High-throughput Roll-to-roll Fabrication of Flexible Thermochromic Coatings for Smart Windows with VO2 Nanoparticles

Abstract

VO2-based ‘nanothermochromics’ that utilizes the dispersion of VO2 nanoparticles in passive host matrix has been evaluated as a economic strategy of energy-saving “smart” windows to reduce energy consumption for heating and air conditioning in building. Here, we demonstrate a high-throughput roll-to-roll fabrication of thermochromic coatings for smart windows that can adapt their optical properties in accordance with external temperature. A large quantity (250 g) of VO2 nanoparticles (NPs) was synthesized at a time by controlled thermal treatment of bead-milled V2O5 NPs as a fast and inexpensive method. The amorphous nature of bead-milled V2O5 NPs combined with nanometer size kinetically facilitates uniform synthesis of high-quality VO2 NPs even under the less-reducing condition than that used to obtain bulk VO2. This mass production of VO2 NPs could be used to fabricate the largest VO2/PVP composites thermochromic coatings (12 cm × 600 cm) yet produced with excellent infrared modulation ability (~ 45%). This scalable and continuous production of large coating with thermochromic NPs will accelerate the commercialization of thermochromic coatings for smart windows, which will contribute to a large reduction in energy consumption to heat or cool buildings.