Enhanced optical performance of thermochromic VO2 based on multilayer designs

VO2 is a widely studied thermochromic material for smart windows. In this work, we comprehensively studied optical responses of VO2 -based multilayer structures. It is discovered that one-layer antireflection layer is capable of effectively enhancing both luminous transmittance (T lum ) and solar transmittance (T sol ), solar spectrum modulation (ΔT sol ) is however quite moderate. Employing a two-top-layer strategy further improves the optical performance of VO2 , especially with an increase of ΔT sol from 0.068 to 0.082. Remarkably, combining a layer with an index of 2.2 at the VO2 /glass interface continues to enhance the optical performance, leading to the highest T lum and ΔT sol among the investigated multilayer structures. Compared to the base structure of VO2 /glass, it contributes to a relative enhancement of 26.4% (from 0.435 to 0.550) for T lum ( ), 35.3% (from 0.362 to 0.490) for T lum (>τc ), and 71.7% (from 0.060 to 0.103) for ΔT sol .