Toward Triband Electrochromism: From Energy-Saving Strategies to Smart System Integration

The growing demand for energy-efficient and climate-adaptive technologies has intensified interest in materials capable of dynamically regulating both light and heat. Electrochromic devices (ECDs) enable on-demand control of optical properties with low power consumption. While visible–near-infrared (VIS–NIR) electrochromism effectively manages daylight and solar heat gain, extending modulation into the mid-infrared (MIR) region unlocks active radiative thermal control through reversible cooling and heating modes. Integrating VIS, NIR, and MIR regulation within a single platform─triband electrochromism─offers a holistic strategy for all-season energy regulation. This review surveys recent progress in triband electrochromic technologies, beginning with VIS–NIR modulation strategies for independent spectrum control, followed by MIR-modulating materials and device architectures for dynamic emissivity regulation. We further categorize integrated VIS–NIR–MIR systems into structural, voltage-driven, dual-unit, and codriven architectures, and discuss their operating mechanisms and application potential. Finally, emerging directions toward autonomous, self-powered, and scalable systems are highlighted.