Sulfuric acid vapor treatment for enhancing the thermoelectric properties of PEDOT:PSS thin-films

We introduce a sulfuric acid vapor treatment method to enhance the thermoelectric (TE) performance of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) thin-films. The H2SO4 vapor treatment brought about the reduction of Coulomb interaction between PEDOT and PSS chains and structural rearrangement of PEDOT:PSS as expanded coil-like nanostructure. We studied the effects of the H2SO4 vapor treatment on the electrical conductivity and TE properties of PEDOT:PSS thin-films at various treatment temperatures. By the H2SO4 vapor treatment at 140 degrees C, both electrical conductivity and Seebeck coefficient of the PEDOT:PSS thin-film were improved from 1.1 to 1167 S/cm, and from 7.3 to 12.1 mu V/K, respectively. At this condition, the maximum power factor of 17.0 mu W/mK(2) was obtained, which is higher than that of the pristine PEDOT:PSS film (0.006 mu W/mK(2)) by the factor of 2833. Because the H2SO4 vapor treatment method introduced here has advantages in the large-area process and the film uniformity, we believe that the method can be applicable to various organic electronic devices using PEDOT:PSS as well as TE devices.