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The relevance of developing integrated lighting systems in conditions of unstable power supply via general-purpose networks is beyond doubt. This article discusses original technical solutions for LED modules that ensure system operation within a wide range of input supply voltages for direct and alternating currents. The effectiveness of the proposed circuit approach is demonstrated using the example of a developed LED lighting device with an electronic LED power system with a driver built using the concept of flyback topology, capable of working with input voltages of both direct (20…300 V) and alternating (36…300 V) currents. The results of experimental studies of electro-optical parameters and characteristics of the manufactured prototypes of the developed lighting systems are presented. It has been shown that the LED modules demonstrate a stable luminous flux and a high luminous efficiency (more than 150 lm/W) at various values and types of supply voltage. The developed lighting systems can be effectively used in domestic and industrial environments, including special-purpose facilities, namely, shelters and warehouses for various purposes, etc. [ABSTRACT FROM AUTHOR]

An expression for finding the dependence of narrowing the bands in silicon Eg on the level of illumination from the intrinsic absorption band (or short-circuit current) has been proposed. This expression is used to find experimental values of Eg in high-efficient silicon solar cells. The dependence Eg (J) or dependence Eg (JI), where JI is the shortcircuit current density, has been rebuilt into the Eg (nOC) dependence, where nOC is the excitation level in open-circuit conditions. With this aim, the generation-recombination balance equation was solved taking into account six recombination mechanisms in silicon, including Shockley-Reed-Hall recombination, radiative recombination, interband Auger recombination, surface recombination, non-radiative exciton recombination, and recombination in the space charge region. The latter two recombination terms are not taken into account in studies of the key parameters of silicon solar cells and in programs for simulating the characteristics of these solar cells. Therefore, in this work their correct definition was performed, their contribution was compared with the contribution of other recombination mechanisms, and it has been shown that the description of the characteristics and key parameters of silicon SC without taking them into account is insufficiently correct. The experimental dependences Eg (nOC) obtained in the work were compared with Schenk's theory. It has been shown that there is a good agreement between them. [ABSTRACT FROM AUTHOR]

Theoretical modeling of the optical and photovoltaic characteristics of highly efficient textured silicon solar cells (SC), including short-circuit current, open-circuit voltage and photoconversion efficiency, has been performed in this work. In the modeling, such recombination mechanisms as non-radiative exciton recombination relative to the Auger mechanism with the participation of a deep recombination level and recombination in the space charge region (SCR) was additionally taken into account. In a simple approximation, the external quantum efficiency of the photocurrent for the indicated SC in the long-wavelength absorption region has been simulated. A theory has been proposed for calculating the thickness dependences of short-circuit current, open-circuit voltage and photoconversion efficiency in them. The calculated dependences are carefully compared with the experimental results obtained for SC with the p + -i-α-Si:H/n-c-Si/i-n + -α-Si:H architecture and the photoconversion efficiency of about 23%. As a result of this comparison, good agreement between the theoretical and calculated dependences has been obtained. It has been ascertained that without taking into account recombination in SCR, a quantitative agreement between the experimental and theoretical light I-V characteristics and the dependence of the output power in the SC load on the voltage on it cannot be obtained. The proposed approach and the obtained results can be used to optimize the characteristics of textured SC based on monocrystalline silicon. [ABSTRACT FROM AUTHOR]

Crystalline Silicon (c-Si) remains a dominant photovoltaic material in solar cell industry. Currently, scientific and technological advances enable producing the c-Si solar cells (SCs) efficiency close to the fundamental limit. Therefore, combining the experimental results and those of modeling becomes crucial to further progress in improving the efficiency and reducing the cost of photovoltaic systems. We carried out the experimental characterization of the highly-efficient c-Si SCs and compared with the results of modeling. For this purpose, we developed and applied to the samples under investigation the improved theoretical model to optimize characteristics of highly efficient textured solar cells. The model accounts for all recombination mechanisms, including nonradiative exciton recombination by the Auger mechanism via a deep recombination centers and recombination in the space-charge region. To compare the theoretical results with those of experiments, we proposed empirical formula for the external quantum efficiency (EQE), which describes its experimental spectral dependence near the long-wave absorption edge. The proposed approach allows modeling of the short-circuit current and photoconversion efficiency in the textured crystalline silicon solar cells. It has been ascertained that the dependences of the short-circuit current on the open-circuit voltage and the dark current on the applied voltage at V < 0.6 V coincide with each other. The theoretical results, as compared to the experimental ones, allowed us to validate the developed formalism, and were used to optimize the key parameters of SCs, such as the base thickness, doping level and others. In this work, we have further generalized and refined the analytical approach proposed and used by us earlier to analyze high-efficiency solar cells and model their characteristics. [ABSTRACT FROM AUTHOR]

Short-circuit current, open-circuit voltage, and photoconversion efficiency of silicon high-efficiency solar cells with all back contact (BCSC) with planar surfaces have been calculated theoretically. In addition to the recombination channels usually considered in this kind of modeling, namely, radiative, Auger, Shockley-Read-Hall, and surface recombination, the model also takes into account the nonradiative trap-assisted exciton Auger recombination and recombination in the space charge region. It is ascertained that these two recombination mechanisms are essential in BCSCs in the maximum power operation regime. The model results are in good agreement with the experimental results from the literature. [ABSTRACT FROM AUTHOR]

A new approach to modeling the parameters of high efficiency textured silicon solar cells (SCs) has been presented. Unlike conventional optimization formalisms, our approach additionally includes such important factors as the non-radiative Auger recombination of excitons via deep impurity levels as well as electron-hole pairs recombination in the space charge region. A simple phenomenological expression offered by us earlier for the external quantum efficiency of the textured silicon solar cells with account of the photocurrent in the long-wave part of the absorption spectrum has been also used. Applying this approach, the key parameters of textured silicon SCs, namely: shortcircuit current, open-circuit voltage and photoconversion efficiency, have been theoretically determined. The proposed formalism allows calculating the thickness dependence of photoconversion efficiency, which is in good agreement with the experimental results obtained for the heterojunction SCs with the record photoconversion efficiency of 26.6%. The offered approach and the results of applying this phenomenological expression for the external quantum efficiency of the photocurrent in the long-wave part of the absorption spectrum can be used to optimize the characteristics of high efficiency textured SCs based on monocrystalline silicon. [ABSTRACT FROM AUTHOR]

The key parameters of silicon solar cells with back contact and rear metallization (SC-BC), such as the short-circuit current, open-circuit voltage, and photoconversion efficiency are modeled theoretically. Among other recombination channels, the model accounts for the non-radiative Auger recombination assisted by the deep recombination center and recombination in the space-charge region. It has been ascertained that these mechanisms are important in the typical commercial SC-BC in the maximal-power regime. The theory has been developed for calculating the efficiency as a function of the SC-BC thickness. Experimental and theoretical data agree well between each other. In particular, the theory has been applied to model the SC-BC produced by SunPower Corp. Depending on the surface recombination velocity on the illuminated surface and on the total surface recombination velocity on the front and rear surfaces, two mechanisms determine the optimal SC-BC thickness, at which the output power reaches its maximal. The first mechanism dominates, when the efficiency exceeds 24% under the AM1.5 conditions and is related to an essential increase of photon mean free path in the textured silicon SC. The other mechanism, more pronounced in the SC-BC with the efficiency below 22%, imposes limitations on the optimal thickness due to the surface recombination on the front SC-BC surface. [ABSTRACT FROM AUTHOR]

The influence of non-radiative exciton recombination (NRER) on the photoconversion efficiency in silicon solar cells with short Shockley-Read-Hall lifetimes tSRH has been studied. It has been shown that the efficiency reduction due to this effect is the stronger the shorter tSRH. The influence of NRER is most evident when the NRER time becomes shorter than tSRH. At sufficiently short tSRH, NRER substantially limits the optimal base doping levels of silicon solar cells, at which the photoconversion efficiency is maximal. [ABSTRACT FROM AUTHOR]

The theoretical analysis of photovoltaic conversion efficiency of highly effective silicon solar cells (SC) has been performed for n-type and p-type bases. Considered here is the case when the Shockley-Read-Hall recombination in the silicon bulk is determined by the deep level of Fe. It has shown that, due to asymmetry of recombination parameters inherent to this level, the photovoltaic conversion efficiency is increased in SC with the n-type base and decreased in SC with the p-type base with the increase in doping. Two approximations for the band-to-band Auger recombination lifetime dependence on the base doping level are considered when performing the analysis. The experimental results are presented for the key characteristics of SC based on a-Si:H-n-Si heterojunctions with intrinsic thin layer (HIT). A comparison between the experimental and calculated values of the HIT cell characteristics has been made. The surface recombination velocity and series resistance are determined from it with a complete coincidence of the experimental and calculated SC parameters' values. Apart from the key characteristics of SC, surface recombination rate and series resistance were determined from the results of this comparison, in full agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

This paper describes the results of comparative studies of illumination currentvoltage characteristics and spectral characteristics of silicon solar cells with rear location of the collector p-n-junction for the cases of non-passivated and passivated front illuminated surface. Passivation was performed by silicon dioxide layer or ITO layer. It was found that ITO layer surface passivation with formation of ITO/silicon heterojunction, unlike silicon dioxide layer passivation, leads to a significant reduction of the effective surface recombination velocity. It significantly increases the value of the internal quantum efficiency in the wavelength range from 550 to 1050 nm and, as a result, significantly increases the value of short-circuit current of solar cells. [ABSTRACT FROM AUTHOR]

Investigated in this paper are theoretical and experimental spectral dependences of the short-circuit current as well as small-signal photo-e.m.f. in silicon solar cells. The authors have considered two constructions of solar cells. The first construction is a solar cell with contacts on the front and back surfaces, and the second -- solar cells with back barriers and contact metallization. Analyzed in the work are spectral dependences of the internal quantum efficiency for the short-circuit current and smallsignal photo-e.m.f. It has been shown that the short-wave drop of the short-circuit current is related with recombination on deep centers at the front surface as well as inter-band Auger recombination in the heavily doped emitter. At the same time, availability of the shortwave drop in the small-signal photo-e.m.f. is related with limitation of the efficient rate of surface recombination Seff(λ) due to diffusion inflow. The latter takes place when a layer with the thickness dp and increased recombination is available near illuminated surface. In this case, the mechanism providing decrease in the small-signal photo-e.m.f. in the area of strong light absorption is related with increasing the efficient rate of surface recombination near the front surface, when the dominant amount of electro-hole pairs is generated in the layer with the increased recombination rate. The same mechanism is responsible for the short-circuit current drop in solar cells with back barriers and contact metallization. Juxtaposition of theoretical and experimental results enabled to determine parameters that characterize sub-surface properties of solar cells, namely: the thickness of the surface layer with increased recombination, lifetime of carriers in it, and dependences Seff(λ) . [ABSTRACT FROM AUTHOR]

Theoretical analysis and experimental research of Si solar cells (SC) with interdigitated back side contacts (BSC) photovoltaic parameters and photoconversion efficiency at low light level have been done in presence of floating p+ - n junctions and isotype n+ - n junctions on frontal (illuminated) surface. It has been found that in case of floating junction the magnitudes of short-circuit current, open-circuit voltage and efficiency, as well as of internal quantum efficiency of photocurrent can decrease significantly due to recombination in the space charge region (SCR) rather than to surface recombination. In case of isotype junction, this decrease is absent. These results allow to conclude that the floating p+ - n junctions at the front surface of the silicon BSC SC would be appropriate for use only in case of an illumination intensity ≥ 1000 W/m². [ABSTRACT FROM AUTHOR]

A theoretical analysis of the band-edge electroluminescence efficiency in silicon diodes and p-i-n-structures has been made. We have shown that maximal possible efficiency can achieve 10 % both at room and liquid nitrogen temperatures. Maximal values of the efficiency are restricted by the interband Auger recombination process. It is found that electroluminescence efficiency decreases rapidly with the decrease of characteristic Shockley-Reed-Hall nonradiative lifetime for minority carriers. It is shown that even at room temperatures the main contribution into the edge electroluminescence in silicon barrier structures is given by excitonic effects. Dark IV characteristics of directly biased silicon diodes measured both at room and nitrogen temperatures are used to explain anomalous temperature dependencies of silicon diode electroluminescence. [ABSTRACT FROM AUTHOR]

Experimental data on degradation of photovoltaic and photoenergetic characteristics of silicon solar cells exposed by high-energy electrons and protons as well as low-energy protons have been obtained. The previously proposed theoretical model that can describe degradation of the solar cell characteristics under the influence of irradiation, including that creating spatially inhomogeneous defect distribution over the structure thickness, has been experimentally confirmed. It was ascertained that in the cases of 1 MeV energy electron and 20 MeV energy proton irradiations, when there is a relatively homogeneous defect distribution over the silicon solar cell thickness, its short-circuit current degrades faster than the open-circuit voltage. On the contrary, in the case of low-energy 0.1 MeV proton irradiation, when the distribution of defects is spatially inhomogeneous, the open-circuit voltage degrades faster than the short-circuit current. [ABSTRACT FROM AUTHOR]

The growth of the sick rate of limb peripheral vessels associated with a severe outcome (trophic ulcers, amputation) exerts an appreciable effect on the lowering of quality of life in patients. This manifests by the prolonged loss of work fitness, change of the habitual occupation and disability establishment. Objective analytical information on this problem will be of help in the delineation of the tendencies in this direction and potential approaches to the prevention of social losses. The present work is based on an analysis of 2115 statements of medicosocial expert evaluation (MSEE) of invalids suffering from diseases of limb vessels, performed over recent 8 years in the Altai region. The decisions made by the MSEE were based on the results of the clinical examination of patients using the current diagnostic modalities (ultrasonography, duplex scanning, angiography, etc). It has been established that among persons who had undergone MSEE, over the half (64.1%) were under 60 years, i.e. in the age of work fitness. It is noteworthy that the overwhelming number of invalids were men (83%) and workers (84.2%). As for special vascular pathologies, the majority of patients presented with obliterative arterial diseases (OAD) of the lower limbs, accounting for 76.3% whereas patients with venous pathology ranked second in number (15.9%). The highest severity of invalidism (groups I and II) was also recorded in OAD (77.5%), especially in atherosclerosis obliterans (AO) which accounted for 84%. Of note, these diseases were marked by no tendency toward reduction of their incidence. The time of temporary disability (from 3 to 9 months) was also most frequently recorded in OAD of the limbs. In OAD, the temporary or persistent loss of work fitness were caused by critical ischemia and amputations whereas in venous pathology, namely in varicosity and post-thrombophlebotic syndrome, the cause was progressing CVI complicated by trophic ulcers. On the whole, the lack of changes in the lowering of the number of invalids due to the given pathology evidences the unsatisfactory results of these patients' rehabilitation and the high socioeconomic tension determined by considerable treatment expenses and the high number of the disabled. Approaches to the escape from such a situation should be looked for in the early mass screening diagnosis of vascular lesions, early drug and surgical treatment and in the refinement of the system of rehabilitation prophylactic medical examination.

The chief factors of aggression are discussed together with mechanisms of protection of gastric and duodenal mucosa. Results of treatment of 30 patients with gastritis (Helicobacter pylori negative) with a cytoprotective drug smecta are presented.

Modern definition, classifications, diagnosis and treatment of irritable bowel syndrome (IBS) are presented together with results of treatment of 30 patients with irritable bowel syndrome with the new selective calcium-channel blocker dicetel.