Enhancement of Thermoelectric Properties of PEDOT:PSS Films by Applying an Alternating Electric Field During Preparation

Abstract

Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) is one of the most hopeful thermoelectric materials for realizing energy harvesting systems because of its flexibility and relatively high dimensionless figure of merit ZT. PEDOT:PSS thin films were synthesized under a direct-current and alternating-current electric field, and evaluated for their electrical conductivity $\sigma$ and Seebeck coefficient S as a function of repetition frequency for field. PEDOT:PSS solution containing 3 vol.% ethylene glycol was dropped onto a quartz substrate, and it was evaporated and annealed under square wave or sine wave electric field of 1.25 kV/cm with a repetition rate up to 4 kHz. The drying process was carried out at room temperature for 3 h followed by annealing for crystallization at 130°C for 30 min under the electric field. The value of $\sigma$ increases gradually with increase of repetition frequency $\nu$ for the electric field. The highest $\sigma$ values of 1373 S/cm and 1244 S/cm were attained for square and sine wave application, respectively. On the other hand, the value of S was almost constant. This suggests that carrier density does not change and mobility increases with $\nu$.