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

Abstract In the present study, a novel gel electrolyte composition combining lithium iodide LiI in 1-butyl-3-methylimidazolium iodide (BMII) ionic liquid,triiodide I3-/I- redox mediator and biodegradable gelatin is proposed for electrochromic devices (ECDs). More precisely, ECDs are assembled using viologen anchored − nanostructured TiO2 (deposited on FTO glass substrate by doctor blading at low temperature) as electrochromic material, FTO as counter-electrode and the gel electrolyte as redox mediator in between. Fast switching times and high cycling stability, up to 20000 cycles, are recorded. The optical reflectance modulation at 550 nm between white and blue color reaches a contrast value ΔR of about 19% in less than 4 seconds after 100 cycles.