Doping mechanism in poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate):TiO2 nanoparticles composite films

• The doping mechanism for TiO2–doped PEDOT:PSS samples was investigated.
• TiO2 doping may lead to decreased carrier concentration of PEDOT:PSS.
• The domination of tunneling (hopping) at low (high) temperatures was observed.
• The enhanced mobility is attributed to the weak local electron–phonon coupling.

The doping mechanism for composite poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) films having TiO2 nanoparticles, denoted TiO2-doped PEDOT:PSS, is investigated in this study. It is shown that TiO2 doping may lead to decreased carrier concentration, owing to a combined effect of the high activation energy and changes in the chemical structure of PEDOT:PSS. The carrier mobility in PEDOT:PSS samples exhibits unexpectedly strong temperature dependence, implying the domination of tunneling (hopping) at low (high) temperatures. An exhibition of high mobility of TiO2-doped PEDOT:PSS samples is attributed to the weak local electron–phonon coupling.