Electrochromic technology for flexible self-powered multifunctional systems from materials, devices to applications

Electrochromic (EC) technology has progressed rapidly from simple inorganic thin films to a broad library of organic molecules, conjugated polymers, and porous framework materials, thereby enabling higher coloration efficiency, wider spectral tunability, and improved mechanical flexibility. Contemporary flexible EC devices leverage hybrid material systems, engineered micro/nanostructures, and scalable manufacturing routes to realize faster switching and enhanced optical contrast. Nevertheless, the field continues to confront critical challenges including sluggish ion transport, complex system-level integration, and the difficulty of decoupling piezoelectric and triboelectric signals, which call for coordinated advances in materials design, device engineering, and intelligent control strategies. Against this backdrop, the present review first clarifies the importance of EC technology and elucidates the fundamental mechanisms of redox-driven optical modulation and ion insertion/extraction. It then systematically categorizes EC material systems, spanning inorganic transition-metal oxides, organic small molecules, conjugated polymers, and emerging hybrid platforms such as metal-supramolecular polymers, porous metal-organic frameworks (MOFs)/covalent organic frameworks (COFs), and flexible polymer-based electrolytes. Subsequently, the review examines the structural design and performance optimization of flexible EC devices, including multiscale optimization strategies and scalable fabrication techniques. Finally, it highlights advanced application scenarios from bioinspired electronic skin and smart textiles to self-powered EC energy-storage devices and smart batteries with self-diagnostic functionalities, which also concludes with a discussion of future research directions and outstanding challenges.