最新刊期
卷 21 ， 期 3 ， 2000
- 摘要：A mono color organic light emitting diode matrix display was reported,which has been developed based on a long life green OLED cell with 96×60 pixels,an equivalent pixel size of 0.4×0.4mm2 and a designed driving circuit.A good green color image could be obtained,neither non-uniformity caused by the parasitic capacitance nor cross talk between pixels occurred.The peak luminance at the duty cycle 1/64 was 100cd/m2,and power consumption was 0.6W. The display panel consists of a glass substrate on which ITO anodes are formed in vertical stripes with a width of 0.4mm and a gap of 0.1mm by photolithography,then the buffer layer,hole transporting layer,electron transporting layers were successively deposited,Mg:Ag as a cathode was evaporated and formed in horizontal stripes with a width of 0.4mm and a gap of 0.1mm by a shadow-mask.Then the panel was encapsulated and the electrodes of the display were connected with the driving circuit. For the driving circuit,a line successive scanning and a constant current driving were adopted.It was designed to eliminate the cross-talk between the pixels,a good green color image was realized.关键词：organic thin film;electroluminescent devices;passive driven95|103|0更新时间：2020-08-11
- 摘要：Although the threshold of quantum well semiconductor lasers has been studied by various theoretical analysis,all of the results were not the simple analysis equation but some numerical value curves.In order to obtain the analysis equation,we do a farther study.In this paper,the threshold of single-quantum-well(SQW),multi-quantum-well(MQW) and separate confinement hereostructure quantum-well(SCH-SQW)semiconductor lasers were analyzed.The equation for the optical gain as a function of the injected carrier density at various temperatures for undoped quantum-well were derived.Using this result,the expressions for the threshold current density of the three quantum-well semiconductor lasers were obtained.关键词：quantum well;semiconductor lasers;threshold133|108|0更新时间：2020-08-11
- 摘要：The emission spectra of Cr4+ in 57.5%AlO1.5-35%CaO-7.5%BaO glass were measured at different temperature from 15K to 300K. The energy levels of Cr4+ in this host fall into the weak field regime on the Tanabe Sugano diagram, the lowest excited state is 3T2, and the emission spectrum is a broad band (Fig.2). The spectrum at 15K (Fig. 1) can be approximated by a Pekarian[5] g(Ezp-ptω)=e-SSP/p! By fitting the spectrum with this function we have got Ezp=8400±13cm-1, ω=320±5cm-1, S= 3.58±0.08. Strictly speaking, the spectrum should be the convolution of the phonon sideband and an inhomogeneous lineshape, which is usually expressed by a Gaussian. By calculating the convolution and comparing with Fig.1, we estimated that the inhomogeneous line width is within 300~400cm-1 (FWHM). The emission band widths obtained from Fig.2 are shown in Fig.3 as solid cycles. According to the single frequency approximation, its temperature dependence would be[5] D=D0[1+e-tω/kT/1-e-tω/kT]1/2=D0coth1/2[tω/kT], where D0 is the band width at 0K. With the parameters obtained above, D should be as shown by the solid line in Fig.3 (labeled by ωV/ωU=1). Evidently, it does not agree with the experimental result. The temperature dependence of the width of the phonon sideband originates from the thermal excitation of higher vibronic states. Transition from these states covers larger energy range. If the high vibrational states coupled to the excited electronic state are less populated, the temperature dependence of the bandshape would be weaker. This will happen if the phonon coupled to the excited electronic state possesses energy larger than that coupled to the ground state. Thus it makes us apply the model where the ground state and the excited state couple unequal frequency phonons[6]. Keeping S, Ezp and ηωU obtained from the single frequency approximation fitting and taking ωV/ωU as a new parameter, we calculated the temperature dependence of the emission bandwidths. The calculated results are shown in Fig.3, ωV/ωU=1.15 results in the best fitting.关键词：Cr4+ ions;phonon sideband;single frequency approximation;unequal force constants model115|109|0更新时间：2020-08-11
- 摘要：Cubic lead fluoride(β-PbF2) crystal is known as an excellent Cherenkov radiator with a radiation length of less than 1 centimeter. It is also a very attractive material for use as a scintillator because of its high density. Unfortunately no luminescence has been detected at room temperature so far. Its luminescence existing at liquid helium temperature is rapidly quenched upon raising the temperature. Someone proposed that the luminescence of crystal is hidden as a consequence of the too high local symmetry of the Pb2+: ions in the fluorite lattice. In order to try to break this local symmetry, a few of cation ions, such as turbium, were doped into β-PbF2 crystal to replace the Pb2+: ions. In this experiment, TbF3 was used as a dopant.β-PbF2 crystals doped with Tb3+ ions (β-PbF2:Tb) were grown with a non vacuum Bridgman method employing resistive heating system. The dopant concentration varies from 0.008 to 0.6 at%. The crucible charged with raw materials and trace deoxidant were heated to the temperature over the melting point of lead fluoride and then lowered at the rate of 1mm/cm. The grown crystal ingots were colorless and transparent. They were cut and polished to make a sample with the size of Φ25×25mm for various test. Their absorption and emission spectra excited by X-ray and UV were measured at room temperature respectively. It was found that there are seven absorption bands peaked at 283, 303, 318, 340, 352, 368 and 377nm and their absorption intensity increase with the dopant amount of Tb3+ ions from 0.1% to 0.4%(at.). The optical absorption of β-PbF2:Tb crystals on the UV light is corresponded to 4f-4f transition of Tb3+ ions. There are nine emission peaks with wavelength of 382, 416, 437, 468, 489, 545 and 620nm in the emission spectra excited by X-ray. It is suggested that these emission peaks result from the transition of 5D3→7FJ and 5D4→7FJ (J =6,5,4,3,2), respectively. When the dopant concentration is less than 0.2at.%, the emission from 5D3→7FJ is dominating, otherwise, the emission from 5D4→7FJ is dominating. In the identical doping crystal, the fluorescence intensity decreases from the bottom to the top of the crystal. It behaves like that the segregation coefficient of Tb3+ ion in β-PbF2 crystal is greater than 1. The emission and excitation spectra excited by UV light were recorded by PERKIN ELMER LS50B fluorescence spectrophotometer. Four emission peaks with wavelength at 382, 415, 437 and 545nm were identified in the emission spectra and were ascribed to the transition of 5D3→7FJ(J=6, 5, 4)and 5D4→7FJ,respectively. Tb3+ ions in β-PbF2:Tb crystals are suggested to take the position of Pb2+: ions and the charge deficiency could be compensated by the formation of interstitial fluorine ions.关键词：lead fluoride;turbium ion;doping;fluorescence86|98|1更新时间：2020-08-11
- 摘要：Luminescence of Er in hydrogenated amorphous silicon film is promising for its potential application in optoelectronics. We investigated the influence of some light elements on the luminescence of Er in silicon based materials. O, B, P doped hydrogenated amorphous silicon films are fabricated via plasma enhanced chemical vapor deposition technique. XPS analysis indicated the ratio of Si and O contents in the film is 1:1. After room-temperature erbium implantation and rapid thermal annealing in N2 ambient,photoluminescence (PL) of Er was measured. At room temperature strong PL of 1.54μm peak was observed. Oxygen has a great enhancement function on Er photoluminescence and B or P co-doped with O further enhances PL intensity of Er. Rapid thermal annealing experiments indicated that the incorporation of three elements compensated the defects of the films, improved the thermal stability and enhanced the escaping temperature of H. The annealing temperature corresponding to the optimum PL intensity increased by 100℃, respectively, in three different kinds of samples. We attributed this phenomenon to the incorporation of O, B and P. The presence of oxygen with erbium formed optically active [Er-O] complexes which greatly enhanced PL intensity. Also the excitation mechanism of Er was discussed.关键词：Er;O;B;P;luminescence;hydrogenated amorphous silicon97|309|1更新时间：2020-08-11
- 摘要：Multi-layer GaP wafers with different luminescence efficiency were investigated using microscopical optical methods. According to an interaction between the free carrier plasma and on the longitudinal optical lattice vibrations via their microscopical electric fields in GaP, an mixed plasmon-phonon character is appeared. The carrier distribution has been determined from the fitting of the theoretical line shape to the observed spectra of the plasmon-LO-phonon coupled modes in the cross section of GaP diodes. The optical determination of electrical parameters has some advantages, it is not necessary to contact sample and the spatial resolution amounts to about 1 μm. The obtained results are in good agreement with those of electrical measurements. We have performed a synchronistic measurement in the cross section of GaP wafer by microscopical photoluminescence. The experiment demonstrates that there are different deep levels and red emissions in GaP substrate and p layer. The deep level in p local area has an obvious influence on PL intensity-distance curve and on the luminescence efficiency. Therefore, it is important to improve red emission and to control deep level from growth condition. The result showed that the carrier distribution obtained from microscopical Raman spectra is related to the curve of PL intensity-distance using microscopical photoluminescence. They argee reasonably with the distribution of doped impurities and existent defects in GaP substrate and epitaxial layers. It comes to the conclusion that the scanning Raman and photoluminescence technique is a powerful tool for the characterizations of GaP epitaxial layers as well as the diagnostics of LED devices.关键词：microscopical photoluminescence;Raman scattering91|137|1更新时间：2020-08-11
- 摘要：The revised disorder induced scattering theory mode was applied to analyze the effect of Raman coupling coefficient on Raman scattering in glass ceramics(PbF2+WO3+GeO2(PWG)).Although the Raman coefficient is generally attributed to be frequency-dependent,it is formally the Fourier component of the spatial correlation function.The Raman coupling coefficient is therefore rigorously momentum (wavevector)dependent,thus describe the momentum conserving interactions occurring within a glass ceramics materials during an Raman scattering process.Analysis of the spectral distribution curves for thermally active vibrational states in PWG showed the coupling coefficient to be qualitatively represented by the inclusion of an exponential decay dependence.The sum of a harmonic potential and the spatial correlation function(interaction potential)associated with the coupling coefficient is shown to yield a distorted harmonic closely resembling an asymmetric double well potential.The relevance of this combined potential is discussed with respect to relaxational mode behavior.关键词：glass ceramics;Raman scattering;coupling coefficient97|130|0更新时间：2020-08-11
- 摘要：In many hosts, Eu3+ can be a fluorescent probe to detect local symmetry and microstructure of rare earth ions in a crystal. (La1-xEux)(BO2)3 has been synthesized by solid state reaction at high temperature, and this paper is to establish the relationship between the spectra of Eu3+ and the crystal structure of (La1-xEux)(BO2)3. The polycondensation of [BO3] units has been analyzed from infrared spectra, and the results suggests the negative ion units are polymerized into chain structure such as (BO2)nn-, among which La3+ and Eu3+ are scattered. The crystal structure has been investigated using X-ray powder diffraction, which indicates the sample is monoclinic, with space group being I2/a. According to the crystal structure and emission spectra of La(BO2)3:Eu3+, the relationship between the luminescent properties and the site symmetry of Eu3+ in La(BO2)3 has been discussed in detail. For space group I2/a, the symmetrically equivalent points of 4a, 4b, 4c and 4d positions have inverse centers, so their site symmetry is Ci,but there is no inverse center for 4e and 8f position,and their site symmetries are C1 and C2 respectively. In La(BO2)3:Eu3+ system, 5D0→7F0 transition does not exist, moreover, the emission corresponding to 5D0→7F1 transition is much more intense than that of 5D0→7F2 transition, so the Eu3+ must be located at the site of Ci symmetry, and the 5D0→7F2, 7F3 and 7F4 transitions are attributed to a little part of Eu3+ deviated from inverse centers. In addition, it has been confirmed that adding a certain flux may be of great advantage for the sample to be well crystallized and for Eu3+ to be located at a site of perfect Ci symmetry so that 590nm emission corresponding to 5D0→7F1 transition is greatly intensified. On the other hand, the reason that Eu3+ gives very intense emission nearby 697nm corresponding to 5D0→7F4 transition need to be further investigated.关键词：La(BO2)3：Eu3+;luminescent properties;crystal structure86|97|0更新时间：2020-08-11
- 摘要：Several decades for the studies on luminescence materials doped with rare earth ions were past.The rare earth ions doped inorganic materials have been extensively applied to many fields, such as display techniques,laser medium,and fiber comunication.Most of the rare earth ions were used commercially,like Nd3+,Er3+,Ce3+,and so on.The intense transitions of Tm3+ are at blue and infrared domain,they are fitting for source of high densities optical storage and infrared communication.For this reason,the blue and infrared emissions are very important and attract many researchers to investigate.Glass materials have different characters with crystals.Glass materials are plastic so that they can be fabricated into fiber.Furthermore, the doping concentration of rare earth ions in glasses can be adjusted in broad range.Therefore,doping Tm3+ in glass materials is very important to application. Ten gram batches of Tm3+ doped tellurate glasses 50TeO2-10AlF3-(20-x/2)PbF2-10BaF2-10NaF-x/2Tm2O3(x=0 2,1 6,2,3,4)were weighed and melted in crucibles at 800℃ for 10min.The resulting glass rods were cut and polished for spectra experiments. The absorption spectra was measured by commercial electroform as light source with D330 spectrometer and R955 photomultipler tube,the signals were connected to XY plotter.The emission spectra and the fluorescence decay under 355nm excitation were measured with SPEX-1403 double grating spectrometer,and the raw data was collected and saved by PC. The intensity parameters of Ω2=2.83×10-20(cm2),Ω4=3.21×10-20(cm2),Ω6=3.96×10-20(cm2) were obtained from the J-O calculation results based on the absorption spectra. The experimental result of fluorescence decay of Tm3+ for different concentration samples shows that,the fluorescence decay constant of 1D2-3H4 and 1G4-3H6 transitions decreased with the increasing of Tm3+ concentration.The experimental results were coincided with Dexiter's theory about cross relaxation energy transfer.The relationship between fluorescence quantum efficiency of 1D2 and 1G4 and the concentration of Tm3+ in MFT glasses was discussed.The transfer rate between Tm3+ ions was calculated for sample with 4% Tm3+.We conclude that the cross relaxation luminescence quenches for 1D2 of Tm3+ was induced by dipole dipole interactions.关键词：J-O theory;quantum efficiency;transfer efficiency;fluorescence decay79|173|1更新时间：2020-08-11
- 摘要：Photosynthetic bacteria (PBS) is a special kind of microbe, it is not only as a good kind of material which has been studied in photosynthesis, but also it has been applied to the treatment of high concentration's organic waste water and a fodder additive in the aquatic breeding. Recently a few active strains which are nontoxic for human being, may be used in health field because it has been discovered some physiologic activities such as anti-radiation,the regulation of immunity etc. For proving the effect of PBS on inhibiting lipid-peroxidation, two typical systems were measured by using the method of chemiluminescence. The system Ⅰ that was imitated easy oxidative components of membrane of cell were constituted by BSA-linoleic acid-Fe2+. The chemical structure of linoleic acid molecule has some dual-binding between carbon atoms. The structure can be oxided easily. BSA (bovine serum albumin) also has same character. The existence of Fe2+ promoted the process of lipid-oxidation. Luminol was added into system Ⅰ for raising sensitive degree. The autoxidation of components in system Ⅰ would cause low-level bioluminescence. The value of the bioluminescence can be measured by the instrument of bio-chemiluminescence (Model GSH-1) and represent the strength of lipid-oxidation. In the system Ⅱ, it was constituted by mouse brain-homogenate and Fe2+. The brain homogenate contains rich lipid and poly-unsaturated fatty acid, which initiate the process of lipid-oxidation easily with the existence of Fe2+. The strength of the autoxidation was measured by the same method. The culture of the active photosynthetic bacteria No.1 strain was centrifuged into two parts: the cell of bacteria and the supernatant liquid. In the system Ⅰ the rate of inhibiting on the lipid-peroxidation was 13.4% for the undiluted supernatant liquid. It was 56.4% for suspended cell when the concentration of cell was 5mg/L. The effecting function was stronger with the increasing of cell concentration. In the system Ⅱ the rate of inhibition was 10.2% for the undiluted supernatant liquid. However it already reached 74.1% when the concentration of cell was only 5μg/L. It was stronger than that in the system Ⅰ. In an alkali condition triphenoliclog can release superoxide anion. Moreover it initiated successive reactions and caused an autoxidation. In the autoxidation process the value of curve's slant rate(K) presents the rate of the autoxidation. The result showed the suspended cell has the function of inhibiting on the autoxidation obviously. When the concentration of cell was 250mg/L, K reduced to 0.47 as compared with that K equals 1.33 under contrast condition. It has also proved that PSB has a good effect on quenching super oxide anion. In order to discover new microbiological resource and provide a basis of the theory for PSB applied as a new healthy product, we explored the anti-oxidative function from two associated aspects about inhibiting lipid-peroxidation and quenching superoxide anion.关键词：photosynthetic bacteria;lipid-peroxidation;chemiluminescence;super-oxide anion98|277|7更新时间：2020-08-11
- 摘要：To improve the characters of organic light emitting diodes (OLEDs), the mechanism of electroluminescence processes has been studied extensively, but due to the complexity of mathematics and experiments, most of them have not been solved. In this paper we try to solve this problem by adding the injection and the recombination of carries to a model which H.Bassler and co-workers have proposed. Using Monte-Carlo method we simulated the injection, transport, and recombination of carriers in the OLEDs, and we obtained the time-dependent diffusion coefficient of δ electronic pulse, then we extended the diffusion coefficient of δ electronic pulse to the diffusion coefficient of direct current. The relationship between diffusion coefficient, electric field and standard deviation of density of states (σ) was obtained. We found that relationship between diffusion coefficient and electric field is non-linear, and it lies on the magnitude of standard deviation of density of states (σ). With increasing σ,the variance of diffusion coefficient changing with electric field became much greater. If taking into account the recombination type: Langevein type, r=4π<R>(D++D-) at the same time, we can get the relationship between recombination coefficient and electric field. Then we discussed the spectrum deforming with electronic field of ITO/ROPPV(60nm)/Alq(40nm)/Al structure. In our simulation, it is the standard deviation of density of states (σ) that controls the variance magnitude. The standard deviation of density of states (σ) tells disorder degree of samples and can be adjusted by changing the temperature of substrate and growing velocity in developing sample. In fact the reason influencing the deformation of spectrum is the relative magnitude of σ,so if we find a way to diminish σ, we can decrease the variance of recombination coefficient. But it also decreases the magnitude of mobility and decreases the luminescence efficiency. There exists a best σ value improving the characters of OLEDs. With this method, we have a new way to design the OLEDs.关键词：Monte-Carlo simulation;diffusion coefficient;organic light emitting diodes94|165|0更新时间：2020-08-11
- 摘要：Organic/polymeric electroluminescence (EL) has attracted much attention due to its potential applications in large-area full-color flat-panel displays. Since the first report of high performance double-layer organic light-emitting device by C.W. Tang in 1987, much progress has been made in this field. A lot of novel materials have been synthesized. So it becomes very important to characterize and evaluate the properties of these materials. Study on the energy band structure of organic/polymer materials is very significant. It can give directions in materials design and synthesis, devices design and fabrication, and device properties improvement. In this work, we focus on the characterization and analysis of the energy band structure of more than one hundred kinds of organic/polymer EL materials by cyclic voltammetry and UV-Vis spectra method. The materials include a series of π-conjugated rigid rod phenylene vinylene (PPV) oligomers, pyrazoline derivatives system, bipyridine ruthenium complexes system, rhenium complexes system and some other materials(including EL materials and carrier transporting materials) in common use. Based on the principle of energy level matching, a series of organic EL device were designed and fabricated. The result shows that a good performance device can be obtained by considering the energy band matching, the thickness matching, as well as the carrier mobility matching.关键词：electroluminescence;energy band structure;energy band matching107|81|4更新时间：2020-08-11
- 摘要：The developments in rare earth organic/polymer electroluminescence(EL)were described.Since the studies of RE-OEL were reported in 1990 by Kido et al,the study in this field has made a progress rapidly.In our group,the studies on organic/polymer EL-based on RE complexes,such as white electroluminescence based on Dy-complex and Eu-Tb double nuclear complexes,Eu-red electroluminescence with higher efficiency and long lifetime were carried out,and phenomena of electronic transition from 5D0-7F1 at 596nm of a new EL based on Eu-polymer complex were observed.The efficiency and durability of OEL devices based on Eu complex improved intensively,and the efficiency is about 4.6% which exceeded the theoretical limit,and the lifetime(the decaying time from 100cd/m2 to 50cd/m2)is the highest so far.Either blue EL or IR EL emissions based on Tm-complexes could be observed when the ligand changed.On the other hand,new IR emission and I-V characteristics of OEL devices based on Yb,Er and Nb-complexes were studied too.Finally some problems existed in RE OEL were discussed in which the luminance and durability should be improved,and new RE-complexes with stable structure and good film forming properties must be carried out.The foreground for color displays is prospected.关键词：rare earth;polymer;organic electroluminescence94|93|3更新时间：2020-08-11
- 摘要：Organic electroluminescent devices (OLEDs) have been intensively investigated since the first efficient device was demonstrated.Although there are some studies about the dependence of the performance of OELDs on the morphologies and structures of organic thin films,similar studies on Alq3 have not been reported.In this paper,organic electroluminescent devices with a structure of ITO/Poly (9-vinylcarbazole)/tris(8-hydroxyquinoline)aluminum(Alq3)/Mg:Ag are fabricated at different substrate temperature(77K,298K,and 438K)during Alq3 deposition.It is found that the surface morphologies of Alq3 thin films greatly affect the I-V characteristics of the devices by the contact area between metal cathode and light-emitting layer.The more uniform Alq3 film is the larger contact area is,and the greater current is obtained.There is a decrease in the uniformity and smoothness of the Alq3 thin films on PVK films in the order of S298>S438>S77.Accordingly,at the same bias voltage,current through the device increases in the order of I77<I438<I298.There is a increase in the quantum efficiencies of the devices in the order of η77<η438<η298.We attribute this to different structures of Alq3 thin films.It is confirmed by transmission electron microscopy that the film deposited at 77K consists of polycrystalline grains,and the ones deposited at 298K and 438K are both amorphous.Crystallization can induces lower quantum efficiency than the glassy state does,which answers for the lowest quantum efficiency obtained at 77K. Despite the same glassy state,the quantum efficiency of the film deposited at 438K is higher than that of the film deposited at 298K, which results from the reduction of impurities and defects in the film deposited at 438K.Additionally,photoluminescence measurements testify that there is a increase in photoluminescence efficiencies of Alq3 films on quartz substrates in the order of E77<E298<E438, which is consistent with the above conclusions.In summary,by controlling the morphology and structure of Alq3 film,we can not only improve the quantum efficiency of device,but also reduce the current of device(equal to reduce Joule heat).Hence,it is a new method to improve the performance of device:controlling the condensation state of organic film by substrate temperature.关键词：substrate temperature;morphology and structure;quantum efficiency;current density101|85|2更新时间：2020-08-11
- 摘要：In order to compare the stability between small molecule light-emitting materials and polymer light-emitting materials,tris-(8-hydroxyquinoline)aluminum (Alq)(a typical small molecule light-emitting material)and poly(9,9-dioctylfluorene)(PFO)(a brand new polymer light-emitting material)were chosen as study cases in this work.Ultraviolet photoelectron spectroscopy(UPS),X-ray photoelectron spectroscopy(XPS),atomic force microscopy(AFM), and photoluminescence spectrometer(PL) were used to investigate the ambient effect on the electronic structures,surface morphology,and PL properties of the Alq film and the PFO film. Alq films, with thicknesses of 6~8nm, were deposited by the thermal evaporation on to either Si substrates or indium tin oxide (ITO) coated glass substrates in a deposition chamber attached to a VG ESCALAB 220i-XL photoelectron spectroscopy system. PFO was spin coated from a toluene solution (1 5wt%) to form the films with thicknesses of 7~15nm on Au coated Si substrates or on ITO coated glass substrates. After first time measurements, the freshly prepared samples were put into air for storage at room temperature for further measurements. The relative humidity during storage was 60~70%, and the storage duration was from 1 hour to 28 days. We used the He Ⅱ excitation line(40.8eV) from a He discharge lamp for the UPS measurements and a monochromatised Al Kα excitation line(1486.6eV) for the XPS measurements. A clean Au film on Si substrate was used for the Fermi level (EF) and the binding energy calibration. Surface morphologies of the films were observed in air by Scientific Auto probe CP AFM. The PL properties of the films were obtained by Perkin Elmer LS-50B Luminescence Spectrometer. UPS results indicated that the electronic structure of Alq film were obviously changed upon 1-hour exposure to air while that of PFO film was slowly changed with increasing the storage time up to 28 days,but this change was hardly discernible after 1-week storage in air.XPS results indicated that Al bonding and N bonding in Alq molecule were easily influenced by H2O and O2 while C-C bonding in PFO was not easily attacked by H2O and O2.AFM revealed that the surface morphology of Alq film was also obviously changed after exposure to air but that of PFO film remained basically unchanged.The PL peak intenstity of Alq film was quenched rapidly in the air while that of PFO film was decreased much slowly.Therefore,PFO is a rather stable light-emitting material used in polymer light-emitting devices.关键词：organic light-emitting materials;stability;electronic structures;surface morphology;photoluminescence properties100|76|2更新时间：2020-08-11
- 摘要：Organic electroluminescent (EL) devices have attracted much attention because of their high potential for full-color large-area flat panel display applications. One of the important steps for full color displays is the realization of red electroluminescence (EL). Porphyrin compounds have many derivatives that have various molecular structure and electronic states,including PtOEP,TPP,ZnTPP ect.,which were used for red-emitting materials.In this paper,a new compound 2,3,7,8,12,13,17,18-octaethyl-21H23H-porpine zinc (ZnOEP) was proposed for red electroluminescence. Organic EL devices with ZnOEP as a dopant at various concentrations within a tris (8-hydroxyquinoline) aluminum (Alq3) host layer were prepared by conventional vapor deposition. The multi layer structure of the devices is ITO/TPD/ZnOEP:Alq3/Alq3/Mg:Ag.For deposition of the ZnOEP:Alq3 layer,the evaporation rates for the ZnOEP dopant and the Alq3 host were independently controlled by separate thin film deposition monitor.The dopant concentrations in the Alq3 were 0.5,2,10 and 15wt%,respectively. EL spectra, B-J curves and pulse response characteristics of the devices were measured. It was found that EL spectra and B-J curves were significantly different as the dopant concentration varied.In the spectra of all the devices,there were two peaks at about 590nm and 630nm,which were originate from ZnOEP molecular excitons.It is observed that the peak at 590nm becomes weaker when the ZnOEP dopant concentration increases and the emission color turns from orange to red, while the luminance efficiency drops from 0.96cd/A to 0.14cd/A.The experimental results may be explained by the following two factors:the self absorption of ZnOEP and the phenomena of concentrated quenching. Additionally, response time characteristics were obtained by measuring the EL light waveforms while using rectangular voltage pulses of 100μs duration. The pulse response characteristic of the device may indicate the existence of the energy transfer between the Alq3 and the ZnOEP molecules. In conclusion,it is the first time to get electroluminescence from ZnOEP:Alq3 system in this paper.The EL spectra of the devices changed with the ZnOEP dopant concentration due to the self absorption of ZnOEP and the phenomena of concentrated quenching.When the ZnOEP dopant concentration is over 10%,red electroluminescence was obtained.In additional,the pulse response characteristics of the devices were investigated,too.关键词：electroluminescence;dopant;ZnOEP103|80|3更新时间：2020-08-11
- 摘要：After the first report of a bright green light organic electroluminescent(EL) device by Tang and Van Slyke,intensive research efforts have been made to realize other emission colors. Various emission colors,including blue,green,red and white,can be obtained at high luminance levels,which promises the application of these devices to flat panel full color displays.Among them,white light emission is very important for applying organic EL devices to full display,backlight and illumination light source.Owing to the lack of the single active material,which emits white light,several fluorescent dyes with different emission colors should be used to generate white light.Therefore,it is necessary to develop special device structures for this purpose. This work have developed a high brightness and efficiency white light devices.The device structure of ITO/poly(N-vinylcarbazole)(PVK)/1,1,4,4-tetraphenyl 1,1,3-butadiene(TPB)/aluminum complex(Alq)doped with rubrene/Alq/Mg/Al was employed.The turn-on voltage is as low as 2.5V.Blue fluorescent TPB,orange fluorescent rubrene,and green fluorescent Alq are used as three primary colors.The Commission Internationale de 1′E clairage(C.I.E)coordinates of the emitted light are (x=0.319,y=0.332)at 10V,which is located in the white light region.Bright white-light,over 20000cd/m2,was successfully obtained,and the maximum efficiency reaches to 1.24lm/W at 9V. In this paper,the structure of the white-light-emitting device belongs to common multilayer structures,but at present the brightness and efficiency of the device was in the lead in international reported white light-emitting devices.The reason the author considered probably are as follows:polymer PVK acts as hole transport layer,the thick PVK layer(200nm)can not only reduce the amount of pinhole of the film, enhance the evenness of the film,but also reduce hole current,namely majority current,which benefit to charge carrier injection balance and improve the formation probability of exciton,and at the same time,the thick PVK layer can depress the jouleheat made by largger current,bring down the effect of heat on fluorescence efficiency of organic material,which also benefit to achieving high-performance devices.关键词：hole;organic/polymer;electroluminescence82|85|1更新时间：2020-08-11
- 摘要：Due to the excellent properties such as lightness,good transparency,impact resistance,processability,and dyeability,optical resins were extending their application as transparent materials replacing inorganic optical materials in wide fields.Rare earth compleses with organic ligands,especially those containing Er3+ and Tb3+,often exhibit efficient luminescence such as high luminous intensity,long luminous lifetime and sharp line spectrum. Though rare earth complexes assumed sound luminescence performance,but the stability was different,as a result,its application was restraint.If rare earth complexes were recombined into a range of suitable cuchion substance,the cushion substance can provied relatively stable environment for the rare earth complexes,which is good to exihbit the luminescent characteristic of the rare earth complexes.Furthermore,the rare earth complexes can offer the cushion substance novel function. According to the principle of molecular design,when introducing rare earth ion into the optical resin,the transparent polymer with luminescent properties could be prepared.In our knowledge,this research has rarely been seen before and is terrifically significantly. In this paper,the rare earth complexes were combined into optical resins,and the resins that possess high transparency and good luminescent properties were obtained,their optical properties were studied.In addition,the relationships between the transparency luminescent properties of the polymer and the content of the components in the copolymer system were investigated.135|93|9更新时间：2020-08-11
- 摘要：Since the discovery of efficient organic light-emitting devices (OLEDs), there has been considerable interest in developing OLEDs with high brightness, high efficiency, and long lifetime for display applications. This has resulted in substantial research activity to increase the carrier mobility, color gamut, and electroluminescence efficiency of organic materials, as well as to improve electron and hole injection by the contacts. The brightness and efficiency of OLEDs depend on the number density of electrons and holes in the emission layer, so that effective charge injection into the organic materials is critical for optimum device performance. For the hole injecting contact, indium tin oxide (ITO) is often used because of its transparency and high work function (5.1eV). On the other hand, an efficient electron-injecting contact is usually a low work function material such as magnesium, calcium, or lithium. These materials are typically alloyed with metal such as aluminum or silver to form contact that is both more stable and more resistant to corrosion upon exposure to air. At the same time inserting an insulating layer between cathode and organic material is effective means to improve current injection and EL. In this paper, some multilayers OLEDs were fabricated using Al,LiF/Al and Mg:Ag as cathode respectively while ITO-coated glass as anode, 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene(PPCP) as emitter, N,N′-diphenyl-N,N′-bis(3-methyl-phenyl)-(1,1′-biphenyl)-4,4′-diamine(TPD) as hole-transport layer, tris(8-hydroxyquinoline)aluminum(Alq), 2-(4-biphenylyl)-5-(4-tertbutyl-phenyl)-1,3,3-oxadiazole(PBD) or 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene(BBOT) as electron-transport layer, respectively. And effect of cathode on performance of blue OLEDs was studied. All organic layers were prepared by a high vacuum multisource type organic molecular deposition system. From result, it is found that the performance of device with LiF/Al as cathode excels that of the device with Al or Mg:Ag as cathode. Devices with LiF/Al show better I-V characteristics and higher EL efficiency. The presence of LiF at the metal-organic material interface cause band bending of organic material, thus lower the electron-injection barrier height.关键词：electrode;blue OLED;LiF104|200|0更新时间：2020-08-11
- 摘要：Unique luminescent properties of rare earth ions in inorganic and organic matrices have been the subject of many studies for many years, including both photoluminescence and electroluminescence. The Er3+ ion has a sharp luminescence centered at 1530nm due to an intra-4f shell transition between the first excited state (4I13/2) and the ground state (4I15/2). Considering the potential use of trivalent erbium complexes as IR emitting materials for optical quartz fiber communication and laser application, we concentrated in organic electroluminescence (EL) from Er3+ in IR range. Except for notable advantages of current excitation over photo excitation, probability of realizing electric pump laser from Er3+, which is a usual emitting center in inorganic laser crystals and glasses, is another attractive purpose of this study. Er(DBM)3bath and several kinds of other Er-complexes were synthesized according to traditional method in our lab. Bilayer and trilayer EL devices based on Er(DBM)3bath were fabricated. Two intense bands at 1530nm and 977nm originated from trivalent Er3+ ion were observed under a low DC voltage for the first time. Individual organic films and alloy cathode of EL devices were deposited onto indium tin oxide glass substrate successively by thermal evaporation in a vacuum chamber at 5×10-4 Pa. The made up devices were encapsulated in dried nitrogen. IR(700~2000nm) and visible (400~750nm) spectra were measured by a Biorad PL-9000FT spectrometer and a Hitach-4000 fluorescence spectrophotometer at room temperature, respectively. From ITO/TPD(30nm)/Er(DBM)3bath doped TPD(30nm) (about 1:1)/Er(DBM)3bath(60nm)/Mg:Ag(150nm) (device I), intense emitting band locating at 1530 nm corresponding to 4I13/2→4I15/2 transitions of Er3+ was observed. Almost pure emissions from Er3+ were obtained including a weaker peak at 977nm, which was originated from 4I11/2→4I15/2 transition. IR emissions were accompanied by visible emitting for both bilayer and trilayer devices. Emitting spectra of the two types of devices were quite different. This indicates that radiative decay of the lowest excited state of ligand occurred through not only f-f transition of Er3+ ion but also other ways.关键词：infrared emission;organic electroluminescence;Er-complex85|188|3更新时间：2020-08-11
- 摘要：Self-focus medium-liquid crystal was placed between two BK7 glass plates,and the grating with the triangle groove was caved on the internal surface of one of glass plates for making nonlinear modulation grating.An Ar ion laser beam with 5145nm wavelength was irradiated perpendicularly to the grating surface and was focused on the liquid crystal.The diffractive angle of the laser beam was depended on the grating period.The intensity of 0-order beam was depended on the depth of the grating groove.Because the liquid crystal is self focus medium,the increasing of laser power density focused on the liquid crystal can change the refractive index difference between the liquid crystal and BK7 glass plate.Under a specified value of the laser power,it was obtained by experiment that the laser power density focused on the liquid crystal was 0.5kW/cm2,the refractive index difference between the liquid crystal and BK7 glass plate was nearly equal to 0.As a result,the grating in this structure was covered,the various diffracted orders of the transmitting sample almost disappeared,only 0-order beam was left;deviating from this value,the grating reappeared,the various diffracted orders appeared immediately,0-roder beam was weakened.This modulation effect is on physical basis for adaptive optical limiting of the nonlinear grating.The effect of the adaptive optical limiting has the features of large bandwidth and high speed optical limiting.So it has important application prospects in tunable protection of lasers.关键词：optical limiting;self-modulation;nonlinear grating108|172|1更新时间：2020-08-11
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