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Electrochromic metallo-supramolecular polymers showing visible and near-infrared light transmittance modulation

: Schott, Marco; Niklaus, Lukas; Clade, Jürgen; Posset, Uwe


Solar energy materials and solar cells 200 (2019), Art. 110001, 8 pp.
ISSN: 0927-0248
Journal Article
Fraunhofer ISC ()
metallo-supramolecular polymers; electrochromism; electrochromic device; thin film coating; neutral tint; near-infrared absorption

Metallo-supramolecular polymers (Fe-MEPEs) based on Fe2+ ions and bis(terpyridine) ligands exhibit outstanding optical and electrochromic properties. The intensive coloration of Fe-MEPEs is caused by the metal-to-ligand charge transfer (MLCT) transition in the visible region. Thin films with high optical quality can be produced on transparent conducting glass or plastic substrates by common wet-coating techniques, e.g. dip-coating or roll-to-roll (R2R) processes. By applying a low voltage, the Fe-MEPE films can be reversibly switched between the reduced (dark) state (Fe2+) and the oxidized (bright) state (Fe3+). A further color change is visible at negative voltages resulting from a strong absorption in the near-infrared (NIR) region. Visible light transmittance changes (Δτv) > 60%, fast response times, and cycle stabilities over 10,000 switching cycles are demonstrated, which makes these electrochromic Fe-MEPEs very attractive to be used in electrochromic devices for a number of applications, e.g. in wearables, labels, architectural glazing, appliances, vehicles, and aircraft.