Antireflection coatings (ARCs) increase the absorption of light and, therefore, the conversion efficiency of solar cells. Mullite was chosen as the ARC material for a silicon (Si) solar cell and was synthesized by melting a charge consisting of a mixture of Al2O3 and SiO2 at a component concentration of 75 and 25 wt.

A set of AgxCu1 – xGaSe2 (0 ≤ x ≤ 1) solid solution powders has been prepared by solid-state synthesis. Using a combination of X-ray diffraction analysis and Raman spectroscopy, it has been found that the samples have a single-phase tetragonal structure (space group I-42d). It has been shown that their crystal lattice parameters do not follow Vegard’s law up to x ≈ 0.4. It has been revealed that the band gap of the samples also changes nonlinearly: initially it decreases and then increases. Studies of the low-temperature luminescence and microwave photoconductivity decay spectra have shown that a set of samples with x of 0 to 0.4 and further in the region with x > 0.4 is characterized by an increase in the photogenerated current carrier lifetime in AgxCu1 – xGaSe2 powders. The observed effect is apparently attributed to the replacement of deep charge carrier traps, such as selenium vacancies, by shallower cation vacancies.

In this work, the optical properties of nanocrystalline CdS films in the initial state and after ion-plasma treatment have been studied. The chemical bath deposition technique was used to prepare CdS films with thickness 80-115 nm on glass substrates. The ion-plasma treatment was carried out in argon plasma in a high-density low-pressure radio frequency inductively coupled plasma reactor at an argon ion energy of 25 eV for 30-50 s. It has been established that ion-plasma treatment leads to a decrease in film thickness by 10-15% of the initial one and the formation of new nanostructures on its surface. The results showed that the sizes of coherent scattering regions during plasma treatment decreased for a series of studied samples from 8.2-10.0 nm to 6.3-7.7 nm. This led to an increase in the band gap energy of the for nanocrystalline CdS films from 2.53-2.78 eV to 2.95-3.11 eV.

The peculiarities of the electrochemical deposition of a copper layer on flexible titanium and tantalum supports as well as the modes of sequential electrochemical deposition of a tin layer on Cu/Ti and Cu/Ta supports and a nickel layer on the Sn/Cu/Ti and Sn/Cu/Ta supports are studied by cyclic voltammetry from the corresponding electrolyte solutions. The deposition potentials are found for each metal layer with regard to the support type. A wide series of stable precursor films Cu–Sn–Ni/Ti and Cu–Sn–Ni/Ta are obtained. The stage of annealing in the active sulfur atmosphere (sulfurization) is optimized aimed at the synthesis of stable compounds Cu2NiSnS4. Based on data obtained by the methods of XRD and Raman spectroscopy, it is shown that the synthesis of stable single-phase compounds Cu2NiSnS4 with the polycrystalline structure on the Ta and Ti supports requires that the annealing in the active sulfur atmosphere carried out at 550°С for 60 min.

In this work, the influence of proton irradiation and platinum impurities on the crystal structure of silicon samples was studied by Raman spectroscopy. It has been established that the doping of single crystals of Si with platinum leads to minor changes and the appearance of new vibrations in the Raman spectra. The intensity of the main silicon peak at 521 cm–1 decreases by a factor of 1.6, while its FWHM practically does not change and is about 4.0 cm–1. Such a decrease in the intensity of the peak is probably due to the weakening and breaking of bonds in the structure of the silicon crystal lattice due to the diffusion of Pt. It is shown that the appearance of new vibrations in the range 60–280 cm–1 in the spectra of Si is associated with the presence of elemental Pt and the formation of PtSi. It has been found that irradiation of Si samples with 600 keV protons leads to a change in the Raman spectra, and the peaks from Pt and/or PtSi disappear.

We present the results of the study of the microstructure, X-ray diffraction and Raman scattering spectra of Cu2SnS3 (CTS) films synthesized at 500 o C by the sulfurization of SnCu stacked metal precursors with different annealing time. The results indicate that sulfurization time has a great influence on both composition and morphology of the film. It is shown that the process of formation of a single-phase CTS compound with a monoclinic structure and composition close to stoichiometry is completed for a synthesis time of 60 - 80 min. With an increase in the time of synthesis to 120 min, the preservation of the monoclinic structural modification of the material is observed, accompanied by a shift in the stoichiometric composition, namely copper enrichment, material delamination and degradation of microstructural characteristics. As a result, it was found that the most optimal conditions for the synthesis of a single-phase Cu2SnS3 compound of a monoclinic structure are the temperature 500 o С with the duration of the sulfurization process from 60 to 80 min.

In this work, we have studied the geometric structure and electronic and optical properties of Cu2ZnSn(S1-xSex)4 nanocrystals where x = 0, 0.25, 0.50, 0.75, 1.00 by the quantum-chemical calculations within the framework of DFT. For the electronic and optical properties calculations, the effective XC functional and the TB-mBJ potential were used. The calculated structural characteristics show that the volume of these systems increases with increasing the Se concentration. The electronic properties of the Se-doped kesterite Cu2ZnSnS4 show that the bandgap tends to decrease. It was found that the Se-doped material has noticeably increased its absorption capacity. Hence, the efficiency of the Cu2ZnSnS4 in the IR region of radiation improves. The effective reduction bandgap from 1.455 eV to 0.94 eV is observed, which is in gоod agreement with known experimental data for the pure and undoped systems Cu2ZnSnS4 and Cu2ZnSnSе4. The calculated band gap is 1.346 eV for the Cu2ZnSnS3Se system, which is comparable with the optimal bandgap of semiconductors used in photovoltaic applications. It was found that with the increase of the Se concentration, the absorption coefficient increases, thereby resulting in the materials' reflectivity decrease. The calculated optoelectronic parameters and the density of electronic states indicate that the Cu2ZnSnS4:Se system possesses a favorable property, suitable for applications in solar cells technology.

In this work, the effect of alpha particles on the crystal structure and structural characteristics of n-type silicon (n-Si) single crystals was studied using X-ray diffraction. Samples of n-Si were first doped with chromium and then irradiated with alpha particles at a dose of 6x10(14) c?(-2). It has been established that the irradiation dose used does not lead to the formation of a near-surface amorphous silicon layer. However, the obtained X-ray diffraction patterns indicate a slight deterioration in the crystallinity of silicon samples after their irradiation.

The Cu 2 SnS 3 (CTS) thin films were produced by deposition of Sn/Cu layers by RF sputtering followed by annealing in an Ar/S atmosphere with S and Sn sources. According to XRD analyses and Raman spectroscopy, it was shown that single-phase CTS films of a monoclinic structure with traces of the CuxS phase were formed at a temperature of 520 °C. The scanning electron spectroscopy revealed a compact and homogeneous microstructure of the polycrystalline CTS layers. Photoluminescence spectra of the СTS films of monoclinic modification show one wide peak in the energy range of 0.7—1.0 eV, due to optical transitions of electrons from the conduction band to deep energy levels of acceptor-type defects.

The Cu2SnS3 (CTS) thin films were produced by deposition of Sn/Cu layers by RF sputtering followed by annealing in an Ar/S atmosphere with S and Sn sources. According to XRD analysis and Raman spectroscopy, it was shown that single-phase CTS films of a monoclinic structure with traces of the CuxS phase were formed at a temperature of 520°C. Scanning electron microscopy revealed a compact and homogeneous microstructure of the polycrystalline CTS layers. Photoluminescence spectra of the СTS films of monoclinic modification show one wide peak in the energy range of 0.7–1.0 eV, due to optical transitions of electrons from the conduction band to deep energy levels of acceptor-type defects.

The temperature dependence (in range from 24 to 290 K) of Raman spectroscopy of the Cu2ZnSnSe4 (CZTSe) films with Zn-rich (series A) and Zn-poor (series B) composition obtained on a Ta foil is investigated. Analisys and approximation by the Lorentz function of the CZTSe Raman spectra suggests that the CZTSe most intense Raman peak consists of two modes (at 192/189 and 194/195 cm(-1)), which are slightly shifted from each other. In addition, the Raman peaks around 192 and 189 cm(-1) lead to asymmetric broadening of dominant peaks at 194 and 195 cm(-1) in Raman spectra of the CZTSe films series A and B, respectively. In the case of the Sn-rich CZTSe films, we attribute of Raman peak around 189 cm(-1) to SnSe2 compound. However in the case of the Sn-poor CZTSe films, the observable shift is too high to assign confidently the 192 cm(-1) band to a SnSe2 compound, which was not detected by XRD analysis. We suppose that this mode is attributed to disordered kesterite structure. The temperature dependence Raman spectra for both series of the CZTSe films shows that a change temperature from 290 to 24 K leads to position shift and narrowing of the CZTSe Raman A-modes. The calculated temperature coefficients and anharmonic constants in Klemens model approximations for temperature dependence of shift position and FWHM of the CZTSe A-modes shown that four-phonon process has dominant contribution in damping process and as a consequence in Raman spectrum changes for two series of the CZTSe films.

Polycrystalline Cu2ZnSn(SхSe1– х)4 solid solutions have been prepared by a single-temperature method using elemental Cu, Zn, Sn, S, and Se. The chemical composition of the synthesized materials has been determined by X-ray microanalysis and their crystal structure and phase composition have been studied by X-ray diffraction and Raman spectroscopy. Using frequency-time-resolved microwave photoconductivity measurements, we examined the effect of sulfur and selenium content on photogenerated current carrier loss kinetics in the Cu2ZnSn(SхSe1– х)4 solid solutions. An increase in sulfur content has been shown to result in the formation of additional deep levels, capable of acting as electron acceptors.

Thin film Cu2ZnSnSe4 (CZTSe) solar cells can be grown on flexible and lightweight metal substrates allowing their direct integration on bendable surfaces and where the weight of solar cell is an important criterion. Flexible substrates make it possible to use the roll-to-roll technology of solar cells, which leads to an additional reduction in the cost of production and final cost of solar cells. The CZTSe thin films were fabricated by selenization of electrodeposited metallic precursors onto tantalum (Ta) flexible substrates at different temperature and time. The results of the effect of selenization temperature and time on the morphology, structural, and optical property of the CZTSe films are presented in this work. It was found that the morphology of the CZTSe thin films depend on their elemental composition and time of selenization. Experimental data indicate that composition of the CZTSe films selenized within 10 and 20min at 560 °C have the CZTSe basic phase and secondary phases (CuSe, SnSe and ZnSe). In contrast, the increase in selenization temperature and/or time leads to disappearing of the secondary phases (CuSe, SnSe) and better crystallization of the CZTSe films. It was found that films selenized at 560 and 580 °C within the same time have similar characteristics. Depending on selenization time and temperature of the CZTSe, thin films exhibited a shift in band gap from 1.16 to 1.19 and to 1.22 eV, respectively. The change of band gap of the CZTSe thin films is associated with changes of elemental and phase compositions, and thickness of the film. These results showed that the received CZTSe films on Ta foil can be used for fabrication of thin film solar cells.

AbstractCu_2ZnSnSe_4 thin films are produced by selenizing electrochemically layer-by-layer deposited and preliminarily annealed Cu–Zn–Sn precursors. For flexible metal substrates, Mo and Ta foils are used. The morphology, elemental and phase compositions, and crystal structure of Cu_2ZnSnSe_4 films are studied by scanning electron microscopy, X-ray spectral microanalysis, X-ray phase analysis, and Raman spectroscopy.

Cu 2 ZnSnSe 4 thin films are produced by selenizing electrochemically layer-by-layer deposited and preliminarily annealed Cu–Zn–Sn precursors. For flexible metal substrates, Mo and Ta foils are used. The morphology, elemental and phase compositions, and crystal structure of Cu 2 ZnSnSe 4 films are studied by scanning electron microscopy, X-ray spectral microanalysis, X-ray phase analysis, and Raman spectroscopy.