Effects of a proton scavenger on the thermoelectric performance of free-standing polythiophene and its derivative films

In this study, thermoelectric (TE) performance of free-standing polythiophene (PTh), poly(3-methylthiophene) (P3MeT), and poly(3-octylthiophene) (P3OT) films electrosynthesized in a freshly distilled boron trifluoride diethyl etherate (BFEE) solution containing 2,6-di-tert-butylpyridine (DTBP) as a proton scavenger, was systematically investigated. Free-standing PTh, P3MeT, and P3OT films obtained from the BFEE system displayed electrical conductivities of 46.1, 98.5, and 9.4 S cm−1, respectively. When DTBP was added, the electrical conductivities improved to 65.9, 147.3, and 15.9 S cm−1. The Seebeck coefficients of the films with improved electrical conductivities were 36.7, 13.7, and 24.9 μV K−1, respectively; these values were slightly lower than the original values of 42.5, 14.9, and 26.8 μV K−1 for the polymer films electrochemically synthesized in BFEE without DTBP. As a result, the power factor of polymer films increased from 8.33, 2.19, and 0.68 μW m−1 K−2 to 8.88, 2.76, and 0.99 μW m−1 K−2 with DTBP introduced, and the maximum figure of merit (ZT) maintained around 10−2 by estimate.