最新刊期
卷 24 ， 期 5 ， 2003
- 摘要：Electroluminescent devices based on polymer/phosphorescent complexes have become a novel and attractive area of research in recent years. In this review, characteristics of both polymer matrices and phosphorescent dopants, the electrophosphorescent mechanism and device structure have been introduced. The advantage of phosphorescent materials is that they can utilize both singlet and triplet exciton states which can reach 100% internal quantum efficiency theoretically. The system requires polymer matrices satisfy energy matching between polymer host and phosphorescent dopant and have good carrier mobility. All the phosphorescent materials can be used as dopants for EL devices, which is a significant advantage of polymer host over small molecule host. Grafting and incorporating phosphorescent polymers can be used as a novel kind of luminescence materials with less self-quenching and more efficient energy transfer. Electroluminescence of these devices is from both Föster energy transfer and exciton directly recombination on the dopant, so it is necessary to be in view of the interaction and self-quenching of the excitons while designing the suitable structures of devices.关键词：polymer;phosphorescent materials;electroluminescence95|178|1更新时间：2020-08-11
- 摘要：Organic electroluminescence(OEL) devices have attracted considerable interest due to their potential application in flat panel displays.The color of EL devices is readily tuned by the proper choice of dopant dispersed in a host.Incomplete energy transfer can then result in light emission from both the host and the dopant,this way has been used to obtain white light from organic small-molecule-based devices. In this paper,luminescence of blue emitting material DPVBi doped with red dye DCJTB were investigated.Based upon the photoluminescence results of DPVBi doped by DCJTB with different mass concentration,the organic light emitting diodes(OLEDs) were fabricated with the electroluminescent layer consisting of DPVBi doped by different mass concentration DCJTB. In the device structure of ITO/CuPc/NPB/DPVBi:DCJTB/Alq3/LiF/Al,doping mass concentration of DCJTB contain 0%,0.03%,0.08% and 0.25%.It was observed that the blue bands gradually decrease with the increase of the doped DCJTB mass concentration.This indicates that energy transfer does occur from DPVBi to DCJTB.When the mass concentration of DCJTB is 0.08%,white light emission can be obtained.As the DCJTB mass concentration is further increased,the spectrum deviate from the white colour because of more energy transfered from DPVBi to DCJTB.It is expected that the CIE coordinates of the white colour could be further optimized by adjusting the dopant concentration.The results demonstrate that white emission can be realized through the incomplete energy transfer of blue emitting material DPVBi to red dye DCJTB in the same emitting layer.The white device shows the increase in relative intensity of blue to red emission with increasing applied voltage.For the white device with CIE coordinates x=0.25, y=0.32,the maxiumum luminance, luminance and the maximum luminous efficiency under current density of 20mA/cm2 are 7 822,489cd/m2 and 1.75 lm/W,respectively.关键词：blue emitting material DPVBi;red dye DCJTB;doping;luminescent properties101|99|0更新时间：2020-08-11
- 摘要：The discovery of electroluminescence in polymers has greatly promoted the development of LED. Exciton play an important role in those materials. Polyaniline, which belongs to the family of conducting polymers, has been the focus of increased physical and chemical studies in the past several years. It has been demonstrated that polyaniline may be distinguished in three discrete oxidation states, namely, leucoemeraldine-base (LB), emeraldine-base (EB) and pernigraniline-base (PNB). The research works about exciton of the pernigraniline-base (PNB), the fully oxidation of polyaniline, are less reported, a possible reason is that the chemical and electronic structure of this polymer are very complicated. In this paper, exciton in a PNB polymer under the electric field has been studied in the framework of the extended Ginder-Epstein model. In the earlier works, Liu Jie et al. has succeeded in explaining some experimental data of the PNB polymer by using this model and brought forth some new concepts such as combined polarons and combined solitons. Our numerical simulations showed that the exciton in this polymer is self-trapped and it consists of a bond order exciton associated with a ring torsion exciton. Further calculations showed that it will move along the main chain in weak electric field. When E≥3.6×104V/cm, the exciton is dissociated into a pair of positive and negative polarons. Polarization of the exciton has not been found in our work. We suggest that the model be modified such as the electronic interference be considered. The results about the behavior of exciton in zero and strong electric field are very similar to those of the conducting polymers such as m-LPPP, which has ever been calculated by Li Lei et al. We still have not found the relevant experimental data, so the above numerical solutions can only be considered as a reference.关键词：pernigraniline-base;electric field;self-trapped exciton96|69|0更新时间：2020-08-11
- 摘要：Since negative differential resistance phenomenon of the dye-doping polymer thin films was discovered, the mechanism of negative differential resistance has not been well explained due to many affecting factors. Several different interpretations were put forward, but most of them lacked the experimental evidence. In this paper the factors affecting negative differential resistance of the dye-doping polymer thin film devices was studied, and experimental evidence brought forward in order to further interpret the principle of organic negative differential resistance. Many kinds of dye-doping polymer thin films devices were fabricated. Factors affecting negative resistance including different organic dyes and polymeric matrices, varied composition and thickness of the film, ITO and anodic polyaniline were investigated respectively. In an atmosphere, a remarkable negative resistance phenomenon was found in low voltage state (3～4V) at room temperature. The maximum ratio of peak current to valley current was approximately 8. The appearance of the negative differential resistance phenomenon and the magnitude of ratio of peak current to valley current depended on thickness of the film, structure and fabrication technique of the device. When negative differential resistance was big enough, the electrical current flowing past the negative differential device would be small hence the peak of electrical current would be concealed. An equivalent circuit model composed of a diode in parallel with a negative resistance device was put forward in order to interpret negative differential resistance phenomenon. The negative differential resistance appeared to be caused by an imblanced injection of charge carriers. A novel soluble PPV derivative containing oxadiazole electron transporting group on the main chain (OPPV) was designed and synthesized, which had the abilities of hole and electron transmissions. The device showed stable N-type negative differential resistance characteristics in the atmosphere. Compared to inorganic negative differential resistance device, organic negative differential resistance device has many advantages such as easier fabrication as well as lower cost. If related materials and technologic conditions could be controlled, the negative differential resistance phenomenon would be observed distinctly and it is possible to develop a novel organic negative differential resistance device.关键词：organic negative resistance;organic dye;doping;polymer;OLED84|113|1更新时间：2020-08-11
- 摘要：After the first report of electroluminescence (EL), in poly(p-phenylenevinylene) (PPV)-based diodes, much effort had been devoted to the preparation of novel conjugated polymers in order to change the emission color and/or to increase the EL efficiency. All kinds of new materials and new techniques in the field of PLED have been developed in recent years, it promoted the development of PLED greatly. However, there are still some problems which block the industrialization of the PLED. The poly(p-phenylenevinylene) (PPV) is one of the familiar electroluminescent materials, which has the property of poor solubility, however. The soluble poly(2-methoxy-5-butoxy)-p-phenylene and poly(2-methoxy-5-octoxy)-p-phenylene with high yield were prepared by dehydrochlorination process in this paper. The product shows good solubility and film forming property, and the film was analysed with scanning electron micrograph(SEM), the results showed that the PPV prepared have the property of excellent filming forming. Single-layer device and multi-layer device with Alq3 as electron transfer layer and PEDOT as hole transfer layer have been prepared with PPV synthesized, and the property of electroluminescence have been studied. The effects of various factors to the light-emitting voltage and stability of the device, such as the purity of PPV,the thickness and quality of PPV films, and the structure and techniques of devices, have been studied in this paper also. The result showed that the multi-layer device is more stable than that of the single-layer device. The light-emitting starting voltage of the single-layer device is 4V, and the light-emitting starting voltage of the multi-layer device is 6V. The peak wavelength of the single-layer device and the multi-layer device are both at about 580nm.关键词：PPV;dehydrochlorination;synthesis;electroluminescence;device80|95|0更新时间：2020-08-11
- 摘要：Conjugated polymers have attracted much interest in the last several years for their versatilities and potential application in light-emitting devices. Hyperbranced polymers have been intensively investigated recently due to their good solubility, processability, tunable physical and chemical properties and easy synthesis by called one-pot reaction. Our aim was to synthesize hyperbranched conjugated polymers combining the merits of both dendrimer-like structure and linear conjugated units. In order to improve hole-transporting ability of the material, triphenylamine was introduced into the polymer as connecting units. With triphenylbenzene as cores, a novel hyperbranched polymer (TPA-TPP) was synthesized based on A2+B3 reaction. The synthetic method, molecular structure and photophysical properties were investigated systematically. TPA-TPP showed good solubility, film-performing property and high thermal stability. The polymer was synthesized with molecular weight of 1 700; the relative low value was related to the Wittig-reaction used in the synthesis and the large steric hindrance of the branches. Due to the electron-donating triphenylamine moieties, it would be expected that the twisted intramolecular charge transfer state (TICT) exist at the excited state, which was evidenced by the solvent effect of polymer fluorescent spectra. TPA-TPP showed a broad and structureless emission band, and the peak position of the band red shifted with the increase of solvent polarity, the way of tuning emission wavelength of the material by simply changing the environment of TPA-TPP distributed may be provided. Fluorescent spectra of TPA-TPP showed that there was a red-shift of 10nm only from dichloromethane solution to thin film, which was much smaller than those of the linear conjugated polymers (normally larger than 50nm). The reason may be due to the large steric hindrance caused by triphenylbenzene and triphenylamine. Our results exhibited that by introducing groups with large steric hindrance into the light-emitting polymer, the red-shift of emission band from solution to film could be reduced, which was favorable for application in light-emitting devices. Light-emitting diodes with the structure ITO/PEDOT/TPA-TPP/Ba/Al have been fabricated. The electroluminescence spectrum of TPA-TPP exhibits a broader profile with emission ranging from 430nm to 740nm.关键词：hyperbranched conjugated polymer;hole-transporting moieties;TICT;triphenylbenzene80|97|2更新时间：2020-08-11
- 摘要：Highly efficient organic electroluminescent devices (OLEDs) need to achieve an effective and balanced injection of carriers. The injection of holes is usually easier than that of electrons in most of OLEDs. In order to investigate the mechanism and the effect of using 8-hydroxy-quinolinato lithium (Liq) as an injection layer on the performance of OLEDs, devices with a structure of ITO (indium tin oxide)/TPD (N,N′-diphenyl-N,N′-bis (3-methylphenyl)-1,1′biphenyl-4,4′diamine)/Alq3(tris-(8-hydroxy-quinolinato) aluminum)/Liq/Al were prepared. Experimental results showed that the efficiency of the device with Liq as an electron injection layer is very similar to that of device with LiF as an electron injection layer, but is got about five times higher than that without Liq. This may be attributed to the enhancement of electron injection from the introduction of Liq, which generate a dipole layer and form an ohmic contact between aluminum electrode and organic Alq3 layer.117|190|1更新时间：2020-08-11
- 摘要：Polymer light-eimtting diodes (PLED) have been demonstrated to possess advantages of sufficient brightness, a broad range of emission color and long operating lifetime. Monocolor PLED has been, so far, made great progress in luminance efficiency and lifetime, specially for green EL emission. However, polymer color emission devices are still under development because of soluble polymer film casting technique which easily make large area rather than small area pixel. So new methods to fabricate polymer color emission devices are being created in device structure. In the work, we developed a new technique to fabricate multicolor polymer EL devices with multiplayer polymer film structure. The device structure consists of ITO/PEDOT/polymers/Ba/Al. The polymers include those which can emit blue, green and red fluorescence, and same color light in a device under electric field. Al electrode acts to protect metal Ba from oxidation,also. The threshold voltages of the device are 2.5V for blue emission, 2.5V for green and 1.8V for red, respectively. The CIE coordinates of the EL emissions are x=0.16, y=0.16 for blue, x=0.34, y=0.58 for green and x=0.60, y=0.39 for red. EL quantum efficiencies for red, green and blue emission are 1.2%, 1.7% and 2.5%, respectively.The multi-layered film structure is promising in potential application of full color polymer light emitting displays.关键词：polymer;electroluminescence;multi-color emission89|123|0更新时间：2020-08-11
- 摘要：As a potential candidate for organic electroluminescent material, bi(8-hydroxyquinolinolato)magnesium was synthesized by a reaction of magnesium chloride and 8-hydroxyquinoline. The composition of the complex was confirmed to be Mg(C9H7NO)2·2H2O by elementary analysis, thermogravimetry analysis and IR spectroscopy. Ultra-violet absorption spectrum was obtained in alcohol solution. The maximum emission of the compound is at 472nm. The results showed that the complex has excellent photoluminescence property and can be applied as a green-blue emitting material. With the complex as an emitter and an electron transporting layer, bright blue-green electroluminescence diodes were fabricated by conventional vacuum-coating method. The structure of the diodes was ITO/TPD/Mgq2/Al. The EL spectrum for device was observed and was very similar to the corresponding PL emission spectrum, clearly the magnesium chelate acted as the emitter in the device. Comparing to the PL spectrum, the maximum emission wavelength in EL emission spectrum shifts from 472nm to 528nm, indicating that the exciting transporters(electrons and holes) combine in a wider energy range. The J-V curve implied that the device had the standard characteristic of diode communication. The L-J curve showed that the turn-on voltage for the device was satisfied, the maximum luminance was 12 000 cd·m-2 under 15V drive voltage.关键词：bi(8-hydroxyquinolinolato)magnesium;organic electroluminescence;light emitting device121|119|0更新时间：2020-08-11
- 摘要：Polynuclear complexes with d10 metals, which often possess unique structures and properties, have drawn a lot of attention. For the preparation of tetranuclear zinc carboxylate, four methods have been used: (a) by the reaction between zinc oxide and the carboxylic acid in the appropriate proportion; (b) by the thermal decomposition of the neutral carboxylate Zn(RCO2)2; (c) by the reaction of zinc oxide with the neutral carboxylate and (d) by the hydrolysis of the neutral zinc carboxylate. In the present work, a tetranuclear zinc benzoate Zn4O(C6H5CO2)6 was synthesized by the thermal decomposition of zinc benzoate Zn(C6H5CO2)2 in an inert atmosphere. Its electronic absorption, infrared, excitation and emission spectra were investigated. The nature of luminescence and the relationship between structure and luminescent property were discussed. Structure refinement showed that Zn4O(C6H5CO2)6 has a cubic structure, space group Ia-3d, with great crystal cell: a=41.0063(18)Å, V=68953(5)Å3, Z=48. In the crystal all benzoates coordinate with zinc atoms in a bidentate bridging mode, four zinc atoms form a regular tetrahedron. Each Zn4O(C6H5CO2)6 molecule is in an octahedron geometry and every four adjacent molecules constitute a slightly distorted tetrahedron. The complex Zn4O(C6H5CO2)6 possesses an infinitely extended three-dimensional supramolecular structure. It emits a green luminescence under the excitation of UV/blue light in solution or in the solid state. Its excitation and emission bands at 290～330 and 370nm are attributed to the ligand-centered transition. The excitation bands at about 460nm and the emission band at about 530nm are assigned to the LMCT (ligand to metal charge transfer) transition of pπ*(L,O2-)-4sσ(Zn2+). The luminescent property has relation with its particular structure. In the nature of its excitation and emission spectra, a leading role is played by the arrangement of Zn4O tetrahedron around the central oxygen atom because of the absence of similar bands for the simple mononuclear complex Zn(C6H5CO2)2. Furthermore, in addition to the Zn4O unit, the OZn4O12 one is needed to explain the nature of experimental bands. The green emission of complex Zn4O(C6H5CO2)6 makes it a possible candidate for luminescent material.关键词：benzoic acid;zinc;tetranuclear coordination compound;synthesis;luminescence87|148|1更新时间：2020-08-11
- 摘要：Since the first report of polymeric light-emitting diodes (PLED) based on poly(p-phenylenevinylene) (PPV) by the Cambridge group in 1990, great progress has been made in PLEDs due to their promising applications in the field of patterned light and flat panel display. Single-color and full-color have been realized. At present, the main work is to improve the performance of PLED with high quantum efficiency, high luminescence and long life. But it’s very difficult to get these because the properties of these functionalized light-emitting polymers can be easily modified by external stimuli such as temperature, pressure and solvent, etc. Though major effort has been focused on determining the relationship between polymer chemical structure and conformation and the corresponding physical and chemical properties, there is not still good theory to direct us to utilize the conformational transition and the effects of the aggregation. In this work, we focus on the effect of the aggregation and conformation of functionalized light-emitting polymers on their luminescent properties. The materials we used here are poly[(2, 5-didecyloxy-1, 4-phenylene) vinylene] (DD-PPV) and poly[2-methoxy-5-(2'-ethylhezyloxy)-1, 4-phenylene-vinylene] (MEH-PPV). The UV-Vis absorption peaks of MEH-PPV centered at 494nm in chloroform solution and 504nm in the drop cast film. And its maximum emission has a red-shift from 555nm in solution to 603nm in solid state. The red-shift of absorption from solution to solid state is commonly observed and usually is attributed to the aggregation in the solid state. Moreover we investigated the UV-Vis absorption features of MEH-PPV in the mixtures of chloroform (good solvent) and methanol (poor solvent). Upon increasing the amount of methanol, an evident color change was observed, e.g. the red shift of the maximum of absorption from 495nm to 548.5nm, which indicates that a more conjugated and ordered structure appears upon aggregation. MEH-PPV in solution might have two distinct conformational structure, a co-planar (or nearly planar) conformation and the twisted structure. The presence of an isosbestic point confirms our hypothesis. However, blue shift of the maximum absorption of DD-PPV was observed in the same mixtures. Perhaps it’s because there is only one kind of conformation. So the poor solvent methanol decreases the conjugated length of this two polymers.关键词：light-emitting polymers;solvatochromic effect;UV-Vis absorption spectroscopy;fluorescent spectroscopy109|147|0更新时间：2020-08-11
- 摘要：Conjugated polymers offer many advantages as materials for light-emitting diodes. They are mechanically flexible, and can be fabricated and patterned with relative ease by casting from solution, and the emitted light color of these semiconducting and luminescent polymers can be controlled by designing the molecular structure. Among the blue emitting materials, poly(paraphenylene) (PPP) and its derivatives are promising because of their high photoluminescence(PL) efficiency. The stability of PPP and the solubility of PPP with side groups are the focus of our concern. Four luminescent materials of conjugated copoly(phenylene-alkoxyphenylene)s were synthesized, all these polymers have excellent solubility in common organic solvents. The UV-Vis absorption spectra and the photoluminescence properties of their films and solvents were studied, and their energy band structures were inspected through electrochemical methods. The effect of alkoxy side chains on luminescence intensity of the polymers was discussed. The results showed that these four polymers emitted blue lights with excitation of UV rays, and energy values of π-π* transition were within 3.2-3.3eV. The luminescence intensity reached the peak when the polymers had the alkoxy side chain with about 10 carbon atoms.关键词：copoly(phenylene-alkoxyphenylene);photoluminescence;energy gap91|123|1更新时间：2020-08-11
- 摘要：Amorphous semiconductor is a quickly developed new subject, and is one of the most active area in material science. Because amorphous semiconductor is a covalent and unordered meshwork, hasn’t long periodic structure, so amorphous semiconductor has different photoelectric characters compared with crystal semiconductor, and has great potential application. As a wide direct band gap semiconductor material, ZnO is of interest for short wavelength electro-optical devices such as light-emitting diodes and laser diodes, especially for lasers with low thresholds at high temperatures due to its large exciton binding energy of 59meV. In recent years, there has been great interest in growth of ZnO by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), sol-gel, reactive evaporation, thermal decomposition, and electro-deposition and so on, but all of these ways are used to prepare crystal ZnO, there are few reports on preparation of amorphous ZnO. In this paper, we synthesized ZnO powder by solid-state pyrolytic reaction, and charactered by XPS, XRD, TEM, infrared spectrum and PL. The XPS indicated that the sample is ZnO, and the TEM reveals the ZnO has not crystal structure. XRD proved the ZnO is amorphous and include little crystal ZnO, and can make a conclusion that amorphous ZnO include complex H2O from the infrared spectrum. The amorphous ZnO shows an extremely enhanced ultraviolet emission (visible emission was quenched fully). Study on amorphous ZnO will be helpful for fabricating optoelectronic devices and accelerate the development of amorphous semiconductor.关键词：solid-state pyrolytic reaction;ZnO;amorphous;strong ultraviolet emission107|106|0更新时间：2020-08-11
- 摘要：In recent years, the development of molecular-beam epitaxy techniques and metal-organic chemical-vapor deposition techniques have made possible the fabrication of quantum well structures in which the electrons are confined to move in one or two dimensions. Due to their small sizes these structures present some special physical properties. Optical and electronic properties of quantum wells, quantum wires and quantum dots have been the subject of both theoretical and experimental investigations in recent years. Polaron in quantum wires are markedly different from those in bulk materials, due to the presence of wire potentials with the form V, which confine the carriers motion in the ρ-plane transverse to the wire axis. The confining potential may bring out many rich phonon modes such as confined phonon modes, interface phonon modes, etc. Even for the confined phonon itself, there are so many types: rectangular, cylindrical and parabolic types. A variety of phonon modes and various types of the wire potential have given rise to rich and varied investigations in this field. For the energies of polaron problems in QW, few author studied energies of polaron itself. In this paper, by solving the effective mass equation with the variational method, we have studied the ground state energies and the electron-phonon interaction energies of polaron in cylindrical quantum wires.The energies of the ground state and the absolute value of the electron-LO phonon interaction energies were given. The numerical results show, with the decreasing radius of the quantum wires, the ground state energies and the absolute value of the electron-LO phonon interaction energies increase mononically.关键词：quantum wire;polaron;ground state energy;the electron phonon interaction energy102|104|3更新时间：2020-08-11
- 摘要：Rare earth ions doped inorganic materials have been extensively applied to many fields, such as display techniques, laser medium, and fiber communications. Trivalent thulium (Tm3+) in different hosts exhibits interesting optic and magnetic properties that are amenable to convenient experimental and theoretical studies. The fluoride compound doped with Tm3+ has been identified as an excellent candidate of laser material, due to its high efficiency, narrow line widths, and unusually large transition cross sections. In addition, the crystal structure of the fluoride compound permits greater doping concentrations of larger rare earth ions than other widely used host materials such as yttrium aluminum garnet and yttrium scandium garnet. For many applications, it is important to know the detailed energy level scheme of RE3+ in the appropriate host matrix. However, well-established investigations of the energy level scheme of Tm3+ ion in various host matrices are rather scarce. Detailed characterization of the interactions effective in the formation of the energy level scheme of the Tm3+ ion had been carried out mostly for the simple fluorides and oxide matrices. In addition, the maximum degeneracy of 91, which is rather low for an RE3+ ion, can be treated theoretically and by computational means easily as a whole without any truncations. In this paper the experimental results of absorption and emission spectra of K2YF5:Tm3+ at 12K were reported. The optical data were interpreted in terms of the C2v point symmetry of the Tm3+ site in the K2YF5 matrix using the multipolar and group theoretical selection rules for electronic transitions. The Stark energy levels of ground state 3H6 and excited states 1D2, 1G4, 3F2, 3F3 and 3F4 were assigned clearly. The experimental energy levels are compared with those of calculated by a phenomenological model, in which the Hamiltonian includes the electrostatic, spin-orbit interactions and crystal field interactions. The simulated treatment of the free ion and crystal field interactions within 4f12 electron configuration yielded a satisfactory agreement with the experimental values of 32 Stark components, with a quite small root mean square deviation of 18cm-1. In older to acquire the information of crystal field effect, the parameters S and Sk were introduced.In addition, decay curves of 1D2 and 1G4 emissions in the samples with different Tm3+ doping friction were discussed. Cross relaxation mechanisms have been used to explain the variations of the lifetimes.关键词：photoluminescence;crystal field analysis;K2YF5：Tm3+116|271|0更新时间：2020-08-11
- 摘要：The local structure of rare-earth ions in solid host is of great research interest for designing new luminescence materials, and Eu3+ ion is a good probe to reflect the local environment around rare-earth ions in different materials. In this paper, Eu3+-doped La2O3-3B2O3 crystal and glass samples were prepared by solid-state reaction under different calcination temperatures. By controlling calcination temperatures at 960℃ and 1 200℃, respectively, the crystal and glass samples with the same composition were obtained. The Eu3+ ions in the two samples present different flourescent properties. With the excitation of 394nm ultra-violet light, the glass sample presents an intense 618nm emission, while the crystal sample gives a dominant 696nm emission. The emission spectra, the phonon sideband spectra, the charge transfer bands and the lifetimes were measured to clarify the different luminescence of the two samples. In the emission spectra, both of the two figures (Fig.1, Fig.2) present the characteristic luminescence of Eu3+ ion, including emission peaks at 590nm (5D0→7F1), 618nm (5D0→7F2), 650nm (5D0→7F3), 696nm (5D0→7F4). Among these transitions, the 5D0→7F1 transition is a magnetic dipole transition, and the 5D0→7F2 transition is an electric dipole transition. It was found that, with the transition from crystal phase to glass phase, the intensity ratio of 5D0→7F2 to 5D0→7F2 of Eu3+ ion was enhanced, which indicates that the value of J-O parameter Ω2 was increased. The local structures around Eu3+ ion in the two different host were investigated by measuring the charge transfer bands and the phonon sideband spectra associated with the 5D2←7F0 transition. It was concluded that B-O vibrational mode inside the various borate rings and nonbridging B-O-1 bonds stretching mode with phonon energy of 1 900, 1 500cm-1, respectively, exist in both of the two samples. The charge transfer bands confirmed that the near coordination ions of Eu3+ are different in the two samples.关键词：borate;Eu3+;spectral properties;local structure132|214|5更新时间：2020-08-11
- 摘要：The luminescence of Mn4+ ions shows different features for MgAl2O4,ZnAl2O4 and LiAl5O8 which all have a spinel structure. In LiAl5O8, the emission spectrum of Mn4+ consists of a sharp line at 660nm overlapped on a broad band with maximum at 680nm. The former is assigned to the 2E→4A2 transition of Mn4+ and the latter is attributed to the vibronic side band. The emission of Mn4+ showed a higher intensity in LiAl5O8, and however, only a weak emission was observed in MgAl2O4 and almost no luminescence was recorded in ZnAl2O4. The differences in the intensity of the Mn4+ emissions for the three spinel compounds can be illustrated by the fact that the compounds have different micro-structures and composition elements. In the perovskite-related aluminates LaAlO3 and GdAlO3, The Mn4+ ions show 2 and 3 sharp emission lines, respectively, under 254nm excitation at room temperature. The Mn4+ emission peaks locate at 695 and 725nm for LaAlO3:Mn,Ca and at 680, 700 and 715nm for GdAlO3:Mn,Ca. These lines are assigned to the 2E→4A2 transition of Mn4+ ions and its phonon-coupling transitions. Energies of the phonons asso-ciated with the 2E→4A2 transition have been estimated. Both the excitation spectra of Mn4+ in LaAlO3:Mn,Ca and GdAlO3:Mn,Ca show two broad bands. One locates at about 300nm and the other at about 500nm. The strong band at about 300nm is assigned to the O2-→Mn4+ charge-transfer band and the weaker band at about 500nm is due to the 4A2→4T2 transition of Mn4+. The 4A2→4T1 absorption transition is almost hidden under the charge-transfer band and exhibits only a little peak or shoulder at about 330nm. From the energy of the 4A2→4T2 transition we estimate crystal field parameter Dq to be equal to 2 000cm-1 for LaAlO3:Mn,Ca and 2 040cm-1 for GdAlO3:Mn,Ca.关键词：luminescence;Mn4+;aluminates;spinel;perovskite136|135|4更新时间：2020-08-11
- 摘要：For solving the problem on the degradation of light efficient of BAM phosphor,BAM phosphor was coated with alumina sol(the diameter of the particle is about 10nm) making an alumina protective film around the individual powder particle of BAM.The surface state and surface component of the coated powder were investigated with SEM and Xps.The alumina film coating rate on the power surface reached to be about 90% and the film layer was found quite stable as it could stand various processes, e.g., washing with water, coating in lamp tube and baking at high temperature. The BAM phosphor’s luminescence performance was tested and compared to uncoated phosphor. An evident improvement has been found in the thermal stability. The thermal deterioration of the phosphor was alleviated obviously after annealing at 500,550, 600 and 650℃ for 30min. By the way, the fluorescent lamps of single colour were prepared using the coated phosphor for the time lighting test. The degradation of light efficient was less than uncoated one evidently. For example, the degradation of the lamps after lighting for 1 000h, for the coated BAM phosphor was 6.1%, but 18.5% for uncoated one. The mercury amount adsorbed on the phosphor was determined by cold vapour atomic absorption spectrometry(CVAAS), and the result proved that the adsorbed amount on coated BAM phosphor was evidently less than that for uncoated one. Based on a series of results in the test, it was proved that the coating treatment of BAM phosphor can protect the phosphor powder and can improve the thermal stability and alleviate the decrease in luminance of the BAM phosphor. Therefore, the study by coating treatment for BAM phosphor with alumina sol is of significance in practice.关键词：phosphor;coating;degradation of light efficient;alumina sol117|89|6更新时间：2020-08-11
- 摘要：The Eu3+-doped LaPO4 phosphor was prepared with the conventional solid-state reaction method. Stoichiometric amounts of (NH4)2HPO4 and H3BO3 were milled and fired in air at 900℃ for 2h, and washed thoroughly with distilled water. The white powder, BPO4, was dried at 110℃ in an oven for 3h. Stoichiometric amounts of La2O3, BPO4, Eu2O3 and Li2CO3 were milled and subsequently fired in air at 900℃ for 2h, and treated with 2mol·L-1 HNO3 and 10% NH3·H2O for 12h, washed thoroughly with distilled water. The product was dried at 110℃ in an oven for 3h, and finally stored in a desiccator until use. The Eu3+-doped LaPO4 phosphor was characterized by powder X-ray diffractometry. According to our measurements with X-ray diffraction, this material belongs to monoclinic crystal system with its lattice constants: a=6.84Å, b=7.08Å, c=6.46Å, β=103.85°, it is consistent with space group P21/n (No.14). The excitation and emission spectra were measured. The luminescence properties of Eu3+-doped LaPO4 and energy transfer mechanism were discussed. Under 393nm radiation excitation, the emission spectra of LaPO4:Eu consists of the sharp line emissions in the range of 500～720nm from the transitions of electrons in 4f shell of Eu3+. The main peak at 612nm can be ascribed to the 5D0→7F2 transition of Eu3+, it shows a strong red emission, and the 5D0→7F2 transition emission splits to 610, 614nm. The peak at 592nm can be ascribed to the 5D0→7F1 transition, Eu3+, it splits to 590, 594nm also. The excitation spectra of Eu3+ 5D0→7F2 transition emission have two parts, the wide band between 200～300nm and sharp lines between 300～600nm. The wide band includes both charge transfer excitation of PO43- and charge transfer excitation of Eu3+, and the sharp lines originate from Eu3+ f-f electron transitions. The strong evidence from excitation spectra, emission spectra of this system showed that there is the energy transfer from host lattice to activator in the process of luminescence.关键词：LaPO4;Eu3+;luminescence;synthesis88|105|5更新时间：2020-08-11
- 摘要：In this paper, spectral difference between nanocrystalline yttria doped with europium (Y2O3:Eu3+) and the bulk ones was reported. Besides a 580.6nm line similar to that in the bulk Y2O3:Eu3+, a new broad excitation line at 579.9nm was observed in the excitation spectra of nanocrystals (NCs). The 579.9nm peak relative to the 580.6nm one decreases a little as temperature increases. The fluorescent lifetime excited by 579.9nm line became slightly shorter than that of the 580.6nm line. We suggest that in nanocrystalline Y2O3:Eu3+ the broader 579.9nm excitation peak originates from the luminescence of Eu3+ ions near the surface, and the 580.6nm one from the internal Eu3+ ions. The surface to volume ratio is quite small (1%) in the micrometer particles, while it increases significantly as the particle size decreases to several nanometers. This will lead the surface effects to be effective. As well known, the energies of electrons in 4f states of rare earth ions are affected by the crystal field. In nanocrystals, rare earth ions near the particle surface are at the sites microscopically inequivalent with those close to the center. Their energy levels may shift, and the degenerated spectral lines in the bulk sample may split. Due to the appearance of numerous surface defects the crystal field in the surface of nanoparticles degenerates and the emission of 5Do→7Fj,shifts. Because the local environments surrounding Eu3+ ions near the surface are more disordered and surface defects may act as nonradiative transition channels, the width of the 579.9nm line is broader and the fluorescent lifetime becomes shorter.关键词：nanocrystalline Y2O3：Eu3+;surface defects;high-resolution spectra91|85|0更新时间：2020-08-11
- 摘要：Nitrogen-incorporated tetrahedral amorphous carbon (Ta-C(N)) films are emerging materials synthesized in the studies on the preparation of β-C3N4 films, and they are interesting materials with various applications including electrochemistry. Ta-C(N) films shown unusual durability and enhanced catalytic efficiency in some important instance over boron-doped diamond (BDD) electrodes, and their potential window.in acid media even wider than that of BDD. In particular, Ta-C(N) films can be prepared under ambient conditions whereas BDD films require high substrate temperatures (850~900℃) and the nucleation is difficult. The ambient conditions allow for a much wider range of substrates and provide a surface finish smooth on the atomic level, in contrast to the microcrystalline nature of BDD. So, Ta-C(N) is compatible to application such as microelectronics and microelectromechanical systems. Some properties such as nitrogen content, sp3/sp2 ratio and other conditions have effect on the electrochemical behavior of.Ta-C(N) films. The filtered cathodic vacuum arc deposition (FCVAP) technique is an efficient method for producing maeroparticle free and smooth Ta-C(N) films at ambient temperature. In this paper, Ta-C(N) films were synthesized on polished Si substrates at different nitrogen partial pressure with home made magnetically filtered cathodic vacuum arc deposition apparatus. In this apparatus,A curved 90~ solenoid was employed to reduce macroparticles and guide the carbon arc plasma which produced with a high-purity sintered graphite cathode into the deposition chamber, and the partial pressure of nitrogen in the chamber was controlled by the inlet of nitrogen gas through a leak valve and was monitored by an ion gauge. For investigating the effect of nitrogen partial pressure on the nitrogen content and sp3/sp2 ration, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) methods were employed. The Raman and XPS results shown that N/C atomic ratios of the films increased from 0.098 to 0.311 with rising nitrogen partial pressure in deposition chamber whereas the sp3/sp2 ratio of the films decreased, but the deposition rate decreased with rising pressure, and nitrogen atoms in the films combined with carbon atoms mainly with C=N bond.关键词：filtered cathodic vacuum arc deposition;Ta-C(N) films97|89|2更新时间：2020-08-11
- 摘要：Organic light-emitting diodes (OLEDs) with excellent performances have been reported. However, such devices are typically deposited on glass substrates because of structural or processing constraints. The use of thin flexible substrates in OLEDs allows lightweight, mechanically flexible, unbreakable emissive flat-panel displays, but the flexibility of the substrate adds much difficulty to the fabrication technology. Since the first report of flexible OLEDs, performance improvements of them are slower, and fewer researchers are involved in compared with that of glass-based devices. Advanced developments, especially the complicated effects of substrate material on the devices are required before this technology is available in commercial products. Here vacuum-deposited OLEDs based on indium tin oxide (ITO)-coated polymer substrate are demonstrated. Electroluminescent small-molecule material 8-hydroxyquinoline aluminum (Alq3) was used and complemented by the hole-transport material tetraphenyldiamine (TPD). ITO films were etched with HCl+Zn solution to stripes ～10mm and supersonic cleaned. TPD, Alq3 and Al films were deposited by heat evaporation in a base vacuum of 2×10-3 Pa. By masking each slide before Al deposition, several active areas of ～20mm2 were achieved.The light-emitting and mechanical characteristics of the devices were investigated, the influence of substrate material on ITO properties and Alq3 morphology and thus the device performance were studied, and the failure mechanisms of the devices were analyzed.As a result, the brightness of the flexible OLEDs reached 200cd/m2, which meets the need of practical display. These devices can be bent over a radius of curvature larger than 1cm without any observable changes in their characteristics. The substrate materials, the deposition methods and conditions influence ITO structure, photoelectric properties, and morphology of subsequently deposited organic films. The ITO films could deposit on polymer substrates without lattice-matching requirements, but the mismatched thermal expanding coefficients of polymer and ITO play a reverse role on the increase of brightness and stability. Also, the Alq3 morphology is sensitive to the evaporating condition, which is difficult to control. It is shown that ITO films, when pre-coated on polymer substrates with good resistance to gas, moisture and thermal expansion, provide flexible contacts suitable for OLED applications, and that optimal evaporating conditions of organic films for different substrates are necessary in order to optimize the flexible OLEDs’characteristics.关键词：organic light-emitting diode;ITO;substrate;flexibility92|91|0更新时间：2020-08-11
- Address：No.3888 Dong Nanhu Road, Changchun, Jilin, China Postal code：130033
- Tel：0431-86176862 Email：fgxbt@126.com
- Technical support is provided by Beijing Founder electronics co., LTD 吉ICP备11002662号-17
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0