Progress and challenges in flexible electrochromic devices

Electrochromic (EC) technology has made tremendous progresses and demonstrated potential applications in various fields such as green building, smart displays, military camouflage, etc. In recent years, flexible electrochromic devices (FECDs) have attracted growing interests due to their promising applications in flexible electronics and smart wearable. In spite of fascinating flexibility, the construction of FECDs faces more challenges compared with their rigid analogues because of more complex configures and assemblies. Thus, a comprehensive review is presented here to provide guidance for developing high-performance FECDs. In this review, the core components of FECD and their flexible features are firstly introduced. Then, recent advances and progress in the construction of FECDs are summarized in detail based on the different EC materials. Some critical performances are presented and compared between different devices to indicate the development direction of both EC materials and flexible transparent electrodes of FECDs. Finally, some challenges encountered in the fabrication and operation of FECDs are discussed and corresponding solutions are proposed. It is anticipated that this review will provide new insights into developing high-performance flexible ECDs toward applications in smart wearable and flexible electronics.