Table of Content

15 January 2025, Volume 54 Issue 1

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Review

Research Progress on the Growth of Large-Sized CsPbBr₃ Crystals by the Melt Method

TANG Jia, SUN Zhicheng, ZHANG Zubang, LUO Hui

2025, 54(1):  1-10.  doi:10.16553/j.cnki.issn1000-985x.2024.0187

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All-inorganic halide crystal CsPbBr₃ has gained significant attention due to its outstanding high-energy ray resolution capability and excellent environmental adaptability. However, due to the presence of structural phase transitions and thermal stresses, stress is prone to arise during the growth process of large-sized CsPbBr₃ crystals, leading to defects such as cracks on the crystal surface, subgrain boundaries and twin crystals. These defects have severely impact on the performance of CsPbBr₃ crystals. Currently, large-sized high-quality CsPbBr₃still can't be mass-produced through effective means, restricting its further application. Hence, conducting research on the growth and performance of large-sized CsPbBr₃ crystals holds great theoretical significance and practical value. This paper briefly summarizes the fundamental properties, crystal preparation methods and research progress of CsPbBr₃ crystals, mainly discussing the influencing factors of the vertical Bridgman growth method, and proposing novel optimization ideas for the growth of high-quality CsPbBr₃ crystals.

Research Articles

High Rate HVPE Growth of High Uniformity 6-Inch GaN Thick Film

XU Wanli, GAN Yunhai, LI Yuewen, LI Bin, ZHENG Youdou, ZHANG Rong, XIU Xiangqian

2025, 54(1):  11-16.  doi:10.16553/j.cnki.issn1000-985x.2024.0227

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Gallium nitride (GaN) is an ideal semiconductor material for the development of microelectronic and optoelectronic devices. Homo-epitaxial growth on high-quality GaN single crystal substrates is the fundamental way to achieve high performance of GaN-based devices. Hydride vapor phase epitaxy (HVPE) is currently a most common approach for manufacturing the vast majority of commercially available GaN substrates. Owing to its high growth-rate, how to control the growth of HVPE-GaN with high growth-rate and high uniformity is of great significance for obtaining large-size high quality GaN substrates. Here, HVPE equipment for 6-inch GaN substrate is designed and developed independently. The effect of growth conditions such as the distance between source gas and substrate (D), separator gas, HCl and NH₃ carrier gas flow-rates on the thickness-uniformity of as-grown GaN films have been studied with the help of numerical simulation and epitaxy experiments. Simulation and experimental results indicate that the self-developed HVPE system has the characteristics of high growth-rate and high thickness-uniformity. The introduction of separator gas and increasing D can effectively promote the diffusion of GaCl gas to the edge of substrates, so as to significantly improve the thickness-uniformity of the large size epitaxial thick films. By further optimizing the growth conditions, 6-inch GaN film with a thickness of ~11 μm achieved thickness-nonuniformity about ±1.5% and growth-rate more than 60 μm/h. The growth-rate increases as the growth time increases. When the growth time is 3 h, the thickness of 6-inch GaN thick film is ~700 μm, the growth rate increases to >200 μm/h and the thickness-nonuniformity is still in the range of ±5%. The corrosion effect of non-reactive HCl on the deposited GaN on the quartz tube wall may lead to the increase of GaCl concentration and thus increase the growth rate. The results will help us to design the large-size HVPE growth system and prepare large-area and high quality GaN substrates.

Multi-Physics Field Modeling and Optimization of Large-Size Czochralski Silicon Single Crystal Growth

LIN Haixin, GAO Dedong, WANG Shan, ZHANG Zhenzhong, AN Yan, ZHANG Wenyong

2025, 54(1):  17-33.  doi:10.16553/j.cnki.issn1000-985x.20241022.001

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With the rapid advancement of the photovoltaic and semiconductor industries, the trend towards producing larger diameter (12 inch and above, 1 inch=2.54 cm) silicon single crystal has become increasingly prominent. The Czochralski method, as a predominant technique for silicon single crystal production, is highly emphasized. However, during the growth of large-diameter, high-quality Czochralski silicon single crystals, the enlargement in both crystal diameter and crucible size significantly expands the melt volume, thereby intensifying the complexity of the thermal field, flow field, and stress field. The interaction between vortices, thermal buoyancy, and Coriolis forces induces substantial turbulence and causes fluctuations in the melt's flow velocity and temperature, leading to challenges such as uneven temperature distribution at the solid-liquid interface and complex thermal convection within the melt, which can impact the defect distribution within the silicon crystals. Therefore, how to control process parameters to achieve ideal silicon single crystals with large-diameter is of significant importance. This study established a two-dimensional axisymmetric global numerical simulation model for the preparation of 18-inch crystal silicon rods within a 40-inch thermal field, capable of real-time prediction, dynamic control, and optimization of process parameters to address delays and cost issues in actual production. The model takes into account the increased crucible depth and extended heat conduction path, and incorporates an additional bottom heater alongside the main heater. Using the finite element method, the effects of variations in crystal rotation speed, crucible rotation speed, and gas pressure on the thermal field and silicon single crystal growth were analyzed individually, including shape of solid-liquid interfaces, temperature gradient, value of V/G, oxygen concentration and defect distribution, etc. Through multiple simulation experiments, a set of optimal process parameters was identified: a crystal rotation speed of 15 r/min, a crucible rotation speed of 5 r/min, and a furnace gas pressure of 1 200 Pa, which can make the temperature gradient of solid-liquid interface smaller and the temperature distribution more uniform, effectively avoiding excessive turbulence. Crystal growth experiments and a series of tests show that thesilicon single crystal rods produced with the optimal process parameters obtained from the simulation can increase the crystallization rate to 87.44%. This set of optimal process parameters for the 18-inch silicon single crystal rods (including crystal rotation speed, crucible rotation speed, and furnace pressure) has been precisely optimized based on the complexities of the thermal and flow fields in the growth of large-diameter (12 inches and above) Czochralski silicon single crystals. These parameters are well-suited for large-diameter silicon single crystal growth but may require specific adjustments and validation for smaller diameters (such as 4, 6 or 8-inch), where differences in heat transfer and airflow disturbances must be taken into account. The digital model established in this study can accurately predict and optimize the growth process of large-size Czochralski silicon single crystal, and have practical application prospects.

Growth and Properties of Large Size Ultra High Purity Germanium Single Crystals

ZHAO Qingsong, NIU Xiaodong, GU Xiaoying, DI Juqing

2025, 54(1):  34-39.  doi:10.16553/j.cnki.issn1000-985x.2024.0228

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High purity germanium detectors have the advantages of high resolution, high detection efficiency and strong stability, and their applications are becoming increasingly widespread. However, the preparation of ultra high purity germanium single crystals, the key materials for high purity germanium detectors, is challenging due to the high purity and high quality requirements. The domestic technology for preparing ultra high purity germanium single crystals is still immature, and the quality of the prepared crystals is still not high enough. In this work, large size ultra high purity germanium single crystals were grown in hydrogen atmosphere using the Czochralski method and self-made equipment. The crystal properties were analyzed through low-temperature Hall measurement, dislocation measurement, and deep level impurity measurement. The results show that the net carrier concentration of the as-grown germanium crystals is less than 1×10¹⁰ cm^-3, the deep level impurity concentration is less than 4.5×10⁹ cm^-3, the dislocation density is less than 5 000 cm^-2, and the number of dislocation array is less than 3, which meet the requirements of ultra high purity germanium detectors. Finally, qualified crystals with a diameter of 85 mm and a length of 60 mm were obtained.

Influencing Factors of Performance of Nuclear Radiation Imaging Detector Based on MPPC Array

TAO Zucai, WANG Qiang, XIAO Xiong, SONG Baolin, ZHANG Wenqiang, LIU Shuangquan, HUANG Xianchao, DING Yuchang, XU Yang

2025, 54(1):  40-48.  doi:10.16553/j.cnki.issn1000-985x.2024.0180

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This paper employs YSO crystal arrays and MPPC arrays to construct a nuclear radiation imaging detector, investigating the key factors influencing the performance of MPPC array-based nuclear radiation imaging detectors, including front-end resistance networks, light guide thickness, and light guide edge cutting depth. Initially, through front-end electronics experiments, it is found that using symmetric charge division circuit (SCD) can improve image distortion issues and enhance signal-to-noise ratio. Subsequently, based on SCD, the impact of different thicknesses of light guides (0, 1.0, 1.5, 2.0, 2.5 mm) on imaging performance was studied.The results show that a thickness of 1.5 mm provides the best resolution. However, the edge pixels of the crystal array still cannot be distinguished. Lastly, building upon the 1.5 mm light guide, experiments cutting the light guide periphery to varying depths and insertingelectron spin resonance (ESR) reflective film demonstrats that complete cutting through with the addition of reflective film allows for clear distinction of edge crystal units.

Fast Preparation of Fe₃O₄@C Photonic Crystal Flexible Composite Films by Magnetic Field Assisted Method

WANG Zhiqiang, ZHANG Qi, LIANG Ying, WANG Wenxin, CHEN Qi

2025, 54(1):  49-58.  doi:10.16553/j.cnki.issn1000-985x.2024.0189

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In this paper, the Fe₃O₄@C nanoparticles were synthesized by hydrothermal method and then arranged into Fe₃O₄@C photonic crystal films by vertical deposition method, natural deposition method, and magnetic field assisted method, respectively. The vertical deposition method for preparing photonic crystal films is time-consuming, and the resulting films are non-uniform. Additionally, these films can only be adhered to specific substrate materials, making them difficult to separate. Natural deposition produces more uniform photonic crystal films, but the surfaces are prone to unevenness. Additionally, these films still adhere to the substrate material and forcibly separating them can cause the photonic crystal films to break. The magnetic field assisted method can not only make the Fe₃O₄@C nanoparticles arrange into bright structural colors in a short period of time, but also make the Fe₃O₄@C nanoparticles arrange into periodic ordered structures in the photocurable polyurethane acrylate. This prevents the photonic crystal from being exposed to the air, reducing interference from external factors and enhancing the stability of the photonic crystal. The resulting Fe₃O₄@C photonic crystal flexible composite films are uniform in thickness and smooth on the surface. Ultrasonic treatment of Fe₃O₄@C nanoparticles is essential to obtain bright structural colors. Only the Fe₃O₄@C nanoparticles which have been ultrasonic treated to remove surface impurities can be arranged into periodic ordered structures with the help of magnetic field to display structural colors. Magnetic field assisted method can reduce the preparation time of the photonic crystal flexible film to some extent. The photonic crystal flexible composite film prepared by the magnetic field assisted method is more uniform and smooth, which also improves the stability of photonic crystal. It is helpful to promote the application of photonic crystal in security anti-counterfeiting, camouflage coating, sensors, solar cells, biomedicine and other fields.

Design of THz Metamaterial Sensors Insensitive to Incidence Angle and Polarization

LI Xiangyu, HAN Hua, WANG Yang, YAO Xiayuan

2025, 54(1):  59-68.  doi:10.16553/j.cnki.issn1000-985x.2024.0183

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Common terahertz wave sensors work under normal incidence conditions to distinguish the device under test (DUT). However, if the excited terahertz wave is not normal incident, its discrimination linearity will be affected. In this paper, a symmetrical gear-shaped terahertz metamaterial sensor is proposed. The structure of the sensor consists of a surface gear shaped metal pattern and a polyurethane substrate. This design has high transmittance in the range of 0.2~1.2 THz, and when the incident angle of electromagnetic waves changes within the range of 0°~70°, the resonance point of the sensor changes very stably and is insensitive to the incident angle, which compensates for the current shortcomings of sensors and has good ability to resist the uncertainty of the incident angle. At the same time, this sensing unit is also insensitive to the polarization of the incident wave, which expands the application range of terahertz sensors. The mathematical relationship between the sensitivity S and the refractive index of the object to be tested is derived. The sensitivity of the sensor is tested by the liquids with different refractive indices as the measurands. The result shows that there is a good linear relationship between the change of resonant frequency and the refractive index of sample. The sensitivity of the sensor is between -0.28 to -0.13 THz/RIU, demonstrating superior performance.

Luminescent Properties of CaLa₂(WO₄)₄∶Eu³⁺,Sm³⁺ as Novel Red Phosphor for White LEDs

HUANG Qu, JIANG Hongxi, ZHOU Bo

2025, 54(1):  69-76.  doi:10.16553/j.cnki.issn1000-985x.2024.0196

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A series of red phosphors of CaLa₂(WO₄)₄∶Eu³⁺ and CaLa₂(WO₄)₄∶Eu³⁺,Sm³⁺ were synthesized by high temperature solid state method. The crystal structure, spectral properties, thermal stability, fluorescence lifetime, and color coordinates of the samples were analyzed by experimental equipment such as X-ray diffractometry and scanning electron microscopy, etc. The results show that the samples synthesized by doping Eu³⁺and Sm³⁺into CaLa₂(WO₄)₄did not contain impurity phases, and the crystal structure remains unchanged. Under the excitation of 394 nm, the CaLa₂(WO₄)₄∶Eu³⁺ phosphors exhibit the strongest red light emission at 615 nm, originating from the ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺. The optimal doping concentration is 0.09. After doping with Sm³⁺, the emission peaks enhance, and the lifetime of the phosphors significantly increases. Sm³⁺ exhibits a sensitizing effect on Eu³⁺. In the co-doped system, energy is transferred from Sm³⁺ to Eu³⁺. For CaLa₂(WO₄)₄∶Eu³⁺,Sm³⁺, as the temperature increases, the integrated area of the ⁵D₀→⁷F₂ transition emission of Eu³⁺ gradually decreases; when the temperature rises to 100 ℃, the luminescence intensity become 53% of the initial temperature, indicating the occurrence of temperature quenching. In the co-doped system, the color coordinates move towards the red light region as the doping amount of Sm³⁺ increases. When the doping amount of Sm³⁺ is 0.02, the corresponding color coordinate is (0.645 8, 0.353 8). Based on the characteristics of CaLa₂(WO₄)₄∶Eu³⁺,Sm³⁺ phosphors, it can be used as potential red phosphors for white LEDS.

Electronic Structure and Optical Property of 4d Transition Metal Doped Monolayer WS₂

ZHANG Ningning, YU Haitao, LIU Yanyan, XUE Dan

2025, 54(1):  77-84.  doi:10.16553/j.cnki.issn1000-985x.2024.0238

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With the unique physical and chemical properties, WS₂ shows great potential for applications in the fields of electronics and optics. Based on the first-principles calculations of density functional theory, the aim of this paper is to investigate the electronic structure and optical properties of single 4d transition metal atoms X (X=Nb, Mo, Tc, Ru, Rh, Pd) substitutionally doped monolayer WS₂. The results show that the transition metal atoms doped WS₂ systems are all exothermic and stable, and the decrease of the band gap width leads to the enhancement of conductivity and significant changes in electronic structure. For these doped metal atoms, Nb doped WS₂ exhibits metallicness, Ru doped WS₂ exhibits semi-metallicness, and Tc, Rh and Pd doped WS₂ induce magnetism. The dielectric constant and optical refractive index of Nb, Ru, Rh and Pd doped WS₂ systems increase. The WS₂ systems before and after doped have good transparency characteristics, and the absorption spectrum is red shifted. The absorption of Nb, Ru and Rh doped WS₂ is enhanced in the infrared region, and the absorption of Nb, Rh and Pd is enhanced in the visible region. Especially, the Pd doped WS₂ has the best absorption effect in the visible region, which has a certain potential for application in thephotodetector.

Influence of Cations on the Structural Framework and the Origin of Birefringence in X₂(PO₄)₂ (X=Ba, Pb) and XPO₄ (X=Y, Bi)

WANG Yunjie, HE Zhihao, DING Jiafu, SU Xin

2025, 54(1):  85-94.  doi:10.16553/j.cnki.issn1000-985x.2024.0190

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Based on density functional theory, a systematic investigation of the geometric structure, electronic structure, and optical properties of Ba₃(PO₄)₂, Pb₃(PO₄)₂, BiPO₄, and YPO₄, which are composed of P—O coordination tetrahedra with Y, Ba, Pb, and Bi, has been conducted. The research indicates that the substitution of metal atoms can alter thestructural framework of compound, thereby regulating its band gap and optical properties, providing an effective approach for designing materials with excellent comprehensive performance. All four compounds are indirect band gap materials with relatively wide band gaps, with band gaps of 5.188, 3.879, 3.870, and 4.886 eV for Ba₃(PO₄)₂, Pb₃(PO₄)₂, BiPO₄, and YPO₄, respectively. According to Mulliken population analysis, the cations Ba, Pb, Bi, and Y form O—X (X = Ba, Pb, Bi, and Y) bonds with oxygen, which have similar bond lengths and exhibit strong ionic bond characteristics. The bottom of the conduction band in the four compounds is occupied by the outermost orbitals of the metal cation, and the main contributor to the top of the valence band is the O-2p orbital. The 2p orbitals of the oxygen atoms also exhibit strong localization near the Fermi level, and the P-3p orbitals bond with the O-2p orbitals, showing strong covalent P—O bonds. The birefringence of the four crystals Ba₃(PO₄)₂, Pb₃(PO₄)₂, BiPO₄, and YPO₄ are 0.003 7, 0.027 0, 0.059 0 and 0.149 0, respectively, with BiPO₄ and YPO₄ showing the highest birefringence and anisotropy among the four systems, which is due to the asymmetric crystal structural framework caused by different cations.

First-Principles Study on the Regulation of Optical Properties of Gallium, Indium, and Thallium Phosphates Through Sulfur Substitution

DING Jiafu, HE Zhihao, WANG Yunjie, SU Xin

2025, 54(1):  95-106.  doi:10.16553/j.cnki.issn1000-985x.2024.0193

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In this work, we present a comprehensive first-principles investigation to compare the phosphates GaPO₄, InPO₄, TlPO₄, and the thiophosphates GaPS₄, InPS₄, Tl₃PS₄, focusing on the [PO₄]^3- and [PS₄]^3- groups. Band structure calculations disclose that TlPO₄ possesses the smallest bandgap (E_g=0.788 eV), whereas InPO₄, GaPS₄, InPS₄ and Tl₃PS₄ exhibit larger bandgaps of 2.604, 2.352, 2.360 and 2.393 eV, respectively. GaPO₄ stands out with its notably large bandgap, which is 4.487 eV. The band structure of the [PS₄]^3- compounds is notably more predictable and adjustable. Density of states analyses indicate that in GaPO₄, InPO₄ and TlPO₄, the valence band maximum is primarily attributed to O-2p orbitals, while the conduction band minimum is a result of both the cation's s orbital and O-2p orbitals. Conversely, in GaPS₄, InPS₄ and Tl₃PS₄, the valence band maximum is dominated by the p orbitals of sulfur atoms, with the porbitals of phosphorus atoms in the [PS₄]^3- groups showing increase activity in the conduction band. The dielectric function analysis reveals that the peak values for both [PO₄]^3- and [PS₄]^3- compounds experience a redshift with the enlargement of the cation size, with the [PS₄]^3- compounds exhibiting a larger static dielectric constant compared to their [PO₄]^3- counterparts. Birefringence calculations at 1 064 nm show that GaPS₄ has the highest birefringence value (0.247), attributed to the sensitivity of its internal P—S bonds and Ga atoms to energy changes. The other compounds exhibit birefringence values of 0.017 (GaPO₄), 0.049 (InPO₄), 0.057 (TlPO₄), 0.022 (InPS₄), and 0.038 (Tl₃PS₄). Differential charge density and population analysis suggest that the optical effects and band structures of these six compounds are predominantly influenced by the [PO₄]^3- and [PS₄]^3- groups. Elastic modulus analysis concludes that the phosphates exhibit superior elastic properties over the thiophosphates, with indium-containing compounds showing enhanced mechanical stability and rigidity.

First-Principles Study on the Adsorption of SO₂ and CO on ReS₂ Surface

MO Qiuyan, ZHANG Song, JING Tao, WU Jiayin

2025, 54(1):  107-114.  doi:10.16553/j.cnki.issn1000-985x.20241030.001

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Using first-principles calculations based on density functional theory, we investigated the adsorption characteristics of SO₂ and CO molecules on ReS₂ material. Our study reveals the following key findings: compared to CO, SO₂ exhibits stronger interactions with ReS₂, resulting in a more compact adsorption geometry and higher adsorption energy. Differential charge density calculations further elucidate the electron transfer process from the ReS₂ surface to SO₂ molecules. This enhanced electronic density rearrangement at the adsorption interface provides a microscopic explanation for the high sensitivity of SO₂ detection. ReS₂ exhibits rapid desorption capabilities for SO₂ and CO at room temperature, making it a suitable sensing material for ambient SO₂ and CO detection. In summary, ReS₂ possesses the potential for use as a gas sensor and adsorbent material, facilitating the design of novel, high-performance technologies for gas pollution detection.

Synthesis, Structure and Hirshfeld Analysis of Zn Coordination Polymer Based on 1,3-Benzodioxole-5-Carboxylic Acid and 4,4′-Bipyridine

XU Yarong, ZHAO Jiuzhou, ZHAO Chengxiong, LIANG Yinong, SUN Zan

2025, 54(1):  115-120.  doi:10.16553/j.cnki.issn1000-985x.2024.0246

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A Zn coordination polymer [Zn(BDCA)(4,4′-bpy)_0.5]_n (I) was successfully synthesized by solvent thermal synthesis based on 1,3-benzodioxole-5-carboxylic acid (HBDCA), 4,4′-bipyridine (4,4′-bpy) and Zn(NO₃)₂. The structure was characterized by X-ray single crystal diffraction (SXRD), elemental analysis (EA), infrared spectroscopy (IR), thermogravimetric analysis (TGA) and X-ray powder diffraction (XRD). The results indicate that complex I belongs to the monoclinic crystal system, I₂/a space group, with lattice parameters of a=1.321 96 (11) nm, b=1.019 64 (9) nm, c=1.672 83 (14) nm and β=100.771 (6)°. The molecular formula is C₂₆H₁₈N₂O₈Zn. In complex I, the central Zn atom is located in a distorted tetrahedral geometry, and the ligand connects the metal to form a 1D chain structure. Hirshfeld analysis show that the chains can interact with each other through π…π stacking and C—H…O interactions to form a 3D supramolecular structure. In addition, the UV-vis diffuse reflectance spectra and solid-state fluorescence properties of complex I were also studied.

Preparation and Properties of a Cadmium Coordination Compound with 4,5-Imidazoledicarboxylic Acid

LI Miao, ZHENG Yimeng, SUN Yiting, MAO Yuling, ZHU Baili, CUI Shuxin

2025, 54(1):  121-125.  doi:10.16553/j.cnki.issn1000-985x.2024.0230

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The compound {[Cd(H₂IDC)₂(H₂O)₂]·2H₂O}_n (1) was synthesized via a hydrothermal method, utilizing 4,5-imidazoledicarboxylic acid (H₃IDC) and Cd(NO₃)₂·4H₂O as raw materials. Single crystal X-ray diffraction (SXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and fluorescence spectroscopy (FL) were employed to ascertain and elucidate the structure of compound 1. SXRD analysis reveals that compound 1 categorized under the P2₁/n space group of monoclinic crystal system. In compound 1, Cd(II) ions coordinate with H₂IDC^- anions and water molecules to form a six-coordinated octahedral configuration, which is further extended into a three-dimensional structure through hydrogen bonding. Fluorescence spectrum analysis at room temperature indicates that compound 1 exhibits the most intense emission peak at 598 nm when excited at a wavelength of 296 nm.

Cd(Ⅱ)-Based Fluorescent Sensing Organic Framework Constructed by Mixed Ligands and Its Performance

WANG Xinying, QIAO Decong, PAN Huibin, GAO Xia, LU Jiufu

2025, 54(1):  126-132.  doi:10.16553/j.cnki.issn1000-985x.2024.0181

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Under solvothermal conditions, using Cd(NO₃)₂·4H₂O as the metal source, pentamethylisophthalic acid (H₂MIP) ligand and 1,3-bis(2-methyl-1H-imidazol-1-yl)propane (BMIP) as mixed ligands, a novel Cd(Ⅱ) organic framework material {[Cd(MIP)(BMIP)]·2/3DMF}_n (SNUT-47) was constructed. X-ray single-crystal diffraction indicates that SNUT-47 exhibits a two-dimensional bilayer organic framework structure. The obtained complex was further characterized by powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and other techniques. The positions of the experimental and simulated diffraction peaks match well, indicating that the synthesized SNUT-47 material has excellent phase purity and reproducibility. Fluorescence experiments show that SNUT-47 possesses excellent fluorescence properties and exhibits a significant fluorescence enhancement effect for Na⁺ in aqueous solution, making it an efficient fluorescent sensor for the detection of Na⁺ with a detection limit of 2.56×10^-6 mol/L. Additionally, SNUT-47 can be easily recycled after cyclic experiments with just water washing, demonstrating good recyclability.

Tunneling Oxidation and Passivation Process of p-Type TOPCon Structure

GAO Jiaqing, QU Xiaoyong, WU Xiang, GUO Yonggang, WANG Yonggang, WANG Liang, TAN Xin, YANG Xinze

2025, 54(1):  133-138.  doi:10.16553/j.cnki.issn1000-985x.20241029.003

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In order to further investigate the preparation process and passivation performance of p-type TOPCon structure, experimental investigations were conducted on the effects of oxygen flow rate, oxidation temperature, and oxidation time on the quality of oxide layer during the growth of tunnel oxide layer. Additionally, the passivation performance and sheet resistance of p-poly at different boron diffusion temperatures were also examined. The experimental results demonstrate that increasing the oxygen flow rate to 15 slm (standard liter per minute) leads to an average hidden open circuit voltage of 730 mV, and a dark saturation current density as low as 3.5 fA/cm² for p-poly. Furthermore, when oxidation temperature is 620 ℃ and oxidation time reaches 30 min, the imply open circuit voltage increases to 735 mV. It is observed that both increasing oxidation temperature and extending oxidation time tend to stabilize the imply open circuit voltage. Moreover, when maintaining a boron diffusion temperature at 960 ℃, a sheet resistance value of p-poly remains at 132 Ω/□ while achieving a dopant junction depth of 0.25 μm in silicon. This configuration exhibits excellent passivation performance. The determined process parameters in this study enable the preparation of p-poly structures with superior passivation performance and provide valuable data support for future industrial applications involving P-type TOPCon structures in high-efficiency crystalline silicon cells.

Preparation and Energy Storage Performance of KNN-CZ Relaxation Ferroelectric Ceramics

PANG Guowang, ZHANG Pan, YIN Wei, YANG Yahong, MA Yabin, YANG Feiyu, MA Junliang, WANG Ping, QIN Yanjun, LI Ping

2025, 54(1):  139-145.  doi:10.16553/j.cnki.issn1000-985x.2024.0201

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Utilizing lead-free dielectric materials for mechanical energy harvesting and energy storage is an inevitable choice for environmental friendly energy storage devices. In this paper, (1-x)[(K_0.5Na_0.5)(Nb_0.9Sr_0.05Ta_0.08)O₃]-x(CaZrO₃) (KNN-CZ, x=0, 0.05, 0.07, 0.09) ceramics were prepared by solid-state reaction method, and their phase structure, microscopic morphology, dielectric and energy-storage properties were systematically studied. The results show that the KNN-CZ ceramics exhibit good relaxation and the P-E hysteresis lines are “thin”, which is due to the long-range ordered structure of KNN is destroyed by doping. Among them, 0.93KNN-0.07CZ has the best energy storage performance with effective energy storage density of 1.98 J/cm³, which is due to the higher energy storage efficiency (83.19%) and breakdown field strength (250 kV/cm) at x=0.07. The above results provide an environmentally friendly and promising material for ceramic capacitors.

Effect of Lithium Salt and Film-Forming Additives on the Low Temperature Electrochemical Performance of Lithium-Ion Batteries

JIANG Xiaoxue, SONG Fei, HU Guangyu, XU Jinhua, LI Cuiqin

2025, 54(1):  146-157.  doi:10.16553/j.cnki.issn1000-985x.2024.0195

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A low-temperature electrolyte was constructed with LiPF₆ as the lithium salt, LiDFOB+LiBF₄+LiPO₂F₂ as the lithium salt additives, fluoroethylene carbonate (FEC)+ vinylene carbonate (VC)+tris(trimethylsilyl) phosphae (TMSP) as the film-forming additives, and ethylene carbonate (EC)+dimethyl carbonate (DMC)+ethyl methyl carbonate (EMC) as the solvent, and was used to improve the low-temperature (-20 ℃) performance of NCM811 (LiNi_0.8Co_0.1Mn_0.1O₂) lithium-ion battery. The properties of low-temperature electrolytes were studied by various analytical techniques, and the effects of lithium salts and film-forming additives on the electrochemical properties of lithium-ion batteries were studied. The results show that the low-temperature electrolyte has good cycling stability and lithium deposition performance. Lithium-ion batteries assembled from low-temperature electrolytes have excellent low-temperature electrochemical properties. The first discharge specific capacity is 171.5 mAh/g at -20 ℃ and 0.1 C, and the capacity retention rate is 96.33% for 120 cycles at 1 C. The SEM and TEM results of the electrodes before and after cycling show that the low-temperature electrolyte form a uniform and dense CEI film on the surface of the positive electrode, due to the action of lithium salt and film-forming additives, which restrain the cracking of the positive electrode material and prevent the electrolyte decomposition, effectively improving the cycling stability of lithium-ion batteries at low temperatures.

Preparation of Ni-Doped Mo₂C/C Bifunctional Catalysts and Their Performance in Electrolytic Water Splitting

CHEN Hongming, FAN Shengqi, SONG Qi, JIANG Ling, CHEN Yongjun, LI Jianbao, ZHANG Xueyan

2025, 54(1):  158-164.  doi:10.16553/j.cnki.issn1000-985x.20241025.001

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With the increasing prominent global environmental issues and the depletion of fossil fuels, the search for renewable energy has become a daunting task. Hydrogen production by water electrolysis, which simultaneously generates hydrogen and oxygen through the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), is an efficient and green hydrogen production method, attracting the interest of an increasing number of researchers. However, currently commercial noble metal catalysts (Pt/C and RuO₂/IrO₂) are expensive and have limited reserves. Therefore, the development of high-performance, low-cost, and highly stable non-noble metal electrocatalysts has become a research hotspot. In this paper, a Ni@Mo₂C/C catalyst with three dimensions (3D) nanosheet structures was successfully prepared via a simple salt-template pyrolysis method. The composition, morphology and structure of Ni@Mo₂C/C material were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The elemental composition and valence states were analyzed using X-ray photoelectron spectroscopy (XPS), and the electrochemical performance of Ni@Mo₂C/C was investigated. The results indicate that at a current density of 10 mA·cm^-2, the overpotentials for the HER and OER of the Ni@Mo₂C/C catalyst are 47 and 232 mV, respectively. In the overall water splitting test, a voltage of only 1.61 V was sufficient to drive a current density of 10 mA·cm^-2, which could be sustained for 100 h.

Structure and Morphology Evolution of Heat Treated Goethite

HU Xuzhao, XU Xueyan, XU Bing, LIAO Shengwen, ZHANG Jiaqi, XIA Ailin

2025, 54(1):  165-174.  doi:10.16553/j.cnki.issn1000-985x.2024.0191

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The structure and morphology evolution of goethite (α-FeOOH) powder under high temperature heat treatments at 250～650 ℃ and 900 ℃ were studied by X-ray powder diffraction, thermogravimetric/differential thermal analysis, and scanning electron microscopy. The results indicate that no significant phase transformation occurs in goethite when calcined at 250 ℃ for 2~8 h. However, as the holding time increases, its acicular morphology gradually breaks down and stacks into short rod-like structures. When the calcination temperature reaches 350 ℃, α-FeOOH begins to dehydroxylate and transform into hematite (α-Fe₂O₃), and it completely transforms into the α-Fe₂O₃ phase at 450 ℃. When the calcination temperature reaches 450～650 ℃, although the product exhibits the α-Fe₂O₃ phase, it retains the original acicular morphology of α-FeOOH. As the heat treatment temperature and time increase, the average grain size of the product gradually increases. With heat treatment temperatures rising, α-Fe₂O₃ crystals grow larger, the specific surface area decreases progressively, sintering phenomena occur between particles, and when the calcination temperature reaches 900 ℃, the broken rod-like structure turns into rice-grain-like α-Fe₂O₃, which has certain application values in fields such as wastewater treatment, photocatalysis, and industrial pigments.