Inorganic electrochromic materials based on tungsten oxide and nickel oxide nanostructures

Electrochromic devices,which dynamically change color under applied potentials,are widely studied for use in energyefficient smart windows.The operation of electrochromic materials and devices involves the gain or loss of electrons and simultaneous insertion/extraction of ions with opposite charges to balance the internal electric fields.The performance is therefore limited by kinetics of charge transport in the electrochromic materials as well as ion migration in the electrolyte,materials and at their interfaces.Nanostructured electrochromic materials have an extremely short charge transport distance facilitating charge transport in electrochromic devices and large specific surface area for interaction with electrolytes,and thus may provide fast charge and ions transport,high electrochemical activities and remarkable enhancement of electrochromic properties.The recent progress in application of nanostructures,including nanoparticles,1D and 2D nanostructures,in metal oxide electrochromic materials and devices is reviewed.A perspective on the development trends in electrochromic materials and devices is also proposed.