Conductive PEDOT Covalently Bound to Transparent FTO Electrodes

A new 3,4-ethylenedioxythiophene (EDOT) monomer derivatized with aminopropyl-triethoxysilane (APTES-EDOT) was prepared via a simple two step reaction in high yield. The new monomer can be firmly grafted to the fluorine-tin-oxide (FTO) conductive glass, where the irreversible electro-oxidation of surface bound APTES-EDOT, in the presence of unsubstituted EDOT monomers in solution, triggers the cationic polymerization of EDOT, resulting in the incorporation of PEDOT chains into APTES-EDOT. As a result, the modified PEDOT film (Si-PEDOT) is covalently bound to the FTO surface and easily withstands mechanical stresses that are critical for the adhesion of regular PEDOT. When tested with Co(III)/(II) redox shuttles, electrodeposited Si-PEDOT films showed decreased charge transfer and mass transport resistances with respect to both platinum and conventional PEDOT films, leading to enhanced relative efficiencies (approximate to 10%) when employed as counter electrode in transparent dye sensitized solar cells.