Multi-color electrochromic devices based on phenyl and heptyl viologens immobilized with UV-cured polymer electrolyte

Herein, an all-solid-state ECD is proposed to tackle the said aggregation issue of PV. An all-solid-state ECD, consisting of HV, PV, and solid polymer electrolyte, is studied by changing the operating potential window to achieve multi-color characteristics. The proposed ECD shows transparent, green, marine, and gray color at the open-circuit potential, 0.6 V, 0.8 V, and 1.0 V, respectively. The first set of redox peaks is due to the redox reaction of PV, and the second set of the redox peaks is the overlap of the first reduced state of HV and the second reduced state of PV. The combination of two viologens in a simple cell configuration (glass/ITO/multicolor-EC + solid electrolyte/ITO/glass) not only offers the characteristics of di-reduced PV species but also opens up a new avenue for color-tuning.