Advanced VO₂/Polymer Nanocomposite Smart Window Films Using VO₂ Nanoparticles from High-Throughput Flow Synthesis

Problems associated with climate change require active implementation of energy-efficiency strategies minimizing carbon dioxide (CO₂) emissions and utilization of renewable energy sources. “Smart” window films utilizing thermochromic vanadium dioxide (VO₂) can adaptively make use of solar energy to significantly reduce the thermal load of the building by reflecting the infrared portion of the solar spectrum as a result of phase transition caused by heating of the monoclinic M-phase (M) of VO₂. In this work, a scalable flow synthesis process has been utilized to screen a broad range of parameter space to target the synthesis of controlled sizes and morphologies of monoclinic VO₂ (M) nanoparticles as well as using a doping strategy and surface modifications to enable the tuning of metal to insulator transition temperature in a high-throughput fashion. We have also explored the strategies to increase solar modulation properties of VO₂-nanoparticle-based polymer films by (i) changing the morphology of the nanoparticles from spherical into a nanorod structure, (ii) the surface modification of VO₂ nanoparticles by low refractive index ligands, and (iii) introduction of additional thermochromic materials to not only boost solar energy modulation but also enable more aesthetically appealing color of designed smart film. By strategically adjusting the VO₂ nanoparticle’s thermochromic and optical properties, we have achieved 10.0% solar energy modulation for the as-synthesized VO₂/polymer composite film and 19.9% solar energy modulation for NLETS [nickel(II) ligand exchange thermochromic system]/PFDA-VO₂ hybrid smart films. Moreover, using VO₂ nanoparticles with dominant nanorod morphology instead of nanospheres has resulted in more than double increase of thermochromic performance, ΔT at 2000 nm, and in the enhancement of solar energy modulation by 68% in combination ligands with low refractive index. This work provides insights into the design of advanced VO₂/polymer composite smart window films.