Doped State and Solubility Changes in PEDOT:PSS Thin Films by High-Energy Gamma-Ray Irradiation

Poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate) (PEDOT:PSS) thin films with various electrical-conductivity ranges are irradiated with gamma rays over a wide range of doses (1-50kGy). Spectroscopic analyses reveal that the high-energy irradiation results in changes in the doped state and chemical structure of the thin polymer films. Through the absorption measurement of the doped PEDOT:PSS films, the authors find that the films are relatively insensitive to irradiation and that the neutral state peaks in the de-doped PEDOT decrease relative to the doped state as the gamma-ray dose increases. The gamma-ray irradiation up to 50kGy results in a decrease in electrical conductivity in the already doped polymer films whereas it induces re-doping and electrical-conductivity enhancement in the chemically de-doped ones. The high-dose irradiation also induces chemical cross-linking, resulting in thin films that are robust against solvent dipping.