On-off near-infrared absorbance based on thermal-responsive plasmonic coupling in vanadium dioxide arrays for thermochromic windows

Vanadium dioxide (VO2) emerges as an attractive plasmonic material due to its unique reversible thermal-responsive phase transition and the promising application in energy-saving smart windows. Here, by optimizing the geometry of VO2 nano-cylinder arrays, we demonstrate a significant performance enhancement for energy-efficient thermochromic windows. Such a performance enhancement relies on the on-off behavior of plasmonic resonance in the extremely high packing density of VO2 nano-cylinder arrays. Different from the typical plasmonic material, silver, VO2 nano-cylinders are characterized to have strong absorbance in near-infrared spectrum with significantly weaker plasmonic coupling to their neighbors, making them suitable to be arranged with a high packing density. The VO2 nano-cylinder arrays exhibit a 160% luminous transmittance increment, comparing to a flat film with the same solar modulation of ∼10%. The work provides a better understanding of the plasmonic behavior on phase-change VO2 and an efficient method to enhance smart window performance.