Low-temperature UV-processing of nanocrystalline nanoporous thin TiO2 films : an original route toward plastic electrochromic sytems

The direct UV irradiation of nanoparticulate TiO2 films deposited by the “doctor-blade” technique led to 1.1 μm thick nanoporous and nanocrystalline anatase layers on various kinds of substrates as evidenced by various characterization techniques (MET, SEM, XRD, TGA-MS, and N2 sorption measurements). These films demonstrated high electrochromic responses and coloration efficiencies in an ionic liquid containing a lithium salt, which is a stable and environmental friendly electrolyte. The coloration efficiency reached 38 cm2 C−1 for films on ITO/plastic, for a 0.65 absorption change at 710 nm, whereas the corresponding film on FTO/glass showed a 40 cm2 C−1 coloration efficiency for a 1.1 absorbance change at 710 nm. The high surface area, nanoporous texture, and nanoparticulate structure of these layers provide a large number of intercalation sites, and minimal diffusion path lengths are ensured by the high surface-to-volume ratio