Structural and electrochromic properties of molybdenum doped vanadium pentoxide thin films by sol-gel and hydrothermal synthesis

Molybdenum-doped vanadium pentoxide (Mo-doped V2O5) thin films with doping levels of 3-10 mol% were prepared by dip-coating technique from a stable Mo-doped V2O5 sol synthesized by sol-gel and hydrothermal reaction. The Mo-doped V2O5 films had a layered V2O5 matrix structure along c-axis orientation with Mo6+ as substitutes. Values of the inserted and extracted charge density of 21.4 and 21.3 mC.cm-2 and the transmittance variation (ΔT at 640 nm) between anodic (+ 1.0 V) and cathodic (- 1.0 V) colored states of 41% were observed for the films with 5 mol% Mo6+ doping. Above this dopant concentration, the charge capacity and ΔT decreased. The enhancement of the electrochemical and electrochromic properties of the films is related to changes in the electronic properties of V2O5 films due to the creation of energy levels in the band gap of V2O5 by the Mo doping, accompanied by the reduction of the forbidden-band width and the increase of the conductivity