Conductivity enhancement of conjugated polymer after HCl–methanol treatment

Polymer conductivity is key factor to improve the performance of the electronic and photonic devices. Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) films were soaked into 0.03, 0.14, 0.41, and 1.13 M concentrations of HCl–methanol solution for 10, 20, 30, 40, 50, 60, and 70 min. The resulting films were investigated using Fourier transform infrared (FTIR) spectrometry, conductivity measurements, and field emission scanning electron microscopy. The characteristic FTIR absorption peaks of poly(4-styrenesulfonate) (PSS) of the films decreased as the soaking time increased. While PSS absorption peaks appeared in the HCl–methanol soaking solution and increased with the soaking time. The conductivity of PEDOT:PSS film was approximately 1.20 × 10 − 6 S/cm before soaking in the HCl–methanol solution. The conductivity of PEDOT:PSS was enhanced nearly three orders of magnitude after soaking the films into the HCl–methanol solvent. The surface of PEDOT:PSS film was initially very smooth. However, numerous humps appeared on the surface of the films after soaking PEDOT:PSS film into the HCl–methanol solution for 10, 20, and 30 min. The number of humps was reduced and disappeared thereafter.