Structural, Optical and Electrochromic Properties of Sol–Gel V₂O₅Thin Films

Abstract

Vanadium pentoxide thin films are prepared by the sol-gel route by dissolving V 2 O 5 powder (99.5% purity) in H 2 O 2 solution. The solution is spin-coated on glass substrates for optical (UV-VIS-NIR) and XRD analysis, and on ITOcoated glass substrates for electrochromic measurements. The samples are then annealed at 150 C for 1 hour. The resulting films have a yellow-orange color, typical of polycrystalline V 2 O 5 . XRD measurements have shown that after annealing in air at 400 C the structure of the films has a c-axis preferred orientation, the (0 0 1)-type planes lying parallel to the substrate. SEM analysis revealed a smooth surface. The films' optical and physical constants (n, a, Eg, the thickness d and the mean thickness inhomogeneity s) are calculated using a simple and accurate method based on the transmission spectrum alone. The films' electrochromism is studied using cyclic voltammetry (CV) and chronoamperometry in propylene carbonate solution containing 1 mol=l LiClO 4 . The films show reversible multichromism (yellow-green-blue) upon Li þ ion insertion=extraction. The absorbance of films colored at three different potentials is measured in the UV-VIS-PIR wavelength range, and this study shows that the changes in the optical absorption are consistent with the film color changes. Finally, the optical and electrochromic properties of the films prepared by this method are compared with those of our sputtered films already studied and with other works.

Study of optical properties of highly oriented nanocrystalline V2O5·nH2O films doped with K ions

“…4a. The result for V 2 O 5 ÁnH 2 O sample is in good agreement with results that obtained in [17]. These results can be compared with those obtained for sputtered [18] and other works [19][20][21][22].…”

Electrochromic thin films of sodium intercalated vanadium(V) oxide xerogels: Chemical bath deposition and characterization

“…The presence of one redox pair has been attributed to the amorphous nature of the films [45]. According to Benmoussa et al [46] the appearance of two redox pairs reflects the crystalline nature of the films. The observation of three redox pairs in our films is consistent with data of Costa et al obtained at the same scanning speed for vanadium oxide gel prepared on flexible polyethylene terephthalate/ indium tin oxide electrodes [2].…”

“…The survey from the literature shows that the cyclic voltammograms of vanadium(V) oxide xerogels display one [45], two [46] and three redox pairs [2]. The presence of one redox pair has been attributed to the amorphous nature of the films [45].…”

Characterization of V2O5 nanorods grown by spray pyrolysis technique

“…Therefore, it is very important to choose the appropriate deposition parameters to prepare the vanadium oxide thin films for a certain application [9]. V 2 O 5 thin films have been prepared by different techniques including pulsed laser deposition [10], sol-gel [11,12], vacuum evaporation [13], magnetron sputtering [14], electron-beam evaporation [15], and spray pyrolysis [16]. Among the various deposition techniques for the preparation of vanadium oxide thin films, chemical spray pyrolysis technique is a relatively simple and inexpensive technique for large-area coatings.…”