Grid patterned VO2 thermochromic coatings

Abstract

VO2 has garnered much attention in recent years as a promising candidate for thermochromic window applications due to rising awareness for energy conservation. Many different methods to synthesize affordable, cost-efficient, and high performance VO2 – based films have been developed over the past few years, including but not limited to sputtering, physical vapor deposition, chemical vapor deposition, etc. However, the tradeoff between improving luminous transmittance (Tlum) and solar modulation ability (ΔTsol) obstructs the commercialization of VO2-based smart windows. Previous studies of nanocomposite, nanoporous, biomimetic nanostructuring, anti-reflection coatings (ARC) and hybrid have been directed towards enhancing both Tlum and ΔTsol simultaneously. This work, for the first time, demonstrates a novelty approach that incorporates periodic grid structure of VO2 by using screen printing meshes. The effects of VO2 concentration, thickness, and mesh size on film’s performance were investigated, and the optimal combinations of the three factors were identified. Experimental results demonstrate that grid-patterning allows for formation of thicker coating with higher luminous transmittance and solar modulation performance (grid-pattern: Tlum = 67%, ΔTsol = 8.8%, continuous film: Tlum = 60%, ΔTsol = 6.9%). The best result obtained shows excellent solar modulation ability (14.9%) for a moderate transmittance level (43.3%), which is comparable to some of the best reported results.