High-performance electrochromic devices based poly[Ni(salen)]-type polymer films
journal contributionposted on 25.10.2016, 13:04 by Marta Nunes, Mariana Araujo, Joana Fonseca, Cosme Moura, Robert Hillman, Christina Freire
We report the application of two poly[Ni(salen)]-type electroactive polymer films as new electrochromic materials. The two films, poly[Ni(3-Mesalen)] (poly) and poly[Ni(3-MesaltMe)] (poly), were successfully electrodeposited onto ITO/PET flexible substrates, and their voltammetric characterization revealed that poly showed similar redox profiles in LiClO4/CH3CN and LiClO4/propylene carbonate (PC), while poly showed solvent-dependent electrochemical responses. Both films showed multielectrochromic behavior, exhibiting yellow, green, and russet colors according to their oxidation state, and promising electrochromic properties with high electrochemical stability in LiClO4/PC supporting electrolyte. In particular, poly exhibited a very good electrochemical stability, changing color between yellow and green (λ = 750 nm) during 9000 redox cycles, with a charge loss of 34.3%, an optical contrast of ΔT = 26.2%, and an optical density of ΔOD = 0.49, with a coloration efficiency of η = 75.55 cm2 C–1. On the other hand, poly showed good optical contrast for the color change from green to russet (ΔT = 58.5%), although with moderate electrochemical stability. Finally, poly was used to fabricate a solid-state electrochromic device using lateral configuration with two figures of merit: a simple shape (typology 1) and a butterfly shape (typology 2); typology 1 showed the best performance with optical contrast ΔT = 88.7% (at λ = 750 nm), coloration efficiency η = 130.4 cm2 C–1, and charge loss of 37.0% upon 3000 redox cycles.