Overlapping large polaron tunneling conduction process in the ordered defect coumpound p-CuIn3Se5

The AC electrical conductivity σ ac (ω, T) in polycrystalline ordered defect semiconductor compound p-CuIn3Se5 is studied, for the first time, in the low temperature range 120–180 K with alternating current in the frequency range from 600 kHz to 1 MHz. The conduction mechanism is explained by the process that can be ascribed to the tunneling transport mechanism such as the Overlapping Large Polaron Tunneling (OLPT). The analysis of the frequency exponent of AC conductivity s(T), obtained from the study of the AC electrical conductivity through allows us to show agreement with the theoretical model of OLPT. Some important parameters such as the hopping tunneling distance R ω and the density of states at the Fermi level N(EF) are estimated and their temperature and frequency dependence discussed. An equivalent circuit model is proposed to fit impedance plots and the activation energies for the relaxation process are estimated. The relaxation time for the grain boundary contribution is studied by analyzing the behavior of impedance versus frequency at different temperatures. The deduced relaxation time is found to decrease with increasing temperature and obey the Arrhenius relationship.