Electrosynthesis and characterization of an electrochromic material containing biscarbazole–oxadiazole units and its application in an electrochromic device

• Donor–acceptor type monomer was synthesized.
• Electrochromic device were constructed.
• The polymer film exhibited multicolor electrochromism.
• The device has high contrast ratio, fast response time, excellent stability and color persistence.

Electroactive poly(2,5-Bis(9-methyl-9 H-carbazol-3-yl)-1,3,4-oxadiazole) (PolyBCO) film was synthesized to form a highly stable conducting polymer with excellent electrochromic properties. The polymer was characterized by cyclic voltammetry, UV–Vis-NIR spectroscopy and colorimetry. Spectroelectrochemistry analysis demonstrated that the polymer can undergo both p-type and n-type doping processes. The polymer has four accessible color states. Further kinetic studies demonstrated that the polymer revealed high contrast ratio (75%), fast response time (0.9 s), excellent stability and color persistence. A dual-polymer electrochromic device was constructed in sandwich configuration where PolyBCO was used as the anodically coloring material. The device switches between a transmissive light gray state and a blue-colored state with a fast response time and high stability.