Abstract
As a typical thermochromic material, VO2 coatings can be applied to smart windows by modulating the transmission of near infrared (NIR) light via phase transition. However, the inherent undesirable luminous transmittance (Tlum) and solar modulation efficiency (ΔTsol) of pure VO2 impede its practical application. In order to solve this problem, the porous VO2 based composite film was prepared by magnetron sputtering and subsequent acid solution process with Zn2V2O7 particles used as a sacrificial template to create pores, which showed excellent Tlum (72.1%) and enhanced ΔTsol (10.7%) compared with pure VO2 film. It was demonstrated that the porous structure of the film caused by acid solution process could improve the Tlum obviously and the isolated VO2 nanoparticles presented strong localized surface plasmon resonance (LSPR) effects to enhance the ΔTsol. Therefore, this method will provide a facile way to prepare VO2 based films with excellent thermochromic performance and thus promote the application of the VO2 based films in smart windows.
Highlights
VO2 is an important thermochromic material with high potential for low-cost switching and energy saving devices which has been widely studied due to its reversible semiconductor to metal transition accompanied by a dramatic change in optical and electrical properties at near room temperature (~68 ◦C) [1]
Inspired by this analysis, differing from directly etching pure VO2 film, we introduce Zn2V2O7 as the etching template into the VO2 film since the Zn2V2O7 possess higher activity than VO2 in the reaction with acid, which greatly improves the targeting of acid solution process, making the porous structure preparation in the film more controllable and avoiding more VO2 is corroded to guarantee the desirable ∆Tsol
Only diffraction peaks of VO2 were observed in sample S2 and the relative intensity decreased, which indicated that Zn2V2O7 as the template were totally corroded
Summary
VO2 is an important thermochromic material with high potential for low-cost switching and energy saving devices which has been widely studied due to its reversible semiconductor to metal transition accompanied by a dramatic change in optical and electrical properties at near room temperature (~68 ◦C) [1] With this characteristic, VO2 was usually investigated for thermochromic smart windows to reduce building energy consumption in response to the dynamic environmental temperature since significant decrease in the NIR transmittance and negligible changes in the visible and UV transmittance upon phase transition were exhibited. VO2 based thermochromic window is faced with great challenges of reducing the phase transition temperature (Tc), improving durability, enhancing luminous transmittance (Tlum) and solar modulation efficiency (∆Tsol) simultaneously. It is of great importance to develop a facile method to prepare controllable porous structure of VO2 based film
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