Nitrogen-doped carbon dots-modified Prussian blue with sandwich-like structure as a high-performance electrochromic material

Prussian blue (PB), as a promising inorganic electrochromic material (ECM), has been widely used in smart windows, displays, sensors, etc. However, there are still many challenges for PB to achieve high electrochromic performance. Herein, we synthesized nitrogen-doped carbon dots-modified PB film (defined as PB@N-CDs) with a sandwich-like structure by a simple stepwise electrodeposition method. The carbon dots show an obvious advantage in ultrafast electron transfer ability, which can reduce charge loss during the transfer process, improve the electrochemical activity on both sides of PB, and thus facilitate a rapid electrochromic response. Furthermore, the surface of nitrogen-doped carbon dots contains multiple organic functional groups, which widen the movement path of K⁺ ions under electrostatic adsorption. Impressively, the PB@N-CDs film exhibits a short bleaching/coloring time (0.5/0.9 s) and a superior optical modulation range (78.6%). Particularly, the coloring efficiency has been significantly improved to 137.71 cm²/C (at 700 nm). All of these results open up new avenues for developing high-performance PB-based ECMs and promoting their applications in corresponding electrochromic devices (ECDs) and smart windows.