ELECTROCHROMISM OF SOL-GEL DERIVED NIOBIUM OXIDE-FILMS

Niobium oxide films are promising cathodic electrochromics that in man y aspects can compete with the more frequently studied WO, films. The films reported herein were prepared using the sol-gel route from a NbC l5 precursor. The electrochromic properties were pronounced for crysta lline films heat-treated at 500 degrees C and exhibited transmittance changes between coloured and bleached states of 60% in the ultraviolet (UV) sind 80% in the visible (VIS) and near-infrared (NIR) regions. I mproved bleaching and more reversible electrochromism of thick niobium oxide films (thickness (d) > 250 nm) were obtained by lithiation. Ele ctrochromic (EC) devices were also prepared by assembling niobium oxid e and lithiated niobium oxide films of different thicknesses with a hy brid inorganic/organic Li+ ionic conductor (organically modified elect rolyte-ormolyte) and a molybdenum and antimony doped tin oxide (SnO2:S b(7%): Mo(10%) counter electrode films. The EC devices exhibited adequ ate colouring/bleaching kinetics (< 2min) and colouring/bleaching chan ges up to 40-50%. (C) 1998 Elsevier Science B.V. All rights reserved.