Oxetanes as polymerizable additives to PEDOT:PSS for water-resistant and transparent electrodes

Conductivity and structural resistance in water of thin films of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS):oxetane mixtures are improved remarkably (with the conductivity reaching 710 S/cm), when comparing with pristine PEDOT:PSS films. By investigating the effect of different substituents on the oxetanes, such as hydroxyl, hydroxylmethyl, methylchloride, and methyl groups, hydroxyl moieties were found to be crucial to the attained improvements. The conductivity enhancements are attributed to PEDOT segregation and its conformational changes, driven by screening effects between charged PEDOT and PSS chains. These effects are induced by either covalent cross-linking or hydrogen bonds established between negative PSS and hydroxyl groups in polyether chains, resultant from the polymerization of the oxetanes in the PEDOT:PSS medium. The films' applications as transparent electrodes resistant to aqueous media is shown by fabricating organic photovoltaic devices incorporating an oxetane:PEDOT:PSS film as the cathode and exhibiting similar performance to devices with indium tin oxide electrode.