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Information × Registration Number 0210U005773, 0110U006229 , R & D reports Title Investigations of the properties and impurity composition of silicon and degradation of its characteristics under irradiation. Optimization of the crystals growing technology for making of photovoltaic cells with improved performance. popup.stage_title Head Khyrunenko Lyudmyla Ivanivna, Registration Date 06-01-2011 Organization Institute of physics NASU popup.description2 The subject of study is monocrystalline silicon with high oxygen and boron content, which is usually used for photovoltaic solar cells production; photodiodes. The object of work is the study of light induced reactions with participation of oxygen, oxygen dimers and boron in silicon and photovoltaic cells. One of the main problems of the modern photovoltaic, 93% of which are based on single, poly- and multi- silicon, is low coefficient of efficiency. Typical commercial silicon devices are less than 15% efficient and unfortunately in their initial few hours of operation solar cells produced on the base of silicon doped with boron suffer from degradation and lose 10% of their efficiency. It is believed that the reduction in efficiency is due to a formation a powerful recombination centre as a result of reactions that occur under effect of light. But to date the nature of the defect has not been established and, accordingly, is not developed methods suppression of degradation. To solve this problem requires a thorough understanding of the possible reactions between the defects which may occur in the technology of solar cells production and are stimulated by light in the course of their operation. In this investigation we study the role of boron and oxygen, which are the dominant impurities in silicon, used in photovoltaic, in the processes of defect formation, which occur under the influence of light close to the spectral composition of solar radiation. The investigations were carried using spectroscopy of local vibrational modes which is one from the powerful methods in defects identification with the use of Fourier spectrometer IFS-113v. In silicon the new absorption band situated near 1026 cm-1 was found after its illumination at a light intensity of 70-100 mW/сm2 and passing weak current (4-20 mА/сm2). An investigation of sample with various content of oxygen and boron has shown that defects concentration, to which new band corresponds, depends on concentration of these impurities. This indicates that both oxygen and boron are part of the defect. It was shown that the intensity of the detected bands increases with increasing illumination time. It was found that the defect may also occur during heat treatment of silicon without illumination at applied to the sample of weak currents (4 - 200 mA). Assumption has been made that formation of defect occur due to recombination-enhanced diffusion of oxygen (or oxygen dimers) and may take place through intermediate metastable state. The supposition was made that observed center is one of the defects that may lead to the degradation of solar cells parameters in the first hours of their operation. Obtained data will be used in future to develop of methods to decrease formation efficiency of found defect and to suppress its effect on degradation of solar cells parameters. It is shown that doping of silicon with nitrogen leads to a decrease in the deflection plates after cutting and increase the width of the surface defect-free zone near the p-n junction. It was found that the effective distribution coefficient of tin in silicon, depending on the speed of pulling the single crystal during growth, can vary from 0.0167 to 0.0233, which leads to the heterogeneity of its distribution along the ingot. The photodiodes have been made on the base of investigated silicon. It is shown that the initial parameters correspond to the standard characteristics of photodiodes. The investigation of the lifetime of minority current and the open circuit voltage under illumination has been shown the effect of their degradation during the first 3-4 hours of operation. The obtained results can be used to develop methods of controlling influence on the reactions between the impurities and in manufacturing technology of devices with the specified parameters. Product Description popup.authors Дуванський Андрій Володимирович Помозов Юрій Васильович Самочорних Сергій Володимирович Соснін Михайло Георгійович Хируненко Людмила Іванівна Яшник Віктор Іванович popup.nrat_date 2020-04-02 Close