Transparent‐To‐Reflective Multicolor All‐Solid‐State Electrochromic Devices for Next‐Generation Intelligent Display Windows

Inorganic all-solid-state electrochromic devices have a wide range of industrial applications due to favorable chemical stability, high optical modulation rate, and good process compatibility. However, the monochromatic nature evidently restricts its development in transparent display, especially in application scenarios where color display is required. Here, an all-solid-state WO₃-based electrochromic device is presented with a dielectric-metal-dielectric (DMD) composite electrode, which features a transparent-to-reflective switching mode. More importantly, through the optimization of optical interference, the device exhibits rainbow structural colors. Leveraging the tunable optical constants of the electrochromic layer in conjunction with the additive color mixing principle, a remarkably wide color gamut of up to 11.58% can be attained with merely a minimal bias voltage of ±1.5 V, which substantially broadens the color gamut boundary of all-solid-state ECDs and represents a significant breakthrough in color-rendering capabilities. The device exhibits excellent electrochromic performance, remarkable cycling stability (at least 5600 cycles), low power consumption (3.8 mW cm^-2). Moreover, this device has two different performance modes, namely transmittance and reflection, and it holds great application potential in fields such as advertising, information transmission, and anti-counterfeiting.