Interfacial and space charge dielectric effects in Polypyrrole/ZnO composites

Abstract

Polypyrrole/zinc oxide composites were studied by Broadband Dielectric Spectroscopy in the frequency range 10 mHz–1 MHz for temperatures ranging from 15 K to room temperature. Lowering temperature, the dc conductivity was suppressed revealing underlying dielectric relaxation mechanisms. For 20, 30 and 40 wt.% ZnO composites, a relaxation was detected in the vicinity of range 104–10­5 Hz. Its typical mean relaxation time and its concentration dependence are compatible with Sillar's model for interfacial polarization in heterogeneous matter. At high ZnO concentrtion, a low-frequency relaxation also appeared around 0.01–10 Hz, stemming from space charge polarization. The shift of the relaxation upon temperature provides an insight to the dynamics of relaxing charge entities. Composites consisting of 10 wt.% ZnO are most suitable optoelectronic material, as they combine good electrical conduction, low capacitance effects and ohmic sample-electrode contacts.