Nonstoichiometric ZnO1-x phases with oxygen deficiency at grain boundaries (GBs) in polycrystalline ZnO layers are a typical damaged layer formed during the synthesis or subsequent storage. In this case, the processes of adsorption-desorption of gases are the basic phenomenon used in the analysis of gas composition. MGB layers also play an important role in creating transparent electrodes for transparent electronics and optoelectronics devices. This makes it relevant to study the generalization of research data on non-stechiometric structures in various applications. Purpose: the research carried out is devoted to the analysis of the formation processes of non-stoichiometric ZnO1-x surface phases in gas sensors, transparent electrodes, ceramic targets for magnetron sputtering, and in light-emitting structures. Research is aimed at finding ways to control and optimizing the parameters of non-stoichiometric ZnO1-x phases. The structural features, electrical, optical, and emissive properties of the layers were studied depending on the stoichiometry of the material. The issues of transformation of the structure of grain boundaries in ZnO-based polycrystalline layers depending on the formation conditions and external influences are considered. The relationship between the mechanisms of carrier transport and the processes of formation of nonstoichiometric phases on the MG has been studied. The dependences of the luminescence spectra of ZnO layers on the density of oxygen vacancies were traced. The regularities of the formation of energy structures of magnetic grains in ZnO layers are considered. Establishment of patterns of formation and characteristics of non-stoichiometric phases on the MGB during the formation of various modifications of transparent electrodes. Study of ways to optimize the parameters of surface non-stoichiometric layers.