Sol-gel preparation and characterization of SiO ₂ coated VO ₂ films with enhanced transmittance and high thermochromic performance

Vanadium dioxide (VO ₂ ) films prepared at low-temperature with a low cost are considerable for energy-saving applications. Here, SiO ₂ coated VO ₂ films with clearly enhanced visible transmittance by introducing antireflection coatings (ARCs) and excellent thermochromic performance were present. The VO ₂ films have been prepared via a stable and low-cost sol-gel synthesis route using vanadium pentaoxide powder as precursor, and their structural, morphological, optical and electrical properties and thermochromic performance were systemically characterized. The resistance of VO ₂ films varies by 4 orders of magnitude and the transmittance changes from 11.8% to 69.3% at 2500 nm while no significant deviation appears in the visible region during metal-insulator transition (MIT). Nanoporous SiO ₂ coating with good optical transparency was coated on the surface of VO ₂ film via sol-gel dip-coating technique to enhance its optical transmittance, and the visible transmittance is increased by 14.6% due to the significantly decreased reflectance. The critical transition temperature (63 °C) and infrared switching properties of VO ₂ films are not much deteriorated by applying SiO ₂ layer. The synergistic effect of antireflection and thermochromism on SiO ₂ coated VO ₂ films was investigated.