PEDOT-PSS based 2-in-1 step-by-step films: A refined study

The fine influence of several key parameters onto the recently reported 2-in-1 step-by-step construction of PEDOT-PSS nanofilms by spin-coating is investigated by laser ellipsometry, UV–vis–NIR spectrometry, tapping-mode AFM and 4-point probe conductimetry following Van der Pauw geometry. First, the thickness of the film increases when deposited under good ventilation. Then, the linearity of film thickness with respect to the PEDOT-PSS deposition step number is maintained by thermal treatment at 423 K during 30 min, showing that the 2-in-1 deposition method is compatible with the thermal annealing steps used in electronic devices containing PEDOT-PSS. Moreover, the concentration of the PEDOT-PSS suspension used for the deposition exerts major influence on the film buildup rate, with a minimum one needed for the method to process at reasonable pace. Finally, analogously to what is known for films obtained by a sole deposition step, the conductivity of 2-in-1 PEDOT-PSS nanofilms is shown to behave differently at ambient to high temperature (373 K) than at the lower temperatures where the conductivity studies are usually made. All these results will be precious for the construction of devices containing a PEDOT-PSS film with a thickness needing to be controlled reproducibly at the nanoscale.