Fig. 3: Role of morphology in the performance of thermochromic antennas.

a 3D model used in computational calculations (top) and SEM (bottom) of VO₂ nanostars. b Measured emissivity of a thermochromic composite based on VO₂ stars at hot and cold states. c Simulation of absorption cross-section contrast, and normalized scattering and absorption cross-sections of optimum VO₂ nanostars (dimensions shown at the top right corner). d Three different dipole antenna geometries with large SA:V, a core-shell and a spherical particle, with their optimized characteristic length (\({L}_{c}\)). e Absorption cross-section contrast for the 5 different geometries presented in (d). f Scattering and absorption cross-sections of the five geometries in the hot state at \(\lambda=10\,{{\rm{\mu }}}{{\rm{m}}}\). The values are normalized to the particle’s volume (\({V}_{p}\)). g Maximum \(\Delta \epsilon\) (averaged in the atmospheric window) of resulting composite films based on a transparent host. For details, see supplementary note 5 and Supplementary Fig. 15. The maximum \(\Delta \epsilon\) of a composite based on a PE host of 50 \({{\rm{\mu }}}{{\rm{m}}}\) and 100 \({{\rm{\mu }}}{{\rm{m}}}\) thickness are also shown, indicating the volume fraction for maximum contrast. The parameter \({\Lambda }_{{{\rm{abs}}},c}\) was computed with \({C}_{{{\rm{abs}}},{{\rm{c}}}}\) at \(\lambda=10\,{{\rm{\mu }}}{{\rm{m}}}\). For core-shell particles, the refractive index of the core is 1.5. The refractive index of PE and VO₂ is based on values reported elsewhere (Supplementary Fig. 9)^33,40. Source data are provided as a Source Data file.