Dielectric relaxation in semiconducting regioregular poly(3-hexylthiophene)

Regioregular effect transistor applications. While, the electrical mobility properties of P3HT have been examined$^{ }$the dielectric poly(3-hexylthiophene) (P3HT) is a material typically used as an organic semiconductor in thin film field- relaxation processes have not been systematically studied. We investigated the dielectric response of P3HT films in the temperature range of 240~K to 315~K and at frequencies up to 12 GHz. In the low frequency range P3HT shows a semi-conducting character and the overall dielectric response is dominated by dc-conductivity with $E_{a}$~=~17~kJ/mol. The apparent semi-conducting character cease at certain frequency above which, the material becomes a dielectric. At room temperature the semi-conducting to dielectric transition takes place at about 5 kHz. In the range of 10 kHz to 12 GHz the dielectric dispersion is insignificant and the dielectric constant is about 4. The dielectric relaxation process, with \textit{$\tau $} = 3*10$^{-5}$s and $E_{a}$~=~24~kJ/mol, can be attributed to local molecular motion of thiophene rings.