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Direct crystallization is widely used in the production of multicrystalline silicon. The efficient way for the silicon melt stirring control is to use magnetic fields. The paper provides the results of mathematical modeling of electromagnetic stirring of silicon melt under various conditions. Mathematical modeling was carried out using COMSOL Multiphysics software. In the course of modeling, the distributions of the magnetic field induction, the densities of the Lorentz force, and the melt stirring velocities were obtained. The distribution of the surface rate of the melt movement was determined. The experimental studies were carried out on a direct crystallization G5 unit. To create a running magnetic field, a current pulse generator was made. In the course of the study a physical and mathematical model of electromagnetic stirring of silicon melt was developed; a pilot unit was created and experimental studies were carried out; the optimal conditions for obtaining a stable, repeatable process of silicon melt stirring were established.

We demonstrate the impact of the intermediate hydrogen plasma treatment of intrinsic amorphous silicon layer in silicon heterojunction solar cells (SHJ). After deposition of the first layer of intrinsic amorphous hydrogenated silicon with a thickness of 5–6 nm hydrogen plasma treatment allows passivation of defects in the layer and, due to surface hydrogenation, creates conditions for defect-free growth of the next layer to a total thickness of 10 nm. The lifetime of minority charge carriers increases from 2 to 5 ms in comparison with base process. The parameters of hydrogen plasma treatment are determined, which makes it possible to increase the surface passivation quality by the layers of intrinsic hydrogenated amorphous silicon in the production of high-efficiency solar cells. The process is useful for fabrication of high performance SHJ solar cells.

The paper studies the issues for creating a monitoring system for electrical quantities, power supply schemes, wind speed and directions, and also photovoltaic module power in order to investigate the possibility of using wind and solar energy. Unlike many existing systems for measuring the parameters of power supply or electrical power generation by SCADA wind turbines, in the developed system fifteen measured values of electrical parameters averaged over a 10-second interval are accumulated in the database. As a research result the program for handling the database has been developed in order to obtain the values of any parameter averaged over any period of time and to construct a load diagram for any day of the year. The annual database contains about 50 million records of measured values. The maximum value of the power consumption to the average value for different periods of time has been determined. The identification of this relationship is important for the selection of inverters and batteries in case of changing the house power supply system to the stand-alone power supply based on wind and solar energy.

This paper presents the effect of the magnesium oxide film on the characteristics of a glow discharge with a metal film cathode based on the Cr-Cu-Cr composition. It has been found that for the mixture of Ne + 3% Xe at the pressure of 133 hPa the minimum value of the cathode fall of the glow discharge is (32.5±2) V. The onset of relaxation oscillations of the discharge current is established. The observed phenomena can be explained by the generation and dynamics of charging the magnesium oxide film.

Cu films are widely used in electronics for interconnections. In some applications, reliable thin-film connecting elements having high electrical conductivity, mechanical stability and adhesion to a glass substrate are required. In this case the length of the elements amounts to tens of centimetres. In this paper, Cu was used as the basis for the connecting elements. To ensure high adhesion Cr was used as an underlayer. The paper investigates the structure, electrical conductivity, adhesion, defect formation of Cu, Cu-Cr, Cr-Cu-Cr thin-film conductors. As a result of the performed research, the regularities of changes of the film structure, electrical conductivity, adhesion, defect formation depending on the technological process parameters were established. Physical and technological mechanisms determining the observed patterns are considered. The research results are used in the device production technology.

Currently, the main material for the production of solar cells is still silicon. More than 70% of the global production of solar cells are silicon based. For solar-grade silicon production the technologies based on the reduction of silicon from organosilicon compounds are mainly used. These technologies are energy-consuming, highly explosive and unsustainable. The present paper studies the technology of purification of metallurgical-grade silicon by vacuum-thermal and plasma-chemical treatment of silicon melt under electromagnetic stirring using numerical simulation and compares this technology with the existing ones (silane technologies and Elkem Solar silicon (ESS) production process) in terms of energy consumption, environmental safety and the process scalability. It is shown that the proposed technology is environmentally safe, scalable and has low power consumption. The final product of this technology is multicrystalline silicon, ready for silicon wafer production.

The paper evaluates the effectiveness of various parameters of the electromagnetic stirring of a silicon melt.

As a result of studies of a new gas-discharge current switch in a nanosecond voltage pulse generator, the megawatt power managed to achieve the following operating parameters. The pressure range when the device operated in the break current mode was 30 Pa - 45 Pa; the rise time range of the leading edge of the voltage pulse varied from 30 ns to 100 ns; the minimum recorded value of this parameter was 30 ns. The limit of the generator output voltage with the new device was 70 kV; the limit value of the switched current was 600A.

The paper presents the research results of 3D model of internal macrostructure of a multicrystalline silicon ingot obtained by directional crystallization method using high performance multicrystalline silicon technology. The 3D model is based on digital processing of signal images of photoluminescence intensity from the surface of wafers obtained from the investigated ingot. The purpose of the paper is the experimental study of the heightwise distribution of defect cluster areas in the silicon ingot. The study of the internal multicrystalline structure and the defect distribution in the course of the ingot crystallization using classical methods requires much time and destruction of the sample along the growth direction. This is unsuitable for the manufacturing process. In this paper, the results of the analysis of the defect distribution in the direction of silicon crystal growth are presented. The 3D model construction is performed using the MATLAB software environment.

The paper substantiates the composition and choice of a microgrid for settlements in the Central European part of Russia that are not connected to centralized public electricity networks. An economic analysis of microgrid costs in comparison with traditional methods of power supply (diesel, power lines) has been carried out. The economic advantages of using microgrid are shown both from the point of view of customers and the state in providing the availability of electricity for the population.

Funding Information: This work was supported by the Ministry of Education and Science of the Russian Federation in the frame of the state assignment FSSN-2020-0003. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. The performance characteristics (microhardness, porosity, roughness, and transient resistance) of Au–Ru coatings with and without the Co–W alloy barrier sublayer electrodeposited on the surface of contact blades of commercially produced reed switches were investigated. It was found that the barrier sublayer reduces the average roughness of the coatings without significant change in their porosity. The Au–Ru coatings without sublayer exhibited a greater variation in the transient resistance during an increase in the pressing force. The service time of reed switches with the barrier sublayer increased in both testing modes: in low-power (50 mV, 5 µA, 50 Hz) by more than 4 × 106 switching cycles, and in mean-power (12 V, 0.25 A, 50 Hz) by more than 1.8 × 106 switching cycles. publishersversion published

In this paper, we present the research results of plasma-chemical purification of metallurgical-grade silicon from boron and carbon under the conditions of electromagnetic stirring of silicon melt. The research is carried out by mathematical modeling using COMSOL Multiphysics software. The regularities between the process parameters and the efficiency of silicon purification from boron and carbon are established. The obtained data show that silicon plasma-chemical purification using electromagnetic stirring allows achievement of a purity level corresponding to the solar-grade silicon requirements.

The electrophysical (donor-acceptor) properties of the of glass carbon (GC) surface before and after its electrochemical modification in conditions of chemisorption of fluorine-containing nanogroups were studied using the methods of scanning probe microscopy. The values of the coefficients characterizing local (for atomic-scale) electrophysical properties of the surface are calculated on the basis of obtained local spectral dependences of the tunneling current on the tunnelling voltage. Fluorination of the GC surface resulted in change of the ratio of its donor-acceptor atomic characteristics, acceleration of electrode processes, and increase of the overall tunneling activity of local places.

Electrodeposition in pulse current mode of nickel-molybdenum alloy on a nickel substrate was studied. The range of current density variation from 2 to 9 A/dm2 was investigated. The range of pulse and pause step lengths is from tens to hundreds of milliseconds. SEM-images of applied coatings surfaces are obtained. The method of energy dispersive spectroscopy determined that the molybdenum content in the coating is 21-24 wt%. It was found that under transient pulse mode of electrolysis, with the pulse step corresponding to hundreds of milliseconds, the most rigid and smooth coatings of the electrolytic nickel-molybdenum alloy are obtained from ammonium-citrate electrolyte. It is shown that the percentage of nickel in the alloy does not depend on the electrolysis mode.

The present paper examines nanoporous material – carbon fabrics, which is used as electrodes in rechargeable energy storage capacitors (ultracapacitors). The fabrics structure, impurities composition, the influence of impurity types on ultracapacitor characteristics and the influence of thermal treatments on the impurities concentration are studied. The analysis of the ultracapacitor equivalent circuit with the studied material is made and the capacitor charge-discharge characteristics are investigated. The performed studies resulted in determination of the investigated carbon material structure, determination of impurities composition of carbon material and change of impurities content depending on thermal treatment in vacuum. The optimum temperature range for treatment in vacuum is established. The equivalent circuit of the ultracapacitor is analyzed and its charge-discharge characteristics are investigated. The chosen equivalent circuit makes it possible to estimate the influence of pores different size on the ultracapacitor charge-discharge characteristics that is important for its application in energy storage devices.

The influence of deep level defects lateral distribution in active layers of multicrystalline Si-based standard solar cells is investigated. Multicrystalline p-type Si wafers with 156×156 mm dimensions and 200 µm thickness were used for SCs preparation. One type of solar cells with conversion efficiency 20.4% was studied using capacitance voltage characteristics method (C-V) and by current deep level transient spectroscopy (I-DLTS). From various places along the diagonal of solar cell’s substrate with 20.4% efficiency nine pieces with an area ~20 mm2 were extracted and studied. I-DLTS spectra of the five pieces from solar cell were measured. The features of deep levels defects concentration lateral distribution along the SCs surface were studied.

It is known that n-Si solar cells have higher efficiency than p-Si solar cells. One of the problems connected with n-Si application for solar cell production is the difficulty of using Czochralski method for growing n-Si ingots, uniform in structure. The present paper examines the possibility of production of n-Si ingots, uniform in resistance, by neutron transmutation doping (NTD) for photovoltaics using the mathematical modeling method. The provided calculation data are obtained by MCU-RFFI/A accounting code with DLC/MCUDAT-1.0 constant library developed by «Kurchatov Institute» Russian Research Center. The MCU accounting code is used for solution of the neutron-transport equation by Monte-Carlo procedure on the basis of estimated nuclear data for arbitrary three-dimensional geometry systems. The present paper provides the estimation of uniformity of neutron-flux density along the ingot length and radius; dependence of silicon resistance on duration of irradiation. These studies established the neutron flux density distribution along the ingot length and radius; regularities of silicon resistance changes on duration and intensity of irradiation.

The paper presents the results of experimental research of a gas discharge current interrupter with a slotted configuration of holes and improved discharge parameters in a high-voltage pulse generator with inductive energy storage. The obtained results showed that in this device, in comparison with the analog, it was possible to reduce the average value of the turn-off time by 2.5 times, the range varied from 40 to 200 ns; the minimum turn-off time decreased by 4 times and was equal to 37 ns. The maximum amplitude of the pulse voltage was fixed at 85 kV, which exceeded the previously obtained value for a device with a slotted configuration by 20%. The increase of the peak pulse power to 24 MW, i.e by 70%, was achieved. The influence of the grid node temperature on the critical charge is shown.

The work presents the data of numerical modeling of silicon vacuum refining at different temperatures under electromagnetic stirring for purification of large volumes of silicon (≈500 kg). Time dependencies of the concentration decrease of impurities (P, Al, Ca, Zn, Na and Cu) at different rates of electromagnetic stirring and silicon melt temperatures are obtained. The influence of the silicon melt temperature on the purification efficiency rate is established. The numerical studies are performed by COMSOL Multiphysics.

The operating principle of magnetically controlled microelectromechanical system (MEMS) switches is based on controlling the beam movement under the influence of a magnetic field. Currently, there is a MEMS switch design with a flexible ferromagnetic electrode in the form of a fixed-terminal beam, with an electrode fastened on a straight or cranked anchor. The basic performance characteristics of magnetically controlled MEMS switches (service life, sensitivity, contact resistance, fast response) are largely determined by the flexible electrode design. To ensure the stable and controlled motion of the flexible electrode, it is necessary to provide the optimal design of a flexible electrode.

The paper presents the research results of formation peculiarities of barrier electrically insulated coatings based on titanium oxide (TiO2) under conditions of AC-DC electrochemical anodizing. It is shown that overlapping of AC component (at the frequency of 100 kHz – 10 MHz) leads to formation of coatings 1.2–1.4 times thicker. Dependences of the coating thickness on frequency under various ratios of the AC-component amplitude to the DC-component of anodizing voltage have been obtained.

The paper presents the research results of influence of various parameters of magnetic field concentrator geometry on sensitivity of magnetically controlled MEMS switches. It is shown that magnetic sensitivity increases with the growth of the magnetic concentrator width and practically does not depend on its length. It is established that dependence of magnetic sensitivity on the overlap length of the ferromagnetic flexible contact-concentrator has a minimum corresponding to 2-3 lengths of the contact gap. Recommendations on sensitivity increase of magnetically controlled MEMS switches are provided.

The paper presents the research results of formation features of nanoporous titanium oxide structure under electrochemical anodizing by AC-DC current. It is shown that addition of current AC-component (at the frequency of 100 Hz – 10 kHz) leads to increase of the coating formation rate and to structure quality changes of nanoporous TiO2 coatings: open intertubular space appears, intertubular bridges are formed and the nanotubes section form becomes round.

The present paper has suggested a new non-observational method to calculate electronic structure of carbynes taking into consideration the influence of the spin-orbital coupling. The method is demonstrated by calculations of the structure splitting at the Fermi level in cumulene and polyyne carbynes having semiconductor and metallic electronic structure correspondingly. These couplings result in 2 - 3 meV gaps.

The present paper contains results of the experimental researches of structure properties of the catalytic coating based on the nanoporous TiO2 film affected by corona-discharge plasma in air atmosphere under atmospheric pressure in the test system of needle-plane electrodes. Coating of the plate electrode was found to influence insignificantly on the discharge current-voltage characteristic, however if there is a coating on the plane electrode surface, an offset is observed towards lower currents under constant voltage at the gap. Obtained data on the surface morphology change shows that under negative corona erosion of the nanoporous TiO2 coating surface is practically absent and under positive corona, decrease of the coating thickness is observed.

The influence of deep level defects (DLs) on the conversion efficiency of multicrystalline Si-based standard solar cells (SCs) is investigated. Multicrystalline p-type Si wafers with 156×156 mm dimensions and 200 μm thickness were used for SCs preparation. Three types of SCs with conversion efficiency 10%, 16.8% and 20.4% were studied using capacitance voltage characteristics method (C-V) and by current deep level transient spectroscopy (I-DLTS). The correlation between the total concentration of DLs and the values of the SCs conversion efficiency is found.

The paper presents the results of modeling and development of a thyratron type grid node with improved discharge parameters of gas-discharge current interrupter for a high-voltage pulse generator with inductive energy storage. With the help of modeling, it is shown that the change in geometry of the holes in the grid assembly does not lead to the dropping of electrical strength index. Advantages of gas-discharge current interrupter with such a grid node in a high-voltage generator are described. 3D model of the fabricated grid assembly is shown. Comparative description of the developed grid node and existing analogs is given.

Silicon is the main material for solar cells production. The silicon growing technology improvement, its cost reduction is the important task for the development of photovoltaics. The paper presents the research results of electromagnetic stirring of silicon melt by mathematic modeling using COMSOL Multiphysics software. The effect of electromagnetic stirring under conditions of various configurations of an alternating magnetic field is investigated. The efficiencies of various configurations of stirring field are compared with the qualitative and quantitative characteristics of mass transfer within silicon melt. The interconnection between the parameters of electromagnetic stirring and the characteristics of the silicon flows induced by the field, as well as the rate of surface mass transfer of silicon melt is established. The research was carried out by mathematical modeling.

The paper presents the results of mathematical modeling of vacuum refining of silicon melt under the conditions of electromagnetic stirring. The results of calculations of the dynamics of silicon purification from impurities (e.g., P, Zn, Na) with high saturated vapour pressure at the temperature above the silicon melting temperature are presented. The effect of the electromagnetic stirring rate on the silicon purification rate is determined. Basic regularities and factors limiting the purification rate are shown. The research is carried out by mathematical modeling using COMSOL Multiphysics software.

Currently the improvement of stand-alone PV power systems characteristics, including increase of their service life is the actual direction of ground solar power development. The analysis of stand-alone PV power systems efficiency with the use of ultra capacitors is carried out by the means of mathematical modeling. The obtained data shows that the use of ultra capacitors as additional short-term energy storage devices in stand-alone PV power systems contributes to considerable increase of storage batteries lifetime and the total system operating time.

The paper presents an approach to the development of microgrid on the basis of renewable energy sources for settlements in the Central European part of Russia not connected to centralized electrical network providing comfortable level of the population living. The paper determines the annual power consumption and energy as well as firm capacity which are to be provided by microgrid. The optimum relationship of PV and wind power stations is determined; the structure of microgrid providing continuous power supply of a customer is determined.

The paper presents the research results of interaction of inert gas (argon) plasma jet containing chemically active impurity vapors with the surface of silicon melt under the conditions of its high turbulence to determine the optimal conditions for purification of silicon for solar cells. The interconnection between the plasma parameters (current, power) and the rate of surface mass transfer of the silicon melt is established. It has been found that under the conditions of the melt high turbulence the most efficient removal of impurities from silicon melt surface takes place. The research is carried out by mathematical modeling using COMSOL Multiphysics and Matlab software.

One of the major lines of solar energy development is the creation of environmentally friendly, wasteless, and cheap solar-grade silicon production technologies. Currently the main silicon production technologies are based on a reduction of silicon hydrogen chloride compounds: trichlorosilane, tetrachlorosilane, and monosilane. These technologies use environmentally dangerous and nonfireproof compounds in quantity. Such production levels can be profitable only in large volumes (more than 1000 tons per year). This chapter examines the research results of methods of silicon purification by extraction from a solid phase and plasma-chemical purification of metallurgical-grade silicon from impurities to the solar-grade level.

The paper presents the research results of energy, ecological, operational, economic and social efficiency of renewable energy (photovoltaic (PV) and wind power) and comparison results of renewable and traditional energy efficiency. It is established that wind and PV power stations are more effective, than thermal stations; their ecological efficiency is considerably higher, than that of thermal stations; the use of PV and wind power stations increases social stability.

One of the major lines of solar energy development is the creation of environmentally friendly, wasteless and cheap solar-grade silicon production technology. Currently the main silicon production technologies are based on reduction of silicon hydrogen chloride compounds: trichlorosilane, tetrachlorosilane, monosilane. These technologies use harmful and potentially dangerous compounds in quantity. These productions can be profitable only at big volumes (more than 1000 tons per year). The paper presents the research results of mathematical modeling and experimental research of metallurgical-grade silicon purification by the method of plasma chemical treatment of silicon melt up to solar-grade level with further direct crystallization in one reactor.

The beginning of the twenty-first century has been marked by quick growth of renewable energy sources market in the world, especially, in Europe. In Russia this market is extremely small; big energy projects with the application of renewable energy sources are absent. The present chapter provides the data on the potential of renewables in Russia; the analysis of the factors affecting the application of renewable energy sources.