High-contrast electrochromic multilayer films of molybdenum-doped hexagonal tungsten bronze (Mo0.05–HTB)

Abstract

The creation of new materials for lightweight and high performance displays is an extremely active research field. Inorganic electrochromic ultra-thin film displays possess a keen advantage over other technologies because of their multiple color, fast switching, improved durability, high contrast, high coloration efficiency and low cost. Here we present the successful fabrication of multiple colored electrochromic multilayer films consisting of molybdenum-doped hexagonal tungsten bronze formulated as Na_0.2Mo_xW_1−xO₃·ZH₂O (x = 0.05) (Mo_0.05–HTB), using a layer-by-layer (LBL) assembly method. The resultant organic–inorganic films exhibit a linear increase in film thickness with assembly progressing. The color and electrochromic contrast of the films are adjustable by changing the mole ratio of Mo to W. Electrochromic contrast, coloration efficiency, switching speed, stability and optical memory for the as-prepared films were carefully investigated. The Mo–HTB/polyethyleneimine films undergo a color transition from colorless to light blue, and finally to dark blue over the potential range from −1.0 to 1.0 V vs Ag/AgCl reference electrode. These results exhibit the validation of an LBL-assembly based intermixing strategy for the design of multiple-hue electrochromic films.