Durable Electrochromic Devices Driven at 0.8 V by Complementary Chromic Combination of Metallo-Supramolecular Polymer and Prussian Blue Analogues for Smart Windows with Low-Energy Consumption

Abstract

Durable electrochromic devices (ECDs) driven at 0.8 V were successfully fabricated by the complementary chromic combination of Fe(II)-based metallo-supramolecular polymer (polyFe) and Prussian blue analogues (PBAs). PolyFe was synthesized by the 1:1 complexing of Fe(OAc)2 and bis(terpyridyl)benzene and served as a cathodically coloring material. Nickel hexacyanoferrate (NiHCF) was revealed to be the best anodically coloring material among three PBAs. The complementary electrochromic (EC) pair of polyFe and NiHCF enabled a dramatic decrease of the driving voltage down to 0.8 V in the ECD. We fabricated two ECDs with liquid or solid electrolytes (L-ECD and S-ECD, respectively) and compared their EC properties. S-ECD showed a color change from blue-purple (0 V) to light yellow (0.8 V) with a transmittance change (ΔT) of 45.1% at 580 nm; the response times were 0.52 s for coloring and 1.03 s for bleaching; the coloration efficiency reached a high value of 627.5 cm2/C. S-ECD showed better durability than L-ECD in the long term stability test up to 10 000 cycles. In addition, a drastic change in transmittance spectrum between 415 and 655 nm in S-ECD aligned with the highest solar irradiance in the visible region. When exposing the S-ECD to solar irradiation, it was calculated that a large solar irradiance (99.6 W/m2) can be attenuated at the colored state (0 V), and only a low power density (0.0243 W/m2) was required to keep at the bleached state (0.8 V).