The possibility of using a graded-gap crystal as a protective coating of organic solar cells from harmful chemical and other external influences has been studied. On the basis of a quantum model for an electronic near-surface state with an Airy potential well, an expression is obtained that is radically different from the Tamm level, with the help of which the condition of light transparency of the graded-gap region is formulated, but with the implementation of protective properties due to a reduced band gap. It is assumed that the developed method is valid for both classical semiconductors and ionic materials. It was shown that graded-gap coatings have no electronic levels at a certain thickness and, therefore, do not absorb solar radiation; they are completely transparent and can also be used as encapsulating coatings for organic solar cells. Antireflection coatings based on MgF2–CaF2 composite materials are considered as an example of a graded-gap coating. Composite material MgF2–CaF2 is a homogeneous material with an ionic bond, so the coating based on it has graded-gap properties. Such coatings are antireflective and promising for encapsulation of organic solar cells. The increase in the transmission of a glass substrate with applied antireflection coatings is 1.68–2.27%, depending on the composition of the coating. After storage under normal conditions for 3 years (2018–2020) and climatic tests for 1 year (2021), the coatings retained their spectral–optical properties. The experiment showed that graded-gap coatings on organic solar cells are antireflective and protective from external influences.

The paper presents the results of testing a heat-protective material based on Al 2 O 3 and SiO 2 fibers under exposure to a concentrated solar energy flux and highly non-uniform thermal and light field conditions. Avariation in the material structure and morphology depending on the heat treatment temperature is shown. The material retains its properties during extended exposure to temperatures of 1,600 – 1,700°C due to the formation of a stable mullite and α-Al 2 O 3 structure. Above the mullite melting point (~1,840°C), the material undergoes deformation and melting, and loses its physical, mechanical, and thermal insulation properties.

The behavior of a heat-protective ceramic composite material based on ZrO 2 fibers in a concentrated solar energy flux under conditions of a strongly nonequilibrium temperature and light field is demonstrated. A change in its structure and morphology depending on the heat treatment temperature is displayed. During an experiment the maximum surface temperature of a specimen based on ZrO 2 fibers reaches 1600°C, which is significantly lower than the operating temperature of materials based on ZrO 2 . As a result of a concentrated flow of solar energy on heat-protective material based on ZrO 2 fibers, sintering, shrinkage, deformation, and fracture effects are observed, and the material loses its physical, mechanical and heat insulation properties.

We present the results of the numerical modeling of the Al 2 O 3 -SiO 2 single layer composite antireflection coating for silicon solar cells, its manufacturing and investigation of the reflection integrated coefficient R S £10 %. It is shown that when the concentrations of Al 2 O 3 , SiO 2 are in the ranges 52-84 % and 16-48 % (weight %), respectively, and the thickness of layers is within the 53-97 nm area, the minimum of Rs is achieved for the Al 2 O 3 = 73-77 %, SiO 2 = 27-23 % and 69-75 nm thickness. It is also shown that for layers of Al 2 O 3 : SiO 2 = 75:25 % with a 72 nm thickness the value of R S is 3.53 %, which is approximately twice lower than R S for the Si 3 N 4 coating.

AbstractResults are presented obtained in measurements of current–voltage characteristics of organic solar cells with and without antiref lection coatings produced by melting in a solar furnace of 95 : 5 and 55 : 45 wt % MgF_2 and CaF_2 fluoride mixtures. The relative increase in the efficiency of the organic solar cells was 3.2% in the first case and 3.3% in the second.

Results are presented obtained in measurements of current–voltage characteristics of organic solar cells with and without antiref lection coatings produced by melting in a solar furnace of 95 : 5 and 55 : 45 wt % MgF2 and CaF2 fluoride mixtures. The relative increase in the efficiency of the organic solar cells was 3.2% in the first case and 3.3% in the second.

We present the results of studying the effect of technological synthesis regimes of a solar furnace using the method of a partial metal reduction of one of the oxides on the phase formation of cermet composite materials of the TiO2-CuO system. It has been established that the phase composition of the synthesized cermet composite materials depends on the carbon concentration, melting temperature and cooling rate. The dependence of the spectral-optical properties of selectively absorbing coatings on the production technology and properties of synthesized composite materials has been presented. It has been found that the coatings fabricated by melting in air with overheating at a melt cooling rate of about 105–106°C/s have the highest values of the integral absorption coefficient, α s = 91.0–94.5%.

Влияние технологических режимов синтеза на солнечной печи на фазовый состав керметов системы TiO 2 -CuO и оптические свойства покрытий на их основе © С.Х.Сулейманов, В

Experimental studies on increasing the transmittance of a light–receiving element (LRE) by applying an antireflection coating were carried out. As an antireflection coating on the solar furnace, the fluoride composite material MgF 2 –CaF 2 was synthesized. Transmission spectra of the LRE without the antireflection coating and with the antireflection coating were measured. The effect of translucence (increase of transmittance) of the LRE after applying the antireflection coating is observed in the spectral region of 0.4–1.1 μm.

The results of the studies on the elaboration of composite antireflective coatings for photoconverters based on polycrystalline silicon are reported. Spectral dependences of the hemispherical reflection factor prior to and after the deposition of the antireflective coating on both the surface of poly-silicon and that of the photoconverter are studied. By the results of the simulation, mixtures of silicon with its oxides, and also a mixture of silicon monoxide with zinc sulfide are chosen as the material of the coating. The effect of the contact grid on the optical properties of the frontal surface of the photoconverter is assessed.