Lithium insertion in TiO2 doped Nb2O5 electrochromic thin films

TiO2 doped Nb2O5 thin films of concentration 0.1–10 mol% were prepared by the Pechini method and their electrochemical and electrochromic properties were characterized by cyclic voltammetry, chronoamperometry, ‘in situ’ UV–Vis spectrophotometry and scanning electron microscopy. The films obtained have a thickness between 440 and 550 nm. The cyclic voltammograms showed an increase in the cathodic current densities for the doped films. The highest values of the insertion charge density were observed for films containing TiO2 between 0.05 and 0.5 mol%. The undoped Nb2O5 films showed a transmittance variation (ΔT at 620 nm) of 56.8% and a coloration efficiency (CE) of 14.9 cm2 C-−1. An increase in ΔT and CE was observed with the increase of the TiO2 concentration up to 1.0 mol%, which presented ΔT=84% and CE=26.9 cm2 C−1. Above this concentration, the ΔT and CE values decreased. These results are discussed considering the electronic and morphological properties of the samples.