Supramolecular ionogels enable highly efficient electrochromism.

Abstract

Ionogels are a promising solution to improve the functionality of electrochromic devices (ECDs) by solving issues related to traditional liquid electrolytes, such as volatility, toxicity, and leakage. However, manufacturing ionogels is complicated as it often involves cross-linking polymerization or chemical sol-gel processes, requiring large amounts of inorganic or polymeric gelators. This results in low ionic conductivity and poor ECD performance. This study demonstrates the fabrication of highly conductive supramolecular ionogels by directly solidifying an ionic liquid (IL) using a low-molecular-weight gelator with a very low content (5 wt%). The resulting ionogel, DBS-G, exhibited self-healing properties, high optical transmittance (>86%), and high ionic conductivity (3.12 mS cm^-1) comparable to the pure IL. When combined with a conjugated thiophene-based electrochromic polymer or by incorporating electrochromic viologen derivatives and ferrocene into the ionogel, the constructed five-or three-layer ECDs demonstrate electrochromic performance comparable to IL electrolyte and surpassing polymer gelator-based ionogels. They exhibit high optical contrast, rapid response, high coloring efficiency, good cycle stability, and can operate effectively in a broad temperature range from -25 °C to 80 °C. Furthermore, the adhesive properties of DBS-G facilitate the fabrication of flexible ECDs, which exhibit commendable electrochromic performance and cycle stability under bending conditions.