Layer-by-layer assembled WO₃ and tungstophosphate nanocomposite with enhanced electrochromic properties

Construction of a nanocomposite WO₃ film has been considered to be an important way to enhance electrochromic performance of the material. Herein, we fabricated a nanocomposite film containing WO₃ nanoparticles, tungstophosphate clusters K₆P₂W₁₈O₆₂ (P₂W₁₈) and poly(ethylene imine) by the layer-by-layer method. The fabrication and morphology of composite materials were investigated by UV–Vis spectra and scanning electron microscopy. The electrochemical and electrochromic properties were also examined and compared with P₂W₁₈–WO₃ composite film as well as individual P₂W₁₈ and WO₃ thin film. The composite film supported a greater number of sites for Li⁺ ion intercalation and extraction due to its large active surface area. As a result, the composite film displays enhanced optical contrast (48.4 %) and coloration efficiency (46.1 cm² C⁻¹) by incorporation of P₂W₁₈ into the WO₃ film. The enhanced electrochromic performances can be attributed to the composite structure, which provides large active surface area for electrochemical reactions and electrochromic performances. These results demonstrate that enhanced electrochromic properties could be achieved using the WO₃ and P₂W₁₈ composite structure.