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.