have wider photonic band gaps which is different from the case of traditional photonic crystals with narrow transmission bands. Based on dispersion relationship, these phenomena were explained. Besides these, the relation between the reflectance and incident angles of different polarization modes when light incident with central wavelength was discussed. It's found that one-dimensional photonic crystals containing negative refraction materials have better angular properties than that of traditional photonic crystals and exhibit an omnidirectional reflection for the incident light with central wavelength.关键词：photonic crystals;negative refraction materials;transfer matrix method114|55|2更新时间：2020-08-11
- 摘要：Absorption is the underlying reason for the change of luminescence traits. And the lifetime influences on the absorption in turn. That is a common law, it is not only suitable for photoluminescence, but also other types of luminescence. In field of electroluminescence, there are two kinds of luminescence center blue have dramatically dissimilar lifetime, in the co-doped ZnS:Cu, Mn material. The experiment clearly demonstrates that the ratio of luminance of Cu and Mn change with the driving frequency. This law is also fit for the change of luminance in Cu, which has blue and green luminescent centers. The experiment proves that this law has something to do with lifetime and nothing to do with the way of exciting and the reasons is abruptly quenching. No matter what quenching is, the lifetime of centers must be shortened, for shorter lifetimes centers the inten-sity increases with the increase of driving frequency more quickly. The luminescence of singlet and triplet states in organic electroluminescence is crucial in determining the overall efficiencies. The density of states in singlet and triplet levels is 1:3. The transition from triplet state to singlet state is generally forbidden. People considered that the luminescence efficiency is limited to 1/4. But they ignored that their lifetimes are quite different, and this situation influences on the efficiency of luminescence. So the efficiency of luminescence in organic electroluminescence may be greater than 25%. The experiment also demonstrates the correctness of relationship between the differential cross-section and lifetime which was brought forward in thin film electroluminescence. In the case of thin film electroluminescence the differential cross-section of excitation is inversely proportional to the lifetime center. This result provides the basis of fabricating color tunable display panel using a single phosphor material. The rate of absorption of luminescent materials is controllable by luminescence lifetime, and the effect influences on the brightness and apparent efficiency of luminescence.关键词：lifetime of luminescence center;co-doping;electroluminescence161|167|2更新时间：2020-08-11
- 摘要：We have investigated the synthesis, luminescence and time-resolved fluorescence decay spectra for Zn2GeO4:xMn phosphors doped with different contents of Mn2+ as an activator. The microstructure of Zn2GeO4:xMn samples is highly dependent on synthetic conditions. The observed red shift in λem from 527nm to 534nm with increasing Mn2+ content has been investigated and rationalized by the presence of a weak crystal field due to the substitution of Zn2+ by Mn2+, which leads to a distorted tetrahedral lattice site. The CIE chromaticity coordinates were found to shift slightly with variation of doped Mn2+ content. Time-resolved fluorescence decay curves of Zn2GeO4:xMn have also been investigated. Interestingly, the shortening of fluorescence decay lifetime observed in Zn2GeO4:xMn phosphors with increasing Mn2+ dopant concentration has been rationalized by the alteration of transition probability as a consequence of magnetic interaction between Mn2+-Mn2+ pairs in the host lattice.关键词：Zn2GeO4：xMn phosphors;time-resolved fluorescence decay;photoluminescence spectra;color chromaticity126|67|0更新时间：2020-08-11
- 摘要：As an important Ⅱ-Ⅵ group material, ZnS nanoparticles have attracted more interest in its novel photoelectric properties, such as its wide bandgap and high luminescent efficiency. And in the last years scholars have composed all kinds of light-emitting ZnS based nano-phosphor powder. Recently the white-light emitting EL devices are mainly made by two methods. One type of device is structured by red-light, green-light and blue-light emitting diodes. The other type is achieved by transforming two or three kinds of colors coming from different fluorescent powders. But there lacks a type of ZnS based nano-phosphor powder which emitting white-light all by itself. The white-light emitting ZnS based nanoparticles have been prepared by doping the Mn2+ directly into the ZnS nanoparticles, which suggests a simple and easy operation. In the operation we mainly controlled two factors. One is the reactive temperature, and the other is the doping ration of the Mn2+ in the ZnS nanoparticles. The prepared particles are as small as 7nm in diameter with consistent crystal structure and mono-dispersivity and capped or modified by methacrylic polymer. The photoluminescence (PL) spectra of the ZnS:Mn nanopowder exhibit two emission peaks under excitation of 380nm, one is at 480nm with an blue-light emitting coming from the ZnS base and the other is at 590nm with a yellow-light emitting coming from the Mn2+ dopant. In general, the two violent emitting come into being an white-light emitting. It is worthy to give a careful discussion about the doping ration of the Mn2+ in the ZnS nanoparticles because only the optimum dose can make the ZnS:Mn nanopowder to exhibit white-light emitting. X-ray diffraction (XRD) demonstrated that the ZnS:Mn nanoparticles have zinc blend crystal structure and Scherrer formulation was applied to estimate the diameter of the ZnS:Mn nanoparticles,which is about 7~8nm. In its UV-vis spectra, there is a blue shift of the absorption peak due to the modified surface and small size effect of the ZnS:Mn nanoparticles. According to the blue shift, Brus formulation was applied to estimate the diameter of the nanoparticles, which is consistent with the result obtained from the Scherrer formulation. The IR patterns of the ZnS:Mn nanoparticles and the one of the methacrylic acid have much comparability indicating that methacrylic polymer has capped or modified the ZnS:Mn nanoparticles.关键词：nano ZnS:Mn particle;white-light emitting;doping ration of Mn103|66|2更新时间：2020-08-11
- 摘要：Combustion synthesis technology overcame the disadvantages of high temperature solid-state reaction, and resolved the serious pollution of sulfur for the environment, what's more, phosphor powders of the small particle size were achieved, which could enhance the resolution of imaging system to some extent. X-ray phosphor powders of Ln2O2S:RE3+ (where Ln=La,Gd; RE=Eu,Tb)were prepared by combustion reactions. In detail, different kinds of rare earth nitrates were weighed and mixed in stoichiometric amounts, where the doses of the dopant were 0.15%, 0.35% and 0.5% in mol fraction, respectively. The nitrates were molten during drying in an oven at 100℃, and during the cooling of these mixed nitrates reactants, appropriate amounts of organic fuel, such as dithio-oxamide were added, mixed and ground along with the nitrates, where molar ratio of dithiooxamide to the rare earth nitrates was 2. The mixtures were heated in an air tube furnace with the ignition temperature of 300~350℃. To evaluate the effects of heat treatment, the combustion-prepared powders were also heated to 500~700℃ in air. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), photoluminescence(PL) and X-ray excited luminescence (XEL). XRD results showed the oxide sulfide phases only when the sintering temperatures were lower than 500℃, which avoided the defect of high sintering temperature. SEM results showed a loose, porous agglomeration and a continuous three-dimensional network, and the primary particlesize is not more than 50nm. PL spectra showed the characteristic emission of rare earth activation ions, respectively. To our satisfaction, the PL intensities were nearly the same as some commercial X-ray phosphors. XEL spectra showed the same characteristic emission, although their luminescence principals were different each other. In addition, the absorption coefficients and the dopant concentration doped of these samples weren't the same for X-ray excitation, therefore, their light emission efficiencies were also different.关键词：combustion synthesis;X-ray phosphor powders;X-ray excited;characteristic emission112|33|5更新时间：2020-08-11
- 摘要：Recently, borophosphate has attracted much attention during the continuous searching for new functional materials. We report the synthesis process, structural and spectroscopic properties of Ce3+ doped alkali-earth borophosphate. MBPO5 (M=Ca, Sr, Ba) were prepared by solid-state reactions and Ce3+ ions were successfully doped into the samples in a reduction atmosphere. The structural properties were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). XRD patterns exhibit that the samples crystallize in stillwellite structure. FT-IR spectra show the absorption bands of BO 4 and PO 4 groups, indicating that B and P atoms were linked with O atoms in regular tetrahedron form. The excitation spectra in the vacuum ultraviolet-ultraviolet region of the samples were recorded. The emission spectra feature typical 5d→4f transition of Ce3+. The effects of radius of alkali earth ions on the excitation spectra and emission spectra were discussed. The lifetime of Ce3+ emission in BaBPO5 is measured to be about 25ns, which meet the demand of scintillator for the short lifetime. Our results show that Ce3+ doped MBPO5 (M=Ca,Sr, Ba) may find potential applications in scintillator materials.关键词：scintillators;borophosphate;Ce3+112|60|6更新时间：2020-08-11
- 摘要：Much attention has been paid to search for high-efficient phosphor since the plasma display panels (PDP) edged competitively in the market of large flat panel display. The commercial PDP blue phosphor BaMgAl10O17:Eu2+ suffers from decreasing performance of brightness and color because of the serious processing thermal degradation and timing deterioration. New blue phosphor with stable activation ion may be a better way to solve this problem. In the lanthanide series, Tm3+ may be a feasible candidate for the blue emissions originating from 1D2→3H4 (around 450nm), 1G4→3H6 (around 480nm) transitions. Conventionally, the phosphor production is prepared using solid-state reactions between oxide sources at high temperature. However, it is difficult to control over particles size and morphology, uniform dopant concentration. On the contrary to conventional methods, aerosol synthesis technique has been employed successfully to prepared phosphor particles with good morphology in recent years. By coprecipitation reaction, high quality Y(P,V)O4:Tm3+ phosphor was prepared. The phosphor was characterized by XRD, SEM, and photoluminescence under VUV (147nm) or UV (254nm) excitation. The XRD patterns disclosed that the obtained Y(P,V)O4:Tm3+ is not a mixture, but a compound. The SEM image showed that the size of the phosphor particles is uniform and submicron, and the morphology is regular and no agglomeration. Under VUV and UV excitation, there are two emission peaks for most phosphors observed, the narrow one at 475nm originates from the Tm3+ ion transition 1G4→3H6, and the weak broad-band around 430nm belongs to VO43-group. With increasing Tm3+ concentration, the narrow peak intensity enhanced while the Tm3+ concentration is lower than 0.005 in mole. When the Tm3+ concentration is higher than 0.005, the intensity of the transition 1G4→3H6 decreases with increasing Tm3+ concentration. The intensity of broad-band de-creases with Tm3+ concentration in full studied concentration region. It is expected that Y(P,V)O4:Tm3+ would be a promising candidate for PDP phosphors.关键词：coprecipitation;Y(P;V)O4：Tm3+;phosphor;photoluminescence108|109|3更新时间：2020-08-11
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Phenomenon and Mechanism of Long Afterglow Phosphors in Trivalent Rare Earth Ions Doped Cd3Al2Ge3O12
摘要：Though the long afterglow phosphors have been improved greatly since its invention in the nineteenth century, the mechanism of the occurrence of long afterglow is still unknown clearly. In this work, trivalent rare earth ions activated garnet-typed cadmium aluminium germanate Cd3Al2Ge3O12:Ln phosphors were studied to discover the relation between the ion electronegativity and afterglow performance. All samples were synthesized by a traditional solid-state reaction method. The luminescent properties were investigated. Long afterglow were observed excitation by 254nm light for all of the samples. The rare earth ions can be divided into three kinds based on their long afterglow performance. The first one is Pr3+,Tb3+ and Dy3+. Characteristic emissions with afterglow were generated after excitation by 254nm light. The second one is Eu3+ and Sm3+. These ions can produce characteristic emission with excitation by 254nm light, but without afterglow. The third one is Ce3+,La3+,Nd3+ and other rare earth ions. These ions can not produce characteristic emission, and have no distinctly influence on the afterglow performance of the host. By comparing their electronegativity, we found that the electronegativity was consistent with the afterglow performance. Basing on the phenomena mentioned above, we concluded that the afterglow performance of reductive ions was better than that of oxidative ions in this host. The mechanism of the long afterglow may be depicted as two steps. For example of Pr3+, at first, Pr3+ electrons are excited to the conduction band and are trapped at the electron traps. This process leaves Pr4+ ions in the sample. Then the electrons at the electron traps escape from the electron traps and are captured by Pr4+ ions to produce Pr3+ ions in excited stated. The excited state Pr3+ ions emit photons and return to ground state. The Pr3+,Tb3+ and Dy3+ can be photoionizated to quadrivalent ions easily. It's very difficult for Eu3+ or Sm3+ to be photoionizated to quadrivalent ions, so afterglow can't be observed in the Eu3+ or Sm3+ doped samples.关键词：afterglow;Cd3Al2Ge3O12;thermoluminescence117|87|1更新时间：2020-08-11 - 摘要：Recently, much attention has been focus on the investigation of the electroabsorption in the GaAs/AlGaAs quantum wells (QW's) because of its possibility of designing new types of electro-optic modulators. Much optical properties of the single QW's with different potential has been and being investigated experimently and theoriticaly with different methods. In these few years, the double quantum wells (DQWs) became the focus of the research. In this paper, by using the density matrix formalism and iterated method, the first-and the third-order intersubband optical absorption of double quantum well with infinit boundary was investigated theoretically. Thereafter, a typical GaAs/AlGaAs DQWs is presented to get the results. The results show that the peak absorption varies with the width of the intermediate potential barrier. And it also shows that the absorption decrease as the incident optical intensity increasing.关键词：double quantum wells;optical absorption coefficient114|91|0更新时间：2020-08-11
- 摘要：Europium-doped nanocrystalline ZrO2:Eu3+ powders with different doped concentrations were prepared by chemical co-precipitation method, which is a useful and simple technique to dope Eu3+ ions into a host material. The sharp characteristic photoluminescence (PL) in visible region originating from the intra-4f transition of the Eu3+ ions and the energy transfer between the nanocrystalline ZrO2 host and the dopants were observed at room temperature. Luminescent properties of nanocrystalline ZrO2:Eu3+ with different sintering temperatures and doped concentrations were studied. At keeping the doped concentration unchanged, we found that the luminescent intensity of the sample with the sintering temperature 600℃ was greater than those of other samples. The luminescent intensity of the sample with the doped concentration 5% are relatively the greatest when other conditions were kept unchanged. Our results also show that the crystal phase is changed as the sintering temperature is increased. In addition, the charge transfer state of Eu3+ ions was also observed in this paper.关键词：nanocrystalline ZrO2：Eu3+;chemical co-precipitation;photoluminescence;doping;energy transfer99|115|5更新时间：2020-08-11
- 摘要：There are many viewpoints about green emission center in ZnO films, such as VO (donor) or OZn (acceptor). In order to control the emission spectra, it's important to find out green centers of ZnO films. ZnO films were grown on Si substrates by DC reaction sputtering. After growing the samples were heat treated in different temperatures and oxygen partial pressures. X-ray diffraction patterns indicate all films have ?0002〉 preferred orientation, but the film treated in 1000℃ in N2 ambience has a lattice constant larger than that of other samples and its lattice was larger distortion in lattice. We guess that a lot of interstitial zinc (Zni) was generated in the film, as a result of annealing in the ambience of lack of oxygen. Depth analysis of element contents by Auger electron spectroscopy (AES) indicates the distributions of Zn and O in ZnO films were different due to different annealing conditions. Photoluminescence spectra of all films show two emission peaks at 3.18eV (ultraviolet) and 2.38eV (green), except the Sample 1#(annealed in N2), which has a 3.18eV peak only. Comparing photoluminescence spectra of the films to the distributions of Zn and O by AES in the films, it was found that if O content exceeds that of Zn in any depth of film, the films generate green emission,and the green emission is stronger the more excess of O content. If O content exceeds Zn, the acceptors defects exceed donors in the monophase films. Therefore we suggest that green luminescence center is concerned in acceptor defects in ZnO grown on Si substrates by DC sputtering, the energy of green luminescence, 2.38eV, is centered OZn, comparing with energy band calculation.关键词：ZnO film;Auger electron spectrum;photoluminescence;Zn/O ratio112|80|6更新时间：2020-08-11
- 摘要：Raman scattering spectra of GaN and Mg-doped GaN films grown by metal-organic chemical-vapor deposition (MOCVD) on sapphire substrate are investigated. Some weak peaks are also observed in two spectra besides the allowed E2 and A1(LO) phonon modes in Z(X-)Z backscattering geometry. The origins of these peaks are discussed and the differences between two spectra are compared. Two peaks at 640 and 660cm-1 are observed both in the spectra of GaN and Mg-doped GaN samples. The 640cm-1 peak is attributed to an overtone process of the highest acoustic-phonon branch at the zone boundary (L point). The peak at 660cm-1 is attributed to the optical-phonon branch at the zone boundary or the local vibrational mode induced by defect. In the spectrum of Mg-doped GaN sample there is a broad feature near the two peaks. It is suggested that the broad feature arises from the local vibrational mode of Mg-N bond which superposed on the two peaks mentioned above or arises from defect-induced broaden. Two additional peaks at 276cm-1 and 376cm-1 are also observed in the spectrum of Mg-doped GaN sample. The peak at 276cm-1 is the local vibrational mode of Mg-N bond and the peak at 376cm-1 is the local vibrational mode of impurity-defect complex. The frequency of E2 mode in Mg-doped GaN shifted to low energy side compared with GaN sample, and located at 568cm-1 at room temperature. This indicated that the relaxation of residual stress existed in Mg-doped sample. The stress relaxation is contributed to Mg-induced generation of dislocation. Furthermore, electron-phonon interaction also can induce frequency shift of E2 mode.关键词：GaN;Raman scattering;stress relaxation112|105|0更新时间：2020-08-11
- 摘要：In recent years, the synthesis of nanomaterials have received extremely interests of physicists, chemists and materialists in both fundamental and applied studies. As one of synthesis method of nanomate-rials, the synthesis by template is specially important, for example, more and more materials were produced by porous anodic aluminum oxide. In our recent work, wide range porous anodic aluminum oxide (AAO) film with highly ordered nanopore arrays was prepared by using a two-step anodization technique. The characterization of AAO template was achieved by scan electron microscope (SEM) and X-ray diffraction. In this work we made an attempt to introduce rare earth ion into AAO. Eu3+ ion was introduced into the voids of porous anodic aluminum oxide film (AAO:Eu3+) by hydrothermal reaction, and the spectra of AAO:Eu3+ was discussed. The excitation spectra were measured by monitoring the 614nm emission. There are three sets of lines can be observed:one strong broad band located at about 254nm can be assigned to the O2-→Eu3+ charge transfer transition. Three weak sharp peaks located at around 363, 381 and 394nm consisting of one set of peaks; while another single peak is located at 465nm, these peaks are derived from 7D→5D absorbing transition of 4f electrons of Eu3+. Under 254nm light excitation, the characteristic red emission peaks of Eu3+ ions were observed. The peak at 614nm is due to the 5D0→7F2 electric dipole transition of Eu3+, and its intensity is extremely stronger than that of the 5D0→7F1,3,4 transition, indicating that the Eu3+ ions located in the host lattice have lower symmetry. The results showed that the materials synthesized by this method have favorable color purity and higher quenching concentration.关键词：anodic oxidation;porous membrane;anneal;Eu3+;hydrothermal method96|64|0更新时间：2020-08-11
- 摘要：Efficient blue light organic electroluminescent (EL) devices were fabricated by using a highly fluorescent bis(2-(2-hydroxyphenyl)-pyridine)beryllium(Bepp2) as an emitting layer. The multiplayer devices, a Bepp2 emitting layer, and an electron transport layer were employed in order to obtain high performance. For the devices, the maximum luminance of 6200cd/m2 and electroluminascent efficiency of 1.3cd/A(0.71lm/W) were achieved. The EL spectrum peak of Bepp2 appeared at 451nm.关键词：organic electroluminescence;organic electroluminescent material;beryllium complex95|156|2更新时间：2020-08-11
- 摘要：Top-emitting organic light-emitting devices (OLEDs) offer a feasible fabrication of OLED displays on opaque substrates, such as Si wafers and active-matrix backplanes with complicated pixel circuits of thin-film transistors and integrate circuit. In top-emitting OLEDs, high reflectivity of the bottom anode is essential for achieving high luminance efficiency. Among various metals, Ag has the highest reflectivity for visible light. However, it is generally not considered as an ideal hole-injecting anode for OLEDs due to its rather low work function, not matching well the ionization potentials of organic materials commonly used in OLEDs. In this letter, we report a top-emitting organic light-emitting device on silicon substrate with high luminance and current efficiency utilizing Ag as electrodes and ultrathin quinacridone(QAD) as emitting layer. Surface-modified Ag and thin Ag films act as anode. The luminance reaches 13700cd/m2 at 10V and the maximum current efficiency of the device using such electrode is 4.3cd/A at 7V, which is about twice times than those devices without QAD. The improved performance is owing to the characteristics of quinacridone, which accepts excitation energy from tris(8-hydroxyquinoline) aluminium via Fster mechanism.关键词：organic light-emitting devices;top-emitting;luminance;current efficiency129|87|2更新时间：2020-08-11
- 摘要：In recent years aromatic diamine derivatives with good photoluminescent and hole transporting properties have been widely used in organic electroluminescence devices. However, their layer represents the weakest link in the electroluminescent structure considering the thermal stability of these materials. In this paper, 1,5-bis[N-(1-naphthyl)-N-phenyl] naphthalene diamine(NPN) with high purity was synthesized by liquid-phase Ullmann reaction and high quality film of NPN was formed on cleaned glass substrates by vacuum evaporation. NPN and its film were characterized by FTIR spectra, 1H NMR spectra, UV absorption spectra and fluorescence spectra. Differential scanning calorimeter (DSC) showed NPN has high Tg (129.7℃) and T m (245.7℃). Photoluminescent properties of NPN were studied by solvent effects on UV absorption spectra and fluorescence spectra. Stokes shifts of compound NPN, solved in such solvents with different polarity as cyclohexane, chloroform and ethanol, were calculated based on Bilot-Kawski equation and they were 3496, 5164 and 5402cm-1 respectively. Distinct difference of dipole moment of NPN molecule between the ground state and excited state, which was 3.74D, showed that the charge transfer in NPN molecule occurred. In addition photoluminescent properties of NPN film were investigated by UV absorption spectra and fluorescence spectra. The results indicate that the synthetic route in NPN is efficient and safe. According to UV absorption spectra the long wave absorption peak, which has contribution to fluorescence, is attributed to charge transfer transition from nitrogen to aromatic ring. UV absorption spectra and fluorescence spectra of NPN in ethanol solvent and its film show that the absorption and emitting peak have red-shift. It is indicated the molecules of NPN in its film form "J-aggregate". NPN film can emit intense blue fluorescence with peak wavelength at 448.6nm and bandwidth of 72.6nm (Chromaticity coordinates:x=0.1677, y=0.1400; Purity:0.7168) under UV excitation of 365nm. It is demonstrated that NPN is a good hole transporting material and blue electroluminescent material with good thermal stability.关键词：1;5-naphthalene diamine derivative;electroluminescence;thermal stability;hole transporting material;blue emitting material140|109|2更新时间：2020-08-11
- 摘要：Several novel unconjugated oxdiazole-containing ploy(aryl ether) type organic light emitting materials of PE1,PE2 and PE3 were synthesized through nucleophilic substitution reaction of monomer Ma [2,5-bis(2-ethyl-hexoxy)-1,4-bis{2,2′-〔5-(p-fluorophenyl)〕-1,3,4-oxodiazole}benzene] and another three parts of compounds(biphenol A, sulfonobisphenol A and mixed sulfono-biphenyl) in the mixture solution of N,N-dimethyl acetamide and toluene at a temperature of 165℃,catalysted by potassium carbonate. Their chemical structures were characterized by H 1 NMR and element analysis. Their solubility was apparently improved by introducing of double flexible side-chain substitutes. The polymers were obtained in a good yield via controlling reaction condition and polymerization temperature. Chemical and physical properties of these materials were investigated by absorption spectra, photoluminescent spectra and current-voltage relation. Absorption peaks of PE1, PE2 and PE3 at 374, 374, 397nm respectively are almost identical. Nevertheless, the photoluminescent peak of PE3 at 572nm exhibits a large bathochromic shift contrast to them of PE1 and PE2 at 439, 438nm respectively. Fabrications of simple devices based on these polymers with structure of ITO/polymer/Ca/Ag were firstly performed. Results show these materials have blue light emitting as well as good thermal stability.关键词：OLED;unconjugation;poly(aryl ether);oxdiazole118|68|0更新时间：2020-08-11
- 摘要：In this paper, the driving circuit design was introduced for active matrix organic light emitting diode display, the pixel electrode circuit was discussed. And the method was proposed for some peripheral integration of driving circuits on substrate using complementary poly-silicon thin film transistor (TFT) to reduce the lead lines between the OLED display and peripheral circuitry, and simplify the peripheral driving complexity. Based on the two-TFT pixel electrode circuit, we design the driving circuit on the panel. Firstly a kind of shift register circuit structure was given, and using this circuit and some accessory gate circuits the gate driver was composed for the scan lines. Further the data sampling circuit on panel was constructed. For reduce the connection lines with the peripheral driver, the data lines were divide into M blocks. When the gate bus line is enabled, the blocks are in operation one by one. Consequently the analog signal from the peripheral driver will transmit to the data lines. This data voltage is applied on the two-TFT pixel circuit to drive the OLED. Because the data voltage is different analog signal, the OLED current is different as the data voltage and its luminance change with the OLED current. By AIM-Spice software we simulate the driver integrated on the panel, and verify the gate driver and data sample circuit function. A specific programmable application specific driver IC design was proposed for active matrix organic light emitting diode display, it is achieved by using CPLD (Complex Programmable Logic Device) chip. We make use of the hardware description language VHDL to program the CPLD and generate the external control signal for active matrix OLED panel. And at the same time CPLD operates the data process and outputs the digital display data with grey scale, those digital data were converted to analog voltage signal and transmitted to data sampling circuitry on panel. Our design results were verified by simulation and synthesis. At last the outline of the specific application IC and OLED display was shown.130|128|1更新时间：2020-08-11
- 摘要：Organic light emitting diodes with microcavity structure have been fabricated. Comparing of the optimized cavity and non-cavity devices, the EL performances of cavity device was improved significantly. The pure-red emission of Eu3+ was observed, and the CIE coordinates were about (x=0.651, y=0.338). Because of the sharp-band emission of Eu3+ complex, the defect of OLEDs with microcavity structure, causing a blue-shift of emission peak with increasing emission angle, was weakened. The maximum brightness of 1 160cd/m2 was achieved at 19V, and the efficiency was enhanced at high current density.关键词：OLEDs;microcavity structure;Eu complex120|96|1更新时间：2020-08-11
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