Electron and Ion Transport in Mixed Electrochromic Thin Films of Perfluorinated Phthalocyanines

Thin films of a mixture of the perfluorinated phthalocyanines 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadeca-fluorophthalocyaninato copper(II) (F16PcCu) and 1,4,8,11,15,18,22,25-octakis-fluoro2,3,9,10,16,17,23,24-octakis-perfluoro-(isopropyl) phthalocyaninato copper(II) (F64PcCu) of different thicknesses and mixing ratios were prepared by simultaneous vapor deposition. A moderate extent of the intermolecular coupling between F16PcCu and F64PcCu within the mixed films comparable to that reported earlier for tetrakisperfluoroisopropyl-perfluoro phthalocyanine (F40PcCu) was revealed by UV/Vis spectroscopy. The electrochromic properties as well as the transport of electrons and counter cations in the 1:1 F-16 PcCu:F64PcCu mixed films were investigated by electrochemical and spectroelectrochemical characterization using an aqueous solution of KCl as electrolyte. The transport coefficients of electrons and ions of these films were comparable to those reported for F40PcCu films, for which a well-balanced, equally fast transport of both electrons and ions had been seen. Fast, reversible, and stable switching characteristics of the mixed films, upon reduction and intercalation of K+ counterions and re-oxidation with extraction of the counterions, were observed by cyclic voltammetry, chronoamperometry, and simultaneously measured optical absorption spectra. (C) 2021 Elsevier Ltd. All rights reserved.