Metallopolymers and non-stoichiometric nickel oxide: Towards neutral tint large-area electrochromic devices

Abstract Wet-chemical approaches were utilized to fabricate electrochromic (EC) thin films of different chemical nature, but compatible to each other in terms of coloration and electrochemical properties. A metallo-supramolecular polyelectrolyte (Fe-MEPE) thin film is shown to exhibit a large visible light transmittance change (Δτ v ) of 54% when switched from deep blue-violet (Fe 2+ ) to colorless (Fe 3+ ). On the other hand, a soft sol-gel peroxo-based approach was pursued to fabricate non-stoichiometric nickel oxide (Ni 1-x O) thin films on transparent conductive glass at low process temperature. Ni 1-x O, due to the Ni 2+ /Ni 3+ redox couple, shows an EC response with a Δτ v of 44% when switched from a colorless state (Ni 2+ ) to a grey-brown mixed-valence state (Ni 2+ /Ni 3+ ). Proof-of-concept is provided for a glass-based EC device combining Fe-MEPE and Ni 1-x O electrodes. The excellent EC performance is manifested in a Δτ v of 28% for the full cell and a low haze of via spin-coating, dip-coating, or slot-die deposition. The viability of this approach for later industrial production is demonstrated by the example of roll-to-roll (R2R) processing on transparent conductive films (TCF).