Thermochromic VO 2 Films for Energy-Efficient Windows

Abstract

VO2 films were produced by reactive e-beam evaporation followed by annealing post-treatment. Electrical measurements demonstrated a semiconductor-metal transition at Tc ~ 60°C. Spectrophotometry showed that the near-infrared solar transmittance was reduced when Tc was exceeded while the luminous transmittance remained relatively unchanged. This thermochromism may be utilized for regulating the energy throughput of windows. Practical application hinges on improved transmittance and on Tc-depression. These goals can be accomplished to some extent by dielectric overlayers, as verified by measurements on SiO2-coated VO2 films.