Flexible and stretchable electrochromic displays: strategies, recent advances, and prospects

Flexible and stretchable electrochromic displays (ECDs) perform a crucial function in Internet of Things (IoT) systems, as they have shown superior eye-friendly, energy-saving, mechanical (flexibility and stretchability) properties. They can be integrated with IoT devices and successfully applied as wearable and intelligent electronics. Flexible and stretchable ECD technology has shown promising potential but is still in the early stage of development. A systematic overview from comprehensive perspectives of materials selection and modification, structure design, and advanced fabrication methods of this technology is necessary. In this review, we concentrate on the strategies in substrates, active layers, and electrolyte aspects to fabricate high-performance flexible and stretchable ECDs. We have systematically summarized the materials selection/modification and device structure design in these strategies. We also outline recent advances in flexible and stretchable ECDs based on processing methods for electrode patterns, active layer patterns, electrolyte patterns, and ECD pixels. Moreover, the interactive visual displays integrating ECD pixels with different sensors have been elaborated. Finally, we outline the future directions for developing flexible and stretchable ECDs, focusing on materials, methods, and applications. These prospects aim to overcome the limitations in pattern resolution, electrolyte uniformity, and pixel size/number and realize the manufacturable, commercialized, scalable, and robust flexible ECDs. This review can further promote the basic research and advanced fabrication of flexible ECDs and facilitate the advancement of multifunctional displays to satisfy the increasing demand for next-generation flexible electronics.