Multicolor electrochromic polyaniline–WO3 hybrid thin films: One-pot molecular assembling synthesis

Abstract

Nanostructured polyaniline (PANI)–WO₃ hybrid thin films were synthesized via a molecular assembling route in a solution of aniline using peroxotungstic acid (PTA) as the dopant and ammonium persulfate as the oxidant. The films show a porous morphology with nanorod arrays on the surface, and WO₃ is uniformly incorporated into the polymer network. Electrochemical and electrochromic tests including cyclic voltammetry, chronoamperometry and corresponding in situ transmittance of PANI–WO₃ hybrid films compared with neat PANI film and sol–gel WO₃ film were conducted in 0.5 M sulfuric acid solution. The hybrid films, being a dual electrochromic material, varied from royal purple to green, pale yellow and finally dark blue as the applied potential was scanned from 0.8 V to −0.5 V. Compared to sulfate doped PANI film, high colouration efficiency and comparable durability are obtained in the PANI–WO₃ hybrid films. The PANI–WO₃ hybrid films also show faster switching speed and better durability than WO₃ film. The enhanced electrochromic properties such as faster switching speed and better durability are mainly attributed to the combining of advantages of both materials and the formation of the donor–acceptor system.