Five-state flexible dynamic windows

Abstract

Flexible electrochromic (EC) devices are highly desirable in smart applications. Although flexible devices with up to three states have been demonstrated in previous work, the goal of EC device with characteristics of the multistate property, flexible compatibility, fast switching speed is still hard to achieve. In this work, we successfully developed a five-state flexible dynamic window (FFDW) based on Bi and Cu bimetal reversibly deposited system. This device possesses transparent state, gray state, black state, cupreous mirror state and silvery mirror state via a precise voltage control strategy. More excitingly, the phenomenon of two mirror states obtained in one device is firstly reported. This FFDW, which can be bended for more than 50 times, exhibits fast switching speed of 2.34 s for complete stripping and 11.12 s for tinting, with a more than 63% transmittance modulation range at black state and an over 60% reflectance modulation range at mirror state. Finally, we unveiled the mechanism accounting for the voltage-dependent rich optical states in details. Our findings are helpful for developing high-performance dynamic windows for application in smart homes, vehicles and wearable devices.