Low temperature analysis of the electrical conduction with the NSPT mechanism in p -CuIn 3 Se 5

Abstract The AC electrical conductivity σ a c ( ω , T ) in polycrystalline semiconductor p -CuIn 3 Se 5 has been studied by means of impedance spectroscopy measurements, in the temperature and frequency ranges between 173 and 253 K and 600 KHz-1MHz, respectively. The frequency and temperature dependence of the power law exponent s and σ a c are interpreted by the Non-overlapping Small-Polaron Tunneling (NSPT) model. Some important parameters such as the polaron hopping energy W h , the hopping tunneling distance R ω and the density of states at the Fermi level N (E F ) are estimated and their temperature and frequency dependence discussed. Experimental data of the real (Z′) and imaginary (Z″) impedance of the complex impedance Z ∗ obtained from Nyquist diagrams shows the contribution of the grain and the grain boundary. This allows to choose an appropriate equivalent circuit for this material in the considered temperature and frequency ranges.