An electrochromic composite film of Preyssler-type phosphotungstate decorated by AuNPs

• AuNPs were incorporated with phosphotungstate building an electrochromic composite film.
• Surface coverage and charge transfer rate of the film were increased due to presence of AuNPs.
• Color switching of the composite film was observed from transparent claret-red to deeper purple.
• The film showed enhanced optical contrast, coloration efficiency, and reduced coloring time.

A multilayer composite film containing Preyssler-type phosphotungstate K12.5Nal.5[NaP5W30O110]·l5H2O (P5W30) and Au particles (AuNPs) was fabricated by layer-by-layer assembly technology (LBL). The {[PEI/PSS–AuNPs/PEI/P5W30]n} composite film was characterized by scanning electronic microscopic (SEM), UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and cyclic voltammetry (CV) measurements. The electrochemical behavior of the films with and without AuNPs was investigated by cyclic voltammetry and electrochemical impedance spectra, and the composite film showed an enhanced electron transfer rate. The 6 bilayer AuNPs-free film performed color switching from transparent to blue, optical contrast of 10.4%, and an coloration efficiency of 6.99 cm2 C−1 at 600 nm. The 6 bilayer composite film displayed enhanced electrochromic performance with the color switching from claret-red to deeper purple, optical contrast of 27.3% and coloration efficiency of 18.52 cm2 C−1 at 550 nm due to the presence of AuNPs. The contribution of AuNPs gives valuable information for exploring new electrochromic materials.

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