ICT2014 Abstracts

Conducting polymers have excellent potential as thermoelectric materials for harvesting energy from waste heat at temperature below 423 K because of their low thermal conductivity and sufficiently-large electrical conductivity. For instance, it is well-known that an addition of a second solvent into an aqueous dispersion of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), such as ethylene glycol (EG), can dramatically improve its electrical conductivity. We have reported that the improvement of the electric properties of PEDOT:PSS films is due to the nanostructural ordering after the addition of EG [1]. PEDOT:PSS readily absorbs water vapor from the air. However, there are few studies on the relationship between water content and thermoelectric properties in the PEDOT:PSS system. Recently, we also reported an increase in the thermoelectric power factor of PEDOT:PSS with EG as a second solvent in high-humidity conditions [2]. This enhancement was caused mainly by an increase in the apparent Seebeck coefficient. We 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. In this presentation, we will discuss the effect of the humidity on the conduction mechanism in the PEDOT:PSS system. On the other hand, the design of the thermoelectric module using PEDOT:PSS is also crucial for low temperature use, and we will show the enhancement of the thermoelectric power output by the optimization of the module design.

[1] Q. Wei, M. Mukaida, Y. Naitoh, and T. Ishida, Adv. Mater., 25 (2013) 2831-2836.
[2] Q. Wei, M. Mukaida, K. Kirihara, Y. Naitoh, and T. Ishida, Appl. Phys. Express, 7 (2014) 031601.