VRH and NSPT conduction mechanisms in CuIn0.7Ga0.3Se2 near the liquid nitrogen temperature

Abstract Variable range hopping conduction process of Shklovskii-Efros type is identified, for the first time, in CuIn0.7Ga0.3Se2 bulk material in the temperature range [-190 °C, −10 °C]. Two different methods are considered to confirm this mechanism. The corresponding characteristic temperature and the localization length of mobile carriers are estimated. The AC electrical conductivity analysis suggests the predominance of Non-overlapping Small Polaron Tunneling mechanism. In the frequency range [20 Hz, 1 MHz], the equivalent circuit model of this material is established and the microscopic contributions to the total electrical conduction are discussed.