Three‐Dimensional Ordered Macroporous Amorphous WO3 Arrays for Zinc‐Based Electrochromic Device with Large Light Modulation and Fast Switching

Abstract Electrochromic devices have important applications in building energy conservation, next‐generation displaying, and security encryption, while durable and high‐performance electrochromic materials are highly desirable. Herein, a Zn‐based electrochromic smart window by using 3D ordered macroporous amorphous WO 3 (a‐WO 3 ) arrays as cathode is reported. Benefiting from a 3D ordered macroporous structure with a high specific surface area that accelerates the ion diffusion and migration, and the oxygen vacancy modulated a‐WO 3 providing abundant zinc ion insertion channels, the as‐fabricated zinc‐based a‐WO 3 inverse opal (a‐WO 3 ‐IO) device exhibits excellent electrochromic properties, including large light modulation (83% optical contrast at 700 nm), fast response time (5.3 s for coloring and 3.2 s for bleaching), and robust cycling stability. Moreover, a solid‐state a‐WO 3 ‐IO prototype electrochromic smart window is demonstrated for light modulation, electronic display, and power supply. Furthermore, experimental results and theoretical calculations reveal that 3D macroporous amorphous WO 3 with rich oxygen vacancies can enhance the zinc ion absorption and diffusion, leading to the enhancement of electrochromic performance.