最新刊期
卷 41 ， 期 1 ， 2020
- 摘要：Upconversion nanocrystals capable of tunable emitting color have shown wide application prospects. In this paper, we designed and successfully synthesized compact multi-layer core-shell nanocrystals. Different layers in a nanocrystal respectively produce upconversion luminescence with red, green and blue color, excited by various lasers. The emitting color with high purity can be further tuned in real-time within full color range. In addition, the luminescence intensity dependences on the pump power were recorded and used to investigate the luminescence mechanisms. The proposed compact core-shell nanocrystal with tunable color in a single nanoparticle shows great potentials for the applications such as bio-detection and imaging, display devices with ultrahigh resolution and advanced anti-counterfeiting.关键词：lanthanide;core-shell nanocrystal;upconversion;real-time color-tuning218|214|1更新时间：2020-08-12
- 摘要：To develop a novel red light luminescent material was important to prepare the high-efficiency organic light emitting devices. In this paper, a new kind of D-π-A-π-D red light luminogen utilizing fluorenone as acceptor and 3,4,5-trimethoxybenzene as donor was designed and synthesized, named 3MeFO. Its structure was confirmed by the 1H NMR spectra, 13C NMR spectra and X-ray single crystal diffraction. The compound had strong charge transfer and π-conjugated structure that contributed to the red shift and the PL peak of crystal was located at 620 nm. From the single crystal analysis, the introduction of methoxy groups had increased the intermolecular interaction owing to the formation of the hydrogen bond. Meanwhile, the compound exhibited excellent thermal stability properties, electrochemical performance that were benefit to prepare the OLED with the considerable electroluminescent properties.关键词：organic red light luminogens;D-π-A-π-D;molecular aggregation;OLED274|117|3更新时间：2020-08-12
- 摘要：The up-conversion BaGd2(WO4)0.5(MoO4)0.5:Yb3+/Tm3+ nano-crystals were synthesized by hydrothermal method with complexing agent PEG. The structure and properties of luminescent powder were examined by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The crystal structure of the sample was tetragonal system, which characterized by XRD. The results showed that the particle size was between 25-40 nm, which observed by SEM and TEM. The luminescence intensity was the strongest while the Yb3+ doping concentration was 6.0% and CYb3+/CTm3+=4:1. The blue emission peak at 475 nm corresponded to 1G4→3H6 transition of Tm3+, and red emission peak at 650 nm corresponded to 1G4→3F4 transition of Tm3+. The lg-lg plots of luminescence intensity and pump power revealed that blue emission peak was the three-photon absorption, red emission peak was the two-photon absorption. The quantum yields of the sample were near 0.9%. The BaGd2(WO4)0.5(MoO4)0.5:Yb3+/Tm3+ nano-crystals had excellent luminescent properties, which had high practical application value.关键词：hydrothermal;up-conversion;nano-crystal;BaGd2(WO4)0.5(MoO4)0.5:Yb3+/Tm3+200|259|3更新时间：2020-08-12
- 摘要：Mg2+, Zn2+ doped CaWO4:Eu3+ phosphors were synthesized by microwave-assisted heating solid state reaction method. The crystal structures of the samples were characterized by XRD,excitation spectra, emission spectra and fluorescence lifetime were investigated. The influences of the doping metal ions of Mg2+ or Zn2+ on the microstructure, luminescence intensity and fluorescence lifetime for synthesized samples were investigated. The results showed that they were still the tetragonal phase for Mg2+ or Zn2+ doped CaWO4:Eu3+ samples. Under 395 nm excitation, the luminescence intensities of CaWO4:2% Eu3+ samples doped with 0.5% Mg2+ or 0.5% Zn2+ increased by 1.3 and 2.1 times than that of undoped these ions, the luminescence intensities of CaWO4:3% Eu3+ doped with 3% Mg2+ or 3% Zn2+ powders increased by 7.3 times and 14.8 times than that of CaWO4:2% Eu3+ samples doped with these ions, and the luminescence intensities of CaWO4:3% Eu3+ doped with 3% Mg2+ or Zn2+ increased by 1.2 and 1.3 times than that of undoped these ions. The lifetime of 5D0 level of Eu3+ for the same sample excited at 262 nm was longer than that at 395 nm. Under 395 nm excitation, compared with fluorescence lifetime of CaWO4:2% Eu3+ sample, the lifetime of the samples doped with Mg2+ or Zn2+ increased first and then decreased. At the same excitation wavelength, compared with lifetime of CaWO4:2% Eu3+ sample doped with Mg2+ or Zn2+, the lifetime of CaWO4:3% Eu3+ samples doped with 3% Mg2+ or 3% Zn2+ all decreased.关键词：microwave-assisted heating solid state reaction method;Mg2+/Zn2+ co-doped CaWO4:Eu3+;luminescent properties;energy level lifetime194|146|2更新时间：2020-08-12
- 摘要：In order to prepare nitrogen-phosphorus co-doped graphene quantum dots (N,P-GQDs) to explore the tunability of their fluorescent properties, we use hydrothermal method with citric acid as carbon source and phosphonitrilic chloride trimer as nitrogen source and phosphorus source. Blue photoluminescence nitrogen-phosphorus co-doped graphene quantum dots (N,P-GQDs) were prepared. The structure and composition of N,P-GQDs were characterized by TEM and AFM, and their fluorescence properties were detected and studied by UV-Vis and fluorescence spectroscopy. Through some test characterization, it can be found that the prepared N,P-GQDs have a uniform size distribution with a lateral average size of about 4.8 nm, a lattice spacing of 0.24 nm, and a longitudinal average thickness of about 0.95 nm. When the excitation wavelength of N,P-GQDs is 329 nm, the maximum emission wavelength is 426 nm. In the optical performance test, it was observed that the fluorescence emission spectrum of N,P-GQDs has a strong dependence on the excitation wavelength, and it exhibits strong absorption to visible light. The quantum yield of N,P-GQDs was calculated by the quantum yield formula to be 10.4%. The prepared N,P-GQDs have excellent anti-bleaching ability and optical stability. The adjustability of the fluorescence properties of N,P-GQDs was studied by adjusting the dilution ratio of the sample. It was found that the fluorescence intensity first increased and then decreased with the increase of the dilution factor. In addition, the fluorescence intensity of the N,P-GQDs could be greatly quenched by the addition of a small amount of Fe3+, because the prepared N,P-GQDs have a strong complexing effect on Fe3+. Through the experimental research, the sensing analysis method of Fe3+ was established.关键词：graphene quantum dots;hydrothermal method;fluorescence;nitrogen and phosphorus doping179|144|3更新时间：2020-08-12
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First Principle Calculation of Electronic Structure and Optical Properties of ZnNb2-xTaxO6 (x=0-2.0)
摘要：According to the pseudopotential plane-wave method of first-principles calculation based on the DFT, we investigate the electronic structures and optical properties of ZnNb2O6 doped by tantalum with different concentrations, and their relationship is theoretically analyzed. The dielectric function and complex refractive, reflectivity, and absorption coefficents of ZnNb2-xTaxO6 (x=0-2.0) dominated by electron interband transitions are analyzed in terms of the precisely calculated band structure and density of satates. The results indicate that:(1)ZnNb2-xTaxO6 (x=0-2.0) is a indirect semiconductor and the band gap is 3.51-2.916 eV. the conduction band edge moves in the direction of the Fermi level after being doped. The density of states is mainly composed of O 2p, Zn 3d, Nb 4d and Ta 5d orbitis. (2)The valences electronic state of ZnNb2-xTaxO6 (x=0-2.0) is asymmetric and has a strong local area characteristic. These have an important influence on the electronic structure and the bonding chararcteristics of ZnNb2-xTaxO6 (x=0-2.0). (3)The calculation of the dielectric function reveals that ZnNb2-xTaxO6 (x=0-2.0) is anisotropic, the biggest peak of absorption will fluctuate narrowly around 3.02×105 cm-1, the extinction coefficient shows strong absorption characteristic near the band edge, and the mechanism of the electric and optical properties of ZnNb2-xTaxO6 (x=0-2.0) dominated by electron inter-band transitions are analyzed in terms of calculated band structure and desity of states, which provides theoretical basis for developing novel functional materials with high performance to be used in optoelectronic devices.关键词：ZnNb2O6;electrobic structure;optical properties;first-principles250|186|1更新时间：2020-08-12 - 摘要：Toward high performance GaN-based vertical cavity surface emitting lasers (VCSELs), we designed two types of InGaN/GaN coupled quantum wells (QWs) with different photo-electron interaction strengths, and studied their optical properties. In sample A, two sets of QWs are located at two antinodes of the optical field with two coupled QWs in each set. While in sample B, one set of QWs is located at one antinode of the optical filed with five coupled QWs. The relative optical confinement factors are calculated to be 1.79 and 1.47 for samples A and B, respectively. Optical measurements revealed that sample A has higher internal quantum efficiency (IQE) and higher radiative recombination efficiency. VCSELs fabricated by using sample A are featured with lower threshold pumping energy compared with the device fabricated from sample B. These results demonstrated that the structure of QWs will influence the photo-electron interaction, the IQE, the radiative efficiency of materials, and the threshold of VCSELs. In our case, structure of sample A is better than sample B.关键词：active region;relative optical confinement factor;internal quantum efficiency;recombination lifetime;vertical cavity surface emitting laser146|251|0更新时间：2020-08-12
Synthesis and Properties of Materials
- 摘要：A vortex fiber amplifier is proposed, which is based on a ring core fiber with erbium ions doped partially in the ring core areas. For the amplification characteristics of the erbium-doped fiber, the effects of fiber length, erbium-doped concentration and pump power on the gain characteristics of the signal modes are studied. The results show that the proposed fiber amplifier can support 22 orbital angular momentum (OAM) modes transmit stably. Meanwhile, the gain of all signal modes is larger than 23 dB, the signal-to-noise ratio is larger than 27 dB, and the differential mode gain (DMG) is less than 0.015 dB at C band (1 530-1 565 nm). The proposed vortex fiber amplifier based on the ring core fiber has the advantages of supporting large number of orbital angular momentum modes, low differential mode gain and high signal-to-noise ratio, which has important value for online amplification in an OAM-multiplex transmission system with long distance.关键词：fiber amplifier;orbital angular momentum;effective refractive index difference;differential mode gain;amplified spontaneous emission137|264|2更新时间：2020-08-12
- 摘要：In this paper, graphene quantum dots (GQDs) saturable absorber (SA) was prepared by hydrothermal method. The optical properties of the GQDs SA was characterized and the modulation depth was calculated to be 6.9%. Using the GQDs SA into diode-end-pumped Nd:YVO4 laser, a passively Q-switched operation of 1 063.5 nm laser was realized. Pulses as short as 200 ns under a repetition frequency of 1.64 MHz were generated at the absorbed pump power of 9.12 W, implying a pulse energy of 0.51 μJ with the peak power of 2.5 W.关键词：solid state laser;pulse laser;graphene quantum dots;saturable absorber;passively Q-switched171|128|0更新时间：2020-08-12
- 摘要：The dye-doped chiral nematic liquid crystal (DDCLC) laser with the SU-8 grating structure is designed and fabricated. Random laser emission is realized on both front and side of the device. After an SU-8 grating with a period of 15 μm is produced on the bottom glass substrate of an anti-parallel rubbing treatment cell by the lithography technique, uniformly mixed laser dye PM597, chiral compound S-811 and nematic liquid crystal (LC) TEB30A are infused into the cell. When the cell is pumped by a 532 nm Nd:YAG pulsed solid-state laser, a series of discrete random lasers with a full width at half maximum (FWHM) of 0.19 nm and a range of 580-590 nm, and two independent lasers with an FWHM of 0.19 nm and a range of 579-585 nm are excited at the side of the cell. In addition, a random lasing emission with an FWHM of 0.17 nm and a range of 584-592 nm is generated on the front of the cell. If the cell is heated to 61℃ in which the LC phase changes into an isotropic state, the laser emission with a wavelength of about 590.60 nm and FWHM of about 0.24 nm is still observed on the sideof the device. The experimental results show that after the SU-8 grating structure is introduced into the liquid crystal cell, photons can obtain feedback amplification not only through multiple scattering between liquid crystal molecules but also via Bragg reflection in the SU-8 grating. These two mechanisms can complement each other. The independent laser emissions on the side of the cell are mainly produced by Bragg reflection of the SU-8 grating. Whereas, the random lasers on the side and front of the cell are formed through multiple scattering between liquid crystal molecules.关键词：chiral nematic liquid crystal;SU-8 grating;random laser169|267|1更新时间：2020-08-12
- 摘要：In order to improve the optoelectronic properties of organic light emitting diodes (OLEDs) with a hybrid film as the light emitting layer, which included the thermally activated delayed fluorescent (TADF) as host matrix and the sky-blue fluorescent material guest, we adjusted the device structures properly to improve the utilization rate of the host material. The basic structure of OLED is ITO/NPB(40 nm)/DMAC-DPS:x% BUBD-1(40 nm)/Bphen(30 nm)/LiF(0.5 nm)/Al. First, the optoelectronic properties of host-guest OLED devices was studied with different doping ratio. Then, the DMAC-DPS (10 nm) was evaporated between the hole transport layer and the emission layer, it improved the utilization rate of the host material. Moreover, an organic material HAT-CN was added as the hole injection layer between the anode and the hole transport layer with the method of vacuum evaporation. Finally, the hole-only devices with or without HAT-CN were fabricated for the impedance spectra. The results indicated that the external quantum efficiency (EQE) of 4.92% was acquired at the optimal doping ratio (2%), it approached the theoretical EQE limit of the fluorescent OLEDs. The DMAC-DPS (10 nm) between the hole transport layer and the emission layer improved the utilization rate of the host material, led to a higher EQE of 5.37%, and breaked the limit of 5% of the EQE of traditional fluorescent OLEDs. The HAT-CN/NPB heterojunction units effectively reduced the driving voltage of OLEDs (2.7 V), and the maximum EQE increased to 5.76% at the same time. Additionally, From the lgJ-lgV curves and the impedance spectrum analysis, the hole-only devices with HAT-CN improved the hole mobility and reduced the impedance of the devices. This study shows that TADF materials have great potential in enhancing the optoelectronic performance of OLEDs.关键词：thermally activated delayed fluorescent (TADF);TADF-OLED;device structure hole only devices;impedance spectrum289|331|5更新时间：2020-08-12
- 摘要：In order to prepare high uniformity and large size high-definition RGB-OLED display terminals, we developed a new and low-cost color film deposition technology-thin film transistor(TFT) oriented film deposition technology, and studied the influence of width to length ratio of thin film transistor and gate voltage on the performance of electropolymerized luminescent film, to find the best preparation conditions. The electrochemical polymerization process of luminescent films on ITO pixels was controlled by TFT on AMOLED substrate with pixel size of 200 μm×200 μm. Firstly, the properties of TFT with different width-length ratio were characterized, and then electrochemical polymerized films prepared with different width-length ratio under different grid pressure conditions were characterized and analyzed. The experimental results show that under the control of TFT with the same width to length ratio, the higher the gate pressure is applied, the thicker the prepared film is, and the better the luminescence effect is. Under the control of TFT with different width-length ratio, the higher the width-length ratio is, the thicker the polymer film is, and the better the luminescence effect is. TFT with a width length ratio of 50 μm/10 μm is the most suitable condition under large gate pressure. The results lay a good foundation for the application of electrochemical polymerization in AMOLED display.关键词：electrochemical polymerization;active matrix organic electroluminescent display;thin film transistor186|183|3更新时间：2020-08-12
- 摘要：To increase the storage capacity per unit area, the traditional strategy is reducing the storage capacity per unit area, which will face bottlenecks such as the physical limits of device size. People are turning their attention to multi-level memory devices that can achieve high-density storage on a single device. In this paper, a multi-level memory device with optical write operation is fabricated by using the persistent photoconductivity (PPC) effect in organic thin film transistors, which effectively avoids the contact destructiveness and large work consumption of the device by the electrical write operation. The device storage state under different power (60, 100, 150 μW/cm2) and different duration (50-1 000 ms) 700 nm optical write pulse was studied. It exhibited extremely low operating power as low as 0.189 nJ under the optical pulse with power of 60 μW/cm2 and duration of 100 ms. When 16 consecutive optical write pulses were applied, the device showed 16 distinct effective storage state, it meant that multi-level optical write storage function with a storage capacity of 4 bits was realized in this device.关键词：organic thin film transistor;multi-level storage;optical storage214|247|1更新时间：2020-08-12
- 摘要：The gate driver circuit integrated by metal oxide thin film transistors(TFTs) generally adopts a double negative power supply scheme due to their depletion mode, which has difficulty in matching with the peripheral driving chip and a large power consumption. In the proposed circuit, a new coupling circuit structure is designed in order to generate a lower voltage than the negative voltage applied in the circuit. Consequently, the pull-down transistors of the output module can be completely turned off to prevent the current leakage problem caused by the depletion mode of oxide TFT. Thus, the power consumption can be saved since the voltage range of power source for single negative voltage source method is smaller than that for the two negative voltage sources method. In addition, the gate driver circuit using a single negative voltage source is easy to comply with the peripheral driving ICs. The proposed gate driver circuit has been fabricated on glass by metal oxide TFTs with the etch-stop layer (ESL) structure. The experimental results show that the proposed gate driver circuit achieves a full swing output with a pulse width of 10 μs at the clock frequency of 33.3 kHz under the load of RL=3 kΩ and CL=30 pF. The power consumption of the gate driver circuit is measured as 160 μW. The proposed gate driver circuit is suitable for a 1 980×1 080 resolution display at a frame rate of 60 Hz.关键词：In-Zn-O thin film transistors;gate driver;new coupling circuit structure187|252|1更新时间：2020-08-12
Device Fabrication and Physics
- 摘要：The characteristics of polarized infrared spectroscopy of water molecules in the silicon wafer slits during capillary evaporation were explored in this article. Associated with the slit of the silicon wafer, the direction of the infrared polarized light-horizontal:the polarized direction is parallel to the direction of the silicon wafer slit; vertical:the polarized direction is perpendicular to the direction of the silicon wafer slit-was changed to measure the polarized infrared absorption of water molecules at 3 900-3 600 cm-1 (stretching vibration) and 1 800-1 400 cm-1 (bending vibration). The results indicated that compared with horizontally polarized light, water molecules, which is evaporated from the slit of the silicon wafers, had a strong absorption for vertically polarized light in the range of 3 900-3 600 cm-1 (stretching vibration) and 1 800-1 400 cm-1 (bending vibration), demonstrating that the direction of dipole moment of water molecules evaporated by capillary action tends to the normal direction of the silicon wafers slit.关键词：evaporation of water molecules;capillary effect;polarized infrared spectrum150|308|0更新时间：2020-08-12
Luminescence Applications and Interdisciplinary Fields
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