High-performance dual-band electrochromic materials based on Prussian white

Dual-band electrochromic has attracted much attention in the past decades due to the independent regulation ability in visible and near-infrared light. However, dual-band electrochromic materials usually consist of multi-component nanomaterials that require delicate design and complex preparation processes. Herein, single-component dual-band electrochromic material, Prussian white (Na2FeII[FeII(CN)6], FeHCF), is successfully synthesized through facile aqueous solution method under atmospheric pressure at different temperatures. FeHCF film synthesized at 110 °C is composed of well-defined nanocubes with high crystallinity and exhibits outstanding dual-band electrochromic performance. It has high optical modulation (73.5% at 756 nm and 65.1% at 1000 nm), fast switching speeds (tb/tc=9.7/4.1 s at 756 nm, 10.6/8.0 s at 1000 nm), and excellent cycling stability (80% optical modulation retention at 756 nm, 81.7% at 1000 nm after 5000 cycles). The electrochromic device based on FeHCF-110 is capable of operating in three different modes, including "bright & warm", "cool" and "dark & cold" mode, showing great potential as energy-efficient windows.