Recently, a research group led by Prof. LI Guanghai from Institute of Solid State Physics, Hefei Institutes of Physical Science of Chinese Academy of Sciences, used a new method to develop thermochromic film with excellent luminous transmittance and solar modulation ability.

The research results were published in Materials Horizons.

VO₂(M) is a common thermochromic material capable of transitioning from a semiconductor to a metal state at a specific temperature (68°C). This transition affects the transparency of near-infrared light, making it useful for applications like energy-saving windows, optoelectronic switches, and temperature sensors. However, current methods for producing VO₂(M) face challenges such as high hydrothermal temperature requirements and the formation of large particles.

In this study, researchers developed a method to prepare high-quality VO₂(M) nanocrystals using a combination of hydrothermal and heat treatment processes.

Initially, they synthesized ultrafine VOOH nanoparticles under mild hydrothermal conditions. These nanoparticles were then heated to produce high-purity VO2(M) nanocrystals. The team also investigated how different heat treatment times affected the phase transition temperature and optical properties of VO₂ particles.

To enhance the environmental durability of VO₂, researchers encapsulated the nanocrystals in silica shells (VO₂@SiO₂). They explored how the thickness of these shells affected the optical properties of the material through theoretical simulations. The resulting VO₂@SiO₂/PVP thin films displayed impressive thermochromic abilitites. They can efficiently regulate solar heat, achieving a 14.91% increase in energy efficiency while maintain a high level of luminous transmittance at 62.29%.

"Our findings may inspire the development of more straightforward and efficient processes for producing high-performance VO₂-based films for various applications," said Dr. WU Liangfei, first author of the paper.