Electrochromism of sol–gel derived niobium oxide films

Abstract

Niobium oxide films are promising cathodic electrochromics that in many aspects can compete with the more frequently studied WO3 films. The films reported herein were prepared using the sol–gel route from a NbCl5 precursor. The electrochromic properties were pronounced for crystalline films heat-treated at 500°C and exhibited transmittance changes between coloured and bleached states of 60% in the ultraviolet (UV) and 80% in the visible (VIS) and near-infrared (NIR) regions. Improved bleaching and more reversible electrochromism of thick niobium oxide films (thickness (d)>250nm) were obtained by lithiation.Electrochromic (EC) devices were also prepared by assembling niobium oxide and lithiated niobium oxide films of different thicknesses with a hybrid inorganic/organic Li+ ionic conductor (organically modified electrolyte-ormolyte) and a molybdenum and antimony doped tin oxide (SnO2:Sb(7%):Mo(10%) counter electrode films. The EC devices exhibited adequate colouring/bleaching kinetics (<2min) and colouring/bleaching changes up to 40–50%.