Effects of Organic Acids and a Fluoropolymer on the Conductivity and Transparency of Poly(3,4-ethylenedioxythiophene) Films

Using two organic acids with similar structures, we could fabricate poly (3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)-based conductive thin films with improved transparency and surface resistance. Sulfosuccinic acid showed better performance than p-toluenesulfonic acid with respect to the surface resistance and transparency, because sulfosuccinic acid has more acid group than that of p-toluenesulfonic acid, which shows efficient phase separation of PEDOT. This leads to the growth of PEDOT grains and decrease of the PSS shell. It was presumed that the PEDOT grain isolated from the pristine film swelled and grew, thereby improving the connectivity and facilitating the charge transfer. In addition, addition of a fluoropolymer enhanced the hydrophobicity of the surface of the film, thereby enhancing the durability of the film by increasing the water resistance and water permeability. When sulfosuccinic acid was added, the PEDOT:PSS film showed low surface resistance (106 Ω/sq) and high transparency (>89%). In addition, addition of the fluoropolymer resulted in a lower surface resistance (95 Ω/sq) and higher transparency (>89 %). The durability of the film was maintained for 3 days in the conventional case, but the durability was maintained up to 20 days on addition of the fluoropolymer. [Figure not available: see fulltext.].