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.