A Highly Efficient and Energy Saving Electrochromic Platform for Adaptive Visible and Near-Infrared Light Modulation

Dual-band electrochromic devices (DBEDs) with reversible optical properties in visible (VIS) and near-infrared (NIR) spectral ranges are highly desirable for intelligent technologies (e.g. electrochromic smart windows, adaptive and military camouflages). However, most available DBEDs only have two optical states - namely the bleached and colored states, and efforts are committed to increasing the optical modulation between them, while durability of cycling is rarely reported. Herein, we report a novel multicolored rocking-chair DBED based on Prussian blue (PB) thin films as electrochromic layers and a conductive carbon cloth (CC) frame as the counter electrode. During the electrochromic process, cations from the electrolyte migrate back and forth between PB and CC, and electrolysis of aqueous electrolyte can be effectively avoided to extend device longevity. The PB-CC DBED exhibits superior dual-band electrochromic performance with a wide range of switchable colors, including transparent, blue, green and yellow, large optical modulation in VIS-NIR ranges, fast response speed, high coloration efficiency and long-term durability. Based on the diverse color change in the VIS range and thermal control in the NIR range, the camouflage ability of the device is also described. Finally, an adaptive optical modulation platform is demonstrated, obtained by connecting the PB-CC device to a voltage-controlled circuit module to realize intelligent and autonomous color switching of the device.