Preparation And Properties Of Electrochromic Film Based On Polyoxometalate Polyanions

Electrochromic film has attracted much attention due to the potential application in military disguise, smart windows, rear view mirror, high contrast display and the thermal control of satellites. Polyoxometalates (POM), a class of molecularly defined inorganic metal-oxide cluster usually represents reversible redox activity. POMs can be reduced or oxidized by applying voltage and most of them display blue color in the reduced state. Thus, there should be suitable method to fabricate POMs into conducting matrix for the further electrochromic devices. In recent years, the fabrication of layer by layer self-assembled ultra-thin film has attracted considerable interest in view of their importance to nanomaterials with tailored structures and properties. The layer-by-layer (LbL) self-assembly method, initially developed for pairs of oppositely charged polyelectrolytes, is a facile and versatile technique that has lately emerged as a viable approach to prepare large area ultra-thin films. Because the composition, thickness, and components of each layer in the film can be controlled, the LbL technique provides a route to fabricate various regular structures at the molecule level, which offers potential advantages for device application. Obviously, polyanions are suitable to the LbL method due to containing negative charge. Herein, to investigate new inorganic-organic electrochromic film based on polyoxometalate anions, the electrochromic films based on polyoxometalate were prepared by LbL self-assembly method and the electrochromic properties were explored in detail.