Ultrafast Ampipolar Switching in Electrochromic Copolymer Thin Films of Zinc(II) Tetrakis(4-aminophenyl)porphyrin -3,4-ethylenedioxythiophene

Abstract

Electrocopolymerization of different monomers is a useful approach for developing materials with tailored electrochromic properties and expanded color palettes. We report electrocopolymerization of two distinct monomers -zinc(II) tetrakis(4-aminophenyl)porphyrin (ZnTAPP) and 3,4ethylenedioxythiophene (EDOT) on an FTO-coated glass substrate. Our copolymer, poly (ZnTAPP-EDOT), exhibits a reversible color change from orange-brown to olive-green, with optical contrasts of 25% and 31%, and high coloration efficiencies of 434 and 181 cm²/C in the visible and near-IR regions, respectively. Poly (ZnTAPP-EDOT) retains 88% and 82% of its electrochromic performance after 200 redox cycles in the visible and near-IR regions, respectively, along with a fast switching response and strong optical memory under open-circuit conditions. Our time-dependent density functional theory (TDDFT) calculations reveal that the increasing EDOT units between ZnTAPP moieties promote a systematic redshift in absorption peaks and enhance oscillator strengths, attributed to extended πdelocalization facilitated by the added EDOT linkages, corroborating experimental UV-vis data. Our results suggest that electrocopolymerization of suitable porphyrins with selective monomers can produce electrochromic materials with tunable optical properties, high efficiency, and stability, making them well-suited for use in electrochromic devices.