High Performance and Enhanced Durability of Thermochromic Films Using VO₂@ZnO Core-Shell Nanoparticles

For VO₂-based thermochromic smart windows, high luminous transmittance (T_lum) and solar regulation efficiency (ΔT_sol) are usually pursued as the most critical issues, which have been discussed in numerous researches. However, environmental durability, which has rarely been considered, is also so vital for practical application because it determines lifetime and cycle times of smart windows. In this paper, we report novel VO₂@ZnO core-shell nanoparticles with ultrahigh durability as well as improved thermochromic performance. The VO₂@ZnO nanoparticles-based thermochromic film exhibits a robust durability that the ΔT_sol keeps 77% (from 19.1% to 14.7%) after 10³ hours in a hyperthermal and humid environment, while a relevant property of uncoated VO₂ nanoparticles-based film badly deteriorates after 30 h. Meanwhile, compared with the uncoated VO₂-based film, the VO₂@ZnO-based film demonstrates an 11.0% increase (from 17.2% to 19.1%) in ΔT_sol and a 31.1% increase (from 38.9% to 51.0%) in T_lum. Such integrated thermochromic performance expresses good potential for practical application of VO₂-based smart windows.