Study of the doping of PEDOT:PSS films and the reversibility in organic electrochemical transistors

In this work, the effect in the performance of organic electrochemical transistors (OECTs) due to the doping with a secondary dopant solvent of poly(3,4ethylenedioxythiophene): poly (styrene sulfonic acid) (PEDOT:PSS) films) has been studied. We found an improvement in the performance of the OECTs related to the increase of conductivity of the PEDOT:PSS film due to the doping with ethylene glycol (EG). We found that PEDOT:PSS films doped with EG showed higher conductivity due to the improvement of conducting paths between the PEDOT+ chains, which causes a higher transconductance and response of the OECTs. However, a higher concentration of EG is detrimental to the OECT performance due to the removal of PSS- chains caused by the EG secondary doping, which was corroborated by X-ray diffraction. We propose that the good reversibility between low-resistance state (ON) to high-resistance state (OFF), is caused by the injection/removal of cations in the polymeric film to maintain the electroneutrality. We found applying more negative gate voltage pulses in the transfer characteristics of the OECTs is necessary to reach the complete oxidation of the PEDOT:PSS film, as lower negative voltages only partially dedope the film.