Growth of a high-performance WO3 nanofilm directly on a polydopamine-modified ITO electrode for electrochromism and power storage applications

Constructing a nanostructured electrochromic film and enhancing the bonding strength between the electrochromic film and electrode would effectively improve the charge transport and stability of the electrochromic film. In the present study, nanoporous WO3 films, including WO3 films without polydopamine (W-x, x = 2, 3, and 4) and WO3 films with polydopamine (PW-x, x = 2, 3, and 4), were built using a low-temperature hydrothermal method. The PW-x films showed significantly improved electrochromic cycle stability compared to the W-x films because the bonding strength between the ITO glass electrode and the WO3 film was enhanced by polydopamine (PDA) film. Notably, the PW-2 film still retained 90.8% of its original optical contrast after 5000 cycles. In addition, both the W-2 and PW-2 films exhibited high optical contrast from visible to infrared regions owing to their 3D network nanoporous structure; their optical contrasts were 71.5% and 69.7% at 700 nm, respectively. Both the W-2 and PW-2 films also exhibited high coloration efficiency and areal capacitance; their coloration efficiencies were 80.4 and 72.5 cm(2)/C, and areal capacitances were 59.38 and 75.32 mF/cm(2), respectively. PW-2 film is promising for electrochromic energy-saving smart windows with power storage.