The effect of ethylene glycol post-treatment on the electrical conductivity of PEDOT: PSS thin films

Abstract

The application of organic conducting polymers such as poly (3,4-ethylene dioxythiophene): poly (4-styrene sulfonate) (PEDOT: PSS) is vastly expanding for the development of advanced and flexible organic electronic devices, such as solar cells, light-emitting diodes, and organic electrochemical transistors (OECTs). Also, PEDOT: PSS can perfectly replace high-cost Indium tin oxide (ITO) thin films. In this study, PEDOT: PSS was synthesized via the chemical oxidative polymerization method. The film formation was carried out through a feasible drop-casting method onto a cleaned glass substrate. To further enhance the conductivity of pristine PEDOT: PSS, the PEDOT: PSS thin films were post-treated with different concentrations (3, 5, and 7% v/v) of ethylene glycol (EG). Based on the electrochemical impedance spectroscopy (EIS) analysis, it was revealed that the post-treated sample had a higher conductivity value compared to the untreated sample (2.48 × 10-4 S/cm), with the highest recorded conductivity value of 2.67 × 10-3 S/cm at 5% v/v of EG. This result corresponds to the previous study, which highlighted that the optimum concentration of EG is 5% v/v to achieve the optimum conductivity value for thin film application. Furthermore, the structural properties of the thin films were characterized using Fourier transform infrared (FTIR) spectroscopy to confirm the presence of PEDOT: PSS and EG in the samples.