Stabilizing vanadyl acetylacetonate using imidazolium Ionic liquids for VO2 thermochromic thin films

This study examines the role of different imidazolium ionic liquids (ILs) on the stabilization of vanadyl acetylacetonate, VO (acac)(2), as a vanadium precursor by using UV-Vis spectroscopy. The possible stabilization mechanisms of VO (acac)(2) in IL solution were investigated. Furthermore, a fabrication method is proposed to prepare monoclinic vanadium oxide VO2 (M) thin films using a mixture of ionic liquid and poly-ionic liquid (PIL). The ILs 1-ethyl 3-allyl imidazolium bis(tri-fluoromethansulfonylimide) ([EAIM] [TFSI]), 1-ethyl 3-methyl imidazolium trifluoromethanesulfonate ([EMIM] [TFO]) and 1-ethyl 3-methyl imidazolium acetate ([EMIM] [AcO]) were investigated. It is shown that ([EAIM] [TFSI]) has the best coordinating ability to VO (acac) 2 for protecting the central vanadium atom from oxidation. For thermochromic film formation, the effect of annealing temperature (250 degrees C - 400 degrees C) and time (10 minutes - 120 minutes) on crystallization was studied using X-ray diffraction. The possible role of PIL decomposition on the formation and crystallization of VO2 (M) is discussed. The prepared films showed excellent thermochromic properties with 20.3 % solar modulation efficiency.

Automated summary

This study investigates the role of different imidazolium ionic liquids on stabilizing vanadyl acetylacetonate and proposes a method for preparing monoclinic vanadium oxide thin films. It is found that a specific imidazolium ionic liquid has the best coordinating ability to protect the central vanadium atom from oxidation. The prepared films exhibit excellent thermochromic properties with a solar modulation efficiency of 20.3%.