Oxygen and temperature effects on the electrochemical and electrochromic properties of rf-sputtered V₂O₅ thin films

Vanadium pentoxide (V₂O₅) thin films grown by rf-sputtering have been studied as a function of two growth parameters, O₂ content and substrate temperature, which influence importantly their structural, as well as their electrochemical and electrochromic properties. The increase in O₂ content appears to result in an increase of the grain size of the films, while the increase in substrate temperature leads in platelets perpendicular to the substrate, which enhance the porosity of the films. Films with low O₂ content (3%) and films grown at a substrate temperature of 300 °C, present enhanced charge storage properties of 553 mA h g⁻¹ and large transmittance modulation ability. On the contrary, high O₂ content (11%) and a substrate temperature of 150 °C lead to improved coloration efficiency (at λ = 400 nm), reaching values of 84.5 and ∼132 cm²C⁻¹, respectively. These findings are discussed in terms of structural and morphological changes occurring during the two parameters studied.