Electrochromic properties of MoO3 thin films derived by a sol–gel process

Molybdenum trioxide (MoO3) films were deposited on ITO/Glass substrates by the sol–gel method using a spin-coating technique and heat treated at various temperatures under different ambient atmosphere. Effects of the process parameters on the electrochromic properties of MoO3 films were studied using cyclic voltammetry (CV) in a propylene carbonate (PC) non-aqueous solution containing 1 M lithium perchlorate (LiClO4). Electrochromic MoO3 film on lithium intercalation was investigated by in-situ transmittance measurement during the CV process. The MoO3 films showed reversible recharge ability on Li+/e− intercalation/deintercalation. Experimental results revealed that the heat-treatment temperature, the ambient atmosphere, and the thickness will have the string influence on the electrochromic properties of MoO3 thin films. X-ray diffraction (XRD) results show that the amorphous MoO3 films can be obtained with the heat-treatment temperature below 300 °C in O2 ambient atmosphere. The optimum electrochromic MoO3 film, with a thickness of 130 nm, exhibits a maximum transmittance variation (ΔT%) of 30.9%, an optical density change (ΔOD) of 0.213, an intercalation charge (Q) of 8.47 mC/cm2, an insertion coefficient x in Li x MoO3 was 0.21 and a coloration efficiency (η) of 25.1 cm2/C between the colored and bleached states at a wavelength (λ) of 550 nm.