WO3 thin films by sol-gel for electrochromic applications

Tungsten oxide (WO3) is one of the most promising materials for electrochromic devices. WO3 thin films have been prepared at low temperature by using a polyethylene glycol (PEG) assisted sol–gel method. The structure and the stoichiometry of films deposited by dip coating on glass substrates have been studied as a function of thermal annealing by XRD, FTIR and l-Raman. PEGcontaining samples show improved electrochromic efficiency due to the formation of sub-stoichiometric, nanocrystalline phases. The electrochromic performance of WO3 films gets worse for annealing temperatures higher than 300C due to massive Na absorption from the substrate