SOL-GEL Nb_2O_5 AND Nb_2O_5-TiO_2: NEW MATERIALS FOR ELECTROCHROMIC DEVICES

摘要

Thin films of niobium pentoxide (Nb_2O_5) and mixture of niobium pentoxide and titanium oxide deposited on ITO electronic conductor have been obtained by different sol-gel methods. After thermal treatment, the coatings are transparent and homogeneous without defects or cracks. The coatings consist of nanosized particles (<30-70nm) and show excellent electrochromic properties under Li~+ insertion. When crystallized the coatings turn deep blue with a large variation of the optical transmission from 80% (bleached state) to less than 20% (colored state) in the spectral range 400-1100nm. In pure niobia coatings the processes of Li~+ insertion or extraction (tested up to 2000 voltammetry cycles) are reversible and electrochemically stable. The electrochromic properties have been studied by electrochemical techniques such as cyclic voltammetry and optical spectroscopy in electrolyte of 0.1 M lithium perclorate (LiClO_4) dissolved in propylene carbonate (PC).