The integrated investigations of the stationary characteristics of photoconductivity (the spectral distribution of photoconductivity (PC), luminous-ampere characteristics (LAC), temperature dependences of dark photoconductivity) and the thermostimulated current (TSC) for crystalline and glassy lead thiogermanate (PbGeS 3) were performed. It was determined, as a function of crystals growing rate, there are one or two impurity maxima except for the native one in photoconductivity spectra. For the glassy lead thiogermanate in the range of wave lengths of 0.4-1.0 μm in PC spectra was revealed the hysteresis at the change of direction wave lengths sweep of incident light, conditioned by the phenomenon of induced impurity conductivity. The activation of PC, caused by thermal emptying of attachment levels, was observed on the temperature dependences of photoconductivity.

Photovoltaic tracking sensor monitoring the position of the sun in the sky was developed on the basis of GeS:Sb layered crystals. The operating principle of this sensor is based on the phenomenon of photovoltaic effect in GeS:Sb crystals; the magnitude and sign of generated photo-emf depend on the position of the light probe relative to the ohmic contacts, deposited on (001) surface of the crystal.

Ab initio calculations of the band structure, total and partial densities of states and the spatial distribution of the electron charge density of crystalline Na2GeS3 are performed in the framework of density functional theory in the local density approximation for an exchange-correlation potential. According to the calculation results, sodium thiogermanate is a direct-gap crystal with the top of the valence band and the bottom of the conduction band at the Γ point of the Brillouin zone. The calculated band gap is Eg = 2.51 eV. The nature of the components of the electronic states in different subbands of the valence band is determined. The calculated total density of states in the valence band of the crystal is compared with the known experimental X-ray photoelectron spectrum of Na2GeS3 glass. Based on the maps of the electron density distribution, the nature of the chemical bonds and high mobility of Na + ions in Na2GeS3 crystal is analyzed.

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