Facile fabrication of HfO2/nanocomposite vanadium oxide bilayer film with enhanced thermochromic properties and excellent durability

Abstract

Monoclinic vanadium dioxide (VO2(M)) can smartly regulate solar irradiation through its reversible semiconductor to metal transition, which has been widely investigated for the application in thermochromic smart windows. The poor durability, low solar modulation ability (ΔTsol), and luminous transmittance (Tlum) of high-purity VO2(M) film are the main obstacle for its commercial application. Nanocompositing can significantly improve the ΔTsol and Tlum, but the process is complex, expensive, and incompatible with large scale manufacturing procedures. We develop a facile way to fabricate HfO2/nanocomposite vanadium oxide bilayer films through room temperature magnetron sputtering and air environment rapid thermal annealing process. The nanocomposite vanadium oxide layer makes up of VO2, V2O5, and V3O7. The V2O5 and V3O7 components have a lower refractive index than VO2 function as antireflection. The HfO2 layer can act as a protective layer and antireflective layer at the same time. Meanwhile, the HfO2 can avoid contact with hazardous V2O5 from coming in touch with the environment. The bilayer structure presents Tlum of 51.6% and ΔTsol of 15.4%. The accelerated test suggested that the expected service life of this film is 21 years. This work provides a facile strategy to fabricate good thermochromic performance, excellent durability, and environment-friendly thermochromic smart windows.