Thermoelectric power enhancement of PEDOT:PSS in high-humidity conditions

We report an increase in the thermoelectric power factor of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) from 23 +/- 5 to 225 +/- 130 mu W/(m.K-2) in high-humidity conditions. This enhancement was caused mainly by an increase in the apparent Seebeck coefficient, which could be related to morphological change after water absorption or electrochemical reaction of PEDOT in air. Our results demonstrate a positive effect of water in the PEDOT:PSS system and indicate the need for well-controlled measurement conditions, particularly humidity, in evaluating the performance of conducting organic materials. (C) 2014 The Japan Society of Applied Physics