Facile fabrication of VO2 composite film with enhanced significantly solar modulation performance by adjusting viscosity of VO2/PU dispersion

The facile fabrication of VO 2 thermochromic film with outstanding solar modulation ability along with high luminous transmittance is still challenging for the large-scale practical application of VO 2 films. The dispersity of VO 2 in polymer matrix can determine the optical performance of VO 2 thermochromic film to some content. Herein, the VO 2 nanoparticles were prepared by one-step hydrothermal method and directly dispersed in polyurethane (PU) sol with different viscosity to cast the VO 2 composite film . The solar modulation ability (ΔT sol ) almost increased linearly with the logarithm of viscosity for PU sol, and ΔT sol can be enhanced to 14.5% from 6.6% while maintaining a high T lum beyond 54% only by changing the content of thickener. The ΔT sol increased further to 20.0% for the three layers film. The enhanced optical performances might be attributed to the good dispersity of VO 2 nanoparticles and pore structure in PU matrix. This study provides a novel strategy in preparing VO 2 film for the applications in smart windows.