Effective Way To Enhance the Electrode Performance of Multiwall Carbon Nanotube and Poly(3,4-ethylenedioxythiophene): Poly(styrene sulfonate) Composite Using HCl–Methanol Treatment

In this study, the electrode performance of composite films composed of highly conductive multiwalled carbon nanotubes (MWCNTs) and poly(3,4-ethylenedioxythiophene) polymerized with poly(4-styrenesulfonate) (PEDOT:PSS) are improved with the use of HCl–methanol (HCl–met) treatment. The HCl–met treatment affects film properties, including surface morphology, optical transmittance, work function (Φ), and electrical conductivity, which are investigated using various kinds of MWCNT/PEDOT:PSS composite systems. As a result of the HCl–met treatment, all MWCNT/PEDOT:PSS films undergo considerable changes in molecular ratio and arrangement between PEDOT and PSS, but their MWCNTs have no chemical/structural transitions. This in turn enhances the electrical conductivity and catalytic activity of the MWCNT/PEDOT:PSS films without changing their other properties. Furthermore, because of these effects, the HCl–met treatment brings about noticeable enhancements in performance as the source/drain electrode in an organic thin-film transistor and as the catalytic counter electrode in a dye-sensitized solar cell.