Oligothiophenes incorporated in a polysilsesquioxane network: application to tunable transparent conductive films

Novel polysilsesquioxanes incorporating long oligothiophenes (octamer to dodecamer) have been synthesized. Cyclic voltammetry and absorption spectroscopy of the polymer films showed the negative shift of oxidation potentials and the red shift of absorption bands with increasing the length of oligothienylene unit. Electrical conductivities and mobilities of charge carriers were changed by the doping level and their maximum values also increased with the length of oligothienylene unit. Work functions of the polymer films could be tuned from 5.3 to 5.7 eV by increasing the doping level. The comparison with the monomer films suggested that the rigidity of the polymer network strongly affects mechanical, spectroscopic, electrochemical, and electrical properties of the polymer films.