Electrochromic devices using Fe(II)-based metallo-supramolecular polymer: Introduction of ionic liquid as electrolyte to enhance the thermal stability

Abstract

We fabricated electrochromic (EC) devices with Fe(II)-based metallo-supramolecular polymer (polyFe), 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (BMPyr(NTf)2) ionic liquid (IL), and Prussian blue (PB) as electrochromic layer, electrolyte layer, and counter layer, respectively. Thermal stability and ionic conductivity of BMPyr(NTf)2 IL was measured by thermogravimetric analysis (TGA) and impedance analysis to be 380°C and approximately 7.8 × 10−4 S/cm, respectively. The fabricated device showed reversible electrochromism between bluish-violet and colorless by applying +3.0/−1.5 V alternately. The 65% of the original EC contrast remained in the device after the repeated changes for 100 cycles at 100°C.