Nanothermochromics with VO2-based core-shell structures: Calculated luminous and solar optical properties

Composites including VO2-based thermochromic nanoparticles are able to combine high luminous transmittance Tlum with a significant modulation of the solar energy transmittance ΔTsol at a “critical” temperature in the vicinity of room temperature. Thus nanothermochromics is of much interest for energy efficient fenestration and offers advantages over thermochromic VO2-based thin films. This paper presents calculations based on effective medium theory applied to dilute suspensions of core-shell nanoparticles and demonstrates that, in particular, moderately thin-walled hollow spherical VO2 nanoshells can give significantly higher values of ΔTsol than solid nanoparticles at the expense of a somewhat lowered Tlum. This paper is a sequel to a recent publication [S.-Y. Li, G. A. Niklasson, and C. G. Granqvist, J. Appl. Phys. 108, 063525 (2010)].