Green Electrochromic Film Formation via Phenylcarbazole Polymerization in Ionic Liquids

The scale-up of electrochromic devices (ECD) from laboratory research to mass production is still challenging due to the use of toxic organic solvents and electrolytes, as well as performance losses when transferred to solid substrates specially flexible ones. Here, we present a green approach for the electropolymerization of polycarbazoles on flexible substrates, using two distinct monomers: 4-(9H-carbazol-9-yl)phenol and 4-(3-methoxy-9H-carbazol-9-yl)phenol. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-TFSI) ionic liquid (IL) is used as a reusable electrolyte medium, which not only minimizes environmental impact but also enables efficient modulation of the electrochromic performance. The resulting electroactive films showed promising coverage (2.24·10^{- 9} and 2.5·10^{- 8} mol cm^{- 2}, respectively), and efficient electrochromic features (31 and 17 cm² C^-1, respectively), demonstrating their potential for improving sustainable fabrication protocols and paving the way toward practical, environmentally friendly ECD applications.