最新刊期
卷 32 ， 期 7 ， 2011
- 摘要：Selection rules studied here tell whether the processes, such as absorption and emission, nonradiative decay, or energy transfer happen or not. They depend on the approximation adopted. A thorough analysis of these selection rules have been given in this work and the application of these selection rules have been demonstrated through a few examples with experimental data collected from the literature.关键词：radiative transition;nonradiative decay;energy transfer;rare earths;selection rules473|630|6更新时间：2020-08-12
- 摘要：We theoretically analyzed the bonding and anti-bonding energy states in the GaAs/Al0.35Ga0.65As asymmetric coupled quantum dots under a series of electric fields. The carrier tunneling effect strongly influences the exciton energy and oscillator strength.We find that energy splitting of anti-crossing occurs under an critical electric field for hole bounding and anti-bonding states, and both the energy gap and the critical field decrease with increasing the barrier distance. Meanwhile, the exciton luminescence intensity changes from bright(dark) to dark(bright) under external fields.关键词：exciton;quantum dot;bonding state97|139|0更新时间：2020-08-12
- 摘要：In2O3 ∶ Ho3+,Yb3+ nanocrystals with efficient upconversion luminescence were prepared by solvent thermal method using glycol as solvent. The samples were characterized by X-ray diffraction(XRD), transmission electron microscopy (TEM), diffuse reflectance spectra, and upconversion luminescence spectra. XRD results indicate that the products are cubic phase. TEM images show that the In2O3 ∶ Ho3+,Yb3+ nanoparticles are sphere shape with an average size of 30 nm. The diffuse reflectance spectra give four narrow bands at 448, 538, 644 and 975 nm, corresponding to the 5I8→5G6 (448 nm), 5I8→5S2/5F4 (538 nm), 5I8→5F5 (644 nm) transitions of Ho3+ ions and 2F7/2→2F5/2 (975 nm) transition of Yb3+ ions. Under the excitation of 980 nm, In2O3 ∶ Ho3+ ,Yb3+ nanocrystals can emit strong green emission and weak red emission, corresponding to (5F4,5S2)→5I8, 5F5→5I8 transitions of Ho3+. Upconversion luminescence of In2O3 ∶ Ho3+,Yb3+ nanocrystals codoped with different concentrations of Ho3+ and Yb3+ ions were investigated to improve the luminescene intensity. The results show that the strongest upconversion emission can be achieved at a Ho3+ mole fraction of 3% and an Yb3+ mole fraction of 4%. The lnI-lnP curves show that both the green and red emissions are double-photon process and the possible mechanism is proposed.关键词：Ho3+/Yb3+;In2O3;solvent-thermal method;upconversion114|98|1更新时间：2020-08-12
- 摘要：Europium (Ⅲ)-doped CaSnO3 was prepared by hydrothermal method. The sample was characte-rized by X-ray diffraction, field emission-scanning electron microscopy (FE-SEM) and photoluminescence (PL). The experimental results indicate that this phosphor can be effectively excited by charge-transfer band (280 nm), ultraviolet light 395 nm and blue light 465 nm. The wavelengths at 395 nm and 465 nm are nicely fitting with the emission wavelengths of widely applied ultraviolet or blue LED chips.关键词：CaSnO3 ∶ Eu3+;hydrothermal synthesis;red emitting phosphors110|81|2更新时间：2020-08-12
- 摘要：Eu3+ activated LiBaPO4 phosphor with several emission peaks (589, 594, 619, 655 and 692 nm), under the near ultraviolet light (401 nm) was synthesized by the high temperature solid state reaction method. And the phase present of the phosphor was characterized by powder X-ray diffraction (XRD), the spectrum of the phosphor was measured by a SHIMADZU RF-540 fluorescence spectrophotometer. It was found that the processing parameters, including the activator content and the charge compensator, affected the emission intensity and other luminescent properties. The emission intensity of LiBaPO4 ∶ Eu3+ phosphor reaches the maximum at 5% Eu3+, and the concentration self-quenching mechanism is the d-d interaction by Dexter theory. When the charge compensator incorporated, the emission intensity of the phosphor can be enhanced. The results show that LiBaPO4 ∶ Eu3+ is a promising red phosphor for white LED.关键词：white LED;LiBaPO4 ∶ Eu3+;luminescent characteristics108|97|4更新时间：2020-08-12
- 摘要：The red phosphors MMoO4 ∶ Eu3+(M=Ca,Sr,Ba) were prepared by hydrothermal synthesis method. The crystalline phase, morphology and luminescence characteristics of the phosphor particles were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM),excitation and emission spectra. The results show that the phosphors prepared at 800 ℃ temperature are with MMoO4 (M=Ca,Sr,Ba) crystalline phase, the phosphors have small particle size and uniform particle size distribution. Upon excitation with 395 nm and 465 nm light, all the MMoO4 ∶ Eu3+(M=Ca, Sr, Ba) phosphors show bright red emission due to the 4f-4f transitions of Eu3+ ions, and the highest photoluminescence intensity at 616 nm is found. The excitation and emission spectra show that this phosphor could be effectively excited by ultraviolet(395 nm) and blue light(465 nm), nicely fitting with the emission wavelengths of widely applied ultraviolet or blue LED chips.关键词：red phosphor;hydrothermal synthesis;molybdate110|103|6更新时间：2020-08-12
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AEP-assisted Hydrothermal Synthesis and Upconversion Luminescence of NaYF4 ∶ Yb3+ ,Er3+ Nanocrystals
摘要：NaYF4 ∶ Yb3+ ,Er3+ nanocrystals were successfully prepared by the combination of coprecipitation and hydrothermal methods using 2-aminoethyl phosphate (AEP) as chelator. It is found that the crystal structures of the NaYF4 ∶ Yb3+ ,Er3+ nanoparticles before and after hydrothermal treatment are both in cubic phase, the size of which is about 80 nm. The upconversion luminescence from the two samples was observed under the excitation of 980 nm laser. The green and red emission bands are attributed to the transition of 2H11/2,4S3/2→ 4I15/2 and 4F9/2→4I15/2 energy levels of Er3+ ions, respectively. The upconversion luminescence intensity of the sample with hydrothermal treatment is much stronger than that of the sample without hydrothermal treatment due to the improved crystallization of the samples and the reduction of organic ligands on the surface of the NaYF4 ∶ Yb3+ ,Er3+ nanoparticles.关键词：nanocrystals;hydrothermal synthesis;upconversion;rare earth104|77|1更新时间：2020-08-12 - 摘要：CdS nanoparticles were synthesized on ZnO nanorods by a sample hydrothermal method. The as-grown ZnO/CdS heterostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD). It is shown that ZnO nanonods could be gradually corroded with the growth process of CdS. We selected ZnO-CdS nano-composites as a configuration to decompose methyl orange (MO) under ultraviolet and green light irradiation. Compared with ZnO nanorods, the absorption spectrum of CdS/ZnO nano-composites could be extended from ultraviolet to visible light, then compared with ZnO nanorods the photocatalytic activity of the nano-composites was obvious enhanced.关键词：ZnO;CdS;nano-composites;photovoltaics177|158|3更新时间：2020-08-12
- 摘要：A series of novel red phosphors LiLa2O2BO3 ∶ Eu3+ were synthesized by conventional solid state reaction method using H3BO3 (99.5%), La2O3 (99.99%), Eu2O3 (99.99%) and Li2CO3 (97.0%) with different Eu3+ concentrations. The crystal structure and spectral features of the phosphors were characterized by XRD,excitation and emission spectra, respectively. The XRD pattern result indicates that the LiLa2O2BO3 crystals are stably existed.The lattice parameters were calculated by the Le Bail model method. We can also conclude from XRD patterns that unknown phases are formed with higher concentration Eu3+ doping. The excitation spectrum data demonstrate that these phosphors could be effectively excited by ultraviolet (UV) (396 nm) and blue (466 nm) light, which represent highly future prospects in both ultraviolet and blue light emitting diodes (LED) chips. Due to the 5D0→7F2 transition of Eu3+, the phosphors have best emission spectrum performance of 613 nm and 623 nm, illustrating Eu3+ occupy the non-centrosymmetric lattice site in LiLa2O2BO3 phases. The optimal doping concentration of Eu3+ was 20%. Our further research indicates the luminescent intensity increases significantly by doping optimal concentration of Si4+ ions. The CIE chromaticity coordinates are much closer to the standard of NTSC(x=0.670,y=0.330) by partly replacement of B3+ by Si4+ ions.关键词：borate;red emitting phosphor;LiLa2O2BO3;white LED154|120|5更新时间：2020-08-12
- 摘要：A series of phosphors Ba0.955Al2-xBxSi2O8 ∶ Eu2+(x=0~0.5) were prepared by solid-state reaction in weak reductive atmosphere. The lattice positions and the luminescent mechanism of Eu2+ in the host were discussed. The effects of B3+-substitution on the host lattices and spectral properties were also investigated. It was found that when B3+ entered BaAl2Si2O8 lattice and substituted for Al3+ complete solid solutions formed in the whole range of x=0~0.5. The lattice parameters (a, b, c) and unit cell volume of phosphors Ba0.955Al2-xBxSi2O8 ∶ Eu2+ (x=0~0.5) decreased linearly and lattice parameter β increased linearly as boron content increased. A broad excitation spectrum consists of four excitation bands, which locate between 225 nm and 400 nm,its peak wavelength is at 337 nm,and basically does not change with the content of B3+. The full width at half maximum is 93 nm. The emission spectrum is also a broad band between 370 nm and 600 nm and its apparent peak is at 437 nm,which can be fitted by two peaks at 423 nm and 457 nm.Two fitted peaks are blue shifted with the increasing of the content of B3+-substitution.关键词：silicate;BaAl2Si2O8;B3+-substitution;Eu2+116|81|3更新时间：2020-08-12
- 摘要：Eu3+ ,Dy3+ ,Sm3+ doped Ca(Sr,Ba)WO4 phosphors were synthesized by the co-precipitation method in order to investigate the effect of different metallic cations on luminescence properties of rare earth ions. The data of X ray diffraction (XRD) indicated that the crystal structures of CaWO4, SrWO4, BaWO4 belong to tetragonal, I41/a(88) and the diffraction peaks moved towards smaller angle with the increasing diameter of the metal cation. The data of X-ray diffraction (XRD) of BaWO4 synthesized under different temperatures showed that the diffraction peaks were broader under lower synthesized temperature, which can be attributed to the smaller particle sizes (about 100~300 nm seen from SEM morphology) of BaWO4 phosphors under lower synthesized temperature. The emission spectrum and excitation spectrum of Eu3+ ,Dy3+ ,Sm3+ doped Ca(Sr,Ba)WO4 phosphors were measured. J-O strength parameters Ωλ (λ=2,4) of Eu3+ ion, were calculated. The data indicated that Ω2 decreased with increasing diameter of the metal cation, which can be used to explain the decrease of emission intensity of Eu3+ doped Ca(Sr,Ba)WO4 with increasing diameter of the metal cation. However, the emission intensity of Sm3+ doped SrWO4 phosphors were more stronger than that of Sm3+ doped Ca(Ba)WO4 which can be explained by the energy transfer between WO2-4 and rare earth ions. It can be seen from the emission spectrum of Dy3+ ,Sm3+ doped Ca(Sr,Ba)WO4 the emission peaks moved towards shorter wavelength and their bandwidths were reduced, which was explained by the configurational coordinate diagram.关键词：rare earth ions;emission;J-O strength parameters;configurational coordinate diagram168|116|3更新时间：2020-08-12
- 摘要：A serial of Er3+ ∶ Ag-bismuth glass nanocomposites were prepared by the conventional melting-quenching method. The effect of nano-silver addition on the emission intensity of Er3+ was investigated. The experimental results indicate that Ag nanoparticles of mass fraction of 0.2% drastically enhances the intensity(~4.6 times) of 1.53 μm emission bands of Er3+ .Local field enhancement induced by Ag0 surface plasmon resonance (SPR) and energy transfer from fluorescent Ag0→Er3+ ions are found to be responsible for this enhancement.关键词：silver nanoparticles;bismuth glass;fluorescence intensity;surface plasmon resonance125|150|1更新时间：2020-08-12
- 摘要：Eu3+ doped 2ZnO·2.2B2O3·3H2O, was synthesized by hydrothermal method. The morphology, crystal phase and luminescent properties of the sample were characterized by scanning electronic microscopy (SEM), X-ray diffraction (XRD) and fluorescence spectra, respectively. The SEM image shows the particle size of the as-prepared powder is ranged from 0.1 to 1 μm. The crystal phase of the as-prepared powder is toward to glass state with the increasing of Eu3+ content. The fluorescence spectra of Eu3+-doped 2ZnO·2.2B2O3·3H2O reveals that the emission intensity of Eu3+ excited by 253 nm (corresponding to the charge transfer band of Eu3+-O2-) is much stronger than it excited by 394 nm. The optimism doping concentration is 24% ∶ n(Zn2+)=24%]. When the annealing temperature is increased up to 400 ℃, decrease in the emission intensity of Eu3+ and appearance of a new fluorescence peak (the peak position at 470 nm) assigned to the emission of Eu2+ is observed.关键词：hydrothermal method;zinc borate;photoluminescence87|20|3更新时间：2020-08-12
- 摘要：We have demonstrated efficient blue electrophosphorescent organic light-emitting diodes (PHOLEDs) with double light-emitting layers (D-BOLED), by doping both hole and electron transport layers with iridium(Ⅲ) bis picolinate (FIrpic), simultaneously. The D-BOLED showed a peak efficiency of 23.4 cd/A, which was improved about 36.8% compared to the conventional blue PHOLEDs with a single light-emitting layer (S-BOLED), by doping either hole or electron transport layer with FIrpic. We have attributed this improvement mainly to that the D-BOLED can efficiently use the triplet excitons that were generated by carrier recombination at the interface of FIrpic ∶ TCTA/ FIrpic ∶ TPBI and diffused into FIrpic doped charge transport layers and subsequently decayed radiatively on FIrpic sites.Combining a DCJTB doped color conversion layer with the D-BOLED, we have achieved a WOLEDs with a peak efficiency of 10.7 cd/A and CIE coordinate of (0.33, 0.33).关键词：blue OLEDs;WOLEDs;double-emission layers;color conversion layers103|121|7更新时间：2020-08-12
- 摘要：GaN-based PIN radiation detectors were fabricated, and various response properties of the detectors under X-ray irradiation were studied. In the absence of X-ray irradiation, the detectors have very low leakage current less than 0.1 nA at -10 V. Time response of the detectors to X-ray was analyzed and simulated, following a reasonable interpretation of the physical mechanism. The relationship between signal to noise ratio(SNR) and applied bias was investigated, and an optimum voltage of -20 V corresponding to the best SNR was found.关键词：GaN;X-ray detector;signal to noise ratio;time response178|198|2更新时间：2020-08-12
- 摘要：This article fabricated the CuPc/C60 double-layer heterojunction organic photovoltaic devices, investigated the effects of different illumination intensity and temperature on device performance. The results showed that the illumination density directly determined the value of photocurrent under short circuit condition, while had little effect on the open circuit voltage. The short circuit density had little weak dependence on temperature. The device exhibited larger open circuit voltage with the reduction of temperature. According to the experimental data, This article theoretically analyzed the relationship of illumination intensity, tempe-rature short, circuit density and open circuit voltage, which provided a research foundation for the high performance of organic solar cells.关键词：device performance;the illumination intensity;temperature96|132|1更新时间：2020-08-12
- 摘要：The organic thin film transistors (OTFTs) based on multi-layer gate dielectric were presented without vacuum breaks. As a result, the OTFTs show multi-functional properties, such as electric-switching, memory, and photosensitive. The memory effect was attributed to the structure of OTFTs, i.e. the utilization of the separated CaF2 nanoparticle islands acting as the charge trapping centers. The photo-responses included two different types of fast response and slow response, and are, respectively, originated from the generation of mobile carriers by the absorption of photo energy higher than the band gap energy of semiconductor and the tapped and released of photo-induced electrons by the traps in the dielectric at the electrical field modulation.关键词：organic thin film transistor;memory effect;photo-responses120|150|2更新时间：2020-08-12
- 摘要：The ZnO films grown with different growth temperature have been deposited on c-Al2O3 substrates by plasma assistant molecular beam epitaxy (P-MBE). Their crystal structures are characterized by X-ray diffraction (XRD). The XRD results indicate that all the ZnO films with the (002) preference orientation of hexagonal wurtzite structure. The full width at half maximum (FWHM) of the (002) diffraction peak decreases as the growth temperature increasing. The surface morphology of the ZnO films is measured by scanning electron microscope (SEM),the surface morphology of the ZnO films grown at different growth temperature changes gradually. In the SEM image of the film grown at 500 ℃,there are a large number of particles, and the surface of the film is rough. The particle size is about 50~100 nm.The particle size increases (about 100~200 nm) at 600 ℃ growth, which indicates that the particle size increase with the increasing of the growth temperature. As the film growth temperature reaches 700 and 800 ℃, it can be found that the surface of the film become uniform and smooth from the SEM image. The photoluminescence (PL) intensity of the ZnO film increased with the increasing of the growth temperature. The origin of the PL peak is the free exciton emission. The carrier concentration and Hall mobility of the films as a function of growth temperature are studied. Hall measurements show that all the films are n-type. The carrier concentration value decreases gradually from 3.4×1018 cm-3 to a value of 1.8×1018 cm-3 with increasing the growth temperature from 500 to 800 ℃. The Hall mobility of ZnO films rises from 11 cm2/(V·s) to 51 cm2/(V·s) with the increase of film growth temperature. The high quality ZnO thin films was obtained at 800 ℃,exhibiting that the FWHM of XRD is about 0.05°, the Hall mobility is about 51 cm2/(V·s), the carrier concentration is about 1.8×1018 cm-3.关键词：ZnO;P-MBE;PL165|147|0更新时间：2020-08-12
- 摘要：Delayed fluorescece (DF) is intrinsically related to the photosynthesis process, and it is a good method of researching the effect of various chemical and physical factors in vivo and in vitro on photosynthetic performance of plants. In this paper, the detection of DF emission spectra under the stress (heat, salt and UV-B) have been investigated in maize (98-2) sample. The maximal values of DF emission spectra at 685 nm and 730 nm were marked as F685 and F730 respectively. After comparative measurement of F730/F685 ratio, DF intensity and Fv/Fm, the linear fitting results shown that the two parameters has a good linear correlation (R2≥0.960 9). The experimental results suggest that the degree of plant photosynthetic physiology damage whether caused by different concentration or different stress time can be effectively measured by F730/F685. Moreover, the responses of F730/F685 ratio of DF emission spectra to the stress could be a new and useful judgment to identify and evaluate the stress damage of the samples.关键词：felayed fluorescence sdpectra;F730/F685;stress physiology;photosynthetic physiology86|68|0更新时间：2020-08-12
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