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Issue 4 ， 2022
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Reversible Fluorescence Modulation and Applications Based on Chromic Effect in Inorganic Rare-earth Luminescent Materials Cover Article Enhanced Publication
Abstract：Inorganic rare-earth luminescent materials are widely used in lighting, display, laser and biomedicine. The fluorescence modulation is beneficial to expand the applications in temperature sensing, anti-counterfeiting, optical switch, optical storage, et al. However, the traditional fluorescence modulation methods such as designing the core and shell structure, changing the material composition to control the crystal field, and changing the doping type or concentration of rare earth ions to control the energy transfer are difficult to achieve reversible modulation of fluorescence properties, limiting their practical applications. Compared with these traditional methods, the color of materials can change under external stimulation, such as electric field, thermal field and light field. The reversible fluorescence modulation based on the chromic effect could expand the applications. In this paper, the reversible modulation based on chromic effect under electric field, thermal field or light field stimulation in inorganic rare-earth luminescent materials and their applications were mainly reviewed.Keywords：inorganic rare-earth luminescent materials;fluorescence modulation;electrochromic;thermochromic;photochromic- 2646
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Published：2022-04-20
Cover Story
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Amplification in E Band Based on Highly Phosphorus and Bismuth Co-doped Silica Fiber Enhanced Publication
Abstract：The low-loss bismuth- and highly phosphorous-co-doped silica fiber(BPDF) was prepared by the modified chemical vapor deposition technology combined with the solution doping method, where the mole fraction of phosphorous was as high as 7.2% and the background loss was 18 dB/km@1 550 nm. We used the tunable Raman laser operating at ~1 240 nm to pump the homemade BPDF, and achieved a broadband amplification in the range of 1 355 nm to 1 380 nm. The proposed BPDF amplifier provided the maximum gain of 5.18 dB at 1 355 nm. To our knowledge, this is the first report on the realization of low-loss BPDF fabrication, and the broadband amplification in the near-infrared band using the homemade BPDF in China.Keywords：highly phosphorus and bismuth co-doped silica fiber;broadband amplifier;fiber optics- 595
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Published：2022-04-20
Research Letter
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Progress of Luminescent Behaviors of Mn2+-Mn2+ Pair with Magnetic Coupling Interaction Enhanced Publication
Abstract：Transition metal ion Mn2+ doped semiconductors/insulators as luminescent materials have found significant applications in the fields of light-emitting diodes and displays. Due to the five unpaired electrons of Mn2+and normally the high-spin state when used as dopants in luminescent materials, the exchange or superexchange interaction, i.e., magnetic interaction, should easily take place between Mn2+ ion and the nearest neighbor Mn2+ ion. The interaction can generate a strong binding force at the molecular scale to the spin of electrons, making the luminescent behaviors of Mn2+-Mn2+ pair different from that of isolate Mn2+, like the shortened decay lifetime, abnormal redshift/blueshift of the emissions, multi-band emissions and unusual magneto-optic behavior. However, the confirmation and assignment of magnetic interaction in Mn2+-Mn2+ pair and its effect on luminescence behavior is still controversial because of the interference effects of concentration quenching, defect, phonon coupling, energy transfer, the sp-d exchange coupling between Mn2+ ions and exciton and the limitation of testing instruments. With the deepening of research and the introduction of some new techniques(like the photomagnetism measurement), the above issues can be partly solved. This review firstly introduces the fundamental theory and knowledge of magnetic interaction between transition metal ions. Then the effects of magnetic interaction of Mn2+-Mn2+ pair on the absorption spectra, emission spectra, decay lifetime, and magneto-optical effect are reviewed. The virous measurement methods were emphatically compared and discussed to prove the existance of magnetic interaction in Mn2+-Mn2+ and assign the type of interation. Finally, summary and some outlooks are given,concerning the potential applications of such materials in the field of LEDs devices.Keywords：Mn2+;magnetic coupling interaction;luminescence- 592
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Published：2022-04-20
Invited Review
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Optoelectronic Properties of InP/ZnSe/ZnS Quantum Dots with Different ZnSe Shell Layer Thicknesses Enhanced Publication
Abstract：Indium phosphide(InP) quantum dots(QDs) have drawn much attention in quantum dots light-emitting diodes(QLED) owing to their heavy-metal-free components and outstanding optics and electricity properties. In this paper, green InP/ZnSe/ZnS QDs were prepared with ZnSe and ZnS as the shell layers, QDs with various luminescence properties obtained by regulating the thickness of the ZnSe shell layer. When the mass ratio of Se powder to Zn(St)2 is 1∶15, the PL peak of InP/ZnSe/ZnS QDs is 522 nm, the half-peak width is 45 nm and the PLQY is as high as 86%. QLED based on different thicknesses of ZnSe shell layers was prepared, the residual organic solvent in the QDs films was removed by vacuum evaporation to avoid the destruction of QDs performance by high temperature annealing, and the best EQE of 2.2% was obtained for the QLED devices.Keywords：Indium phosphide quantum dots;fluorescence quantum efficiency;light emitting diode- 240
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Published：2022-04-20 -
1.5 μm Laser Properties of Large Mode Field Er3+/Yb3+ Co-doped Microstructured Fiber Cone Enhanced Publication
Abstract：The waveguide structures of large-mode-field double-cladding microstructured optical fiber and fiber cone were designed by the full vector finite element method. The microstructured optical fiber with the composition of 45Bi2O3-29GeO2-15Ga2O3-10Na2O-1CeO2 has been prepared by the cluster drawing method. Moreover, the fiber's core diameter is 70 μm, the inner cladding duty cycle is 0.25, and the mode field area is about 3 014.8 μm2. The fiber cone with a core diameter of 17.5 μm and an effective mode field area of 206.47 μm2 was prepared by using the fused biconical taper technology. The laser characteristics of the fiber and its cone were studied under 980 nm LD pumped. The results show that the central wavelength of the excitation spectrum of fiber drifted from 1 550.2 nm to 1 546.9 nm after tapering. And the output laser beam quality factor M2 of fiber and fiber cone decreased significantly from 3.45 ± 0.03 to 1.16 ± 0.01. The slope efficiency of fiber and fiber cone reaches 10.29% and 9.70%, respectively. The results indicate that the taper can effectively improve the laser output mode of microstructured optical fiber, and the laser output of fiber cone has good single model characteristics. Fiber taper technology provides a new approach for preparing large-mode-field and high-power laser fiber materials.Keywords：Er3+/Yb3+ co-doped;microstructure fiber taper;mode field;1.5 μm laser characteristics- 251
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Published：2022-04-20 -
Synthesis and Performance of Bipolar Green Phosphorescent Host Material Based on Imidazopyridine Enhanced Publication
Abstract：High-performance phosphorescent organic electroluminescent devices rely on host materials. Compared with normal host materials, bipolar host materials can not only reduce driving voltage, improve current efficiency and power efficiency, but also accelerate carrier mobility and balance current carriers. Therefore, in this paper, two donor-acceptor type bipolar green host materials named 9-phenyl-3-(9-(4-(3-Phenylimidazo ［1,2-a］ pyridin-2-yl) phenyl)dibenzo ［b,d］ furan-2-yl) -9H-carbazole(CzDFDp) and 9-Phenyl-3-(3-(9-(4-(3-phenylimidazo ［1,2-a］ pyridin-2-yl) phenyl) dibenzo ［b,d］ furan-2-Phenyl) -9H-carbazole(CzPDFDp) were developed by using 9-phenylcarbazole and dibenzofuran as the electron donor units, respectively, and imidazopyridine as the electron acceptor group. Their structures were characterized by HNMR. Photophysical studies show that CzDFDp and CzPDFDp have higher triplet states energy levels of 2.8 eV and 2.49 eV, the decomposition temperatures(Td, decomposition temperature at 5% loss) are 509 ℃ and 529 ℃, and the glass transition temperatures(Tg) are 130 ℃ and 138 ℃, respectively, indicating that it has good thermal stability and morphological stability, which is conducive to device evaporation and film formation. Therefore, GD-Ir-based doped devices using CzDFDp and CzPDFDp as host matrix exhibit low driving voltage(Von, 1 cd·m-2) of only 2.6 V, the maximum current efficiency of 44.9 cd·A-1 and 47.2 cd·A-1, and the maximum power efficiency of 50.4 lm·W-1 and 57 lm·W-1. Compared to device using the conventional host CBP(3.6 V, 14.4 cd·A-1, 5.8 lm·W-1), these two host materials-based devices show 1 V lower in the driving voltage, the current efficiency is increased by more than 3 times, and the power efficiency is increased by more than 8 times, indicating that these two novel bipolar host materials have good transmission properties and can effectively balance carriers, and are excellent green host materials.Keywords：bipolar host material;Imidazopyridine;green light;organic phosphorescen- 169
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Published：2022-04-20 -
Crystalline(phthalic acid)-induced Luminescence of Carbon Dots for White-light-emitting Diode Devices Enhanced Publication
Abstract：Obtaining simply C-dots-based solid-state fluorescent materials is profound in photoelectric field, yet it is still faced with the challenge to synthesize such material due to the serious quenching effect generated by aggregation of C-dots currently. Here, a pyrolytic route to rapidly synthesize sulfur(S), nitrogen(N)-codoped fluorescent carbon dots wrapped by the crystalline phthalate is reported. After optimizing the preparation conditions, the composite emits a dazzling orange-red fluorescence due to the crystal structured by phthalic acid precursor around the single C-dots during the formation of C-dots, and the formation of crystal creates a barrier to avoid the aggregation of C-dots. In addition, the emission of such composite is characteristic of the multipeaks due to the co-doping of sulfur and nitrogenelements, endowing it an advantage to fabricate white-light-emitting diode. As a result, it achieves a warm-white light with the correlated color temperature(CCT)~3 100 K, color rendering index(CRI)~82 at the chromaticity coordinates of (0.43, 0.40) combined with the commercial phosphors besides of the light emitting diode with an orange light, endowing such fluorescent nanomaterials broad prospect in the photoelectric industry.Keywords：C-Dots;sulfur and nitrogen co-doping;crystalline-induced;LED- 180
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Published：2022-04-20 -
Preparation and Luminescent Properties of ZnAl2O4/CaAl12O19∶Mn4+ Phosphors Enhanced Publication
Abstract：A series of xZnAl2O4/CaAl12O19∶Mn4+ (xZAO/CAO∶Mn4+) mixed-phase red-emit phosphors were prepared by traditional high-temperature solid-state method. The influence of ZnAl2O4 doping on the morphology and luminescence properties of CaAl12O19∶Mn4+ was investigated. The X-ray diffraction(XRD) characterization results show that the mixed-phase phosphors were successfully synthesized after sintered at 1 723 K for 6 h, and the two-phase coexistence is maintained with the increase of ZnAl2O4 doping amount. Fluorescence spectrum shows that ZAO/CAO∶Mn4+ has the largest fluorescence intensity when x=1, which is 203% higher than that of CaAl12O19∶Mn4+. Compared with CaAl12O19∶Mn4+ phosphor, the lifetime of ZAO/CAO∶Mn4+ is improved and internal quantum yield of ZAO/CAO∶Mn4+ is 211% higher than that of CaAl12O19∶Mn4+. An absolute sensitivity(Sa) of 4.32×10-3 K-1 of the ZAO/CAO∶Mn4+ phosphor was obtained in the range of 298-418 K and the maximum relative sensitivity(Sr) was 3.65×10-3 K-1 at 418 K, implying that it has potential application value in optical thermometry.Keywords：phosphor;optical thermometry;luminescent properties;Mn4+;ZnAl2O4/CaAl12O19- 207
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Published：2022-04-20 -
Preparation of n-type β-Ga2O3 Film with High Thickness by MOCVD Enhanced Publication
Abstract：High-thickness Ga2O3 film could increase the breakdown voltage of the device and it was generally prepared by HVPE. However, this method has some disadvantages such as the high cost and shortage of machines. In this paper, n-type β-Ga2O3 film with high thickness was prepared by metal-organic chemical vapor deposition(MOCVD) process on the Ga2O3 substrate with SiH4 as the n-type doping source and the influence of SiH4 flow on the properties of β-Ga2O3 was studied. The thickness of the β-Ga2O3 film prepared in the experiment reaches 4.15 μm. The crystal quality is high, and the surface of the film is dense and smooth and presents a step flow growth mode. As the flow of SiH4 increases, both the crystal quality and the electron mobility gradually decreases, while the electron concentration increases significantly. At present, the electron concentration of the high-thickness β-Ga2O3 film can be adjusted within the range of 3.6×1016 - 5.3×1018 cm-3; when the film electron concentration is 3.6×1016 cm-3, the electron mobility can reach 137 cm2·V-1·s-1. This article demonstrates the feasibility of growing high-thickness n-type β-Ga2O3 films by MOCVD process, which also provides a new way for the preparation of β-Ga2O3-based vertical structure power devices.Keywords：gallium oxide;metal-organic chemical vapor deposition(MOCVD);high-thickness film- 157
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Published：2022-04-20
Synthesis and Properties of Materials
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Research Progress of Graphene Based Photodetectors Under Different Response Mechanisms Enhanced Publication
Abstract：Photodetectors are widely used in video imaging, optical communication, biomedical imaging and motion detection since their ability of converting optical signals to electrical signals. The limited performances of traditional photodetectors are mainly due to the intrinsic properties of materials which they are made of, therefore, it is pressingly needing to find new materials for developing new photodetectors with superior performances. In recent years, the emerging two-dimensional materials have provided a whole category of novel material platforms for fabricating higher-performance detectors. Among them, graphene is one of the most promising candidate material for the next generation high-performance photonics benefiting its unique electrical, optical and thermal properties. In this manuscript, we have systematically summarized the research progress and status on the graphene based photodetectors according to their light response mechanisms, and followed by a concise future prospect on different graphene photoelectric devices.Keywords：graphene;photodetector;Response Mechanism;research progress- 362
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Published：2022-04-20 -
Single-layer Thermally Activated Delayed Fluorescent Organic Light-emitting Devices and Exciton Distribution Profiles Enhanced Publication
Abstract：Developing single-layer structure is important to simplify fabrication processes and reduce manufacture costs of organic light-emitting devices(OLEDs). In this work, we develop an efficient single-layer thermal activation delayed fluorescence(TADF) OLED by combining a non-doped TADF emitting layer, a C60(2 nm)/MoO3(3 nm)/C60(2 nm) modified ITO anode and a 4,7-Diphenyl-1,10-phenanthroline(Bphen, 3 nm) modified silver cathode. The single-layer TADF-OLED can achieve efficient hole and electron injection ability such that it has a low turn-on voltage of 3 V, a maximum current efficiency of 37.7 cd/A, a maximum power efficiency of 47.4 lm/W, and an external quantum efficiency of 13.24%. And then, we investigate the exciton distribution profile of the single-layer TADF-OLED by using a "probe" method. It is found that most excitons are formed at the emitting layer close to the anode. Finally, with the classical theory of electromagnetism, we simulate and analyze the outcoupling efficiency, and prove that this exciton distribution profile is beneficial to achieve higher outcoupling efficiency, and thus the external quantum efficiency of single-layer OLEDs.Keywords：single-layer OLED;thermal activation delayed fluorescence(TADF);exciton distribution profile;anode modified layer;outcoupling efficiency- 230
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Published：2022-04-20 -
Wide-ridge Waveguide Distributed Feedback 1.06 μm Semiconductor Laser with Lateral Microstructure Enhanced Publication
Abstract：In order to improve the lateral mode and spectral characteristics of wide ridge waveguide semiconductor laser, in this paper, a distributed feedback semiconductor laser with lateral microstructure ridge waveguide and high-order surface grating is proposed. In order to make the device have better lateral modes and narrow line width, two microstructure regions are introduced to both sides of the ridge waveguide. Due to the different optical field distribution of each order lateral modes, the introduction of microstructure regions increases the loss difference between the fundamental lateral mode and the higher-order lateral modes. Therefore, The "multilobe" phenomenon of far-field spot is eliminated, and the output power is improved. At the same time, with the help of high-order surface grating, the linewidth of the device is further narrowed. In the case of a ridge waveguide width of 50 μm and a cavity length of 1 mm, the high-order lateral modes are suppressed. The output power is increased by 16.4%, the slope efficiency is increased by 17.9%, the electro-optic conversion efficiency is increased by 15% and an output near the fundamental lateral mode at 0.6 A. Compared with the conventional semiconductor device, the spectral characteristics have been effectively improved, the spectral linewidth is about 39 pm.Keywords：semiconductor laser;high order bragg grating;lateral microstructure;lateral mode;narrow line width;far-field spot- 349
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Published：2022-04-20
Device Fabrication and Physics
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Color-tunable QLED Based on Mixed Quantum Dots and Its White-light Application Enhanced Publication
Abstract：A color tunable quantum-dot light emitting diode(QLED) with the structure of ITO/PEDOT∶PSS/TFB/Mixed-QDs/ZnO/Ag was fabricated by using red and green mixed quantum dots as the light-emitting layer, and the electroluminescence spectrum of QLED device was studied. The experimental results show that the QLED device has significant color tunability. With the increase of applied voltage, the QLED device presents a color change from dark red to orange and then to dazzling yellow-green. The QLED device exhibits a turn-on voltage of 2.0 V and the maximum brightness can reach 6×104 cd/m2. What's more, the device achieves a maximum current efficiency of 21 cd/A and a maximum external quantum efficiency of 7.5% at 31 934 cd/m2. As an application demonstration, we further combine the color tunable QLED device with GaN-based blue LED to prepare a white light emission. The results show that the color temperature of white light emission can be tuned from 3 568 K(warm white) to 10 269 K(cold white) and color rendering index is not less than 70, exhibiting great prospects in the application of lighting.Keywords：Quantum-dot light emitting diode;color tunable;white-light application;correlated color temperature- 215
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Published：2022-04-20 -
Progress on Modulation Bandwidth of Quantum-dot LED in Visible Light Communication Enhanced Publication
Abstract：As one of the wireless communication technologies, visible light communication(VLC) acts as a complement to radio frequency communication, and has attracted many researchers' attention in recent years. Except for electrical circuit designing and modulation mode designing in communication links, modulation bandwidth is one of the key factors to realize high-quality VLC. Different from traditional organic LEDs, polymer LEDs, and inorganic LEDs(such as GaN/InGaN LEDs), quantum-dot LEDs(QLEDs) show fast response, high color purity, high luminous efficiency, and they can realize photoluminescence and electroluminescence simultaneously. QLED is an ideal solid-state light source for VLC, however, literatures seldom report the mechanism of modulation bandwidth of QLED in VLC, especially the modulation bandwidth of multi-color QLED and electroluminescent QLED. Based on the light conversion mechanism of quantum dots, we systematically review the modulation mechanism of different QLEDs, and analyze the limitation of the modulation bandwidth of photoluminescence and electroluminescence QLEDs. This study lays the theoretical foundation for the application of QLEDs in VLC.Keywords：visible light communication;light-emitting diode;quantum dot;modulation bandwidth- 260
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Published：2022-04-20
Luminescence Industry and Technology Frontier
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Orthotopic Bladder Tumor Targeted Carbon Dots for Fluorescence Imaging-guided Phototherapy Enhanced Publication
Abstract：Bladder cancer has become one of the most frequent malignant tumors in the urinary system. Chemotherapy and radical cystectomy could not effectively cure this illness and even lead to side effects and low-quality life, which seriously threaten the lives of patients. Phototherapy provides a new method for bladder cancer treatment. Here, multifunctional carbon dots theranostics was developed and modified by a bladder cancer-specific peptide(PLZ4). PLZ4-carbon dots(PCDs) integrate targeted delivery, photodynamic therapy(PDT), and photothermal therapy(PTT) in one procedure. In vitro fluorescence imaging revealed that PCDs tend to aggregate in tumor cells than in normal cells, thus allowing them to effectively ablate MB-49 bladder cancer cells under a 635 nm laser. In vivo biodistribution showed that the PCDs specifically accumulated in bladder cancer tissues but exhibited negligible fluorescence in normal bladder tissues. After combined PDT/PTT, the orthotopic bladder tumor can be completely killed, thereby proving that PCDs have a potential as a candidate for bladder cancer treatment.Keywords：Carbon dots;phototherapy;orthotopic bladder cancer;targeted tumor therapy- 222
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Published：2022-04-20 -
Preparation of Switchable ZnO-NH2 QDs Fluorescent Probe and Its Application in Specific Detection of Cu2+ Enhanced Publication
Abstract：In this paper,a kind of fluorescence stable ZnO-NH2 QDs was prepared by sol-gel method. ZnO-NH2 QDs were characterized by UV-visible spectroscopy(UV-Vis), Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS), and fluorescence(PL). Based on the dynamic fluorescence quenched of ZnO-NH2 QDs by Cu2+ and the mechanism that Cu2+ can react with o-phenylenediamine(OPD, a non-fluorescent substance) to form 2, 3-diaminophenothiazine (DAP) with yellow fluorescence, a fluorescent probe for ZnO-NH2 QDs with specific recognition of Cu2+ and a ZnO-NH2 QDs+Cu2++OPD fluorescence sensing system were developed. The probe detected Cu2+ over a linear range of 40-9 000 nmol/L with detection limit of 3.93 nmol/L. The recovery rate of standard addition ranged from 98% to 100.58% in tap water, and that was 97.43% to 101.47% in Liujiang water. The experimental results show that the probe has good selectivity and accuracy for Cu2+, which can provide a new idea for the fluorescence rapid detection of Cu2+ metal ions.Keywords：ZnO quantum dots;switchable fluorescence probe;Cu2+- 158
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Published：2022-04-20
Luminescence Applications and Interdisciplinary Fields
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