Easy-to-make sulfonatoalkyl viologen/sodium carboxymethylcellulose hydrogel-based electrochromic devices with high coloration efficiency, fast response and excellent cycling stability

In this paper, 1,1′-bis (2-sulfonatoethyl) viologen (SEV) and 1,1′-bis (3-sulfonatopropyl) viologen (SPV) as chromophore were synthesized and used to fabricate hydrogel-based electrochromic devices. The electrochromic hydrogel, consisting of SEV (or SPV), water, sodium carboxymethylcellulose and 1,1′-ferrocenedimethanol, was employed to fabricate all-in-one electrochromic devices. The proposed SEV/SPV-based hydrogel electrochromic devices have satisfactory coloration efficiency up to 304 cm2/C, response times below 3 s and driving voltages below −0.8 V. Surprisingly, SEV-based hydrogel and SPV-based hydrogel electrochromic device showed high cycling stability, attenuating 2% after 10000 cycles and attenuating 1% after 8000 cycles, respectively. The easy-to-make process for device and outstanding electrochromic properties of the hydrogel containing SEV and SPV make it promising to achieve environmentally benign electrochromic devices for smart windows and so forth.