ИСТИНА

In the last decade various types of all-solid photovoltaic cells have been developed including perovskite solar cells. Complex iodides play a role of light-harvesting compounds and obtain hole and electron conductivity properties. But it was demonstrated that this type of materials also has electroluminescent properties. However, a significant drawback of a large amount of compositions is the tendency to degradation during oxidation, exposure to ultraviolet radiation and other factors. The use of inorganic iodides with more stability than organic-inorganic compounds looks promising. For this purpose, the cesium iodcuprate CsCu2I3 was chosen as the object of study, which, according to the data obtained earlier, has the ability to photoluminescence in the visible region. The aim of the work was to obtain films of cesium ioduprate and the study of their optical and transport properties. Within its framework, problems were dissolved on the synthesis of continuous films, the analysis of their morphology, the determination of the phase composition and the subsequent analysis of their transport characteristics. To obtain films, the solution method was used, with the varying solvents and their mixtures for deposition, as well as the procedure for applying the reagents — one-step and two-step. The one-step method involved co-precipitating copper iodides with cesium and subsequent thermal removal of the solvent. The two-step method consisted in obtaining a film of copper iodide, which subsequently immersed for some time into cesium iodide solutions. The analysis of the properties of the films obtained was carried out with the help of X-ray phase analysis and optical microscopy. As a result, CsCu2I3 films were synthesized under various conditions. It was found that with an increase in the concentration of dissolved substances, the degree of continuity of the resulting film increased. As a result of the two-step synthesis, according to X-ray phase analysis, a significant amount of the impurity phase Cs3Cu2I5 was formed. Copper iodide films obtained by this method in the first step of two-stage synthesis demonstrate texture and are oriented along the <111> direction. In one-step synthesis DMSO, acetonitrile, dimethylformamide, ethyl alcohol and other substances were tested as solvents. In the synthesis, temperatures from 110 to 190 ° C were used, and it was found that at temperatures up to 150 ° C some DMSO remained in the film, which acted as the main component of the solvent mixture. The amount of the impurity phase Cs3Cu2I5 in this method of synthesis was significantly smaller, which follows from the diffraction data of the products. The best results in terms of the uniformity of the coating showed films obtained from dimethyl sulfoxide and a mixture of dimethyl sulfoxide with acetonitrile. In all cases, the growth of rod-like CsCu2I3 particles was observed. According to X-ray diffraction data, the presence of orientation of the films along the <110> direction was revealed, which was observed for films obtained at temperatures higher than 110°C. Further work will be aimed at studying the transport characteristics of films and individual CsCu2I3 whisker crystals by the two-contact method. [1]. Shan Q. et al. High Performance Metal Halide Perovskite Light-Emitting Diode: From Material Design to Device Optimization. Small. 2017, 13 (45), 1–25.