Complex inorganic compounds within the Ag-Ga(In)-Si(Ge)-S(Se) systems constitute a large group of materials that exhibit semiconductor properties. These materials are of significant interest due to their potential applications. They are promising for optoelectronics, photovoltaics, sensor technology, telecommunications, and nonlinear optics.Crystals of the Ag-Ga(In)-Si(Ge)-S(Se) system with various cation-anion compositions have been synthesized. Through the application of a range of modern research methods, an analysis of the composition, optical, photoelectric, nonlinear optical spectra, as...