Today, an actual task of photovoltaics is the search for new light-absorbing materials for solar cells, which will make them more efficient and economically affordable. Semiconductor Cu₂NiSn(S,Se)₄ (CNTSSe) thin films are promising materials due to suitable optical and electrical properties. This compound consists of abundant, inexpensive, and low-toxicity elements. However, few results of studying the properties of CNTSSe films have been presented in the literature. This paper presents the results of studying the morphology, phase composition, and crystal structure of the CNTSSe films, which were first obtained by high-temperature annealing of electrodeposited Ni/Cu/Sn/Ni precursors on glass/Mo substrates in chalcogen vapor. The films were studied using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. It has been found that sequential electrochemical deposition makes it possible to obtain the Ni/Cu/Sn/Ni precursors of the required quality for further synthesis of the films. It is shown that high-temperature annealing in chalcogen vapor in air makes it possible to synthesize stable polycrystalline CNTSSe films. The obtained results confirm that the production of CNTSSe films is suitable for use in solar cells by the proposed method, which can be improved by more precise control of the precursor composition and annealing conditions.

A set of Ag _x Cu _{1 –  x} GaSe ₂ (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 Ag _x Cu _{1 –  x} GaSe ₂ powders. The observed effect is apparently attributed to the replacement of deep charge carrier traps, such as selenium vacancies, by shallower cation vacancies.

Using the solid-state ampoule synthesis method, Cu_2 – δSrSnS₄ (0 ≤ δ ≤ 0.4) samples have been synthesized; the crystal lattice parameters of the samples have been refined, and the Raman spectra as a function of δ have been studied. It has been found that these compounds have a narrower single-phase region than that of Cu_2 – δBaSnS₄ compounds with a similar structure. In addition, the Cu_2 – δSrSnS₄ samples are unstable during vacuum annealing. Using microwave photoconductivity, it has been found that further annealing of Cu_2 – δSrSnS₄ in the presence of SnS₂ leads to a significant increase in the photogenerated current carrier lifetimes; this fact is apparently attributed to a decrease in the amount of impurity phases and structural defects formed due to thermal instability during synthesis.

The structure of CdTe–Sb₂Te₃ and CdTe–CdSb solid solutions (0–10¹⁹ Sb atoms cm^–3) prepared by multistage solid-state synthesis from the elements has been studied. It has been found that the introduction of antimony Sb³⁺ and Sb³⁻ into cadmium telluride leads to a decrease and increase in the unit cell volume, respectively. It has been shown that the crystal lattice parameters gradually change up to an antimony concentration of 10¹⁸ atoms cm^–3 in both systems, whereas an increase in the antimony concentration above 10¹⁸ Sb atoms cm^–3 is characterized by an abrupt change in the unit cell volume due to a significant change in the structure. The decay kinetics of current carriers has been studied by the time-resolved microwave photoconductivity method. It has been found that the introduction of antimony into CdTe in a threshold concentration (10¹⁸ Sb atoms cm^–3) leads to an increase in the lifetime of photogenerated current carriers; this fact can be attributed to the formation of defect associates and the occurrence of a self-compensation process during doping.

The Cu₂CrSnS₄ microcrystalline powders and films with orthorhombic structure were obtained by solid-phase synthesis, and their Raman spectra were recorded for the first time. By optical spectroscopy, it was found that their E_g=1.70 eV, while in energy band gap of the powders there is a donor level with E=1.23 eV. It is shown for the first time that films of this material are photosensitive and have p-type of dark conductivity. Keywords: solid-phase synthesis, microcrystalline powder, film, dark conductivity.