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

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 3vol.% ethylene glycol was dropped onto a quartz substrate, and it was evaporated and annealed under square wave or sine wave electric field of 1.25kV/cm with a repetition rate up to 4kHz. The drying process was carried out at room temperature for 3h followed by annealing for crystallization at 130 degrees C for 30min under the electric field. The value of sigma increases gradually with increase of repetition frequency for the electric field. The highest sigma values of 1373S/cm and 1244S/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 .