Thermochromic VO2 for Energy-Efficient Smart Windows

Rapid development of the thermochromic glazing technique promises next-generation architectural windows with energy-saving characteristics by intelligently regulating indoor solar irradiation via modulating windows' optical properties in response to the surrounding temperature. Vanadium dioxide (VO2) is a promising material for energy-saving smart windows due to its reversible metal-to-insulator transition near room temperature and accompanying large changes in its optical properties. This review provides a comprehensive overview of the application of VO2 to smart windows with particular emphasis on recent progress from the electronic, atomic, nano, and micron perspectives. The effects of intrinsic atomic defects, elemental doping, and lattice strain on VO2 nanocrystals are examined. Nano- and microscale morphology engineering approaches that aim to enhance the thermochromic performance and impart practical multi-functionalities are summarized. Finally, the challenges and future directions of VO2-based smart windows are elaborated to bridge the gap between the lab research and large-scale practical applications.