Enhanced optical performance of thermochromic VO2 based on multilayer designs

Abstract

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 (Tlum) and solar transmittance (Tsol), solar spectrum modulation (ΔTsol) is however quite moderate. Employing a two-top-layer strategy further improves the optical performance of VO2, especially with an increase of ΔTsol 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 Tlum and ΔTsol 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 Tlum (<τc), 35.3% (from 0.362 to 0.490) for Tlum (>τc), and 71.7% (from 0.060 to 0.103) for ΔTsol.