最新刊期
卷 21 ， 期 1 ， 2000
- 摘要：Ⅱ-Ⅵ semiconductor heterostructures have been extensively studied in the past several years due to their potential applications in blue and blue-green optoelectronic devices. The use of these structures in light emission diode and laser diode requires the applications of an electric field to provide carriers for recombination-based optical processes. But the existence of electric field also influences the optical properties of these structures. In this paper, the investigation of the effect of electric field on the electro-modulated reflectance (ER)spectra energy and intensity of ZnCdSe-ZnSe superlattices was described. The variation of ER spectra under different bias at room temperature is studied for the first time. In the range of the weak electric field, the intensity of the ER spectra increase with increasing the electric field, but the lineshape is almost not affected. In the range of strong electric field, the lineshape of the ER spectra vary with increasing the electric field, and the transition energy shows a red shift. The forbidden transition emerges under certain field intensity, and its intensity increases quickly with increasing the field intensity, these effects are attributed to the quantum confined stark effect (QCSE). The ER spectra of compound superlattice with different potential barrier heights under different bias voltages indicate that the excitons are more easily affected than the superlattice with lower confining energy. The results are useful for the design of ZnSe/based optoelectronic devices.关键词：Zn1-xCdxSe-ZnSe superlattices;electro modulated reflectance spectra;electro optical modulation81|78|0更新时间：2020-08-11
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Effect of Substrate Temperature on the Epilayer Quality of ZnS Grown on the Si Substrate by LP-MOCVD
摘要：ZnS has been of great interest for optoelectronic development as a potential light emitting material. Most Ⅱ-Ⅵ compounds have been grown on GaAs substrates. However silicon is the most important semiconductor for electronic industry because of its availability in large-area wafer with excellent quality and low cost, and silicon-based devices are so highly developed. In this work, the ZnS epilayers directly grown on (111) Si substrates have been successfully obtained at lower temperature (300～400℃) by low-pressure metalorganic chemical vapor deposition (LP MOCVD). The growth of ZnS on Si substrates has been investigated primarily by X-ray diffraction. The Si substrates were degreased in organic solutions and cleaned using 1HNO3:1H2SO4 solution and 3HCl:1H2O2:1H2O solution, then etched with HF solution to remove the native oxide layer, then immediately flushed with N2 gas and loaded into the reactor. No high temperature preheat treatment of the Si substrates was used to obtain ZnS in this work. The two-step growth method with changing Ⅱ/Ⅵ flow rate was used to obtain ZnS epilayers on Si substrates. The growth mechanism was discussed. A thin amorphous or an unstable crystal structure was deposited at a lower Ⅱ/Ⅵ flow rate for the first layer. The subsequent step was done at a higher and optimum growth Ⅱ/Ⅵ flow rate. The Zn and S atoms would rearrange themselves through a solid-phase epitaxial process in which the relatively lattice-matched regions may act as seeds for subsequent single-crystal growth. The X-ray diffraction spectra of ZnS epilayers show that the epilayer qualityincreases with decreasing the growth temperature. The crystallinity was further investigated in terms of the X-ray FWHM (full width at half maximum) of ZnS epilayers. The FWHM decreases with decreasing growth temperature. The lowest FWHM of ZnS epilayer grown at 300℃ on Si by the two-step method of changing Ⅱ/Ⅵ flow rate is 540 arc·sec.关键词：ZnS epilayer;Si substrate;LP-MOCVD86|105|0更新时间：2020-08-11 - 摘要：Temperature dependence of the effective mass of the strong coupling magnetopolaron in polar crystals are studied by means of an improved linear combination operator method. The temperature characteristic of the effective mass are discussed in detail at different approximation calculation level. The result illustrates that the different approximation calculation level can provided two completely contrary conclusions on temperature dependence of the effective mass of the magnetopolaron.关键词：different approximation level;strong coupling;magnetopolaron;effective mass;temperature characteristic116|98|1更新时间：2020-08-11
- 摘要：Microcavity lasers have been attracting much more attention recently. Microdisk lasers represent a novel class among them. The disk thickness is typically only a half of an optical wavelength in the materials. Whispering gallery modes near the disk edge account for the low loss resonator modes. InGaAs/InGaAsP MQW microdisk lasers based on this disk resonator were fabricated by using standard photolithography, reactive ion etching (RIE) and wet chemical etching. The MQW materials were grown on InP substrates by gas source MBE technique. The diameters of the disk laser we had made were 8μm, 4.5μm and 2μm, respectively. The optical properties of the disk were characterized by optical pumping at liquid nitrogen temperature. The lasing threshold of the disk with a diameter of 2μm was only about 3μW when pumped by 514.5nm line of Ar ion laser. To our knowledge, this threshold of 3μW is the lowest one up to now. Multiple mode lasing, mode chirping and output saturation were investigated when pumped at high optical pump density. It was observed that the structure of the photoluminescence spectra became sophisticated with increasing the pump power. New lasing peaks appeared and became dominated in the spectra. It was also observed that the intensity of lasing lines became saturated with increasing the pump power. The linewidth of lasing peak was of the order of about 1.3nm. It was also observed that microdisk lasers showed anomalous linewidth behavior compared with ordinary semiconductor laser. This characteristic was usually explained with many-body effect induced by the non equilibrium carrier distribution when optically pumped.关键词：microdisk;microcavity laser;lasing101|71|0更新时间：2020-08-11
- 摘要：The photoluminescence (PL) in directly Be doped self organized InAs quantum dots (QDs) grown by molecular beam epitaxy has been firstly studied systematically. The samples of single layer QDs were undoped and directly doped with Be of 1×1017cm-3, 5×1017cm-3, and 2×1018cm-3 in 2.5ml InAs layer, respectively. The samples of multi-layer QDs were undoped and doped with Be of 3×1016cm-3 homogeneously. When the doping level is low, a decrease in line width and a little blue shift in peak are observed in PL. However, when the doping level is high, the uniformity and photoluminescence peak intensity of QDs will be decreased. With doping, Be atoms act as the nucleation centers in the formation of QDs. Due to doping induced nucleation centers, there are more nucleation centers in the doped samples. The size fluctuation of QDs becomes smaller. Hence the line width of PL spectra will decrease. There will be more and more nucleation centers with the increasing of doping level. So more and more QDs will be formed. With increasing the number of QDs, there will be amalgamation between different small QDs. So the size fluctuation of QDs becomes larger, which will cause the increase in line-width and decrease in peak intensity in PL. Another reason for the phenomena may be due to the incorporation of nonradiative impurities with a higher level doping. Thus, appropriate doping maybe helpful to the formation of uniform QDs. However, unduly doping seems to lower the quality of QDs. The work will be very meaningful for the fabrication of self organized InAs quantum dots devices.关键词：self-organized InAs quantum dots;photoluminescence;doping131|72|0更新时间：2020-08-11
- 摘要：Si/SiO2 superlattice structure was designed and prepared by rf magnetron sputtering technique. The high pure polycrystal Si was taken as sputtering target. SiO2 film was obtained by using Ar+O2 as sputtering atmosphere; Si film was obtained by using Ar as sputtering atmosphere; Si/SiO2 superlattice structure was prepared by shutting off O2 or openning O2 repeatedly. The thicknesses of Si and SiO2 layers were controlled by sputtering power or velocity of moving substrate in front of target. The periodic structure of superlattice was demonstrated by TEM and low-angle X-ray reflection spectra. The optical transparence spectra showed that the optical absorption edge shifted to shorter wavelength when thickness of Si layer was decreased. Laser Ramman spectra of the samples before and after annealing gave the evidence of existence of Si quantum dots in Si layer and the size of Si quantum dots. Blue-green ACEL from Si/SiO2 superlattice with double insulating layers structure was obtained for the first time. There were several emission bands in EL spectrum. When the thickness of Si layer is decreased, the intensity of the shorter wavelength emission band increased quickly.关键词：superlattice;electroluminescence;Si quantum dots90|68|0更新时间：2020-08-11
- 摘要：The blue luminescence of unintentionally doped GaN at room temperature was studied. The unintentionally doped GaN films were grown on (0001) oriented Al2O3 substrate by MOCVD. TMGa and NH3 were used for Ga and N sources, respectively. N2 and H2 were used as carrier gases. Several analytical techniques were employed to characterize the grown layers. The optical properties of GaN films were measured by photoluminescence (PL), the electrical properties were characterized by the Van der Pauw Hall method at room temperature, and the crystalline quality were analysed by double crystal X-ray diffraction (DXRD). The research results indicated that the blue luminescence (about 2.9eV) at room temperature in unintentional doped GaN was obviously related with the compensation ratio. The intensity of blue luminescence was strong in high compensation ratio of GaN, while it was weak in light compensation ratio of GaN. It is considered that the blue luminescence was related with acceptor levels. Further study showed that the peak position of the blue luminescence shifted to lower energy by about 35meV with increasing excitation density, and the peak intensity was superlinear with the excitation density. The blue luminescence in undoped GaN was attributed to the transition from the free electron in conduction band to acceptor levels (eA luminescence).The results indicate that the blue luminescence will be restrained and the band edge emission will increase by using a large flow rate H2 in the main carrier gas.关键词：GaN;MOCVD;photoluminescence;compensation ratio84|87|7更新时间：2020-08-11
- 摘要：The correlation of the crystalline quality with the electrical characteristics of the unintentionally doped GaN films has been studied. The growth of unintentionally doped GaN films was performed by MOCVD method using a home-made vertical reactor operating at atmospheric pressure. The growth was carried out on (0001) oriented sapphire substrates using trimethylgallium (TMGa) and blue ammonia (NH3) as Ga and N sources, respectively. The mixed gases of hydrogen and nitrogen were used as the carrier gases. A thin buffer layer with thickness of about 15nm was grown at 520℃ and recrystallized at 1060℃ for 6 minutes. The GaN films were grown at 1060℃. The crystalline quality was analyzed by the Full-width at half-maximum (FWHM) of double crystal X-ray diffraction (DXRD). The electrical properties were measured by Van der Pauw Hall method at the room temperature. Table 1 shows the FWHM of X-ray double crystal diffraction and the electrical parameters for GaN films grown by MOCVD on sapphire (0001). Fig.1 shows the function of the electron drift (solid curves) and Hall (dashed curves) mobility on the compensation ratios of 0.00, 0.15, 0.30, 0.45, 0.60, 0.75 and 0.90 for 300K. Fig.2 shows the double crystal X-ray rocking curve for unintentionally doped GaN grown by MOCVD on sapphire (0001). These results indicate that there is no obvious relationship between the mobility and the carrier concentration, and neither between the FWHM and the mobility or the carrier concentration. However, there exist an obvious correlation of the FWHM of double crystal X ray diffraction to the compensation ratio at room temperature for the unintentionally doped GaN/Al2O3 films. Fig.3 shows the dependence of FWHM on the compensation ratio in unintentionally doped GaN. The FWHM of heavily compensated GaN is broad while that of lightly compensated GaN is narrow. The FWHM becomes wider from 5.6 to 17 minutes with the increasing of the compensation ratios from 0.46 to 0.79. Some possible mechanisms responsible for those phenomena have been analyzed. As for unintentionally doped GaN films with high compensation ratio, the existence of many acceptors and donors will result in deformation in the crystal lattice, so the FWHMs of these samples will be broad. For the samples with low compensation ratio, the lattice deformation is relatively small, and the FWHM is also relatively narrow.关键词：GaN;compensation ratio;X-ray double crystal diffraction;MOCVD93|97|1更新时间：2020-08-11
- 摘要：Fluoroborate glasses have been the subject of several spectroscopic investigations due to their potential as laser host matrix. In recent letters infrared conversion to visible and ultraviolet by Yb3+-Er3+ and Yb3+-Ho3+ ions in some glasses host has been reported. In this paper, the aim is to find suitable host for upconversion luminescence, and a fluoroborate glass co doped with Yb3+ and Er3+ was designed. The optical transition properties and upconversion under 970nm LD excitation were discussed for this glass sample. The fluoroborate glass with component 30H3BO3-15AlF3-19.5PbF2-10BaF2-10ZnF2-10NaF5Yb2O3-0.5Er2O3 was prepared. The absorption spectrum was measured in visible range from 350nm to 700nm. The J-O theory was used to calculate the optical properties of Er3+ and Yb3+ codoped in fluoroborate glass. The J-O parameters were obtained, Ω=1.2E-20(cm2), Ω=3.6E-20(cm2), Ω=7.7E-21(cm2). The transition probabilities, the oscillator strengths, branching ratios and the radioactive lifetimes were obtained. The red (4F9/2→4I15/2) and green (2H11/2,4S3/2→4I15/2) upconversion luminescence under 970nm LD excitation was observed, the upconversion mechanism was discussed. In this system the upconversion luminescence by energy transfer from Yb3+ to Er3+ and from Er3+ to Er3+ and excited state absorption of Er3+ was proposed. The relationship between LD working current and intensity of upconversion luminescence was discussed. The results confirmed that the upconversion process is consisted by two photons.关键词：Er3+;fluoroborate glass;J-O theory;upconversion110|84|7更新时间：2020-08-11
- 摘要：Ca0.9Sr0.1S:Bi3+, Tm3+ is a kind of codoped host mixing material. In this work, excitation spectra monitored at different wavelength from 440nm to 520nm, also emission spectra excited at different wavelength from 250nm to 350nm were obtained. Decay curves of the afterglow were measured at different emission position from 440nm to 520nm. UV excitation spectra showed that Tm3+ 's contribution to the Bi3+ ion's 3P1 to 1S0 emission (at 453nm) came from 325nm of charge transfer transition. The Tm3+ also acted as an electron-trapping center with its trap depth about 0.5eV. The decay kinetics of afterglow of the materials having both electron and hole trapping centers may be described as It=I0[(1+γet)(1+γht)]-n. In the case of Ca0.9Sr0.1S:Bi3+, Tm3+, γh=0.0168, γe=0.0001, n=1.1. Considering the linear relationship of the host mixing materials, the depth of the electron traps and the hole-traps can be written as De=βe-αx and Dh=(βhc-αhx)x+( βhs-αhx )(1-x ).关键词：luminescent powder;host mixed;codoping84|58|0更新时间：2020-08-11
- 摘要：Aggregation features of molecules in various types of Langmuir-Blodgett (LB) multilayers were investigated by using the steady-state and time-resolved fluorescence techniques. The fluorescence peak of interleaving hemicyanine/arachidic acid multilayers is at 598nm which shows a significant blue shift with respect to that of hemicyanine(615nm) in solution. As the interlayer interactions were screened by arachidic acid layers, intralayer interaction of hemicyanine molecules caused the formation of H-aggregates in interleaving hemicyanine/arachidic acid multilayers. However, the fluorescence peaks of pure Y and Z-type hemicyanine multilayers are at 645nm and 635nm, respectively. It indicated that the molecules mainly formed J-aggregates which lead to a significant red shift of fluorescence band due to the stronger interlayer interactions. It indicated that the interlayer interaction would be stronger than the intralayer interaction because of the lack of the screening of AA and the inclination angle θ would be reduced (close to 0), which caused J-type aggregation. The temporal profile could be well fitted by the model. The lifetime, relative amplitudes of the components and molecular numbers in an aggregate were deduced, Notice that the molecular numbers and amplitudes of the aggregates in the pure hemicyanine samples were larger than that in LB interleaving films.关键词：Langmuir-blodgett (LB) multilayers;aggregate;time-resolved fluorescence86|79|1更新时间：2020-08-11
- 摘要：Anodic alumina films were prepared by anodization of ~400nm thick aluminum films evaporated on silicon substrate using electron beam in 15wt% H2SO4 at 250C under a constant DC voltage of 40V. FTIR, PL and PLE measurements were performed on those resulting Si based anodic alumina films based upon which possible origin of the PL was discussed. All three PL peaks were analyzed to be related to oxygen deficient defects emission similar to that in sapphire. Among them two sharp peaks centered at 312nm, 367nm were basically attributed to F+ and F center emission respectively while the origin for third broad 449nm peak is still unknown and further detailed work is required.关键词：anodic alumina;photoluminescence99|114|0更新时间：2020-08-11
- 摘要：This paper introduced the experimental set-up method for studying the impacts of Cu2+ on the sonofluorescence of three aqueous luminol-alkaline solutions, and compared the sonofluorescence spectra of the solution with Cu2+ with that of the solution without Cu2+. The spectra showed that the Cu2+ increased the sonofluorescence intensity of the aqueous solutions of luminol-NaOH and luminol Ca(OH)2, and showed red-shifts by 6nm and 9nm in their maximum sonofluorescence peaks, respectively. On the other hand, the Cu2+ decreased the sonofluorecence intensity of the aqueous solution of luminol-Na2CO3, and produced a blue-shift by 5nm in its maximum sonofluorescene peak. But, it seems that the Cu2+ didn't change the sonofluorescence wavelength range of 370～750nm for above solutions. The experiment and results represented that, to say the least of it, the aqueous luminol-alka-line solution would become a luminescent system of sonofluorescence for detecting Cu2+ or even other ions.关键词：Cu2+;luminol-alkaline solution;sonofluorescence;intensity;red-shift;blue-shift106|68|0更新时间：2020-08-11
- 摘要：UV-written fiber Bragg gratings is adopted to study its strain sensing properties. Axial strain and refractive index changes of fiber gratings are caused by external strains so that Bragg reflected wavelength is shifted. The strain of fiber gratings vs. Bragg reflected wavelength is measured experimentally at 20℃ using spectrum analyzer that can disperse in the region of 400～1800nm wavelength and using InGaAsP/InP light emitting diode as bandwidth source. It shows that Bragg reflected wavelength shift vs. external strain changes of fiber gratings is linear in the range of 155.4～156.8nm wavelength.The sensitivity of fiber grating to the external strains is 1.211pm/με, which basically agrees with theoretical calculation. By the using strain sensing properties of fiber grating, the sensing head of pressure has been designed and made. It consists of a upper and a below metal plates and two fine adjustable screws on the upper metal plate. Two ends of fiber gratings are fixed respectively on two fixed points. The microrise and microdrop of the upper metal plate which acts as load stage can be regulated by fine adjusting screws. By adjusting the screws in stretch strain region of the fiber gratings,the fiber grating becomes as long as possible to keep larger linear region of the sensing head. And tested zero of the sensing head is determined at constant temperature of 20℃. The shift of Bragg reflected wavelength caused by pressure changes are measured with sensing head under two same material plates with different thicks. It shows that different gauge regions can be designed by chosing metal plates with different material or same material metal plates with different thicks. The sensing head of pressure can be widely applied in the measurement of different gauge regions and loads.关键词：UV-written;fiber grating;strain sensing114|87|2更新时间：2020-08-11
- 摘要：The relation between the transformation rates of photochemistry reaction and the time of illumination was described. Under the conditions of optimum matched spectrum, the ergosterol used as raw materials will beturned into vitamin-D2 and other byproducts. By series of experiments, it is found that the 283nm-waved ultraviolet light source is fit for the photochemistry reaction.With this light source, the transform effect is best. With increasing illumination time, the transformation rate goes up and the content of the main product vitamin-D2 increases.But at the same time the content of the by-products including tachysterol and lumisterol increase accordingly.So the time of illumination is a key factor in the production of vitamin-D2. We hope that these data on Vitamin D2 will be usefal to producers, with which they can compare their manufacture parameters and improve their production technology.关键词：photochemistry reaction;ergosterol;vitamin-D2(VD2);ultraviolet light source;transformation rate126|154|2更新时间：2020-08-11
- 摘要：The formation of self-assembled CdSe quantum dots under Stranski-Krastanow (S-K) mode by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) was reported for the first time. The samples were grown directly on GaAs (100) surfaces by LP-MOCVD. DimethylSelenide (DMSe) and DimethylCadmium (DMCd) were used as precursors. The growth pressure was kept at 2.93×104Pa and the growth temperature was 500℃. CdSe with the thickness of about 2 monolayers was grown directly on GaAs (100) surfaces. For the purpose of AFM observation, this uncapped sample was cooled down immediately to room temperature and was monitored under a Digital Instruments Nanoscope Ⅲa system at the same day of growth. The AFM images show that the average diameter, height and density of those self assembled CdSe quantum dots are 50±15nm, 13±4nm and 5μm-2, respectively. And those dots' diameter-height ratio is about 4～5, just the same as those results observed in other Ⅱ-Ⅵ and Ⅲ-Ⅵ compounds which were grown under S-K mode by MBE.关键词：CdSe;self-assembled;quantum dots;S-K mode122|97|0更新时间：2020-08-11
- 摘要：Optically pumped stimulated emission behavior was demonstrated in a slab-waveguide structure formed by substrate/organic film/air. The organic film was deposited by high vacuum (1×10-3Pa) co-evaporating of 8-hydroxyquinolinato aluminum(Alq) and laser dye DCM. A wafer of quartz was used as the substrate. The thickness of the organic film was about 300nm, and the percentage of DCM was about 3%. The third harmonic output(355nm) of a Nd:YAG laser was used as the excitation source. The pulse width was about 300ps. The repetition rate was 2Hz. The pump beam was focused onto the sample with a cylindrical lens (f=10cm). The excitation area was a typical 10mm×0.2mm stripe. Detected from the side or the surface of the organic film, the fluorescence spectrum with the FWHM (the full width at half maximum) of about 110nm was achieved at excitation pulses energy of 0.1μJ. Increasing the excitation pulse energy to 4μJ, the FWHM of the spectrum detected from the edge of the sample reduced to 13nm with the peak at 620nm and the spectrum from the surface was still a broad band. The change of the emission spectra detected from the edge of the sample showed a clear threshold action and gain narrowing phenomenon when increasing the excitation intensity. The spectrally gain narrowing results from the amplified spontaneous emission (ASE) of the waveguide along the excitation stripe in the film.关键词：planar waveguide;stimulated emission;amplified spontaneous emission;gain narrowing103|147|0更新时间：2020-08-11
- 摘要：White color emitting organic electroluminescence (EL) device is a convenient means to realize full-color display because the three necessary primary colors could be obtained by color filters from white back light. In this paper a new three-layer device is presented. We used N, N'-bis-(lnaphhyl)-N, N'-diphenyl-1, 1'-biphenyl-4, 4'-diamine (NPB) as the hole transport layer, Alq as the electron transport layer, CuPc as the buffer layer, and TPBi as the blocking layer inserted between NPB and Alq.The 5,6,11,12-tetraphenyltetracene (Rubrene) as dopant was doped into the blocking layer.It was thought initially that if energy transfer existed between the host and dopant in photoluminescence (PL) of NPB doped with Rubrene, white emission might be obtained in a device such as ITO/CuPc/NPB:Rubrene/TPBi/Alq/Mg:Ag. Thus the PL of NPB:Rubrene system excited by NPB absorption band with different dopant concentrations were investigated in advance. There are two bands in the PL spectra, the blue one is emitted by NPB and the yellow one is by Rubrene. The ratio of these two bands can be adjusted by changing the Rubrene concentration. This shows that energy transfer does occur from NPB to Rubrene. Time-resolved spectra of this system, which will be given in another paper, confirm further that the energy transfer exists and is quite effective. White emission can be produced by adjusting the concentration of Rubrene in PL. However, devices of structure ITO/CuPc/NPB:Rubrene/TPBi/Alq/Mg:Ag were made according to these results with TPBi as the blocking layer, white emission can not be obtained by changing the Rubrene concentration.For another device of structure ITO/CuPc/NPB/TPBi:Rubrene/Alq/Mg:Ag, with a blocking layer TPBi doped by Rubrene concentration 1.5% inserted between NPB and Alq, white emission can be obtained. The highest luminance and maximum efficiency are 8635cd/m2 and 1.39lm/W respectively, CIE coordinate x=0.31, y=0.32. The color of the emitted light can still be optimized by adjusting the relative thickness of the relevant layers and dopant concentration.The electroluminescence mechanism of two kinds of cells was discussed.关键词：white displays;organic thin film;electroluminescent devices99|81|2更新时间：2020-08-11
- 摘要：In order to use organic light-emitting devices (OLEDs) in display application, it is very important to obtain red emitting light. There are two methods for obtaining red emitting light:doping high fluorescent dyes in host or using metal complexes. Phosphorescent dyes has been used efficiently recently. In this letter, we demonstrate red organic light-emitting devices (OLED) with the electroluminescent layers consisting of aluminum tris(8-hydroxyquinoline) (Alq3) doped with the dye DCM and DCJTB, which the emission color depends on the concentration of DCM and DCJTB. The typical cell structure is as follows:[ITO/hole transport layer (60nm, TPD) /emitting layer(60nm, Alq3+red dopant) /LiF(0.5～2nm)/Al(150nm)]. For DCM doped devices, the maximum luminance of 148000cd/m2 (chromaticity coordinates:x=0.51, y=0.47) and 5730cd/m2 (chromaticity coordinates:x=0.58, y=0.42) are measured for DCM concentration of 0.2% and 2% in Alq3, respectively; and for DCJTB doped devices, 17400cd/m2 (chromaticity coordinates:x=0.51, y=0.46) and 3846cd/m2 (chromaticity coordinates:x=0.63, y=0.37) are obtained for DCJTB concentration of 0.2% and 2% in Alq3, respectively.关键词：red light emission;organic thin film;electroluminescent devices100|68|2更新时间：2020-08-11
- 摘要：The operating mechanisms of the OLEDs involve injection of electrons and holes from the electrodes, and electron-hole recombination which emits the light. To balance the numbers of electrons and holes injected from electrode and obtain high emission efficiency, several hole injecting buffer layers such as CuPc, Carbon, Al2O3 and SiO2 have been used to improve the efficiency and lifetime of the OLEDs. In this study, highly efficienct and bright organic electroluminescent devices were developed using lithium fluoride (LiF) film as hole and electron injecting layers. Typical OLEDs have the structure of ITO glass/LiF/NPB(70nm)/Alq(70nm)/LiF(0.5nm)/Al(200nm). The device with a 2.0nm LiF hole injecting layer showed the luminance of 1210cd/m2 at 20mA/cm2 which corresponds to an efficiency of 6.0cd/A. In contrast, the device without LiF hole injecting layer exhibited 617cd/m2 at the same current density which showed an efficiency of 3.2cd/A. These results suggest that the LiF hole injecting layer with a proper thickness can enhance the efficiency of the OLEDs due to blocking the injection of holes.关键词：buffer layer;organic thin film;electroluminescent devices109|86|2更新时间：2020-08-11
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