Poly­(3,4-ethylenedioxythiophene) (PEDOT) is certainly the most known and most used conductive polymer because it is commercially available and shows great potential for organic electronic, photovoltaic, and thermoelectric applications. Studies dedicated to PEDOT films have led to high conductivity enhancements. However, an exhaustive understanding of the mechanisms governing such enhancement is still lacking, hindered by the semicrystalline nature of the material itself. In this article, we report the development of highly conductive PEDOT films by controlling the crystallization of the PEDOT chains and by a subsequent dopant engineering approach using iron­(III) trifluoromethanesulfonate as oxidant, N-methyl pyrrolidone as polymerization rate controller and sulfuric acid as dopant. XRD, HRTEM, Synchrotron GIWAXS analyses and conductivity measurements down to 3 K allowed us to unravel the organization, doping, and transport mechanism of these highly conductive PEDOT materials. N-methyl pyrrolidone promotes bigger crystallites and structure enhancement during polymerization, whereas sulfuric acid treatment allows the replacement of triflate anions by hydrogenosulfate and increases the charge carrier concentration. We finally propose a charge transport model that fully corroborates our experimental observations. These polymers exhibit conductivities up to 5400 S cm–1 and thus show great promise for room temperature thermoelectric applications or ITO alternative for transparent electrodes.

The adsorption of water on several alkali halide surfaces was studied using scanning polarization force microscopy. Water adsorption leads to an overall increase of surface potential and ionic mobility. At a critical humidity that is characteristic of each salt (NaCl, KCl, KBr, and KI), important changes in the rate of increase of the surface potential and ionic mobility occurred. Topographical changes occurred as well, in the form of step motion. These were observed to occur at a fast rate above the critical point, while little step motion occurred at lower humidity. Dissolution of the crystal (deliquescence) is observed at high humidity. Below the critical humidity, contact potential images indicate that preferential solvation of cations occurs at steps producing a large enhancement of the step contrast in the images.