Optical‐Cavity‐Incorporated Colorful All‐Solid‐State Electrochromic Devices for Dual Anti‐Counterfeiting

Abstract The fusion of electrochromic technology with optical resonant cavities presents an intriguing innovation in the electrochromic field. However, this fusion is mainly achieved in liquid electrolyte‐based or sol–gel electrolyte‐based electrochromic devices, but not in all‐solid‐state electrochromic devices, which have broader industrial applications. Here, a new all‐solid‐state electrochromic device is demonstrated with a metal–dielectric–metal (MDM) resonant cavity, which can achieve strong thin‐film interference effects through resonance, enabling the device to achieve unique structural colors that have rarely appeared in reported all‐solid‐state electrochromic devices, such as yellow green, purple, and light red. The color gamut of the device can be further expanded due to the adjustable optical constants of the electrochromic layer. What is more, this device exhibits remarkable cycling stability (maintaining 84% modulation capability after 7200 cycles), rapid switching time (coloration in 2.6 s and bleaching in 2.8 s), and excellent optical memory effect (only increasing by 13.8% after almost 36 000 s). In addition, this exquisite structural design has dual‐responsive anti‐counterfeiting effects based on voltage and angle, further demonstrating the powerful color modulation capability of this device.