Electrochromic properties of undoped and lithium doped Nb2O5 films prepared by the sol-gel method

The electrochromic properties of lithium doped niobium pentoxide films prepared by the sol-gel route were analyzed. The electrochemical responses of the films exhibited a strong dependence on the lithium doping level. They were evaluated by monitoring the electrode mass change observed during cyclic voltammetry and chronoamperometry measurements, using the electrochemical quartz crystal microbalance. The electrochromic properties of the films, investigated by in situ spectroelectrochemical measurements, indicated that the bleaching process in the lithium doped films was complete whereas in the pure Nb2O5 films a residual coloration was observed, An increase in the lithium doping level improved the electrochemical and optical performances of the oxide film electrodes and a higher mass change was observed during the insertion/deinsertion measurements, so the maximum anodic charge that could be associated with a faster bleaching process was observed for films with the highest lithium doping level. (C) 2001 Elsevier Science Ltd. All rights reserved.