INTERFACIAL POLARIZATION IN SEMICONDUCTING POLYPYRROLE THIN-FILMS

Semiconducting polypyrrole (PPY) thin films have been found to exhibit interesting dielectric properties when sandwiched between blocking electrodes. Dielectric relaxation studies have been carried out on metal-PPY-metal capacitors with and without an application of external bias. The relaxation spectra observed in the frequency range 1 kHz-1 MHz have been attributed to space charges and dipoles. The data have also been used to estimate the mobility of charge carriers inside PPY by application of simple space-charge theories. This phenomenon has been studied at several temperatures in the range 200-400 K. Interestingly, the mobility of charge carriers has been found to have a negative temperature coefficient, in agreement with theoretical calculations found in the literature for the mobility of charged polarons and kinks in conjugated polymers.