A complementary electrochromic system based on a Prussian blue thin film and a heptyl viologen solution

Electrochromic devices based on surface-confined Prussian blue or Ruthenium purple and aqueous solution-phase di-n-heptyl viologen

“…The deep blue/purple 'on' state is different in hue to the overall blue state reported by Lin et al [17] for similar PB/di-n-heptyl viologen ECDs. In this recent work [17], the electrolyte solvent was an equi-volume mixture of water and isopropanol, rather than pure water.…”

“…In this recent work [17], the electrolyte solvent was an equi-volume mixture of water and isopropanol, rather than pure water. As confirmed by spectra (with λ max = 605 nm) [17] of the reduced di-n-heptyl viologen, the monomeric radical cation form is dominant in the mixed solvent, thus providing colourless to blue as the cathodically-colouring electrochromic reaction.…”

“…In this recent work [17], the electrolyte solvent was an equi-volume mixture of water and isopropanol, rather than pure water. As confirmed by spectra (with λ max = 605 nm) [17] of the reduced di-n-heptyl viologen, the monomeric radical cation form is dominant in the mixed solvent, thus providing colourless to blue as the cathodically-colouring electrochromic reaction. In the present work, the CIELAB (L*a*b*) chromaticity coordinates ( Table 1), show that with a decrease in L*, a positive change (towards red) in a* occurs, coupled with a negative change (towards blue) in b*, quantifying the perceived coloured state as a combination of blue and purplish-red.…”

A WO3–poly(butyl viologen) layer-by-layer film/ruthenium purple film based electrochromic device switching by 1 volt application

“…A contrast ratio of 49% was observed for the device under fully colored state ( À 1.0 V), thus showing it to be suitable for EC applications [2,4]. Previously, for a complementary electrochromic system based on a Prussian blue thin film and a heptyl viologen solution, a maximum transmittance window of 59% was obtained [52]. For a star-shaped 4,4 0 -bipyridine derivative (1,3,5-tri(1-methyl-4,4 0 -bipyridinium bromide)-2,4,6-trimethyl benzene) based electrochromic device, a contrast ranging between 25% and 40% at 530 nm was achieved [51].…”

Eco-friendly redox mediator gelatin-electrolyte for simplified TiO2-viologen based electrochromic devices

“…Different strategies have been exploited in viologen devices, like the use of a liquid electrolyte for a faster ionic diffusion and improved electrolyte penetration into the EC layer [44,45] or the use of viologen itself in a liquid state (device simplification to 4 layers) [50], implying supplementary constraints for assembly and sealing, with negative effects on the device mechanical and cycling stability.…”