Conductivity relaxation of poly(3-alkylthiophene)s

The conductivity relaxation of poly(3-alkylthiophene)s (P3ATs) is analyzed by use of electric modulus analysis together with non-exponential decay function to investigate intrinsic conduction mechanism of neutral P3ATs. A correlation with the thermal transitions from dynamic mechanical analysis and UV-Vis spectroscopy is attempted. It is found that conductivity relaxation behavior is highly related to the molecular motion. The side chain motion has no significant effect on the charge transport. While in the glass transition and rubbery region, relaxation time distribution becomes broadened with temperature. As the coplanar subchains in the ordered region melt, the conjugation length decreases and its distribution (and therefore relaxation time distribution) becomes narrower. The intrinsic conduction mechanism of neutral P3AT is determined by thermal activated hopping of charge carriers over energy barrier resulting from conformational defects such as soft or localized conformons.