Structural, morphological and electrical properties of Cu2ZnSn1-xSixS4 (x = 0.8, x = 1) for solar-cells applications

• Equivalent circuits models are proposed for the materials.
• The AC conductivity is dominated by NSPT and CBH mechanisms.
• The electrical conductivities are dominated by band conduction and NNH.
• The conductivities are dominated by “VRH” mechanism.

The electrical properties of p-type semiconductor compounds derived from the family of Cu2Zn(Sn,Si)S4, namely materials with Si-content x = Si/(Sn + Si); (x = 0.8 and x = 1) have been prepared by solid–state reaction method. Structural characterizations of the materials were performed by powder X-ray diffraction and by Energy Dispersive X-ray spectroscopy (EDX) at room temperature. The materials were investigated by impedance spectroscopy technique measured in the 40 Hz–6 MHz frequency range from 100 to 300 K. Besides, the Cole–Cole (Z″ versus Z′) plots were well fitted to the equivalent circuits. Furthermore, the AC conductivity was investigated as a function of temperature and frequency in the same range.The different hopping models were used to investigate the characteristics of electrical conduction by hopping in employed temperature range. It was shown that two types of behavior can be expected, nearest-neighbour hopping for temperatures greaten then 220 K (region I) and the Mott variable-range hopping for temperatures lower then 220 K (region II).Characteristic parameters describing conductivity, such as the activation energy (ENNH), the critical concentration nC of the charge carriers and the acceptor concentration (NA), in region (I). Moreover, the characteristic temperature (T0), the density of states at the Fermi levels N(EF), localization length (ξ), hopping distance and average hopping energy, in region (II) were determined and their values were discussed. These results are critical for understanding the behavior of based on polycrystalline from the family of Cu2Zn(Sn,Si)S4 for absorber materials in solar-cells.