On the charge transport mechanism of cross-linked PEDOT:PSS films

Conductive composites based on cross-linked poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) blends have been widely applied to produce electronic devices, such as organic electrochemical transistor, biosensors and electrochromic devices, to name a few. Notwithstanding, fundamental details regarding the influence of the cross-link agent on the charge transport mechanism of PEDOT:PSS based composites is still not completely understood. Herein, we present a study regarding the influence of the cross-link (3-glycidyloxypropyl) trimethoxysilane (GPTMS) on the charge transport mechanism of PEDOT:PSS/GPTMS composites. We have verified that the charge transport is dominated by hopping into percolated PEDOT:PSS-rich clusters for composites with a PEDOT:PSS content above 40%-wt. Interestingly, by analyzing the conductivity data by the variable range hopping model we observed that the hopping temperature, electronic localization length and charge carriers mobility remains practically independent on the PEDOT:PSS concentration. As for non-percolated composites, (i.e. below 40%-wt PEDOT:PSS), however, the charge transport is dominated by charge carrier hopping between unconnected PEDOT:PSS clusters, in which the electrical conductivity and the hopping temperature are strongly influenced by the cross-link agent content, and characterized by shorter carrier localization lengths.