Soluble triarylamine functionalized symmetric viologen for all-solid-state electrochromic supercapacitors

Electrochromic supercapacitors have drawn enormous attention due to their ability to monitor the charge and discharge processes through color changes of electroactive materials. However, there are few work on small organic molecules as active materials for all-solid-state electrochromic supercapacitors. Herein, we reported two novel multifunctional symmetric viologens (TPA-bpy and CZ-bpy), which showed different solvatochromic, electrochromic, electroluminochromic and energy storage behaviors despite their similar chemical structures. The different performances between these two viologens were attributed to the difference in the intramolecular charge transfer capability and the solubility in organic solvents. Devices containing TPA-bpy displayed faster response time and higher coloration efficiency due to the introduction of packing-disruptive and three-dimensional triarylamine groups. Moreover, devices containing TPA-bpy also showed energy storage characteristics with an obvious color change from purple to yellow. It showed a wide voltage window (2.0 V), long discharge time (230.3 s at 0.01 mA cm−2), and excellent cycling stability with 90% capacitance retention after 6,000 cycles. The work provides a new and convenient strategy towards the development of novel electrochromic capacitive materials.