A double network hydrogel electrolyte-based electrochromic device for enhanced electrochromic performance and lower power consumption

This study aims to investigate the electrochromic behavior of a Y-shaped, water-soluble monosubstituted viologen analog, BPYDB-C6H13, in different electrolyte systems. Two all-in-one gel-type ECDs (CMC-Na-ECD and CMC-Na-PAM-ECD) with CMC-Na hydrogel and CMC-Na-PAM double network hydrogel as the electrolytes and a solution-type ECD (DIW-ECD) were fabricated, and the electrochromic behaviors of BPYDB-C6H13 in different electrolytes were studied. Compared to DIW-ECD, the gel-state ECDs, especially CMC-Na-PAM-ECD with double network channel, showed enhanced cycling stability (retaining of the initial optical contrast after 12,000 s: 99.0% versus 95.5%), improved coloration efficiency (168.5 cm2/C versus 64.3 cm2/C), lower power consumption (0.55 mW/cm2 versus 2.11 mW/cm2), and longer memory time, because CMC-Na-PAM hydrogel had a larger pore size and a smoother transfer path than CMC-Na, thus reduced the path of charge transfer, and enhanced the ionic conductivity. The characteristics of easy-to-make, better electrochromic performance, and ultra-low power consumption make this gel-state ECD a promising candidate for applications in the fields of electronic paper, smart windows, displays, etc.