A model of an autonomous receiving station of free space optical communication system based on a multi-section energy heterostructure (HJT) Si photoconverter and an information photodetector based on AlGaAs/GaAs p-i-n photodiodes has been developed. The energy part, when excited by laser radiation with a power of ~ 264 W at a wavelength of 0.974 μm in the photovoltaic mode, provided ≥ 60 W of electric power. The photodetector of the information channel, when excited by pulsed radiation at a wavelength of 0.78 μm, provides response time in the photovoltaic mode in the sub-nanosecond range. Keywords: free space opical communication, receiving station, HJT Si photoconverter, AlGaAs/GaAs p-i-n photodetector, laser radiation, pulsed radiation

prudchenkokk@mail.ioffe.ru Abstract. The possibility of efficient conversion of continual infrared laser radiation by heterojunction technology a-Si:H/c-Si photovoltaic converters is demonstrated. The photo-voltaic characteristics of eight different types of heterojunction structures were investigated. The photovoltaic converters of the n-& alpha;-Si/n-c-Si/p-& alpha;-Si heterojunction structure with contact grid Ag turned out to be the best in terms of dark currents, external quantum efficiency, I-V characteristics, and conversion efficiency of laser radiation with 1064 nm wavelength at a pow-er density up to 2 kW/m2. The maximum efficiency-' 24.5% of this structure was reached at power density of 1 kW/m2.

A model of an autonomous receiving station of free space optical communication station based on a multi-section energy heterostructure (HJT) Si photoconverter and an information photodetector based on AlGaAs/GaAs p-i-n photodiodes has been developed. The energy part, when excited by laser radiation with a power of ~264W at a wavelength of 0.974µm in the photovoltaic mode, provided ≥60W of electric power. The photodetector of the information channel, when excited by pulsed radiation at a wavelength of 0.78µm, provides speed in the photovoltaic mode in the sub-nanosecond range.

The possibility of efficient conversion of constant laser radiation using alpha-Si:H/c-Si structures in the transparency window of the Earth's atmosphere at wavelength 1.06 mu m is shown for the first time. A hybrid photovoltaic converter based on alpha-Si:H/c-Si cells and AlGaAs/GaAs photodetectors has been developed and manufactured. The photoelectric con-verter provides simultaneous conversion of radiation from two types of laser sources in the photovoltaic mode: continuous at a wavelength of 1.06 mu m with an efficiency of similar to 26% and pulsed at a wavelength of 0.78 mu m of <= 900 ps FWHM.

Уменьшение концентрации дефектов в пленках ZnO, полученных методом высокочастотного магнетронного распыления, дает возможность эффективного легирования акцепторными примесями как в катионной (Li), так и анионной подрешетках (N+) и получение дырочного типа проводимости с воспроизводимыми параметрами (концентрации, подвижности) носителей заряда. Легирование азотом производилось с помощью отжига пленок ZnO в атмосфере высокочастотного газового разряда. В результате измерений с помощью эффекта Холла (методика Ван-дер-Пау) показано, что использование тонких слоев Eu, нанесенных на поверхность ZnO-пленок, приводит к увеличению концентрации и подвижности основных носителей заряда. Введение металлических примесей, отличающихся по размерам ионных радиусов (Ag, Au), в катионную подрешетку пленок ZnO с целью компенсации напряжений несоответствия дает возможность увеличения концентрации центров излучательной рекомбинации. DOI: 10.21883/FTP.2017.05.44411.8437

Исследован процесс текстурирования поверхности монокристаллического кремния, окисленного под слоем V2O5. Интенсивное окисление кремния на границе Si-V2O5 начинается при температуре 903 K, что на 200 K ниже, чем при термическом окислении кремния в атмосфере кислорода. На границе V2O5-Si образуется слой диоксида кремния толщиной от 30-50 нм с включениями SiO2 в кремний глубиной до 400 нм. Найдено значение коэффициента диффузии атомарного кислорода при 903 K через слой диоксида кремния (D≥2·10-15 см2·с-1). Предложена модель низкотемпературного окисления кремния, основанная на диффузии атомарного кислорода из V2O5 через слой SiO2 к кремнию и возникновении преципитатов SiOx в кремнии. После удаления слоев V2O5 и диоксида кремния на поверхности кремния образуется текстура, интенсивно рассеивающая свет в области длин волн 300-550 нм, что важно для текстурирования фронтальной и тыльной поверхностей солнечных фотопреобразователей. DOI: 10.21883/FTP.2017.01.8292

It is demonstrated that a reduction in the defect concentration in ZnO films formed by high-frequency magnetron sputtering allows effective doping with acceptor impurities both in the cation (Li) and anion (N+) sublattices and p-type conductivity with reproducible charge-carrier parameters (concentration and mobility) to be obtained. ZnO films are doped with nitrogen by annealing in a high-frequency gas discharge atmosphere. Hall measurements by the Van der Pauw technique show that the deposition of thin Eu layers on the ZnO film surface increases the concentration and mobility of majority charge carriers. The embedding of metal impurities with different ionic radii (Ag and Au) in the cation sublattice of the ZnO films to compensate misfit stresses makes it possible to enhance the concentration of radiative-recombination centers.

The process of surface texturing of single-crystal silicon oxidized under a V2O5 layer is studied. Intense silicon oxidation at the Si–V2O5 interface begins at a temperature of 903 K which is 200 K below than upon silicon thermal oxidation in an oxygen atmosphere. A silicon dioxide layer 30–50 nm thick with SiO2 inclusions in silicon depth up to 400 nm is formed at the V2O5–Si interface. The diffusion coefficient of atomic oxygen through the silicon-dioxide layer at 903 K is determined (D ≥ 2 × 10–15 cm2 s–1). A model of low-temperature silicon oxidation, based on atomic oxygen diffusion from V2O5 through the SiO2 layer to silicon, and SiO x precipitate formation in silicon is proposed. After removing the V2O5 and silicon-dioxide layers, texture is formed on the silicon surface, which intensely scatters light in the wavelength range of 300–550 nm and is important in the texturing of the front and rear surfaces of solar cells.

The introduction of nanocrystals plays an important role in improving the stability of the amorphous silicon films and increasing the carrier mobility. Here we report results of the study on the photoluminescence and its dynamics in the films of amorphous hydrogenated silicon containing less than 10% of silicon nanocrystals. The comparing of the obtained experimental results with the calculated probability of the resonant tunneling of the excitons localized in silicon nanocrystals is presented. Thus, it has been estimated that the short lifetime of excitons localized in Si nanocrystal is controlled by the resonant tunneling to the nearest tail state of the amorphous matrix.

The photoinduced degradation of photovoltaic converters based on an a-Si:H/µc-Si:H tandem structure under a standard illuminance of 1000 W/m2 is studied. The spectral and current–voltage characteristics of specially fabricated samples with various degrees of crystallinity of the intrinsic layer in the lower (microcrystalline) cascade are measured in the course of the tests.

Optical and electrical properties (Haze spectra, carrier concentration, mobility, resistivity) of zinc oxide thin films deposited on glass substrates were studied by plasma treatment and by thermal annealing. Films of copper oxides on the glass and CuO/ZnO structures were formed by vacuum deposition of copper films followed by thermal annealing in air. Optical and structural properties of the CuO films and electrical properties of ZnO/CuO structures were investigated upon thermal treatment. It is shown that a photosensitive n-ZnO/p-CuO heterojunction may be formed by rapid (similar to 1 min) thermal processing in air.

Photo-induced degradation of tandem α-Si: H/μc-Si: H photoconverters under standard light flux densities of 1000 W/m2 (AM1.5G) have been investigated. Spectral and current-voltage characteristics of solar modules produced with standard and modified recipes are presented and analyzed. This research is dedicated to the optimization of crystallization level in intrinsic layer of lower (microcrystalline) cascade.

The results of works on designing, mounting, and testing a grid-connected photovoltaic station based on thin-film tandem photovoltaic modules with a peak power of 2 kW are presented. Approaches and methods to analyze such stations, as well as techniques for constructing similar objects and payback mechanisms, are described. The role and site of electric energy storage units entering into a grid solar power plant are considered.

Specific features of the operation of the membrane-electrode assembly with high catalytic activity that are a part of the simplified design of a low-temperature air-hydrogen fuel cell under conditions of forced and natural convection of air on the cathode are studied. The governing effect of water balance on the specific power of the fuel cell in the stationary mode (∼1 h) is shown, and the range of the operating conditions of the cell with self-control is determined. The power of the fuel cell at an efficiency of ∼50% and the surface density of platinum on a cathode of ≈0.2 mg/cm2 is 200–250 and 100 mW/cm2 in the forced and natural air-convection modes, respectively, which is comparable with the advanced results.

It is demonstrated that the efficiency of catalysis and platinum usage in electrochemical energy converters can be improved by employing chemically functionalized multiwalled carbon tubes. On this basis, membrane-electrode assemblies for air-hydrogen fuel cells with specific powers up to 581 mW/cm(2) have been obtained.