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Issue 11 ， 2021
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Performance of A Single Phosphorus-doped β-Ga2O3 Microwire Solar-blind Ultraviolet Photodetector Enhanced Publication
Abstract：Recently, ultraviolet(UV) photodetectors have aroused the widespread concern of researchers around the world for their wide applications in UV radiation detection, missile warning, flame detection, ozone monitoring, and environmental monitoring. Most of the solar-blind photodetectors have been realized based on the wide bandgap semiconductor materials, such as ZnMgO, AlGaN, diamond and β-Ga2O3. Compared with these semiconductor materials, β-Ga2O3 is an emerging wide bandgap semiconductor that has attracted a large amount of interest due to its ultra-large bandgap of 4.9 eV in the solar-blind range, a high breakdown field of 8 MV/cm, and high thermal stability and chemical stability. In addition, the study shows that the impurity doping can significantly improve the electrical properties of β-Ga2O3 materials. In this paper, large-scale centimeter-level phosphorus-doped β-Ga2O3 microwires were grown by chemical vapor deposition method without any catalyst. The high purity Ga2O3, P2O5, graphite powders and O2 were used as the source materials and reactant gas for the microwires growth. The surface morphology, crystal structure and composition of the microwires were studied. It was found that the length of the microwire about was 0.6-1 cm and the diameter was about 40 μm. In order to study the UV sensing characteristics of photodetector, we fabricated a metal-semiconductor-metal(MSM) structure solar-blind ultraviolet detector based on a single phosphorus doped β-Ga2O3 microwires. The results show that both the undoped β-Ga2O3 microwires and phosphorus doped β-Ga2O3 microwires have good responses to 254 nm UV light, and the photocurrent value of the device made of the microwire with phosphorus content of 2.3% is the highest. Further photoelectric test of the phosphorus doped device shows that when the optical power is 550 μW/cm2, the photocurrent is 3.1 μA, the dark current is 1.56 nA, the photo-to-dark current ratio is about 2×103, the rise and fall time are 47 ms and 31 ms, respectively, and the responsivity reaches 2.8 A/W. When the optical power is 100 μW/cm2, the optical responsivity and external quantum efficiency of the device are the largest, which are 6.57 A/W and 3213%, respectively. Meanwhile, the UV detection mechanism of the device was studied.Keywords：chemical vapor deposition;phosphorus-doped;β-Ga2O3 microwire;UV photodetector- 1164
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Published：2021-11-23
Cover Story
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Current Status of Red and Near-infrared Emission Halide Scintillation Crystals Enhanced Publication
Abstract：In recent years, the technology of silicon-based photodetectors has developed rapidly, especially in avalanche diode and silicon photomultiplier tube, which present high quantum efficiency and high long-wavelength sensitivity. Therefore, the red and near-infrared luminescent scintillation crystals have been concerned. In this review, firstly, the development history of red and near-infrared emission halide scintillation crystals is summarized. Secondly, the scintillation properties and luminescence mechanism of Eu2+-Sm2+ co-doped metal halide scintillation crystals are described in detail, and the selection principle for excellent red and near-infrared luminescence material is also discussed. Finally, from the viewpoint of both material preparation and detector development, the problems for red and near-infrared scintillators are analyzed.Keywords：red and near-infrared luminescence;scintillation crystal;photoelectric conversion device;metal halide;nuclear radiation detection- 539
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Published：2021-11-23 -
Recent Advances in Rare-earth Doped Upconverison Materials with Thermally-enhanced Emissions Enhanced Publication
Abstract：Rare-earth doped upconversion materials generally feature serious thermal quenching as the temperature rising, which greatly limits their applications in optical thermometry, anti-counterfeiting, and display. Recently, unique thermal enhancement phenomenon of upconversion intensity has been detected by many groups, and great efforts have been devoted to revealing the mechanism and the influential factors. Meanwhile, the theoretical exploration and optimization of thermal enhancement effect open a novel and effective avenue for the rational design and applications of rare-earth doped upconversion materials. In this review, the recent advances in thermos-enhanced rare-earth ions doped upconversion materials are elaborately summarized from inner mechanism to possible applications, with the perspective and outlook in the emerging challenges in the future research.Keywords：Rare-earth doped luminescence materials;Thermal enhancement of luminescence;up-conversion;nano-particles- 950
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Published：2021-11-23
Invited Review
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Research Progress on Fabrication of Thin Black Phosphorus Materials and Its Optoelectronic Devices Enhanced Publication
Abstract：With the decrease of device size, traditional semiconductor materials will have thermal effect, size effect and other phenomena. These phenomena lead to the decline of the device performances and even the failure of the devices. To solve these problems, researchers are looking for new materials to replace traditional semiconductor materials. Black phosphorus is a p-type two-dimensional material with direct band gap and high carrier mobility, which has been extensively studied by researchers. This review first introduces the preparation methods of black phosphorus materials, such as mechanical exfoliation, liquid mechanical exfoliation, etc. Then, the application status of black phosphorus in solar cells, photodetectors, and field effect transistors is introduced. Finally, the prospect of black phosphorus materials in future is presented.Keywords：two-dimensional materials;black phosphorus;solar cell;photodetector;field effect transistor- 250
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Published：2021-11-23 -
Research Progress of Lead Halide Perovskite Nanocrystals Stabilized by Surface Coating Enhanced Publication
Abstract：Lead halide perovskite nanocrystals are emerging semiconductor materials in the past decade, exhibiting excellent optoelectronic properties, such as high photoluminescence quantum yield, narrow emission, tunable emission peak position, and high carrier mobility. They show great application prospects in the fields of solar cells, light-emitting diodes, lasers, and X-ray scintillators. However, lead halide perovskite materials easily undergo phase transformation or decomposition under the ambient conditions including water, light, and/or high temperature due to the inherent characteristics of perovskite ionic compounds. Stability is the biggest obstacle limiting the commercialization of perovskite nanocrystals. In recent years, many methods for stabilizing perovskite nanocrystals have been reported. In this review, the structures and the causes of instability of perovskite nanocrystals, as well as the strategies for forming composite materials to stabilize the nanocrystals by surface coating including macromolecule, inorganic matter, porosint, and heterojunction are summarized in detail. Some perspectives about the stabilization of perovskite nanocrystals are also proposed.Keywords：perovskite;nanocrystals;surface coating;stability;composite materials- 462
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Published：2021-11-23 -
Research Progress of Metal-organic Frameworks in Organic Perovskite Solar Cells Enhanced Publication
Abstract：Organic perovskite solar cells(OPSCs) have exhibited excellent power conversion efficiency, which is comparable to the monocrystalline silicon-based solar cells. But they still face the challenge of device stability due to the moisture and air sensitivities of organic perovskite materials. Metal-organic frameworks(MOFs) and their derivatives have open pore structure and large specific surface area. They can be used as additives in electron/hole transport layer, mixed perovskite MOF optical absorption layer, or as interface modification layer to effectively passivate the defects of perovskite absorption layer. In this way, the energy conversion efficiency and device stability of perovskite solar cells can be significantly improved. This paper introduces the related knowledge of MOFs and the research status of MOFs combined with OPSCs, focusing on the application and progress of MOFs in OPSCs in recent five years.Keywords：Photovoltaic technology;Metal organic framework materials;perovskite solar cells- 343
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Published：2021-11-23 -
Temperature Dependence and Evolution Mechanism of Aluminum Nitride Morphologies Enhanced Publication
Abstract：Aluminum nitride(AlN) is a significant ultra-wide bandgap semiconductor material. This paper studies the surface morphology evolution and growth mechanism of AlN grown on sapphire substrates by hydride vapor phase epitaxy(HVPE). The morphologies of AlN are controlled by the nitridation pre-treatment and the growth temperature from 750 ℃ to 1 100 ℃. The results show that growth temperature played a critical role in the AlN growth of morphology and growth mode. The difference in nanoscale or microscale morphologies of AlN is attributed to the surface migration of Al adatoms dominated by the growth temperature and the evolution of the dislocation. Moreover, the surface morphology evolution leads to an inverted pyramid morphology or large V-shaped pits at the growth temperature of 900 ℃. The grown V-shaped pits have {10-11} semi-polar facets and follow the three-dimensional(3D) growth mode. The semi-polar facets AlN structure could be used for realizing facet-controlled epitaxial of semi-polar UV-LED or other Ⅲ-nitride growth, which has prospects in optoelectronic and electronic devices.Keywords：Ultra-Wide bandgap semiconductor;Aluminum nitride;Hydride vapor phase epitaxy;Growth temperature;Surface morphology- 205
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Published：2021-11-23 -
Preparation and Electroluminescence Properties of CsPbI3/ZnO/GaN Nano-composite Structure Enhanced Publication
Abstract：Herein, ZnO nanowires and CsPbI3 nanostructures were prepared on p-GaN substrates by high pressure pulsed laser deposition and solution spin coating, sequentially. The structure, morphology and optical properties were investigated by X-ray diffraction, scanning electron microscopy and photoluminescence. The light-emitting diode(LED) fabricated with the nano-composite structure exhibited strong visible wide band light emission under forward bias, the electroluminescence(EL) spectrum consists of a blue peak at 440 nm, the yellow-green emission band at 500-650 nm and a red peak at 705 nm. With the increase of the injection current, the EL color of the device changes from nearly white to blue gradually, and with the decrease of the spinning speed of CsPbI3, the EL color of the device changes from blue light to yellow light gradually. At last, the EL mechanisms of heterojunction LEDs were discussed using the band diagram, and the reason why the emission spectrum of the device changes with the injection current and spin coating speed was explained. The CsPbI3/ZnO nano-composite can adjust the spectral color coordinates from blue to white, which provides a new way for single chip white LED.Keywords：ZnO nanowires;CsPbI3;electroluminescence;white light-emitting diode- 214
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Published：2021-11-23 -
Luminescence Properties of Pr3+ Doped in Ba3La(PO4)3 with Vacuum Ultraviolet and X-ray Excitation Enhanced Publication
Abstract：The radiative transition rate of Pr3+4f5d is large, which makes it as a promising luminescence center of fast scintillators. Samples of Ba3La(PO4)3(BLP) activated with Pr3+ were prepared through high temperature solid state method and characterized by XRD, temperature-dependent luminescence spectra upon VUV-UV and X-ray excitations and decay curves. Efficient and thermal stable Pr3+4f5d broad band emission with decay time of ~15 ns was observed. There is energy transfer from host to Pr3+4f5d upon excitation at 172 nm, however, the energy transfer is absent upon X-ray excitation which is attributed to influence of defects on surface. The results indicate that BLP∶Pr3+ could be applied as an efficient VUV to UV-C converting material. In addition, the research is also important for designing novel fast scintillators.Keywords：vacuum ultraviolet;Pr3+4f5d;energy transfer;decay curves;host luminescence- 240
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Published：2021-11-23 -
Effect of Ce3+ Doping on Upconversion Luminescence of NaYF4∶Yb3+,Tm3+ Nanoparticles and Application of Fluorescence Temperature Characteristics Enhanced Publication
Abstract：A series of Yb3+/Tm3+/Ce3+ co-doped NaYF4 nanoparticles with different Ce3+ contents were produced by solvothermal method. Strong upconversion blue fluorescence can be observed under 980 nm laser excitation. The influence of different Ce3+ content on the luminescence intensity was investigated. It was found that the upconversion luminescence from UV to visible enhanced firstly and then weakened with the increase of Ce3+ concentration when the mole fraction of Ce3+ increased from 0% to 0.5%. The fluorescence intensity reached the maximum at 0.2%, which was about 5 times stronger than that without Ce3+ doping, and the blue light at 475 nm was enhanced by 6 times. In addition, the mechanism was explored in detail. On the one hand, the cross relaxation between(3F3, 3H4) in Tm3+ and (2F7/2, 2F5/2) in Ce3+ occured after doping Ce3+, which effectively prevented the electron transition from going back to the ground state, resulting in the overall fluorescence enhancement. On the other hand, the (Yb3+- Yb3+- Ce3+) Trimers formed by doping Ce3+ transfered energy to 1G4 level and emitted 475 nm blue light, which led to strong blue light. When it was applied to the fluorescence intensity ratio thermometry measurement, the absolute sensitivity was as high as 0.035 0 K-1.Keywords：Ce3+ doped;upconversion luminescence;strong blue light;(Yb3+- Yb3+- Ce3+) Trimers;fluorescence intensity ratio thermometry- 759
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Published：2021-11-23 -
Optical Storage Characteristics of Sr2SiO4∶Eu2+,Dy3+ Enhanced Publication
Abstract：Sr1.994-xSiO4∶0.006Eu2+,xDy3+(x=0.001-0.006) phosphors were prepared by high-temperature solid-state reaction in a reducing atmosphere. The crystal structure and photoluminescence(PL) properties of Sr1.994-xSiO4∶0.006Eu2+,xDy3+ phosphors were investigated with X-ray diffractomer(XRD) and spectrophotometer. The PL spectra and photostimulated luminescence(PSL) spectra show that all the luminescence centers are derived from Eu2+ ions. Under the excitation of 320 nm and 365 nm, blue light emission centered at 470 nm and green light emission centered at 530 nm can be observed. The thermoluminescence test proved that the trap of Sr1.994-xSiO4∶0.006Eu2+,xDy3+ material is deep, and it is less affected by thermal disturbance at room temperature. Under the excitation of 800 nm infrared light, the trapped electrons are released and interact with holes in the luminescent center. After irradiated by 254 nm UV for 0.5 h, and stimulated with a 980 nm infrared laser, the phosphors exhibit obvious green PSL. The results show that Sr1.994-x-SiO4∶0.006Eu2+,xDy3+ has optical storage characteristics.Keywords：high temperature solid-state reaction;Sr2SiO4;photoluminescence;photostimulated luminescence;optical storage- 265
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Published：2021-11-23 -
Development of Single Molecular White Light Material Based on Rare Earth Europium Complexes Enhanced Publication
Abstract：In this paper, a novel white light material CRP4-Eu was developed by introducing rare earth europium complex with excellent red light into coumarin derivative with blue light. Since rare earth europium complex is mainly dependent on the energy transfer of the ligand 2-thienoyltrifluoroacetone(TTA), with a Stokes shift up to 274 nm, the absorption spectrum of rare earth europium has almost no overlap with the fluorescence emission spectrum of coumarin derivative with blue light, so that red light and blue light can be emitted simultaneously, and finally white light can be realized. The effect of excitation wavelength and concentration of CRP4-Eu on the luminescence color was investigated. It was proved that the CIE(Commission Internationale de L'Eclairage) coordinate of CRP4-Eu was (0.33, 0.35) when the concentration of CRP4-Eu was 30 μmol·L-1 and the excitation wavelength was 392 nm, which was close to that of pure white light(0.33, 0.33). This provides a basis for the further development of single molecular white organic luminescent materials.Keywords：white light material;coumarin;rare earth europium complex;single molecular white light- 179
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Published：2021-11-23 -
Ultrafast Electron Dynamics in Gold Films Probed by Near-infrared Femtosecond Laser Enhanced Publication
Abstract：Using ultrafast pump-probe technology, the ultrafast electron dynamics in gold films are investigated by near-infrared femtosecond laser. Transient reflectivity decrease after the 800 nm femtosecond laser excitation is observed. By analyzing and simulating the transient reflectivity spectrum difference, we found that it is mainly the result from the combined action of two kinds of electron dynamics: free electron relaxation and interband two-photon transitions. The two-temperature model is used to simulate the temperature relaxation and transient reflectivity difference, and the simulated results are in good agreement with the experimental results.Keywords：pump-probe technology;near-infrared femtosecond laser;gold film;ultrafast electron dynamics;transient reflectivity- 224
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Published：2021-11-23
Synthesis and Properties of Materials
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High-quality White Light Emission by Blue-green Organic Light Emitting Devices with Hybrid Color-conversion Layer Enhanced Publication
Abstract：The white organic light emitting diodes(OLEDs) were fabricated by employing DCJTB dispersed in PMMA as a color conversion layer(CCL) and pure blue and blue-green OLEDs as excitation sources. The results showed that the electroluminescence(EL) performance of the white OLED(WOLED) employing the blue-green OLEDs as the excitation source with the emitting layer structure of mCP∶Firpic(10 nm)/mCP(1 nm)/mCP∶4CzIPN(1.5 nm) was significantly better than that of the WOLEDs with the pure blue excitation OLEDs, which demonstrated maximum current efficiency(CE) and color rendering index(CRI), CIE coordinate and color conversion efficiency(CCE) of 15.44 cd/A and 77,(0.320 6, 0.369 5) and 52%, respectively. In order to further broaden the EL spectrum and increase the CRI, DCJTB and inorganic phosphor Sr2Si5N8∶Eu2+ were mixed in a certain ratio and dispersed in PMMA to fabricate a hybrid material for CCL, which was spin-coated on the backsides of the blue-green OLEDs at various speed. The results showed that the dopant Sr2Si5N8∶Eu2+ in the CCL will dramatically improve the CRI of the WOLED due to the broadening of the EL spectrum resulted from the red-shifting of the PL spectrum of doped CCL via the modulation of the CCL thickness. The WOLEDs with the optimal doped CCL thickness reveal optimal EL performance with the respective maximum CE, CRI, CIE coordinate and CCE of 11.29 cd/A, 82, (0.320 6, 0.369 5) and 34%, respectively, at the spin speed of 750 r/min.Keywords：organic light emitting diode(OLED);high-quality white light;hybrid color-conversion layer- 182
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Published：2021-11-23 -
O-band Single Longitudinal Mode Fabry-Pérot Laser Based on Double Slanted Slots Structure
Abstract：The re-growth free single longitudinal mode Fabry-Pérot(F-P) lasers based on etched double slanted slots have been achieved. Firstly, we have analyzed the resonant conditions for the F-P laser with a pair of etched slots, and the stably single longitudinal mode operation can be obtained when the slots are tilted with an angle of 4°. To investigate the effects of the slot widths on the device performance, the laser chips with various slot widths have been fabricated. It has been found that the best single mode performance has been realized of the laser chip with the slot width of 1.5 μm. And the quite stable single mode operation has been achieved with a side mode suppression ratio as high as 40 dB under a continuous-wave current injection of 70 mA for the laser. Under the test temperatures ranging from 20 ℃ to 75 ℃, the lasing wavelength shift rate for the slotted F-P lasers is only 0.12 nm/℃, which is much smaller than 0.6 nm/℃ for the lasers without slots. These results further confirm that a stable single longitudinal mode can be achieved by introducing slots in a F-P laser, which shows great potential for the application of optical communications.Keywords：F-P laser;etched slots;single longitudinal mode;optical communications- 166
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Published：2021-11-23
Device Fabrication and Physics
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A Novel Curcumin Derivatives Fluorescent Probe for Selective Recognition of Cysteine Enhanced Publication
Abstract：As an important sulfhydryl amino acid in organism, cysteine(Cys) is closely related to cell metabolism and redox homeostasis. However, excess amount of Cys is associated with diseases including rheumatoid arthritis, Alzheimer's disease. Thus, it is of great significance to develop a fluorescent probe for selective recognition of cysteine. In this paper, a fluorescence probe based on curcumin-difluoride and modified with 2-chloro-5-nitrobenzoyl was synthesized for the determination of cysteine. The results showed that the probe could selectively recognize Cys. A good linear relationship between the fluorescence intensity of the probe and Cys concentration in the range of 10-70 μmol·L-1 was obtained, from which the detection limit was deduced to be 2.9 μmol·L-1. Meanwhile, the addition of Cys could lead to an obvious colour transition from yellow to colourless, permitting a rapid identification of Cys by the naked eye. Moreover, the probe can simulate the detection of Cys in water samples, and the recoveries of Cys in tap water and river samples ranged from 98%-109%.Keywords：Cysteine;curcumin derivatives;fluorescent probe;selective recognition- 246
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Published：2021-11-23 -
Preparation of Pig Bone Nitrogen-doped Carbon Quantum Dots and Application in Detection of Co2+ Enhanced Publication
Abstract：Nitrogen-doped carbon quantum dots(N-CQDs) were successfully synthesized using pig bone and ethylenediamine as carbon and nitrogen sources by one-step hydrothermal method. Structure, optical properties and element composition of N-CQDs have been studied by transmission electron microscope(TEM), Fourier transform infrared spectroscopy(FT-IR), X-ray diffractometer patterns(XRD), UV-Vis absorption spectroscopy(UV-Vis) and X-ray photoelectron spectroscopy(XPS) technologies. The synthesized N-CQDs have a high quantum yield(26.4%), an average particle size of 2.34 nm, showing bright blue fluorescence under a 365 nm UV lamp. The study found that Co2+ had a good quenching effect on N-CQDs, so as to establish a new method for rapid detection of Co2+. The fluorescence quenching intensity of N-CQDs has a good linear relationship with the concentration of Co2+ at 0-15 μg/mL and 30-80 μg/mL, the detection limit is 20 μg/L, and the recovery rate of standard addition is 97.26%-109.14%, RSD<3.24%, which can be applied to the determination of Co2+ content in actual water samples.Keywords：nitrogen-doped carbon quantum dots;pig bone;fluorescence detection;Co2+- 226
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Published：2021-11-23
Luminescence Applications and Interdisciplinary Fields
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