To improve the conversion efficiency of thermoelectric devices, new thermoelectric materials are being searched and studied. The use of materials such as metal chalcogenides in engineering for the creation of converters, thermoelements, and functional electronics elements is of interest. In this regard, it is topical to study the thermophysical properties and the effect of defects on the properties of these materials. The chalcogenides of the metals of the first group have a strong dependence of their properties on the intrinsic defectiveness of the structures. An increase in the degree of imperfection causes a decrease in the phase transition temperature, which is caused by a decrease in the forces of interatomic interaction. An increase in thermal conductivity with an increase in the chalcogen content is due to the prevailing increase in the electronic thermal conductivity over a decrease in the phonon component; the value of the lattice thermal conductivity is affected by the imperfection of the crystal lattice.