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- 2019
- polycrystalline ferrite-garnet
- magnetoplasmonic crystals
- magnetooptical effects
- deposition
- ion-beam methods
- sputtering
- plasmon resonance
- Physics
- Moscow Technological University
- Moscow State University
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Recycling of silicon scraps by directional solidification coupled with alternating electromagnetic field and its electrical property
摘要： In this paper, alternating electromagnetic field and directional solidification are used to separate SiC and Si3N4 in polycrystalline silicon tailings. It is found the inclusion particles move downward at the center of the ingot and moving upward at the edge of the ingot by a variety of forces during the directional solidification process. The electromagnetic force accelerates the melt flow and enhances the lift force, so that larger particles can be pushed to the top of the ingot. Rod-shaped Si3N4 and block-shaped SiC particles show symbiotic relationship between each other. The aggregation of inclusion particles adsorbs metallic impurities, especially volatile metals, due to the effects of mushy region and short-circuit diffusion. The average conversion efficiency of the solar cells (Al-BSF method) prepared using the recycled silicon reached 18.56%, which meets the demand of the solar cells.
关键词： SiC,Alternating magnetic field,Directional solidification,Si3N4,Polycrystalline silicon
更新于2025-09-19 17:13:59
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22.6% Efficient Solar Cells with Polysilicon Passivating Contacts on n‐type Solar‐Grade Wafers
摘要： Czochralski (Cz)-grown upgraded metallurgical-grade (UMG) silicon wafers degrade signi?cantly during high-temperature processes, eroding their appeal as a low-cost alternative to conventional electronic-grade silicon wafers. However, the thermal degradation in UMG wafers can be delayed by utilizing a prefabrication annealing step. Based on this, a high-ef?ciency solar-cell process is modi?ed by selecting a single-boron diffusion step and applying phosphorus-doped polycrystalline ?lms as electron-selective contacts with excellent impurity-gettering properties to minimize the thermal budget. The application of this modi?ed high-ef?ciency solar-cell process to n-type UMG-Cz wafers results in a solar cell with a conversion ef?ciency of 22.6% on a cell area of 2 (cid:1) 2 cm2.
关键词： solar-grade silicon,polycrystalline contacts,ring defects,tabula rasa
更新于2025-09-19 17:13:59
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Assessment of power generation performance characteristics using different solar photovoltaic technologies
摘要： Solar energy is a relatively free renewable, clean, green, and environmentally friendly energy resource produced from the sun, using different technologies like solar thermal and photovoltaic (PV) modules to generate heat and electricity, respectively. This paper aims to assess and compare the power generation performance characteristics of different solar PV module technologies by simulation, deploying identical input temperature and irradiance parameters. The solar PV designs were simulated using PVsyst Version 6.73 for 26.0 kW annual power and 42.9 MWh/year annual yields using the climate data of Sydney, Australia. The results show that monocrystalline solar technologies needed an area of 163m2, while polycrystalline and thin films needed areas of 173m2 and 260m2 respectively to generate 42.9MWh annual yield. The monocrystalline PV modules are more efficient at solar energy conversion than polycrystalline and thin film technologies, respectively (94.2% and 62.7%). The symmetric semi-toroid dome of sun heights against azimuthal angles show 13 bimodal pyriforms, that cut the azimuths at least twice on each of the optimisation lines. These optimal solution points were visible for every sunlight hour of between 6 and 18 hours (inclusive). They show convex sets of global optima (or local optima) with one minimum in the interval of convexity. Also, each of the minimum points for each of the 13 directed fish-like bimodal pyriforms was on azimuth. However, the assessment of respective PV module characteristics with respect to variation of irradiation and temperature, show that the general results from simulation displayed disparate changes in the voltages and currents of the generated power with respect to different solar PV modules. The proposed semi-toroid model indicates that many optimisation solutions for easier, cheaper, quicker and more efficient power generation are possible with appropriate design. It is recommended that the installation of a single-axis solar tracker or maximum power point tracker could overcome the azimuth angle effect.
关键词： simulation,photovoltaic modules,polycrystalline,monocrystalline,thin film,solar energy,PVsyst,power generation,solar tracker,azimuth angle
更新于2025-09-19 17:13:59
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Performance Analysis of Submerged Polycrystalline Photovoltaic Cell in Varying Water Conditions
摘要： Exploring the underwater solar energy by solar photovoltaic (PV) cells leads to a huge advantage by utilizing the humongous space of water covered by the earth’s surface. Even though the amount of solar radiation decreases with the depth of the water, water provides sustainable cooling and cleaning for solar PV cells underwater. There are many challenges and constraints to develop solar PV cells underwater because they are mostly calibrated and amenable to space, dryland, terrestrial, etc., and the solar spectrum is prone to get narrower with the depth of the water. The implementation of solar PV cells underwater is pliable in various commercial and defense applications, such as sensors, water monitoring systems, autonomous vehicles, underwater gliders, etc. In this article, first, a mathematical model has been developed for the solar cell spectrum to incorporate the changes in the solar irradiance with the depth of the water. Furthermore, an experimental setup was designed and implemented to mimic an underwater environment. The performance of the polycrystalline encapsulated solar cell was studied based on the different types of water and the depth of the solar cell underwater. This article manifests that there is a sufficient amount of underwater solar power that can be utilized using PV cells to operate various devices and systems.
关键词： polydimethylsiloxane (PDMS),Photovoltaic (PV) cells,underwater solar power,polycrystalline solar cell,solar spectrum,water salinity,solar irradiance
更新于2025-09-16 10:30:52
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Intense red emission on dilute Mn-doped CaYAlO4-based ceramics obtained by laser floating zone
摘要： The laser floating zone (LFZ) technique was used to produce polycrystalline fibers composed by P21/c monoclinic Y4Al2O9 (YAM) and P?421m tetragonal CaYAl3O7 (CYAM) phases embedded into I4/mmm tetragonal CaYAlO4 matrix. The scanning electron microscopy and X-ray diffraction patterns put in evidence the strong effect of growth rate on the microstructural and phases’ evolution. Besides the microstructural and structural analysis, complementary optical techniques as photoluminescence (PL), PL excitation (PLE), and lifetime measurements were used to characterize the produced fibers. The nonintentionally doped fibers were shown to exhibit an intense deep red emission likely due to Mn4+ trace impurities. From the PLE measurements, average crystal field strength was estimated with Dq/B ~ 2.94. Temperature-dependent PL measurements revealed that the red luminescence is due to the overlap of transitions from the almost electronic degenerate 2E and 4T2 excited states to the 4A2 ground state. The emission from the two excited states arises due to the breakdown of the adiabatic approximation. The overall luminescence intensity of the red emission was found to decrease from 11 K to RT, and the internal quantum efficiency, estimated from the ratio of the integrated luminescence at high and low temperatures, was found to be 60%. Time-resolved spectroscopy indicates a single decay time of ca. 2.0 ms at room temperature, corresponding to the spin and parity forbidden 2E → 4A2 transition.
关键词： Laser floating zone,Crystal field strength,Polycrystalline fibers,Mn4+ trace impurities,Red emission
更新于2025-09-16 10:30:52
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Ultraviolet Nanosecond Laser Annealing for Low Temperature 3D-Sequential Integration Gate Stack
摘要： For the top tier in a 3D sequential integration, we propose a low temperature gate first approach in which an in-situ doped amorphous silicon layer is deposited at 475°C then subsequently converted into a polycrystalline film using ultraviolet nanosecond laser annealing. We demonstrate the ability to obtain a low resistance poly-Si gate for the top transistors within a thermal budget expected to preserve the bottom devices electrical performance.
关键词： Ultraviolet Nanosecond Laser Annealing,Polycrystalline Silicon,3D-Sequential Integration,Low Temperature Gate Stack
更新于2025-09-16 10:30:52
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Effect of laser texturing on the performance of ultra-hard single-point cutting tools
摘要： This paper investigates the cutting performance and anti-adhesive properties of textured single-point polycrystalline diamond (PCD) cutting tools in machining Aluminium 6082 alloys. The micro/nano textures were first milled using a fibre laser (1064-nm wavelength) at different power intensities, feed speeds and pulse durations, and finally characterised using scanning electron microscopy, white light interferometry and energy dispersive X-ray spectroscopy. The effect of different textures on the cutting performance was investigated in turning tests under dry cutting conditions. The test was stopped at regular lengths of cut to allow analysis of height of adhesion through 3D white light interferometry. The data processing of the cutting forces and the microscopical characterisation of the tested cutting tools enabled the evaluation of the effects of texture design, friction coefficient and adhesive properties. The results indicated that feed force in tools with grooves perpendicular to the chip flow direction (CFD) was more stable (20–40 N) than the benchmark (6–41 N). Similarly, the thrust force for tools with grooves parallel to CFD and grooves perpendicular to CFD showed a homogeneous trend fluctuating between 60 and 75 N as compared with the benchmark (ranging between 73 and 90 N). For texture depth in the order of 260 nm and post process roughness in the order of tens of nanometers, a reduction of average friction coefficient (0.28 ± 0.14) was reported when using lasered inserts with grooves parallel to the chip flow direction compared with the benchmark tools (0.34 ± 0.26) corroborated by reduced stiction of workpiece material on the rake face. In machining via textured tools with grooves perpendicular to CFD, the cutting forces were reduced by 23%, and the surface quality of the machined workpiece was improved by 11.8%, making this geometry the preferred choice for finishing applications. Using grooves parallel to CFD reduced the cutting forces by 11.76%, adhesion by 59.36% and friction coefficient by 14.28%; however, it increased the surface roughness of the machined workpiece, making this geometry suitable for roughing operations. For the first time, laser manufacturing is proposed as a flexible technique to functionalise the geometrical and wear properties of PCD cutting tools to the specific applications (i.e. roughing, finishing) as opposed to the standard industrial approach to use microstructurally different PCDs (i.e. grain size and binder %) based on the type of operation.
关键词： Adhesion,Dry cutting,Nanosecond pulse,Laser milling,Polycrystalline diamond insert,Laser surface texturing,Cutting forces
更新于2025-09-16 10:30:52
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Pixel Circuit With Leakage Prevention Scheme for Low-Frame-Rate AMOLED Displays
摘要： This work proposes a new pixel circuit for active-matrix organic light-emitting (AMOLED) smartwatch displays with a low frame rate. Within the long emission period, the leakage current of a low-temperature polycrystalline silicon thin-film transistor (LTPS TFT) is reduced to suppress the distortion of the driving voltage at the gate node of the driving TFT. Based on the measured electrical characteristics of a fabricated p-type LTPS TFT, the HSPICE model is established to verify the feasibility of the proposed circuit. The analytical results indicate that the relative OLED current error rates are all below 4.73%, as the threshold voltage of TFT varies by ±0.5 V. Notably, the OLED current varies by only 2.94% during the emission period of 66.7 ms at a medium gray level, demonstrating the effectiveness of the leakage prevention scheme.
关键词： low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs),Active-matrix organic light-emitting diode (AMOLED),leakage current prevention
更新于2025-09-16 10:30:52
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Silicon Powder-Based Wafers for Low-Cost Photovoltaics: Laser Treatments and Nanowire Etching
摘要： In this study, laser-treated polycrystalline Si (pc-Si) wafers, fabricated by wire sawing of hot-pressed ingots sintered from Si powder, have been investigated. As-cut wafers and those with high-quality thin Si layers deposited on top of them by e-beam have been subjected to laser irradiation to clarify typical trends of structural modifications caused by laser treatments. Moreover, possibility to use laser-treated Si powder-based substrates for fabrication of advanced Si structures has been analysed. It is established that (i) Si powder-based wafers with thicknesses ~180 μm can be fully (from the front to back side) or partly (subsurface region) remelted by a diode laser and grain sizes in laser-treated regions can be increased; (ii) a high-quality top layer can be fabricated by crystallization of an additional a-Si layer deposited by e-beam evaporation on top of the pc-Si; and (iii) silicon nanowires can be formed by metal-assisted wet chemical etching (MAWCE) of polished Si powder-based wafers and as-cut wafers irradiated with medium laser power, while a surface texturing on the as-cut pc-Si wafers occur, and no nanowires can form in the region subject to a liquid phase crystallization (LPC) caused by high-power laser treatments.
关键词： polycrystalline Si wafers,nanowire etching,photovoltaics,laser treatments,silicon powder
更新于2025-09-16 10:30:52
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Electrostatic self-assembly synthesis of ZnFe2O4 quantum dots (ZnFe2O4@C) and electromagnetic microwave absorption
摘要： Making effective usage of quantum size effect is a foregrounded strategy to design and fabricate excellent electromagnetic microwave absorption materials. In this research, ZnFe2O4 quantum dots were coated by hybrid amorphous carbon to form a sea islands structure by a facile electrostatic self-assembly synthetic technology. Simultaneously, the rejection of heterogeneous charges leads to the formation of quantum dots, by which the quantum size effects on dielectric and magnetic characteristic were investigated. Consequently, multiple hetero-interface and interfacial polarization was originated from polycrystalline feature of ZnFe2O4 with spinel and inverse spinel structures. In particular, the electromagnetic microwave absorption properties of ZnFe2O4 were greatly optimized, as the minimized reflection loss reached -40.68 dB at the frequency 11.44 GHz and thickness 2.5 mm, while the effective bandwidth corresponding was 3.66 GHz (from 9.87 to 13.52 GHz). The largest effective bandwidth was 4.16 GHz (from 8.08 to 12.24GHz) with a thickness of 3 mm. It is suggested that high performance of microwave absorption of ZnFe2O4 quantum dots was well guided by the optimized impedance matching and attenuation constants.
关键词： Electromagnetic microwave absorption,interfacial polarization,ZnFe2O4 quantum dots,polycrystalline,Electrostatic self-assembly
更新于2025-09-16 10:30:52