最新刊期
卷 24 ， 期 6 ， 2003
- 摘要：From the viewpoint of application, electroluminescence (EL) is especially useful in the technology of flat panel display (FPD).Among the all types of emissive FPDs, inorganic electroluminescence (IEL) and organic electroluminescence (OEL) are especially promising’because of their several attractive characteristics.But there are still some deficiencies in their behavior.The main problem is the lack of blue colored emission in inorganic EL and the lack of electron transport materials and stability in organic EL.In view of the compensatory properties of IEL and OEL, it is quite natural to develop their superiority and minimize their inferiority.From this analysis, we are convinced that the heterogeneous junction made from organic and inorganic materials as well as the excitation with AC and DC sources may shed light on the possibility of combining their advantages.In the improvement of inorganic EL layered optimization has been proposed and investigated in detail.The aim of that structure is to strengthen the effect of electron acceleration by spatially separated addition of SiC>2 electron acceleration layer to the ordinary IEL layer.The semi-conducting property of the thin film of SiO2 is used for electron acceleration.After acceleration the energy of electrons may be raised up to more than 10 electron volts.These hot electrons have enough energy to excite centers of luminescence in the visible region by impact excitation.Since these energetic electrons are accelerated not in vacuum but in solids, the luminescence generated by their bombardment is called Solid State Cathodolumi-nescence or CL-like emission.This CL-like emission is a new form of excitation mode.In this paper, we introduce and summarize the physical background, experimental results and some important unsolved problems about this method.At the end we propose some methods to solve these problems.关键词：solid state cathodoluminescence (CL-like);electroluminescence;organic/inorganic hybrid device97|143|4更新时间：2020-08-11
- 摘要：With recent rapid advances in nanofabrication technology it has become possible to confine electrons in all three spatial dimensions in semiconductors called quantum dots.The electron energy spectrum of such quantum dot is fully quantized.Such systems are of great interest in fundamental studies, as well as in practical applications for microelectronic devices.Electron-phonon interaction, which plays an important role in electronic and optical properties of polar crystalline materials in three dimensions, will have pronounced effects in low-dimensional systems as well.Recently there have been a considerable number of theoretical studies on the same effects including the confinement problem in quantum dot system.Zhu and Gu have studied the effect of an external magnetic field on zero-dimensional polarons in the weak-coupling limit using the second-order Rayleigh-Schrodinger perturbation theory, and found that for a strong magnetic fields, the cyclotron mass in a parabolic quantum dot is split into two cyclotron masses.Zhou has calculated both the ground state and the exited state energy of strong-coupling magnetoplorons in a disk-shape quantum dot with Peker-tape variational method.In this paper, we investigate weak-coupling magnetopolaron’s properties in a parabolic quantum dot by the linear combination operators in the first time.It is shown that the bound state energy and binding energy decrease with increasing the effective confined length of the quantum dot, and enhance with enlarging the cyclotron resonance frequency.The Fig.1 and 2 present that the magnetopolaron ground state energy E0 of parabolic quantum dot is as a function of the effective confinement length and the cyclotron resonance frequency.The Fig.3 and 4 indicate that the magnetopolaron binding energy |Eb| of parabolic quantum dot effect as a function of effective confinement length and the cyclotron resonance frequency.We can see that the confine effect of parabolic quantum dot strengthens the ground state energy and the binding energy.关键词：linear combination operators;parabolic quantum dot;weak-coupling magnetopolaron88|81|2更新时间：2020-08-11
- 摘要：The properties of magnetopolaron in crystals and semiconductors influence on the properties of the crystals and semiconductors very remarkably.With the development of the material science and experimental technology, the properties of magnetopolaron in crystals and semiconductors have been of considerable interest.Many investigators studied the properties of the magnetopolaron by means of various theoretical methods and experimental methods.Wu et al.studied the properties of the 2D magnetopolaron using the Feynmann path-integral approach.Wei et al.calculated the induced potential, resonance frequency and the self-energy of an interface magnetopolaron using the Green-function method.Lassnig et al.discussed the theory of resonant magnetopolaron of 2D electron system in narrow gap semiconductors using the variational method.Madkour et al.studied the effect of magnetic field on magnetopolaron states in a polar crystal interface and emphasized the result that the presence of magnetic field leads to a local potential for charge carriers at the interface.Based on Wigner-Brillouin theory, Brancus and Stan investigated the state energy of an anisotropic three-dimensional polaron in a magnetic field.Wollf et al.investigated the bound magnetic polarons in semimagnetic semiconductors and the bound magnetic polarons in dilute magnetic semiconductors by the optical experiments.Employing Haga’s perturbation method, Hu et al.derived an effective Hamiltonian for the interface magnetopolaron in polar crystals.The properties of surface magnetopolaron in a magnetic field have been further discussed by Xiao and co-workers.Tokuda studied the mean number of phonon of the optical and the piezoelectric polarons by using improved Huybrechts method.However, the mean number of phonon of magnetopolarons in crystals has not been studied so far.In this paper, the properties of magnetopolaron which is a strong-and weak-coupling of optical phonon was discussed by using Tokuda’s improved linear combination operator and the Lagrange multiplier and the variational method.Numerical calculations for RbCI and GaAs crystal, as an example, are performed.The relational of the vibration frequency, the ground state energy and the mean number of optical phonon to magnetic field B and Lagrange multiplier u are discussed.The result illustrates that the vibration frequency of magnetopolaron will increase with increasing magnetic field B and Lagrange multiplier u, the ground state energy E will increase with increasing u and decreasing B, the mean number of optical phonon N will increase with increasing u.关键词：magnetopolaron;vibration frequency;mean number of optical phonon94|124|0更新时间：2020-08-11
- 摘要：In recent years, the properties of magnetopolaron in polar crystals have been of considerable, interest.Larsen proposed a fourth-order perturbation method to calculate the ground state energy of two-dimensional polaron in a magnetic field.Kandemir et aL.discussed the ground-state and first-excited-state energy of two-dimensional large magnetopolaron by using recently introduced squeezed Landau states.Wei et al.studied the cyclotron resonance mass and resonance frequency of the interface magnetopolaron using the Green’s function method.Xiu et al.using the variational method, studied the property of strong coupling magnetopolaron in a polar crystal slab.The energies of the ground state and the excited state were presented and the electron-surface optical (SO) phonon interactions at ground state and excited state were studied emphatically.Using Huybretch’s variational method and unitary transformation, the strong coupling between electron and surface optical (SO) phonons and the weak coupling between electron and bulk longitudinal optical (LO) phonons were studied systematically by Xia et al..Wang et al.investigated the magnetic field and temperature dependence of the properties of a magnetopolaron at the interface of polar-polar crystals in an external magnetic field by using the generalized Haga perturbation method.The properties of surface polaron in a magnetic field have been further discussed by the present authors and co-workers.Tokuda studied the property of the mean number of the optical and the piezoelectric polarons and the mean number of the acoustic and optical polarons via deformation potential by using improved variational method.However, the mean number of optical phonon of surface magnetopolarons has not been studied so far.In this paper, the properties of surface magnetopolaron which is a strong-and weak-coupling of optical phonon was discussed by using Tokuda’s improved linear combination operator and the Lagrange multiplier and the variational method.The ground state energy and the mean number of optical phonons of the strong-and weak-coupling magnetopolaron were calculated.Numerical calculations for AgCl and ZnS crystals, as an example, were performed.The relational of the vibration frequency, the ground energy and the mean number of optical phonon to magnetic field B and Lagrange multiplier u were discussed.The result illustrates that the vibration frequency λ of surface magnetopolaron will increase with increasing magnetic field B and Lagrange multiplier u, the ground state energy E will increase with increasing u and decreasing B, the mean number of optical phonon N will increase with increasing u.关键词：surface magnetopolaron;vibration frequency;mean number of optical phonon83|104|0更新时间：2020-08-11
- 摘要：Instead of photovoltaic devices which attract much attention, photoconductive devices were objects of our work.Two kinds of PVK/TiO2 bilayer devices were prepared, including S1:ITO/TiO2/PVK/Al and S2:ITO/PVK/TiO2/Al.The properties of charge transportation of organic/inorganic devices were investigated by dark current and photocurrent spectra.The small noises are better properties of PVK/TiO2 bilayer devices.For these two devices, both of photocurrent response peaks are at 340nm or so, which indicated that the main excited layer is PVK film and photogenerated excitons of PVK influenced on the production of photocurrent.The TiO2 film functioned as electron transporting and adjuvant excited layer.For dark current of two devices, the dark current of S1 was much smaller than that of S2.Dark current is resulted from: electron injection and transportation in PVK from cathode; hole injection and transportation in TiO2 from anode; hole transfer from TiO2 to the value band of PVK.These three points can be used to explain the smaller dark current of S1.For photocurrent of the two devices, the peak photocurrent of S1 at forward bias was 4 times of that of S1 at reversed bias, which was similar with the peak photocurrent of S2 at forward and reversed bias.The effective charge transfer at the interface of PVK/TiO2, proper charge transportation layers and the match of energy level and work function had been considered to be the main factors that influence on the intensity of photocurrent of the devices.The reasons induced different properties of two devices, including: different morphology of PVK/TiO2 interface caused by different fabricating sequences, the exchanged contacts near PVK film and TiO2 film and the different absorption because of excited light reaching the different film first which led to photocurrent response spectra of the two devices were different.As a result, the properties of device S1 is better than that of S2.With the increase of applied voltage, the tails of S1 photocurrent spectra at the short wavelength turned higher, but photocurrent spectra of S2 nearly had no tails, which may be attributed to the different absorption and trapping energy level.关键词：charge transportation;photoconductivity;dark current89|100|0更新时间：2020-08-11
- 摘要：Organic electroluminescence is one of the most promising technology for next generation of flat panel display.Hole transporting layer represents the weakest link in the electroluminescent structure considering the thermal stability of the materials.The most widely used hole transporting material, N,N’-bis (1-naphthyl)-N, N’-diphenyl-1, 1’-biphenyl-4, 4’-diamine (NPB), has a glass transition temperature (Tg) of 95℃, which is much lower than that of the electron transporting material, tris (8-hydroxyquinoline) aluminum (Alq3).Based on the good hole transporting property and suitable energy level matched with other materials of NPB, two new hole transporting materials: N, N’-bis(1-naphthyl)-N,N’-di(4-methylphenyl)-1,1’-biphenyl-4, 4’-diamine (NTB) and N, N’-bis(1-naphthyl)-N, N’-di(4-tert-butylphenyl)-1, 1’-biphenyl-4, 4’-diamine (NBB) were synthesized by introducing methyl and tert-butyl groups into NPB to improve its thermal stability.The glass transition temperature (Tg) of NTB and NBB measured by DSC are 108℃ and 129℃ respectively, showing better thermal stability than that of NPB.The ionization energy obtained by ultraviolet photoemission spectroscopy is 5.2eV for all of NPB and its derivatives.The emission peak in the photoluminescent spectra of the solid films of NTB and NBB are at 455nm and 460nm, which are close to the emission peak of NPB at 440nm.The organic electroluminescent devices using NPB, NTB and NBB as hole transporting layer (HTM) were fabricated with the structure of ITO/CuPc(20nm)/HTM(50nm)/Alq3(60nm)/LiF(0.5nm)/Al(100nm).The emission spectra of the three devices are the same and the green color light was emitted from the Alq3 layer.The turn-on voltages of the devices are 11, 9, 8V for NPB, NTB and NBB, respectively.The brightness of the devices at 15V are 1000, 1300, 1200cd/m2 for NPB, NTB and NBB.The devices with NTB and NBB also show better longevity than that of NPB in a prelimin ary test.关键词：NPB derivatives;hole transport;thermal stability;electroluminescent device110|138|4更新时间：2020-08-11
- 摘要：Three kinds of multi-layer light emitting diodes (LEDs) were fabricated, in which poly (phenylene vinylene) derivatives, such as poly (2-methoxy-5-(2-ethyl-hexoxy)-l,4-phenylene-vinylene (MEH-PPV), the alternating copolymer of triphenylamine and phenylene vinylene (TPA-PPV) and the alternating copolymer triphenylamine and phenylene vinylene (TPA-DMPPV) were used as light emitting materials, Alq3 was used as electron-transport materials, while emeraldine base form of polyaniline (PANI-EB) was used as hole-transport materials.It was found that the PANI-EB layer as a hole-transport layer introduced into the PPV derivative/Alq3 diodes reduced the threshold voltage and enhanced the emission intensity of the diodes.This might result from decreasing of the barriers of ITO/PPV derivative interface and benefit for the hole injection and electron/hole transport.Moreover, enhancement of the diode properties resulted in PANI-EB layer is related to the structure of PPV derivatives, and an order of TPA-PPV>MEH-PPV>TPA-DMPPV in lightness was observed.关键词：OLED;polyaniline;poly(phenylene vinylene)derivatives105|100|1更新时间：2020-08-11
- 摘要：We report the red organic light-emitting diodes doped with rubrene and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB).N, N’-diphenyl-N, N’-bis(1-naph-thyl)-(1, 1’-biphenyl)-4, 4’-diamine (NPB) and doped tri-(8-hydroxyquinoline)aluminum(Alq3) are used as hole and electron-transport layers, respectively.The performances of the co-doped diodes were found to be improved compared to the only DCJTB doped diodes.We attribute the improvement to rubrene which assists the energy transfer from Alq3 to DCJTB more efficiently.The energy transfer rates from Alq3 to DCJTB, from Alq3 to rubrene, and from rubrene to DCJTB are proximately calculated to be 1.04×109, 3.89×109, 2.79×109s-1 according to the fit of the fluorescence decay curves, respectively.It can be seen clearly that the energy transfer rate from Alq3 to DCJTB through rubrene is 2.7 times higher than that from Alq3 to DCJTB directly.关键词：organic light-emitting diodes;energy transfer;time-resolved photoluminescence spectra118|233|0更新时间：2020-08-11
- 摘要：The devices of polymer mixed with phosphorescence dye have the virtue,of high efficient, easy to fabricate.But our attention should be given to the congregation and phase separation of the small molecule, especially at high concentration.By using a matrix polymer PC (poly[2, 7-(9, 9-dihexylfluorene)-co-alt-2, 10-(cyclohexane-l-spiro-6/-dibenzo [d, f][1,3] dioxepin)]), a kind of PF (polyflorene) polymers which have twist structure and have broad band gap causing the emission have a blue shift about 20nm than PF, more close to the absorption of Ir(ppy)3(iridium(Ⅲ) tri(2-phenylpyridinato-N, C2)), that means it can get a better matching between the emission of polymer and the absorption of phosphorescence dye, and achieve higher efficient energy transfer.At low concentration (about 0.5%), the matrix polymer PC can transfer its total energy to Ir(ppy)3.At such low concentration, congregation or phase separation can result less problem.The device structure is ITO/PEDOT:PSS/polymer:Ir(ppy)3/Ba/Al.关键词：organic light emitting;phosphorescence dye;polymer;board band gap semiconductor100|163|1更新时间：2020-08-11
- 摘要：Exciplex formation at the organic interface and its potential application for emission color tuning have been investigated.The bilayer electroluminescent devices using N, N ’-bis(3-methylphenyl)-N, N’-diphenyl-[1, 1’-biphenyl]-4-4’diamine(TPD) as an hole-transport layer and 2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3, 4-oxadiazole(PBD) as an electron-transport layer was prepared.The thickness of the TPD and PBD were both 60nm, and the cathode material is air stable aluminum.The EL spectra of this device were different from the PL spectra of TPD and PBD, showing a new band in the wavelength region of visible light together with weak emission in the wavelength of 400-430nm originating from the emission of TPD.The exciplex formation was evidenced by measurement and comparison of the photoluminescence spectra of the TPD, PBD and TPD:PBD equimolar vacuum evaporated thin films.The EL spectra were changed with different driving current densities.With an increase of the current density, the emission resulting from TPD became stronger relative to that from exciplex, when the current density was larger than 12mA/cm2, the strength of emission from TPD became smaller relative to that from exciplex.Meanwhile, the peak of the EL spectra shifted towards longer wavelength as the current density was increased.The change of EL spectra with the increase of the current density leads to change of emission color from white with the current density more than 2mA/cm2 to yellowish green at current density of 40mA/cm2.Consideration of the energy levels of TPD(LUMO:2.4eV;HOMO:5.5eV) and PBD(LUMO:2.8eV, HOMO:6.2eV) suggests that the energy barrier for the electrons injection from the PBD layer into the TPD layer is much lower than that for the holes injection from the TPD layer to the PBD layer.Therefore, it is suggested that the exciplex is formed by the interaction between the electronically excited singlet-state generated by recombination of holes and electrons in the bulk of TPD layer and the ground-state of PBD.The maximum luminance of this bilayer device is 149cd/m2 at a bias voltage of 18.6V.关键词：organic interface;exciplex;electroluminescence127|120|0更新时间：2020-08-11
- 摘要：In multi-layered organic electroluminescent devices, it is very important to obtain accurate data of energy band structure of organic electroluminescent materials.There are mainly several methods, for example, UV-vis absorption spectroscopy, quantum chemistry calculation, and cyclic voltammetry, are usually used to obtain band gap and HOMO energy level, respectively.However it is too difficult to get precise data of HOMO energy level by cyclic voltammetry.In this paper technology of linear scanning voltammetry(LSV) is instead utilized to attain a result of oxidation potential (or HOMO energy level) due to electrochemical oxidation of organic electroluminescent material filmed on the working electrode.In this electrochemical system, the supporting electrolyte tetrabutyl ammonium perchlorate (TBAP) synthesized by ourselves is dissolved in CHCl3 as well as CH2Cl2.It showed that the results may be better in CH2Cl2than that in CHCl3 according to linear scanning voltammograms of Alq3 in 0.1mol·L-1 TBAP.It can be calculated that the HOMO energy level of Alq3 is 5.79eV from oxidation potential of linear scanning voltammogram of its film on the working electrode in 0.1 mol·L-1 TBAP(CH2Cl2), which is in good agreement with the result determined by other methods.We also have got the HOMO energy level of other electroluminescent materials, such as TPD, PBD, which is often acted as hole transporting material and electron transporting material.Their HOMO energy level is 5.44eV and 6.24eV, respectively.Then the LUMO energy levels calculated from their band gap are 3.0, 2.34, 2.94eV for Alq3, TPD, PBD.Less amounts of materials is consumed in this method.And the results showed that this method is faster and more convenient.关键词：OLED material;HOMO energy level;electrochemistry;determination100|112|10更新时间：2020-08-11
- 摘要：The notion that π-conjugated polymeric materials should possess interesting and useful electronic and optical properties is now well established in the scientific literature.Light-emitting polymers have revolutionized the flat-panel display technology.A large number of light-emitting polymers have been introduced during the last 10 years.Among these polymers, polyfluorenes are important class of electroactive and photoactive materials.In this thesis, a palladium-catalyzed Suzuki coupling method was used to synthesize a series of novel soluble conjugated copolymers from 9, 9-dioctyfluorine (DOF) and 2, 1, 3-naphthoselena-diazole (NSeD).The feed ratio of DOF to NSeD are 95:5 and 99:1.The polymers are materials emitting saturated red color (650-666nm) light.The maximal emissions of devices slightly red-shifted gradually with increasing NSeD’s content.The maximal external quantum efficiency of the polymer light-emitting devices (PLED) reached 1.05%.The result indicated that the use of conjugated polyfluorene as wide band-gap segment with a small amount of narrow band-gap dopant in the polymer main chain could provide a new way to combine high quantum efficiency along with color turning ability.91|87|1更新时间：2020-08-11
- 摘要：Rare-earth polymer complexes are promising new materials for luminescence and display applications because they combine both the advantages of rare-earth and polymer, but their optical properties are often degraded because of the poor solubility of rare-earth complex in polymer.In this paper, two rare-earth containing complex, europium octanoate and Eu (DBM)3 (phen), were synthesized first, and then were mixed separately with PMMA using physical and chemical methods.Thus two new kinds of rare-earth containing polymers were synthesized.The optical properties of the two materials were investigated.The emission intensity of PMMA-Eu(DBM)3(phen) is more than one order higher than that of PMMA-Eu(OA)3.The emission from PMMA-Eu(DBM)3(phen) is only due to Eu3+:5D0→7F2 transition, while the emission from PMMA-Eu(OA)3 contains not only the transitions from Eu3+:5D0→7F2 but also transtions from other 5D levels to 7F2, which implied that the emission from PMMA-Eu(DBM)3 (phen) showed better color purity.Thus, PMMA-Eu (DBM)3(phen) may be a promising new optical material.Our results also implies that a non-centrosymmetrical conformation for rare-earth complex and a strong energy transfer between rare-earth ion and ligands are essential for a high optical performance of rare-earth containing polymer.关键词：PMMA;Eu(DBM)3(phen);europium octanoate [Eu(OA)3];luminescent properties96|86|2更新时间：2020-08-11
- 摘要：Organic small molecule and polymer luminescent materials have shown great potential for commercial application of organic light-emitting diodes (OLED), due to their high luminescent level and quantum efficiency.With the development of OLED more and more attentions were attracted to improve their efficiency.Because excitons are strongly confined for molecular semiconductors, the relative spin configuration of injecting electron (spin 1/2) and hole (spin 1/2) determines the excited state properties (singlet or triplet).Radiative decay from singlet exciton is fast and that from triplets is spin-forbidden.and.often very inefficient, but triplet emission is partially allowed in the presence of spin-orbit coupling and can be seen in molecule containing elements of high atomic number.The use of triplet emitters to improve OLED efficiency has already been proposed.Up to date, most center metal atoms are rare metals such as Pt, Ir, Ru, Re, Os etc., but it is essential for people to find some cheaper ones to realize efficient EL emission and to decrease the cost of OLED.Cu4 displays intense emission at 520nm with a quantum yield of 0.42 in-dichloromethane.Here we reported the results of devices using a blend film of Cu4 and the hole transport polymer PVK as the emitting layer.The structure of this device is ITO/Cu4: PVK/TAZ/Mg/Al and it can realize the emission of triplet Cu4 at 516nm.The research focused on energy transfer especially on EL process and the influence of oxygen on the photoluminescence of Cu4.关键词：phosphorescent material;doped system;Cu4;polymer EL devices100|99|0更新时间：2020-08-11
- 摘要：1.5mm emission from the first excited state to the ground state of Er3+ is very important for the applications in integrated optics and lasers.And we know that for a given transition of trivalent rare earth ions its properties mainly depends on the surroundings, say, host where the rare earth ions are inside.At this point, in order to find a better host material to incorporate the Er3+ a lot of kinds of materials, such as sulfide, chloride, fluoride, oxide glasses, and some kinds of crystals have been studied.Finally, amongst these materials the phosphate glass is thought to be a promising candidate for practical application.But there are problems still left to be solved, like chemical stability, lower transition temperature, and so on.In the present paper, a special host glass composition has been designed.Three samples with different Er concentration have been produced.Absorption spectra for these samples have been measured, the calculation results of absorption cross sections for the samples indicated that for a certain transition they are analogous.J-O parameters have been obtained to be 4.4(Ω2), 1.3(Ω4) and 1.1×10-2cm2(Ω6).Using the J-O parameters the oscillator strengths, radiative transition probabilities for other transitions and radiative transition lifetimes for some levels have been derived.Emission cross sections for the transition 4I13/2→4I15/2 have been obtained by using absorption spectra data or emission spectra data.A comparison between the emission cross sections derived from different approaches shows that week reabsorption is existent even in the sample containing 5% of Er3+, this fact implies that Er3+ doped this kind of material is suitable for the application in integrated optics.Fluorescence decay for the transition 4I13/2→4I15/2 room temperature has been measured for the samples with different Er3+ concentration.It is shown that for all the samples, its fluorescence decay lines obey the single exponential function.Through some calculations it could be concluded that the interaction type between Er3+ ions is of electric dipole, and the quantum efficiency for the transition 4I13/2→4I15/2 in our phosphate glass with lower Er3+ concentration is close to 100%.From the facts above it is expected that our phosphate glass would be an advanced material for the practical applications in integrated optics and lasers.关键词：phosphate glass;spectra;optical transition;fluorescence decay118|60|0更新时间：2020-08-11
- 摘要：High quality unintentionally doped InP, quaternary alloy GaxIn1-xAsyP1-y epilayers and the distributed Bragg reflectors(DBRs) formed alternately with high and low refractive index semiconductor materials have been grown on InP substrates in an atmospheric or low pressure metal organic chemical vapor deposition system made up in our laboratory.The trimethylindium(TMIn), trimethylgallium (TMGa), arsine(AsH3) and phosphine(pH3) are as the source materials.The properties of the epilayers were investigated by measurement of X-ray diffraction, X-ray rocking curve, scanning electronic microscope, low-temperature photoluminescence spectra in detail.The results indicated that the GaxIn1-xAsyP1-y, quaternary alloys epilayers grown by LP-MOCVD have good lattice match to InP substrates.The lattice mismatch is only 1×10-3 between GaxIn1-xAsyP1-y epilayers and InP substrates.And we obtained the InP and GaxIn1-xAsyP1-y epilayers with better optical quality.The FWHM of PL spectrum of the GaxIn1-xAsyP1-y epilayers and InP epilayers were 32, 9.3meV, respectively.The results measured by SEM indicated that we successfully obtained high quality DBR structures.They are formed by laying down alternating layers of GaxIn1-xAsyP1-y and InP semiconductors materials with different refractive index.The optical thickness of each layer of alternating growth layers is λ/4n (0.1μm).λ is the center wavelength, n is the refractive index of each alternating growth layer.Although when the number of alternating layers is 23, the reflectivity of the DBRs layers will reach 90%, but more epilayer will increase the resistance of the device and raise the threshold current.So it is important to optimize a suitable number of layers.关键词：MOCVD;InP/GaInAsP;distribution Bragg reflector109|96|1更新时间：2020-08-11
- 摘要：The mesostructured/mesoporous materials have attracted so much interest because of their large pore dimensions and volumes as well as high internal surface areas to use as potential catalysts and separation media.Recently the nanocomposites which are incorporated the organic molecules in the periodic mesostructured/mesoporous materials have received much attention.More efforts have been directed toward the goal of obtaining dye-doped structures for optical applications.In this paper the Rhodamine 6G (Rh 6G) molecules were incorporated in the nanometer pores of MCM-41 to form nanocomposite exhibiting different luminescent property.Such nanocomposite offer new opportunities for controlling the local environments for occluded dye molecules.In this letter we synthesized the polycrystalline powder of the mesostrucure MCM-41 by using cetyltrimothylammonioum bromide as the template.After calcined in air, we obtained the mesoporous MCM-41 framework.The dimensions of the mesopores of the MCM-41 framework are about 3nm.The Rh 6G/MCM-41 assemblies were obtained through ion exchange mixing of the calcined MCM-41 and Rh 6G solution at the concentration of 10-4 mol/L.The mixtures were stirred for 48h at room temperature.Then the nanocomposite was washed thoroughly with ethanol and dried in air.The nanocomposite was characterized by transmission electron microscopy (TEM),X-ray diffraction (XRD),and fluorescence measurements.An obvious blue shift and spectral broadening were observed in the emission of the nanocomposite, compared with Rhodamine 6G in ethanol solution at the concentration less then 10-10 mol/L.Considering the strong guest-host interaction between the Rh 6G molecules and the MCM-41 mesopores, the blue shift was attributed to the partial localization of the π-electrons in the chromophore.The intramolecular charge-transfer is originated from the strong guest-host interaction between the Rh 6G molecules and the MCM-41 mesopores.And the broad emission of the Rh 6G/MCM-41 can be interpreted as distribution of different site-specific emission.The result indicates that the nanocomposite represents useful property.It suggests a new approach to tunable wavelength range of dye laser.关键词：nanocomposite;Rhodamine 6G;MCM-41;fluorescence107|76|2更新时间：2020-08-11
- 摘要：We designed and processed a Φ100mm measurement integral sphere, which connected with a fluorescence spectrophotometer by optical fiber, to meet the require of studies and application of white light-emitting diode for especial illumination.The system can measure the spectral power distribution of LED.On basis of the spectrum distribution, we can calculate the optical and colorimeter parameter of LED such as CIE color coordinate, color temperature, color rendering index and so on.This method can avoid color-correction which is necessary for general photometer and the large data error caused by color-correction.关键词：LED;integral sphere;relative spectral power distribution;color-correction89|54|0更新时间：2020-08-11
- 摘要：We have analyzed two p-Si TFT pixel driving circuit with accurate model parameters using AIM-Spice software.We primarily focus on some aspects what we consider can impose much influence on OLED driving circuit, such as ratio of width and length of driving thin-film transistor, influence of storage capacitance and so on.Because there are many parasitical capacitances in the circuit, it is very important to choice reasonable storage capacitance to eliminate the influence of some disadvantageous factors and maintain the circuit to work.By the simulation results, reasonable T2 W/L ratios can be obtained.The simulation results also showed that the OLED grayscale could be adjusted by changing the data voltage.The impact of storage capacitor on output characteristic was discussed.The lower size capacitor will reduce the OLED current during the pixel electrode OFF period.And too large capacitor will increase a charge time constant, which impacts on the respond speed and brightness of OLED.The larger T1 W/L ratios will also result in the drop of the OLED current during the pixel electrode OFF period.So it is necessary to select them carefully.From the transient characteristic of the influences of the scan pulse voltage on output current, it is clear that the lower scan voltage value will result in the OLED current to be not proportional to data voltage.Thus the OLED brightness cannot follow the variation of the data voltage.The reasonable scan voltage value will solve the above problem.Through analysis, we conclude that best circuit parameters and using them can practice gray-scale signal response analysis in order to test its fast switching speed which is regarded as one of OLED best advantages.Conclusively with best circuit parameters above, driving circuit can drive OLED to desire brightness display, maintain driving current in every frame period, quickly respond to time-changing gray-scale signal, and minimum the influence of TFT non-linear character on OLED current to the least degree.All the works can be used for choosing reasonable parameters in the design and analysis of OLED driving circuit.关键词：OLED pixel driving circuit;active matrix OLED;AIM-Spice;p-Si TFT;simulation analysis125|100|4更新时间：2020-08-11
- 摘要：Since the Ag-O-Cs (S-l) thin film photoelectric cathodes was discovered in 1930, the polycrys-talline thin films as surface emission electron source were developed in different light sensitive materials, which successfully applied in night vision image tube, photoelectric tube, photo multiplier tube and low level light camera tube, and facilitated the developments of photoelectric and special purpose photoelectric imaging devices.The Sb-Cs and Na-K-Cs-Sb thin films in S series of photoelectric cathodes are limited in application because they have no solar blind characteristics, though they have higher quantum efficiency in the range of near UV (200-380nm).In recent, surface emitters with the stable, homogeneous and no change in photoemission when exposed to air are needed in some conditions.So, the studies on gold (Au), aluminum (Al) photosensitive films are noticeable in recent years.This paper gave an introduction of preparation of Au and Al thin film and made a study on the characteristics of their UV photoelectric emission.Preparation of metallic photosensitive film is simple.The quartz glass of YS series that has good thermal and chemistry stability was selected as the window in the range of 200-380nm, which has a transmittance to be larger than 85%.Evaporation coating method was used to prepare the metallic film.The film thickness was monitored by the system of testing transmittance or by the measuring apparatus for film thickness based on the theory of quartz vibration.The relationship between the transmittance of white light and the one of UV, and between the transmittance of UV and the photoelectric current density were proposed to be use as a criterion of optimum film thickness.The stability of Au film photoemission is good when exposed to air for many times.Because of it has high chemistry stability.The photoemission of Al film is stable in vacuum, but reduces fast when it was exposed to air and reaches to a definite value for 36 hours as the result of forming a natural oxidation layer.The relationship between thickness and photoemission of Au and Al were given in this paper, In a word, the theory of metal photoemission is relatively in maturity, where Fowler theory can be used as a tool for analyzing and discussing.Practically photoemission mainly depends on the film structure and preparation technology.The surface photoelectron source obtained from Au and Al film will find applications in characteristics test of microchannel plates, dynamic analogue of imaging tube and some special UV imaging devices.关键词：thin film photoelectric cathode;photoelectronic emission;lifetime82|67|2更新时间：2020-08-11
- 摘要：Microsphere plate (MSP) is a compact electron multiplier with temporal and spatial resolving power.It consists of glass beads with diameter of 40 to 60/μm.These glass beads were sintered to form a thin, porous plate.The surface of the glass beads is covered with partially conductive, secondary electron emissive material.The two faces of the plate are coated with conductive electrodes.When voltage is applied between the two electrodes, secondary electron multiplication takes place among the glass beads.MSP is used in vacuum system for the detection of charged particles.Its applications include particle imaging, time-of-light mass spectroscopy, particle monitoring, and electron microscopy.There are several key technologies in the process of fabricating final MSP.First of all, the formation of MSP substrate is the most important, due to the requirement of porosity and strength.The quality of the substrate will directly affects on the quality of final MSP.In this paper an introduction of the operating principle and characteristics of MSP was presented.Based on twin-ball sintering mode, a sintering rate formulation in the sintering process was established.In the actual sintering experiment, this twin-ball mode is superior to the panel-ball mode proposed by Kuczynski, so the sintering rate formulation agrees to the experiment well and can help us to operate technological process properly.In this paper the experimental processes on the formations of glass-beads and MSP body were presented also.The specific experiment included the followings: designed high lead glass as composition which can be used for formatting glass-beads, fabrication of glass-beads with vertical stove which was designed by ourselves, explored sorting technology of glass-bead and technological process of MSP.In the end, some comparison images of the experimental samples were given with that taken from reference.From these images.it will be found that our glass-beads’sphericity is good and sorting technology was well done, the sintering process controlled well, the MSP body has a quantity of connective gaps and passage, and has little distortion.Generally speaking, the experiment is successful.In the whole experiments, we think it is important to solve the sorting technology of glass-beads.In order to form gaps and passage, it needs precisely control the sintering process and make possible methods to improve the MSP quality.In order to minimize the pollution to MSP, the whole experiment must be made in the clean environment.The experiment on fabricating MSP is unprecedented at home, so the experiment is a new one.The experiment itself has embodied the spirit of innovation, especially in the process of formation of MSP body and minimizing the pollution to MSP in the whole process.All of these will enable the follow researcher to improve the fabricating process and pave the way for further study on MSP.关键词：MSP;MCP;sintering95|107|0更新时间：2020-08-11
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