Flexible electrochromic devices having remarkable color change from golden to green and their application in smart windows and electronic labels

Abstract

In this study, four viologen derivatives, namely, 1,1′-bis(4-(bis(4-bromophenyl)amino)phenyl)-[4,4′-bipyridine]dihexafluorophosphate (DBrPV), 1-benzyl-1′-(4-(bis(4-bromophenyl)amino)phenyl)-[4,4′-bipyridine]dihexafluorophosphate (Bn-BrPV), 1,1′-bis(4-(3,6-dibromo-9H-carbazol-9-yl)phenyl)-[4,4′-bipyridine]dihexafluorophosphate (DBrCV), and 1-benzyl-1′-(4-(3,6-dibromo-9H-carbazol-9-yl)phenyl)-[4,4′-bipyridine]dihexafluorophosphate (Bn-BrCV), were synthesized. Electrochromic devices (ECDs) were fabricated using the four viologen derivatives as active materials. The structures of the ECDs were ITO–PET (or ITO–glass)/electrochromic active material/ITO–PET (or ITO–glass). Both flexible and rigid ECDs exhibited reversible color changes under an applied voltage. In particular, the ECDs (flexible and rigid) based on Bn-BrCV can vary from golden to grass green. Furthermore, flexible ECDs can maintain excellent performance after 1000 bending cycles. In addition, electrochromic smart windows and electronic tags, which can display information dynamically, were assembled.